Chemical structure and antigenic aspects of complexes obtained from epimastigotes of Trypanosoma cruzi

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Abstract
Cells of [the Chagas'' disease causing] T. cruzi, Y strain, were submitted to water extraction by successive freezing and thawing. Fractionation of soluble material on P-10 column gave an antigenic glycoprotein (fraction I) in which the carbohydrate portion (40%) contained galactose, mannose, glucose and xylose in a molar ratio of 35:13:1:1. It was electrophoretically homogeneous (Mr [molecular ratio] .apprx. 25000) and contained short chains of mannopyranosyl (23%) and galactopyranosyl (10%) nonreducing end units and 2-O-substituted mannopyranosyl units (19%). Extraction of the remaining cell fragments with phenol-water gave an antigenic CHCl3-MeOH-H2O-soluble fraction II (LPPG), which yielded a galactomannan (fraction III) (galactose and mannose in a molar ratio of 1:2.1) on degradation with hot aqueous NaOH-NaBH4. It contained end units of galactofuranose (25%) and 2-O-(5%), 3-O- (32%), and 2,3-di-O- (19%) substituted mannopyranosyl units. Galactofuranose was directly linked (1 .fwdarw. 3) to mannopyranose and not via a phosphorodiester bridge. .beta.-D-Galf-(1 .fwdarw. 3)-Me-.alpha.-D-Manp, in contrast with Me-.beta.-D-Galf, was effective in inhibiting the precipitin reaction between LPPG and antiserum raised against LPPG. Fraction IV, insoluble in CHCl3-MeOH-H2O, contained galactose and mannose in a ratio of 1.4:1. After degradation with hot aqueous NaOH-NaBH4, it gave a product (fraction V) containing galactose and mannose in a 1:2 ratio. Methylation analysis showed it to differ from fraction III since it contained a high proportion of nonreducing end units (41%) and 2-O-substituted units (16%) of mannopyranose.