HIV This Week

Kaul M, Lipton SA. Mechanisms of neuroimmunity and neurodegeneration associated with HIV-1 infection and AIDS. J Neuroimmune Pharmacol. 2006 Jun;1(2):138-51.

Infection with the human immunodeficiency virus-1 (HIV-1) the virus causing acquired immunodeficiency syndrome (AIDS), is a persistent health problem worldwide. HIV-1 seems to enter the brain very soon after peripheral infection and can induce severe and debilitating neurological problems that include behavioural abnormalities, motor dysfunction, and frank dementia. Infected peripheral immune-competent cells, in particular macrophages, appear to infiltrate the CNS and provoke a neuropathological response involving all cell types in the brain. The course of HIV-1 disease is strongly influenced by viral and host factors, such as the viral strain and the response of the host’s immune system. In addition, HIV-1-dependent disease processes in the periphery have a substantial effect on the pathological changes in the central nervous system (CNS), although the brain eventually harbours a distinctive viral population of its own. In the CNS, HIV-1 also incites activation of chemokine receptors, inflammatory mediators, extracellular matrix-degrading enzymes, and glutamate receptor-mediated excitotoxicity, all of which can initiate numerous downstream signalling pathways and disturb neuronal and glial function. Although there have been many major improvements in the control of viral infection in the periphery, an effective therapy for HIV-1-associated dementia (HAD) is still not available. This article addresses recently uncovered pathologic neuroimmune and degenerative mechanisms contributing to neuronal damage induced by HIV-1 and discusses experimental and potentially future therapeutic approaches.

Editors’ note: This review provides an overview of how HIV in the brain stimulates immune system reactions, including inflammatory cytokines that are highly toxic to cells of the central nervous system. Prior to combination antiretroviral treatment, the majority of patients with HIV associated dementia would deteriorate rapidly over several months. Now it appears that virological improvement of patients with dementia who are on antiretroviral treatment correlates with neurological improvement, leading to a more favourable prognosis. Differences in the abilities of specific antiretroviral drugs to penetrate the central nervous system may explain why some people with dementia and not others respond well.

Intranasal drug administration is a noninvasive method of bypassing the blood-brain barrier to deliver neurotrophins and other therapeutic agents to the brain and spinal cord. This method allows drugs that do not cross the blood-brain barrier to be delivered to the central nervous system (CNS) and eliminates the need for systemic delivery, thereby reducing unwanted systemic side effects. Delivery from the nose to the CNS occurs within minutes along both the olfactory and trigeminal neural pathways. Intranasal delivery occurs by an extracellular route and does not require that drugs bind to any receptor or undergo axonal transport. Intranasal delivery also targets the nasal associated lymphatic tissues and deep cervical lymph nodes. In addition, intranasally administered therapeutics are observed at high levels in the blood vessel walls and perivascular spaces of the cerebrovasculature. Using this intranasal method in animal models, researchers have successfully reduced stroke damage, reversed Alzheimer’s neurodegeneration, reduced anxiety, improved memory, stimulated cerebral neurogenesis, and treated brain tumors. In humans, intranasal insulin has been shown to improve memory in normal adults and patients with Alzheimer’s disease. Intranasal delivery strategies that can be employed to treat and prevent NeuroAIDS include: (1) target antiretrovirals to reach HIV that harbors in the CNS; (2) target therapeutics to protect neurons in the CNS; (3) modulate the neuroimmune function of monocyte/macrophages by targeting the lymphatics, perivascular spaces of the cerebrovasculature, and the CNS; and (4) improve memory and cognitive function by targeting therapeutics to the CNS.

Editors’ note: The blood – brain barrier serves to protect the brain and spinal cord from a variety of pathogens and toxic substances, but it is also a barrier to treatment of central nervous system disorders, including those caused by HIV infection. Intranasal drug delivery, which patients can do themselves, targets therapeutic agents directly to the brain, by-passing the blood-brain barrier and reducing systemic exposure. It can be used to treat neuroAIDS by targeting antiretroviral drugs, including neuroimmune modulators, to reach HIV that harbours in the central nervous system (CNS), to protect neurons in the CNS, and to improve memory and cognitive function. Intranasal insulin anyone?

Kiwanuka N, Laeyendecker O, Robb M, Kigozi G, Arroyo M, McCutchan F, Eller LA, Eller M, Makumbi F, Birx D, Wabwire-Mangen F, Serwadda D, Sewankambo NK, Quinn TC, Wawer M, Gray R. Effect of Human Immunodeficiency Virus Type 1 (HIV-1) Subtype on Disease Progression in Persons from Rakai, Uganda, with Incident HIV-1 Infection. J Infect Dis. 2008 Feb 11 [Epub ahead of print].

Human immunodeficiency virus type 1 (HIV-1) subtypes differ in biological characteristics that may affect pathogenicity. Kiwanuka and colleagues determined the HIV-1 subtype-specific rates of disease progression among 350 HIV-1 seroconverters. Subtype, viral load, and CD4(+) cell count were determined. Cox proportional hazards regression modelling was used to estimate adjusted hazard ratios (HRs) of progression to acquired immunodeficiency syndrome (AIDS) (defined as a CD4(+) cell count of </=250 cells/mm(3)) and to AIDS-associated death. A total of 59.1% of study subjects had subtype D strains, 15.1% had subtype A, 21.1% had intersubtype recombinant subtypes, 4.3% had multiple subtypes, and 0.3% had subtype C. Of the 350 subjects, 129 (37%) progressed to AIDS, and 68 (19.5%) died of AIDS. The median time to AIDS onset was shorter for persons with subtype D (6.5 years), recombinant subtypes (5.6 years), or multiple subtypes (5.8 years), compared with persons with subtype A (8.0 years). Relative to subtype A, adjusted hazard rations of progression to AIDS were 2.13 [95% confidence interval {CI}, 1.10-4.11] for subtype D, 2.16 [95% CI, 1.05-4.45] for recombinant subtypes, and 4.40 [95% CI, 1.71-11.3] for multiple subtypes. The risk of progression to death was significantly higher for subtype D (adjusted HR, 5.65; 95% CI, 1.37-23.4), recombinant subtypes (adjusted HR, 6.70; 95% CI, 1.56-28.8), and multiple subtypes (adjusted HR, 7.67; 95% CI, 1.27-46.3), compared with subtype A. HIV disease progression is affected by HIV-1 subtype. This finding may affect decisions on when to initiate antiretroviral therapy and may have implications for future trials of HIV-1 vaccines aimed at slowing disease progression.

