Reduced frequency of HIV superinfection in a high-risk cohort in Zambia.

Rates of HIV-1 superinfection， re-infection with a genetically distinct virus despite HIV-1 specific immune responses， vary in different risk populations. We previously found the rates of superinfection were similar to primary HIV infection (PHI) in a Zambian heterosexual transmission cohort. Here， we conduct a similar analysis of 47 HIV-positive Zambians from an acute infection cohort with more frequent follow-up， all infected by non-spousal partners. We identified only one case of superinfection in the first two years， significantly fewer than in our previous study， which was likely due to increased counseling during acute infection and an overall population-wide decline in factors associated with HIV transmission. The predominant virus detected after superinfection was a recombinant of the transmitted founder (TF) and the superinfecting strain. The superinfected individual mounted a neutralizing antibody response to the primary TF virus， which remained TF-specific over time and even after superinfection， did not neutralize the superinfecting variant.