Molecular Characterization of Avian Infectious Bronchitis Virus Isolated in Malaysia during 2014-2016
Authors: Leow, B. L.; Aini, Syamsiah S.; Filth, Faizul M. Y.; Redzwan, Muhammad S.; Khoo, C. K.; Ong, G. H.; Basirah, M. A.; Norazura, B.; Mazaitul, Z.; Khairil, Mohd A.; Jihan, Mohd R.; Sohayati, A. R.; Chandrawathani, P.
Avian Infectious Bronchitis (IB) is a highly contagious disease which can cause huge economic losses to the poultry industry. Forty five IB viruses (IBV) were isolated from poultry in Malaysia during 2014-2016. Phylogenetic analysis of the spike glycoprotein 1 (S1) gene revealed that all isolates were clustered into five distinct groups. The predominant type of IBV isolated was QX strains (47%), second was 4/91 type (27%), followed by Malaysian strain MH5365/95 (13%), Massachusetts type (11%) and finally Taiwanese strains (2%). Four types of S1 protein cleavage recognition motifs were found among the isolates which includes HRRRR, RRSRR, RRFRR and RRVRR. To our knowledge, this is the first report describing the motif RRVRR and are unique to Malaysian strains. Six IBVs were grouped in Malaysian MH5365/95 strains. Among these, one isolate was different from others where it only shared 82% identity with MH5365/95 and to others. It formed its own branch in the Malaysian cluster suggesting it may be a variant unique to Malaysia. Alignment analysis of the S1 amino acid sequences indicated that point mutations, insertions and deletions contribute to the divergence of IB variants. This study indicated at least five groups of IBV are circulating in Malaysia with most of the isolates belonged to QX strains. As new IBV variants continue to emerge, further study need to be carried out to determine whether the current available vaccine is able to give protection against the circulating virus.
Infectious bronchitis vaccine virus detection and part-S1 genetic variation following single or dual inoculation in broiler chicks
Authors: Ball, Christopher; Awad, Faez; Hutton, Sally; Forrester, Anne; Baylis, Matthew; Ganapathy, Kannan
An investigation was undertaken of the extent of genetic variation occurring within infectious bronchitis virus (IBV) vaccine strains following vaccination of day-old broiler chicks. Chicks were divided into seven groups, with two groups receiving single Massachusetts (Mass) vaccinations while the other four were inoculated with combinations of different IBV serotypes; Mass, 793B, D274 and Arkansas (Ark). The remaining group was maintained as an unvaccinated control. Following vaccination, swabs and tissues collected at intervals were pooled and RNA was extracted for detection of IBV by reverse transcription polymerase chain reaction. Positive amplicons were sequenced for the part-S1 gene and compared to the original vaccine strain sequences. Single nucleotide polymorphisms, amino acid variations and hydrophobicity changes were identified and recorded for each sampling point. A total of 106 single nucleotide polymorphisms were detected within 28 isolates. The average single nucleotide polymorphism counts of swab isolates were greater than those found in tissue samples. This translated into 64 amino acid changes; however only six resulted in a change to the hydrophobicity properties. All hydrophobic alterations occurred within swab isolates and the majority were recovered at 3 days post vaccination suggesting such changes to be detrimental to early virus survival. Nucleotide deletions were seen only in the group given the combination of Mass and Ark. Of the 16 sequenced samples in this group, 13 contained the same AAT deletion at position 1033 1035 in the Ark strains. Findings presented in this study demonstrate alteration in the S1 nucleotide sequence following co-administration of live IBV vaccines.