Abstract
1. We have demonstrated previously (Harrowe et al., 1990), using a lymphoblastoid cell line that constitutively expresses the substance P receptor (SPR) (Payan et al., 1984, 1986), that this receptor may facilitate measles virus (MV) fusion with these cells. In order to test this hypothesis further, a stable cell line transfected with SPR cDNA has been established, and various stages of MV infection in SPR positive and negative cells compared. 2. Jurkat cells, a human T-lymphoblastoid cell line, were transfected with a cDNA clone encoding the SPR. Cells transfected with only the plasmid were used as controls. Jurkat cells and Jurkat vector control cells (J-vo) failed to demonstrate any detectable 125I-SP binding, whereas a clonally selected population of cells transfected with SPR cDNA (J-SPR) expressed about 50,000 receptors/cell (Sudduth-Klinger et al., 1992). 3. Using the J-vo- and J-SPR-transfected cell lines, the following experiments were conducted to investigate the effect of SPR expression on MV infection. To determine if MV would preferentially attach to J-SPR as compared to J-vo, we absorbed virus to cells at 37 degrees C for various times and measured bound MV using a fluorescence activated cell sorter (FACS). Using this approach, we found that MV bound to a greater degree to J-SPR compared with J-vo. In addition to equilibrium being reached faster for J-SPR, the total amount of bound MV was higher on J-SPR. The effect was greater at lower MOIs, suggesting that there existed multiple binding sites for MV on these cells and that the affinity is higher for those cells expressing the SPR. 4. Since binding does not necessitate a successful viral infection, we needed to know if this difference in binding reflected a difference in infection. This was demonstrated by showing an approximate twofold increase in infected cells after a 2-hr binding period with J-SPR as compared to J-vo at an MOI of 1 in an infectious cell-center assay. Moreover, when both cells types were subjected to continuous infection in culture, J-SPR-infected cells produced a seven- to ninefold increase in measles viral titer in 24 hr as compared with J-vo. The observed increase in viral titer may have resulted in more of the J-SPR cells binding virus, as indicated by our binding and infectious cell-center data, or alternatively, the virus might have entered the J-SPR cells faster and begun replication before the J-vo-infected cells.(ABSTRACT TRUNCATED AT 400 WORDS)