A perspective on potential antibody-dependent enhancement of SARS-CoV-2

Breadth of SARS-CoV-2 Neutralization and Protection Induced by a Nanoparticle Vaccine

Coronavirus vaccines that are highly effective against SARS-CoV-2 variants are needed to control the current pandemic. We previously reported a receptor-binding domain (RBD) sortase A-conjugated ferritin nanoparticle (RBD-scNP) vaccine that induced neutralizing antibodies against SARS-CoV-2 and pre-emergent sarbecoviruses and protected monkeys from SARS-CoV-2 WA-1 infection. Here, we demonstrate SARS-CoV-2 RBD-scNP immunization induces potent neutralizing antibodies in non-human primates (NHPs) against all eight SARS-CoV-2 variants tested including the Beta, Delta, and Omicron variants. The Omicron variant was neutralized by RBD-scNP-induced serum antibodies with a mean of 10.6-fold reduction of ID50 titers compared to SARS-CoV-2 D614G. Immunization with RBD-scNPs protected NHPs from SARS-CoV-2 WA-1, Beta, and Delta variant challenge, and protected mice from challenges of SARS-CoV-2 Beta variant and two other heterologous sarbecoviruses. These results demonstrate the ability of RBD-scNPs to induce broad neutralization of SARS-CoV-2 variants and to protect NHPs and mice from multiple different SARS-related viruses. Such a vaccine could provide the needed immunity to slow the spread of and reduce disease caused by SARS-CoV-2 variants such as Delta and Omicron.

Hyperimmune immunoglobulin for hospitalised patients with COVID-19 (ITAC): a double-blind, placebo-controlled, phase 3, randomised trial

BACKGROUND

Passive immunotherapy using hyperimmune intravenous immunoglobulin (hIVIG) to SARS-CoV-2, derived from recovered donors, is a potential rapidly available, specific therapy for an outbreak infection such as SARS-CoV-2. Findings from randomised clinical trials of hIVIG for the treatment of COVID-19 are limited.

METHODS

In this international randomised, double-blind, placebo-controlled trial, hospitalised patients with COVID-19 who had been symptomatic for up to 12 days and did not have acute end-organ failure were randomly assigned (1:1) to receive either hIVIG or an equivalent volume of saline as placebo, in addition to remdesivir, when not contraindicated, and other standard clinical care. Randomisation was stratified by site pharmacy; schedules were prepared using a mass-weighted urn design. Infusions were prepared and masked by trial pharmacists; all other investigators, research staff, and trial participants were masked to group allocation. Follow-up was for 28 days. The primary outcome was measured at day 7 by a seven-category ordinal endpoint that considered pulmonary status and extrapulmonary complications and ranged from no limiting symptoms to death. Deaths and adverse events, including organ failure and serious infections, were used to define composite safety outcomes at days 7 and 28. Prespecified subgroup analyses were carried out for efficacy and safety outcomes by duration of symptoms, the presence of anti-spike neutralising antibodies, and other baseline factors. Analyses were done on a modified intention-to-treat (mITT) population, which included all randomly assigned participants who met eligibility criteria and received all or part of the assigned study product infusion. This study is registered with ClinicalTrials.gov, NCT04546581.

FINDINGS

From Oct 8, 2020, to Feb 10, 2021, 593 participants (n=301 hIVIG, n=292 placebo) were enrolled at 63 sites in 11 countries; 579 patients were included in the mITT analysis. Compared with placebo, the hIVIG group did not have significantly greater odds of a more favourable outcome at day 7; the adjusted OR was 1·06 (95% CI 0·77-1·45; p=0·72). Infusions were well tolerated, although infusion reactions were more common in the hIVIG group (18·6% vs 9·5% for placebo; p=0·002). The percentage with the composite safety outcome at day 7 was similar for the hIVIG (24%) and placebo groups (25%; OR 0·98, 95% CI 0·66-1·46; p=0·91). The ORs for the day 7 ordinal outcome did not vary for subgroups considered, but there was evidence of heterogeneity of the treatment effect for the day 7 composite safety outcome: risk was greater for hIVIG compared with placebo for patients who were antibody positive (OR 2·21, 95% CI 1·14-4·29); for patients who were antibody negative, the OR was 0·51 (0·29-0·90; pinteraction=0·001).

INTERPRETATION

When administered with standard of care including remdesivir, SARS-CoV-2 hIVIG did not demonstrate efficacy among patients hospitalised with COVID-19 without end-organ failure. The safety of hIVIG might vary by the presence of endogenous neutralising antibodies at entry.

FUNDING

US National Institutes of Health.

Neutralizing Antibodies and Antibody-Dependent Enhancement in COVID-19: A Perspective

Antibody-dependent enhancement (ADE) is an alternative route of viral entry in the susceptible host cell. In this process, antiviral antibodies enhance the entry access of virus in the cells via interaction with the complement or Fc receptors leading to the worsening of infection. SARS-CoV-2 variants pose a general concern for the efficacy of neutralizing antibodies that may fail to neutralize infection, raising the possibility of a more severe form of COVID-19. Data from various studies on respiratory viruses raise the speculation that antibodies elicited against SARS-CoV-2 and during COVID-19 recovery could potentially exacerbate the infection through ADE at sub-neutralizing concentrations; this may contribute to disease pathogenesis. It is, therefore, of utmost importance to study the effectiveness of the anti-SARS-CoV-2 antibodies in COVID-19-infected subjects. Theoretically, ADE remains a general concern for the efficacy of antibodies elicited during infection, most notably in convalescent plasma therapy and in response to vaccines where it could be counterproductive.

