Antibody Therapy for the Control of Viral Diseases: An Update

Characterization of antibodies targeting severe fever with thrombocytopenia syndrome virus glycoprotein Gc

Severe fever with thrombocytopenia syndrome (SFTS) is a hemorrhagic fever caused by SFTS virus (SFTSV), which is primarily found in East Asian countries. Despite its high mortality rate and increasing incidence, no vaccines or therapeutics have yet been approved for use against SFTS. Antibody drugs have shown promise in treating lethal infectious diseases that currently have no established treatments. In the case of SFTS, however, only a limited amount of research has been done on SFTSV-neutralizing antibodies targeting the transmembrane proteins Gn and Gc, which play critical roles in viral infection. This study focuses on the production and characterization of antibodies targeting the SFTSV Gc protein. Monoclonal antibodies against Gc were generated through immunization of mice, and their antiviral activity was evaluated. Three out of four anti-Gc antibody clones from this study demonstrated dose-dependent SFTSV neutralization activity, two of which exhibited a synergistic effect on the neutralization activity of the anti-Gn antibody clone Mab4-5. Further studies are necessary to identify key sites on the SFTSV glycoprotein and to develop novel agents as well as antibodies with diverse mechanisms of action against SFTSV.

Dapoxetine, a Selective Serotonin Reuptake Inhibitor, Suppresses Zika Virus Infection In Vitro

Zika virus (ZIKV) belongs to the Flavivirus genus of the Flaviviridae family, and is a pathogen posing a significant threat to human health. Currently, there is a lack of internationally approved antiviral drugs for the treatment of ZIKV infection, and symptomatic management remains the primary clinical approach. Consequently, the exploration of safe and effective anti-ZIKV drugs has emerged as a paramount imperative in ZIKV control efforts. In this study, we performed a screening of a compound library consisting of 1789 FDA-approved drugs to identify potential agents with anti-ZIKV activity. We have identified dapoxetine, an orally administered selective serotonin reuptake inhibitor (SSRI) commonly employed for the clinical management of premature ejaculation (PE), as a potential inhibitor of ZIKV RNA-dependent RNA polymerase (RdRp). Consequently, we conducted surface plasmon resonance (SPR) analysis to validate the specific binding of dapoxetine to ZIKV RdRp, and further evaluated its inhibitory effect on ZIKV RdRp synthesis using the ZIKV Gluc reporter gene assay. Furthermore, we substantiated the efficacy of dapoxetine in suppressing intracellular replication of ZIKV, thereby demonstrating a concentration-dependent antiviral effect (EC50 values ranging from 4.20 μM to 12.6 μM) and negligible cytotoxicity (CC50 > 50 μM) across diverse cell lines. Moreover, cell fluorescence staining and Western blotting assays revealed that dapoxetine effectively reduced the expression of ZIKV proteins. Collectively, our findings suggest that dapoxetine exhibits anti-ZIKV effects by inhibiting ZIKV RdRp activity, positioning it as a potential candidate for clinical therapeutic intervention against ZIKV infection.

A combination of two resistance mechanisms is critical for tick-borne encephalitis virus escape from a broadly neutralizing human antibody

Tick-borne encephalitis virus (TBEV) is a flavivirus that causes human neuroinfections and represents a growing health problem. The human monoclonal antibody T025 targets envelope protein domain III (EDIII) of TBEV and related tick-borne flaviviruses, potently neutralizing TBEV in vitro and in preclinical models, representing a promising candidate for clinical development. We demonstrate that TBEV escape in the presence of T025 or T028 (another EDIII-targeting human monoclonal antibody) results in virus variants of reduced pathogenicity, characterized by distinct sets of amino acid changes in EDII and EDIII that are jointly needed to confer resistance. EDIII substitution K311N impairs formation of a salt bridge critical for T025-epitope interaction. EDII substitution E230K is not on the T025 epitope but likely induces quaternary rearrangements of the virus surface because of repulsion of positively charged residues on the adjacent EDI. A combination of T025 and T028 prevents virus escape and improves neutralization.

