Cryptococcus Neoformans Polysaccharide: Studies of Serologic Properties and Role in Infection

Abstract

A complement fixation test for polysaccharides of Cryptococcus neoformans was found to detect concentrations of as little as 0.25 to 1.0 µg/ml, depending on the preparation of polysaccharide. The test was less sensitive toward other polysaccharides but did react with those from Hansenula minuta, Hansenula capsulata, Cryptococcus laurentii and Diplococcus pneumoniae. The test was used to demonstrate that cryptococcal polysaccharide injected intracisternally into rabbits disappeared rapidly from the cerebrospinal fluid but appeared and persisted for weeks in the bloodstream. Cryptococcal polysaccharide injected i.v. into rabbits or mice also persisted in the bloodstream for weeks. The inability of mice to clear this foreign antigen from their bloodstream was felt to help account for the high titers of cryptococcal polysaccharide found in the mice infected with C. neoformans. An i.v. injection of polysaccharide into mice caused no gross toxicity but hastened mortality if the mice were infected subsequently with a large inoculum of C. neoformans.