Cells nonproductively infected with HIV-1 exhibit an aberrant pattern of viral RNA expression: a molecular model for latency.

U1 and ACH-2 cells are subclones of HIV-1-infected monocyte/macrophage-like and T lymphocyte cell lines, respectively, which express the HIV-1 genome at very low levels. We have examined whether they might provide a model of HIV-1 latency. The patterns of HIV-1-specific RNA expressed in these cells consisted of singly and multiply spliced RNA species, with little or no full-length genomic RNA. Upon stimulation with agents that activate the HIV-1 long terminal repeat in these cells, a marked rise in the amount of small mRNAs, encoding the viral regulatory proteins, preceded the increase in the unspliced RNA. Thus, U1 and ACH-2 cells maintain HIV-1 in a state equivalent to the early phase of a lytic infection and, after stimulation, recapitulate the events of a single cycle infection of highly susceptible target cells.