Editors’ note: Subtype does matter ― subtype D has a higher frequency of syncytium formation and of the CXCR4 receptor use which is associated with more rapid decreases in CD4 cell count. Infection with multiple subtypes also was associated with faster disease progression compared to infection with a single subtype, emphasising the importance of positive prevention to avoid super-infection. Future therapeutic HIV vaccine trials should assess subtype specific responses; however, current treatment programmes, with subtype analysis remaining a research and surveillance tool, will have to continue to initiate antiretroviral treatment using standard thresholds for everyone, regardless of subtype.

Pereyra F, Addo MM, Kaufmann DE, Liu Y, Miura T, Rathod A, Baker B, Trocha A, Rosenberg R, Mackey E, Ueda P, Lu Z, Cohen D, Wrin T, Petropoulos CJ, Rosenberg ES, Walker BD. Genetic and Immunologic Heterogeneity among Persons Who Control HIV Infection in the Absence of Therapy. J Infect Dis. 2008 Feb 15;197(4):563-571.

Spontaneous control of human immunodeficiency virus (HIV) infection has been documented in a minority of HIV-infected individuals. The mechanisms behind this outcome remain largely unknown, and a better understanding of them will likely influence future vaccine strategies. HIV-specific T cell and antibody responses as well as host genetics were examined in untreated HIV-infected patients who maintain comparatively low plasma HIV RNA levels (hereafter, controllers), including those with levels of < 50 RNA copies/mL (elite controllers), those with levels of 50-2000  copies/mL (viremic controllers). Pereyra and colleagues also examined HIV-specific T cell and antibody responses as well as host genetics for patients with levels of >10,000 copies/mL (chronic progressors). CD8+ T cells from both controller groups preferentially target Gag over other proteins in the context of diverse HLA class I alleles, whereas responses are more broadly distributed in persons with progressive infection. Elite controllers represent a distinct group of individuals who have significantly more CD4 and CD8 T cells that secrete interferon-gamma and interleukin-2 and lower levels of HIV-neutralizing antibodies. Individual responses were quite heterogeneous, and none of the parameters evaluated was uniquely associated with the ability to control viremia. Elite controllers are a distinct group, even when compared to persons with low level viremia, but they exhibit marked genetic and immunologic heterogeneity. Even low-level viremia among HIV controllers was associated with measurable T cell dysfunction, which has implications for current prophylactic vaccine strategies.

Editors’ note: The CD8 T cells of elite controllers appear to have enhanced ability to inhibit virus replication in vitro. Elite controllers have the highest ratio of functional CD4 to CD8 T cells (chronic progressors have the lowest). Whether this association between T cell function and HIV is cause or effect is unclear. The lower neutralising antibody activity seen in elite controllers suggests that neutralising antibodies do not play a major role in maintaining viral suppression in people who spontaneously control viral replication.

Weiser B, Philpott S, Klimkait T, Burger H, Kitchen C, Burgisser P, Gorgievsk M, Perrin L, Piffaretti JC, Ledergerber B, the Swiss HIV Cohort Study. HIV-1 coreceptor usage and CXCR4-specific viral load predict clinical disease progression during combination antiretroviral therapy. AIDS 2008; 22(4):469-479.

Although combination antiretroviral therapy dramatically reduces rates of AIDS and death, a minority of patients experience clinical disease progression during treatment. Weiser and colleagues aimed to investigate whether detection of CXCR4(X4)-specific strains or quantification of X4-specific HIV-1 load predict clinical outcome. From the Swiss HIV Cohort Study, 96 participants who initiated combination antiretroviral therapy yet subsequently progressed to AIDS or death were compared with 84 contemporaneous, treated nonprogressors. A sensitive heteroduplex tracking assay was developed to quantify plasma X4 and CCR5 variants and resolve HIV-1 load into coreceptor-specific components. Measurements were analyzed as cofactors of progression in multivariable Cox models adjusted for concurrent CD4 cell count and total viral load, applying inverse probability weights to adjust for sampling bias. Patients with X4 variants at baseline displayed reduced CD4 cell responses compared with those without X4 strains (40 versus 82 cells/[mu]l; P = 0.012). The adjusted multivariable hazard ratio (HR) for clinical progression was 4.8 [95% confidence interval (CI) 2.3-10.0] for those demonstrating X4 strains at baseline. The X4-specific HIV-1 load was a similarly independent predictor, with HR values of 3.7 (95% CI, 1.2-11.3) and 5.9 (95% CI, 2.2-15.0) for baseline loads of 2.2-4.3 and > 4.3 log10 copies/ml, respectively, compared with < 2.2 log10 copies/ml. In conclusion, HIV-1 coreceptor usage and X4-specific viral loads strongly predicted disease progression during combination antiretroviral therapy, independent of and in addition to CD4 cell count or total viral load. Detection and quantification of X4 strains promise to be clinically useful biomarkers to guide patient management and study HIV-1 pathogenesis.

Editors’ note: HIV-1 requires two receptors to infect cells: CD4 is the primary receptor, with chemokine receptors CCR5 and CXCR4 serving as co-receptors. CCR5 using viruses (called R5 viruses) are those most commonly transmitted between people but after years of infection CXCR4-using strains (X4 viruses) are detected in half of people living with HIV and often predict CD4 cell depletion and accelerated disease progression. This study suggests that an assay detecting a high fraction of viruses using the X4 coreceptor early in the course of infection could be clinically useful; clinical trials are now needed to evaluate whether early treatment of asymptomatic people with CD4 counts above 350 cells/µl who harbor X4 strains can reduce HIV-1 levels and slow disease progression.

Vitezica, Zulma G; Milpied, Brigitte; Lonjou, Christine; Borot, Nicolas; Ledger, Terence Niel; Lefebvre, Anne; Hovnanian, Alain. HLA-DRB1*01 associated with cutaneous hypersensitivity induced by nevirapine and efavirenz. AIDS 2008;22(4):540-541.

HLA typing, demographic and immunological risk factors for nevirapine and efavirenz reactions were studied in a French cohort of HIV patients. Cases with isolated rash were significantly associated with HLA-DRB1*01 allele. No liver toxicity was observed and no association was detected with the percentage of CD4 T-cells. This study suggests that HLA-DRB1*01 allele plays an important role in susceptibility to cutaneous reactions associated with nevirapine and efavirenz in HIV patients.

