Intestinal immune response of feeder pigs to infection with transmissible gastroenteritis virus.

Five feeder pigs 4 to 6 months old were orally inoculated with transmissible gastroenteritis virus. Diagnosis of transmissible gastroenteritis was made on the basis of clinical signs and examination of intestinal mucosa by the fluorescent antibody technique. Immunoglobulins were extracted from intestinal fluid of infected feeder pigs. Virus-binding and neutralizing antibodies were detected in intestinal extracts between 7 and 56 days after infection. The concentration of binding antibodies reached a peak at 21 days after infection and was on the decline at the end of the experiment on the 56th postinfection day. In contrast, neutralizing intestinal antibody concentration was increasing on day 56. In both systems, the predominant immunoglobulin was of the IgA class. Examination of blood serums of the pigs by the plaque-reduction technique showed progressive antibody increases ranging in titer from 1:8 on day 7 to 1:256 on day 56 after infection. An analysis of the protein profiles from these serums showed a significant increase in the concentration of gamma-globulins and a decrease in the albumin fraction.