Utilização de ovinos para avaliação de vacinas recombinantes contra leptospirose animal

Abstract

Commercially available veterinary vaccines are composed of bacterins, and have limitations that impair their vaccine efficacy, since the bacteria exhibit fastidious, burdensome growth and confer immunity only to serovars antigenically related to those present in the vaccine formulation. In this scenario, recombinant vaccines become a promising alternative to bacterins, as they eliminate time-consuming and costly culture and, in theory, may confer protection against more than one serovar. LigAni, LigBrep and LipL32 proteins have been shown to promote protective immune response against homologous challenge in hamsters. However, several studies are carried out using hamsters as an experimental model and there is still no study using experimental animals as an experimental model to evaluate the immune response obtained through recombinant vaccines. Thus, the objective of this work was to evaluate recombinant antigens (LipL32, LigAni e LigBrep) associated with different adjuvants in the development of vaccines against animal leptospirosis, using sheep as an experimental model. For this, the project was divided into two stages. First, the pathogenesis of leptospira interrogans was evaluated using experimentally infected sheep. After evaluation of the experimental infection, the immune response obtained by sheep when vaccinated with formulations containing recombinant antigens and different adjuvants was evaluated. The results regarding the experimental infection showed that, despite the absence of clear symptomatology, it was possible to cause experimental infection in sheep, demonstrated by Polymerase Chain Reaction (PCR) and Microscopic Agglutination Test (MAT). In addition, it was possible to observe that the recombinant proteins LigAni, LigBrep and LipL32 have immunogenic properties, generating high titres of antibodies when coadministered with different adjuvants and using sheep as an experimental model. Therefore, it is concluded that sheep can be used as an experimental model in studies related to animal leptospirosis.