Emulsões de polissacarídeo bacteriano como adjuvantes em vacinas recombinantes

Abstract

Vaccines proved to be effective in preventing diseases that previously had high morbidity and mortality. They should be administered in advance of exposure to pathogens, with sufficient time to induce antigen-specific immune memory. Vaccination with recombinant antigens, which are generally less immunogenic, results in modest activation of T lymphocytes and low induction of antibodies. To overcome this deficiency, these antigens are incorporated into adjuvant formulations in order to enhance the vaccine immune response. In this study an adjuvant (EPB) was developed in the form of a triple emulsion, water/oil/water, using the bacterial polysaccharide xanthan gum and the Montanide ISA 50 V2® oil. The emulsion was innocuous for mice, horses and cattle, showing seringability, and remained stable for 6 months under refrigeration (4 °C). Its immunogenic efficiency was evaluated against the recombinant Equi Merozoite Antigen (rEMA-2) from Theileria equi and Epsilon Toxin (rETX) from Clostridium perfringens. Experimental groups vaccinated with EPB emulsified to the rEMA-2 antigen from both mice and horses showed significantly higher total serum IgG levels when compared to groups vaccinated with aluminum hydroxide (p <0.05) and EPB alone (p <0.01). IgG1 and IgG2a isotypes of the mice serum pools collected on days 28 and 60 were evaluated by ELISA. On day 60 a significant (p <0.05) increase of IgG2a levels was observed in the vaccinated group with EPB in relation to day 28, suggesting a modulation for a Th1 response. The bovines vaccinated with rETX emulsified with PSB had serum titers of total IgG against rETX significantly higher (p <0.05) than the group that received aluminum hydroxide as an adjuvant. A significant increase (p <0.05) in cytokines IL-2 (3.5 x), IL-15 (3.8 x) and IL-17 (2.0 x) mRNA transcription was observed in animals vaccinated with the rETX protein emulsified with PSB in peripheral leukocytes when stimulated with the rETX protein and compared to the aluminum hydroxide group. The results of this study demonstrated that the triple emulsion adjuvant developed is innocuous, stable and has a promising action as a vaccine adjuvant with the recombinant proteins tested.