Studies of human immunodeficiency virus type 1 mucosal viral shedding and transmission in Kenya

If human immunodeficiency virus type 1 (HIV-1) vaccines are to be highly ef fective, it is essential to understand the virologic factors that contribut e to HIV-1 transmission, It is likely that transmission is determined, in p art, by the genotype or phenotype (or both) of infectious virus present in the index case, which in turn will influence the quantity of virus that may be exchanged during sexual contact. Transmission may also depend on the fi tness of the virus for replication in the exposed individual, which may be influenced by whether a virus encounters a target cell that Is susceptible to Infection by that specific variant. Of interest, our data suggest that t he complexity of the virus that is transmitted may be different in female a nd male sexual exposures.