The human pathogenic fungus Cryptococcus neoformans has a large polysaccharide (PS) capsule a
copious amounts of PS into cultures and infected tissues. The capsular PS is a major virulence fact
elicit protective antibody responses. PS recovered from culture supernatants has historically provid
and convenient source of material for structural and immunological studies. Two major assumption
studies are that the structural features of the exopolysaccharide material faithfully mirror those of c
that the isolation methods do not change PS properties. However, a comparison of exopolysacchari
two isolation techniques with capsular PS stripped from cells with gamma radiation or dimethyl su
revealed significant differences in glycosyl composition, mass, size, charge, viscosity, circular-dich
and reactivity with monoclonal antibodies. Our results strongly suggest that exopolysaccharides an
are structurally different. A noteworthy finding was that PS made by cetyltrimethylammonium bro
precipitation had a larger mass and a different conformation than PS isolated by concentration and
suggesting that the method most commonly used to purify glucuronoxylomannan alters the PS. He
method used to isolate PS can significantly influence the structural and antigenic properties of the p
findings have important implications for current views of the relationship between capsular PS and
exopolysaccharides, for the generation of PS preparations suitable for immunological studies, and f
formulation of PS-based vaccines for the prevention of cryptococcosis.
