The S1 gene study of avian infectious bronchitis virus (IBV) isolated from local disease outbreaks

Abstract

Infectious bronchitis (IB) is an acute and highly contagious respiratory, renal, and reproductive organ infection of chickens. Infectious bronchitis virus (IBV) that replicates in epithelial cells of the trachea resulting in respiratory signs (sneezing, cough, tracheal rales, gasping and nasal discharge. This study was carried out to monitor Infectious bronchitis virus (IBV) infection in local disease outbreaks in Khyber Pakhtunkhwa (KP), Pakistan. A total of 57 chickens (broilers & layers) were examined for the presence of IBV. Tissue samples were screened through reverse transcriptase PCR (RT-PCR) to detect IBV S- glycoprotein gene (surface glycoprotein gene) and to amplify the hypervariable region of the S1-glycoprotein gene. Ten samples were found to be positive for the infectious bronchitis virus (IBV) after the initial PCR screening from the original 57 samples. An expected approximately 298bp band was noticed in detection of RT-PCRs. The samples found to be positive by the detection of PCR were further processed for the genotyping RT-PCR of the S1 gene. An approximately 700 bp band was seen in all the 10 cases. The bands were gel-purified and then sent for DNA sequencing. HKY model for Neighbour joining with 1000 bootstrap replicates in Program Geneious (10.2.3 version) was used to construct a phylogenetic tree. Next, we performed amino acid sequence alignment of these positive samples with the amino acid sequences of the previously reported two sequences of the S-1 gene of M41(Massachusetts 41) strain in Pakistan which were used in Phylogenetic analysis. This revealed that 4 sample amino acid sequences were closely related (93-100%) with Pakistan reported IBV sequences (KY588135 and KU145467). Our current study of IBV isolates revealed an identity of 60% with the isolates reported from China, 30% identity with the isolates reported in Pakistan and 10% identity with the isolates reported from India