Antibodies at work in the time of severe acute respiratory syndrome coronavirus 2

Antibody Therapy for COVID-19: Categories, Pros, and Cons

COVID-19 is a life-threatening respiratory disease triggered by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It has been considered a pandemic viral infection since December 2019. The investigation of the effective prophylaxis or therapeutic strategies for emergency management of the current condition has become a priority for medical research centers and pharmaceutical companies. This article provides a comprehensive review of antibody therapy and its different categories with their advantages and disadvantages for COVID-19 over the last few years of the current pandemic. Antibodies can be generated by active immunization, including natural infection with a pathogen and vaccination, or by the passive immunization method such as convalescent plasma therapy (CPT) and antibody synthesis in laboratories. Each of these ways has its characteristics. Arming the immune system with antibodies is the main aim of antiviral therapeutic procedures toward SARS-CoV-2. Collecting and discussing various aspects of available data in this field can give researchers a better perspective for the production of antibody-based products or selection of the most appropriate approach of antibody therapies to improve different cases of COVID-19. Moreover, it can help them control similar viral pandemics that may happen in the future appropriately.

Correlation between the binding affinity and the conformational entropy of nanobody SARS-CoV-2 spike protein complexes

Understanding the structural principles that determine the binding affinity of nanobodies to the spike protein of severe acute respiratory syndrome coronavirus 2 has been difficult. We analyzed electron microscopy maps of nanobody-spike complexes and quantified the conformational entropy of binding. This informed the design of an engineered nanobody with improved binding to the spike protein. This result offers a guiding principle for the rational maturation of nanobodies directed against the spike. High-binding potency nanobodies have been shown to be effective in animal models; thus, this technology could have application in future pandemics.

Camelid single-domain antibodies, also known as nanobodies, can be readily isolated from naïve libraries for specific targets but often bind too weakly to their targets to be immediately useful. Laboratory-based genetic engineering methods to enhance their affinity, termed maturation, can deliver useful reagents for different areas of biology and potentially medicine. Using the receptor binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein and a naïve library, we generated closely related nanobodies with micromolar to nanomolar binding affinities. By analyzing the structure–activity relationship using X-ray crystallography, cryoelectron microscopy, and biophysical methods, we observed that higher conformational entropy losses in the formation of the spike protein–nanobody complex are associated with tighter binding. To investigate this, we generated structural ensembles of the different complexes from electron microscopy maps and correlated the conformational fluctuations with binding affinity. This insight guided the engineering of a nanobody with improved affinity for the spike protein.

Adverse Audio-Vestibular Effects of Drugs and Vaccines Used in the Treatment and Prevention of COVID-19: A Review

(1) Background: The purpose of this article is to review pharmacological treatments for COVID-19 (currently approved by the EMA (European Medical Agency) and FDA (Food and Drug Administration)) and highlight their potential audio-vestibular side-effects as an ototoxic adverse reaction. (2) Methods: Review of the available literature in the scientific databases PubMed, ResearchGate, Scopus, and ScienceDirect, and in summaries of product data sheets. (3) Results: In accordance with EBM (evidence-based medicine) the treatment of COVID-19 by using lopinavir/ritonavir, chloroquine and hydroxychloroquine, azithromycin, favipiravir, amantadine, oseltamivir, and ivermectin is no longer recommended for patients suffering from COVID-19 due to a lack of clinical data, publications, and recommendations. There were 39 publications and 15 summaries of product characteristics (as other sources of data) which were also used in this analysis. Adverse events could be permanent or disappear over time. Following treatment for COVID-19, the most frequent adverse audio-vestibular reactions reported in clinical trials and publications in the area of audiology and otorhinolaryngology were: dizziness, blurry vision with dizziness, nasopharyngitis, dysgeusia, and tinnitus. As far as vaccines are concerned, dizziness as an ototoxic effect was uncommon and occurs only in hypersensitive people who experience anaphylactic shock. (4) Conclusions: The ototoxicity of the drugs discussed here does not have as severe symptoms as the drugs used in the treatment of COVID-19 in 2020 (e.g., hydroxychloroquine), and relates mainly to disorders of the vestibulocochlear system. However, there is still a need to monitor ototoxic side-effects because of potential interactions with other ototoxic drugs. Many of the drugs approved by EMA and FDA are new, and not every side-effect is known.

