RESUMEN
Burkholderia mallei is an aerobic, Gram-negative, non-motile bacillus. As an obligate mammalian pathogen, it primarily affects solipeds. Although rarely transmitted to humans, the disease it causes, glanders, is classified as a zoonosis. The bacterium was officially eradicated in Brazil in 1969; however, it reemerged after three decades. This study aims to assess the virulence of a specific B. mallei strain, isolated in Brazil, in BALB/c mice through intranasal infection. The strain, B. mallei BAC 86/19, was obtained from the tracheal secretion of a young mare displaying positive serology but no clinical signs of glanders. Post-mortem examinations revealed macroscopic lesions consistent with the disease, however. In mice, the LD50 was determined to be approximately 1.59 × 105 colony-forming units (CFU)/animal. Mice exposed to either 0.1 × LD50 or 1 × LD50 displayed transient weight loss, which resolved after three or five days, respectively. B. mallei persisted within the liver and lung for five days post-infection and in the spleen for seven days. These findings underscore the detectable virulence of the Brazilian B. mallei BAC 86/19 strain in mice, which are relatively resilient hosts. This research points to the importance of the continued investigation of the virulence mechanisms and potential countermeasures associated with B. mallei infections, including their Brazilian isolates.
RESUMEN
Considerando as limitações dos atuais métodos de controle contra a anaplasmose bovina, o desenvolvimento de uma vacina efetiva se faz necessário. A partir do advento da análise genômica e proteômica, novas proteínas de membrana de Anaplasma marginale foram identificadas como possíveis candidatas a componentes de uma vacina, tais como, VirB9, VirB10 e Fator Termo Instavél de Elongação de Peptídeos (EF-Tu). Embora estas proteínas ainda não estejam bem caracterizadas na membrana de A. marginale, a produção destas na forma recombinante (rVirB 9, rVirB10 e rEF-Tu) tem sido realizada, mas as mesmas ainda não foram exploradas em formulações vacinais. Neste trabalho, avaliou-se o uso de rVirB9, rVirB10 e rEF-Tu emulsionadas em adjuvante Montanide em camundongos. Nas condições testadas, verificou-se a indução de forte resposta imune humoral com a produção de IgG1 e IgG2a, sendo que as proporções dos níveis de produção destas subclasses indicam predomínio de IgG1. Entretanto, esplenócitos de animais, que foram injetados com rVirB9 ou rVirB10, produziram interferon-gama acima do limite de detecção do ensaio após estimulação in vitro, sinalizando assim resposta celular específica. Assim, novas avaliações serão realizadas com a finalidade de modular o perfil de resposta imune obtido em bovinos e avaliar a proteção contra A. marginale.
Considering the limitations of current methods of anaplasmosis control, the development of a more effective vaccine is required. Previous studies, using proteomic and genomic approaches, have identified new membrane proteins in Anaplasma marginale that may be vaccine candidates. These include VirB9, VirB10 and elongation factor-Tu (EFTu). Although the role of these proteins in the membrane of A. marginale has not been properly characterized, production of the recombinant proteins rVirB9, rVirB10, and rEF-Tu has been achieved. However, these recombinant proteins have not yet been exploited in vaccine formulations. The present study describes the use of rVirB9, rVirB10 and rEF-Tu, emulsificated in adjuvant Montanide, in mice. A strong humoral immune response was induced under these conditions, with both IgG1 and IgG2a production. The IgG2a/IgG1 ratios revealed a predominance of IgG1. However, splenocytes of the animals that received rVirB9 or rVirB10 produced high levels of gamma interferon after in vitro stimulation, indicating a specific cellular immune response to these proteins. Therefore, further studies are required to adjust the profile of the immune response in order to perform tests of protection against A. marginale in cattle.
