Molecular Characterization of Mx1 Gene in Native Indian Breeds of Chicken.

The genetic polymorphism of Mx1 gene was explored in Indian chicken breeds. PCR-RFLP analysis in 102 bp fragment of partial intron 13 and partial exon 14 of Mx1 gene revealed two genotypes viz. RS and SS with two alleles viz. R and S both in Naked Neck and Tellicherry breeds of chicken. The homozygous genotype RR was not identified. When deduced amino acid sequences were compared, the asparagine amino acid was found to be substituted in "R" allele for serine in "S" allele. PCR-SSCP analysis of 284 bp fragment in 5'-UTR and partial promoter region revealed three genotypes viz. CC, CG, and CH with three different alleles viz. C, G, and H in Naked Neck breed of chicken and five genotypes viz. DI, JK, KK, KL, and KM with six different alleles viz. D, I, J, K, L, and M in Tellicherry breed of chicken. The homozygous genotypes viz. GG and HH in Naked Neck and DD, II, JJ, LL, and MM in Tellicherry chicken was not identified. The nucleotide substitution rate estimated to be in the range of 0.004-0.011. The identified genetic variation can be helpful for better insight to disease resistance property of the Mx1 gene.

Cytokine gene expression following RSV-A infection.

The present study determines the cytokine gene expression in chickens following RSV-A infection, using RT-qPCR. In susceptible chickens tumors progressed to  fulminating metastatic tumors while it regressed in  regressors  chickens and some resistant non-responder chickens did not respond to RSV-A infection and thus did not develop tumors at all. The in vivo expression of pro-inflammatory cytokines, Th1 cytokines and Th2 cytokines was determined at the primary site of infection, as well as in different organs of progressor, regressor and non-responder chicks at different time intervals. Our results indicated a significant upregulation of the pro-inflammatory cytokines, IL-6 and IL-8, in all the organs of progressor chicks, while they were significantly lower in regressor and non-responder chicks. The expression of the Th1 cytokines IFN-γ and TNF-α was low in all of the organs of the progressor group, except that in  spleen. In contrast, regressor and non-responder groups showed high expression of IFN-γ and TNF-α. Further, there was an early upregulation of the expression of the Th2 cytokine, IL-10, TGF-ß and GM-CSF, in all of the organs of progressors as compared to uninfected control.

MHC-B haplotypes impact susceptibility and resistance to RSV-A infection.

We investigated the impact of haplotype of major histocompatibility complex (MHC)-B on the outcome of infection of Synthetic Dam Line (SDL) broiler strain with Rous Sarcoma Virus (RSV). Genomic analysis of MHC-B haplotypes, revealed a total of 12 known standard haplotypes that constituted to twenty-five different genotypes and one new haplotype of 217 bp size, designated BX. The inoculation of RSV-A in SDL chicks resulted in the development of tumors of progressive or regressive phenotypes with varying tumor profile index (TPI). Haplotypes B2, B21 and B22had low TPI scores (1 or 2) with less mortality and were resistant to RSV-A tumor. The haplotypes B13, B13.1., B15, B15.1. and B15.2. had significantly higher TPI scores (5 or 6), indicating a susceptibility to RSV-A. The genotype, Bx /Bx, had a mean TPI score of 3.67 ± 1.33, which was closer to the resistant haplotype. Sequence analysis of the new haplotype (BX) revealed 99.5% similarity with B2 haplotype. Metastases was observed in 44% of chicks and comprised of mixed fibrosarcoma and myxosarcoma.