Vaccine potential of 56-66 kDa protease secreted by Entamoeba histolytica.

Excretory/secretory (ES) antigens and sub-cellular fractions of E. histolytica (HM1:IMSS strain) were tested for the presence of common proteases using substrate gel electrophoresis. We obtained two E. histolytica proteases (56-66 kDa and 29 kDa) from ES material, soluble components and plasma membrane. Protease 56-66 kDa from ES antigen was selected for immunizing hamsters because it gave a consistent broad band. We observed 62.5 per cent protection in immunized animals, compared to 0 per cent in unimmunized controls. Although all vaccinated golden hamsters showed high antibody response, there was no correlation between antibody titres and protection. 56-66 kDa ES protease could thus prevent disease and could be a candidate molecular vaccine against amoebiasis.