Vaccinal effect of HIV-1 antibody therapy: dream or reality?

PURPOSE OF REVIEW

This review summarizes recent studies reporting the induction of vaccinal effects by human immunodeficiency virus (HIV-1) antibody therapy. It also puts into perspective preclinical studies that have identified mechanisms involved in the immunomodulatory properties of antiviral antibodies. Finally, it discusses potential therapeutic interventions to enhance host adaptive immune responses in people living with HIV (PLWH) treated with broadly neutralizing antibodies (bNAbs).

RECENT FINDINGS

Recent studies in promising clinical trials have shown that, in addition to controlling viremia, anti-HIV-1 bNAbs are able to enhance the host's humoral and cellular immune response. Such vaccinal effects, in particular the induction of HIV-1-specific CD8 + T-cell responses, have been observed upon treatment with two potent bNAbs (3BNC117 and 10-1074) alone or in combination with latency-reversing agents (LRA). While these studies reinforce the idea that bNAbs can induce protective immunity, the induction of vaccinal effects is not systematic and might depend on both the virological status of the patient as well as the therapeutic strategy chosen.

SUMMARY

HIV-1 bNAbs can enhance adaptive host immune responses in PLWH. The challenge now is to exploit these immunomodulatory properties to design optimized therapeutic interventions to promote and enhance the induction of protective immunity against HIV-1 infection during bNAbs therapy.

Uses and Challenges of Antiviral Polyclonal and Monoclonal Antibody Therapies

Viral diseases represent a major public health concerns and ever-present risks for developing into future pandemics. Antiviral antibody therapeutics, either alone or in combination with other therapies, emerged as valuable preventative and treatment options, including during global emergencies. Here we will discuss polyclonal and monoclonal antiviral antibody therapies, focusing on the unique biochemical and physiological properties that make them well-suited as therapeutic agents. We will describe the methods of antibody characterization and potency assessment throughout development, highlighting similarities and differences between polyclonal and monoclonal products as appropriate. In addition, we will consider the benefits and challenges of antiviral antibodies when used in combination with other antibodies or other types of antiviral therapeutics. Lastly, we will discuss novel approaches to the characterization and development of antiviral antibodies and identify areas that would benefit from additional research.

A humanized anti-human adenovirus 55 monoclonal antibody with good neutralization ability

Background

Human adenovirus type 55 (HAdV55) has a re-emerged as pathogen causing an acute respiratory disease presenting as a severe lower respiratory illness that can cause death. To date, there is no HAdV55 vaccine or treatment available for general use.

Methods

Herein, a monoclonal antibody specific for HAdV55, mAb 9-8, was isolated from an scFv-phage display library derived from mice immunized with the purified inactived-HAdV55 virions. By using ELISA and a virus micro-neutralization assay, we evaluated the binding and neutralizing activity of mAb 9-8 following humanization. Western blotting analysis and antigen-antibody molecular docking analysis were used to identify the antigenic epitopes that the humanized monoclonal antibody 9-8-h2 recognized. After that, their thermal stability was determined.

Results

MAb 9-8 showed potent neutralization activity against HAdV55. After humanization, the humanized neutralizing monoclonal antibody (9-8-h2) was identified to neutralize HAdV55 infection with an IC50 of 0.6050 nM. The mAb 9-8-h2 recognized HAdV55 and HAdV7 virus particles, but not HAdV4 particles. Although mAb 9-8-h2 could recognize HAdV7, it could not neutralize HAdV7. Furthermore, mAb 9-8-h2 recognized a conformational neutralization epitope of the fiber protein and the crucial amino acid residues (Arg 288, Asp 157, and Asn 200) were identified. MAb 9-8-h2 also showed favorable general physicochemical properties, including good thermostability and pH stability.

Conclusions

Overall, mAb 9-8-h2 might be a promising molecule for the prevention and treatment of HAdV55.

