Studies on a haemolymph lectin isolated from Rhodnius prolixus and its interaction with Trypanosoma rangeli

We demonstrated that in Rhodnius prolixus haemocyte monolayers, both Trypan osoma cruzi and Trypanosoma rangeli are capable of inducing haemocyte/paras ite clump formation. We also purified, by one-step affinity chromatography, a haemolymph galactoside-binding lectin from R. prolixus which we believe could play an important role in the development of T. rangeli in the haemoc oel of the insect vector. This lectin markedly enhanced the activation of c lump formation by T. rangeli in R. prolixus haemocyte monolayers, with an i ncrease in clump size and haemocyte aggregation. The haemolymph lectin also significantly affected the motilitity and survival of T. rangeli culture s hort forms, but not the long forms, when they were incubated in vitro. This molecule is also one of the few described in insects with agglutination ac tivity independent of calcium ions. The partial N-terminal amino acid seque nce of this lectin demonstrated similarity to a bacterial xylulose kinase a nd in preliminary experiments the purified haemolymph lectin phosphorylated a tyrosine kinase substrate in a dose-dependent manner. The possible role of this haemolymph lectin in the Life cycle of T. rangeli is discussed. (C) 1999 Academic Press.