Current situation, genetic relationship and control measures of infectious bronchitis virus variants circulating in African regions

Abstract

Infectious bronchitis virus (IBV) is a major viral pathogen of commercial poultry, affecting chickens of all ages and causing major economic losses in poultry industry worldwide. Frequent points of mutations and recombination events in the S1 gene region, result in the emergence of new IBVs variants circulating in the form of several serotypes/genotypes that can be partially or poorly neutralized by current vaccines. IBV is well studied worldwide, nevertheless in African countries epidemiological and scientific data are poor and not updated.This review aims to give a current overview of IBV situation, to establish evolutionary relationship between the African variants and to list some of the potential measures to control IBV in Africa.Three S1 gene hypervariable regions were studied and compared to the reference genotypes/serotypes that found emerging in African regions. This comparison was based on phylogenetic trees, nucleotide and amino-acid sequence analysis. It clearly appears that IBV variants reported in Africa, display a low genetic relationship between them and with the majority of the reference strains emerging in neighboring countries, except the case of variants from Libya and Egypt that show a high relatedness. Also the Massachusetts serotypes were the most prevalent co-circulating Abbreviations: IBV, infectious bronchitis virus; IB, infectious bronchitis; S, spike; M, membrane; N, nucleocapsid; HVR, hyper variable region; nt, nucleotide.

Comparative features of infections of two Massachusetts (Mass) infectious bronchitis virus (IBV) variants isolated from Western Canadian layer flocks

“…QX like IBV strains) and Mass type IBV isolates recovered from various geographical areas [18,42,43,45,46]. Nephropathogenic QX-type strains are distantly related to the M41 strain and their genetic similarity is 78.6% [60]. Based on the partial S1 sequence analysis of three nephropathogenic IBV isolates, which belong to the Mass genotype revealed that they are more than 99.1 and 97.8% identical to the classical M41 strain in nucleotide and deduced amino acid sequences, respectively [61].…”

Limited Cross-Protection against Infectious Bronchitis Provided by Recombinant Infectious Bronchitis Viruses Expressing Heterologous Spike Glycoproteins

“…Effective vaccination against IBV is proving to be an increasing challenge due to the emergence of novel strains, such as QX, first isolated in China, in 1995 [ 29 ], and subsequently spread worldwide [ 30 , 31 , 32 ]. Whilst some strains of IBV have spread worldwide, others have emerged but remained limited to distinct geographical areas [ 33 , 34 ]. Commercial live IBV vaccines are generated through multiple passages of a pathogenic field isolate through embryonated hen’s eggs with the aim of generating a virus that is attenuated but still immunogenic [ 35 , 36 ].…”

Avian Coronavirus: Case of Infectious Bronchitis Virus Pathogenesis, Diagnostic Approaches, and Phylogenetic Relationship Among Emerging Strains in Middle East and North Africa Regions

“…It is an enveloped positive-stranded RNA virus with a genome of about 27.6 kb in length encompassing 5 0 and 3 0 untranslated regions with a poly(A) tail. A major part of the genome is composed of two overlapping open reading frames (ORFs), 1a and 1b, which are translated into large polyproteins, 1a and 1ab, respectively, and contribute to the formation of the replication and transcription complex (Cavanagh., 1997;Khataby et al, 2016b). The remaining part of the genome encodes for four structural proteins that are called the phosphorylated nucleocapsid protein (N), the membrane glycoprotein (M), the envelope protein (E), and the spike glycoprotein (S).…”

“…The high variation in the nucleotide sequences of spike gene can change the protection ability of a vaccine or immunity (Cavanagh and Naqi, 2003). Some reports have demonstrated that this genetic diversity, due to changed genomic virus by frequent point mutations and recombination events in the S1 gene, has given the emergence of new IBV variants that can be partially or poorly neutralized by existing vaccine serotypes (Khataby et al, 2016b). Wherefore, the phylogenetic analysis of the S1 gene is the most useful strategy to differentiate IBV genotypes and serotypes, because it correlates closely with the serotype and permits the selection of the appropriate vaccine serotypes for IB control in each of the geographic regions (Jackwood, 2012).…”

“…The evolutionary characterization of IBV is essentially based on the analysis of the variable S1 gene or the expressed S1 protein. Moreover, three hypervariable regions (HVR1, HVR2, and HVR3) located at the positions 114À201, 297À423, and 822À1161 nt corresponding respectively, to amino acid residues 38À67, 91À141, and 274À387 have been located within the S1 subunit (Bourogâa et al, 2009;Khataby et al, 2016b).…”