Isolation and genetic analysis revealed no predominant new strains of avian infectious bronchitis virus circulating in South China during 2004–2008

Abstract

Twenty-seven strains of avian infectious bronchitis virus (IBV) were isolated from dead or diseased chickens at different chicken farms in South China during 2004-2008, of which the S1 gene was sequenced. Phylogenetic analysis of the S1 gene sequences of the isolated 27 strains together with 29 strains published in Genbank revealed that all IBV strains except for one isolated and one published were clustered into six distinct genotypes I-VI. 26 isolated strains belong to genotypes I, II, and III, forming a big phylogenetic branch without new predominant strains, whereas all five vaccine strains belong to genotype V that is evolutionarily distant from genotypes I, II, and III. The study of the protease cleavage motif within the S1 protein found 12 different cleavage motifs, of which 3 motifs are shared by both isolated and published strains, 2 motifs unique to isolated strains, and 7 motifs unique to published strains, further bolstering the notion of no new predominant strains. Alignment analysis of the S1 amino acid sequences indicated that the amino acid substitutions, insertions, and deletions are polymorphic and diverse, showing no sign of predominant genetic changes among the isolated strains. Taken together, there was no predominant new strain circulating in South China during 2004-2008. Nonetheless, circulating IBV strains have been continuously evolving with genetic compositions distant from vaccine strains; this explains why there have been constant but infrequent outbreaks in commercial flocks in South China during 2004-2008. Furthermore, in order to safe guard against the sudden emergence of new predominant strains, continuing surveillance of IBV strains circulating in the field is of extreme importance.

Phylogenetic analysis of infectious bronchitis coronaviruses newly isolated in China, and pathogenicity and evaluation of protection induced by Massachusetts serotype H120 vaccine against QX-like strains

“…Most of them belonged to genotype I (Figure 1). This result was consistent with other studies conducted in China (Liu et al, 2006(Liu et al, , 2008(Liu et al, , 2009Xu et al, 2009;Li et al, 2010), which confirms that this genotype is the predominant IBV type circulating in chicken flocks in China. Interestingly, phylogenetic analysis of large numbers of strains of genotype I isolated from 1997 to 2009 in China showed that this type of virus was split in two major phylogenetic clusters, represented by strains LX4 and QX, respectively (Figure 1).…”

“…The results of IBV surveillance contrast with the conclusion drawn by Li et al (2010), who reported that no new strains of IBV have circulated in South China in recent years. In the mid-1990s, transmissible proventriculitis, which was associated with IBV infection, was reported both in layer hens and broilers in China (YuDong et al, 1998).…”

“…A very challenging aspect of the epidemiology of IBV in China is the emergence of new strains and variants (Li & Yang, 2001;Yu et al, 2001;Liu & Kong, 2004;Liu et al, 2005Liu et al, , 2006Liu et al, , 2008Liu et al, , 2009Xu et al, 2009;Li et al, 2010). In the present study, isolate CK/CH/ LGX/091110 was established as a new group based on phylogenetic analysis of the S1 gene.…”

“…Although vaccines based on Mass-type strains, such as H120 and H52, have been in use for many years on poultry farms, the regular occurrence of suspected IB and the isolation of the virus from vaccinated flocks (Li & Yang, 2001;Yu et al, 2001;Liu & Kong, 2004;Liu et al, 2005Liu et al, , 2006Liu et al, , 2008Liu et al, , 2009Xu et al, 2007;Li et al, 2010) implies that poor protection is provided by the Mass-type vaccines. This indicates the importance of continued surveillance of IBV in chicken flocks in China.…”

Sambucus nigra Extracts Inhibit Infectious Bronchitis Virus at an Early Point during Replication

“…Interestingly, while vaccination is the main method for inhibiting IBV in poultry populations [77], its effectiveness on new strains is often minimal, leading to outbreaks in even vaccinated populations [78][79][80]. Perhaps vaccination in conjunction with administering the active polyphenol could have a synergistic effect, similar to that seen when the polyphenol isoquercetin was administered with the influenza medicine amantadine in vitro [24].…”