DETECTION OF VIRAL-ANTIGEN FOLLOWING EXPOSURE OF ONE-DAY-OLD CHICKENS TO THE HOLLAND-52 STRAIN OF INFECTIOUS-BRONCHITIS VIRUS

One-day-old specific-pathogen-free single comb White Leghorn chickens were inoculated by eyedrop with either 0.1 ml of phosphate buffered saline containing 10(4.3) EID50 of the Holland 52 strain of infectious bronchitis virus or normal allantoic fluid. Trachea, caecal tonsils and kidneys were removed from randomly selected birds at 0, 3, 5, 7 and 10 days post-inoculation (pi) and the presence or absence of viral antigen was detected utilizing virus isolation (VI), an indirect fluorescent antibody technique (IFA), or a streptavidin-biotin immunohistochemical (IH) technique. The presence of viral antigen as detected by the IH technique was also compared to histopathological changes in serial sections stained with haematoxylin and eosin. Detection of viral antigen occurred more frequently with VI than with IFA or IH. The IFA and IH techniques detected viral antigen with about the same frequency. Viral antigen was detected in the mucosa and submucosa of the trachea as early as 3 days pi, reached maximum levels at 5 days pi, and could still be detected in the mucosa at 10 days pi. In the kidney, viral antigen was not detectable by IFA or IH at 3 days pi, but could be visualized in distal convoluted tubules and collecting tubules at 5 days pi. At 7 days pi, antigen was detectable in the proximal convoluted tubules also. The presence of antigen in the caecal tonsils was sporadic, but it was detected in histiocytic cells and, occasionally, lymphoid cells of that organ.