By virtue of the presence of CD4 on the cell surface , PLB-985 cells were chronically infected with HIV-1 strain IIIB .
by virtue of the presence of cd4 on the cell surface , plb-985 cells were chronically infected with hiv-1 strain iiib .
O O O O O O B-protein_molecule O O B-cell_component I-cell_component O B-cell_line I-cell_line O O O O B-virus O O O