Imunogenicidade de proteínas recombinantes de Erysipelothrix rhusiopathiae: proteção em um modelo murino

Abstract

Erysipelothrix rhusiopathiae is a Gram-positive bacillus that causes swine erysipelas, which leads to the loss and poor development of pigs. Existing vaccines for immunization against erysipelas are made up of killed or attenuated bacteria and, according to reports in the literature, have failed to provide protection, leading to the search for other components that could form a new vaccine against this disease. The surface protein SpaA of E. rhusiopathiae alredy has been reported to induce a host immune response against the bacteria, and hsp70 DnaK has been shown to be an antigenic protein of the bacteria. This work evaluated the immunogenicity and protection induced by the recombinant proteins SpaA and DnaK from E. rhusiopathiae in a murine model. The model was designed in 6 groups of mice that received two doses (subcutaneous and intramuscular) of 40 µg and 100 µg of recombinant proteins. The proteins were evaluated separately and together, compared with a commercial vaccine and with the no-vaccination condition. The proteins were evaluated separately and together, compared with a commercial vaccine and the without vaccination condition. 21 days after the last dose, mice were challenged with a virulent strain of E. rhusiopathiae and serum was collected to assess antibodies, peripheral blood cells were counted, and spleen and kidney tissues were analyzed for the presence of E. rhusiopathiae by colony count. Finally, two survival curves were performed, evaluating the protection induced by the proteins. The results showed that IgG antibodies increased in the serum of animals inoculated with the proteins, which also had bacterial proliferation reduced in the spleens and kidneys evaluated, and presented a significant delay in the symptoms of the disease in this immunization model. These results suggest that the DnaK and SpaA proteins from E. rhusiopathiae have immunogenic potential and can modulate the development of the disease, as assessed in the murine model.