MULTIPLE EFFECTS OF MUTATIONS IN HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INTEGRASE ON VIRAL REPLICATION

The integration of a DNA copy of the human immunodeficiency virus type 1 (HIV-1) genome into a chromosome of an infected cell is a pivotal s tep in virus replication. Integration requires the activity of the vir us-encoded integrase, which enters the cell as a component of the viri on. Results of numerous mutagenesis studies have identified amino acid residues and protein domains of HIV-1 integrase critical for in vitro activity, but only a few of these mutants have been studied for their effects on HIV replication. We have introduced site-directed changes into an infectious DNA clone of HIV-1 and show that integrase mutation s can affect virus replication at a variety of steps. We identified mu tations that altered virion morphology, levels of particle-associated integrase and reverse transcriptase, and viral DNA synthesis. One repl ication-defective mutant virus which had normal morphology and protein composition displayed increased levels of circular viral DNA followin g infection of a T-cell line. This virus also had a significant titer in a CD4-positive indicator cell assay, which requires the viral Tat p rotein. Although unintegrated viral DNA can serve as a template for Ta t expression in infected indicator cells, this level of expression is insufficient to support a spreading viral infection in CD4-positive ly mphocytes.