Human Antibodies for Viral Infections

Antibodies have been used to prevent or treat viral infections since the nineteenth century, but the full potential to use passive immunization for infectious diseases has yet to be realized. The advent of efficient methods for isolating broad and potently neutralizing human monoclonal antibodies is enabling us to develop antibodies with unprecedented activities. The discovery of IgG Fc region modifications that extend antibody half-life in humans to three months or more suggests that antibodies could become the principal tool with which we manage future viral epidemics. Antibodies for members of most virus families that cause severe disease in humans have been isolated, and many of them are in clinical development, an area that has accelerated during the effort to prevent or treat COVID-19 (coronavirus disease 2019). Broad and potently neutralizing antibodies are also important research reagents for identification of protective epitopes that can be engineered into active vaccines through structure-based reverse vaccinology. Expected final online publication date for the Annual Review of Immunology, Volume 40 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Immunology and Technology of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Vaccines

We have experienced an enormous cohesive effort of the scientific community to understand how the immune system reacts to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and how to elicit protective immunity via vaccination. This effort resulted in the development of vaccines in record time with high levels of safety, efficacy, and real-life effectiveness. However, the rapid diffusion of viral variants that escape protective antibodies prompted new studies to understand SARS-CoV-2 vulnerabilities and strategies to guide follow-up actions to increase, and maintain, the protection offered by vaccines. In this review, we report the main findings on human immunity to SARS-CoV-2 after natural infection and vaccination; we dissect the immunogenicity and efficacy of the different vaccination strategies that resulted in products widely used in the population; and we describe the impact of viral variants on vaccine-elicited immunity, summarizing the main discoveries and challenges to stay ahead of SARS-CoV-2 evolution. SIGNIFICANCE STATEMENT: This study reviewed findings on human immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), analyzed the immunogenicity and efficacy of the various vaccines currently used in large vaccination campaigns or candidates in advanced clinical development, and discussed the challenging task to ensure high protective efficacy against the rapidly evolving SARS-CoV-2 virus. This manuscript was completed prior to the emergence of the Omicron variant and to global vaccine boosting efforts.

A randomized, double-blind phase I clinical trial of two recombinant dimeric RBD COVID-19 vaccine candidates: Safety, reactogenicity and immunogenicity

Background

The Receptor Binding Domain (RBD) of the SARS-CoV-2 spike protein is the target for many COVID-19 vaccines. Here we report results for phase I clinical trial of two COVID-19 vaccine candidates based on recombinant dimeric RBD (d-RBD).

Methods

We performed a randomized, double-blind, phase I clinical trial in the National Centre of Toxicology in Havana. Sixty Cuban volunteers aged 19–59 years were randomized into three groups (20 subjects each): 1) FINLAY-FR-1 (50 µg d-RBD plus outer membrane vesicles from N. meningitidis); 2) FINLAY-FR-1A-50 (50 µg d-RBD, three doses); 3) FINLAY-FR-1A-25 (25 µg d-RDB, three doses). The FINLAY-FR-1 group was randomly divided to receive a third dose of the same vaccine candidate (homologous schedule) or FINLAY-FR-1A-50 (heterologous schedule). The primary outcomes were safety and reactogenicity. The secondary outcome was vaccine immunogenicity. Humoral response at baseline and following each vaccination was evaluated using live-virus neutralization test, anti-RBD IgG ELISA and in-vitro neutralization test of RBD:hACE2 interaction.

Results

Most adverse events were of mild intensity (63.5%), solicited (58.8%), and local (61.8%); 69.4% with causal association with vaccination. Serious adverse events were not found. The FINLAY-FR-1 group reported more subjects with adverse events than the other two groups. After the third dose, anti-RBD seroconversion was 100%, 94.4% and 90% for the FINLAY-FR-1, FINLAY-FR-1A-50 and FINLAY-FR-1A-25 respectively. The in-vitro inhibition of RBD:hACE2 interaction increased after the second dose in all formulations. The geometric mean neutralizing titres after the third dose rose significantly in the group vaccinated with FINLAY-FR-1 with respect to the other formulations and the COVID-19 Convalescent Serum Panel. No differences were found between FINLAY-FR-1 homologous or heterologous schedules.

Conclusions

Vaccine candidates were safe and immunogenic, and induced live-virus neutralizing antibodies against SARS-CoV-2. The highest values were obtained when outer membrane vesicles were used as adjuvant.

Trial registry: https://rpcec.sld.cu/en/trials/RPCEC00000338-En.

Anti-SARS-CoV-1 and -2 nanobody engineering towards avidity-inspired therapeutics

In the past two decades, the emergence of coronavirus diseases has been dire distress on both continental and global fronts and has resulted in the search for potent treatment strategies. One crucial challenge in this search is the recurrent mutations in the causative virus spike protein, which lead to viral escape issues. Among the current promising therapeutic discoveries is the use of nanobodies and nanobody-like molecules. While these nanobodies have demonstrated high-affinity interaction with the virus, the unpredictable spike mutations have warranted the need for avidity-inspired therapeutics of potent inhibitors such as nanobodies. This article discusses novel approaches for the design of anti-SARS-CoV-1 and -2 nanobodies to facilitate advanced innovations in treatment technologies. It further discusses molecular interactions and suggests multivalent protein nanotechnology and chemistry approaches to translate mere molecular affinity into avidity.

ACE2 can act as the secondary receptor in the FcγR-dependent ADE of SARS-CoV-2 infection

It is unknown whether antibody-mediated enhancement (ADE) contributes to the pathogenesis of COVID-19, and the conditions for ADE needs to be elucidated. We demonstrated that without inducing an ACE2-independent ADE on Raji cells, the neutralizing antibody CB6, a mouse anti-S1 serum and convalescent plasma, induced ADE on cells expressing FcγRIIA/CD32A and low levels of endogenous ACE2. ADE occurred at sub-neutralizing antibody concentrations, indicating that unneutralized S protein was required for ADE. The enhanced infectivity of 614G variant was higher than that of 614D wildtype in the presence of antibodies, further suggesting that ADE may be influenced by virus strains with different ACE2-binding affinity. Finally, knockdown of ACE2 or treatment with a fusion-inhibition peptide EK1C4 significantly reduced ADE. In conclusion, we identified an ADE mechanism mediated by neutralizing antibodies against SARS-CoV-2. ACE2 may act as a secondary receptor required for the antibody- and FcγR-mediated enhanced entry of SARS-CoV-2.

