Keep out! SARS-CoV-2 entry inhibitors: their role and utility as COVID-19 therapeutics

AbstractThe COVID-19 pandemic has put healthcare infrastructures and our social and economic lives under unprecedented strain. Effective solutions are needed to end the pandemic while significantly lessening its further impact on mortality and social and economic life. Effective and widely-available vaccines have appropriately long been seen as the best way to end the pandemic. Indeed, the current availability of several effective vaccines are already making a significant progress towards achieving that goal. Nevertheless, concerns have risen due to new SARS-CoV-2 variants that harbor mutations against which current vaccines are less effective. Furthermore, some individuals are unwilling or unable to take the vaccine. As health officials across the globe scramble to vaccinate their populations to reach herd immunity, the challenges noted above indicate that COVID-19 therapeutics are still needed to work alongside the vaccines. Here we describe the impact that neutralizing antibodies have had on those with early or mild COVID-19, and what their approval for early management of COVID-19 means for other viral entry inhibitors that have a similar mechanism of action. Importantly, we also highlight studies that show that therapeutic strategies involving various viral entry inhibitors such as multivalent antibodies, recombinant ACE2 and miniproteins can be effective not only for pre-exposure prophylaxis, but also in protecting against SARS-CoV-2 antigenic drift and future zoonotic sarbecoviruses.

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SARS-CoV-2 Biology Insights, Part IV.Antibody-Dependent Enhancement (ADE) and the tricky “Herd Immunity”: narrative review (Preprint)

10.2196/preprints.21599 ◽

2020 ◽

Author(s):

Laura Lafon-Hughes

Keyword(s):

Viral Infection ◽

Viral Entry ◽

Neutralizing Antibodies ◽

Vaccine Development ◽

Whooping Cough ◽

Common Knowledge ◽

Herd Immunity ◽

Life Quality ◽

Host Cells ◽

System P

BACKGROUND It is common knowledge that vaccination has improved our life quality and expectancy since it succeeded in achieving almost eradication of several diseases including chickenpox (varicella), diphtheria, hepatitis A and B, measles, meningococcal, mumps, pneumococcal, polio, rotavirus, rubella, tetanus and whooping cough (pertussis) Vaccination success is based on vaccine induction of neutralizing antibodies that help fight the infection (e.g. by a virus), preventing the disease. Conversely, Antibody-dependent enhancement (ADE) of a viral infection occurs when anti-viral antibodies facilitate viral entry into host cells and enhance viral infection in these cells. ADE has been previously studied in Dengue and HIV viruses and explains why a second infection with Dengue can be lethal. As already reviewed in Part I and Part II, SARS-Cov-2 shares with HIV not only 4 sequences in the Spike protein but also the capacity to attack the immune system. OBJECTIVE As HIV presents ADE, we wondered whether this was also the case regarding SARS-CoV-2. METHODS A literature review was done through Google. RESULTS SARS-CoV-2 presents ADE. As SARS, which does not have the 4 HIV-like inserts, has the same property, ADE would not be driven by the HIV-like spike sequences. CONCLUSIONS ADE can explain the failure of herd immunity-based strategies and will also probably hamper anti-SARS-CoV-2 vaccine development. As reviewed in Part I, there fortunately are promising therapeutic strategies for COVID-19, which should be further developed. In the meantime, complementary countermeasures to protect mainly the youth from this infection are presented to be discussed in Part V Viewpoint.

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Characterization of SARS-CoV-2 variants B.1.617.1 (Kappa), B.1.617.2 (Delta) and B.1.618 on cell entry, host range, and sensitivity to convalescent plasma and ACE2 decoy receptor

10.1101/2021.09.03.458829 ◽

2021 ◽

Author(s):

Wenlin Ren ◽

Xiaohui Ju ◽

Mingli Gong ◽

Jun Lan ◽

Yanying Yu ◽

...

