Vaccination of Congenitally-Immune Chicks against Newcastle Disease Virus

Abstract

Summary

One to 2-day-old chicks with different levels of passive immunity and controls were vaccinated with an homogenate of chemically-inactivated Newcastle disease virus antigen-antibody complexes, excess antibody, and aluminum hydroxide adjuvant. The antigen-antibody complex vaccine protected 65% or more of the chicks (usually < 80%) against a challenge dose of 10^4.5 BLD₅₀ for at least 10-weeks postvaccination. Comparable protection was not achieved in the passively-immune chicks when vaccinated with preparations containing only antigen and adjuvant. In susceptible chicks, however, the antigen-antibody complex vaccine did not confer any better protection against challenge inoculation than did simple vaccines. It was concluded that immunological refractoriness of congenitally-immune chicks can be surmounted by appropriate vaccination with an antigen-antibody complex vaccine.