Antibody Detection for Diagnosis of Acute Leptospirosis

Pathogenic members of the genus, Leptospira, in particular L. interrogans, cause leptospirosis, which has an estimated 5-20% case fatality rate. This disease is of particular importance to the U.S. military, to returning travelers, and in subtropical regions of the United States. Early diagnosis of leptospirosis leading to specific antimicrobial treatment prevents progression to severe disease, which is characterized by fever, refractory shock, pulmonary (and other) hemorrhage, and acute renal failure. Because the initial manifestations of leptospirosis, including acute undifferentiated fever, are non-specific, the diagnosis of this disease is often missed or delayed. The well-recognized market for a diagnostic test that identifies early, acute leptospirosis is an unmet and substantial need, both in terms of clinical care and for quantifying the burden of leptospirosis disease that is of prime interest in the United States. In the United States, leptospirosis is an important consideration in the differential diagnosis of fever in U.S. military personnel, the returned traveler and those with potential domestic zoonotic exposures. Clinically-actionable tests to diagnose acute leptospirosis remain unavailable. This proposal aims to address this gap and domestic and global needs by developing solid phase antibody-detection assays for referral laboratory use and for rapid, point-of-care, actionable diagnosis. The Luna Bioscience team has developed an antibody-detection ELISA using recombinant Virulence Modifying Protein (VMP) antigens that enables detection of pathogen-specific IgM and IgG antibodies early (4 days) in experimentally-infected Rhesus macaques, and in naturally acquired, diverse leptospiral infection in humans. In humans, our preliminary data show that our new VMP-based ELISA identified acute leptospiral infection better than standard tests (culture, Microscopic Agglutination Test (MAT)) and PCR. We propose to further develop VMP-based ELISA and Lateral Flow Assay (LFA) rapid tests in two Specific Aims. First, we will optimize and produce prototype solid phase VMP-based antibody-detection leptospirosis diagnostic tests using serially-obtained sera from experimentally infected animals challenged with multiple species and serovars of Leptospira. Second, we will test well-characterized, biobanked, deidentified sera from military personnel and from at-risk Americans for anti-VMP antibodies and compare results with standard and commercially-available tests. This Phase I STTR project will yield intellectual property and prototypes of solid phase leptospiral antibody-detecting assays for diagnosis of human leptospirosis. A Phase II project will involve scaled-up manufacturing for ELISA kits and LFA devices, and expanded field-based clinical testing in Americans at risk for leptospirosis, and lead to commercialization.