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NAbs induced ADE of SARS-CoV-2 on cells expressing FcγRIIA and ACE2

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Unneutralized S protein was required for ADE

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ADE may be influenced by virus strains with different ACE2-binding affinity

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ACE2 acts as a secondary receptor required for the Ab- and FcγR-mediated ADE

Characteristics of the first 1,119 SARS‐CoV‐2 Omicron variant cases, in Marseille, France, November‐December 2021

One thousand one hundred and nineteen cases of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) Omicron variant cases have been diagnosed at the Institut Hospitalo‐Universitaire Méditerranée Infection, Marseille, France, between November 28, 2021, and December 31, 2021. Among the 825 patients with known vaccination status, 383 (46.4%) were vaccinated, of whom 91.9% had received at least two doses of the vaccine. Interestingly, 26.3% of cases developed SARS‐CoV‐2 infection within 21 days following the last dose of vaccine suggesting possible early production of anti‐SARS‐CoV‐2 facilitating antibodies. Twenty‐one patients have been hospitalized, one patient required intensive care, and another patient who received a vaccine booster dose died.

Significantly low rates of hospitalization, transfer to Intensive Care Unit and death were observed in patients infected with Omicron as compared to those infected with Delta variant of severe acute respiratory syndrome coronavirus 2 during the same period,

26.3% of patients infected with Omicron get infected during the 3 weeks following COVID‐19 vaccination raising the question of facilitating antibodies.

ELISA-Based Analysis Reveals an Anti-SARS-CoV-2 Protein Immune Response Profile Associated with Disease Severity

Since the start of the COVID-19 pandemic, many studies have investigated the humoral response to SARS-CoV-2 during infection. Studies with native viral proteins constitute a first-line approach to assessing the overall immune response, but small peptides are an accurate and valuable tool for the fine characterization of B-cell epitopes, despite the restriction of this approach to the determination of linear epitopes. In this study, we used ELISA and peptides covering a selection of structural and non-structural SARS-CoV-2 proteins to identify key epitopes eliciting a strong immune response that could serve as a biological signature of disease characteristics, such as severity, in particular. We used 213 plasma samples from a cohort of patients well-characterized clinically and biologically and followed for COVID-19 infection. We found that patients developing severe disease had higher titers of antibodies mapping to multiple specific epitopes than patients with mild to moderate disease. These data are potentially important as they could be used for immunological profiling to improve our knowledge of the quantitative and qualitative characteristics of the humoral response in relation to patient outcome.

Computational Design of Miniproteins as SARS-CoV-2 Therapeutic Inhibitors

A rational therapeutic strategy is urgently needed for combating SARS-CoV-2 infection. Viral infection initiates when the SARS-CoV-2 receptor-binding domain (RBD) binds to the ACE2 receptor, and thus, inhibiting RBD is a promising therapeutic for blocking viral entry. In this study, the structure of lead antiviral candidate binder (LCB1), which has three alpha-helices (H1, H2, and H3), is used as a template to design and simulate several miniprotein RBD inhibitors. LCB1 undergoes two modifications: structural modification by truncation of the H3 to reduce its size, followed by single and double amino acid substitutions to enhance its binding with RBD. We use molecular dynamics (MD) simulations supported by ab initio density functional theory (DFT) calculations. Complete binding profiles of all miniproteins with RBD have been determined. The MD investigations reveal that the H3 truncation results in a small inhibitor with a -1.5 kcal/mol tighter binding to RBD than original LCB1, while the best miniprotein with higher binding affinity involves D17R or E11V + D17R mutation. DFT calculations provide atomic-scale details on the role of hydrogen bonding and partial charge distribution in stabilizing the minibinder:RBD complex. This study provides insights into general principles for designing potential therapeutics for SARS-CoV-2.

Pre-existing humoral immunity to human common cold coronaviruses negatively impacts the protective SARS-CoV-2 antibody response

SARS-CoV-2 infection causes diverse outcomes ranging from asymptomatic infection to respiratory distress and death. A major unresolved question is whether prior immunity to endemic, human common cold coronaviruses (hCCCoVs) impacts susceptibility to SARS-CoV-2 infection or immunity following infection and vaccination. Therefore, we analyzed samples from the same individuals before and after SARS-CoV-2 infection or vaccination. We found hCCCoV antibody levels increase after SARS-CoV-2 exposure, demonstrating cross-reactivity. However, a case-control study indicates that baseline hCCCoV antibody levels are not associated with protection against SARS-CoV-2 infection. Rather, higher magnitudes of pre-existing betacoronavirus antibodies correlate with more SARS-CoV-2 antibodies following infection, an indicator of greater disease severity. Additionally, immunization with hCCCoV spike proteins before SARS-CoV-2 immunization impedes the generation of SARS-CoV-2-neutralizing antibodies in mice. Together, these data suggest that pre-existing hCCCoV antibodies hinder SARS-CoV-2 antibody-based immunity following infection and provide insight on how pre-existing coronavirus immunity impacts SARS-CoV-2 infection, which is critical considering emerging variants.

SARS-CoV-2 and the Host Cell: A Tale of Interactions

The ability of a virus to spread between individuals, its replication capacity and the clinical course of the infection are macroscopic consequences of a multifaceted molecular interaction of viral components with the host cell. The heavy impact of COVID-19 on the world population, economics and sanitary systems calls for therapeutic and prophylactic solutions that require a deep characterization of the interactions occurring between virus and host cells. Unveiling how SARS-CoV-2 engages with host factors throughout its life cycle is therefore fundamental to understand the pathogenic mechanisms underlying the viral infection and to design antiviral therapies and prophylactic strategies. Two years into the SARS-CoV-2 pandemic, this review provides an overview of the interplay between SARS-CoV-2 and the host cell, with focus on the machinery and compartments pivotal for virus replication and the antiviral cellular response. Starting with the interaction with the cell surface, following the virus replicative cycle through the characterization of the entry pathways, the survival and replication in the cytoplasm, to the mechanisms of egress from the infected cell, this review unravels the complex network of interactions between SARS-CoV-2 and the host cell, highlighting the knowledge that has the potential to set the basis for the development of innovative antiviral strategies.

