Quantitative comparison of HTLV-1 and HIV-1 cell-to-cell infection with new replication dependent vectors

We have developed an efficient method to quantify cell-to-cell infection with single-cycle,replication dependent reporter vectors. this system was used to examine the mechanisms of infection with htlv-1 and hiv-1 vectors in lymphocyte cell lines. effector cells transfected with reporter vector,packaging vector,and env expression plasmid produced virus-like particles that transduced reporter gene activity into cocultured target cells with zero background. reporter gene expression was detected exclusively in target cells and required an env-expression plasmid and a viral packaging vector,which provided essential structural and enzymatic proteins for virus replication. cell-cell fusion did not contribute to infection,as reporter protein was rarely detected in syncytia. coculture of transfected jurkat t cells and target raji/cd4 b cells enhanced hiv-1 infection two fold and htlv-1 infection ten thousand fold in comparison with cell-free infection of raji/cd4 cells. agents that interfere with actin and tubulin polymerization strongly inhibited htlv-1 and modestly decreased hiv-1 cell-tocell infection,an indication that cytoskeletal remodeling was more important for htlv-1 transmission. time course studies showed that htlv-1 transmission occurred very rapidly after cell mixing,whereas slower kinetics of hiv-1 coculture infection implies a different mechanism of infectious transmission. htlv-1 tax was demonstrated to play an important role in altering cell-cell interactions that enhance virus infection and replication. interestingly,superantigen-induced synapses between jurkat cells and raji/cd4 cells did not enhance infection for either htlv-1 or hiv-1. in general,the dependence on cell-to-cell infection was determined by the virus,the effector and target cell types,and by the nature of the cell-cell nteraction.