Anti-HBc IgG Responses Occurring at the Early Phase of Infection Correlate Negatively with HBV Replication in a Mouse Model

Anti-HBc IgG is usually recognized as a diagnostic marker of hepatitis B, while the functional role anti-HBc IgG in HBV infection has not been fully elucidated. In this study, we firstly investigated the relationship between the anti-HBc IgG responses and the replication of HBV using AAV8-1.3HBV infected C57BL/6N mice. Our data showed that the anti-HBc IgG responses at the early phase of infection correlated negatively with the concentrations of circulating HBsAg and HBV DNA at both the early and chronic phases of infection. This observation was confirmed by an independent experiment using AAV8-1.3HBV infected C57BL/6J mice. Furthermore, to comprehend the potential causal relationship between the anti-HBc IgG responses and HBV infection, mice were treated with an anti-HBc monoclonal antibody at three days post AAV8-1.3HBV infection. Our data showed that the anti-HBc mAb significantly suppressed the fold increase of circulating HBsAg level, and the protective effect was not affected by NK cell depletion. Collectively, our study demonstrated that anti-HBc antibodies occurring at the early phase of HBV infection may contribute to the constraint of the virus replication, which might be developed as an immunotherapy for hepatitis B.

Adeno-associated virus mediated expression of monoclonal antibody MR191 protects mice against Marburg virus and provides long-term expression in sheep

Vectored monoclonal antibody (mAb) expression mediated by adeno-associated virus (AAV) gene delivery leads to sustained therapeutic mAb expression and protection against a wide range of infectious diseases in both small and large animal models, including nonhuman primates. Using our rationally engineered AAV6 triple mutant capsid, termed AAV6.2FF, we demonstrate rapid and robust expression of two potent human antibodies against Marburg virus, MR78 and MR191, following intramuscular (IM) administration. IM injection of mice with 1 × 1011 vector genomes (vg) of AAV6.2FF-MR78 and AAV6.2FF-MR191 resulted in serum concentrations of approximately 141 μg/mL and 195 μg/mL of human IgG, respectively, within the first four weeks. Mice receiving 1 × 1011 vg (high) and 1 × 1010 vg (medium) doses of AAV6.2FF-MR191 were completely protected against lethal Marburg virus challenge. No sex-based differences in serum human IgG concentrations were observed; however, administering the AAV-mAb over multiple injection sites significantly increased serum human IgG concentrations. IM administration of three two-week-old lambs with 5 × 1012 vg/kg of AAV6.2FF-MR191 resulted in serum human IgG expression that was sustained for more than 460 days, concomitant with low levels of anti-capsid and anti-drug antibodies. AAV-mAb expression is a viable method for prolonging the therapeutic effect of recombinant mAbs and represents a potential alternative "vaccine" strategy for those with compromised immune systems or in possible outbreak response scenarios.

Fc-Dependent Immunomodulation Induced by Antiviral Therapeutic Antibodies: New Perspectives for Eliciting Protective Immune Responses

The multiple mechanisms of action of antiviral monoclonal antibodies (mAbs) have made these molecules a potential therapeutic alternative for treating severe viral infections. In addition to their direct effect on viral propagation, several studies have shown that mAbs are able to enhance the host's adaptive immune response and generate long-lasting protective immunity. Such immunomodulatory effects occur in an Fc-dependent manner and rely on Fc-FcγR interactions. It is noteworthy that several FcγR-expressing cells have been shown to play a key role in enhancing humoral and cellular immune responses (so-called "vaccinal effects") in different experimental settings. This review recalls recent findings concerning the vaccinal effects induced by antiviral mAbs, both in several preclinical animal models and in patients treated with mAbs. It summarizes the main cellular and molecular mechanisms involved in these immunomodulatory properties of antiviral mAbs identified in different pathological contexts. It also describes potential therapeutic interventions to enhance host immune responses that could guide the design of improved mAb-based immunotherapies.

Elevated SARS-Cov-2-Specific IgM Levels Indicate Clinically Unfavorable Outcomes in Patients with COVID-19: A Retrospective Cohort Study

Background

COVID-19 outbreak began in Wuhan and pandemics occur. Although SARS-CoV-2-specific immunoglobulins have been detected in serum of COVID-19 patients, their dynamics and association with outcomes have not been fully characterized.

