SEROLOGIC REACTIVITY TO PURIFIED RECOMBINANT AND NATIVE 29-KILODALTONPERIPHERAL MEMBRANE-PROTEIN OF PATHOGENIC ENTAMOEBA-HISTOLYTICA

The 29-kDa peripheral membrane protein of Entamoeba histolytica has re cently been demonstrated to have epitopes on pathogenic clinical isola tes which were not detected by monoclonal antibodies on nonpathogenic isolates. To analyze the serological response to this protein, we test ed 93 serum specimens (from 33 patients with amebic liver abscess, 7 p atients with colitis, 2 patients with ameboma, 18 individuals harborin g a nonpathogenic zymodeme strain, 10 healthy Mexican migrant workers, and 23 healthy controls) by enzyme-linked immunosorbent assay (ELISA) using immunoaffinity-purified native or recombinant protein. When tes ted by ELISA with the native antigen, 79% (26 of 33) of the serum spec imens from patients with amebic liver abscess, 4 of 9 serum specimens from symptomatic patients with colitis or ameboma, and serum from one migrant worker were positive. None of the 18 subjects harboring a nonp athogenic strain or 23 control individuals were seropositive to the na tive antigen (sensitivity, 71%; specificity, 98%). Of 30 serum specime ns from patients with amebic liver abscess tested with recombinant ant igen, 27 were seropositive (90%). In addition, six patients with colit is or ameboma and two individuals who harbored a nonpathogenic strain were seropositive to the recombinant antigen. One healthy Mexican migr ant worker tested positive by both ELISAs (sensitivity, 87%; specifici ty, 94%). Immunoblotting of 51 serum specimens to sodium dodecyl sulfa te-denatured native 29-kDa protein was less sensitive (65%) than ELISA in detecting serum antibodies to the antigen. These results suggest a similar antibody response to native and recombinant antigens (r = 0.8 6) and support the potential utility of a quantitative assay with defi ned recombinant antigen for the serodiagnosis of invasive amebiasis in nonendemic areas in conjunction with other diagnostic tools.