A new weapon has emerged to prevent HIV infection. Called pre-exposure prophylaxis, or PrEP, it is a strategy of providing medications to at-risk people before they are exposed to the virus. Having shown great promise in recent phase 3 clinical trials, PrEP may soon be rolled out for public use.
Doctor Sally Blower and colleagues used sophisticated computer modelling to determine that a PrEP prevention program used alone, or current HIV treatment programs used alone, could indeed, separately, increase drug resistance. But if used together, the researchers say, resistance is likely to decrease.
"This was a very big surprise," said Blower. "We found that this counterintuitive effect will only occur if adherence to the PrEP prevention program, where individuals have to take a daily pill, is very high. This counterintuitive effect occurs when the beneficial effect of PrEP in preventing infections is so great that it overcomes both its own detrimental effect on increasing resistance and the detrimental effect of current HIV treatments on increasing resistance."
Africa is ground zero for HIV and AIDS, a continent where the death rate is simply "awful," Blower said. Since the country of Botswana was one of the sites for the PrEP drug trial, Blower and her colleagues chose it for their modeling. Botswana has the best health care system in Africa, they said, yet 30 per cent of women and 20 per cent of men are infected with HIV.
"Botswana is likely to lead the way in rolling out PrEP," said Virginie Supervie. "So officials there are worried about increasing levels of resistance."
Most health officials feel that if you have a good treatment program in place, it makes sense to establish a good prevention program in the same place. Health officials plan to implement PrEP prevention programs only where treatment programs are highly successful and levels of resistance are low, the researchers said.
But in a second counterintuitive finding, the UCLA researchers say this conventional approach is actually the worst strategy. Instead, they suggest, PrEP programs should be rolled out around treatment programs that are having little success and where rates of resistance are high. Their model shows that this unconventional approach would prevent the maximum number of infections and result in the greatest decrease in drug resistance.
A PrEP clinical trial that involved men who had sex with men and transgender women who had sex with men found that PrEP reduced the risk of acquiring HIV infection by 44 per cent. Two other PrEP trials, which involved heterosexual men and women, showed significant reductions in risk, ranging as high as 73 per cent.
MEDICA.de; Source: University of California - Los Angeles (UCLA)