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MHRP study indicates increase in HIV subtypes in Kenya

August 19, 2015
Increased viral complexity could complicate picture for HIV vaccine researchers.

Recent analysis of data from Kenya shows a rise in both the number and complexity of inter-subtype recombinants of HIV-1, which could pose a significant challenge for vaccine development.

In a new paper published today in PLOS One, researchers led by MHRP analyzed the molecular epidemiology of HIV-1 subtypes within a tea plantation community cohort in Kenya.

In June 2003, MHRP initiated an HIV and Malaria cohort study among plantation workers and adult dependents in Kericho. The study followed 2,400 seronegative individuals every six month for a period of three years. At the end of the study in December 2006, 63 incident infections were recorded.

HIV-1 strains from 58 of those participants were full-genome characterized and the data compared to two previous studies—41 prevalent infections from a 1999-2000 blood bank survey, and 21 infections from 2006 in a higher-risk cohort containing a mix of indecent and prevalent infections. The goal of each of the studies was to inform development of an HIV-1 vaccine, so a comparative analysis was performed looking at candidate vaccines considered for use in Kenya, along with the strains observed across the studies.

Compared to the older studies, the tea plantation cohort contained a higher proportion of recombinant incident infections (56.9% compared to 38.8% in the blood bank cohort and 41.7% in the higher-risk cohort). In each of the studies, subtypes A1 and D were the most common parent subtypes for the recombinants. Researchers then analyzed the infections with recombinants containing both of these subtypes and found a significant increase from the blood bank study (19.5%) to the higher-risk cohort (33.3%), and even higher in the community cohort (48.2%).

According to the Kenya AIDS Response Progress Report, overall rates of HIV-1 infection among men and women ages 15 to 49 are trending down (from 7.6% in 2007 to 5.6% in 2012). However, increases in diversity among viral subtypes—driven by high rates of genetic mutation and recombination—could continue to complicate the picture for vaccine researchers.

MHRP Director Col Nelson Michael comment that “the findings of the present study provide evidence of increased molecular complexity of the HIV-1 epidemic in Kenya, which could impact the selection of immunogens for future HIV vaccine development.”