Immunopathology of mouse hepatitis virus type 3 infection. Role of humoral and cell-mediated immunity in resistance mechanisms.

Humoral and cell-mediated immune responses were studied in resistant and susceptible strains of mice infected with mouse hepatitis virus type III (MHV 3). Virus was maintained by regular passages in susceptible DBA/2 mice and assayed in DBA/2 mice by LD-50 determination. Normal resistant A strain mice were able to clear the virus from liver, brain, and serum within 7 days after infection. No neutralizing antibody was found. Transfer of serum from immunized A strain mice was not effective in protecting susceptible DBA/2 mice against challenge with virus. In A strain animals resistance to MHV-3 developed rapidly during the 3rd week of life. During the period of susceptibility, newborns were protected neither by transplacental passages of anti-MHV-3 antibodies nor by injection of "educated" thymus cells.