Immunodepression of lymphocyte response in mouse hepatitis virus 3 infection

Replication of MHV3 in macrophage-depleted T cells and effects of MHV3 infection on mouse lymphocytes were studied in mixed lymphocyte reaction and in mitogen-stimulated cells. In vitro infection of lymphocytes with infectious MHV3 resulted in replication of the virus and marked inhibition of the proliferative response of cells. In mixed lymphocyte cultures, a strong inhibition was obtained when either X-irradiated stimulator cells or responder cells were preinfected with infectious virus. Inactive virus was able, however, to induce a slight inhibition of MLC reaction following treatment of responder cells, but no inhibition was seen when stimulator cells were treated. Since the infection did not visibly affect lymphocyte viability, MHV3 appeared to replicate in lymphocytes without displaying any cytopathic effects comparable to those observed in infected macrophages.