S1 gene sequence analysis of a nephropathogenic strain of avian infectious bronchitis virus in Egypt

Abdel-Moneim, Ahmed S; El-Kady, Magdy F; Ladman, Brian S; Gelb, Jack

In the S1 subunit, three HVRs are located within amino acids 38-67, 91-141 and 274-387 [4] [5] [6] . HVR1 and HVR2 contain sequences that have been associated with specific IBV serotypes [34, 35] as well as serotype specific neutralizing epitopes [4, 5, 14] . IBV serotypes commonly differ by 20 to 25% in S1 [11, 36] but some serotypes differ in S1 by as little as 2% [13] . Although H120 showed 97% amino acid and nucleotide identity to Egypt/F/03, it possesses 34 different nucleotides that resulted in 14 amino acid substitutions. Among such amino acids, one is located in HVR1, four in HVR2 and one in HVR3 (Fig.4) . The region between amino acid residues 123-152 has been previously identified as a possible region involved in the differing pathogenicity of Gray and non-virulent JMK strains [37] . Egypt/F/03 possesses different amino acid; phenylalanine within this region at positions 130 and 141 instead of serine and leucine in H120 respectively. It is apt to mention that some serotypes differ in S1 by as little as 10 amino acids [13] , suggesting that only a few epitopes may induce most of the VN antibody [38] .