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

Cells of Trypanosoma cruzi, Y strain, were submitted to water extraction by successive freezing and thawing. Fractionation of soluble material on a P-10 column gave an antigenic glycoprotein (fraction I) whose carbohydrate portion (40%) contained galactose, mannose, glucose, and xylose in a molar ratio of 35:13:1:1. It was electrophoretically homogeneous (Mr approximately 25 000) 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 leads to 3) to mannopyranose and not via a phosphorodiester bridge. beta-D-Galf-(1 leads to 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.