A RECOMBINANT CYSTEINE-RICH SECTION OF THE ENTAMOEBA-HISTOLYTICA GALACTOSE-INHIBITABLE LECTIN IS EFFICACIOUS AS A SUBUNIT VACCINE IN THE GERBIL MODEL OF AMEBIC LIVER-ABSCESS

The 170-kDa subunit of the galactose-inhibitable adherence lectin of E ntamoeba histolytica mediates attachment to colonic mucins and host ce lls. The DNA fragment encoding the 170-kDa subunit was produced by pol ymerase chain reaction (PCR) and divided into four sections by restric tion endonucleases. The third section (designated LC3, base pairs 2273 -3397) encodes a cysteine-rich fusion protein that was recognized by a dherence-inhibitory anti-lectin monoclonal antibodies and serum antibo dies from 95% of subjects with amebic liver abscess. Immunization of g erbils with purified recombinant LC3-encoded protein (10 mu g) with Ti termax adjuvant elicited a high-titer serum anti-LC3 IgG antibody resp onse and protective immunity against intrahepatic challenge with 0.5 X 10(6) virulent axenic trophozoites (strain HM1:IMSS; 71% vaccine effi cacy, P < .01). In summary, a recombinant cysteine-rich portion of the 170-kDa lectin subunit was highly antigenic, immunogenic, and effecti ve as a subunit vaccine in an experimental animal model of amebic live r abscess.