A Multifunctional Neutralizing Antibody-Conjugated Nanoparticle Inhibits and Inactivates SARS-CoV-2

The outbreak of 2019 coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in a global pandemic. Despite intensive research, the current treatment options show limited curative efficacies. Here the authors report a strategy incorporating neutralizing antibodies conjugated to the surface of a photothermal nanoparticle (NP) to capture and inactivate SARS-CoV-2. The NP is comprised of a semiconducting polymer core and a biocompatible polyethylene glycol surface decorated with high-affinity neutralizing antibodies. The multifunctional NP efficiently captures SARS-CoV-2 pseudovirions and completely blocks viral infection to host cells in vitro through the surface neutralizing antibodies. In addition to virus capture and blocking function, the NP also possesses photothermal function to generate heat following irradiation for inactivation of virus. Importantly, the NPs described herein significantly outperform neutralizing antibodies at treating authentic SARS-CoV-2 infection in vivo. This multifunctional NP provides a flexible platform that can be readily adapted to other SARS-CoV-2 antibodies and extended to novel therapeutic proteins, thus it is expected to provide a broad range of protection against original SARS-CoV-2 and its variants.

SARS-CoV-2 infections in children: understanding diverse outcomes

SARS-CoV-2 infections mostly lead to mild or even asymptomatic infections in children, but the reasons for this are not fully understood. More efficient local tissue responses, better thymic function, and cross-reactive immunity have all been proposed to explain this. In rare cases of children and young people, but very rarely in adults, post-infectious hyperinflammatory syndromes can develop and be serious. Here, I will discuss our current understanding of SARS-CoV-2 infections in children and hypothesize that a life history and energy allocation perspective might offer an additional explanation to mild infections, viral dynamics, and the higher incidence of rare multisystem inflammatory syndromes in children and young people.

Possibility of exosome‑based coronavirus disease 2019 vaccine (Review)

Coronavirus disease 2019 (COVID‑19) is a global pandemic that can have a long‑lasting impact on public health if not properly managed. Ongoing vaccine development trials involve classical molecular strategies based on inactivated or attenuated viruses, single peptides or viral vectors. However, there are multiple issues, such as the risk of reversion to virulence, inability to provide long‑lasting protection and limited protective immunity. To overcome the aforementioned drawbacks of currently available COVID‑19 vaccines, an alternative strategy is required to produce safe and efficacious vaccines that impart long‑term immunity. Exosomes (key intercellular communicators characterized by low immunogenicity, high biocompatibility and innate cargo‑loading capacity) offer a novel approach for effective COVID‑19 vaccine development. An engineered exosome‑based vaccine displaying the four primary structural proteins of SARS‑CoV‑2 (spike, membrane, nucleocapside and envelope proteins) induces humoral and cell mediated immunity and triggers long‑lasting immunity. The present review investigated the prospective use of exosomes in the development of COVID‑19 vaccines; moreover, exosome‑based vaccines may be key to control the COVID‑19 pandemic by providing enhanced protection compared with existing vaccines.

Review: Development of SARS-CoV-2 immuno-enhanced COVID-19 vaccines with nano-platform

Vaccination is the most effective way to prevent coronavirus disease 2019 (COVID-19). Vaccine development approaches consist of viral vector vaccines, DNA vaccine, RNA vaccine, live attenuated virus, and recombinant proteins, which elicit a specific immune response. The use of nanoparticles displaying antigen is one of the alternative approaches to conventional vaccines. This is due to the fact that nano-based vaccines are stable, able to target, form images, and offer an opportunity to enhance the immune responses. The diameters of ultrafine nanoparticles are in the range of 1-100 nm. The application of nanotechnology on vaccine design provides precise fabrication of nanomaterials with desirable properties and ability to eliminate undesirable features. To be successful, nanomaterials must be uptaken into the cell, especially into the target and able to modulate cellular functions at the subcellular levels. The advantages of nano-based vaccines are the ability to protect a cargo such as RNA, DNA, protein, or synthesis substance and have enhanced stability in a broad range of pH, ambient temperatures, and humidity for long-term storage. Moreover, nano-based vaccines can be engineered to overcome biological barriers such as nonspecific distribution in order to elicit functions in antigen presenting cells. In this review, we will summarize on the developing COVID-19 vaccine strategies and how the nanotechnology can enhance antigen presentation and strong immunogenicity using advanced technology in nanocarrier to deliver antigens. The discussion about their safe, effective, and affordable vaccines to immunize against COVID-19 will be highlighted.

Assessing the risk of vaccine-driven virulence evolution in SARS-CoV-2

The evolution of SARS-CoV-2 virulence, or lethality, threatens to exacerbate the burden of COVID-19 on society. How might COVID-19 vaccines alter selection for increased SARS-CoV-2 virulence? Framing current evidence surrounding SARS-CoV-2 biology and COVID-19 vaccines in the context of evolutionary theory indicates that prospects for virulence evolution remain uncertain. However, differential effects of vaccinal immunity on transmission and disease severity between respiratory compartments could select for increased virulence. To bound expectations for this outcome, we analyse an evo-epidemiological model. Synthesizing model predictions with vaccine efficacy data, we conclude that while vaccine-driven virulence remains a theoretical possibility, the risk is low if vaccines provide sustained robust protection against infection. Furthermore, we found that any increases in transmission concomitant with increases in virulence would be unlikely to threaten prospects for herd immunity in a highly immunized population. Given that virulence evolution would nevertheless impact unvaccinated individuals and populations with low vaccination rates, it is important to achieve high vaccination rates worldwide and ensure that vaccinal immunity provides robust protection against both infection and disease, potentially through the use of booster doses.

