Recent antiviral strategies against human coronavirus-related respiratory illnesses

Marine Sponge is a Promising Natural Source of Anti-SARS-CoV-2 Scaffold

The current pandemic caused by SARS-CoV2 and named COVID-19 urgent the need for novel lead antiviral drugs. Recently, United States Food and Drug Administration (FDA) approved the use of remdesivir as anti-SARS-CoV-2. Remdesivir is a natural product-inspired nucleoside analogue with significant broad-spectrum antiviral activity. Nucleosides analogues from marine sponge including spongouridine and spongothymidine have been used as lead for the evolutionary synthesis of various antiviral drugs such as vidarabine and cytarabine. Furthermore, the marine sponge is a rich source of compounds with unique activities. Marine sponge produces classes of compounds that can inhibit the viral cysteine protease (Mpro) such as esculetin and ilimaquinone and human serine protease (TMPRSS2) such as pseudotheonamide C and D and aeruginosin 98B. Additionally, sponge-derived compounds such as dihydrogracilin A and avarol showed immunomodulatory activity that can target the cytokines storm. Here, we reviewed the potential use of sponge-derived compounds as promising therapeutics against SARS-CoV-2. Despite the reported antiviral activity of isolated marine metabolites, structural modifications showed the importance in targeting and efficacy. On that basis, we are proposing a novel structure with bifunctional scaffolds and dual pharmacophores that can be superiorly employed in SARS-CoV-2 infection.

Inhibitors of SARS-CoV entry--identification using an internally-controlled dual envelope pseudovirion assay

Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) emerged as the causal agent of an endemic atypical pneumonia, infecting thousands of people worldwide. Although a number of promising potential vaccines and therapeutic agents for SARS-CoV have been described, no effective antiviral drug against SARS-CoV is currently available. The intricate, sequential nature of the viral entry process provides multiple valid targets for drug development. Here, we describe a rapid and safe cell-based high-throughput screening system, dual envelope pseudovirion (DEP) assay, for specifically screening inhibitors of viral entry. The assay system employs a novel dual envelope strategy, using lentiviral pseudovirions as targets whose entry is driven by the SARS-CoV Spike glycoprotein. A second, unrelated viral envelope is used as an internal control to reduce the number of false positives. As an example of the power of this assay a class of inhibitors is reported with the potential to inhibit SARS-CoV at two steps of the replication cycle, viral entry and particle assembly. This assay system can be easily adapted to screen entry inhibitors against other viruses with the careful selection of matching partner virus envelopes.

Infection with human coronavirus NL63 enhances streptococcal adherence to epithelial cells

Understanding the mechanisms of augmented bacterial pathogenicity in post-viral infections is the first step in the development of an effective therapy. This study assessed the effect of human coronavirus NL63 (HCoV-NL63) on the adherence of bacterial pathogens associated with respiratory tract illnesses. It was shown that HCoV-NL63 infection resulted in an increased adherence of Streptococcus pneumoniae to virus-infected cell lines and fully differentiated primary human airway epithelium cultures. The enhanced binding of bacteria correlated with an increased expression level of the platelet-activating factor receptor (PAF-R), but detailed evaluation of the bacterium-PAF-R interaction revealed a limited relevance of this process.

Recent developments in anti-severe acute respiratory syndrome coronavirus chemotherapy

Severe acute respiratory syndrome coronavirus (SARS-CoV) emerged in early 2003 to cause a very severe acute respiratory syndrome, which eventually resulted in a 10% case-fatality rate. Owing to excellent public health measures that isolated focus cases and their contacts, and the use of supportive therapies, the epidemic was suppressed to the point that further cases have not appeared since 2005. However, despite intensive research since then (over 3500 publications), it remains an untreatable disease. The potential for re-emergence of the SARS-CoV or a similar virus with unknown but potentially serious consequences remains high. This is due in part to the extreme genetic variability of RNA viruses such as the coronaviruses, the many animal reservoirs that seem to be able host the SARS-CoV in which reassortment or recombination events could occur and the ability coronaviruses have to transmit relatively rapidly from species to species in a short period of time. Thus, it seems prudent to continue to explore and develop antiviral chemotherapies to treat SARS-CoV infections. To this end, the various efficacious anti-SARS-CoV therapies recently published from 2007 to 2010 are reviewed in this article. In addition, compounds that have been tested in various animal models and were found to reduce virus lung titers and/or were protective against death in lethal models of disease, or otherwise have been shown to ameliorate the effects of viral infection, are also reported.

