INFECTIOUS-BRONCHITIS VIRUS-ANTIBODIES IN TEARS AND THEIR RELATIONSHIP TO IMMUNITY

Antibodies to infectious bronchitis virus (IBV) in chicken rears were investigated to determine if they could be used as an indicator of pro tective immunity. Antibody production in tears and serum was measured by enzyme-linked immunosorbent assay (ELISA) in specific-pathogen-free (SPF) white leghorn and broiler chickens vaccinated with a live atten uated vaccine containing the Massachusetts (Mass) Connaught strain of IBV. The effect of virulent infectious bursal disease virus (IBDV) inf ection on antibody production in tears was also evaluated. Immunity wa s assessed by challenging the chickens with Mass 41 and performing tra cheal swabbings 5 days later. In addition, tears were also evaluated f or virus-neutralizing (VN) antibodies to IBV. Following eyedrop vaccin ation, anti-IBV antibodies were consistently detected by ELISA in tear s prior to and in higher concentrations than in the sera of SPF white leghorn and broiler chickens. Maternal IBV antibodies were present in the tear secretions of broiler chickens but in lower concentrations th an in sera. Infection of SPF chicks with a virulent and immunosuppress ive strain of IBDV at 1 day of age greatly reduced IBV ELISA antibody production in rears as well as serum compared with infection of chicke ns with IBDV at 14 days of age. IBV ELISA and VN antibody levels in re ars were not accurate indicators of IBV immunity as determined by chal lenge with Mass 41. High tear IBV antibody titers were observed in som e chickens determined to be susceptible to IBV challenge and low tear titers were detected in some protected chickens. This finding suggests that mechanisms other than antibody-mediated immunity in tears are im portant in viral clearance following challenge.