According to estimates by the World Health Organisation, at the end of 2011, 34 million people worldwide were infected with the human immunodeficiency virus (HIV) responsible for acquired immunodeficiency syndrome (AIDS), a condition in which the immune system progressively fails. That same year, 2.5 million people became newly infected, and 1.7 million died of AIDS-related causes, such as opportunistic infections and cancers. There is currently no cure or vaccine, though lifelong treatment with antiretroviral therapy (ART) can control the progression of the disease.
HIV is spread via the exchange of body fluids from infected individuals, including blood, semen, vaginal secretions and breast milk. The majority of new HIV infections are in sub-Saharan Africa, where heterosexual sex is the main mode of viral transmission.
While numerous animal models have been developed to find chinks in HIV’s armour in the hope of developing a vaccine, none of these mimicked the main route of HIV transmission – vaginal sex – until now. In their paper just published in the open access journal Disease Models and Mechanisms, Hadas et al describe how male mice infected with a genetically modified version of HIV that propagates in rodents instead of humans, efficiently transmitted the virus to uninfected female mice. Male mice infected with the modified virus (EcoHIV/NDK) were allowed to mate with uninfected females for 1-7 nights; 70-100% of the females became infected.
This is exciting news, as now scientists have a relatively cost-effective and simple model to investigate the efficacy of strategies for preventing infection. Indeed, the researchers found that treating the female mice with ART prior to mating largely prevented them becoming infected with EcoHIV/NDK. Interestingly, they also found a significant drop in HIV transmission when female mice were in heat (estrus), suggesting that the local environment of the female reproductive tract has an effect on susceptibility to the virus.
E. Hadas, W. Chao, H. He, M. Saini, E. Daley, M. Saifuddin, G. Bentsman, E. Ganz, D. J. Volsky, M. J. Potash. Transmission of chimeric HIV by mating in conventional mice: prevention by pre-exposure antiretroviral therapy and reduced susceptibility during estrus. Disease Models & Mechanisms, 2013; DOI: 10.1242/dmm.012617