Methods

This retrospective cohort study investigated the association between SARS-CoV-2-specific immunoglobulins and clinical outcomes of COVID-19 patients. We recruited 137 participants who were diagnosed with COVID-19 in four wards of the Tongji Hospital in Wuhan, China. Among the 137 participants, 81 patients were recovered, 23 patients died, and 33 patients remained hospitalized by the end of the study. SARS-CoV-2-specific immunoglobulins were analyzed by chemiluminescence assays. Laboratory and radiological characteristics, and clinical outcomes were compared between the recovered group and the deceased group. Furthermore, a matched cohort study was conducted in which each non-survivor was matched to two recovered patients of similar age.

Results

SARS-CoV-2-specific IgM levels peaked in the fourth week after the onset of COVID-19, while serum IgG levels rose earlier and remained high up to the eighth week. In the age-matched cohort study, the serum IgM, but not IgG levels, were higher among the non-survivors than in the recovered group (P = 0.006). The area under the ROC curve for the IgM and IgG levels was 0.702 (95% CI: 0.560–0.845, P = 0.006) and 0.596 (95% confidence interval: 0.449–0.744, P = 0.194), respectively. We also showed that patients with COVID-19 who had high IgM or IgG levels (stratified according to best cut-off) exhibited significantly lower overall survival (Kaplan–Meier survival curves, P < 0.05).

Discussion

These results indicate the association between immunoglobulins and outcome in patients with COVID-19 and demonstrated that elevated serum IgM levels could indicate poor outcomes in patients with COVID-19. Further, the information about the profile of SARS-CoV-2-specific IgGs may be useful for the future epidemiological investigations of COVID-19 therapies.

Polyclonal alpaca antibodies protect against hantavirus pulmonary syndrome in a lethal Syrian hamster model

The use of antibody-based therapies for the treatment of high consequence viral pathogens has gained interest over the last fifteen years. Here, we sought to evaluate the use of unique camelid-based IgG antibodies to prevent lethal hantavirus pulmonary syndrome (HPS) in Syrian hamsters. Using purified, polyclonal IgG antibodies generated in DNA-immunized alpacas, we demonstrate that post-exposure treatments reduced viral burdens and organ-specific pathology associated with lethal HPS. Antibody treated animals did not exhibit signs of disease and were completely protected. The unique structures and properties, particularly the reduced size, distinct paratope formation and increased solubility of camelid antibodies, in combination with this study support further pre-clinical evaluation of heavy-chain only antibodies for treatment of severe respiratory diseases, including HPS.

Recent Advances in the Scaffold Engineering of Protein Binders

In recent years, extensive attention has been given to the generation of new classes of ligand- specific binding proteins to supplement monoclonal antibodies. A combination of protein engineering and display technologies has been used to manipulate non-human antibodies for humanization and stabilization purposes or even the generation of new binding proteins. Engineered protein scaffolds can now be directed against therapeutic targets to treat cancer and immunological disorders. Although very few of these scaffolds have successfully passed clinical trials, their remarkable properties such as robust folding, high solubility, and small size motivate their employment as a tool for biology and applied science studies. Here, we have focused on the generation of new non-Ig binding proteins and single domain antibody manipulation, with a glimpse of their applications.

Biochemistry, structure, and cellular internalization of a four nanobody-bearing Fc dimer

VHH stands for the variable regions of heavy chain only of camelid IgGs. The VHH family forms a set of interesting proteins derived from antibodies that maintain their capacity to recognize the antigen, despite their relatively small molecular weight (in the 12,000 Da range). Continuing our exploration of the possibilities of those molecules, we chose to design alternative molecules with maintained antigen recognition, but enhanced capacity, by fusing four VHH with one Fc, the fragment crystallizable region of antibodies. In doing so, we aimed at having a molecule with superior quantitative antigen recognition (×4) while maintaining its size below the 110 kDa. In the present paper, we described the building of those molecules that we coined VHH₂ -Fc-VHH₂ . The structure of VHH₂ -Fc-VHH₂ in complex with HER2 antigen was determined using electronic microscopy and modeling. The molecule is shown to bind four HER2 proteins at the end of its flexible arms. VHH₂ -Fc-VHH₂ also shows an internalization capacity via HER2 receptor superior to the reference anti-HER2 monoclonal antibody, Herceptin®, and to a simple fusion of two VHH with one Fc (VHH₂ -Fc). This new type of molecules, VHH₂ -Fc-VHH₂ , could be an interesting addition to the therapeutic arsenal with multiple applications, from diagnostic to therapy.

