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The infectious bronchitis virus (IBV) causes a highly contagious disease [infectious bronchitis (IB)] that results in substantial economic losses to the poultry industry worldwide. We conducted a molecular and phylogenetic analysis of the S1 gene of Brazilian (BR) IBV isolates from a routinely vaccinated commercial flock of broiler breeders, obtained from clinical IB episodes that occurred in 24-, 46- and 62-week-old chickens. We also characterized the antigenicity, pathogenesis, tissue tropism and spreading of three IBV isolates by experimental infection of specific pathogen-free (SPF) chickens and contact sentinel birds. The results reveal that the three IBV isolates mainly exhibited mutations in the hypervariable regions (HVRs) of the S1 gene and protein, but were phylogenetically and serologically closely related, belonging to lineage 11 of the GI genotype, the former BR genotype I. All three isolates caused persistent infection in broiler breeders reared in the field, despite high systemic anti-IBV antibody titres, and exhibited tropism and pathogenicity for the trachea and kidney after experimental infection in SPF chickens and contact birds. In conclusion, BR genotype I isolates of IBV evolve continuously during the productive cycle of persistently infected broiler breeders, causing outbreaks that are not impaired by the current vaccination programme with Massachusetts vaccine strains. In addition, the genetic alterations in the S1 gene of these isolates were not able to change their tissue tropism and pathogenicity, but did seem to negatively influence the effectiveness of the host immune responses against these viruses, and favour viral persistence.

Abstract.A competitive liquid-phase-blocking concanavalin A enzyme-linked immunosorbent assay (LPB-ConA-ELISA) was developed in the current study. The assay used ConA as a capture reagent, and the sera of specific pathogen-free chickens immunized with nonpurified Newcastle disease virus (NDV) suspension as detector antibodies, to detect and quantify specific antiviral antibodies in serum samples from free-ranging pigeons. The comparison between the LPB-ConA-ELISA and the hemagglutination inhibition (HI) test for the detection of antibodies in serum samples from 107 pigeons showed significant correlation between the assays (r = 0.875), a high sensitivity (100%), specificity (95.8%), accuracy (96.3%) for the ELISA, and good agreement (κ = 0.83) between the 2 assays. The results of this study suggest that the LPB-ConA-ELISA could be a useful alternative to HI test in the serodiagnosis of NDV in pigeons, or other species of birds.

RESUMO:A bronquite infecciosa das galinhas (BIG) é uma doença infecciosa causada pelo coronavírus aviário (vírus da bronquite infecciosa -VBI) que está amplamente disseminada entre as criações avícolas comerciais na maior parte do mundo. Esse vírus apresenta alta capacidade de variabilidade genética, o que se traduz pelo aparecimento de alterações marcantes na composição, estrutura e propriedades antigênicas e biológicas de suas proteínas. Diante disso, este trabalho tem por objetivo realizar uma revisão bibliográfica sobre os novos genótipos, tipos antigênicos e de patotipos do VBI que foram isolados nas últimas décadas no Brasil, abordando principalmente a imunogenicidade dessas estirpes do VBI. Assim, essa revisão destaca que com o aparecimento de variantes antigênicas e biológicas entre as estirpes do VBI nos últimos anos, ocorreu o surgimento de diferentes genótipos, sorotipos e patotipos deste vírus o que resultou em um aumento nas falhas vacinais contra esta doença e a necessidade de serem desenvolvidas novas preparações vacinais que proporcionem tanto respostas mediadas por anticorpos como por células T, especialmente no compartimento das mucosas e que resultem em um estado de proteção mais efetivo contra as variantes brasileiras do VBI. Palavras-chave:Coronavírus aviário. Ornitopatologia. Vacinação. AVIAN INFECTIOUS BRONCHITIS VIRUS: IMMUNOGENICITY PROFILES AND NEW PATHOTYPES IN BRAZIL -LITERATURE REVIEW SUMMARY: Infectious bronchitis of chickens (BIG) is an infectious disease caused by avian coronavirus (IBV)that is widely disseminated among commercial poultry farms in most parts of the world. IBV has a high genetic variability, which is reflected by the appearance of marked changes in the composition, structure and antigenic and biological properties of its proteins. Therefore, the objective of this work is to carry out a bibliographical review on the new genotypes, antigenic types and IBV pathotype that have been isolated in the last decades in Brazil, mainly addressing their immunogenicity profiles. With the appearance of antigenic and biological variants among IBV strains in the last years, different genotypes, serotypes and pathophyses of this virus occurred, which resulted in an increase in vaccine failures against this disease and the need to develop new vaccine preparations which provide both antibody and T cell mediated responses, especially in the mucosal compartment, and which result in a more effective protection status against Brazilian VBI variants.

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