Replication of Herpes Simplex Virus in Cultures of Phytohemagglutinin-Stimulated Human Lymphocytes

Summary

Primary cultures of normal human peripheral blood lymphocytes transformed in vitro by pyhtohemagglutinin (PHA) can support replication of human viruses. To establish a model for the identification of unknown viruses in this cell system, we studied the replication of herpes simplex virus (HSV) in PHA-stimulated lymphocytes both by infectivity titer and electron microscopic examination. Our studies documented the replication of HSV, of low infectivity, in cultures of PHA-stimulated normal lymphocytes. Maximum infectivity liters were reached in 48 hours. Unstimulated lymphocytes showed only a slight increase in viral infectivity liters. New virus was first observed by electron microscopy in the infected cultures 24 hours after inoculation. At 48 hours nearly all viable cells examined contained virus in various stages of proliferation. No evidence of replication was found in the nontransformed lymphocytes. Some morphologic alterations observed in the blastoid cells infected with HSV were not characteristic of PHA transformation alone. These included: complex nuclear membrane reduplication (blebs), increased cytoplasmic rough endoplasmic reticulum, and intracytoplasmic membranes resembling viral envelopes. Cultures of PHA-stimulated normal human lymphoctyes may be useful for identification of unknown human viruses and may prove especially valuable for the isolation of possible human lymphotrophic viruses.