Differential and sequential immunomodulatory role of neutrophils and Ly6Chi inflammatory monocytes during antiviral antibody therapy

Antiviral monoclonal antibodies (mAbs) can generate protective immunity through Fc-FcγRs interactions. We previously showed a role for immune complexes (ICs) in the enhancement of antiviral T-cell responses through FcγR-mediated activation of dendritic cells (DCs). Here we addressed how mAb therapy in retrovirus-infected mice affects the activation of neutrophils and inflammatory monocytes, two FcγR-expressing innate effector cells rapidly recruited to sites of infection. We found that both cell-types activated in vitro by viral ICs secreted chemokines able to recruit monocytes and neutrophils themselves. Moreover, inflammatory cytokines potentiated chemokines and cytokines release by IC-activated cells and induced FcγRIV upregulation. Similarly, infection and mAb-treatment upregulated FcγRIV on neutrophils and inflammatory monocytes and enhanced their cytokines/chemokines secretion. Notably, upon antibody therapy neutrophils and inflammatory monocytes displayed distinct functional activation states and sequentially modulated the antiviral immune response by secreting Th1-type polarizing cytokines and chemokines, which occurred in a FcγRIV-dependent manner. Consistently, FcγRIV- blocking in mAb-treated, infected mice led to reduced immune protection. Our work provides new findings on the immunomodulatory role of neutrophils and monocytes in the enhancement of immune responses upon antiviral mAb therapy.

Therapeutic options for COVID-19: a quick review

Since the announcement by the World Health Organization (WHO) of an outbreak of a contagious respiratory viral pneumonia in Wuhan, China, in December 2019 (later named as COVID-19), several research works have been carried out to unstitch the therapeutic options and combat the disease using various aproaches and modalities. These works are currently at different clinical trial stages, and their results may be determined by the outcome of the ongoing trial process. There is the need for a collection of information regarding the availlable therapeutic options related to COVID-19. this article therefore reviewed emerging and re-emerging therapeutic compounds/drugs used in COVID-19 management and reports of clinical trials, with the view to summarize and highlight their prospect and possible adverse effects to allow more extensive choice by clinicians, researchers, and policymakers. The approach used involved retrieval of related collections found in selected repositories including, Medline, Scopus, PubMed, and Google scholar. Only experimental or clinical studies were included. Out of the 39 materials retrieved, 26 (66.67%) studies were based on clinical trials, 12 (30.77%) were classified as in vitro studies, and only one (2.56%) involved experimental animal study. Of the agents evaluated for COVID-19 therapeutics, 15 (38.46%) were anti-viral, four (10.26%) antimalarial, four studies were immunotherapeutics (10.26%), two studies (5.13%) were antibacterial, while, one (2.56%) study wasfor antiparasitic , anticoagulant, anti-inflammatory, anti-viral/antimalarial, and anti-viral/herbal combination for each. Also, eight studies (20.51%) were antibiotic/antimalarial.. This review indicates that there is both a race and quest in the test of antiviral agents against COVID-19 and that arbidol seems to have dominated in the studies analyzed. The use of anticoagulants and antibiotics, such as teicoplanin and azithromycin/hydroxychloroquine were reported to also play a leading role in the management of the disease. Likewise, dexamethasone has been recently claimed to be effective in patients in need of respiratory assistance. Based on unresolved controversies and inconclusive findings, it could be said that generally, a single and specific therapeutics to COVID-19 is still a mirage. There is, thus, an urgent need to test more potent compounds and agents to establish much safer and highly efficacious drugs/agents for the disease, even as we continue to learn more about the disease as well as the characteristic of the virus.

