Serum antibody responses of neonatal and young adult pigs to transmissible gastroenteritis coronavirus.

Serum titers of virus-neutralizing (VN) antibody were 10 to 16 times higher in neonatal pigs than in young adult pigs, after single oral doses of virulent transmissible gastroenteritis virus (TGEV). To determine the reason for this higher response, sera from neonatal and young adult pigs, 18 to 21 days after exposure to TGEV, were collected and assayed for VN antibody by plaque reduction. In addition, sera of VN-positive and VN-negative neonatal pigs were analyzed for immunoglobulin classes by radial immunodiffusion technique. The competence of neonatal pigs to produce VN antibody with increased IgG levels was demonstrated. The higher antibody response seen in neonatal pigs, when compared to sera of young adult pigs, may be attributed to the increased replication of TGEV in the intestinal tracts of neonatal pigs or to the lack of other immunogens that may interfere or compete with the production of specific antibody.