Human immunodeficiency virus type 1 NL4-3 replication in four T-cell lines: rate and efficiency of entry, a major determinant of permissiveness.

Single-cycle infections have been used to study the human immunodeficiency virus type 1 (HIV-1) life cycle in CD4+ T-cell lines that differ in their permissiveness for infection. In single-cycle infections of highly permissive C8166 cells, 50% of the infectious units escaped being blocked by a monoclonal antibody against the virus binding site on CD4 (leu3a) within 30 min. In contrast, 50% of the infectious units for three less permissive cell lines (H9, A3.01, and Jurkat) required 4 h to escape the leu3a block. Entry was also more efficient in the highly permissive cells, with NL4-3 stocks having three times more infectious units for C8166 cells than for H9, A3.01, or Jurkat cells. Postentry steps up through reverse transcription required approximately 3.5 h in each of the cell lines. The times lapsing between reverse transcription and the expression of reverse transcripts ranged from 17 to 25 h in the different cell lines. Virus production per cell was also similar in the different cell lines (within 1.5-fold of each other). These results indicate that a major determinant of the permissiveness of growing T cells for HIV-1 is the rate and efficiency of virus entry.