Molecular imaging of influenza and other emerging respiratory viral infections

Research on the pathogenesis and therapy of influenza and other emerging respiratory viral infections would be aided by methods that directly visualize pathophysiologic processes in patients and laboratory animals. At present, imaging of diseases, such as swine-origin H1N1 influenza, is largely restricted to chest radiograph and computed tomography (CT), which can detect pulmonary structural changes in severely ill patients but are more limited in characterizing the early stages of illness, differentiating inflammation from infection or tracking immune responses. In contrast, imaging modalities, such as positron emission tomography, single photon emission CT, magnetic resonance imaging, and bioluminescence imaging, which have become useful tools for investigating the pathogenesis of a range of disease processes, could be used to advance in vivo studies of respiratory viral infections in patients and animals. Molecular techniques might also be used to identify novel biomarkers of disease progression and to evaluate new therapies.

Severe acute respiratory syndrome (SARS)

This article reviews the virology, history, pathology, epidemiology, clinical presentations, complications, radiology, laboratory testing, diagnosis, treatment, and prevention of severe respiratory distress syndrome, with reference to documented outbreaks of the disease.

Broad-spectrum in vitro activity and in vivo efficacy of the antiviral protein griffithsin against emerging viruses of the family Coronaviridae

Viruses of the family Coronaviridae have recently emerged through zoonotic transmission to become serious human pathogens. The pathogenic agent responsible for severe acute respiratory syndrome (SARS), the SARS coronavirus (SARS-CoV), is a member of this large family of positive-strand RNA viruses that cause a spectrum of disease in humans, other mammals, and birds. Since the publicized outbreaks of SARS in China and Canada in 2002-2003, significant efforts successfully identified the causative agent, host cell receptor(s), and many of the pathogenic mechanisms underlying SARS. With this greater understanding of SARS-CoV biology, many researchers have sought to identify agents for the treatment of SARS. Here we report the utility of the potent antiviral protein griffithsin (GRFT) in the prevention of SARS-CoV infection both in vitro and in vivo. We also show that GRFT specifically binds to the SARS-CoV spike glycoprotein and inhibits viral entry. In addition, we report the activity of GRFT against a variety of additional coronaviruses that infect humans, other mammals, and birds. Finally, we show that GRFT treatment has a positive effect on morbidity and mortality in a lethal infection model using a mouse-adapted SARS-CoV and also specifically inhibits deleterious aspects of the host immunological response to SARS infection in mammals.

The role of viruses in the etiology and pathogenesis of common cold

Numerous viruses are able to cause respiratory tract infections. With the availability of new molecular techniques, the number of pathogens detected in specimens from the human respiratory tract has increased. Some of these viral infections have the potential to lead to severe systemic disease. Other viruses are limited to playing a role in the pathogenesis of the common cold syndrome. This chapter focuses on the viral pathogens that are linked to common cold. It is not the intention to comprehensively review all the viruses that are able to cause respiratory tract infections—this would go beyond the scope of this book. The list of viruses that are briefly reviewed here includes rhinoviruses, respiratory syncytial virus, parainfluenza virus, adenovirus, metapneumovirus and coronavirus. Bocavirus is discussed as one example of a newly identified pathogen with a less established role in the etiology and pathogenesis of common cold. Influenza virus does not cause what is defined as common cold. However, influenza viruses are associated with respiratory disease and the clinical picture of mild influenza and common cold frequently overlaps. Therefore, influenza virus has been included in this chapter. It is important to note that a number of viruses are frequently co-detected with other viruses in humans with respiratory diseases. Therefore, the viral etiology and the role of viruses in the pathogenesis of common cold is complex, and numberous questions remain to be answered.

Human monoclonal antibodies to SARS-coronavirus inhibit infection by different mechanisms

SARS-CoV causes an acute infection making targeted passive immunotherapy an attractive treatment strategy. We previously generated human mAbs specific to the S1 region of SARS-CoV S protein. These mAbs bind epitopes within the receptor binding domain (RBD) or upstream of the RBD. We show that mAbs recognizing epitopes within the RBD inhibit infection by preventing viral attachment to the cellular receptor. One mAb binds upstream of the RBD and prevents viral entry by inhibiting a post-binding event. Evaluation of several mAbs demonstrated varying ability of the mAbs to select escape mutants when used individually. However, a mixture of antibodies could effectively neutralize a range of mutant viruses. These data strongly suggest that a mixture containing antibodies recognizing distinct regions and targeting more than one step in viral entry is likely to be more effective in neutralizing the virus and suppressing the generation of escape mutants, and thus potentially constitute a highly effective passive immunotherapy.