Editors’ note: Being able to detect which patients are more likely to develop rashes with the first line non-nucleoside reverse transcriptase inhibitor (NNRTI) drugs nevirapine (NVP) and efavirenz (EFV) would be very useful clinically. Between 20-35% of patients on nevirapine and 32% of patients on efavirenz develop cutaneous hypersensitivity reactions within 6 weeks of treatment initiation and need to be switched to other drugs. This small study of 21 patients should be confirmed and, although its findings are promising, there is a way to go before genetic screening of human leukocyte antigen (HLA) markers to detect such susceptibility can be turned into a diagnostic test which would help decrease or eliminate this problem.

Boberg A, Isaguliants M Vaccination against drug resistance in HIV infection. Expert Rev Vaccines. 2008;7(1):131-45.

HIV-1 resistance to currently employed antiretroviral drugs and drug-associated adverse reactions and toxicity point to a need for additional measures to control HIV-1 replication in HIV-infected patients. The immune system of HIV-infected individuals mount an immune response against the regions harboring drug-resistance mutations, sometimes stronger than that against the parental wild-type sequences. A potent cross-reactive immune response against drug-resistant pol proteins can suppress the replication of drug-escaping HIV. This suggests the possibility for a vaccination against existing and anticipated drug-resistant HIV variants. If successful, therapeutic vaccines against drug resistance would ease the therapeutic modalities and limit the spread of drug-resistant HIV. A better understanding of the complex interactions between patterns of drug-resistance mutations, immune responses against these mutations and their antigen presentation by particular human lymphocyte antigen alleles could help to tailor these vaccines after new drugs/new mutations. In this review, we describe the developments in the field of immunization against mutations conferring drug resistance and evaluate their prospects for human vaccination.

Editors’ note: None of the therapeutic vaccine concepts and vaccination strategies tested thus far (subunit protein and DNA vaccines, live-vectored recombinant vaccines and various prime-boost vaccine combinations) have targeted drug-resistant HIV variants. Such a strategy would aim to induce immune pressure which would act synergistically with antiretroviral drugs. Ideally such a therapeutic vaccine would stimulate a strong cross-reactive immune response against both the wild-type and drug-escape HIV variants. Pie in the sky? Boberg and Isaguliants think this is feasible.

Bernard EJ, Azad Y, Vandamme AM, Weait M, Geretti AM. HIV forensics: pitfalls and acceptable standards in the use of phylogenetic analysis as evidence in criminal investigations of HIV transmission. HIV Med 2007;8:382-7.

Phylogenetic analysis - the study of the genetic relatedness between HIV strains - has recently been used in criminal prosecutions as evidence of responsibility for HIV transmission. In these trials, the expert opinion of virologists has been of critical importance. Pitfalls of phylogenetic analysis of HIV gene sequences relate to its complexity and its findings which do not achieve the levels of certainty obtained with the forensic analysis of human DNA. Although two individuals may carry HIV strains that are closely related, these will not necessarily be unique to the two parties and could extend to other persons within the same transmission network. For forensic purposes, phylogenetic analysis of acceptable standard should be conducted under strictly controlled conditions by laboratories with relevant expertise applying rigorous methods. It is vitally important to include the right controls, which should be epidemiologically and temporally relevant to the parties under investigation. Use of inappropriate controls can exaggerate any relatedness between the virus strains of the complainant and defendant as being strikingly unique. It will be often difficult to obtain the relevant controls. If convenient but less appropriate controls are used, interpretation of the findings should be tempered accordingly. Phylogenetic analysis cannot prove that HIV transmission occurred directly between two individuals. However, it can exonerate individuals by demonstrating that the defendant carries a virus strain unrelated to that of the complainant. Expert witnesses should acknowledge the limitations of the inferences that might be made and choose the correct language in both written and verbal testimony.

Editors’ note: In trying to determine in a court of law whether an HIV transmission has been intentional/purposeful transmission or reckless transmission or negligent transmission it is important first of all to establish whether transmission has occurred. Phylogenetic analysis can rule it out but is less likely to be able to rule it in with any certainty.

Brass AL, Dykxhoorn DM, Benita Y, Yan N, Engelman A, Xavier RJ, Lieberman J, Elledge SJ. Identification of Host Proteins Required for HIV Infection Through a Functional Genomic Screen. Science. 2008 Jan 10 [Epub ahead of print]

Photo credit: Boehringer-Ingelheim

HIV-1 exploits multiple host proteins during infection. Brass and colleagues performed a large-scale small interfering RNA (siRNA) screen to identify host factors required by HIV-1 and identified over 250 HIV-dependency factors (HDFs). These proteins participate in  a broad array of cellular functions and implicate new pathways in the viral life  cycle. Further analysis revealed previously unknown roles for retrograde Golgi transport proteins (Rab6 and Vps53) in viral entry, a karyopherin (TNPO3) in viral integration, and the Mediator complex (Med28) in viral transcription. Transcriptional analysis revealed that HDF genes were enriched for high expression in immune cells suggesting that viruses evolve in host cells that optimally perform the functions required for their life cycle. This effort illustrates the power with which RNA interference and forward genetics can be used to expose the dependencies of human pathogens such as HIV, and in so doing identify potential targets for therapy.

Editors’ note: A small virus, HIV-1 has nine genes that code only 15 proteins and yet has a complex life cycle. This elegant research began with the premise that HIV-1 must depend on host factors and found that 273 human proteins help HIV to infect cells, enter the nucleus, integrate into the human chromosome, and make copies of itself. These host-dependency factors could make excellent targets for drugs in much the same way that CCR5 inhibitors prevent viral docking for cell entry. However, we humans need these proteins too, so determining which ones we can get by without is the challenging path of research inquiry this work has opened up.

Schneider JA, Alam SA, Ackers M, Parekh B, Chen HY, Graham P, Gurwith M, Mayer K, Novak RM. Mucosal HIV-Binding Antibody and Neutralizing Activity in High-Risk HIV-Uninfected Female Participants in a Trial of HIV-Vaccine Efficacy. J Infect Dis 2007;196:1637-44.

