Influence of adjuvants on the ability of anti-Tbp antibodies to block transferrin binding, iron uptake and growth of Neisseria meningitis

To evaluate the effect of five adjuvants on the ability of specific anti-TbpA/B to block iron uptake in Neisseria meningitidis. Transferrin binding complexes (TbpA/B) purified from a TbpB isotype II Neisseria meningitidis strain were used to obtain sera with five different adjuvant formulations in mice in order to test the effect of the adjuvant on the ability of specific anti-TbpA/B antibodies to block transferrin binding, iron uptake and growth by meningococci. Levels of anti-TbpA/B antibodies were relatively low (1:125 in most cases), the highest being obtained with the RAS adjuvant (1:3125). Despite the relatively low responses, all sera were able to significantly inhibit transferrin binding, iron uptake and growth in the homologous strain. Nevertheless, the effect on a strain with a TbpB isotype different from that of the immunizing strain was almost nil, a result in keeping with the described division of the meningococci into at least two TbpB groups (isotypes I and II). In contrast to previous results for another important meningococcal protein, FbpA, the use of various adjuvants in the immunization of mice with TbpA/B complexes did not produce differences in the immune responses elicited, except in relation to antibody titers.