Antibodies: Friends, Foes, or Both? Lessons From COVID-19 for the Rheumatologist

ABSTRACT

Antibodies are a fundamental tool to fight infections but are intrinsically built as a double-edged sword. One side recognizes the microbial antigen, and the other gives a call to arms to fight infection by recruiting immune cells and triggering inflammation. A balanced immune response must combine a potent neutralizing antibody and a swift disposal of the invading agent by innate immune cells with the least tissue damage possible. The longer the immune system takes to control the infection, the higher the possibility for a self-sustaining inflammatory process with potentially fatal consequences for the host. In addition to quantity, the quality of antibodies also matters, because posttranslational modifications altering the N-glycan composition in Fc fractions may help tilt the balance to the effector side, by modifying their affinity for Fc receptors in immune cells. The COVID-19 pandemic has provided a wealth of data bolstering our understanding of the rules governing the production of protective and nonprotective antibodies. Also, it has broadened our understanding of the role of viruses in triggering autoimmunity and inflammation, and widened our knowledge of the different mechanisms that can be activated by viral infection and lead to autoantibody production, inflammation, and progressive tissue damage. In addition, the COVID-19 infection has contributed a great deal to our comprehension of the role of antibodies in the causation of cytokine storms and systemic inflammatory response syndrome, also seen in patients with systemic autoimmune diseases.

Vaccine-Associated Enhanced Disease and Pathogenic Human Coronaviruses

Vaccine-associated enhanced disease (VAED) is a difficult phenomenon to define and can be confused with vaccine failure. Using studies on respiratory syncytial virus (RSV) vaccination and dengue virus infection, we highlight known and theoretical mechanisms of VAED, including antibody-dependent enhancement (ADE), antibody-enhanced disease (AED) and Th2-mediated pathology. We also critically review the literature surrounding this phenomenon in pathogenic human coronaviruses, including MERS-CoV, SARS-CoV-1 and SARS-CoV-2. Poor quality histopathological data and a lack of consistency in defining severe pathology and VAED in preclinical studies of MERS-CoV and SARS-CoV-1 vaccines in particular make it difficult to interrogate potential cases of VAED. Fortuitously, there have been only few reports of mild VAED in SARS-CoV-2 vaccination in preclinical models and no observations in their clinical use. We describe the problem areas and discuss methods to improve the characterisation of VAED in the future.

Advances in the design and development of SARS-CoV-2 vaccines

Since the end of 2019, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide. The RNA genome of SARS-CoV-2, which is highly infectious and prone to rapid mutation, encodes both structural and nonstructural proteins. Vaccination is currently the only effective method to prevent COVID-19, and structural proteins are critical targets for vaccine development. Currently, many vaccines are in clinical trials or are already on the market. This review highlights ongoing advances in the design of prophylactic or therapeutic vaccines against COVID-19, including viral vector vaccines, DNA vaccines, RNA vaccines, live-attenuated vaccines, inactivated virus vaccines, recombinant protein vaccines and bionic nanoparticle vaccines. In addition to traditional inactivated virus vaccines, some novel vaccines based on viral vectors, nanoscience and synthetic biology also play important roles in combating COVID-19. However, many challenges persist in ongoing clinical trials.

The Journal of Clinical Investigation in the time of COVID-19

In this editorial, we describe the experience of the JCI editors during the COVID-19 pandemic. Our goal is to share how we operated during the pandemic, recount how the JCI contributed to the response, highlight some of the major papers we published on SARS-CoV-2 and COVID-19, and impart our insights in the hope that these are helpful to journal editors that may need to deal with similar types of crises in the future.

A serum-stable RNA aptamer specific for SARS-CoV-2 neutralizes viral entry

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has created an urgent need for new technologies to treat COVID-19. Here we report a 2'-fluoro protected RNA aptamer that binds with high affinity to the receptor binding domain (RBD) of SARS-CoV-2 spike protein, thereby preventing its interaction with the host receptor ACE2. A trimerized version of the RNA aptamer matching the three RBDs in each spike complex enhances binding affinity down to the low picomolar range. Binding mode and specificity for the aptamer-spike interaction is supported by biolayer interferometry, single-molecule fluorescence microscopy, and flow-induced dispersion analysis in vitro. Cell culture experiments using virus-like particles and live SARS-CoV-2 show that the aptamer and, to a larger extent, the trimeric aptamer can efficiently block viral infection at low concentration. Finally, the aptamer maintains its high binding affinity to spike from other circulating SARS-CoV-2 strains, suggesting that it could find widespread use for the detection and treatment of SARS-CoV-2 and emerging variants.

COVID-19 Vaccination: The Mainspring of Challenges and the Seed of Remonstrance

As of March 2020, the time when the coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) became a pandemic, our existence has been threatened and the lives of millions have been claimed. With this ongoing global issue, vaccines are considered of paramount importance in curtailing the outbreak and probably a prime gamble to bring us back to 'ordinary life'. To date, more than 200 vaccine candidates have been produced, many of which were approved by the Food and Drug Administration (FDA) for emergency use, with the research and discovery phase of their production process passed over. Capering such a chief practice in COVID-19 vaccine development, and manufacturing vaccines at an unprecedented speed brought many challenges into play and raised COVID-19 vaccine remonstrance. In this review, we highlight relevant challenges to global COVID-19 vaccine development, dissemination, and deployment, particularly at the level of large-scale production and distribution. We also delineate public perception on COVID-19 vaccination and outline the main facets affecting people's willingness to get vaccinated.

Mixed-charge modification as a robust method to realize the antiviral ability of gold nanoparticles in a high protein environment

Pandemics caused by viruses have resulted in incalculable losses to human beings, which are exacerbated due to the lack of antiviral drugs. Sulfonic group modified nanomedicine has been proved to possess a broad-spectrum antiviral ability. However, it is very challenging to maintain the antiviral activity in a high protein environment in vivo. To improve the tolerance to the complex biological environment, sulfonic mixed-charge modified gold nanoparticles (MC_AuNPs) were prepared in this research by introducing positively charged ligands into sulfonic ligand modified gold nanoparticles. The MC_AuNPs showed excellent non-fouling ability while retaining comparable antiviral ability to single sulfonic ligand modified gold nanoparticles (MDS_AuNPs). The MC_AuNPs maintained their antiviral ability in 10 mg mL^-1 protein solutions, but the MDS_AuNPs completely lost their antiviral capability in 1 mg mL^-1 protein medium. The mixed-charge modification strategy provides a practical avenue to maintain the antiviral capability of HSPG mimicking nanoparticles in high protein environments.

