Low-virulent mouse hepatitis viruses exhibiting various tropisms in macrophages, T and B cell subpopulations, and thymic stromal cells.

Functional or cellular immunodeficiencies have been reported to result from various pathogenic mouse hepatitis virus (MHV) strains. Moreover, low-virulent MHV strains can reduce the ability of mice to seroconvert to other antigens or viruses. To determine the importance of low-virulent MHV strain tropism in immune cells, as a mechanism involved in the induction of immunodeficiencies, peritoneal exudate cells, T and B cell subpopulations, and thymic stromal cells were infected with low-virulent MHV-D, MHV-K, and MHV-N and pathogenic MHV-3 viral strains. Cell viability, percentages of viral protein-expressing cells, and virus titers have been analyzed. On the basis of our findings, low-virulent MHV viral strains exhibit various tropisms in macrophages, B lymphocyte subpopulations, or thymic stromal cells when compared with the more virulent MHV-3 serotype. All MHV strains tested have replicated in peritoneal exudate cells of C57BL/6 or A/J mice. Low-virulent MHV-N and pathogenic MHV-3 strains showed higher tropism for peritoneal exudate cells than low-virulent MHV-K and MHV-D strains. Likewise, MHV-N and -3 serotypes expressed higher tropism than MHV-D or -K serotypes for thymic stromal cells and B lymphoid cells. No tropism for T lymphocytes, however, was detected with MHV except when in contact with previously infected thymic stromal cells. These results raise the problem of immunologic disorders resulting from viral replication in immune cells in mouse colonies subclinically infected with low-virulent MHV strains.