Amoebiasis is due to invasion of the intestinal wall by the protozoan parasite Entemoeba histolytica. Amoebic colitis results from ulcerating mucosal lesions caused by the release of parasite-derived hyaluronidases and proteases. Hepatic infection occurs as a consequence of entry of the parasite into the afferent bloodstream. The disease is prevalent throughout the developing nations of the tropics, at times reaching a prevalence of 50% of the general population and is estimated to cause more than 100 000 deaths per year.
Evidence from a cohort of Bangladeshi children suggests that mucosal IgA directed against the major amoebic adherence molecule, a 170 kD lectin, correlates with resistance to reinfection with E. histolytica. Gerbils immunized with this lectin antigen were reported to show significant decrease of liver abscesses following parasite challenge, suggesting that a subunit vaccine might elicit protective immunity.