Variability in biological behaviour, pathogenicity, protectotype and induction of virus neutralizing antibodies by different vaccination programmes to infectious bronchitis virus genotype Q1 strains from Chile

Abstract

In the period from July 2008 to 2010, a disease episode resulting in serious economic losses in the major production area of the Chilean poultry industry was reported. These losses were associated with respiratory problems, increase of condemnations, drops in egg production and nephritis in breeders, laying hens and broilers due to infections with infectious bronchitis virus (IBV). Twenty-five IBV isolates were genotyped and four strains were selected for further testing by pathotyping and protectotyping. Twenty-four IBV isolates were of the Q1 genotype. The experiments also included comparing the ability of six vaccination programmes to induce virus neutralizing antibodies (VNA) in layers against four selected Chilean strains. Despite the high genetic homology in the S1 gene between the four strains, the heterogeneity in biological behaviour of these different Q1 strains was substantial. These differences were seen in embryonated eggs, in cell culture, in pathogenicity and in level of cross-protection by IBV Massachusetts (Mass) vaccination. This variability underlines the importance of testing more than one strain per serotype or genotype to determine the characteristics of a certain serotype of genotype. The combination of Mass and 793B vaccine provided a high level of protection to the respiratory tract and the kidney for each strain tested in the young birds. The combination of broad live priming using Mass and 793B vaccines and boosting with multiple inactivated IBV antigens induced the highest level of VNA against Q1 strains, which might be indicative for higher levels of protection against Q1 challenge in laying birds.

Genetic diversity of avian infectious bronchitis virus in China in recent years

“…Different subpopulations of viruses have been identified in the same sample of coronaviruses, such as avian IBVs, through deep sequencing or virus isolation and subsequent sequencing of the viral genomes (de Wit et al, 2017). In this study, we identified two different IBVs and isolated the viruses in the same tissue sample from each of the eight flocks.…”

GI-16 lineage (624/I or Q1), there and Back Again: the history of one of the major threat for poultry farming of our era

“…Finally, a variation in the competitive equilibrium between GI-16 and other pathogens or IBV genotypes (including vaccine strains) could have contributed to shape this genotype epidemiology. The introduction of GI-16 in South America represented an extraordinary epidemiological success from a viral perspective, as reflected by the increase in viral population size reported in the present study and by the outstanding clinical and economic impact in those countries [37]. On the other hand, the clinical impact of this lineage in Italy was negligible in the recent years.…”

“…Nevertheless, its relevance appeared to gradually vanish during the 1990s. Almost simultaneously, a new genotype, often named Q1, emerged in China and was then reported in other Asian countries, Middle East, European and South American countries, being responsible of devastating economic losses [37]. The present phylodynamic analysis demonstrates a common origin of 624/I and Q1, which has been estimated approximately at the beginning or middle of the XX century, depending on the considered genomic region.…”

“…An upgrade in the vaccination strategies was applied in the ‘90s, through the introduction of 793B based vaccines [20]. A Mass plus 793B combined vaccination was proven effective in protecting against GI-16 induced disease [37], and could therefore justify the observed scenario. However, the new protocol was effectively introduced only on the last part of the decade.…”

“…Other studies have demonstrated the presence of relevant biological variations even within the same genotype [37]; the circulation of strains with peculiar pathogenic features could consequently be advocated. Remarkably, recent Italian and South American strains significantly differ in at least three protein positions (i.e.…”