Evaluation of Newcastle disease vaccine response in chickens bearing different genotypes of IFN-promoter SNP (−318 A>G) under induced challenge

Ten days challenge trial was conducted for evaluating the effect of IFN-γ promoter SNP (−318A>G) on response to Newcastle disease (ND) vaccine under induced challenge with velogenic ND virus. Genotyped birds of the white synthetic dam line were divided into three groups viz. AA, AG and GG (30 birds/group) out of which 20 birds/group were challenged with dose of 10⁵ EID₅₀ of velogenic ND virus intramuscularly while at same time 10 birds/group were kept as uninfected or control and treated intramuscularly with normal saline. During challenge trial no mortality was observed, neither any clinical signs was seen in the birds. Analysis of data revealed that effect of genotypes on haemagglutinin inhibition (HI) titer at before and at after challenge stages were non-significant. However, at both stages AG group (6.22±0.20; 7.21±0.37) exhibited higher titers followed by GG genotype (5.83±0.37; 7.01±0.31) and least among AA group (5.24± 0.20; 6.22±0.48). Infected birds of all experimental groups displayed significantly higher means of HI titers than those of uninfected control birds. Whereas, among uninfected birds, AG and GG genotypes showed significantly higher titers than those of AA genotyped birds. After the challenge with velogenic virus, Higher titer in AG and GG genotyped birds indicate better immune responsiveness in these genotype as compared to AA genotype, however study with large number of samples are warranted for further confirmation.