Effects of L3T4+ lymphocyte depletion on acute murine cytomegalovirus infection.

We examined the role of T lymphocytes bearing the L3T4 phenotype in acute murine cytomegalovirus (MCMV) infection. In vivo administration of rat IgG2b monoclonal antibody (MAb) GK 1.5 was used to deplete mice of L3T4+ lymphocytes during acute MCMV infection. Unlike the saline-treated controls that resolved their infections, mice receiving the MAb developed persistent and high levels of virus in the salivary gland, lung and spleen. The production of antibody to MCMV was delayed and the titres achieved were markedly less than in the controls. Despite the higher levels of virus replication, there was no increase in mortality seen in animals treated with the MAb. Following intraperitoneal challenge with MCMV, depletion of L3T4+ lymphocytes was protective, increasing the dose of MCMV required to produce death. These data indicate that T lymphocytes of the L3T4 phenotype influence the degree of MCMV replication during acute infection and may contribute to mortality following intraperitoneal virus challenge.