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Infect. Immun., Jul 1996, 2577-2584, Vol 64, No. 7
MJ Gomez, A Torosantucci, S Arancia, B Maras, L Parisi and A Cassone
A 65 kDa-constituent (MP65) of a whole-cell mannoprotein (MP) fraction of
Candida albicans was purified by immunoaffinity chromatography with
monoclonal antibodies directed against periodate-insensitive, protease-
sensitive MP epitopes, putatively polypeptide in nature. These antibodies
were obtained by immunization of mice with concanavalin A bead-coupled,
low-glycosylated MP from hyphal cells of C. albicans grown in the presence
of a subinhibitory dose of tunicamycin. The immunoaffinity-purified MP65
molecule had a pI of 4.1 and a protein/polysaccharide ratio of 1.8:1. It
was resistant to hydrolysis by endoglycosidase H, endoglycosidase F, or
N-glycoffanases but still reactive with concanavalin A. The polysaccharide
moiety of MP65 was composed exclusively of mannose and glucose at a ratio
of 12.7 to 1. The protein moiety showed numerous potential O-glycosidic
linkage sites as suggested by the high proportion of serine and threonine
(together accounting for more than 20% of the total amino acid composition)
and susceptibility to diluted alkali. This treatment and digestion with
alpha-mannosidase caused a reduction in the MP65 molecular mass to around
54 kDa. The N-terminal sequence of MP65 protein moiety was rich in alanine
and valine (7 of 13 amino acids) and did not show any significant homology
with deposited sequences in data banks. Purified MP65, at doses of a few
nanograms, induced extensive T-cell proliferation of human peripheral blood
mononuclear cells. This proliferation was specifically inhibited, in a
dose-response fashion, by the antigen-binding fragment of the monoclonal
antibody used for immunoaffinity purification. Overall, these results
highlight biochemical and molecular details of MP65, a main target of human
T- cell response to C.albicans.
Copyright © 1996, American Society for Microbiology
Purification and biochemical characterization of a 65-kilodalton mannoprotein (MP65), a main target of anti-Candida cell-mediated immune responses in humans
Department of Bacteriology, Istituto Superiore di Sanita, Rome, Italy.
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