Vaccination of Mice with Virulence-Associated Protein G (VapG) Antigen Confers Partial Protection against Rhodococcus equi Infection through Induced Humoral Immunity

Autor(es)

Trevisani, Marcel M. ; Hanna, Ebert S. ; Oliveira, Aline F. ; Cardoso, Silvia A. ; Roque-Barreira, Maria C. ; Soares, Sandro G.

• Tipo de documento: Artigo Científico
• Fonte: FRONTIERS IN MICROBIOLOGY; v. 8, MAY 11 2017.
• Citações Web of Science: 0

Resumo

Rhodococcus equi is a facultative intracellular bacterium causing severe pyogranulomatous pneumonia, ulcerative enterocolitis, and mesenteric lymphadenopathy in foals aged less than 6 months. Less frequently, this pathogen affects various other species, such as pigs, cattle, cats, and even humans. Although rhodococcosis is treated with a combination of antimicrobial agents, resistance is developed in some cases, and thus, antimicrobial susceptibility must be monitored and managed. Considering these limitations of the current therapy and unavailability of a vaccine to prevent the disease, research is particularly focused on the development of an effective vaccine against rhodococcosis. Most vaccines undergoing development utilize the virulence-associated protein (Vap) A antigen, which was identified previously as a key virulence factor of R. equi. Nevertheless, other proteins, such as VapG, present in most virulent R. equi strains, are also encoded by vap genes located on the R. equi bacterial virulence plasmid. In the present study, we evaluated the effect of VapG immunization on the survival of R. equi-challenged mice. We used attenuated Salmonella as a carrier for VapG (Salmonella-vapG+), a procedure previously adopted to develop a VapA-based vaccine. We observed that vaccination with Salmonella-vapG+ induced both an increased IFN-gamma, IL-12, and TNF-alpha production, and a decreased bacterial burden in organs of the R. equi-challenged mice. Nevertheless, Salmonella-vapG+ vaccination protected only 50% of the mice challenged with a lethal dose of R. equi. Interestingly, we observed an increased frequency of B cells in the spleen of Salmonella-vapG+-vaccinated mice and showed that Salmonella-vapG+-vaccinated R. equi-challenged B-cell-knockout mice did not reduce the bacterial burden. Given these results, we discussed the potential role of the humoral immune response induced by Salmonella-vapG+ vaccination in conferring protection against R. equi infection, as well as the employment of VapG antigen for obtaining hyperimmune plasma to prevent rhodoccocosis in young foals. (AU)

• Processo FAPESP: 13/24201-5 - Determinação da via de indução de morte autofágica ativada por lectina visando a sua aplicação na identificação de novos alvos para drogas no tratamento de leucemias
• Beneficiário: Sandro Gomes Soares
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 06/60941-0 - Escalonamento do processo de produção de vacina recombinante contra Rhodococcus equi
• Beneficiário: Silvia Almeida Cardoso
• Modalidade de apoio: Auxílio à Pesquisa - Pesquisa Inovativa em Pequenas Empresas - PIPE