This study investigated gp120-binding antibody and neutralizing activity, at the gingival- and cervical-mucosal levels, in response to a bivalent gp120 candidate vaccine. Women who met the study’s inclusion criteria for documented high-risk behaviours participated in a nested sub study of the multi-centre phase 3 trial of human immunodeficiency virus (HIV)-vaccine efficacy, VAX004. Gingival, cervicovaginal lavage, and plasma specimens were collected at 6-month intervals for 3 years. Binding-antibody and neutralizing-activity assays quantified the presence of anti-HIV activity in mucosal specimens. Results revealed that vaccine recipients were more likely than placebo recipients to have IgG binding antibodies in all 3 compartments tested and to have only IgA binding antibody in plasma (P<.0001). The relationship between vaccine and cervicovaginal IgG achieved significance (odds ratio [OR], 6.6 [P=.01]) but was weakened by the presence of cervicovaginal leukocytes. There was no relationship between immunization and the presence of neutralizing activity, in either bivariate or multivariate modelling (OR, 6.0 [P=.29]). Schneider and colleagues conclude that vaccination is associated with the presence of both gp120-binding IgG in all compartments and plasma IgA but not with neutralizing activity. There is a role for the measurement of mucosal immunity in response to candidate vaccines and, in particular, for a determination of HIV-specific neutralizing antibodies.

Editors’ note: This vaccine candidate did not induce the neutralizing activity in the vaginal mucosal that will be key to preventing women from becoming infected through vaginal sexual intercourse. In the future, measurement of mucosal immune responses should be systematically included as a standard component in the evaluation of vaccine candidate efficacy.

---

Trifonova RT, Bajpai M, Pasicznyk JM, Chandra N, Doncel GF, Fichorova RN. Biomarkers of leukocyte traffic and activation in the vaginal mucosa. Biomarkers 2007 Aug 22;1-15 [Epub ahead of print]

Development of novel vaginal spermicides and anti-human immunodeficiency virus (HIV) microbicides requires careful assessment of their potential to recruit and activate CD4+ HIV-1 host cells in the female genital tract mucosa, two events that facilitate HIV-1 infection. Leukocyte traffic and activation are mediated by pro-inflammatory cytokines and chemokines, e.g. interleukin (IL)-1, IL-6 and IL-8, which have been detected in vaginal secretions in association with epithelial damage and infections. These pro-inflammatory mediators, however, have bi-directional, destructive as well as beneficial, effects on the mucosal barrier, and may be counterbalanced by endogenous inhibitors. Here Trifinova and colleagues propose additional biomarkers for the evaluation of compound-induced cervicovaginal mucosal inflammation. Displaying different temporal patterns of detection, the levels of soluble E-selecting, vascular adhesion molecule-1, CD14 and myeloperoxidase in vaginal secretions reflected the mucosal leukocyte reaction to pro-inflammatory compounds being evaluated for safety in an improved rabbit vaginal irritation model. These biomarkers, which were also detected in human vaginal secretions, may be used to enhance the characterization of mucosal safety of vaginally applied compounds, both in animal as well as clinical studies.

Editors’ note: Vaginal microbicide candidates need to be evaluated by a variety of biomarkers and assays that can predict vaginal irritation before these candidates enter into large scale efficacy trials. The additional biomarkers in vaginal secretions described here (soluble E-selecting, VCAM-1, and others) may prove to be useful indicators of mucosal tissue signs of leucocyte activation suggesting a promising avenue for continued research.

Connick E, Mattila T, Folkvord JM, Schlichtemeier R, Meditz AL, Ray MG, McCarter MD, Mawhinney S, Hage A, White C, Skinner PJ. CTL Fail to Accumulate at Sites of HIV-1 Replication in Lymphoid Tissue. J Immunol 2007;178:6975-83.

The inability of HIV-1-specific CTL to fully suppress virus replication as well as the failure of administration of exogenous CTL to lower viral loads are not understood. To evaluate the hypothesis that these phenomena are due to a failure of CTL to localize at sites of HIV-1 replication, Connick and colleagues assessed the distribution of HIV-1 RNA and HIV-1-specific CTL identified by HIV-1 peptide/HLA class I tetrameric complexes (tetramers) within lymph nodes of 14 HIV-1-infected individuals who were not receiving antiretroviral therapy. A median of 0.04% of follicular compared with 0.001% of extrafollicular CD4(+) cells were estimated to be producing HIV-1 RNA, a 40-fold difference (p = 0.0001). Tetramer-stained cells were detected by flow cytometry in disaggregated lymph node cells from 11 subjects and constituted a significantly higher fraction of CD8(+) cells in lymph node (mean, 2.15%) than in PBMC (mean, 1.52%; p = 0.02). In situ tetramer staining in three subjects’ lymph nodes, in which high frequencies of tetramer-stained cells were detected, revealed that tetramer-stained cells were primarily concentrated in extrafollicular regions of lymph node and were largely absent within lymphoid follicles. These data confirm that HIV-1-specific CTL are abundant within lymphoid tissues, but fail to accumulate within lymphoid follicles where HIV-1 replication is concentrated, suggesting that lymphoid follicles may be immune-privileged sites. Mechanisms underlying the exclusion of CTL from lymphoid follicles as well as the role of lymphoid follicles in perpetuating other chronic pathogens merit further investigation.

Editors’ note: This work takes us one step further to understanding how HIV finds a safe harbour in reservoirs within lymph nodes. For reasons that remain unknown, the human foot soldiers - cytotoxic lymphocytes - don’t penetrate the lymphoid follicles where HIV is amassing its armies.

Statins have previously been shown to reduce the in vitro infection of human immunodeficiency virus type 1 (HIV-1) through modulation of Rho GTPase activity and lipid raft formation at the cell surface, as well as by disrupting LFA-1 incorporation into viral particles. Here Nabatov and colleagues demonstrate that treatment of an enriched CD4(+) lymphocyte population with lovastatin (Lov), mevastatin (Mev) and simvastatin (activated and non-activated, Sim(A) and Sim(N), respectively) can reduce the cell surface expression of the CC-chemokine receptor CCR5 (P<0.01 for Sim(A) and Lov). The lowered CCR5 expression was associated with down-regulation of CCR5 mRNA expression. The CC-chemokine RANTES protein and mRNA expression levels were slightly increased in CD4(+) enriched lymphocytes treated with statins. Both R5 and X4 HIV-1 were reduced for their infection of statin-treated cells; however, in cultures where statins were removed and where a decrease in CCR5 expression was observed, there was a preferential inhibition of infection with an R5 versus X4 virus. In conclusion, the results indicate that the modulation of CC-chemokine receptor (CCR5) and CC-chemokine (RANTES) expression levels should be considered as contributing to the anti-viral effects of statins, preferentially inhibiting R5 viruses. This observation, in combination with the immuno-modulatory activity exerted by statins, suggests they may possess more potent anti-HIV-1 activity when applied during the early stages of infection or in lowering viral transmission. Alternatively, statin treatment could be considered as a way to modulate immune induction such as during vaccination protocols.

