This initial research, part of a long-term HIV study conducted in Uganda, is essential to understanding why there are differences in the way HIV infects males and females.

According to the Johns Hopkins team that led the study, this initial research is essential to understanding why these differences occur, as well as for future development of a vaccine or other preventive methods that could stop sexual transmission of HIV-1.

Long-Term Study in Uganda

The couples in the study come from the Rakai Cohort, a Uganda-based population in a long-term study of HIV infection.

The researchers tested each couple's viral RNA to determine which variants, or kinds of HIV-1 strain, were present in each man and woman.

Variants Distinguished

Variants of HIV-1 can be distinguished by differences in the gene (gp160) for their protein envelope.

The findings showed that only a subset of HIV-1 variants in the initially infected partner was transmitted to the newly infected partner, and the predominant variant in males was not the kind that infected their female partners.

Also, women infected by men had a greater number of variants than men infected by women.