Coronavirus avian infectious bronchitis virus

Abstract

-Infectious bronchitis virus (IBV), the coronavirus of the chicken (Gallus gallus), is one of the foremost causes of economic loss within the poultry industry, affecting the performance of both meat-type and egg-laying birds. The virus replicates not only in the epithelium of upper and lower respiratory tract tissues, but also in many tissues along the alimentary tract and elsewhere e.g. kidney, oviduct and testes. It can be detected in both respiratory and faecal material. There is increasing evidence that IBV can infect species of bird other than the chicken. Interestingly breeds of chicken vary with respect to the severity of infection with IBV, which may be related to the immune response. Probably the major reason for the high profile of IBV is the existence of a very large number of serotypes. Both live and inactivated IB vaccines are used extensively, the latter requiring priming by the former. Their effectiveness is diminished by poor cross-protection. The nature of the protective immune response to IBV is poorly understood. What is known is that the surface spike protein, indeed the amino-terminal S1 half, is sufficient to induce good protective immunity. There is increasing evidence that only a few amino acid differences amongst S proteins are sufficient to have a detrimental impact on cross-protection. Experimental vector IB vaccines and genetically manipulated IBVs -with heterologous spike protein genes -have produced promising results, including in the context of in ovo vaccination.

Phylogeny and S1 Gene Variation of Infectious Bronchitis Virus Detected in Broilers and Layers in Turkey

“…cross-protection between different viral genotypes make the control of infections difficult (6,7,12,22). Therefore it is important to genetically characterize circulating strains of IBV to guide national or regional strategies for combating IB by designing appropriate diagnostics and vaccination regimes.…”

“…It has a 27 to 28 kb genome encoding four structural proteins, spike (S), membrane (M), envelope (E), and nucleocapsid (N) (6). Genetic differences affecting antigenicity and immunogenicity are mainly restricted to the S protein.…”

Construção de uma biblioteca de fragmentos de anticorpos monoclonais de galinhas com cadeia única (scFv) por phage display com reatividade cruzada para estirpes heterólogas do vírus da bronquite infecciosa aviária

“…Ademais, a proteína N está, na partícula do VBI, intimamente relacionada com o RNA genômico e apresenta uma estrutura altamente conservada, com cerca de 94 a 99% de identidade entre as várias estirpes do VBI (CAVANAGH, 2007). Foi demonstrado ainda que esta é uma proteína altamente imunogênica, sendo, por conseguinte, capaz de induzir a produção de anticorpos contra antígenos mais conservados do grupo do VBI e, ainda, de linfócitos T efetores específicos, sobretudo com ação citotóxica (WILLIAMS, et al, 1992;SEO, et al 1997;SEAH, et al, 2000).…”

“…Esse vírus possui envelope lipoproteico e genoma constituído por uma fita de RNA simples, não segmentada, com sentido positivo. São codificadas quatro proteínas estruturais: a glicoproteína de espícula (S), a glicoproteína de membrana (M), a pequena proteína de membrana (E) e a proteína de nucleocapsídeo (N) (CAVANAGH, 2007;DI FÁBIO & ROSSINI, 2000).…”

“…A consequência disso é o isolamento contínuo de estirpes variantes, que causam a quebra da imunidade conferida pelas estirpes vacinais e dificultam o diagnóstico (CAVANAGH, 2007).…”