Antígeno inativado de Clostridium Novyi tipo B em emulsão W/O: uma prova de conceito em camundongos Swiss visando o controle de necrose hepática de ruminantes

Abstract

Brazilian cattle breeding has great emphasis on the national market. Diseases that affect herds compromise the market as well as generate great economic losses. Clostridium novyi type B causes hepatic necrosis in cattle through the production of alpha toxin, a potent exotoxin that reduces productivity through changes such as hemoglobinuria, reduced appetite, fever, lethargy, decreased milk and stool production. Containing the causative micro-organism becomes a necessary quest both economically and socially. However, control of the disease is still performed by vaccines formulated with multiple antigens. The emulsion may be a promising alternative for the improvement of antigen adsorption in vaccine formulations. Swiss strain mice were used to evaluate clinical aspects and validate results regarding the composition of a new vaccine formulation containing Montanide ISA 61 VG adjuvant and C. novyi inactivated antigen. Characterization and antigenicity tests indicated the presence of the alpha toxin protein in the evaluated composition. The immunogenicity of antigen inactivated in W / O emulsion (water / oil) was verified and the ratio employed (40/60) showed to be ideal in the use of multiple antigens, presenting innocuousness, product stability, controlled release and stimulation of the immune response. The determination of the antigen concentration was investigated by the active antigen ratio and inactivated with sera from sick animals, since the vaccine efficacy was 40%. The suitability of the inactivated alpha toxin concentration in the emulsion was shown to be necessary to achieve better animal protection values. Hemogram, biochemical and liver, spleen and thigh morphology contributed to elucidate the effects of the emulsion and to verify hepatic necrosis in the nonimmunized groups, in addition to suggesting advances in the adsorption of vaccines. The results allowed the establishment of a murine model of C. novyi infection with future applications related to the vaccine production with multiple emulsified antigens to control clostridia.