DETECTION OF CD4(-CELLS HARBORING HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1DNA BY FLOW-CYTOMETRY USING SIMULTANEOUS IMMUNOPHENOTYPING AND PCR-DRIVEN IN-SITU HYBRIDIZATION - EVIDENCE OF EPITOPE MASKING OF THE CD4 CELL-SURFACE MOLECULE IN-VIVO() T)

Human immunodeficiency virus type 1 (HIV-1) infection of T cells and c ells of the monocyte/macrophage lineage requires a specific interactio n between the CD4 antigen expressed on the cell surface and the HIV-1 external envelope glycoprotein (gp120). To study the association betwe en HIV-1 infection and modulation of cell surface expression of the CD 4 molecule in vivo, we examined the CD4(+) T cells harboring proviral DNA obtained from HIV-1-infected individuals who had received no antir etroviral therapy for at least 90 days. Simultaneous immunophenotyping of CD4 cell surface expression and PCR-driven in situ hybridization f or HIV-1 DNA were used to resolve the CD4(+) T cells into distinct pop ulations predicted upon the presence or absence of proviral DNA. Among the HIV-1-infected study subjects, the percentage of CD4(+) T cells h arboring proviral DNA ranged from 17.3 to 55.5%, with a mean of 40.5%. Cell surface fluorescent staining with anti-CD4 antibody directed aga inst a non-gp120 binding site-related epitope (L120) or a conformation -dependent epitope of the gp120 binding site (Leu 3A) demonstrated eit her an equivalent or a 1.5- to 3-fold-lower cell surface staining inte nsity for the HIV-1 DNA-positive subpopulation relative to the HIV-1 D NA-negative subpopulation, respectively. These data suggest that maski ng or alteration of specific epitopes on the CD4 molecule occurs after viral infection.