Rapid Diagnostics for Mucormycosis

Nasralla, Marwan

Abstract

Mucormycosis, most commonly caused by Rhizopus oryzae, is a life-threatening infection that occurs in patients immunocompromised by diabetic ketoacidosis (DKA), neutropenia, corticosteroid use, and/or increased serum iron. Because of the rising prevalence of these risk factors, the incidence of mucormycosis has risen. Despite disfiguring surgery and aggressive antifungal therapy, the mortality of mucormycosis remains >40%, and approaches 100% in patients with disseminated disease and prolonged neutropenia. A key factor which contributes to these abysmal mortality rates of mucormycosis is the current lack of rapid diagnostic tests. This deficiency often results in delayed therapy. Thus, a rapid diagnostic test for mucormycosis is likely to improve the outcome of the disease. Clinical hallmarks of R. oryzae infection include its remarkable angiotropism. We recently made the important discovery that the fungal cell surface proteins encoded by CotH facilitate disease progression by allowing R. oryzae to invade mammalian cells via binding to Glucose Regulated Protein 78 (GRP78), a heat shock protein expressed on endothelial cells lining blood vessels during mucormycosis. Importantly, CotH proteins were found to be conserved among Mucorales (organisms that cause mucormycosis) with amino acid identity ranging from 55-98%. Equally important CotH proteins are unique to Mucorales since they are absent from any other known organisms. Finally, CotH proteins were found to be expressed in clinically relevant animal models of mucormycosis including the DKA mouse model. These features strongly indicate that CotH and their gene products can be utilized for rapid detection of mucormycosis. Indeed our preliminary data show PCR-related methods using specific primers to CotH can amplify signals in blood samples spiked with different Mucorales but not Aspergillus fumigatus or Candida. Moreover, anti-CotH antibodies can recognize a band similar to the predicted size of CotH proteins in serum samples collected from infected mice. We propose to build on these exciting data to further establish CotH and/or their gene products as biomarkers for diagnosis of mucormycosis, progression of the disease and response to therapy. Our goal in this Phase I feasibility study is to use our established and clinically relevant DKA and neutropenic mucormycosis mouse models to develop a PCR-based assay and/or an antigen detection test targeting CotH in biological samples collected from mice infected with Mucorales. Phase II of this STTR application will focus on establishing a PCR-based kit, sandwiched ELISA and/or dipstick assays for the rapid detection of CotH or circulating CotH antigens by testing using human clinical samples. Establishing a rapid detection test will improve mucormycosis outcome by early initiation of proper therapy and inform the response to antifungal therapy.

Public Health Relevance

Mucormycosis is a life-threatening fungal infection that afflicts patients with weakened immune system. Current treatment fail in >40 of patients due to lack of appropriate and rapid detection methods which often results in delayed therapy. We propose to develop rapid detection methods using antigens uniquely present in fungi that cause mucormycosis.