Passive Protection of Specific Pathogen Free Chicks Against Infectious Bursal Disease by <i>In‐Ovo</i> Injection of Semi‐Purified Egg‐Yolk Antiviral Immunoglobulins

Abstract

In order to develop an experimental model for passive immunity in SPF chickens, active neutralizing immunoglobulins (Ig) directed against infectious bursal disease virus (IBDV) were extracted from the yolk of eggs laid by conventional layers immunized against IBDV. Concentrated Ig extracts were inoculated via the intra-vitellin route into 7-day-old embryonated SPF hen eggs. Although detrimental to hatchability, Ig inoculation resulted in hatching two series of SPF chicks with passive immunity against IBDV. The neutralizing and ELISA antibody titres at 1 day-old (respectively 12.64 and 13.15 log2; and 4915 and 4277), the kinetics of decay of the anti-IBDV antibodies and the protection afforded by passive antibodies against highly virulent IBDV challenge proved highly consistent with data previously reported on conventional chicks. In-ovo inoculation of purified egg-yolk immunoglobulins may hence be a good experimental model for anti-IBDV maternally-transmitted immunity. This experimental model might possibly be adapted to other pathogens or vaccines for which interference with maternally derived antibodies is a matter of concern at 1 day-old.