Diagnosis of intestinal amebiasis using salivary IgA antibody detection.

This investigation sought to determine whether detection of salivary IgA antibodies to Entamoeba histolytica could identify intestinal amebic infections among 223 school children. Four groups of children were identified through coproparasitoscopic examination: E. histolytica as other parasites only (20%); and parasite-free (25%). The diagnostic accuracy of salivary IgA antibodies to an E. histolytica membrane extract was 91.5% (sensitivity, 85%; specificity, 98%), maintaining high predictive value at different prevalences. Also, a positive correlation (r = .753, P less than .001) was observed between fecal E. histolytica membrane antigen levels and salivary IgA antibody activity. Measurement of IgA antibodies in saliva may be useful in diagnosing intestinal infections with E. histolytica within a wide range of prevalences. Moreover, sampling of saliva may be a useful non invasive test for immunoepidemiologic surveys.

Evaluation of the ELISA test for detection of Entamoeba histolytica in feces.

The clinical utility of an ELISA test with monoclonal antibodies to detect antigen of Entamoeba histolytica in feces was evaluated in 150 patients with gastrointestinal symptoms. Each subject was examined by rectosigmoidoscopy with rectal smear and/or a triple stool search for ova-bacteria-parasite (OBP); in addition, one stool sample was collected for the ELISA test. All the tests were independent and double blind. E. histolytica was detected by OBP and/or rectosigmoidoscopy in 66 patients; 61 patients had other parasites; and in 23, no parasites were identified. Of all patients, 116 were positive for the ELISA test. Of these, E. histolytica was identified in 52. In 47, other parasites were identified and in 17, no parasites were found. The ELISA test with a monoclonal antibody against E. histolytica antigen showed higher sensitivity than the standard diagnostic methods: the ability to detect the presence of E. histolytica antigen regardless of the destruction of the parasite or of the error due to misidentification of the parasite resulting from faulty preparation of the samples.

An Entamoeba histolytica antigen devoid of enzymatic activity, but endowed with immunogenic and protective properties.

One of the most relevant features of Entamoeba histolytica extracts is their great enzymatic activity. The consequence of this peculiarity is that these extracts digest not only extrinsic proteins but also those within the parasite, causing instability during extract preparation which makes their characterization more difficult and hinders their use in immunoprophylaxis. This report presents evidence which indicates that treatment of E. histolytica extracts with a pH2 acid shock for 30 min at 37 degrees C irreversibly, as shown through its reactivity with polyclonal E. histolytica antisera and through its capacity to induce antibody formation and to protect against intrahepatic challenge with E. histolytica. Among the foremost activities in the field of immunoparasitology are the identification, isolation, purification and characterization of parasite antigens, particularly because of their potential use in immunoprophylaxis. Given the world wide distribution of amebiasis, particularly in undeveloped countries, various researchers have given special importance to the antigenic characterization of the causal agent, Entamoeba histolytica, and to its ability to induce protective immunity in several animal models. Initial studies demonstrated that the parasite produces a variety of proteolytic enzymes which play an important role in the immune response and pathogenesis of the infected host. Additionally, these enzymes cause autodegradation of the amebic extracts, their use in immunoprophylaxis, since proteins germane in inducing protection could be degraded. Even though enzymatic activity may be abolished through specific inhibitors, these are very toxic and therefore not adequate for biological material to be tried on humans.(ABSTRACT TRUNCATED AT 250 WORDS)