We previously reported that a
liposome-
mannan vaccine (L-mann) of Candida albicans induces production of mouse
antibodies that protect against disseminated
candidiasis and vaginal
infection.
Immunoglobulin M (
IgM)
monoclonal antibody (MAb) B6.1, specific for a C. albicans cell surface beta-1,2-mannotriose, protects mice against both
infections. Another
IgM MAb, termed B6, which is specific for a different cell surface
mannan epitope, does not protect against disseminated
candidiasis. The B6.1
epitope is displayed homogeneously 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-immunized mice. By results of
sodium dodecyl sulfate-
polyacrylamide gel electrophoresis analysis, capture
enzyme-linked
immunosorbent assay, and immunodiffusion tests, MAb C3.1 is an
IgG3 isotype. By
epitope inhibition assays, we determined that MAb C3.1 is specific for same
mannotriose as MAb B6. 1. As expected by the results of the inhibition assays, immunofluorescence microscopy 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 survival times of infected mice pretreated with MAb C3.1 indicated that the antibody enhanced resistance of mice against disseminated
candidiasis. Mice in pseudoestrus that were given MAb C3.1 prior to vaginal
infection developed fewer vaginal Candida CFU than control animals that received buffered saline instead of the antibody. The finding that an
IgG3 antibody is protective is consistent with our hypothesis that
epitope specificity and complement activation are related to the ability of an antibody to protect against
candidiasis.