The infected case blood/serum sample was transferred directly onto the sample pad. LFT was incubated laterally for 10-15 minutes, and the sample solutions absorbed and immediately dissolved the colloidal gold conjugate, the reaction between the conjugate antibody and LipL21 antigen took place, and this complex was carried forward onto the nitrocellulose membrane containing the capture lines (Test line containing anti-rLipL21 IgG and control line containing anti-rabbit IgG). The nitrocellulose membrane containing second antibody interaction with leptospiral LipL21-conjugated antibody complex takes place. This immune complex observed on the nitrocellulose membrane solid surface and the unbound reagent was subsequently adsorbed by absorbent pad. When two dark red lines were observed after incubation at test line and the control line, sample evaluation was defined as positive. In the case of observation of only one dark red line at the control line, sample evaluation was defined as negative.
The present invention relates to a diagnostic method for the detection of acute leptospirosis. The method of the invention allows for a quick, specific and sensitive detection of the disease caused by pathogenic Leptospira. The described method is based on the immunological detection of the protein LipL21, a membrane protein expressed specifically by pathogenic strains of Leptospira. Furthermore, the present invention relates to the development of a diagnostic device that allows positive diagnosis to be conducted in the early and critical stage of the infection. The preferred diagnostic device of the invention is a lateral flow test, which as a hand-held assay, is easy to use and facilitates diagnosis of leptospirosis in the first 5 days of infection. The first 5 days of the infection is where the subject or patient could succumb to the disease. Diagnosis of the disease at this critical stage of infection would then advise the affected patient to have immediate systemic antibiotic treatment and thereby, avoid succumbing to the disease.