RESUMO
Bluetongue virus (BTV) is an economically important Orbivirus transmitted by biting midges to domestic and wild ruminants. The need for new vaccines has been highlighted by the occurrence of repeated outbreaks caused by different BTV serotypes since 1998. The major group-reactive antigen of BTV, VP7, is conserved in the 26 serotypes described so far, and its role in the induction of protective immunity has been proposed. Viral-based vectors as antigen delivery systems display considerable promise as veterinary vaccine candidates. In this paper we have evaluated the capacity of the BTV-2 serotype VP7 core protein expressed by either a non-replicative canine adenovirus type 2 (Cav-VP7 R0) or a leporipoxvirus (SG33-VP7), to induce immune responses in sheep. Humoral responses were elicited against VP7 in almost all animals that received the recombinant vectors. Both Cav-VP7 R0 and SG33-VP7 stimulated an antigen-specific CD4+ response and Cav-VP7 R0 stimulated substantial proliferation of antigen-specific CD8+ lymphocytes. Encouraged by the results obtained with the Cav-VP7 R0 vaccine vector, immunized animals were challenged with either the homologous BTV-2 or the heterologous BTV-8 serotype and viral burden in plasma was followed by real-time RT-PCR. The immune responses triggered by Cav-VP7 R0 were insufficient to afford protective immunity against BTV infection, despite partial protection obtained against homologous challenge. This work underscores the need to further characterize the role of BTV proteins in cross-protective immunity.
Assuntos
Antígenos Virais/genética , Vírus Bluetongue/genética , Bluetongue/imunologia , Expressão Gênica , Vetores Genéticos/genética , Proteínas do Core Viral/genética , Animais , Anticorpos Antivirais/sangue , Anticorpos Antivirais/imunologia , Antígenos Virais/imunologia , Bluetongue/prevenção & controle , Bluetongue/virologia , Vírus Bluetongue/imunologia , Linhagem Celular , Cricetinae , Reações Cruzadas/imunologia , Cães , Feminino , Imunidade Celular , Imunização , Masculino , Coelhos , Ovinos , Linfócitos T/imunologia , Linfócitos T/metabolismo , Proteínas do Core Viral/imunologia , Vacinas Virais/genética , Vacinas Virais/imunologiaRESUMO
Safe and efficient vaccination is important for rabies prevention in domestic animals. Replicative vectors expressing the rabies virus glycoprotein, derived from canine adenovirus have been reported to be promising vaccines in various animal models. In this paper we compare the potential of a replicative and a non-replicative vector, both based on canine adenovirus type 2 and expressing the rabies glycoprotein. Upon inoculation in sheep, immune responses against the rabies virus protein elicited by recombinant vectors were monitored. All immunised sheep produced a rapid and potent neutralizing antibody response against rabies virus after a single inoculation of either replicative or non-replicative recombinant canine adenovirus type 2. In addition, the non-replicative vector expressing the rabies glycoprotein stimulated antigen-specific CD4(+) and CD8(+) lymphocyte proliferation as well as IFN-γ production. These results suggest that vectors derived from canine adenovirus 2 could be considered for the development of promising vaccines in the ruminant species.