Antibody-Dependent Enhancement of SARS-CoV-2 Infection of Human Immune Cells: In Vitro Assessment Provides Insight in COVID-19 Pathogenesis

Patients with COVID-19 generally raise antibodies against SARS-CoV-2 following infection, and the antibody level is positively correlated to the severity of disease. Whether the viral antibodies exacerbate COVID-19 through antibody-dependent enhancement (ADE) is still not fully understood. Here, we conducted in vitro assessment of whether convalescent serum enhanced SARS-CoV-2 infection or induced excessive immune responses in immune cells. Our data revealed that SARS-CoV-2 infection of primary B cells, macrophages and monocytes, which express variable levels of FcγR, could be enhanced by convalescent serum from COVID-19 patients. We also determined the factors associated with ADE, and found which showed a time-dependent but not viral-dose dependent manner. Furthermore, the ADE effect is not associated with the neutralizing titer or RBD antibody level when testing serum samples collected from different patients. However, it is higher in a medium level than low or high dilutions in a given sample that showed ADE effect, which is similar to dengue. Finally, we demonstrated more viral genes or dysregulated host immune gene expression under ADE conditions compared to the no-serum infection group. Collectively, our study provides insight into the understanding of an association of high viral antibody titer and severe lung pathology in severe patients with COVID-19.

The potential of COVID-19 patients' sera to cause antibody-dependent enhancement of infection and IL-6 production

Since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), many vaccine trials have been initiated. An important goal of vaccination is the development of neutralizing antibody (Ab) against SARS-CoV-2. However, the possible induction of antibody-dependent enhancement (ADE) of infection, which is known for other coronaviruses and dengue virus infections, is a particular concern in vaccine development. Here, we demonstrated that human iPS cell-derived, immortalized, and ACE2- and TMPRSS2-expressing myeloid cell lines are useful as host cells for SARS-CoV-2 infection. The established cell lines were cloned and screened based on their function in terms of susceptibility to SARS-CoV-2-infection or IL-6 productivity. Using the resulting K-ML2 (AT) clone 35 for SARS-CoV-2-infection or its subclone 35–40 for IL-6 productivity, it was possible to evaluate the potential of sera from severe COVID-19 patients to cause ADE and to stimulate IL-6 production upon infection with SARS-CoV-2.

Mucosal AIDS virus transmission is enhanced by antiviral IgG isolated early in infection

OBJECTIVE

Antibody-dependent enhancement (ADE) affects host-virus dynamics in fundamentally different ways: i) enhancement of initial virus acquisition, and/or ii) increased disease progression/severity. Here we address the question whether anti-HIV-1 antibodies can enhance initial infection. While cell-culture experiments hinted at this possibility, in-vivo proof remained elusive.

DESIGN

We used passive immunization in nonhuman primates challenged with simian-human immunodeficiency virus (SHIV), a chimera expressing HIV-1 envelope. We purified IgG from rhesus monkeys with early-stage SHIV infection - before cross-neutralizing anti-HIV-1 antibodies had developed - and screened for maximal complement-mediated antibody-dependent enhancement (C'-ADE) of viral replication with a SHIV strain phylogenetically distinct from that harbored by IgG donor macaques. IgG fractions with maximal C'-ADE but lacking neutralization were combined to yield enhancing anti-SHIV IgG (enSHIVIG).

RESULTS

We serially enrolled naive macaques (Group 1) to determine the minimal and 50% animal infectious doses required to establish persistent infection after intrarectal SHIV challenge. The first animal was inoculated with a 1 : 10 virus-stock dilution; after this animal's viral RNA load was >104copies/ml, the next macaque was challenged with 10x less virus, a process repeated until viremia no longer ensued. Group 2 was pretreated intravenously with enSHIVIG 24 h before SHIV challenge. Overall, Group 2 macaques required 3.4-fold less virus compared to controls (P = 0.002). This finding is consistent with enhanced susceptibility of the passively immunized animals to mucosal SHIV challenge.

CONCLUSION

These passive immunization data give proof of IgG-mediated enhanced virus acquisition after mucosal exposure - a potential concern for antibody-based AIDS vaccine development.

Recombinant chimpanzee adenovirus AdC7 expressing dimeric tandem-repeat spike protein RBD protects mice against COVID-19

A safe and effective vaccine is urgently needed to control the unprecedented COVID-19 pandemic. Four adenovirus-vectored vaccines expressing spike (S) protein have been approved for use. Here, we generated several recombinant chimpanzee adenovirus (AdC7) vaccines expressing S, receptor-binding domain (RBD), or tandem-repeat dimeric RBD (RBD-tr2). We found vaccination via either intramuscular or intranasal route was highly immunogenic in mice to elicit both humoral and cellular immune responses. AdC7-RBD-tr2 showed higher antibody responses compared to either AdC7-S or AdC7-RBD. Intranasal administration of AdC7-RBD-tr2 additionally induced mucosal immunity with neutralizing activity in bronchoalveolar lavage fluid. Either single-dose or two-dose mucosal administration of AdC7-RBD-tr2 protected mice against SARS-CoV-2 challenge, with undetectable subgenomic RNA in lung and relieved lung injury. AdC7-RBD-tr2-elicted sera preserved the neutralizing activity against the circulating variants, especially the Delta variant. These results support AdC7-RBD-tr2 as a promising COVID-19 vaccine candidate.

An affinity-enhanced, broadly neutralizing heavy chain-only antibody protects against SARS-CoV-2 infection in animal models

Broadly neutralizing antibodies are an important treatment for individuals with coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Antibody-based therapeutics are also essential for pandemic preparedness against future Sarbecovirus outbreaks. Camelid-derived single domain antibodies (VHHs) exhibit potent antimicrobial activity and are being developed as SARS-CoV-2–neutralizing antibody-like therapeutics. Here, we identified VHHs that neutralize both SARS-CoV-1 and SARS-CoV-2, including now circulating variants. We observed that the VHHs bound to a highly conserved epitope in the receptor binding domain of the viral spike protein that is difficult to access for human antibodies. Structure-guided molecular modeling, combined with rapid yeast-based prototyping, resulted in an affinity enhanced VHH-human immunoglobulin G1 Fc fusion molecule with subnanomolar neutralizing activity. This VHH-Fc fusion protein, produced in and purified from cultured Chinese hamster ovary cells, controlled SARS-CoV-2 replication in prophylactic and therapeutic settings in mice expressing human angiotensin converting enzyme 2 and in hamsters infected with SARS-CoV-2. These data led to affinity-enhanced selection of the VHH, XVR011, a stable anti–COVID-19 biologic that is now being evaluated in the clinic.

