HIV and other lentiviruses can productively infect nondividing cells, whereas most other retroviruses, such as murine leukemia virus, require cell division for efficient infection. The determinants for this phenotype have been controversial. The Emerman laboratory found that HIV-1 capsid (CA) is involved in facilitating HIV infection of nondividing cells because amino acid changes on CA severely disrupt the cell-cycle independence of HIV. One mutant in the N-terminal domain of CA in particular has lost the cell-cycle independence in all cells tested, including primary macrophages. The defect in this mutant appears to be at a stage past nuclear entry. Using an in situ HIV uncoating assay developed in the Hope Laboratory, we were able to show that the capsid mutation causes premature loss of capsid (uncoating). These data reveal that CA is directly involved at some step in the viral life cycle that is important for infection of nondividing cells.

Viral Capsid Uncoating Rates Are Altered by CA Mutations that Inhibit Replication in Non-dividing Cells. Synchronized infection of HeLa cells was performed with VSV-g pseudotyped, S15-mCherry, GFP-Vpr labeled HIV-1?Env virions. HeLa cells were immunostained for p24CA (Cy-5) at the indicated time post infection and imaged. GFP (+) pucnta were quantified and individually examined for the presence of mCherry and Cy-5 (p24CA) signal. The percentage of the total number of virions that stained for p24CA over time following fusion is shown.