Characterization of a Non-Pathogenic MHV3 Variant Derived from a Persistently Infected Lymphoid Cell Line
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Mouse hepatitis virus type 3 infection leads to various types of evolution according to strain, age and immune status of animals-1, 2. Three types of viral sensitivity were observed: resistance, full susceptibility and semisusceptibility. The latter is characterized by a chronic disease with occurrence of paralysis, immunodepression, and viral persistency since MHV3 can be recovered during the first three months postinfection in most animals from brain, liver, spleen and lymph nodes1. During the first four days of infection, virus was recovered from the liver of resistant as well as susceptible strain mice. In resistant A/J strain mice, viral titers were consistently low whereas titers greater than 104 were always found in susceptible C57BL/6 animals. In the resistant mouse strain, virus was cleared from liver, brain and serum within seven days. In contrast, virus continued to replicate until death in susceptible animals. Immunosuppressive treatment, however, can abogate the resistance displayed by adult A/J mice, leading to an acute disease and to death. Protection of susceptible newborn mice against MHV3 infection requires the transfer of several cell populations originating from syngenic adult donors: adherent spleen cells, T lymphocytes and a third population present in the non-adherent spleen cell fraction as well as in peritoneal exudate and in bone marrow cells2, 3. Resistance to the acute disease was also correlated with viral replication in hepatocytes4, in embryonic fibroblasts5 and in peritoneal exudate cells2, 6, 7. Recent work suggested that at least two complementary mechanisms were required to confer resistance to MHV3: resistance genes operating at the macrophage level and cells capable to elicit an efficient immune response8.
KeywordsVirus Titer Peritoneal Exudate Susceptible Mouse Mouse Hepatitis Virus Lymphoid Cell Line
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