Nanobodies as powerful pulmonary targeted biotherapeutics against SARS-CoV-2, pharmaceutical point of view

Background Since December 2019, the newly emerged SARS-CoV-2 virus continues to infect humans and many people died from severe Covid-19 during the last 2 years worldwide. Different approaches are being used for treatment of this infection and its consequences, but limited results have been achieved and new therapeutics are still needed. One of the most interesting biotherapeutics in this era are Nanobodies which have shown very promising results in recent researches. Scope of review Here, we have reviewed the potentials of Nanobodies in Covid-19 treatment. We have also discussed the properties of these biotherapeutics that make them very suitable for pulmonary drug delivery, which seems to be very important route of administration in this disease. Major conclusion Nanobodies with their special biological and biophysical characteristics and their resistance against harsh manufacturing condition, can be considered as promising, targeted biotherapeutics which can be administered by pulmonary delivery pharmaceutical systems against Covid-19. General significance Covid-19 has become a global problem during the last two years and with emerging mutant strains, prophylactic and therapeutic approaches are still highly needed. Nanobodies with their specific properties can be considered as valuable and promising candidates in Covid-19 therapy.

SARS-CoV-2 Neutralizing Antibody Responses towards Full-Length Spike Protein and the Receptor-Binding Domain

Tools to monitor SARS-CoV-2 transmission and immune responses are needed. We present a neutralization ELISA to determine the levels of Ab-mediated virus neutralization and a preclinical model of focused immunization strategy. The ELISA is strongly correlated with the elaborate plaque reduction neutralization test (ρ = 0.9231, p < 0.0001). The neutralization potency of convalescent sera strongly correlates to IgG titers against SARS-CoV-2 receptor-binding domain (RBD) and spike (ρ = 0.8291 and 0.8297, respectively; p < 0.0001) and to a lesser extent with the IgG titers against protein N (ρ = 0.6471, p < 0.0001). The preclinical vaccine NMRI mice models using RBD and full-length spike Ag as immunogens show a profound Ab neutralization capacity (IC₅₀ = 1.9 × 10⁴ to 2.6 × 10⁴ and 3.9 × 10³ to 5.2 × 10³, respectively). Using a panel of novel high-affinity murine mAbs, we also show that a majority of the RBD-raised mAbs have inhibitory properties, whereas only a few of the spike-raised mAbs do. The ELISA-based viral neutralization test offers a time- and cost-effective alternative to the plaque reduction neutralization test. The immunization results indicate that vaccine strategies focused only on the RBD region may have advantages compared with the full spike.

Rapid, reliable, and reproducible cell fusion assay to quantify SARS-Cov-2 spike interaction with hACE2

COVID-19 is a global crisis of unimagined dimensions. Currently, Remedesivir is only fully licensed FDA therapeutic. A major target of the vaccine effort is the SARS-CoV-2 spike-hACE2 interaction, and assessment of efficacy relies on time consuming neutralization assay. Here, we developed a cell fusion assay based upon spike-hACE2 interaction. The system was tested by transient co-transfection of 293T cells, which demonstrated good correlation with standard spike pseudotyping for inhibition by sera and biologics. Then established stable cell lines were very well behaved and gave even better correlation with pseudotyping results, after a short, overnight co-incubation. Results with the stable cell fusion assay also correlated well with those of a live virus assay. In summary we have established a rapid, reliable, and reproducible cell fusion assay that will serve to complement the other neutralization assays currently in use, is easy to implement in most laboratories, and may serve as the basis for high throughput screens to identify inhibitors of SARS-CoV-2 virus-cell binding and entry.

