Development of Instantaneous Protection against SARS-CoV with Implications for Multiple RNA Viruses

Development of Instantaneous Protection Against SARS-CoV with Implications for Multiple RNA Viruses Hatem A. Elshabrawy, Ph.D. Department of Microbiology and Immunology University of Illinois at Chicago Chicago, Illinois (2012) Dissertation Chairperson: Dr. Bellur S. Prabhakar The purpose of this study is to develop and identify neutralizing human monoclonal antibodies (HmAbs) against a wide range of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) clinical isolates and antiviral drugs of therapeutic value against multiple RNA viruses e.g. SARS-CoV, Ebola virus (EBOV), Hendra virus (HeV), and Nipah virus (NiV). Currently, there are no effective treatments available. Immune sera from convalescent patients have been shown to be effective in the treatment of patients infected with SARS-CoV making passive immune therapy with HmAbs an attractive treatment strategy for SARS. Previously, using Xenomouse (Amgen British Columbia Inc), a panel of neutralizing HmAbs, was produced in our laboratory, that could specifically bind to the ectodmain of the SARS-CoV spike (S) glycoprotein. Some of the HmAbs were S1 domain specific, while some were not. In this study, we describe non-S1 binding neutralizing HmAbs that can specifically bind to the conserved S2 domain of the S protein. However, unlike the S1 specific HmAbs, the S2 specific HmAbs can neutralize pseudotyped viruses expressing different S proteins containing receptor binding domain sequences of various clinical isolates. These data indicate that HmAbs which bind to conserved regions of the S protein are more suitable for conferring protection against a wide range of SARS-CoV variants and have implications for generating therapeutic antibodies or subunit vaccines against other enveloped viruses. Additionally, this study describes the identification of small chemical compounds which exhibit antiviral activity against SARS-CoV, EBOV, HeV, and NiV all of which require cathepsin L for entering into the target cells. We made use of a High Throughput Screening Assay (HTSA) optimized in our laboratory to identify and characterize candidate compounds from libraries of small molecules that can broadly inhibit cathepsin L mediated cleavage of viral glycoproteins derived peptides containing the natural cathepsin L cleavage sites. In vitro screening of potential hits against SARS-CoV and Ebola pseudotyped viruses identified one entry inhibitor for both viruses and a derivative which is more potent than the parent compound. These results suggest that our approach may be used for developing “broad spectrum anti-viral drugs” that are safe and effective.