HIV This Week

Soto RJ, Ghee AE, Nuñez CA, Mayorga R, Tapia KA, Astete SG, Hughes JP, Buffardi AL, Holte SE, Holmes KK; and the Estudio Multicéntrico Study Team. Sentinel surveillance of sexually transmitted infection/HIV and risk behaviors in vulnerable populations in 5 Central American countries. J Acquir Immune Defic Syndr 2007 Sep 1;46(1):101-11.

In El Salvador, Guatemala, Honduras, Nicaragua, and Panama, Soto and colleagues recruited 2466 female sex workers (FSWs) by probabilistic or comprehensive sampling and 1418 men who have sex with men (MSM) by convenience sampling to measure sociobehavioural risk and sexually transmitted infections. For MSM, HIV seroprevalence ranged from 7.6% in Nicaragua to 15.3% in El Salvador, and estimated HIV seroincidence per 100 person-years ranged from 2.7 in Panama to 14.4 in Nicaragua; 61% reported using condoms consistently with casual male partners, 29% reported exposure to behavioural interventions, and 22% reported recent sex with male and female partners. For female sex workers, HIV seroprevalence ranged from 0.2% in Nicaragua and Panama to 9.6% in Honduras, where estimated HIV seroincidence was also highest (3.2 per 100 person-years); 77% and 72% of FSWs reported using condoms consistently with new and regular clients. Herpes simplex virus (HSV)-2 seroprevalence averaged 85.3% in FSWs and 48.2% in MSM, and syphilis seropositivity averaged 9.6% in FSWs and 8.3% in MSM. Chlamydia trachomatis and Neisseria gonorrhoeae prevalences in FSWs averaged 20.1% and 8.1%, and Trichomonas vaginalis and bacterial vaginosis prevalences averaged 11.0% and 54.8%. An ongoing HIV epidemic involves Central American MSM with potential bridging to women. In female sex workers, HSV-2 infection was associated with HIV infection (odds ratio = 11.0, 95% confidence interval: 2.9 to 7.9). For these vulnerable populations, prevention must incorporate acceptable and effective sexual health services, including improved condom access and promotion.

Editors’ note: This regional epidemiologic profile of 5 countries demonstrates the extent to which HIV has found fertile soil among populations with high levels of sexually transmitted infections, including HSV-2. The negative results of the HSV-2 randomised controlled trial which were reported at the Retrovirus Conference this week suggest that suppressing herpes does not reduce the risk of HIV acquisition but one senses that the story is not fully told. In the meantime there is much to be done to address the health needs of MSM and sex workers in Central America.

Lau KA, Wang B, Saksena NK. Emerging trends of HIV epidemiology in Asia. AIDS Rev. 2007 Oct-Dec;9(4):218-29

The main molecular trait of HIV-1 is the inherent capacity to vary, recombine, and diversify, which gives it a clear edge to evade the human immune system and survive through the generation of complex molecular forms, termed recombinants. In a setting of coinfection, molecular and biological interactions between diverse HIV-1 subtypes may promote the emergence of circulating recombinant forms through the shuffling of viral genomes, which results in increased intra- and inter- host viral variation and altered biological properties. The focus of this review is on Asia, which has the highest proportion of HIV-1 recombinants circulating worldwide, with the top in South and Southeast Asia, amounting to 89% of its total HIV-1 infection. The HIV-1 strains which are spreading in this geographic area are CRF01_AE, subtypes B and C. Given the rapid spread and active establishment of some of the recombinant forms in Asia, it is essential to understand how they differ from their parental strains, the acquisition of certain molecular traits, and their biological attributes upon recombination, which give these strains an epidemiologic edge. The current epidemic provides strong evidence that the parental subtypes are being replaced via competition with possibly more versatile HIV-1 recombinant forms. This appears to be an ongoing phenomenon and has resulted in an HIV-1 epidemic shift, with the expansion and dissemination of a wide variety of HIV-1 forms within this geographic region.

Editors’ note: When two different subtypes infect the same person, either at the same time or sequentially, they can swap pieces of genetic material, forming recombinant viral strains. For example, the strain CRF01 AE is a recombinant of an A and an E subtype. Some of these recombinant strains may behave differently from either of their two “parent” strains in terms of transmissibility, disease progression potential, and sensitivity towards antiretroviral drugs. Understanding how these recombinant forms develop and spread can help predict evolution of the epidemic but it is the virus’s ability to keep a step ahead of the immune system through recombination and other tricks that make vaccine development seem so daunting at times.