Diverse Immunological Factors Influencing Pathogenesis in Patients with COVID-19: A Review on Viral Dissemination, Immunotherapeutic Options to Counter Cytokine Storm and Inflammatory Responses

The pathogenesis of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is still not fully unraveled. Though preventive vaccines and treatment methods are out on the market, a specific cure for the disease has not been discovered. Recent investigations and research studies primarily focus on the immunopathology of the disease. A healthy immune system responds immediately after viral entry, causing immediate viral annihilation and recovery. However, an impaired immune system causes extensive systemic damage due to an unregulated immune response characterized by the hypersecretion of chemokines and cytokines. The elevated levels of cytokine or hypercytokinemia leads to acute respiratory distress syndrome (ARDS) along with multiple organ damage. Moreover, the immune response against SARS-CoV-2 has been linked with race, gender, and age; hence, this viral infection's outcome differs among the patients. Many therapeutic strategies focusing on immunomodulation have been tested out to assuage the cytokine storm in patients with severe COVID-19. A thorough understanding of the diverse signaling pathways triggered by the SARS-CoV-2 virus is essential before contemplating relief measures. This present review explains the interrelationships of hyperinflammatory response or cytokine storm with organ damage and the disease severity. Furthermore, we have thrown light on the diverse mechanisms and risk factors that influence pathogenesis and the molecular pathways that lead to severe SARS-CoV-2 infection and multiple organ damage. Recognition of altered pathways of a dysregulated immune system can be a loophole to identify potential target markers. Identifying biomarkers in the dysregulated pathway can aid in better clinical management for patients with severe COVID-19 disease. A special focus has also been given to potent inhibitors of proinflammatory cytokines, immunomodulatory and immunotherapeutic options to ameliorate cytokine storm and inflammatory responses in patients affected with COVID-19.

Role of Inflammatory Cytokines in COVID-19 Patients: A Review on Molecular Mechanisms, Immune Functions, Immunopathology and Immunomodulatory Drugs to Counter Cytokine Storm

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a severe pandemic of the current century. The vicious tentacles of the disease have been disseminated worldwide with unknown complications and repercussions. Advanced COVID-19 syndrome is characterized by the uncontrolled and elevated release of pro-inflammatory cytokines and suppressed immunity, leading to the cytokine storm. The uncontrolled and dysregulated secretion of inflammatory and pro-inflammatory cytokines is positively associated with the severity of the viral infection and mortality rate. The secretion of various pro-inflammatory cytokines such as TNF-α, IL-1, and IL-6 leads to a hyperinflammatory response by recruiting macrophages, T and B cells in the lung alveolar cells. Moreover, it has been hypothesized that immune cells such as macrophages recruit inflammatory monocytes in the alveolar cells and allow the production of large amounts of cytokines in the alveoli, leading to a hyperinflammatory response in severely ill patients with COVID-19. This cascade of events may lead to multiple organ failure, acute respiratory distress, or pneumonia. Although the disease has a higher survival rate than other chronic diseases, the incidence of complications in the geriatric population are considerably high, with more systemic complications. This review sheds light on the pivotal roles played by various inflammatory markers in COVID-19-related complications. Different molecular pathways, such as the activation of JAK and JAK/STAT signaling are crucial in the progression of cytokine storm; hence, various mechanisms, immunological pathways, and functions of cytokines and other inflammatory markers have been discussed. A thorough understanding of cytokines' molecular pathways and their activation procedures will add more insight into understanding immunopathology and designing appropriate drugs, therapies, and control measures to counter COVID-19. Recently, anti-inflammatory drugs and several antiviral drugs have been reported as effective therapeutic drug candidates to control hypercytokinemia or cytokine storm. Hence, the present review also discussed prospective anti-inflammatory and relevant immunomodulatory drugs currently in various trial phases and their possible implications.

Repurposing Chloroquine Against Multiple Diseases With Special Attention to SARS-CoV-2 and Associated Toxicity

Chloroquine and its derivatives have been used since ages to treat malaria and have also been approved by the FDA to treat autoimmune diseases. The drug employs pH-dependent inhibition of functioning and signalling of the endosome, lysosome and trans-Golgi network, immunomodulatory actions, inhibition of autophagy and interference with receptor binding to treat cancer and many viral diseases. The ongoing pandemic of COVID-19 has brought the whole world on the knees, seeking an urgent hunt for an anti-SARS-CoV-2 drug. Chloroquine has shown to inhibit receptor binding of the viral particles, interferes with their replication and inhibits "cytokine storm". Though multiple modes of actions have been employed by chloroquine against multiple diseases, viral diseases can provide an added advantage to establish the anti-SARS-CoV-2 mechanism, the in vitro and in vivo trials against SARS-CoV-2 have yielded mixed results. The toxicological effects and dosage optimization of chloroquine have been studied for many diseases, though it needs a proper evaluation again as chloroquine is also associated with several toxicities. Moreover, the drug is inexpensive and is readily available in many countries. Though much of the hope has been created by chloroquine and its derivatives against multiple diseases, repurposing it against SARS-CoV-2 requires large scale, collaborative, randomized and unbiased clinical trials to avoid false promises. This review summarizes the use and the mechanism of chloroquine against multiple diseases, its side-effects, mechanisms and the different clinical trials ongoing against "COVID-19".

