Immune Responses In Chicks After Single Or Dual Vaccination With Live Infectious Bronchitis Massachusetts And Variant Vaccines: Some Preliminary Findings

GANAPATHY K., ROTHWELL L., LEMIERE S., KAISER P. and JONES RC

 

lnfectious bronchitis (lB) is an economically important viral disease in chickens, mainly affecting the respiratory, urinary and reproductive systems. For the prevention of the disease, live and inactivated vaccines have been used for many decades but due to the ability of the virus to mutate or to form recombinants, occasionally novel variant viruses can penetrate through the protection conferred by existing vaccines. To overcome this, it has been shawn that when chicks are vaccinated with two different serotypes, there is a broader protection against a range of unrelated IBV challenge viruses compare to homologous vaccines. Despite the widespread use of such vaccination regimes, the underlying immune mechanisms involved are not known. This paper reports on sorne preliminary findings on humoral and cell-mediated immune responses of chicks vaccinated first with live Massachusetts (H120) vaccine then followed by a live 793B (CR88) vaccine. ln addition, protection conferred against virulent IBV M41, 793B, QX, ltaly-02 and D1466 were assessed using an in vitro tracheal organ culture challenge model.

 

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