Respostas imunes e proteção induzidas por uma vacina viva atenuada formulada com uma variante brasileira do vírus da bronquite infecciosa contra desafios com estirpes homóloga e heteróloga
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Data
2018-11-20
Autores
Kasmanas, Thaiane Coelho [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O Vírus da Bronquite Infecciosa (VBI) é caracterizado por alta variabilidade genética que gera um grande número de variantes antigênicas e biológicas devido a mutações pontuais, inserções, deleções e recombinações que podem ocorrer em várias partes do genoma viral e, especialmente, no gene S1. O controle da Bronquite Infecciosa (BI) por meio de vacinas torna-se assim bastante complexo, mas a vacinação ainda é uma das abordagens mais eficazes para a proteção contra a infecção pelo VBI. Desde o ano 2000, o Brasil vem apresentando uma incidência aumentada de surtos de BI causados por estirpes variantes classificadas no genótipo I - linhagem 11 (GI-11) ou no genótipo BR-1 e, até 2016, havia disponíveis para comercialização somente as vacinas vivas atenuadas do genótipo Massachusetts. Nesse ano, uma indústria farmacêutica brasileira desenvolveu e conseguiu, com base em testes de proteção em frangos SPF, a permissão do Ministério da Agricultura, Pecuária e Abastecimento (MAPA) para comercializar uma vacina viva atenuada formulada com uma variante brasileira (BR-1). O objetivo deste trabalho foi avaliar, em frangos de corte comerciais, a proteção induzida por esta nova vacina viva atenuada comercial, quando administrada isoladamente ou quando combinada com outra vacina viva atenuada comercial formulada com estirpe do genótipo Massachusetts. Para tanto, a resposta imune humoral sistêmica foi mensurada pelo teste de ELISA comercial e os escores de proteção para ciliostase traqueal, lesões microscópicas e carga viral por RT-qPCR foram avaliados na traqueia, pulmões e/ou rins dos diferentes grupos de aves vacinadas contra os desafios com estirpes homóloga (estirpe virulenta brasileira - BR-1) ou heteróloga (estirpe virulenta Massachusetts). Os resultados mostraram que a vacinação combinada conferiu uma maior imunoproteção caracterizada por menores escores de ciliostase traqueal, lesões microscópicas mais leves e carga viral mais reduzida e menos persistente após o desafio homólogo com estirpe BR-1. Foi também observada uma imunoproteção parcial contra a estirpe virulenta BR-1 nos grupos mono vacinados, ou somente com a vacina BR-1 ou com a vacina Massachusetts, mas não foi registrada nenhuma proteção relevante para as aves vacinadas somente com BR-1 após o desafio com a estirpe virulenta Massachusetts. Em conclusão, o protocolo vacinal que combina as vacinas atenuadas com as estirpes atenuadas BR-1 e Massachusetts pode ser utilizado de forma bem sucedida para induzir em frangos de corte de criações comerciais respostas imuno protetoras mais eficazes contra estirpes variantes brasileiras (BR-1) e Massachusetts do VBI.
Infectious Bronchitis Virus (IBV) is characterized by high genetic variability that generates a large number of antigenic and biological variants due to point mutations, insertions, deletions and recombination that may occur in various parts of the viral genome and especially in the S1 gene. The control of Infectious Bronchitis (IB) through vaccines thus becomes quite complex, but vaccination is still one of the most effective approaches to protection against IBV infection. Since the year 2000, Brazil has been presenting an increased incidence of IB outbreaks caused by variant strains classified as genotype I - lineage 11 (GI-11) or in genotype BR-1, and until 2016, only live attenuated vaccines containing the Massachusetts genotype were commercially available. In this year, one Brazilian pharmaceutical industry developed and achieved, on the basis of protection tests in SPF chickens, the permission of Ministry of Agriculture, Livestock and Supply (MAPA) to market a live attenuated vaccine formulated with a Brazilian variant strain (BR-1). The objective of this work was to evaluate, in commercial broilers, the protection induced by this new live attenuated vaccine when administered alone or combined with another live attenuated vaccine formulated with Massachusetts strain. For that, the systemic humoral immune response was measured by the commercial ELISA test, and the protective scores for tracheal ciliostasis, microscopic lesions and viral load by RT-qPCR were evaluated in the trachea, lungs and/or kidneys of the different groups of vaccinated birds against homologous (virulent Brazilian variant - BR-1) or heterologous (virulent Massachusetts strain) challenges. The results of this study showed that combined vaccination conferred a greater immune-protection characterized by lower tracheal ciliostasis scores, milder microscopic lesions and a lower and less persistent viral load after homologous challenge with BR-1 strain. Partial immune protection against the virulent strain BR-1 was also observed in the mono-vaccinated groups, either with the BR-1 vaccine or the Massachusetts vaccine, but no relevant protection was recorded for chickens vaccinated only with BR-1 against the challenge with virulent Massachusetts strain. In conclusion, the vaccine protocol combining the attenuated vaccines with the BR-1 and Massachusetts attenuated strains can be successfully used to induce more effective immuno-protective responses against Brazilian variant (BR-1) and Massachusetts IBV strains in commercial broilers.
Infectious Bronchitis Virus (IBV) is characterized by high genetic variability that generates a large number of antigenic and biological variants due to point mutations, insertions, deletions and recombination that may occur in various parts of the viral genome and especially in the S1 gene. The control of Infectious Bronchitis (IB) through vaccines thus becomes quite complex, but vaccination is still one of the most effective approaches to protection against IBV infection. Since the year 2000, Brazil has been presenting an increased incidence of IB outbreaks caused by variant strains classified as genotype I - lineage 11 (GI-11) or in genotype BR-1, and until 2016, only live attenuated vaccines containing the Massachusetts genotype were commercially available. In this year, one Brazilian pharmaceutical industry developed and achieved, on the basis of protection tests in SPF chickens, the permission of Ministry of Agriculture, Livestock and Supply (MAPA) to market a live attenuated vaccine formulated with a Brazilian variant strain (BR-1). The objective of this work was to evaluate, in commercial broilers, the protection induced by this new live attenuated vaccine when administered alone or combined with another live attenuated vaccine formulated with Massachusetts strain. For that, the systemic humoral immune response was measured by the commercial ELISA test, and the protective scores for tracheal ciliostasis, microscopic lesions and viral load by RT-qPCR were evaluated in the trachea, lungs and/or kidneys of the different groups of vaccinated birds against homologous (virulent Brazilian variant - BR-1) or heterologous (virulent Massachusetts strain) challenges. The results of this study showed that combined vaccination conferred a greater immune-protection characterized by lower tracheal ciliostasis scores, milder microscopic lesions and a lower and less persistent viral load after homologous challenge with BR-1 strain. Partial immune protection against the virulent strain BR-1 was also observed in the mono-vaccinated groups, either with the BR-1 vaccine or the Massachusetts vaccine, but no relevant protection was recorded for chickens vaccinated only with BR-1 against the challenge with virulent Massachusetts strain. In conclusion, the vaccine protocol combining the attenuated vaccines with the BR-1 and Massachusetts attenuated strains can be successfully used to induce more effective immuno-protective responses against Brazilian variant (BR-1) and Massachusetts IBV strains in commercial broilers.
Descrição
Palavras-chave
Bronquite infecciosa das galinhas, Ciliostase traqueal, Histopatologia, Linhagem GI-11, RT-qPCR, Vacina viva, Infectious bronchitis, Tracheal ciliostasis, Histopathology, GI-11 strain, Live vaccine