Interaction of alphaviruses with human peripheral leukocytes: in vitro replication of Venezuelan equine encephalomyelitis virus in monocyte cultures.

Human peripheral blood leukocytes (PBL) were examined for their ability to support growth of several group A arboviruses in vitro. Cells were refractory to infection with eastern (EEE) and western (WEE) equine encephalitis viruses, whereas Venezuelan equine encephalomyelitis (VEE) virus was shown to infect and replicate to a substantially high titer. When PBL were fractionated into purified subpopulations, only the monocytes were susceptible to predictive VEE virus infection. Lymphocytes treated 24 h before virus inoculation with phytohemagglutinin (10 microgram/ml) were capable of propagating significant amounts of VEE virus. A monocytic cell line, J-111, was also susceptible to infection with VEE, EEE, and WEE viruses, whereas a lymphocytic cell line, Raji, was refractory. Additional information on the participation of PBL during human infection with these viruses may add considerably to our understanding of their differing pathogenicities and clinical pictures.