Molecular characterisation of membrane glycoprotein and 5b protein of nephropathogenic infectious bronchitis virus

Background: Infectious bronchitis virus (IBV) affects the upper respiratory tract and the reproductive tract, and some strains can cause nephritis. Large number of serotypes and genotypes of the virus have been identified and for the most part do not cross-protect. Identifying the genotype or serotype of IBV field strains is empirical for selecting an appropriate candidate to serve as vaccine strain for prevention of infectious bronchitis (IB) disease in chickens. The variant strains of IBV could be circulating among chickens in India and recently nephropathogenic IB was reported. Hence, the present work was aimed to carry out molecular characterization of nephropathogenic IBV isolates obtained from two different geographical locations of south India, involving relatively conserved regions. Materials and Methods: MIBVPCR and NIBVPCR primers were used to amplify partial M and N gene after synthesizing cDNA. Isolates Ind/KA/07/1 and Ind/TN/07/2 were subjected to direct sequencing as these two isolates are two different geographical regions and scored better in induction of lesions during pathotyping. Results: Amino acids of membrane glycoprotein varied on five occasions for the isolate Ind/KA/07/1 when aligned with that of M 41 strain and isolate Ind/TN/07/2. Eight amino acids of both isolates in 5b protein were different from that of M41 strain. Few point mutations, short deletions and insertions were noticed in the amplified genome, based on the membrane protein nucleotide sequence comparison. Conclusion: Prevalence of IBV strains with few modifications in conserved regions indicated that there was presence of variant IBV in south India.