Virus-specific immunity in neonatal and adult mouse rotavirus infection.

Mouse rotavirus (epizootic diarrhea of infant mice) was used as a model to study the role of virus-specific immunity in infection and diarrheal disease. The distribution of viral antigen in intestinal tissues was determined by immunofluorescent staining with anti-simian rotavirus (SA-11) serum. The location and proportion of antigen-positive cells appeared to vary as a function of time postinfection and age of the animal at the time of infection. In animals infected at 1 and 7 days of age, antigen-positive cells (5 to 25%) were first detected (1 day postinfection) in the proximal segment of the small intestine, and infection progressed to the middle and distal segments. At 10 days postinfection, virus-infected cells were no longer observed in the proximal segment. In animals infected at 21 days of age (disease-free), a significantly lower proportion of cells were antigen positive (2 to 5%), and they were restricted to the middle and distal segments of the small intestine. Infection, defined according to the presence of virus and viral antigens in intestinal tissues and by seroconversion in the immunoglobulin M (IgM) isotype as determined by enzyme-linked immunosorbent assay with SA-11 antigen, was observed for all age groups (neonatal to adult), even in the presence of virus-specific serum or intestinal immunoglobulins. On the other hand, diarrheal disease was not detected in neonatal mice (1 to 3 days old) positive for passively acquired virus-specific intestinal IgG. The presence of virus-specific IgA in the intestinal tract at the time of infection did not protect from subsequent diarrheal disease. Virus-specific, cell-mediated immunity, determined by a delayed-type hypersensitivity response, did not develop in neonatal mice infected at 5 and 12 days of age. Reinfection of adult mice was associated with suppression of virus-specific delayed-type hypersensitivity and a significant decrease in the titers of the virus-specific serum IgG and IgA.