Researchers on Monday at the International Microbicides Conference (M2010) in Pittsburgh continued to present data on HIV prevention research, Reuters reports. The news service outlines several prevention methods being researched, including an intravaginal ring that over time releases two antiretrovirals (ARVs) – dapivirine and maraviroc – for up to a month, and a vaginal tablet that time-releases the antiretrovirals dapivirine and DS003 for up to 12 hours. Both methods have yet to reach clinical trials.

Reuters also notes that researchers have formulated a vaginal film containing the ARV compound IQP-0528 that is currently undergoing laboratory tests (Fox, 5/24). Full descriptions of the data presented on these techniques for protecting women from HIV transmission is available in an M2010 press release (.pdf) (5/23).

Times Live’s “Tracking HIV” blog reports on discussion at the conference about Pre-Exposure Prophylaxis (PrEP), where HIV-negative patients take ARVs as a method of prevention. In order to avoid an increase in ARV drug resistance, researchers warned Monday during the M2010 conference that anyone taking PrEP must first know his or her HIV status, “Tracking HIV” reports. 

The University of Pittsburgh’s John Mellors “expressed concern at the ‘substantial overlap in the drugs being used for treatment and those being studied for prevention.’ He said in a worst case scenario widespread resistance at a population level to these drugs could end up rendering them ineffective for both treatment and prevention. But he added: ‘It is very rare to become infected with a virus we can’t treat today,'” the blog reports (Keeton, 5/24).

A press release (.pdf) from M2010 details the results of two studies presented at the conference that examine how using ARVs for prevention could contribute to drug resistance.

For one of the two studies presented, Ume Abbas of the Cleveland Clinic Foundation helped lead a team of researchers in the development of a mathematical model “to simulate the impact of PrEP on HIV prevention and drug resistance in a region of sub-Saharan Africa, where HIV rates are among the highest, and to identify the determinants contributing most to HIV drug resistance prevalence,” according to the press release. “The model singled out two factors having the most influence, finding that the greater number of people who use PrEP who shouldn’t be and the longer they keep using the ARVs, the more prevalent drug resistance would be,” according to the press release.

The press release describes a second laboratory study where researchers “infected blood cells with different subtypes of HIV and exposed the infected cells to dapivirine alone and to dapivirine plus tenofovir continuously for more than 25 weeks to induce drug resistance” to test whether ARV-based microbicide compounds could cause the virus to become resistant. ” Drug resistance emerged only if HIV infection was present before the candidate microbicide ARVs were introduced and continued to be used,” according to the release (5/23).