Dados do Trabalho

Título

EVALUATION OF THE IMMUNOPROTECTIVE POTENTIAL OF LEPTOSPIRAL DERIVED ANTIGENIC FRACTIONS IN HAMSTER MODEL

Introdução

Leptospirosis is considered an important worldwide zoonosis. 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. As a consequence, a classic T cell response is not activated and annual booster is necessary. Protein fractions obtained from cultured leptospires were investigated recently, and the ability to activate populations of CD4 T cells and gamma delta T cells after stimulation of peripheral blood mononuclear cells from immunized cattle was demonstrated.

Objetivo (s)

To verify whether hamsters immunized with the protein fractions can activate a protective response profile after a challenge assay.

Material e Métodos

Animals were immunized with two doses of fractions containing secreted proteins and SDS-soluble proteins adsorbed to aluminum hydroxide adjuvant, challenged with virulent leptospires and monitored for 2 weeks to survival analysis.

Resultados e Conclusão

We show that protective efficacy of these fractions was dose dependent. Immunized animals with a low antigen concentration did not exhibit any level of protection, while those animals immunized with a higher concentration of fractions exhibited from 60 to 100% of protection, in two independent experiments. Although we have observed a high protection level, secreted proteins immunized animals showed a high frequency of renal colonization. The number of positive cultures for leptospires was lower in the SDS-soluble proteins immunized animals, but only in the first experiments. Nevertheless, when the level of serum creatinine was evaluated, we observed that some animals showed a low amount of creatinine when compared with control group, which suggests that these animals had a minor kidney damage. All immunized animals produced a higher amount of IgG antibodies after second vaccine dose and similar to positive control group the response was exclusive IgG2/3. We showed that leptospiral derived antigenic fractions are able to protect hamsters against leptospirosis infection. However, the reason by which hamster still present renal colonization deserve to be further investigated.

Palavras-chave

Leptospira, leptospirosis, vaccine, antigenic fractions

Agradecimentos

FAPESP, CNPq, Fundação Butantan