Abstract:

The effects of age at infection, route of infection and strain of virus on reovirus-speci®c IgA and IgG
responses of chickens were investigated using anti-IgA and -IgG monoclonal antibodies. Three groups of
SPF chickens were infected with a trypsin-resistant avian reovirus (strain R2) at 1 day old (DO), 7 days
old, or 3 weeks old by oral or subcutaneous routes. Virus titres in the gut declined with increasing age of
chick at infection. IgA was not detected in the intestinal contents of chicks infected at DO. Those infected
orally at 7 days and 3 weeks old showed a substantial rise in intestinal IgA. In the subcutaneously-infected
chicks, only those infected at 3 weeks old showed an intestinal IgA response. There were very similar
reovirus-speci®c IgG responses in the sera of the orally and subcutaneously infected chicks, in all
age-groups. In a second experiment a trypsin-sensitive avian reovirus (TR1) was used to infect DO and
7-day old chicks by oral and subcutaneous routes. No intestinal replication was detected in either age
group, nor reovirus-speci®c intestinal IgA. However, substantial IgG responses were detected in sera of all
TR1-infected chicks. These results indicate that the age of the chick, the route of infection and trypsin-sen- sitivity of the virus have important bearing on the local intestinal responses after reovirus infection.