Recent Development of Ruminant Vaccine Against Viral Diseases

Pathogens of viral origin produce a large variety of infectious diseases in livestock. It is essential to establish the best practices in animal care and an efficient way to stop and prevent infectious diseases that impact animal husbandry. So far, the greatest way to combat the disease is to adopt a vaccine policy. In the fight against infectious diseases, vaccines are very popular. Vaccination's fundamental concept is to utilize particular antigens, either endogenous or exogenous to induce immunity against the antigens or cells. In light of how past emerging and reemerging infectious diseases and pandemics were handled, examining the vaccination methods and technological platforms utilized for the animals may provide some useful insights. New vaccine manufacturing methods have evolved because of developments in technology and medicine and our broad knowledge of immunology, molecular biology, microbiology, and biochemistry, among other basic science disciplines. Genetic engineering, proteomics, and other advanced technologies have aided in implementing novel vaccine theories, resulting in the discovery of new ruminant vaccines and the improvement of existing ones. Subunit vaccines, recombinant vaccines, DNA vaccines, and vectored vaccines are increasingly gaining scientific and public attention as the next generation of vaccines and are being seen as viable replacements to conventional vaccines. The current review looks at the effects and implications of recent ruminant vaccine advances in terms of evolving microbiology, immunology, and molecular biology.

Cross-reactive antibodies after SARS-CoV-2 infection and vaccination

Current SARS-CoV-2 vaccines are losing efficacy against emerging variants and may not protect against future novel coronavirus outbreaks, emphasizing the need for more broadly protective vaccines. To inform the development of a pan-coronavirus vaccine, we investigated the presence and specificity of cross-reactive antibodies against the spike (S) proteins of human coronaviruses (hCoV) after SARS-CoV-2 infection and vaccination. We found an 11- to 123-fold increase in antibodies binding to SARS-CoV and MERS-CoV as well as a 2- to 4-fold difference in antibodies binding to seasonal hCoVs in COVID-19 convalescent sera compared to pre-pandemic healthy donors, with the S2 subdomain of the S protein being the main target for cross-reactivity. In addition, we detected cross-reactive antibodies to all hCoV S proteins after SARS-CoV-2 vaccination in macaques and humans, with higher responses for hCoV more closely related to SARS-CoV-2. These findings support the feasibility of and provide guidance for development of a pan-coronavirus vaccine.

Cross-reactive antibodies after SARS-CoV-2 infection and vaccination

Current SARS-CoV-2 vaccines are losing efficacy against emerging variants and may not protect against future novel coronavirus outbreaks, emphasizing the need for more broadly protective vaccines. To inform the development of a pan-coronavirus vaccine, we investigated the presence and specificity of cross-reactive antibodies against the spike (S) proteins of human coronaviruses (hCoV) after SARS-CoV-2 infection and vaccination. We found an 11- to 123-fold increase in antibodies binding to SARS-CoV and MERS-CoV as well as a 2- to 4-fold difference in antibodies binding to seasonal hCoVs in COVID-19 convalescent sera compared to pre-pandemic healthy donors, with the S2 subdomain of the S protein being the main target for cross-reactivity. In addition, we detected cross-reactive antibodies to all hCoV S proteins after SARS-CoV-2 vaccination in macaques and humans, with higher responses for hCoV more closely related to SARS-CoV-2. These findings support the feasibility of and provide guidance for development of a pan-coronavirus vaccine.

Overview of Neutralizing Antibodies and Their Potential in COVID-19

The antibody response to respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a major focus of COVID-19 research due to its clinical relevance and importance in vaccine and therapeutic development. Neutralizing antibody (NAb) evaluations are useful for the determination of individual or herd immunity against SARS-CoV-2, vaccine efficacy, and humoral protective response longevity, as well as supporting donor selection criteria for convalescent plasma therapy. In the current manuscript, we review the essential concepts of NAbs, examining their concept, mechanisms of action, production, and the techniques used for their detection; as well as presenting an overview of the clinical use of antibodies in COVID-19.

Large-Scale Dewetting via Surfactant-Laden Droplet Impact

The dewetting phenomenon of a liquid film in the presence of a surfactant exists in various natural, industrial, and biomedical processes but still remains mysterious in some specific scenarios. Here, we investigate the dewetting behavior of water films initiated by surfactant-laden droplet impact and show that the maximum dewetting diameter can even reach more than 50 times that of the droplet size. We identify the S-type variation of the dewetting area and demonstrate its correlation to the dynamic surface tension reduction. From a viewpoint of energy conversion, we attribute the dewetting to the released surface energy caused by the surfactant addition and establish a linear relation between the maximum dewetting and the surfactant concentration in the film, i.e., d_max² ∝ c_film, which agrees well with the experiments. These results may advance the physics of liquid film dewetting triggered by surfactant injection, which shall further guide practical applications.

Early Treatment for Covid-19 with SARS-CoV-2 Neutralizing Antibody Sotrovimab

BACKGROUND

Coronavirus disease 2019 (Covid-19) disproportionately results in hospitalization or death in older patients and those with underlying conditions. Sotrovimab is a pan-sarbecovirus monoclonal antibody that was designed to prevent progression of Covid-19 in high-risk patients early in the course of disease.

METHODS

In this ongoing, multicenter, double-blind, phase 3 trial, we randomly assigned, in a 1:1 ratio, nonhospitalized patients with symptomatic Covid-19 (≤5 days after the onset of symptoms) and at least one risk factor for disease progression to receive a single infusion of sotrovimab at a dose of 500 mg or placebo. The primary efficacy outcome was hospitalization (for >24 hours) for any cause or death within 29 days after randomization.

