The 30-kDa antigen (p30) of an Entamoeba histolytica pathogenic strain : preparation of recombinant p30 and its application

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(1) Since the previously reported cDNA coding the 30-kDa antigen (p30) of E.Histolytica was incomplete, the cDNA library of the parasite was screened with monoclonal antibody 4G6. Three cDNA were cloned and sequenced.(2) Amino acid analysis of p30, purified by affinity column chromatography using monoclonal antibody, demonstrated that two of the cloned cDNA contained the complete coding region. The molecular weight and isoelectric point of p30 were 26,253 and 7.44, respectively.(3) Western immunoblot analysis demonstrated that p30 was reactive with some sera from patients with amebic liver abscesses, but was not reactive with sera from patients with amebic colitis. A similar pattern of reactivity was observed when the fusion protein expressed in E.coli was used as antigen in a dot-blot analysis.(4) Immunoelectron microscopy localized p30 in the nucleus and cytoplasm of the trophozoites, but not on the plasma membrane. A database analysis of the amino acid sequence of p30 revealed homology with gene products preferentially expressed in murine erythroleukemia cells, murine osteoblastic cells, and ras-transformed human mammary epithelial cells. These data suggest that p30 plays an important role in the proliferation of E.histolytica.