Protective immunity to amebiasis: new insights and new challenges.

Amebiasis, infection with the protozoan parasite Entamoeba histolytica, is the third leading cause of death from parasitic diseases. Despite its importance, we know little about protective immunity to amebiasis. Now, studies from a cohort of children in Bangladesh have provided some critical insights into immunity to intestinal amebiasis. Children with mucosal IgA antibodies to the amebic adherence lectin were found to be resistant to reinfection with E. histolytica. However, immunity was short-lived, and approximately 20% of children in the cohort had a second episode of E. histolytica infection during the study period. Theses findings indicate that immunity to amebiasis can develop in some children after intestinal infection, but protective immunity may be transient, and its importance in preventing disease remains to be established.