SARS-CoV

A new coronavirus was quickly identified after the outbreak of an atypical pneumonia in southern China early in 2003. The new virus eventually caused 8,000 infections with approximately 800 deaths in 29 countries. The condition was named Severe Acute Respiratory Syndrome, SARS, and the causative coronavirus named SARS-CoV. The zoonotic nature of the infection came with the identification of a similar virus in bats (Poon et al. 2005), although it is possible that the bat virus passed through other animal hosts and recombined with other SARS-like coron-aviruses prior to infecting humans (Hon et al. 2008). SARS-CoV is not currently circulating in the human population however, the mysterious appearance and rapid spread of this virus emphasized how vulnerable the human population is to such respiratory infections. This has spurred interest in the development of antivirals that could be used either in treatment or as prophylaxis to complement public health measures in curbing future outbreaks. 

The initial search for an inhibitor of the SARS 3CL protease focused on preexisting drugs and compounds, some tested empirically and others selected based on modeling. The HlV-1 PI nelfinavir and lopinavir/ritonavir have been considered, with the latter actually used clinically in SARS CoV-infected subjects. The rhi-novirus inhibitor ruprintrivir and related compounds have also been tested (reviewed in Fear et al. 2007). However, in the absence of any elements of specificity, these preexisting compounds would be expected to have low potency. 

SARS-CoV Severe acute respiratory syndrome coronavirus... 

Since the pioneering work of Kleymann et al. (2002), Betz et al. (2002), Baumeister et al. (2007), and Crute et al. (2002), who showed that compounds identified as inhibitors of the helicase-primase enzyme complex could alleviate herpesvirus-induced disease in animal models, the attention of researchers developing antiviral compounds has been drawn more and more towards the virus-encoded helicases, particularly those of Herpes viruses and of RNA viruses such as Hepatitis C Virus (HCV) and SAKS coronavirus (SARS-CoV). Enzyme activity is usually assayed by measuring NTPase activity in the presence of an appropriate nucleic acid co-substrate although, more recently, novel fiuorimetric and luminescence principles have been applied to the measurement of strand unwinding and/or translocation of the protein along the nucleic acid (Frick 2003, 2006). 

Helicase has also been a focal point for the development of antiviral chemotherapy of the coronavirus associated with severe acute respiratory syndrome (SARS) in humans. Although several experimental compounds with nucleic acid binding activity showing effective inhibition of SARS-CoV helicase were reported in 2005, there have been no reports of any further development since that time (Kesel 2005). It remains to be seen whether the S ARS-CoV compounds will be developed further, especially since no new infections have been observed in recent years. 

Sainz B Ir, Mossel EC, Peters CJ, Garry RF (2004) Interferon-beta and interferon-gamma syner-gistically inhibit the replication of severe acute respiratory syndrome-associated coronavirus (SARS-CoV). Virology 329 11-17... 

S-Adenosylmethionine carboxylase Sex-hormone binding globulin CYP 2D6 Falcipain 2 and 3 SARS CoV Chkl kinase Heme oxygenase... 

Protein phosphatase 2C Protein arginine methyltransferase Protein arginine methyltransferase Arylalkylamine N-acetyltransferase SARS Cov 3C-like protease AHAS... 

Researchers at SRMLSC recently developed a HTS that allowed the identification of potential inhibitors of the severe acute respiratory syndrome coronavirus (SARS CoV) from large compound libraries [34], The luminescent-based assay, which measured the inhibition of SARS CoV-induced cytopathic effects (CPE) in Vero E6 cells, was validated with two different diversity sets of compounds against the SARS CoV. The hit rate for both libraries was approximately 0.01%. 

The validated HTS assay was then employed to screen a 100,000-compound library against SARS CoV. The hit rate for the library in a single-dose format was determined to be approximately 0.8%. Screening of the three libraries resulted in the identification of several novel compounds that effectively inhibited the CPE of SARS CoV in vitro. Three hit compounds, shown below, were identified as promising lead candidates for further evaluation. 

Key Words Antigens antibodies carbohydrates glycans glyconjugates microarrays micro spotting nitrocellulose polysaccharides SARS-CoV. 

Horse anti-SARS-CoV anti-sera (gift of Dr. JiahaiLu, Sun-Yatsen University, Guangdong, China). 

Fig. 3. Schematic of staining process of SARS-CoV immunochip. (1) Spotting A high-precision robot transfers the samples, SARS-CoV proteins, and glycans of various complexities, from 96-well plate to nitrocellulose-coated glass slides. (2) Staining Before staining, the slides are rinsed with IX phosphate-buffered saline (PBS), and blocked with 1% bovine serum albumin (BSA)-PBS containing 0.05% NaN3 and 0.05% Tween-20. They are subsequently incubated with horse anti-SARS sera. The primary antibodies captured by microarrays are detected using biotinated anti-horse immunoglobulin (Ig)G, and visualized by Cy3-streptavidin.

Our rationale was that if SARS-CoV expressed antigenic carbohydrate structures, then immunizing animals using the whole virus-based vaccines would have elicited specific antibodies for these structures. In addition, if SARS-CoV displayed a carbohydrate structure that mimics host cellular glycans, then vaccinated animals may develop antibodies with autoimmune reactivity to their corresponding cellular glycans. 

Wang, D. and Lu, J. (2004) Glycan arrays lead to the discovery of autoimmuno-genic activity of SARS-CoV. Physiol. Genomics 18(2), 245-248. 

Moreover, this new class of bioorganometallic compounds exerts antiviral effects with some selectivity toward SARS-CoV infection. These new drugs may offer an interesting alternative for Asia where SARS originated and malaria has remained endemic. 

Severson, W.E. et al. 2007. Development and validation of a high-throughput screen for inhibitors of SARS CoV and its application in screening of a 100,0000-compound library. J. Biomol. Screen. 12, 33 -0. 

Travel to a foreign or domestic location wiili documented or suspected recent ttansmission of SARS-CoV or... 

V Aiiitbody to SARS-CoV is undetectable in a semm specimen obtained >28 days after onset of ilincssff, or... 

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