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A monoclonal antibody to the gp120-CD4 complex has differential effect on HIV-induced syncytium formation and viral
K Konopka1, E Pretzer, F Celada
1Department of Microbiology, University of the Pacific, School of Dentistry, San Francisco, CA 94115.
Insights
A monoclonal antibody targeting CD4 domains D1/D2 showed limited inhibition of HIV-1 infectivity in most T cell lines. However, it significantly inhibited infectivity in H9 cells, suggesting cell-specific differences in antibody efficacy against HIV-1 fusion.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- A murine monoclonal antibody (MAb F-91-55) targets the CD4-gp120 complex and inhibits syncytium formation.
- Its binding site is within the first two domains (D1/D2) of CD4, without blocking CD4-gp120 interaction.
Purpose of the Study:
- To investigate the effect of MAb F-91-55 on HIV-1 infectivity in CD4+ T cell lines (A3.01, Sup-T1, H9).
- To examine the antibody's impact on syncytium formation between these cell lines and chronically infected H9 cells.
Main Methods:
- Testing MAb F-91-55's inhibition of HIV-1 infectivity in A3.01, Sup-T1, and H9 cells.
- Assessing the antibody's effect on syncytium formation in cell-cell fusion assays.
Main Results:
- MAb F-91-55 had limited effect on HIV-1 infectivity in A3.01 and Sup-T1 cells, but significantly inhibited it in H9 cells.
- The antibody inhibited syncytium formation in all tested cell lines, with greater effect in H9 cells.
- Syncytium formation efficiency varied based on incubation medium and cell line.
Conclusions:
- Cellular systems exhibit differential susceptibility to inhibitory antibodies like MAb F-91-55.
- Discrepancies in blocking viral entry versus syncytium formation suggest distinct gp120/gp41-CD4 interaction mechanisms in virus-cell vs. cell-cell fusion.
Abstract:
A murine monoclonal antibody (MAb F-91-55) raised against the complex of soluble CD4 and human immunodeficiency virus type 1 (HIV-1) gp120 had previously been found to inhibit syncytium formation without inhibiting the interaction of CD4 with gp120, and its binding site was localized within the first two domains (D1/D2) of CD4. We investigated whether this antibody inhibited the infectivity of HIV-1 in the CD4+ T cell lines A3.01, Sup-T1 and H9. We also examined the effect of the antibody on syncytium formation between these cells and chronically infected H9 cells. Syncytium formation was found to depend critically on the incubation medium used. The effect of the MAb on HIV-1 infectivity was very limited with A3.01 and Sup-T1 cells, although it inhibited syncytium formation between A3.01 or Sup-T1 and chronically infected H9 cells. In contrast, the MAb inhibited significantly the infectivity of HIV-1 in H9 cells, but it also inhibited syncytium formation between H9 and chronically infected H9 cells to a greater extent than in the case of the other cell lines. Our results indicate that cellular systems used for syncytium assays differ in their susceptibility to inhibitory antibodies. In the A3.01 and Sup-T1 cell systems, the differences in the ability of the MAb to block viral entry or syncytium formation raise the possibility that the mechanisms of interaction of gp120/gp41 with cell membrane CD4 may be different in cell-cell and virus-cell membrane fusion.
