Treating co-infections can lower HIV viral load, reducing risk of transmission and improving prognosis

Small declines in viral load achieved without anti-HIV drugs by treating infections can reduce the risk of heterosexual HIV transmission and HIV disease progression, according to a review article published in the October edition of AIDS. As almost three-quarters of HIV-infected individuals are not taking anti-HIV drugs the authors believe that treatment for infections could have an important impact on the epidemiology of HIV and the prognosis of HIV-positive patients.

Access to antiretroviral therapy in resource-limited settings has expanded significantly in recent years. The overwhelming majority of HIV-positive individuals, however, are not yet receiving anti-HIV drugs because of problems accessing treatment or because the health of their immune system does not warrant it.

There is therefore a need, argue the authors of the article, for “cheap, implementable, and sustainable approaches” to prevent HIV transmission and to improve the prognosis of HIV-positive people not taking antiretroviral therapy.

Earlier studies have suggested that treating infections in people with HIV leads to a small, but sustained fall in viral load.

The authors wanted to establish if such modest falls in viral load (0.3 log₁₀ or 0.5 log₁₀) would have benefits for patients in terms of reducing the risk of HIV transmission or the risk of HIV disease progression.

A review was conducted to identify studies undertaken between 1987 and July 2008 that looked at the link between viral load in the blood and heterosexual HIV transmission. The authors also identified studies investigating the link between viral load and HIV disease progression. Models were then developed to estimate the effect on transmission and disease progression of increases in viral load of 0.3 log₁₀, 0.5 log₁₀ and 1.0 log₁₀.

After looking at four studies, the investigators found that the viral load of individuals who transmitted HIV and those who did not, differed by between 0.6 – 1.0 log₁₀. These studies showed that a 0.3 log₁₀ increase in viral load increased the risk of HIV transmission by between 14% and 31%, that an increase of 0.5 log₁₀ would increase the risk by between 19% and 56% (40% average) and that an increase in viral load of 1 log₁₀ increased the risk of transmission by between 31% and 145% (100% average). Overall, the investigators calculated that each 0.3 log₁₀ increase in viral load increased the risk of HIV transmission by 20%.

Five studies provided sufficient information for the investigators to estimate the effect of increases in viral load on HIV disease progression. An increase in viral load of 0.3 log₁₀ increased the risk of progression to a new AIDS-defining illness or AIDS-related death by between 14% and 36% (25% average), with a 0.5 log₁₀ increase in viral load increasing the risk by between 24% and 67% (44% average) and a 1 log₁₀ increment increasing the risk by between 55% and 179% (average 113%) .

“Small reductions in viral load may have practical applications, even in the antiretroviral therapy era”, write the authors, “treatment of coinfections prevalent among HIV-infected persons in the developing world…may result in small sustained drops in plasma HIV RNA.” They note that mathematical models have shown that treatment of infections and nutritional support can reduce the risk of HIV transmission.

They conclude “small declines in viral load, when introduced on a mass scale, can reduce the likelihood of transmission and slow disease progression. In global efforts to provide antiretroviral therapy, good primary care and systematic control of opportunistic and other coinfections should not be neglected for HIV-infected persons as their treatment may provide a hitherto unanticipated HIV-associated boon.”