The molecular and cellular events necessary for the assembly and release of human T-cell leukemia virus type 1 (HTLV-1) in infected cells and for the entry and replication of virions in target cells are not well defined. Recent work from other laboratories suggests that the directed transmission of HTLV-1 between T lymphocytes is coordinated with development of an intercellular synapse, and occurs at the cell-cell interface. This scenario predicts that various steps in the virus infectious cycle would be integrated with and enhanced by formation of specific cell-cell contacts. We are examining the molecular mechanisms underlying the individual steps in the HTLV-1 infectious cycle with the long-term objective of understanding the concerted production, transfer, and replication of the virus in the context of cell to cell transmission.

To this end, we are developing in vitro methods to analyze cellular and viral events when HTLV-1-infected cells engage uninfected target cells. The figure shows an example of preliminary studies in which Jurkat T-cells were cotransfected with an HTLV-1 provirus clone in combination with a Tax-eYFP expression plasmid and subsequently incubated with an equal number of untransfected Jurkat cells for 1 hr to allow formation of stable cell-cell contacts. Cells were then collected, fixed, and stained with fluorescent-labeled antibodies that recognize HTLV-1 Gag matrix protein (red) and a-tubulin (blue); nuclear-localized Tax-eYFP is shown in green. In individual transfected cells, HTLV-1 Gag is randomly dispersed, but in conjugated cells, Gag is concentrated at the cell-cell interface.