Enterotropic coronavirus (mouse hepatitis virus) in mice: influence of host age and strain on infection and disease.

The course of enterotropic mouse hepatitis virus (MHV) infection was examined in genetically susceptible (BALB) and resistant (SJL) mice of different ages at inoculation (1, 3, and 12 weeks) and at sequential intervals (1, 2, 3, 5, 10, 20, and 30 days) after oral inoculation with the Y strain of MHV (MHV-Y). Virus was quantified in stomach, upper and lower segments of small intestine, cecum, upper and lower segments of colon, Peyer's patches, mesenteric lymph node, and feces, and tissues were examined microscopically. An infant mouse bioassay was used to quantify virus in all tissues of 3-week-old BALB mice and ascending colons of other mouse groups. MHV-specific serum IgG antibody titers were measured with an enzyme immunoassay, using MHV-S-infected 17 Cl 1 cells as antigen. Lesions were first detectable at 2 days and were most severe in 1-week-old mice and more severe in BALB mice, compared with SJL mice of the same age. Additional BALB mice inoculated at the age of 24 hours developed severe necrotizing enterocolitis, whereas SJL mice inoculated at the age of 24 hours developed lesions equivalent to those in 1-week-old BALB mice. Virus was first detectable at 2 days and virus titers were highest at 2, 3, and 5 days, then diminished on days 10, 20, and 30. Low titers of virus were found in a few mice of different ages and genotypes through day 30. Lesions were most severe and virus titers highest in the ascending colon.(ABSTRACT TRUNCATED AT 250 WORDS)