Desenvolvimento de uma nova vacina veterinária de subunidade contra raiva
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Data
2020-02-19
Autores
Rocca, Mayra Pereira [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A vacinação contra a raiva canina e felina é a medida profilática mais eficaz para a prevenção de casos de raiva humana. No Brasil a campanha de vacinação de animais domésticos é realizada anualmente, a partir das primeiras 4 semanas de vida do animal. As vacinas utilizadas são constituídas de vírus inativado e adjuvante. A proteção é conferida por um nível de anticorpos elevados, pois uma resposta imune efetiva ao vírus da raiva depende de sua neutralização. Embora as vacinas estejam disponíveis há muitos anos, há uma evidente falha de cobertura devido à necessidade de reforços periódicos e eventuais problemas com as vacinas contra raiva administradas em campanhas, o que leva muitos proprietários a não vacinarem seus animais. Dessa forma, o desenvolvimento de novas vacinas contra a raiva deve visar o aumento da segurança dessas vacinas e facilitar o processo de administração das doses de reforço. A proposta deste estudo foi o desenvolvimento de um protótipo vacinal baseado na utilização de uma glicoproteína recombinante do envelope do vírus da raiva (RVGP). Essa glicoproteína, utilizando um sistema de vetor viral (SFV-RVGP) e sendo expressa em sistema de células S2 amplamente caracterizado, demonstrou ter propriedades imunogênicas em ensaios preliminares. Diferentes preparações, combinadas ou não com adjuvantes, e diferentes vias foram testadas em modelo animal estabelecido e avaliadas frente ao desafio intracerebral, verificando por meio de testes sorológicos (ELISA e soroneutralização) se os níveis necessários para proteção foram atingidos. Resultados mostraram que tanto a imunização com RVGP de células S2 como com SFV-RVGP são capazes de proteger camundongos contra o desafio viral. A utilização de adjuvantes juntamente com a proteína recombinante se mostrou necessária, tendo sido testados MPLA, sílica (SBA-15) e ISCOM (complexos imunoestimulantes), sendo este último o mais eficiente.
Vaccination against canine and feline rabies is the most effective prophylactic measure for preventing cases of human rabies. In Brazil, the domestic animal vaccination campaign is carried out annually, from the first 4 weeks of the animal's life. Available veterinary Rabies vaccines are composed of inactivated viruses with adjuvant. High level of neutralizing antibodies directly correlates with protection. Although Rabies vaccines have been available for many years, there is a clear lack of coverage due to the need for periodic boosters and potential problems with campaign-administered rabies vaccines, which makes many owners fail to meet their pet vaccination schedule. Thus, the development of new rabies vaccines should aim at increasing the safety of these vaccines and facilitating the booster administration process. The purpose of this study was to develop a vaccine prototype based on the use of a recombinant rabies virus glycoprotein (RVGP). Recombinant RVGP expressed in vivo by using a viral vector system (SFV-RVGP) or being expressed in a widely characterized S2 cell system, have shown immunogenic properties in preliminary experiments. Different preparations, combined or not with adjuvants, and different routes were tested in an established animal model. Immunogenicity evaluated by survival against intracerebral challenge and by serological tests (ELISA and seroneutralization). Results showed that both the RVGP produced in insect cells and the SFV-RVGP system were able to protect mice against viral challenge (CVS). The combination of adjuvants was important for the glycoprotein immunogenicity. Adjuvants as MPLA, silica (SBA-15) and ISCOM (immunostimulant complexes) were tested, with ISCOM showing more efficiency.
Vaccination against canine and feline rabies is the most effective prophylactic measure for preventing cases of human rabies. In Brazil, the domestic animal vaccination campaign is carried out annually, from the first 4 weeks of the animal's life. Available veterinary Rabies vaccines are composed of inactivated viruses with adjuvant. High level of neutralizing antibodies directly correlates with protection. Although Rabies vaccines have been available for many years, there is a clear lack of coverage due to the need for periodic boosters and potential problems with campaign-administered rabies vaccines, which makes many owners fail to meet their pet vaccination schedule. Thus, the development of new rabies vaccines should aim at increasing the safety of these vaccines and facilitating the booster administration process. The purpose of this study was to develop a vaccine prototype based on the use of a recombinant rabies virus glycoprotein (RVGP). Recombinant RVGP expressed in vivo by using a viral vector system (SFV-RVGP) or being expressed in a widely characterized S2 cell system, have shown immunogenic properties in preliminary experiments. Different preparations, combined or not with adjuvants, and different routes were tested in an established animal model. Immunogenicity evaluated by survival against intracerebral challenge and by serological tests (ELISA and seroneutralization). Results showed that both the RVGP produced in insect cells and the SFV-RVGP system were able to protect mice against viral challenge (CVS). The combination of adjuvants was important for the glycoprotein immunogenicity. Adjuvants as MPLA, silica (SBA-15) and ISCOM (immunostimulant complexes) were tested, with ISCOM showing more efficiency.
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Palavras-chave
Raiva, Vacina, RVGP, Adjuvante, RFFIT, FAVN, Reforço vacinal