Molecular cloning and sequence comparison of the S1 glycoprotein of the Gray and JMK strains of avian infectious bronchitis virus

The nucleotide sequences of S1 glycoprotein genes of the Gray and JMK strains of avian infectious bronchitis virus (IBV) were determined and compared with published sequences for IBV. The IBV Gray and JMK strains had 99% nucleotide sequence similarity. The overall nucleotide sequence similarity of the Gray and JMK strains compared with other IBV strains was between 82.0% and 87.4%. The similarity of the predicted amino acid sequence for the S1 glycoproteins of the Gray and JMK strains was 98.8%. Six of the 10 differences in the amino acid sequence were found between residues 99 and 127, suggesting a possible role for that region in the tissue trophisms of the viruses. The S1 glycoprotein of the Gray and JMK strains had 79.5%–84.6% amino acid similarity with the published sequence of other IBV strains. Serine instead of phenylalanine was observed in the protease cleavage site between the S1 and S2 glycoprotein subunits for the Gray and JMK strains, which was similar to the published sequence for the Ark99 and SE17 strains. The significance of that amino acid change is not known. Based on the nucleotide sequence of the Gray and JMK strains, theBsmAI restriction enzyme was selected by computer analysis and was used in restriction fragment length polymorphism analysis to differentiate the two strains.