MURINE CYTOMEGALOVIRUS INFECTION OF PHAGOCYTIC LEUKOCYTES

Cytomegalovirus (CMV) infections have been associated with altered host defense and increased susceptibility to secondary infection. In previous experiments, we observed impaired migratory and chemotactic activity of neutrophils harvested from mice during sublethal murine CMV (MCMV) infection. To investigate further the effects of CMV infection upon phagocytic leukocytes, we incubated murine leukocyte suspensions (95% neutrophils) in vitro with MCMV derived either from tissue culture passage or salivary gland homogenate. Neutrophils incubated with salivary gland MCMV had depressed chemotactic activity at 2 and 4 h. For example, at 4 h the mean chemotactic index of neutrophils incubated with MCMV was 0.92 vs 2.56 in controls (p<0.01). Phagocytic activity at 4 h was also reduced (mean of 1.53 latex particles/cell in MCMV-incubated vs 2.39 in controls, p<0.01). In contrast, tissue culture-passed MCMV did not alter leukocyte function. Adherence of MCMV to phagocytic leukocytes was comparable to adherence of virus to mouse embryo fibroblast cells (2 to 3 log plaque forming units of MCMV/106 cells). Transmission electron microscopy at 4 h demonstrated occasional intracytoplasmic virions. These results indicate that impaired chemotactic and phagocytic activity of phagocytic leukocytes occurs after in vitro incubation with salivary gland-derived MCMV but not with tissue culture-passed virus. These differences may be attributable to altered virulence of MCMV or to the presence of soluble factors in salivary gland MCMV pools