The development of safe, novel adjuvant is necessary to maximize the efficacy of new and/or available vaccines. In this study, three different molecular weights of chitosan (low, medium, high) were evaluated as immunopotentiators/adjuvants of inactivated rabies vaccine in white Norway rats as an experimental model. Two concentrations (1.5% & 3% w/v) of each chitosan type were used in final concentration 5 mg/ml and 10 mg/ml. Results showed that lymphocyte proliferation
were significantly elevated (P < 0.05) in all chitosan vaccinated rats compared to aluminum hydroxide gel vaccinated one. All three type of chitosan produced accelerated and enhanced effects on rabies-neutralizing antibody responses in vaccinated groups. Increases in antibody titers together with lymphocytes proliferation responses revealed that chitosan induced both humoral and cell-mediated immune responses. When compared with aluminum hydroxide vaccine
adjuvant, chitosan was superior to aluminum hydroxide. The conclusion of these results suggested that chitosan with different MW had a strong potential to increase both cellular and humoral immune responses and that chitosan may be a promising and efficacious adjuvant candidate suitable for inactivated rabies vaccine.