Cellular immunity to human immunodeficiency virus type 1 (HIV-1) clades: Relevance to HIV-1 vaccine trials in Uganda

The first prophylactic human immunodeficiency virus type 1 (HIV-1) vaccine trial in Africa, with a clade B immunogen, is currently under way in Uganda , in a region where clades A and D are endemic. The use of a B clade vaccin e is based on anticipated cross-recognition of endemic strains of HIV-1 in Uganda, but, in fact, little is known about the cytotoxic T lymphocyte (CTL ) responses in that region. Seventeen HIV-1-infected volunteers from Kampal a, Uganda, were studied to determine the immune responses elicited by natur al infection with local HIV-1 strains. Despite the presence of broad cross- clade recognition, the CTL responses to the infecting viral clade were high est in most people. Recognition of nonendemic clade B antigens was similar to that of the coendemic local clade, and, in some instances, cross-recogni tion of clade B was greater. Nevertheless, the degree of cross-clade cellul ar responses we observed lends justification to the use of clade B-based im munogens in the current phase 1 vaccine trial in Uganda.