Immunoprotection against systemic candidiasis in mice

We have previously described an immunosuppressive B cell mitogenic (ISM) protein, p43, produced by Candida albicans, which plays an important role in the survival of the microorganism in the host. The N-terminal amino acid sequence of p43 was found to be different from all amino acid sequences registered in updated protein databanks. Immunization of BALB/c mice with p43 partially neutralized the biological effects of this protein, namely depletion of bone marrow pre-B and B cells, the increased numbers of total and large B and CD4+ lymphocytes, and the non-specific polyclonal response of splenic IgG2a-, IgG2b- and IgM-secreting plaque forming cells. Immunization of BALB/c mice with p43 fully protected the mice against the fungal infection. In contrast, immunization with C. albicans sonicates (Cs) was not protective. Our data indicated that specific antibodies against p43 protected, whereas those against Cs facilitated C. albicans infection. Thus, the ratio between anti-p43 and anti-Cs antibody titres was much lower in the non-protected mice (Cs-immunized and control non-immunized) than in p43-immunized mice. Moreover, passive administration of specific anti-p43 antibodies significantly protected against fungal infection, whereas passive administration of specific anti-Cs antibodies markedly increased the susceptibility to C. albicans infection. These observations are discussed on the basis of alternative approaches of immunointervention.