HM-1:IMSS, a pathogenic strain of Entamoeba histolytica, and its mutant BG-3, identified by resistance to cytochalasin D, were tested for their capacity to: (i) secrete electron-dense granules; (ii) adhere and digest native type I collagen gels; and (iii) produce liver abscesses in new-born hamsters. The results demonstrate that the mutant has low adherence to collagen, low electron-dense granule secretion and collagenolytic activity, and low capacity to produce liver lesions in vivo, compared with the parental strain HM1:IMSS.
Differences in geographic distribution of the s and m vacA alleles in Chile and a relationship of s1b m1 genotype with gastritis were found. Sequence data in part support a hispanic origin for the vacA genotype. Asymmetric distribution of genotypes s1b m1 and s2 m2 recedes H Pylori strain distribution in Spain and Portugal.
In vitro interaction of Entamoeba histolytica with collagen induces intracellular formation and release of electron-dense granules (EDG) and stimulation of collagenolytic activity. Purified EDG contain 1.66 U of collagenase per mg of protein. Thus, EDG may participate in tissue destruction during invasive amebiasis. Monoclonal antibodies (MAbs) L1.1 and L7.1 reacted specifically with EDG in enzyme-linked immunosorbent assay (ELISA) and immunofluorescence and immunoelectron microscopy. MAb L7.1 immunoprecipitated three polypeptides with molecular weights of 95,000, 68,000, and 28,000 from lysates of biosynthetically labeled E. histolytica. Both MAbs recognized the pathogenic E. histolytica axenic strains HM1:IMSS, HM38:IMSS, and HK-9 but failed to react in ELISA with Entamoeba moshkovskii, Entamoeba invadens, and E. histolytica-like Laredo. In addition, MAb L7.1 reacted with one E. histolytica isolate from a symptomatic patient but did not react with four of five isolates from asymptomatic patients. EDG antigens were detected by a MAb L7. 1-based ELISA in E. histolytica-containing fecal samples from symptomatic, but not asymptomatic, individuals. These results suggest that the EDG antigen detected with MAb L7. 1 may be differentially expressed in pathogenic and nonpathogenic E. histolytica.
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