Chitosan and trimethyl chitosan chloride (TMC) as adjuvants for inducing immune responses to ovalbumin in mice following nasal administration

Chitosan of different molecular weights (Chi-P, MW = 2.7 × 105 g/mol and Chi-A, MW = 5.0 × 105 g/mol) and trimethyl chitosan chloride (TMC) of various degree of quaternization (DQ) including TMC-20, TMC-40 and TMC-60 were evaluated as adjuvants for inducing of immune responses to ovalbumin (OVA). OVA in solution and in alum were used as controls. Groups of BALB/c mice were immunized on days 0, 7 and 14. The IgG and IgA titers were examined on days 0, 13 and 21. It was found that for both days 13 and 21, Chi-A could elicit higher IgG responses to OVA than Chi-P. On day 13, OVA in TMC-40 induced IgG responses significantly higher than that in solution, Chi-P and TMC-60. Moreover, OVA in TMC-40 could induce IgG responses higher than OVA in alum. Although a significant difference was not observed at day 21, OVA in TMC-40 was shown to induce higher IgG responses than that in TMC-20, TMC-60 and solution. The IgA responses were the most pronounced on day 21. Again, Chi-A could elicite higher IgA responses than Chi-P and TMC-40 induced the highest IgA responses. In conclusion, these findings demonstrate that both MW of chitosan and DQ of TMC influence the level of immune induction. TMC-40 shows to be the most potent adjuvant for intranasal administration.