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An association between tumor necrosis factor alpha (TNF-alpha) and Entamoeba histolytica diarrhea was assessed in a cohort of 138 non-related Bangladeshi children who have been prospectively followed since 2001. Peripheral blood mononuclear cells (PBMCs) obtained at study entry were purified, cultured, and stimulated with soluble amebic antigen before cytokine measurement from supernatant. Higher levels of TNF-alpha were associated with increased risk of first (P = 0.01) and recurrent E. histolytica-related diarrheal episodes (P = 0.005). Children who developed E. histolytica diarrhea had significantly higher TNF-alpha protein levels than those who experienced asymptomatic E. histolytica infection (P value = 0.027) or no infection (P value = 0.017). Microarray studies performed using RNA isolated from acute and convalescent whole blood and colon biopsy samples revealed higher but non-significant TNF-alpha messenger RNA (mRNA) levels in subjects with acute E. histolytica diarrhea compared with convalescence. We conclude that there is an association between higher TNF-alpha production and E. histolytica diarrhea.

Seroprevalence of Entamoeba histolytica infection in HIV-infected individuals from Shanghai city, Anhui province, and Henan province, China, was examined by enzyme-linked immunosorbent assay using crude antigen and a recombinant surface antigen, C-Igl, of the parasite. In 215 HIV-infected individuals, the positive rates for these antigens were 12.1% and 7.9%, respectively; these rates were significantly higher than the rates of 3.1% and 0.5%, respectively, in 191 patients with gastrointestinal symptoms who were not infected with HIV. There was no significant difference in seropositivity to E. histolytica between men and women. Seropositivity in HIV-infected individuals was higher in patients with a CD4(+) T cell count of < 200/microL. This is the first report showing a higher seroprevalence of E. histolytica infection in HIV-infected patients in China. Our results also suggest that HIV infection is a risk factor for infection with E. histolytica.