Efficiency of viral DNA synthesis during infection of permissive and nonpermissive cells with vif-negative human immunodeficiency virus type 1.

The rate-limiting steps in infection by human immunodeficiency virus type 1 (HIV-1) deficient in the viral infectivity factor, Vif, are unknown. As a measurement of completion of the early stages of the HIV-1 life cycle, the levels of viral DNA were examined by polymerase chain reaction amplification during infection by vif-positive and vif-negative viruses of MT-2 and H9 cells, in which vif is required for HIV-1 replication. Viral DNA was detected within hours of infection by both viruses, but the accumulation of vif-negative virus DNA was impeded in terms of both extent and kinetics. Inefficient viral DNA synthesis correlated with restricted replication of the vif-negative virus. Increasing the input dose of vif-negative virus increased viral DNA levels within 24 h of infection but failed to overcome the block to subsequent DNA synthesis and productive infection. Infection of C8166 cells, in which vif function is dispensable, resulted in efficient DNA synthesis by vif-positive and vif-negative viruses. We conclude that one defect in the replication of vif-negative HIV-1 in nonpermissive cells occurs prior to or during viral DNA synthesis and may reflect processes required for efficient nucleocapsid internalization or activation of reverse transcription.