Editors’ note: These are ‘early days’ for statins, the well known anti-cholesterol drug class, as potential HIV treatment candidates. They may have both anti-viral and immuno-modulatory effects but so far these are all in vitro findings, meaning in the laboratory, as opposed to in vivo findings in human subjects.

Reiche EM, Bonametti AM, Voltarelli JC, Morimoto HK, Watanabe MA. Genetic polymorphisms in the chemokine and chemokine receptors: impact on clinical course and therapy of the human immunodeficiency virus type 1 infection (HIV-1). Curr Med Chem. 2007;14(12):1325-34.

The natural history and pathogenic processes of infection by the human immunodeficiency virus type 1 (HIV-1) are complex, variable, and dependent upon a multitude of viral and host factors and their interactions. The CCR5-Delta32 allele remains the most important genetic factor known to be associated with host resistance to the HIV-1 infection. However, other mutations in the CCR5, CCR2, CX(3)CR1, CXCL12 (SDF1), and CCL5 (RANTES) genes have been identified and associated with host resistance and/or susceptibility to HIV-1 infection and disease progression. Some studies have also suggested that chemokine receptor gene polymorphisms may affect response to potent antiretroviral therapy. This article reviews the polymorphisms already described in the mutant chemokine receptors or ligands and their impact on the host susceptibility to HIV-1 infection and on the clinical course of the disease, as well as the development of new anti-HIV therapies that takes into account these potential targets in the host. These genetic polymorphisms could be used as genetic markers to detect individuals at higher risk of developing either a faster disease progression or therapeutic failure. Once these individuals are identified, therapeutic strategies based on either different, more aggressive drugs or combinations of drugs can be used, either alone or in combination with shorter intervals for therapeutic monitoring. Pharmaco-genetics is very likely to underlie future therapies for HIV-1 infection, and current patients with multi-resistance to the existing antiretroviral agents could also benefit from this approach. These developments also underscore the importance of continuing the investigation of new therapies targeted to the host in order to inhibit the HIV-1 entry into the host cells.

Editors’ note: Detecting genetic polymorphisms and determining their influence on HIV disease progression place emphasis on host characteristics rather than solely on viral resistance. It could lead eventually to the tailoring of the timing and composition of antiretroviral therapy for individual patients, as well as different monitoring frequencies both before and after antiretroviral initiation based on patient genetic profiles.

Ofori-Mante JA, Kaul A, Rigaud M, Fidelia A, Rochford G, Krasinski K, Chandwani S, Borkowsky W. Natural history of HIV infected pediatric long-term or slow progressor population after the first decade of life. Pediatr Infect Dis J 2007 Mar;26(3):217-20.

Photo credit: UNAIDS/K.Krobe

Perinatally infected long-term non-progressors/slow progressors represent a select group of individuals. There is very limited information on this group of children beyond the first decade of life. A group of HIV-infected long-term non-progressor/slow progressor children was studied. Ofori-Mante and colleagues enrolled 20 HIV-infected adolescents who were receiving no or minimal therapy (defined as single or dual nucleoside therapy) before the age of 10 years and who had maintained CD4 counts above 25% for the first decade of life. The authors analyzed immunologic and virologic characteristics. Thymic receptor excision circles (TREC) were measured on stored frozen peripheral blood mononuclear cells. CD4 count, viral load and other pertinent information including race and age were obtained from individual medical records. The results revealed that nine of the 20 patients recruited were noted to have developed falling CD4 counts at or around puberty, whereas the other 11 remained stable. There was no difference in TREC values or HIV RNA values before or after puberty between the 2 groups of patients. Those who remained stable, in terms of maintaining CD4 T cells as a group had falling viral loads with age. Those whose CD4 values declined after puberty had viral loads that did not decrease with age. The authors conclude that a select group of patients who never received HAART during their first decade of life will continue to maintain good CD4 associated with declining HIV RNA values. Thymic output is not predictive of those that don’t maintain CD4 T cells.

Editors’ note: How do the immune defences, in this select group of adolescents infected at birth, work to maintain CD4 count levels and produce falling viral loads with age? Answering this question could take us a long way along the path to understanding HIV immunology – and, for that matter, immunology in general.

The persistence of latently infected resting CD4(+) T cells has been clearly demonstrated in human immunodeficiency virus (HIV)-infected individuals receiving effective antiviral therapy. However, estimates of the half-life of this viral reservoir have been quite divergent. Chun and colleagues demonstrate clear evidence for decay of this HIV reservoir in patients who initiated antiviral therapy early in infection. The half-life of this latent viral reservoir was estimated to be 4.6 months. It is projected that it will take up to 7.7 years of continuous therapy to completely eliminate latently infected resting CD4(+) T cells in infected individuals who initiate antiviral therapy early in HIV infection.

Editors’ note: The idea that early treatment could eventually eliminate latently infected CD4 cells is not new but remains to be proven. In the meantime, long term commitment both by individuals to adhere to treatment and by governments and development partners to ensure sustained access to antiretroviral treatment programmes is essential.

When antiretroviral therapy (ART) is administered for long periods to HIV-1-infected patients, most achieve viral loads that are « undetectable » by standard assay methods (ie, HIV-1 RNA <50 copies/mL). Despite sustaining viral loads lower than the level of detection, a number of patients experience unexplained episodes of transient viremia or viral « blips. » Jone and Perelson propose that transient activation of the immune system by infectious agents may explain these episodes of viremia. Using 2 different mathematical models, one in which blips arise because of target cell activation and subsequent infection and another in which latent cell activation generates blips, the authors establish a nonlinear (power law) relationship between blip amplitude and viral load (under ART) that suggest blips should be of lower amplitude, and thus harder to detect, as increasingly potent therapy is used. This effect can be more profound than is predicted by simply lowering the baseline viral load from which blips originate. Finally, the authors suggest that sporadic immune activation may elevate the level of chronically infected cells and replenish viral reservoirs, including the latent cell reservoir, providing a mechanism for recurrent viral blips and low levels of viremia under ART.

