SARS-CoV-2 spike S2-specific neutralizing antibodies.

Since the onset of the coronavirus disease 2019 (COVID-19), numerous neutralizing antibodies (NAbs) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been developed and authorized for emergency use to control the pandemic. Most COVID-19 therapeutic NAbs prevent the S1 subunit of the SARS-CoV-2 spike (S) protein from binding to the human host receptor. However, the emergence of SARS-CoV-2 immune escape variants, which possess frequent mutations on the S1 subunit, may render current NAbs ineffective. In contrast, the relatively conserved S2 subunit of the S protein can elicit NAbs with broader neutralizing potency against various SARS-CoV-2 variants. In this review, the binding specificity and functional features of SARS-CoV-2 NAbs targeting different domains of the S2 subunit are collectively discussed. The knowledge learned from the investigation of the S2-specific NAbs provides insights and potential strategies for developing antibody cocktail therapy and next-generation coronavirus vaccine.

Research progress on action mechanism and preparation of monoclonal antibodies against 2019-nCoV.

During the treatment of critically ill COVID-19 patients it has been revealed that the neutralizing monoclonal antibodies against 2019-nCoV have the advantages of high specificity, high purity, and can be prepared in a large scale, which are expected to be a effective preparation for clinical use. This article introduces the way of 2019-nCoV invasion into the host cells, the major variants of novel coronavirus, and the mechanism of action of anti-2019-nCoV monoclonal antibodies, as well as the progress of research and development of their preparation in major pharmaceutical companies, to provide reference for scientific research and clinical application.Copyright © Chinese Journal of Clinical Infectious Diseases.All rights reserved.

Research progress on action mechanism and preparation of monoclonal antibodies against 2019-nCoV.

During the treatment of critically ill COVID-19 patients it has been revealed that the neutralizing monoclonal antibodies against 2019-nCoV have the advantages of high specificity, high purity, and can be prepared in a large scale, which are expected to be a effective preparation for clinical use. This article introduces the way of 2019-nCoV invasion into the host cells, the major variants of novel coronavirus, and the mechanism of action of anti-2019-nCoV monoclonal antibodies, as well as the progress of research and development of their preparation in major pharmaceutical companies, to provide reference for scientific research and clinical application.Copyright © Chinese Journal of Clinical Infectious Diseases.All rights reserved.

Molecular and Epidemiological Characterization of Emerging Immune-Escape Variants of SARS-CoV-2.

The successive emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants has presented a major challenge in the management of the coronavirus disease (COVID-19) pandemic. There are growing concerns regarding the emerging variants escaping vaccines or therapeutic neutralizing antibodies. In this study, we conducted an epidemiological survey to identify SARS-CoV-2 variants that are sporadically proliferating in vaccine-advanced countries. Subsequently, we created HiBiT-tagged virus-like particles displaying spike proteins derived from the variants to analyze the neutralizing efficacy of the BNT162b2 mRNA vaccine and several therapeutic antibodies. We found that the Mu variant and a derivative of the Delta strain with E484K and N501Y mutations significantly evaded vaccine-elicited neutralizing antibodies. This trend was also observed in the Beta and Gamma variants, although they are currently not prevalent. Although 95.2% of the vaccinees exhibited prominent neutralizing activity against the prototype strain, only 73.8 and 78.6% of the vaccinees exhibited neutralizing activity against the Mu and the Delta derivative variants, respectively. A long-term analysis showed that 88.8% of the vaccinees initially exhibited strong neutralizing activity against the currently circulating Delta strain; the number decreased to 31.6% for the individuals at 6 months after vaccination. Notably, these variants were shown to be resistant to several therapeutic antibodies. Our findings demonstrate the differential neutralization efficacy of the COVID-19 vaccine and monoclonal antibodies against circulating variants, suggesting the need for pandemic alerts and booster vaccinations against the currently prevalent variants.

Complexation of pillar[5]arene-based schiff bases with methylene blue: formation of binary complexes with improved anticancer activity

Cocktail therapy is one of the leading approaches for treating some complex diseases. Herein, a pH-triggered supramolecular cocktail drug delivery system assembled by the medium-strength complexes of pillar[5]arene-based schiff base (P5SB) with methylene blue (MB). Molecular modeling suggest that noncovalent interactions between schiff base side chain of P5SB and MB were mainly responsible for the stability of the complex. The amphiphilic P5SB⊃MB complex assembled into stable vesicles with an average diameter of 244.1 nm in conventional physiological environment (pH=7.4). Drug loading experiments demonstrated that doxorubicin (DOX) could be efficiently encapsulated into the hollow vesicles, and the drug would be rapidly released under acidic environment (pH=6.0). Moreover, the anti-cancer efficiency of DOX-loaded P5SB⊃MB vesicles was significantly enhanced because of the synergistic effect of P5SB, MB and DOX. Nonetheless, the live-cell imaging property of DOX was maintained after encapsulation.