Keyword(s):

Host Range ◽

Viral Entry ◽

Neutralizing Antibodies ◽

Cell Entry ◽

Decoy Receptor ◽

Host Tropism ◽

Entry Inhibitors ◽

Rapid Spread ◽

Entry Efficiency

ABSTRACTRecently, highly transmissible SARS-CoV-2 variants B.1.617.1 (Kappa), B.1.617.2 (Delta) and B.1.618 were identified in India with mutations within the spike proteins. The spike protein of Kappa contains four mutations E154K, L452R, E484Q and P681R, and Delta contains L452R, T478K and P681R, while B.1.618 spike harbors mutations Δ145-146 and E484K. However, it remains unknown whether these variants have altered in their entry efficiency, host tropism, and sensitivity to neutralizing antibodies as well as entry inhibitors. In this study, we found that Kappa, Delta or B.1.618 spike uses human ACE2 with no or slightly increased efficiency, while gains a significantly increased binding affinity with mouse, marmoset and koala ACE2 orthologs, which exhibits limited binding with WT spike. Furthermore, the P618R mutation leads to enhanced spike cleavage, which could facilitate viral entry. In addition, Kappa, Delta and B.1.618 exhibits a reduced sensitivity to neutralization by convalescent sera owning to the mutation of E484Q, T478K, Δ145-146 or E484K, but remains sensitive to entry inhibitors-ACE2-lg decoy receptor. Collectively, our study revealed that enhanced human and mouse ACE2 receptor engagement, increased spike cleavage and reduced sensitivity to neutralization antibodies of Kappa, Delta and B.1.618 may contribute to the rapid spread of these variants and expanded host range. Furthermore, our result also highlighted that ACE2-lg could be developed as broad-spectrum antiviral strategy against SARS-CoV-2 variants.

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Impact of the B.1.1.7 variant on neutralizing monoclonal antibodies recognizing diverse epitopes on SARS–CoV–2 Spike

10.1101/2021.02.03.429355 ◽

2021 ◽

Author(s):

Carl Graham ◽

Jeffrey Seow ◽

Isabella Huettner ◽

Hataf Khan ◽

Neophytos Kouphou ◽

...

Keyword(s):

Monoclonal Antibodies ◽

Viral Entry ◽

Neutralizing Antibodies ◽

Infectious Virus ◽

Antigenic Drift ◽

Host Cells ◽

Receptor Binding Domain ◽

Neutralization Activity ◽

Neutralizing Activity ◽

Neutralizing Epitopes

The interaction of the SARS–CoV–2 Spike receptor binding domain (RBD) with the ACE2 receptor on host cells is essential for viral entry. RBD is the dominant target for neutralizing antibodies and several neutralizing epitopes on RBD have been molecularly characterized. Analysis of circulating SARS–CoV–2 variants has revealed mutations arising in the RBD, the N–terminal domain (NTD) and S2 subunits of Spike. To fully understand how these mutations affect the antigenicity of Spike, we have isolated and characterized neutralizing antibodies targeting epitopes beyond the already identified RBD epitopes. Using recombinant Spike as a sorting bait, we isolated >100 Spike–reactive monoclonal antibodies from SARS–CoV–2 infected individuals. ≈45% showed neutralizing activity of which ≈20% were NTD–specific. None of the S2–specific antibodies showed neutralizing activity. Competition ELISA revealed that NTD–specific mAbs formed two distinct groups: the first group was highly potent against infectious virus, whereas the second was less potent and displayed glycan–dependant neutralization activity. Importantly, mutations present in B.1.1.7 Spike frequently conferred resistance to neutralization by the NTD–specific neutralizing antibodies. This work demonstrates that neutralizing antibodies targeting subdominant epitopes need to be considered when investigating antigenic drift in emerging variants.

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The impact of antigenic drift of influenza A virus on human herd immunity: Sero-epidemiological study of H1N1 in healthy Thai population in 2009

Vaccine ◽

10.1016/j.vaccine.2010.06.002 ◽

2010 ◽

Vol 28 (33) ◽

pp. 5437-5444 ◽

Cited By ~ 6

Author(s):

Yuta Kanai ◽

Naphatsawan Boonsathorn ◽

Malinee Chittaganpitch ◽

Guirong Bai ◽

Yonggang Li ◽

...

Keyword(s):

Epidemiological Study ◽

Influenza A Virus ◽

Influenza A ◽

Herd Immunity ◽

Antigenic Drift ◽

Thai Population ◽

The Impact

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The impact of Spike mutations on SARS-CoV-2 neutralization

10.1101/2021.01.15.426849 ◽

2021 ◽

Cited By ~ 9

Author(s):

C Rees-Spear ◽

L Muir ◽

SA Griffith ◽

J Heaney ◽

Y Aldon ◽

...

