Emerging of Infectious Bronchitis Virus (renal mutant) Evading Chicken Vaccinal Immunity in Ismailia, Egypt

Abstract

In spite of regular vaccination of chicken flocks in Egypt with Infectious Bronchitis Virus (IBV) vaccine, respiratory and kidney lesions had developed. Six vaccinated chicken flocks (5000/flock) in Ismailia, Egypt showed IB- like symptoms was screened for IBV isolation in SPF embryonated chicken eggs. Four Isolates of IBV were characterized and identified at the pathological, biological, physical and molecular level. IB virus spike (S1) gene was amplified by RT-PCR and sequence analysis of the hypervariable region of S1 gene using specific forward and reverse primers was done. Electrophoretic pattern of amplified S1 gene showed a specific band at 380 bp. IBV Ismailia isolates are clustered in distinct phylogenetic group with 4 recent IBV isolates circulating in Egypt since 2012 (Egypt/12197B/2012, Eg/CU-2/2012, Egypt/12120s/2012 and Egypt/01-13/VIR9715/2012). IBV Ismailia isolates showed 99.41%, 99.12%, 98.83 % and 98.54 % nucleotide sequence identity and 99.12 %, 100 %, 99.12% and 98.25% amino acid identity to the Egyptian IBV variants, respectively. In a conclusion, IBV Ismailia isolates are closely related to the recent Egyptian IBV isolates circulating in Egypt except minor changes in nucleotides and amino acids sequences. IBV Ismailia isolates are different from the currently IB virus strains used for vaccine production, indicating a constant evolution of IBV in Egypt. This difference necessitates continuous montoring to control the spread of infections and the development and use of vaccine should be based on indigenous viruses.