Regulation of HIV Production by Blood Mononuclear Cells from HIV-Infected Donors: II. HIV-1 Production Depends on T Cell-Monocyte Interaction

Cell-cell interactions induced between T cells and monocytes by certain soluble anti-CD3 monoclonal antibodies (MAbs) were previously shown to be required for high-level production of HIV-1 by peripheral blood mononuclear cells (PBMCs) from infected donors. Staphylococcal enterotoxin or superantigen (SAg) is another mitogen inducing monocytes-T cell interactions that exhibit potent induction of HIV-1 production. Antibodies to several adhesion molecules were used to test the requirements for T cell- and monocyte-associated adhesion molecules in HIV-1 production following activation with anti-CD3 or SAg. Blocking of either CD2-LFA-3, or CD18-ICAM-1, inhibited anti-CD3-or SAg-induced HIV-1 production by more than 90% without inhibiting CD4⁺ T cell proliferation. Inhibition of HIV production was observed when either the T cell or monocyte coreceptor was bound by MAbs to these adhesion molecules. Blocking of CD28-B7 interactions by soluble CTLA-4 fusion protein, a CD28 homolog, inhibited both HIV-1 production and CD4⁺ T cell proliferation. Fc binding was not required for HIV-1 inhibition by MAbs to CD2 and CD18, because Fab or F(ab')₂ fragments of these MAbs inhibited HIV-1 production by more than 80%. A chimeric single-chain MAb to CD2 was produced, containing heavy and light chain variable regions from MAb 35.1 to CD2 linked to the constant regions of human IgG₁ (CD2 SFv-Ig). This humanized CD2 SFv-Ig inhibited HIV-1 production by 30% to >98%. These results thus indicate that simultaneous engagement of multiple adhesion pathways between T cells and monocytes are required for HIV production by patients PBMCs and may have implications for therapy of HIV infections.