Immunomodulatory Role of NK Cells during Antiviral Antibody Therapy

Monoclonal antibodies (mAbs) are now considered as a therapeutic approach to prevent and treat severe viral infections. Using a mouse retroviral model, we showed that mAbs induce protective immunity (vaccinal effects). Here, we investigated the role of natural killer (NK) cells on this effect. NK cells are effector cells that are crucial to control viral propagation upon mAb treatment. However, their immunomodulatory activity during antiviral mAb immunotherapies has been little studied. Our data reveal that the mAb treatment of infected mice preserves the functional activation of NK cells. Importantly, functional NK cells play an essential role in preventing immune dysfunction and inducing antiviral protective immunity upon mAb therapy. Thus, NK cell depletion in mAb-treated, viral-infected mice leads to the upregulation of molecules involved in immunosuppressive pathways (i.e., PD-1, PD-L1 and CD39) on dendritic cells and T cells. NK cell depletion also abrogates the vaccinal effects induced by mAb therapy. Our data also reveal a role for IFNγ-producing NK cells in the enhancement of the B-cell responses through the potentiation of the B-cell helper properties of neutrophils. These findings suggest that preserved NK cell functions and counts might be required for achieving mAb-induced protective immunity. They open new prospects for improving antiviral immunotherapies.

Persistence of SARS-CoV-2-specific antibodies in COVID-19 patients

To better understand humoral immunity following SARS-CoV-2 infection, 114 hospitalised COVID-19 patients with antibody monitored over 8 weeks from symptom onset were retrospectively investigated. A total of 445 serum samples were assessed via chemiluminescence immunoassay. Positive rate of virus-specific IgM reached up to over 80% from the second week to the eighth week after symptom onset, then declined quickly to below 30% in the twelfth week. Concentrations of IgG remained high for at least 3 months before subsequently declining. As compared with the non-severe group, serum IgM level from week 3 to week 8 was significantly higher among the patients with severe clinical symptoms (P = 0.012) but not IgG (P = 0.053). Serum IgM level from week 3 to week 8 was correlated with positive virus RNA test (r = 0.201, P = 0.044), albumin level (r = -0.295, P = 0.003), lactic dehydrogenase (LDH) level (r = 0.292, P = 0.003), alkaline phosphatase (ALP) level (r = 0.254, P = 0.010), C-reactive protein (CRP) level (r = 0.281, P = 0.004) during the same course, while serum IgG level was correlated with age (r = 0.207, P = 0.038). This presented results provide insight into duration of SARS-CoV-2 antibodies and interaction between the virus and host systems.

Inhibitors of SARS-CoV-2 Entry: Current and Future Opportunities

Recently, a novel coronavirus initially designated 2019-nCoV but now termed SARS-CoV-2 has emerged and raised global concerns due to its virulence. SARS-CoV-2 is the etiological agent of "coronavirus disease 2019", abbreviated to COVID-19, which despite only being identified at the very end of 2019, has now been classified as a pandemic by the World Health Organization (WHO). At this time, no specific prophylactic or postexposure therapy for COVID-19 are currently available. Viral entry is the first step in the SARS-CoV-2 lifecycle and is mediated by the trimeric spike protein. Being the first stage in infection, entry of SARS-CoV-2 into host cells is an extremely attractive therapeutic intervention point. Within this review, we highlight therapeutic intervention strategies for anti-SARS-CoV, MERS-CoV, and other coronaviruses and speculate upon future directions for SARS-CoV-2 entry inhibitor designs.

