ELISA de captura de antígeno para o diagnóstico de leptospirose

Abstract

Leptospirosis is an infectious disease caused by pathogenic spirochetes of the genus Leptospira that can affect vital organs such as lungs, liver and kidneys. The illness is characterized by an acute bacteremic phase of approximately one week, followed by an immune phase in which specific antibodies are found in blood and leptospires are eliminated in urine. Clinical signs in the initial phase of leptospirosis can be confused with other feverish diseases, making laboratory diagnosis of extreme importance to start antibiotic treatment. The existing laboratory tests for early diagnosis of leptospirosis are based on IgM detection and are of low sensitivity. Thus, there is an urgent need for development of new diagnostic strategies for use in the acute phase of leptospirosis. In the present work monoclonal antibodies (MAbs) and polyclonal IgY were used in the standardization of three different antigen capture ELISA formats for direct detection of leptospires in blood during the acute phase of the disease. Detection limit of leptospires in human sera experimentally contaminated ranged from 10 5 to 10 7 cells per millilitre in the different formats. The ELISA format with the best performance was able to detect 10 5 leptospires per millilitre of human sera, using as capture antibody a MAb against LipL32, the major outer membrane protein of pathogenic leptospires, and as detection antibody biotinilated policlonal IgY against a pathogenic serovar of Leptospira interrogans. Although this format did not present the adequate sensitivity for detection of circulating leptospires at the levels existing in blood in the initial phase of the disease, it can be improved in order to do so.