STUDIES ON THE LOCAL IMMUNITY OF INTESTINAL TRACT OF CHICKENS AFTER ORAL ADMINISTRATION OF NEWCASTLE DISEASE VIRUS

Abstract

An enterotropic avirulent Newcastle disease virus (NDV-Ishii) which was administered by the oral route in a dose of about 10⁵-10⁸ TCD₅₀/chick caused alimentary tract infection in 4 week old chickens, which excreted NDV-Ishii in feces from 3 to 7 days after the first feeding. Indirect fluorescent antibody microphotograph of sections of the small intestine revealed that a sort of surface infection was established by the oral administration of enterotropic NDV. But the virus was scarcely recovered from feces after the second feeding 4 to 6 weeks later and the neutralizing activity of fecal extracts, probably coproantibody, was demonstrated a few weeks after the virus feeding. Bursectomy plus γ ray irradiation (650 r) after hatching exerted a profound influence on humoral immunity, namely, suppression of HI antibody production in serum, and at the same time the development of local immunity of the alimentary tract was disturbed. Those chickens excreted the virus even after its second administration. On the other hand, thymectomy plus γ ray irradiation or γ ray irradiation alone had no suppressive effect on establish-ment of the alimentary tract resistance to reinfection. Therefore it is concluded that the local immunity of the alimentary tract of chickens against refeeding of the enterotropic NDV depends largely on humoral immunity governed by the bursa-dependent lymphoid system, and probably on IgA antibody which is produced locally by lymphoid cells of the lamina propria.