Keyword(s):

Monoclonal Antibodies ◽

Viral Entry ◽

Neutralizing Antibodies ◽

Protective Efficacy ◽

Polyclonal Antibodies ◽

Antibody Responses ◽

Serum Samples ◽

Neutralization Sensitivity ◽

Cross Neutralization ◽

The Impact

AbstractMultiple SARS-CoV-2 vaccines have shown protective efficacy, which is most likely mediated by neutralizing antibodies recognizing the viral entry protein, Spike. Antibodies from SARS-CoV-2 infection neutralize the virus by focused targeting of Spike and there is limited serum cross-neutralization of the closely-related SARS-CoV. As new SARS-CoV-2 variants are rapidly emerging, exemplified by the B.1.1.7, 501Y.V2 and P.1 lineages, it is critical to understand if antibody responses induced by infection with the original SARS-CoV-2 virus or the current vaccines will remain effective against virus variants. In this study we evaluate neutralization of a series of mutated Spike pseudotypes including a B.1.1.7 Spike pseudotype. The analyses of a panel of Spike-specific monoclonal antibodies revealed that the neutralizing activity of some antibodies was dramatically reduced by Spike mutations. In contrast, polyclonal antibodies in the serum of patients infected in early 2020 remained active against most mutated Spike pseudotypes. The majority of serum samples were equally able to neutralize the B.1.1.7 Spike pseudotype, however potency was reduced in a small number of samples (3 of 36) by 5–10-fold. This work highlights that changes in the SARS-CoV-2 Spike can alter neutralization sensitivity and underlines the need for effective real-time monitoring of emerging mutations and their impact on vaccine efficacy.

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The use of pseudotyped coronaviruses for the screening of entry inhibitors: Green tea extract inhibits the entry of SARS-CoV-1, MERS-CoV, and SARS-CoV-2 by blocking receptor-spike interaction

Current Pharmaceutical Biotechnology ◽

10.2174/1389201022666210810111716 ◽

2021 ◽

Vol 22 ◽

Author(s):

Jeswin Joseph ◽

Thankamani Karthika ◽

V.R. Akshay Das ◽

V. Stalin Raj

Keyword(s):

Green Tea ◽

Viral Entry ◽

Neutralizing Antibodies ◽

High Titer ◽

Antiviral Agents ◽

Natural Compounds ◽

Cell Surface Receptor ◽

Soluble Form ◽

Entry Inhibitors ◽

Wide Range

Background: Coronaviruses (CoVs) infect a wide range of animals and birds. Their tropism is primarily determined by the ability of the spike protein to bind to a host cell surface receptor. The ongoing outbreak of SARS-CoV-2 inculcates the need for the development of effective intervention strategies. Objectives: In this study, we aim to produce pseudotyped coronaviruses of SARS-CoV-1, MERS-CoV, and SARS-CoV-2 and show its applications, including virus entry, neutralization, and screening of entry inhibitors from natural products. Methods: Here, we generated VSV-based pseudotyped coronaviruses (CoV-PVs) for SARS-CoV-1, MERS-CoV, and SARS-CoV-2. Recombinant spike proteins of SARS-CoV-1, MERS-CoV, and SARS-CoV-2 were transiently expressed in HEK293T cells followed by infection with recombinant VSV. High titer pseudoviruses were harvested and subjected to distinct validation assays, which confirms the proper spike pseudotyping. Further, specific receptor-mediated entry was confirmed by antibody neutralization and soluble form of receptor inhibition assay on Vero E6 cells. Next, these CoV-PVs were used for screening of antiviral activity of natural compounds such as green tea and Spirulina extract. Results: Medicinal plants and natural compounds have been traditionally used as antiviral agents. In the first series of experiments, we demonstrated that pseudotyped viruses specifically bind to their receptors for cellular entry. SARS-CoV-1 and MERS-CoV anti-sera neutralize SARS-CoV-1-PV and SARS-CoV-2-PV, and MERS-CoV-PV, respectively. Incubation of soluble ACE2 with CoV-PVs inhibited entry of SARS-CoV-1 and SARS-CoV-2 PVs but not MERS-CoV-PV. Also, transient expression of ACE2 and DPP4 in non-permissive BHK21 cells enabled infection by SARS-CoV-1-PV, SARS-CoV-2-PV, and MERS-CoV-PV, respectively. Next, we showed the antiviral properties of known entry inhibitors of enveloped viruses, Spirulina, and green tea extracts against CoV-PVs. SARS-CoV-1-PV, MERS-CoV-PV, and SARS-CoV-2-PV entry was blocked with higher efficiency when preincubated with either green tea or Spirulina extracts. Green tea provided a better inhibitory effect by binding to the S1 domain of the spike and blocking the spike interaction with its receptor. Conclusion: In summary, we demonstrated that pseudotyped viruses are an ideal tool for studying viral entry, quantification of neutralizing antibodies, and screening of entry inhibitors in a BSL-2 facility. Moreover, green tea might be a promising natural remedy against emerging coronaviruses.

