T-cell suppression and selective in vivo activation of TH2 subpopulation by the Entamoeba histolytica 220-kilodalton lectin.

A 220-kDa surface protein (L220) with lectin activity from Entamoeba histolytica trophozoites has been characterized previously (J. L. Rosales-Encina, I. Meza, A. López-de-León, P. Talamás-Rohana, and M. Rojkind, J. Infect. Dis. 156:790-797, 1987). This molecule is involved in the adhesion process (I. Meza, F. Cázares, J. L. Rosales-Encina, P. Talamás-Rohana, and M. Rojkind, J. Infect. Dis. 156:798-805, 1987) and is very immunogenic. In this work, we studied both the humoral and the cellular immune responses to L220. We compared L220 with L220-derived components, such as a fusion peptide (M-11) and chemically obtained peptides (by treating the 220-kDa molecule with N-chlorosuccinimide-urea). Spleen cells from L220-immunized mice were unable to proliferate in vitro when stimulated with the protein. However, a proliferative response was obtained when mice were immunized with the L220-derived fusion peptide or the cleaved lectin. To find out if there was a correlation between the observed responses and TH1 or TH2 activation, we analyzed patterns of cytokine secretion (interleukin-2 [IL-2], IL-4, IL-10, and gamma interferon). Cells from mice immunized with peptides that induced cell proliferation (100, 80, and 47 kDa) with the peptides (P < 0.01) and with the intact molecule secreted IL-2 and gamma interferon, showing a TH1-subset pattern. Conversely, cells from mice immunized with the intact 220-kDa molecule secreted IL-4 and IL-10, typical of a TH2 subpopulation; however, antibodies from each group recognized the 220-kDa molecule as determined by Western blotting (immunoblotting). These results suggest that various epitopes in the 220-kDa molecule generate different response patterns, suppressing or activating T-cell responses.

Purification and partial characterization of an hemolytic activity from Entamoeba histolytica.

It is generally accepted that hydrolytic and cytolytic amebic components are involved in the pathogenic mechanisms of E. histolytica. We have now identified a lytic activity in two membrane proteins of 23.5 kDa and 25 kDa, which are able to lyse rat erythrocytes. The activity was purified from total homogenates of the virulent strains HM1:IMSS and HM38:IMSS, and the erythrocyte lysis was directly related to protein concentration. The hemolytic activity was heat-sensitive and resistant to reduction by 2-mercaptoethanol. Total amino acid analysis of pure proteins showed a high hydrophobic amino acid content: 36% for 23.5 kDa and 50% for 25 kDa. This hemolytic activity could be related, along with other amebic factors, to tissue damage.

Antigen detection in onchocerciasis: correlation with worm burden.

Detection of O. volvulus antigen by indirect ELISA test in the serum and the urine of 169 individuals with residence in the southeast onchocerciasis endemic focus in Chiapas, Mexico was performed. Every individual under study was physically examined for signs of onchocerciasis in particular for subcutaneous nodules, dermic lesions, ocular damage and history of Mazzotti reaction. Of the total cases, 91.7% were positive for skin microfilariae. Only 32.2% of the microfilariae positive cases carried at least one palpable nodule. The sensitivity of the ELISA test was 92.3% for serum and 85.9% for urine. A good correlation between the transformed numbers of skin microfilariae (square root of x + 1) and the positivity of the ELISA test for serum and for urine was found. It was also observed that the ELISA test values for the sera and for the urine showed a good correlation with r = 0.76 and Z0.95 less than 0.005. This serological test can be used for seroepidemiological surveys and for orientating the activity of massive onchocerciasis treatment campaigns.