Detection of viral surface antigens on HIV-2ben infected human tumor cell lines by flow cytometry

The human monocytic cell line U-937 clone 2 and two T-cell lines CEM and MOLT-4 clone 8 were infected with HIV-2ben, a recent isolate of HIV-2. Infection and subsequent antigen expression on the cell surface was monitored by flow cytometry using a rabbit-anti-serum against tween-ether-treated HIV-2ben and a fluorescein-isothiocyanate-conjugated IgG against rabbit-IgG. The sensitivity of the three cell lines to infection with HIV-2ben correlated with the percentages of CD4-expressing cells but not with the levels of CD4-expression on the cell. The appearance of viral surface antigens preceded the formation of syncytia and correlated closely with the infecting virus dose. After 1-2 weeks in culture, 20-85% of the cells of each line expressed viral surface antigens. The variation depended on the cell type and cell culture conditions. The MOLT-4 clone 8 and the U-937 clone 2 cells died around 10 or 20 days, respectively, after HIV-2ben infection. Only HIV-2ben infected CEM cells grew permanently. Flow cytometry was an appropriate method to monitor the expression of viral proteins on the cell surface of HIV-infected cell lines. Flow cytometry proved to be more sensitive than determination of RT activity in supernatants of HIV-infected cells and more precise than light microscopy examinations.