RESUMO
Toxoid vaccines can provide protective immunity against clostridial diseases. Since the duration of the toxoid vaccine immunogenicity is short, these vaccines need to contain an adjuvant. The nanoparticles of chitosan can stimulate humoral and cell-mediated immune responses. In the present study, the effect of chitosan nanoparticles was investigated on the immunogenicity of the pentavalent clostridial toxoid vaccine containing Clostridium perfringens types D, C, and B, Clostridium septicum, as well as Clostridium novyi. Rabbits were immunized by two injections with 3-week intervals and checked clinically and through autopsy 2 weeks after the last injection. Hematological changes were investigated during immunization, including the changes of white and red blood cell counts, hemoglobin, packed cell volume, platelet, neutrophil, lymphocyte, eosinophil, basophile, monocyte, and Neut/Lymph. Biochemical factors, namely creatinine, blood urea nitrogen, glucose, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total protein, and albumin, were also studied. The changes in immune responses during the immunization period were investigated through indirect enzyme-linked immunosorbent assay (ELISA). The results of ELISA showed that chitosan significantly enhanced immunogenicity when accompanied with in the pentavalent clostridial toxoid vaccine. During the immunogenicity period and following that, no changes were observed in clinical behavior and internal organs after autopsy. The hematological and biochemical factors were reported with no significant pathologic changes during immunization in the control and vaccinated groups (p <0.05). The obtained findings revealed that the toxoid vaccines could not induce significant physiological changes in the body. The vaccine containing chitosan could stimulate humoral immunity 2-3 times higher than the nonchitosan vaccine. The humoral immune response was significantly duplicated due to the chitosan effect. Chitosan not only had no local or general side effects but also could be a good help with the enhancement of the immune system; therefore, it can be recommended as an appropriate safe adjuvant in the development of toxoid vaccines.
