Protection against candidiasis by an immunoglobulin G3 (IgG3) monoclonal antibody specific for the same mannotriose as an IgM protective antibody

We previously reported that a liposome-mannan vaccine (L-mann) of Candida a lbicans induces production of mouse antibodies that protect against dissemi nated candidiasis and vaginal infection. Immunoglobulin M (IgM) monoclonal antibody (MAb) B6,1, specific for a C, albicans cell surface beta-1,2-manno triose, protects mice against both infections. Another IgM MAb, termed B6, which is specific for a different cell surface mannan epitope, does not pro tect against disseminated candidiasis. The B6,1 epitope is displayed homoge neously over the entire cell surface, compared to a patchy distribution of the B6 epitope, To determine if protection is restricted to an IgM class of antibody, we tested an IgG antibody. MAb C3,1 was obtained from L-mann-imm unized mice. By results of sodium dodecyl sulfate-polyacrylamide gel electr ophoresis analysis, capture enzyme-linked immunosorbent assay, and immunodi ffusion tests, MAb C3,1 is an IgG3 isotype, By epitope inhibition assays, w e determined that MAb C3.1 is specific for same mannotriose as MAb B6,1, As expected by the results of the inhibition assays, immunofluorescence micro scopy showed that the C3,1 epitope is distributed on the yeast cell surface in a pattern identical to that of the B6,1 epitope, Kidney CFU and mean su rvival times of infected mice pretreated with MAb C3,1 indicated that the a ntibody enhanced resistance of mice against disseminated candidiasis, Mice in pseudoestrus that were given MAb C3,1 prior to vaginal infection develop ed fewer vaginal Candida CFU than control animals that received buffered sa line instead of the antibody. The finding that an IgG3 antibody is protecti ve is consistent with our hypothesis that epitope specificity and complemen t activation are related to the ability of an antibody to protect against c andidiasis.