An essentially synthetic liquid medium for Entamoeba histolytica

Immunogenicity and protective efficacy of heparan sulphate binding proteins of Entamoeba histolytica in a guinea pig model of intestinal amoebiasis

Entamoeba histolytica infection is associated with considerable morbidity and mortality in the form of intestinal and extraintestinal amoebiasis. No vaccine is yet available for amoebiasis. Heparan Sulphate Binding Proteins (HSBPs) from E. histolytica were evaluated for immunogenicity and protective efficacy in a Guinea pig model. Animals were immunized subcutaneously with 30μg of HSBP by three weekly inoculations. The immunogenicity of HSBP was determined by antibody response (IgG, IgM and IgA), splenocyte proliferation assay and in vitro direct amoebicidal assay with splenic lymphocytes and monocytes from vaccinated and control animals. The efficacy of the vaccine was evaluated by challenge infection to vaccinated and control animals by intra-caecal inoculation of E. histolytica trophozoites and comparing gross and histopathological findings in caeca of these animals. HSBP was found to induce specific anti-amoebic response as seen by specific antibody production and direct amoebicidal activity of splenocytes. The vaccine also showed partial protection against challenge infection in vaccinated animals as shown by mild/absent lesions and histopathological findings.

Observations on the culture and maintenance of a free-living amoeba

A free-living amoeba isolated from creek water could be grown at 24 °C. on a solid malt agar medium together with a pure culture of a motile Gram-negative bacillus, isolated from the same sample of water. The bacilli apparently served as the sole source of food for the trophozoites, the malt in the medium being-utilized by the bacilli for their own growth. In addition, the encysted form has been maintained on this medium at 24 °C. for the past 12 months and at 4 °C. for 10 months. Transfers to fresh medium of cysts from such cultures yielded numerous trophozoites after 12 hr. incubation at 24 °C, provided that metabolically active bacilli were present.