Editors’ note: Intercurrent infections such as colds, flu, and herpes simplex and other sexually transmitted infections in all people tend to activate the immune system transiently to mount a defence. In people living with HIV this immune activation leads to transient HIV viraemia which may replenish viral reservoirs. If the goal is to deplete HIV’s reservoirs, then where possible, people living with HIV should take steps to prevent other infections (hand washing, flu shots, safer sex and rapid treatment of sexually transmitted infections) which may replenish the reservoirs.

Nair V, Chi G. HIV integrase inhibitors as therapeutic agents in AIDS. Rev Med Virol 2007 Jul-Aug; 17(4):277-95

HIV-1 integrase is a protein of Mr 32 000 encoded at the 3’-end of the pol gene. Integration of HIV DNA into the host cell chromosomal DNA apparently occurs by a carefully defined sequence of DNA tailoring (3’-processing (3’P)) and coupling (integration) reactions. Integration of HIV DNA into human DNA represents the biochemical completion of the invasion of the human cell (e.g., T-cell) by HIV. Unlike major successes seen in the development of clinically approved anti-HIV agents against HIV reverse transcriptase and HIV protease, there are no FDA-approved anti-HIV drugs in clinical use where the mechanism of action is inhibition of HIV integrase. This review summarises some key advances in the area of integrase inhibitors with the major focus being on new generation inhibitors. Special emphasis is placed on diketo acids with aromatic and heteroaromatic moieties, diketo acids with nucleobase scaffolds, bis-diketo acids, functionalised naphthyridines and other isosteres of diketo acids. Data pertaining to integrase inhibition and in vitro anti-HIV activity are discussed. Mention is made of drugs in clinical trials, both past (S-1360, L-870,810 and L-870,812 and present (GS-9137 and MK-0518). Other promising drugs, including those from the authors’ laboratory, are referred. Resistant mutants arising from key integrase inhibitors and cross-resistance are indicated.  

Editors’ note: Clinical trials are currently underway of 2 new classes of antiretroviral drugs that target the viral co-receptor CCR5 and the viral integrase enzyme. For the latter, preventing the integration of HIV into human DNA (integration allows HIV to take over the cell machinery) is a critical challenge — and doing so without important side effects is key. If they work, integrase inhibitors could be particularly beneficial for people who have developed HIV resistance to drugs that target HIV’s two other major enzymes: reverse transcriptase and protease

Molecular umbrella compounds may function as novel topical microbicides to prevent HIV and HSV (herpes simplex virus) infection. In a preliminary structure-activity investigation, one umbrella compound, designated Spm8CHAS, was identified which inhibited both HIV and HSV infection with no cellular toxicity. The objectives of the current studies were to define its spectrum of antiviral activity, characterize its mechanism of action, and explore the possibility of combining Spm8CHAS with HIV-specific reverse transcriptase inhibitors. Spm8CHAS inhibited infection by laboratory and clinical R5 and X4 clade B and clade C HIV strains in cell culture. Ectocervical tissue explants exposed to HIV-1BaL in the presence of Spm8CHAS were completely protected (IC50=13.6 microg/ml), and transfer of virus to target T-cells via migratory cells was abolished (IC50=3.8 microg/ml). Spm8CHAS inhibited HSV-2 infection of epithelial cells 10,000-fold if present throughout the infection. Notably, adding Spm8CHAS to cultures following HSV entry significantly reduced viral infection, indicating that the drug also acts post-entry. Subsequent studies indicate that Spm8CHAS blocks cell to cell spread of HSV. Confocal microscopy using a fluorescently labelled analogue of Spm8CHAS demonstrated that this conjugate crosses the plasma cell membrane and is transported to the nucleus. Combinations of Spm8CHAS with UC-781 or PMPA in vitro exhibited additive anti-HIV activity with preserved anti-HSV activity. The ability of Spm8CHAS to inhibit primary isolates of HIV, block HSV infection post-entry, and cross cell membranes supports the development of a combination microbicide containing Spm8CHAS with an HIV-specific reverse transcriptase inhibitor to prevent both HIV and HSV by multiple mechanisms.

Editors’ note: Molecular umbrella compounds can inhibit both HIV and HSV. In vitro testing of this one – Spm8CHAS – suggests that its ability to inhibit HIV infection (cross-clade), block HIV transfer to T-cells via migratory cells and block HSV spread from cell to cell, if combined with an HIV specific reverse transcriptase inhibitor, would create a potent combo that holds promise for the prevention not only of HIV acquisition but of HSV as well.

Nickle DC, Rolland M, Jensen MA, Pond SL, Deng W, Seligman M, Heckerman D, Mullins JI, Jojic N. Coping with viral diversity in HIV vaccine design. PLoS Comput Biol 2007;3:e75.

The ability of human immunodeficiency virus type 1 (HIV-1) to develop high levels of genetic diversity, and thereby acquire mutations to escape immune pressures, contributes to the difficulties in producing a vaccine. Possibly no single HIV-1 sequence can induce sufficiently broad immunity to protect against a wide variety of infectious strains, or block mutational escape pathways available to the virus after infection. The authors describe the generation of HIV-1 immunogens that minimizes the phylogenetic distance of viral strains throughout the known viral population (the center of tree [COT]) and then extend the COT immunogen by addition of a composite sequence that includes high-frequency variable sites preserved in their native contexts. The resulting COT(+) antigens compress the variation found in many independent HIV-1 isolates into lengths suitable for vaccine immunogens. It is possible to capture 62% of the variation found in the Nef protein and 82% of the variation in the Gag protein into immunogens of three gene lengths. The authors put forward immunogen designs that maximize representation of the diverse antigenic features present in a spectrum of HIV-1 strains. These immunogens should elicit immune responses against high-frequency viral strains as well as against most mutant forms of the virus.

Editors’ note: These scientists are using computer programmes to design immunogens that could be used in vaccines to stimulate immune responses against a broad array of HIV-1 strains, including mutated strains. This is one of many different avenues being explored in the race/marathon to find an effective HIV vaccine.

Munch J, Standker L, Adermann K, Schulz A, Schindler M, Chinnadurai R, Pohlmann S, Chaipan C, Biet T, Peters T, Meyer B, Wilhelm D, Lu H, Jing W, Jiang S, Forssmann WG, Kirchhoff F. Discovery and optimization of a natural HIV-1 entry inhibitor targeting the gp41 fusion peptide. Cell 2007;129:263-75.

