Abstract. To determine if genetic diversity of Blastocystis hominis exists in Japan, we monitored 64 B. hominisinfected people: 39 asymptomatic people whose infections were detected during routine medical check-ups (32 Japanese and 7 non-Japanese) and 25 patients with gastrointestinal symptoms who visited the outpatient clinics of St. Luke's International Hospital (19 Japanese and 6 non-Japanese). We detected 6 known and 2 new riboprint patterns in isolates from the infected people. There were no differences in the distribution of ribodemes between isolates from Japanese and non-Japanese people, similar to that in other countries. However, we noted a possible relationship between ribodeme type and pathogenicity. The results suggest that ribodemes I, III, and VI may be responsible for gastrointestinal symptoms.

A monoclonal antibody that reacts with a 150-kDa protein of Entamoeba histolytica on Western immunoblotting under nonreducing conditions inhibits the adherence and cytotoxicity of the ameba to mammalian cells in vitro. Affinity purification of solubilized trophozoites using the monoclonal antibody and electrophoresis yielded three glycoproteins with molecular masses of 150, 170, and 260 kDa, suggesting the existence of either a common epitope or the close association of these proteins. The 260-kDa fraction was identified as the well-known galactose (Gal)- and N-acetyl-D-galactosamine (GalNAc)-inhibitable lectin. The 150- and 170-kDa fractions seemed to exist as part of a 380-kDa native protein with an isoelectric point of pH 6.9. The N-terminal amino acid sequence of the 150-kDa protein was unique, indicating that the protein was not a degraded product of the 260-kDa lectin. By gel filtration, the 260-kDa lectin and the 150/170-kDa protein could be separated. When Chinese hamster ovary cells were pretreated with the fraction consisting of the 150/170-kDa protein the adherence of trophozoites to Chinese hamster ovary cells was competitively inhibited to a level equivalent to that observed for the 260-kDa lectin. The inhibitory effect was lost in the presence of Gal and GalNAc but was not influenced by the presence of glucose. These results demonstrate that the 150/170-kDa protein is a Gal/GalNAc-inhibitable lectin. The existence of a sugar-binding domain in the protein was confirmed by Gal-affinity chromatography.

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A monoclonal antibody (MAb) produced against trophozoites of Entamoeba histolytica strain HM-1:IMSS, reacted with all of 42 isolates and 4 clones showing pathogenic zymodeme (Z) patterns, i.e., Z-II, Z-IIa-, Z-II (glucose phosphate isomerase:-y+), Z-VII, Z-VII (glucose phosphate isomerase:aL lack, -y+), Z-XI, Z-XIV, and Z-XIX, regardless of culture conditions, geographical origins, or host symptoms in an indirect fluorescence antibody test. In contrast, the MAb failed to react with 14 isolates possessing nonpathogenic zymodemes Z-I and Z-VIII and did not react with other enteric protozoan parasites, such as E. histolytica-like Laredo, Entamoeba hartmanni, Entamoeba coli, Endolimax nana, Dientamoeba fragilis, Trichomonas hominis, and Giardia lamblia. Western immunoblotting analysis showed that the molecular weight of the antigenic component recognized by the MAb was exclusively 30,000 in pathogenic isolates of different zymodemes. These results suggest that the 30,000-molecular-weight antigen is a marker of pathogenic isolates and that the indirect fluorescent-antibody test with the MAb is useful for the accurate discrimination of pathogenic amebae.

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