Specific role of each human leukocyte type in viral infections. II. Phytohemagglutinin-treated lymphocytes as host cells for vesicular stomatitis virus replication in vitro.

The mitogenic agent, phytohemagglutinin (PHA), added to human mixed leukocyte cultures and to lymphocyte cultures converted small lymphocytes into lymphoblasts and increased lymphocyte susceptibility to vesicular stomatitis virus (VSV). Maximum virus yields were 30- to 1,000-fold higher in PHA-treated than in control cultures. VSV replicated to peak titers before lymphocytes were morphologically transformed by PHA, and virus titers fell as lymphoblast destruction began. PHA neither induced significant VSV replication in polymorphonuclear leukocyte cultures, nor increased the large virus yields in monocyte cultures. The treatment of PHA with heat, digestive enzymes, rabbit anti-PHA serum and serial dilutions failed to dissociate that portion of the PHA extract responsible for the conversion of lymphocytes into virus-susceptible cells from those components responsible for leukoagglutination or lymphocyte transformation.