Investigation of post-immunization immune response gene expression kinetics in lymphoid tissues of White Leghorn and Indian native chicken

Understanding the basal expression kinetics of genes related to innate immunity aids effective genetic selection for immune response and how host genetics behaves with tolerance to Newcastle disease (ND) is obscure. It was hence aimed to investigate post-immunization mRNA expression kinetics of some immune response genes in White Leghorn, Aseel and Kadaknath chicken. Day-old chicks were vaccinated with ND RDF-1 strain with booster dose at 28-days of age at the experimental layer farm of ICAR-Central Avian Research Institute, Izatnagar (India) and lymphoid tissues were collected in RNAlater at 42-days of age. Total RNA was extracted and first strand cDNA was synthesized. Relative quantification of mRNA expression of IL1-β, IFN-γ, iNOS and TLR15 gene was assessed by qRT-PCR. The mRNA expressions significantly varied among the genes in spleen and thymus, and moderate expression of IFN-γ in all chicken genotypes suggested good protection against Newcastle disease virus. IL1-β-mRNA expressed at the highest level (P˂ 0.05) in spleen followed by thymus and bursa, whereas IFN-γ and iNOS expressed highly (P˂ 0.05) in thymus followed by spleen and bursa. In case of TLR15, the expression was significantly the highest in spleen followed by bursa and thymus. Kadaknath had the highest (P˂ 0.05) expression of IL1-β in thymus and that of iNOS in spleen, whereas Aseel showed the least (P > 0.05) expression than Kadaknath and White Leghorn. The study revealed the existence of wide variation in basal expression levels of immune response genes among different lymphoid tissues and lack of discernible differences in the expression between the chicken genotypes.