Selective Stimulation of CD4 + Versus CD8 + T-Cell Subsets in Symptomatic and Asymptomatic HIV-1-Infected Individuals

To analyze the proliferative capacity of CD4⁺ or CD8⁺ T-cell subsets of individuals infected with human immunodeficiency virus type 1 (HIV-1) and to optimize the in vitro conditions for virus replication, CD4⁺ or CD8⁺ cells of HIV-1-infected patients were selectively activated inside the whole peripheral blood mononuclear cell (PMNC) population by dual antibody stimulation. To do so PMNC of HIV-1-infected individuals were stimulated with the per se nonmitogenic anti-CD3 antibody fragment BMA030 F(ab)₂ crosslinked through goat antimouse antibodies with an anti-CD4 or an anti-CD8 antibody, which lead to selective proliferation of either the CD4⁺ or the CD8⁺ T-cell subset. In the presence of monocyte supernatant and recombinant interleukin-2 (rIL2) CD4+ cells of HIV-1 patients responded normally upon such stimulation as their proliferation correlated (r = 0.9) to the percentage CD4⁺ cells present in the PMNC population. Selective stimulation and proliferation of CD8+ cells could, however, only partially be elicited by dual antibody stimulation, even in the presence of rIL-2 and monocyte supernatant. Their proliferative response did not correspond (r = 0.1) to the percentage CD8⁺ cells present in the PMNC culture. A positive correlation (r = 0.7) was detected only between percentage CD8⁺ HLA-DR^- cells and proliferation. This confirmed previous studies showing that the defective in vitro proliferative response of peripheral blood lymphocytes of HIV-infected individuals to mitogens, which is usually interpreted being due to a CD4 cell defect, is actually due to a failure of CD8⁺DR⁺ cells to proliferate. The selective activation of CD4⁺ cells by dual antibody stimulation proved to be advantageous to measure virus replication as the optimized stimulation of CD4⁺ cells lead to enhanced virus replication in vitro and circumvented the suppressive effect of CD8⁺ cells without cumbersome purification protocols. Indeed, in 13 out of 19 cell cultures from HIV-1-infected patients (7 with AZT treatment) virus replication was measured as elevated p24 HIV-1 protein levels. In cultures where both CD4⁺ and CD8⁺ cells were stimulated, virus replication was reduced compared with cultures where CD4⁺ cells alone were selectively stimulated, which emphasizes the suppressive role of CD8⁺ cells on virus replication.