To evaluate mucosal immunity of normal and immunosuppressed chickens vaccinated with live Newcastle disease (ND) vaccine, cyclophosphamide (CY) was used to generate immunosuppressed chickens. Normal and immunosuppressed chickens were vaccinated with the Lasota ND vaccine by ocular-nasal route at three weeks of age and challenged with virulent ND virus (vNDV) at day 28 post-vaccination (pv). The immunosuppressed chickens had significantly lower relative weight of the bursa of Fabricius and serum antibody HI titers compared to CY-untreated chickens. Compared with normal chickens, significant lower levels of IgA antibodies were detected in tracheal washings, duodenal washings and bile of immunosuppressed chickens in the whole experimental period. Immunohistochemical experiment also showed that small numbers of IgA positive cells were found in intestinal tissues of immunosuppressed chickens at day 28 pv. There was only a partial protective effect on immunosuppressed chickens post challenge with virulent ND virus (vNDV). These findings increase our understanding of the protective mucosal immune response against ND vaccine and suggest that mucosal immunity play an important role against NDV infection.

Key words: Cyclophosphamide (CY); IgA; Immunosuppression; Mucosal immunity; Newcastle disease (ND); Vaccine