Increased level of protection of respiratory tract and kidney by combining different infectious bronchitis virus vaccines against challenge with nephropathogenic Brazilian genotype subcluster 4 strains

Abstract

Genotyping of seven infectious bronchitis virus (IBV) strains isolated in Brazil showed that all belonged to the common Brazilian genotype and that these strains were closest to the subcluster of strain IBV/Brazil/2007/USP-19. Pathotyping of four selected Brazilian strains showed that they all caused a considerable level of ciliostasis in the trachea but at a somewhat lower level than did M41 and Brazilian strains 50/96, 57/96, 62/96 and 64/96 representing four different serotypes that had been reported earlier. In contrast to the M41 challenge strain, all Brazilian isolates replicated in kidney tissue in a high percentage of non-vaccinated challenged birds, clearly showing that they are nephropathogenic. As for the tracheal protection, the results using Massachusetts (Mass) vaccination against the recent strains seemed to show protection higher on average than for the strains reported earlier. A single or twofold vaccination with a Mass vaccine resulted in a mean tracheal protection level against the four challenge strains of 92% and 90%, respectively, whereas a single and twofold vaccination with a Mass vaccine halved the percentage of infected kidneys (14% and 13%, respectively, P < .05) compared to that of the unvaccinated birds (27%). The combination of the Mass and the 793B vaccine provided on average a tracheal protection of 99% and a reduction of the percentage of infected kidneys to a mean of 2%. This was a significantly (P < .05) higher protection than that achieved by a single or twofold Mass vaccination, showing the added value of the 793B vaccination following priming with a vaccine of the Mass type.

S1 gene-based phylogeny of infectious bronchitis virus: An attempt to harmonize virus classification

“…The GI-11 lineage has been associated with a variety of clinical conditions, ranging from respiratory disease, infertility, drop in egg production and egg quality (Chacón et al, 2011(Chacón et al, , 2008Montassier, 2010;Villarreal et al, 2007a) to enteric disorders (Villarreal et al, 2010;Villarreal et al, 2007b). It was recently demonstrated that the Brazilian variant causes predominantly respiratory and kidney diseases under experimental conditions (Chacón et al, 2014: de Wit et al, 2015. Interestingly, our phylogenetic analysis demonstrates that the indigenous GI-11 lineage has been circulating in the country since 1975, supporting the hypothesis of Montassier (2010) that this variant had already been present in the field since at least as early as 1988.…”

Genetic mutations in live infectious bronchitis vaccine viruses following single or dual in vitro infection of tracheal organ cultures

“…Since the first description of IBV in the 1930s (Schalk & Hawn, 1931), there have been a number of genotypes reported worldwide that are known to infect chicken, such as Massachusetts (Mass), Connecticut, Arkansas, 793B, It-02, QX, Q1 and Dutch strains (Jackwood, 2012). Live IBV vaccines, often two different serotypes, are co-administered to young chicks for protection against most virulent viruses (Awad et al, 2016;Chhabra et al, 2015;De Wit et al, 2015).…”

Rapid detection and differentiation of avian infectious bronchitis virus: an application of Mass genotype by melting temperature analysis in RT-qPCR using SYBR Green I

“…This constant arising of new IB variants in different countries [8,18] is usually pointed as the main cause of vaccine failures in the field and constitutes a great challenge for the molecular direct diagnosis of IBV.Variants of IBV are mutants evolving from parental strains of this virus that differ from strains considered classic, such as those from Massachusetts group, regarding genotype, pathotype, antigenicity and/or immunogenicity. Additionally, IBV mutants are constantly subject to host immune selection and only strains with high antigenic variation are able to evade immune responses induced by vaccines and to survive in the population of hosts, leading to the development of clinical disease [25].Protection studies between commercial vaccines and IBV variants, especially those using Massachusetts (Mass) vaccines, which is the most common attenuated available vaccine, have demonstrated at least partial cross-protection by some authors [9,10,12,14,34], while another studies have not found cross-protection [7,35].Therefore, the rapid detection of IBV infection in poultry flocks and its classification between Mass and variants is considered as major challenge, which requires use of appropriate diagnostic methods. To overcome this issue, several rapid assays have been developed focusing on detection and/or characterization of S1 gene of IBV, including direct gene sequencing, RT-PCR methods with serotype-specific primers, and RT-PCR/RFLP, have become widely used, because their results correlated well with the virusserotyping [19,21,22,33].…”

“…Protection studies between commercial vaccines and IBV variants, especially those using Massachusetts (Mass) vaccines, which is the most common attenuated available vaccine, have demonstrated at least partial cross-protection by some authors [9,10,12,14,34], while another studies have not found cross-protection [7,35].…”