Biomphalaria glabrata Hemolymph Lectins: Binding to Bacteria, Mammalian Erythrocytes, and to Sporocysts and Rediae of Echinostoma paraensei

Abstract

Polyclonal antibodies were raised in rabbits to two groups of diffusely staining M line Biomphalaria glabrata plasma polypeptides, of 150-210 and 70-120 kDa, designated as Group 1 molecules (G1M) and group 2 molecules (G2M), respectively. G1M and G2M are known to increase in abundance and to become more diverse following infection of B. glabrata with the digenetic trematode Echinostoma paraensei. These antibodies were used in conjunction with immunoblotting and slot blotting procedures to document binding of G1M/G2M from plasma of unexposed control snails (C plasma) or plasma from snails with 8-day infections of E. paraensei (I plasma) to various targets. Binding of G1M/G2M to both gram-positive and gram-negative bacteria, human A, B, and O and rabbit erythrocytes, and to sporocysts and rediae of E. paraensei was documented. Immunoblots revealed that erythrocytes are bound by a particular G2M band of 100-120 kDa present in I plasma that is in low concentration or lacking in C plasma. This explains previous results indicating that I plasma agglutinates all 4 erythrocytes examined whereas C plasma agglutinates only rabbit erythrocytes. More G1M/G2M binding to sporocysts occurred if I plasma rather than C plasma was used for incubations. Also, monosaccharide inhibition of G1M/G2M binding to sporocysts was observed in I plasma but not in C plasma. The results indicate that infection with E. paraensei induces production by B. glabrata of unique plasma polypeptides and that molecules present in I plasma can bind to the surfaces of non-self objects including E. paraensei larvae in a lectin-like fashion.