DIAGNOSIS OF ENTAMOEBA HISTOLYTICA INFECTION

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Entamoeba histolytica is believed to infect a half billion people annually. Approximately 10% of these individuals become symptomatic and develop colitis and liver abscess with a mortality rate of more than 40,000 persons each year. The current method of diagnosis utilizes microscopy. However, this method requires extensive experience, is tedious, and may not be accurate if not performed within minutes of specimen collection. It also does not distinguish nonpathogenic from pathogenic strains, a major disadvantage because nonpathogenic strains do not cause disease and persons infected with nonpathogenic strains do not require treatment with harsh antiamebic drugs. In Phase I, we initiated studies on the development and evaluation of two monoclonal antibody (MAb)-based ELISAs that detect the adhesin of the organism. Studies were performed on stool specimens and results were compared with microscopy, culture, and zymodeme analysis. In addition, we initiated studies on the detection of adhesin in sera and liver abscess aspirates, In Phase II, we will continue clinical evaluations of the E. histolytica Test and develop 510(k) applications for submission to the FDA. We will develop a genetic system for overexpressing the E. histolytica adhesin, develop assay conditions for preserved stools, and evaluate "user-friendly" dipstick tests. We will develop alternative assay formats to detect adhesin in sera, urine, and liver aspirates. We will develop PCR methods as additional aids for evaluation. Clinical trials will be performed with emphasis on HIV-infected individuals. Data will be collected for 510(k) applications for submission to the FDA. Special emphasis will be placed on completing the work started in Phase I on tests highly specific for pathogenic E. histolytica. Our tests will be scaled up for commercial application. Phase II represents a strong collaborative effort to develop and improve diagnostic tests for amebiasis. PROPOSED COMMERCIAL APPLICATION: Immunoassays that detect Entamoeba histolytica in stool specimens and that distinguish pathogenic from nonpathogenic strains are more accurate and dependable than methods currently used. The results of this project should lead to the development of commercial diagnostic tests that will be of significant value to the health industry around the world.