A variety of molecules in human blood have been implicated in the inhibition of HIV-1. However, it remained elusive which circulating natural compounds are most effective in controlling viral replication in vivo. To identify natural HIV-1 inhibitors Munch and colleagues screened a comprehensive peptide library generated from human hemofiltrate. The most potent fraction contained a 20-residue peptide, designated VIRUS-INHIBITORY PEPTIDE (VIRIP), corresponding to the C-proximal region of alpha1-antitrypsin, the most abundant circulating serine protease inhibitor. The authors found that VIRIP inhibits a wide variety of HIV-1 strains including those resistant to current antiretroviral drugs. Further analysis demonstrated that VIRIP blocks HIV-1 entry by interacting with the gp41 fusion peptide and showed that a few amino acid changes increase its antiretroviral potency by two orders of magnitude. Thus, as a highly specific natural inhibitor of the HIV-1 gp41 fusion peptide, VIRIP may lead to the development of another class of antiretroviral drugs.

Editors’ note: The identification of this natural defence and its action against even drug-resistant HIV is encouraging.

Fahrbach KM, Barry SM, Ayehunie S, Lamore S, Klausner M, Hope TJ. Activated CD34 derived Langerhans cells mediate trans-infection of HIV. J Virol 2007 Apr 18; [Epub ahead of print]

Langerhans cells (LCs) are a subset of dendritic cells (DCs) that reside within epidermal and mucosal tissue. Because of their location, LCs are potentially the first cells to encounter HIV during sexual transmission. Fahrback and colleagues report that LCs purified from CD34+ derived DCs can facilitate the trans-infection of target cells, but only after activation. Virions were observed in an intracellular compartment that contains several tetraspanins, in addition to the unique LC markers langerin and CD1a. This reveals that the trafficking of HIV within Langerhans cells is reminiscent of that which occurs in mature MD dendritic cells and that it varies with the activation state of the cell. The observation that activated LCs can mediate trans-infection suggests a potential role for these cells in the known increase in HIV transmission associated with sexually transmitted infections that would cause inflammation of the genital lining.

Editors’ note: Langerhans cells are back again, this time mediating trans-infection of target cells by trafficking HIV when they themselves are activated, possibly by sexually transmitted infections. The plot thickens….

Esparza J, Yamada T. The discovery value of “Big Science”. J Exp Med 2007 Apr 9; [Epub ahead of print]

The increasing complexity of biomedical research is leading to the exploration of new models for large-scale collaborative research. This Big Science approach, however, has created anxieties and potential tensions between investigator-driven research, and research guided by a more organized, collaborative effort. Another potential tension exists between research conducted purely in search of new knowledge and research aimed at finding solutions. Esparza and Yamada argue that big biomedicine-the work of coordinated multidisciplinary groups that use the latest technologies to solve complex problems-can be an important way to harness the creativity of individual investigators, stimulate innovation, and supply the infrastructure, experimental systems, and resources needed to solve the urgent health problems confronted by our global society. The authors discuss this using the example of the Global HIV Vaccine Enterprise.

Editors’ note: The War on Cancer (launched in 1971) and the Human Genome Project (launched about 20 years ago) are examples of big science initiatives which have brought tremendous scientific advancement far beyond that which would have resulted from individual investigator curiosity alone. Overall incidence, mortality and mobidity from cancer have decreased and genetic discoveries, which can lead to treatment and prevention of a diverse array of diseases, make the news virtually weekly. The Global HIV Vaccine Enterprise (UNAIDS sits on its Coordinating Committee) arose from the recognition that attempts to develop an HIV vaccine lacked scale and focus. Innovation is the key to both Little and Big Science but as the authors state about an HIV vaccine “…we cannot afford to work selfishly in silos and for personal gain. There are too many people waiting anxiously for the solutions that we must deliver.”

Diaz Munoz L, Serramia MJ, Fresno M, Munoz-Fernandez MA. Progesterone inhibits HIV-1 replication in human trophoblast cells through inhibition of autocrine tumor necrosis factor secretion. J Infect Dis 2007;195:1294-302.

Progesterone levels are higher in placental barriers during pregnancy, but the effect of progesterone on human immunodeficiency virus type 1 (HIV-1) infection in placental cells has not been addressed. Diaz Munoz and colleagues hypothesize that progesterone may affect HIV infection. Purified trophoblastic cells and trophoblastic cell lines were infected or transfected with HIV-1, and the effect of progesterone was analyzed. Viral replication was measured by viral p24 or viral load quantification. Nuclear factor kappa -B (NF- kappa B) or long terminal repeat (LTR)-dependent transcription was measured by luciferase assays. Expression of chemokine receptors was analyzed by flow cytometry. Tumor necrosis factor ( TNF) messenger RNA was assessed by reverse- transcription polymerase chain reaction (RT-PCR) and quantitative RT-PCR. Results. Progesterone inhibits HIV-1 replication in placental cells at the concentration found in the placental interface, at a postentry step, doest not affect cell surface expression of chemokine receptors. Progesterone did not inhibit basal or induced LTR transcription or NF-kappa B activation. . TNF synthesis in placental cells is induced by HIV-1 infection that, in an autocrine manner, activates viral replication, because neutralizing anti-TNF antibodies block it. Progesterone inhibits the induction of TNF synthesis by viral infection and virus or gp-120-induced TNF transcription. The authors’ results demonstrate that progesterone inhibits HIV-1 replication in placental cells by reducing TNF levels, which are required for optimal viral replication.

Editors’ note: This study provides some insight as to why the rate of HIV transmission is so low during pregnancy itself. Progesterone in the placenta is helping stop the virus in its tracks.

Petitjean G, Becquart P, Tuaillon E, Al Tabaa Y, Valea D, Huguet MF, Meda N, Van de Perre P, Vendrell JP. Isolation and characterization of HIV-1-infected resting CD4(+) T lymphocytes in breast milk. J Clin Virol 2007;39:1-8.