Neutralizing Antibody Therapeutics for COVID-19

The emergence of SARS-CoV-2 and subsequent COVID-19 pandemic has resulted in a significant global public health burden, leading to an urgent need for effective therapeutic strategies. In this article, we review the role of SARS-CoV-2 neutralizing antibodies (nAbs) in the clinical management of COVID-19 and provide an overview of recent randomized controlled trial data evaluating nAbs in the ambulatory, hospitalized and prophylaxis settings. Two nAb cocktails (casirivimab/imdevimab and bamlanivimab/etesevimab) and one nAb monotherapy (bamlanivimab) have been granted Emergency Use Authorization by the US Food and Drug Administration for the treatment of ambulatory patients who have a high risk of progressing to severe disease, and the European Medicines Agency has similarly recommended both cocktails and bamlanivimab monotherapy for use in COVID-19 patients who do not require supplemental oxygen and who are at high risk of progressing to severe COVID-19. Efficacy of nAbs in hospitalized patients with COVID-19 has been varied, potentially highlighting the challenges of antiviral treatment in patients who have already progressed to severe disease. However, early data suggest a promising prophylactic role for nAbs in providing effective COVID-19 protection. We also review the risk of treatment-emergent antiviral resistant "escape" mutants and strategies to minimize their occurrence, discuss the susceptibility of newly emerging SARS-COV-2 variants to nAbs, as well as explore administration challenges and ways to improve patient access.

Models to inform neutralizing antibody therapy strategies during pandemics: the case of SARS-CoV-2

Background

Neutralizing antibodies (nAbs) against SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) can play an important role in reducing impacts of the COVID-19 pandemic, complementing ongoing public health efforts such as diagnostics and vaccination. Rapidly designing, manufacturing and distributing nAbs requires significant planning across the product value chain and an understanding of the opportunities, challenges and risks throughout.

Methods

A systems framework comprised of four critical components is presented to aid in developing effective end-to-end nAbs strategies in the context of a pandemic: (1) product design and optimization, (2) epidemiology, (3) demand and (4) supply. Quantitative models are used to estimate product demand using available epidemiological data, simulate biomanufacturing operations from typical bioprocess parameters and calculate antibody production costs to meet clinical needs under various realistic scenarios.

Results

In a US-based case study during the 9-month period from March 15 to December 15, 2020, the projected number of SARS-CoV-2 infections was 15.73 million. The estimated product volume needed to meet therapeutic demand for the maximum number of clinically eligible patients ranged between 6.3 and 31.5 tons for 0.5 and 2.5 g dose sizes, respectively. The relative production scale and cost needed to meet demand are calculated for different centralized and distributed manufacturing scenarios.

Conclusions

Meeting demand for anti-SARS-CoV-2 nAbs requires significant manufacturing capacity and planning for appropriate administration in clinical settings. MIT Center for Biomedical Innovation’s data-driven tools presented can help inform time-critical decisions by providing insight into important operational and policy considerations for making nAbs broadly accessible, while considering time and resource constraints.

Anti-SARS-CoV-2 neutralizing monoclonal antibodies: clinical pipeline

Monoclonal antibody (mAb) therapy has been previously exploited for viral infections, such as respiratory syncytial virus pneumonia and Ebolavirus disease. In the ongoing COVID-19 pandemic, early signals of efficacy from convalescent plasma therapy have encouraged research and development of anti-SARS-CoV-2 mAbs. While many candidates are in preclinical development, we focus here on anti-SARS-CoV-2 neutralizing mAbs (or mAb cocktails) that represent the late-stage clinical pipeline, i.e., those currently in Phase 2 or Phase 3 clinical trials. We describe the structure, mechanism of action, and ongoing trials for VIR-7831, LY-CoV555, LY-CoV016, BGB-DXP593, REGN-COV2, and CT-P59. We speculate also on the next generation of these mAbs.