BACKGROUND: Infectious Bronchitis Virus (IBV) is causative agent of a highly contagious and acute viral disease. IBV cause significant economic losses to the poultry industry in worldwide. Only a few differences in amino acids of the S1 protein of vaccine and virulent strains of IBV can cause impaired immunity of vaccinated birds.
Objective: To determine the genetic relationship between circulating field strains of infectious bronchitis virus, Massachusetts serotype with vaccine strain.
Methods: Viral RNA was extracted from infected allantoic fluid and the S1 sequence was amplified by RT-PCR. The PCR products were sequenced and their homology with the standard strain of IBV (M41, Baudette, H-120, H-52 and Ma5) derived from the gene bank were compared with BioEdite and MegAlign.
Results: Sequence analysis of isolates showed that they are closely related to Massachusetts serotype. Alignment of the S1 sequences of the isolated viruses with standard IBV strains, revealed high homology of 99% and 97% in nucleotide and amino acid sequences respectively with M41 virus. The nucleotide and amino acid sequences of 14 isolates were very close (99% - 100%) with vaccines H-120, H52, Ma5.
Conclusion: The results of this investigation suggest that comprehensive knowledge on infectious bronchitis virus circulating in different areas is essential for design and probably update the right strategy vaccination against the disease