Antiviral therapies: advances and perspectives

Viral infections cause high morbidity and mortality, threaten public health, and impose a socioeconomic burden. We have seen the recent emergence of SARS‐CoV‐2 (Severe Acute Respiratory Syndrome Coronavirus 2), the causative agent of COVID‐19 that has already infected more than 29 million people, with more than 900 000 deaths since its identification in December 2019. Considering the significant impact of viral infections, research and development of new antivirals and control strategies are essential. In this paper, we summarize 96 antivirals approved by the Food and Drug Administration between 1987 and 2019. Of these, 49 (51%) are used in treatments against human immunodeficiency virus (HIV), four against human papillomavirus, six against cytomegalovirus, eight against hepatitis B virus, five against influenza, six against herpes simplex virus, 17 against hepatitis C virus and one against respiratory syncytial virus. This review also describes future perspectives for new antiviral therapies such as nanotechnologies, monoclonal antibodies and the CRISPR‐Cas system. These strategies are suggested as inhibitors of viral replication by various means, such as direct binding to the viral particle, blocking the infection, changes in intracellular mechanisms or viral genes, preventing replication and virion formation. We also observed that a large number of viral agents have no therapy available and the majority of those approved in the last 32 years are restricted to some groups, especially anti‐HIV. Additionally, the emergence of new viruses and strains resistant to available antivirals has necessitated the formulation of new antivirals.

Bacteriophages Could Be a Potential Game Changer in the Trajectory of Coronavirus Disease (COVID-19)

The pandemic of the coronavirus disease (Covid-19) has caused the death of at least 270,000 people as of the 8th of May 2020. This work stresses the potential role of bacteriophages to decrease the mortality rate of patients infected by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. The indirect cause of mortality in Covid-19 is miscommunication between the innate and adaptive immune systems, resulting in a failure to produce effective antibodies against the virus on time. Although further research is urgently needed, secondary bacterial infections in the respiratory system could potentially contribute to the high mortality rate observed among the elderly due to Covid-19. If bacterial growth, together with delayed production of antibodies, is a significant contributing factor to Covid-19's mortality rate, then the additional time needed for the human body's adaptive immune system to produce specific antibodies could be gained by reducing the bacterial growth rate in the respiratory system of a patient. Independently of that, the administration of synthetic antibodies against SARS-CoV-2 viruses could potentially decrease the viral load. The decrease of bacterial growth and the covalent binding of synthetic antibodies to viruses should further diminish the production of inflammatory fluids in the lungs of patients (the indirect cause of death). Although the first goal could potentially be achieved by antibiotics, I argue that other methods may be more effective or could be used together with antibiotics to decrease the growth rate of bacteria, and that respective clinical trials should be launched.

Both goals can be achieved by bacteriophages. The bacterial growth rate could potentially be reduced by the aerosol application of natural bacteriophages that prey on the main species of bacteria known to cause respiratory failure and should be harmless to a patient. Independently of that, synthetically changed bacteriophages could be used to quickly manufacture specific antibodies against SARS-CoV-2. This can be done via a Nobel Prize awarded technique called “phage display.” If it works, the patient is given extra time to produce their own specific antibodies against the SARS-CoV-2 virus and stop the damage caused by an excessive immunological reaction.

Fab-Arm Exchange Combined with Selective Protein A Purification Results in a Platform for Rapid Preparation of Monovalent Bispecific Antibodies Directly from Culture Media

Bispecific antibody (bsAb) applications have exponentially expanded with the advent of molecular engineering strategies that have addressed many of the initial challenges, including improper light chain pairing, heterodimer purity, aggregation, and pharmacokinetics. However, the lack of high-throughput methods for the generation of monovalent bsAbs has resulted in a bottleneck that has hampered their therapeutic evaluation, as current technologies can be cost-prohibitive and impractical. To address this issue, we incorporated single-matched point mutations in the CH3 domain to recapitulate the physiological process of human IgG4 Fab-arm exchange to generate monovalent bsAbs. Furthermore, we utilized the substitutions H435R and Y436F in the CH3 domain of IgG1, which incorporates residues from human IgG3, thus ablating protein A binding. By exploiting this combination of mutations and optimizing the reduction and reoxidation conditions for Fab arm exchange, highly pure monovalent bsAbs can be rapidly purified directly from combined culture media using standard protein A purification. This methodology, reported herein for the first time, allows for the high-throughput generation of monovalent bsAbs, thus increasing the capacity for evaluating monovalent bsAb iterations for therapeutic potential.