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What serosurveillance studies tell us about the 2009 influenza pandemic

Microbiology Australia ◽

10.1071/ma11018 ◽

2011 ◽

Vol 32 (1) ◽

pp. 18

Author(s):

Gary K Dowse ◽

Ian Barr

Keyword(s):

Influenza Pandemic ◽

Herd Immunity ◽

Case Fatality ◽

Antigenic Drift ◽

Surveillance Systems ◽

Pandemic H1n1 ◽

Infection Rates ◽

Vaccination Programs ◽

Pandemic Virus ◽

The Impact

Surveillance of the impact of pandemic (H1N1) 2009 influenza during its initial seasons in both hemispheres relied on routinely available indicators, including numbers and rates of laboratory-detected cases, hospitalisations, ICU admissions and deaths, along with monitoring of influenza-like illness (ILI) from primary care sentinel surveillance systems. Estimates of the clinical attack rate and the case fatality ratio were imperfect. Understanding of the pathogenicity of the pandemic virus and prediction of the impact in subsequent seasons was hindered by a lack of information on actual infection rates in the population. Results of a number of serosurveys conducted in Australia and overseas countries have now become available, revealing that the arrival of the pandemic virus in modern urbanised and non-immune populations resulted in relatively similar infection rates in both the southern and northern hemispheres. Around 30?50% of children and teenagers were infected during the first pandemic season, with lower rates, around 10?20%, in young and middle-aged adults, and very few infections in older adults. There were significant numbers of mild or asymptomatic infections, and case fatality and hospitalisation ratios were much lower than those contemplated in pandemic plans. Many populations, including Australia, achieved a significant level of herd immunity during the first wave, and community susceptibility was further reduced by vaccination programs, although coverage was lower than expected. In the absence of significant antigenic drift or changes in virulence, the impact of the pandemic H1N1 virus should continue to decline in future influenza seasons.

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A safe and convenient pseudovirus-based inhibition assay to detect neutralizing antibodies and screen for viral entry inhibitors against the novel human coronavirus MERS-CoV

Virology Journal ◽

10.1186/1743-422x-10-266 ◽

2013 ◽

Vol 10 (1) ◽

pp. 266 ◽

Cited By ~ 73

Author(s):

Guangyu Zhao ◽

Lanying Du ◽

Cuiqing Ma ◽

Ye Li ◽

Lin Li ◽

...

Keyword(s):

Viral Entry ◽

Neutralizing Antibodies ◽

The Novel ◽

Inhibition Assay ◽

Human Coronavirus ◽

Entry Inhibitors

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Virus-free and live-cell visualizing SARS-CoV-2 cell entry for studies of neutralizing antibodies and compound inhibitors

10.1101/2020.07.22.215236 ◽

2020 ◽

Author(s):

Yali Zhang ◽

Shaojuan Wang ◽

Yangtao Wu ◽

Wangheng Hou ◽

Lunzhi Yuan ◽

...

Keyword(s):

Viral Entry ◽

High Throughput Screening ◽

Neutralizing Antibodies ◽

Fluorescent Protein ◽

Expression System ◽

Live Cell ◽

Phenotypic Characterization ◽

Visualization System ◽

Entry Inhibitors ◽

Versatile Tool

AbstractThe ongoing COVID-19 pandemic, caused by SARS-CoV-2 infection, has resulted in hundreds of thousands of deaths. Cellular entry of SARS-CoV-2, which is mediated by the viral spike protein and host ACE2 receptor, is an essential target for the development of vaccines, therapeutic antibodies, and drugs. Using a mammalian cell expression system, we generated a recombinant fluorescent protein (Gamillus)-fused SARS-CoV-2 spike trimer (STG) to probe the viral entry process. In ACE2-expressing cells, we found that the STG probe has excellent performance in the live-cell visualization of receptor binding, cellular uptake, and intracellular trafficking of SARS-CoV-2 under virus-free conditions. The new system allows quantitative analyses of the inhibition potentials and detailed influence of COVID-19-convalescent human plasmas, neutralizing antibodies and compounds, providing a versatile tool for high-throughput screening and phenotypic characterization of SARS-CoV-2 entry inhibitors. This approach may also be adapted to develop a viral entry visualization system for other viruses.

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