Protective immune response of chickens against Newcastle disease, induced by the intranasal vaccination with inactivated virus

Intranasal vaccination of chickens with inactivated Newcastle disease virus (NDV) induced both local and systemic antibody responses, resulting in protection against intranasal challenge with a lethal dose of a virulent NDV strain. The immune response was enhanced by the use of cholera toxin B subunit (CTB) as an adjuvant and only small amounts of the challenge virus were recovered from the birds vaccinated together with CTB. On the other hand, subcutaneous vaccination with the same antigen induced only a serum antibody response in chickens, allowing the challenge virus to replicate in the sinus. The present results indicate that secretory antibodies induced on the respiratory mucosal surface by intranasal vaccination with inactivated NDV protected chickens from lethal infection by inhibiting virus replication at the portal of entry for the virus.