An HIV-1 reservoir comprised primarily of latently infected resting CD4(+) T lymphocytes that can be stimulated in vivo to produce virus may play a critical role in mother-to-child postnatal transmission of HIV-1 by breastfeeding. Here, Petitjean and colleagues describe an experimental protocol for the detection of resting CD4(+) T cell HIV-1 reservoir from breast milk. The authors adapted a method for the purification of resting CD4(+) T lymphocytes in blood to isolate resting CD4(+) T cells in breast milk from HIV-1-infected-lactating women (n=18) and from controls (n=3). Purified resting CD4(+) T cells from blood and breast milk samples of HIV-1-infected-lactating women were polyclonally stimulated to characterize and enumerate HIV-1-antigen-secreting cells (HIV-1-Ag-SCs) by an enzyme-linked immunospot (ELISpot) assay. Resting CD4(+) T cells represented more than 90% of purified viable breast milk cells. CD4(+) T cell polyclonal stimulation combined with the ELISpot assay led to the characterization of a breast milk T cell HIV-1 reservoir greater than the blood reservoir (median 400 and 57.14 HIV-1-Ag-SCs/10(6) resting CD4(+) T cells, respectively, p<0.001). The authors’ strategy could be adapted to other body fluids and be useful for characterizing new HIV-1 reservoirs.

Editors’ note: Breast milk contains a latent CD4 (+) T lymphocyte reservoir that can be activated for viral replication. Developing techniques to study this pathway further, and how to interrupt it, could have implications for reservoirs in other body fluid compartments.

Lunzen J, Glaunsinger T, Stahmer I, Baehr V, Baum C, Schilz A, Kuehlcke K, Naundorf S, Martinius H, Hermann F, Giroglou T, Newrzela S, Muller I, Brauer F, Brandenburg G, Alexandrov A, von Laer D. Transfer of autologous gene-modified T cells in HIV-infected patients with advanced immunodeficiency and drug-resistant virus. Mol Ther 2007;15:1024-33.

Drug toxicity and viral resistance limit the long-term efficacy of antiviral drug treatment for human immunodeficiency virus (HIV) infection. Thus, alternative therapies need to be explored. Lunzen and colleagues tested the infusion of T lymphocytes transduced with a retroviral vector (M87o) that expresses an HIV entry-inhibitory peptide (maC46). Gene-modified autologous T cells were infused into ten HIV-infected patients with advanced disease and multidrug-resistant virus during antiretroviral combination therapy. T-cell infusions were tolerated well, with no severe side effects. A significant increase of CD4 counts was observed after infusion. At the end of the 1-year follow-up, the CD4 counts of all patients were still around or above baseline. Gene-modified cells could be detected in peripheral blood, lymph nodes, and bone marrow throughout the 1-year follow-up, and marking levels correlated with the cell dose. No significant changes of viral load were observed during the first 4 months. Four of the seven patients who changed their antiviral drug regimen thereafter responded with a significant decline in plasma viral load. In conclusion, the transfer of gene-modified cells was safe, led to sustained levels of gene marking, and may improve immune competence in HIV-infected patients with advanced disease and multidrug-resistant virus.

Editors’ note: Gene therapy is a new frontier in HIV treatment just as it is in the treatment of cancer and inherited genetic disorders. In this case, infusing patients’ T-cells which have been modified to inhibit HIV entry was found to be safe in ten people so it is likely that a larger study will now be conducted to look more closely at the extent and significance of the immunological effects.

An estimated 25 million lives have been lost to acquired immune-deficiency syndrome (AIDS) since the immunodeficiency syndrome was first described in 1981. The progress made in the field of treatment in the form of antiretroviral therapy (ART) for HIV disease/AIDS has prolonged as well as improved the quality of life of HIV-infected individuals. However, access to such treatment remains a major concern in most parts of the world, especially in the developing countries. Hence, there is a constant need to find low-cost interventions to complement the role of ART in prevention of HIV infection and slowing clinical disease progression. Nutritional interventions, particularly vitamin supplementation, have the potential to be a low-cost method for being such an intervention by virtue of their modulation of the immune system. Among all the vitamins, the role of vitamin A has been studied most extensively; most observational studies have found that low vitamin A levels are associated with increased risk of transmission of HIV from mother to child. This finding has not been supported by large randomized trials of vitamin A supplementation; on the contrary, these trials have found that vitamin A supplementation increases the risk of mother-to-child transmission (MTCT). There are a number of potential mechanisms that might explain these contradictory findings. One is the issue of reverse causality in observational studies-for instance, advanced HIV disease may suppress release of vitamin A from the liver. This would lead to low levels of vitamin A in the plasma despite the body having enough vitamin A liver stores. Further, advanced HIV disease is likely to increase the risk of MTCT, and hence it would appear that low serum vitamin A levels are associated with increased MTCT. The HIV genome also has a retinoic acid receptor element: Hence, vitamin A may increase HIV replication via interacting with this element, thus increasing risk of MTCT. Finally, vitamin A is known to increase lymphoid cell differentiation, which leads to an increase in CCR5 receptors. These receptors are essential for attachment of HIV to the lymphocytes and therefore, an increase in their number is likely to increase HIV replication. Vitamin A supplementation in HIV-infected children, on the other hand, has been associated with protective effects against mortality and morbidity, similar to that seen in HIV-negative children. The risk for lower respiratory tract infection and severe watery diarrhoea has been shown to be lower in HIV-infected children supplemented with vitamin A. All-cause mortality and AIDS-related deaths have also been found to be lower in vitamin A-supplemented HIV-infected children. The benefits of multivitamin supplementation, particularly vitamins B, C, and E, have been more consistent across studies. Multivitamin supplementation in HIV-infected pregnant mothers has been shown to reduce the incidence of adverse pregnancy outcomes such as foetal loss and low birth weight. It also has been shown to decrease rates of MTCT among women who have poor nutritional or immunologic status. Further, multivitamin supplementation reduces the rate of HIV disease progression among patients in early stage of disease, thus delaying the need for ART by prolonging the pre-ART stage. In brief, there is no evidence to recommend vitamin A supplementation of HIV-infected pregnant women; however, periodic vitamin A supplementation of HIV-infected infants and children is beneficial in reducing all-cause mortality and morbidity and is recommended. Similarly, multivitamin supplementation of people infected with HIV, particularly pregnant women, is strongly suggested.

Editors’ note: It has taken quite some time to tease out the role of vitamin A deficiency and whether supplementation is useful and if so, for whom. Although vitamin A deficiency does not appear to increase the risk of HIV transmission, it should be treated and prevented in people living with HIV of all ages on general health grounds.