Re‐excretion of infectious bronchitis virus in chickens induced by cyclosporin

Abstract
Following inoculation of day‐old chicks with Moroccan strain ‘G’ of infectious bronchitis virus (IBV) which has a predilection for the gut, virus was recovered from the trachea up to day 7 and from the cloaca up to day 35. After this no virus could be detected, even following the natural stress of re‐housing with unfamiliar birds at 9 weeks. When the birds were 12.5 weeks old, they were injected with cyclosporin, a selective T‐cell suppressor. Four of the five birds re‐excreted virus very erratically, as did two of five contacts. This was accompanied by the appearance of IBV‐specific IgM in the sera of both groups. The results suggest that in long‐term infections with IBV, virus persistence is controlled by T lymphocytes.