Evaluation of the vaccine potential of antigenic fractions obtained in Leptospira interrogans serovar Copenhageni using hamsters as an animal model

Abstract

Leptospirosis, considered an important worldwide zoonosis represents a serious public health problem. Caused by pathogenic bacteria of the genus Leptospira, the number of infections in the world can reach one million per year. In Brazil, outbreaks occur mainly during rainy periods in metropolitan areas that have inadequate infrastructure, such a condition favors the proliferation of rodents that are considered the main reservoirs of the disease. The prevention of leptospirosis by vaccination is an alternative to control the spread of the disease. However, the vaccines available for leptospirosis are based on inactivated bacteria and immune protection is dependent on the production of antibodies against the specific lipopolysaccharides of each serovar. As a consequence, a classic T cell response is not activated and results in the need for an annual boost. The search for vaccine candidates that promote the activation of an immune memory response will contribute to the development of new vaccine strategies for the control of leptospirosis. Protein fractions obtained from cultured leptospires have been investigated recently, and demonstrated the ability to activate populations of CD4 T cells and ³´ T cells after stimulation of peripheral blood mononuclear cells from immunized cattle, suggesting the ability of these fractions to activate memory populations. As the use of a single major leptospira protein was not able to promote such a response, we believe that perhaps a set of proteins is necessary to promote this activation. Thus, clarifying whether animals immunized with these protein fractions would be able to activate the same profile of response and whether this response would result in protection after a challenge trial will be extremely important for the discovery of new vaccine targets and in the understanding of the protective immune responses involved in the control of leptospirosis.