Antibody cocktail effective against variants of SARS-CoV-2.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an RNA virus with a high mutation rate. Importantly, several currently circulating SARS-CoV-2 variants are associated with loss of efficacy for both vaccines and neutralizing antibodies. METHODS: We analyzed the binding activity of six highly potent antibodies to the spike proteins of SARS-CoV-2 variants, assessed their neutralizing abilities with pseudovirus and authentic SARS-CoV-2 variants and evaluate efficacy of antibody cocktail in Delta SARS-CoV-2-infected hamster models as prophylactic and post-infection treatments. RESULTS: The tested RBD-chAbs, except RBD-chAb-25, maintained binding ability to spike proteins from SARS-CoV-2 variants. However, only RBD-chAb-45 and -51 retained neutralizing activities; RBD-chAb-1, -15, -25 and -28 exhibited diminished neutralization for all SARS-CoV-2 variants. Notably, several cocktails of our antibodies showed low IC50 values (3.35-27.06 ng/ml) against the SARS-CoV-2 variant pseudoviruses including United Kingdom variant B.1.1.7 (Alpha), South Africa variant B.1.351 (Beta), Brazil variant P1 (Gamma), California variant B.1.429 (Epsilon), New York variant B.1.526 (Iota), and India variants, B.1.617.1 (Kappa) and B.1.617.2 (Delta). RBD-chAb-45, and -51 showed PRNT50 values 4.93-37.54 ng/ml when used as single treatments or in combination with RBD-chAb-15 or -28, according to plaque assays with authentic Alpha, Gamma and Delta SARS-CoV-2 variants. Furthermore, the antibody cocktail of RBD-chAb-15 and -45 exhibited potent prophylactic and therapeutic effects in Delta SARS-CoV-2 variant-infected hamsters. CONCLUSIONS: The cocktail of RBD-chAbs exhibited potent neutralizing activities against SARS-CoV-2 variants. These antibody cocktails are highly promising candidate tools for controlling new SARS-CoV-2 variants, including Delta.

Inhibition of SARS-CoV-2 pseudovirus invasion by ACE2 protecting and Spike neutralizing peptides: An alternative approach to COVID19 prevention and therapy.

SARS-CoV-2 invades host cells mainly through the interaction of its spike-protein with host cell membrane ACE2. Various antibodies targeting S-protein have been developed to combat COVID-19 pandemic; however, the potential risk of antibody-dependent enhancement and novel spike mutants-induced neutralization loss or antibody resistance still remain. Alternative preventative agents or therapeutics are still urgently needed. In this study, we designed series of peptides with either ACE2 protecting or Spike-protein neutralizing activities. Molecular docking predicted that, among these peptides, ACE2 protecting peptide AYp28 and Spike-protein neutralizing peptide AYn1 showed strongest intermolecular interaction to ACE2 and Spike-protein, respectively, which were further confirmed by both cell- and non-cell-based in vitro assays. In addition, both peptides inhibited the invasion of pseudotype SARS-CoV-2 into HEK293T/hACE2 cells, either alone or in combination. Moreover, the intranasal administration of AYp28 could partially block pseudovirus invasion in hACE2 transgenic mice. Much more importantly, no significant toxicity was observed in peptides-treated cells. AYp28 showed no impacts on ACE2 function. Taken together, the data from our present study predicted promising preventative and therapeutic values of peptides against COVID-19, and may prove the concept that cocktail containing ACE2 protecting peptides and spike neutralizing peptides could serve as a safe and effective approach for SARS-CoV-2 prevention and therapy.

Emerging antibody-based therapeutics against SARS-CoV-2 during the global pandemic.

SARS-CoV-2 antibody therapeutics are being evaluated in clinical and preclinical stages. As of 11 October 2020, 13 human monoclonal antibodies targeting the SARS-CoV-2 spike protein have entered clinical trials with three (REGN-COV2, LY3819253/LY-CoV555, and VIR-7831/VIR-7832) in phase 3. On 9 November 2020, the US Food and Drug Administration issued an emergency use authorization for bamlanivimab (LY3819253/LY-CoV555) for the treatment of mild-to-moderate COVID-19. This review outlines the development of neutralizing antibodies against SARS-CoV-2, with a focus on discussing various antibody discovery strategies (animal immunization, phage display and B cell cloning), describing binding epitopes and comparing neutralizing activities. Broad-neutralizing antibodies targeting the spike proteins of SARS-CoV-2 and SARS-CoV might be helpful for treating COVID-19 and future infections. VIR-7831/7832 based on S309 is the only antibody in late clinical development, which can neutralize both SARS-CoV-2 and SARS-CoV although it does not directly block virus receptor binding. Thus far, the only cross-neutralizing antibody that is also a receptor binding blocker is nanobody VHH-72. The feasibility of developing nanobodies as inhaled drugs for treating COVID-19 and other respiratory diseases is an attractive idea that is worth exploring and testing. A cocktail strategy such as REGN-COV2, or engineered multivalent and multispecific molecules, combining two or more antibodies might improve the efficacy and protect against resistance due to virus escape mutants. Besides the receptor-binding domain, other viral antigens such as the S2 subunit of the spike protein and the viral attachment sites such as heparan sulfate proteoglycans that are on the host cells are worth investigating.

The screening and evaluation of potential clinically significant HIV drug combinations against the SARS-CoV-2 virus.

Spike glycoprotein is essential for the reproduction of the SARS-CoV-2 virus, and its inhibition using already approved antiviral drugs may open new avenues for treatment of patients with the COVID-19 disease. Because of that we analyzed the inhibition of SARS-CoV-2 spike glycoprotein with FDA-approved antiviral drugs and their double and triple combinations. We used the VINI in silico model of cancer to perform this virtual drug screening, showing HIV drugs to be the most effective. Besides, the combination of cobicistat-abacavir-rilpivirine HIV drugs demonstrated the highest in silico efficacy of inhibiting SARS-CoV-2 spike glycoprotein. Therefore, a clinical trial of cobicistat-abacavir-rilpivirine on a limited number of COVID-19 patients in moderately severe and severe condition is warranted.