HIV This Week

Chenine A-L, Shai-Kobiler E, Steele LN, Ong H, Augostini P, et al. Acute Schistosoma mansoni Infection Increases Susceptibility to Systemic SHIV Clade C Infection in Rhesus Macaques after Mucosal Virus Exposure. PLoS Negl Trop Dis. 2008;2(7):e265

Individuals living in sub-Saharan Africa represent 10% of the world’s population but almost 2/3 of all people living with HIV. The disproportionate HIV-1 infection rates in this region may be linked to helminthic parasite infections that affect many individuals in the developing world. However, the hypothesis that parasite infection increases an individual’s susceptibility to HIV-1 has never been prospectively tested in a relevant in vivo model. Chenine and colleagues measured whether pre-existing infection of rhesus monkeys with a parasitic worm would facilitate systemic infection after mucosal AIDS virus exposure. Two groups of animals, one consisting of normal monkeys and the other harbouring Schistosoma mansoni, were challenged intra-rectally with decreasing doses of R5-tropic clade C simian-human immunodeficiency virus (SHIV-C). Systemic infection occurred in parasitized monkeys at viral doses that remained sub-infectious in normal hosts. In fact, the 50% animal infectious (AID50) SHIV-C dose was 17-fold lower in parasitized animals compared to controls (P = 0.001). Coinfected animals also had significantly higher peak viral RNA loads than controls (P = 0.001), as well as increased viral replication in CD4+ central memory cells (P = 0.03). These data provide the first direct evidence that acute schistosomiasis significantly increases the risk of de novo HIV acquisition, and the magnitude of the effect suggests that control of helminth infections may be a useful public health intervention to help decrease the spread of HIV-1.

Editors’ note: The possibility that helminth infections could be a risk factor for increased susceptibility to HIV infection among people living in areas endemic for these parasites has been raised for years. Macaques self cure their schistosomiasis 20 to 25 weeks after exposure to cercariae which limits the application of these findings to the acute phase of schistosomiasis. However, treatment of helminth infections is inexpensive, safe, and easily administered to communities. Important in its own sake, treatment of helminth infections in endemic areas should be further studied for its possible role in HIV prevention.