Influence of lectin inhibitors on Leishmania major growth and morphology

Gut lectins of the insect vectors play important roles in the transmission of pathogens. Galactosamine, a sandfly midgut lectin inhibitor, was previously demonstrated to increase the intensity of Leishmania infection in sandflies; it was suggested that this was due to the inhibition of sandfly midgut lectin. However, galactosamine might also enhance Leishmania growth in the sandfly. Therefore, the aim of this work was to study the effect of galactosamine and other carbohydrates on Leishmania in vitro. At 50 mM concentration, galactosamine inhibits growth of promastigotes, at 10 mM it induces morphological changes similar to that seen in infected sandflies. Glucosamine effect is less pronounced, galactose has no effect. This suggests that the effect of galactosamine on Leishmania differs in vivo and in vitro. Thus, galactosamine does not enhance Leishmania development in sandflies directly, but rather interferes with some aspect of sandfly physiology (e.g. proteinase and/or lectin activity).