RESULTS

In this prespecified interim analysis, which included an intention-to-treat population of 583 patients (291 in the sotrovimab group and 292 in the placebo group), 3 patients (1%) in the sotrovimab group, as compared with 21 patients (7%) in the placebo group, had disease progression leading to hospitalization or death (relative risk reduction, 85%; 97.24% confidence interval, 44 to 96; P = 0.002). In the placebo group, 5 patients were admitted to the intensive care unit, including 1 who died by day 29. Safety was assessed in 868 patients (430 in the sotrovimab group and 438 in the placebo group). Adverse events were reported by 17% of the patients in the sotrovimab group and 19% of those in the placebo group; serious adverse events were less common with sotrovimab than with placebo (in 2% and 6% of the patients, respectively).

CONCLUSIONS

Among high-risk patients with mild-to-moderate Covid-19, sotrovimab reduced the risk of disease progression. No safety signals were identified. (Funded by Vir Biotechnology and GlaxoSmithKline; COMET-ICE ClinicalTrials.gov number, NCT04545060.).

Early Treatment for Covid-19 with SARS-CoV-2 Neutralizing Antibody Sotrovimab

BACKGROUND

Coronavirus disease 2019 (Covid-19) disproportionately results in hospitalization or death in older patients and those with underlying conditions. Sotrovimab is a pan-sarbecovirus monoclonal antibody that was designed to prevent progression of Covid-19 in high-risk patients early in the course of disease.

METHODS

In this ongoing, multicenter, double-blind, phase 3 trial, we randomly assigned, in a 1:1 ratio, nonhospitalized patients with symptomatic Covid-19 (≤5 days after the onset of symptoms) and at least one risk factor for disease progression to receive a single infusion of sotrovimab at a dose of 500 mg or placebo. The primary efficacy outcome was hospitalization (for >24 hours) for any cause or death within 29 days after randomization.

RESULTS

In this prespecified interim analysis, which included an intention-to-treat population of 583 patients (291 in the sotrovimab group and 292 in the placebo group), 3 patients (1%) in the sotrovimab group, as compared with 21 patients (7%) in the placebo group, had disease progression leading to hospitalization or death (relative risk reduction, 85%; 97.24% confidence interval, 44 to 96; P = 0.002). In the placebo group, 5 patients were admitted to the intensive care unit, including 1 who died by day 29. Safety was assessed in 868 patients (430 in the sotrovimab group and 438 in the placebo group). Adverse events were reported by 17% of the patients in the sotrovimab group and 19% of those in the placebo group; serious adverse events were less common with sotrovimab than with placebo (in 2% and 6% of the patients, respectively).

CONCLUSIONS

Among high-risk patients with mild-to-moderate Covid-19, sotrovimab reduced the risk of disease progression. No safety signals were identified. (Funded by Vir Biotechnology and GlaxoSmithKline; COMET-ICE ClinicalTrials.gov number, NCT04545060.).

Functionalized Nanoparticles in Prevention and Targeted Therapy of Viral Diseases With Neurotropism Properties, Special Insight on COVID-19

Neurotropic viruses have neural-invasive and neurovirulent properties to damage the central nervous system (CNS), leading to humans' fatal symptoms. Neurotropic viruses comprise a lot of viruses, such as Zika virus (ZIKV), herpes simplex virus (HSV), rabies virus (RABV), and severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). Effective therapy is needed to prevent infection by these viruses in vivo and in vitro. However, the blood-brain barrier (BBB) usually prevents macromolecules from entering the CNS, which challenges the usage of the traditional probes, antiviral drugs, or neutralizing antibodies in the CNS. Functionalized nanoparticles (NPs) have been increasingly reported in the targeted therapy of neurotropic viruses due to their sensitivity and targeting characteristics. Therefore, the present review outlines efficient functionalized NPs to further understand the recent trends, challenges, and prospects of these materials.

Mammalian animal models for dengue virus infection: a recent overview

Dengue, a rapidly spreading mosquito-borne human viral disease caused by dengue virus (DENV), is a public health concern in tropical and subtropical areas due to its expanding geographical range. DENV can cause a wide spectrum of illnesses in humans, ranging from asymptomatic infection or mild dengue fever (DF) to life-threatening dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Dengue is caused by four DENV serotypes; however, dengue pathogenesis is complex and poorly understood. Establishing a useful animal model that can exhibit dengue-fever-like signs similar to those in humans is essential to improve our understanding of the host response and pathogenesis of DENV. Although several animal models, including mouse models, non-human primate models, and a recently reported tree shrew model, have been investigated for DENV infection, animal models with clinical signs that are similar to those of DF in humans have not yet been established. Although animal models are essential for understanding the pathogenesis of DENV infection and for drug and vaccine development, each animal model has its own strengths and limitations. Therefore, in this review, we provide a recent overview of animal models for DENV infection and pathogenesis, focusing on studies of the antibody-dependent enhancement (ADE) effect in animal models.

Pathophysiology of COVID-19-associated acute kidney injury

Although respiratory failure and hypoxaemia are the main manifestations of COVID-19, kidney involvement is also common. Available evidence supports a number of potential pathophysiological pathways through which acute kidney injury (AKI) can develop in the context of SARS-CoV-2 infection. Histopathological findings have highlighted both similarities and differences between AKI in patients with COVID-19 and in those with AKI in non-COVID-related sepsis. Acute tubular injury is common, although it is often mild, despite markedly reduced kidney function. Systemic haemodynamic instability very likely contributes to tubular injury. Despite descriptions of COVID-19 as a cytokine storm syndrome, levels of circulating cytokines are often lower in patients with COVID-19 than in patients with acute respiratory distress syndrome with causes other than COVID-19. Tissue inflammation and local immune cell infiltration have been repeatedly observed and might have a critical role in kidney injury, as might endothelial injury and microvascular thrombi. Findings of high viral load in patients who have died with AKI suggest a contribution of viral invasion in the kidneys, although the issue of renal tropism remains controversial. An impaired type I interferon response has also been reported in patients with severe COVID-19. In light of these observations, the potential pathophysiological mechanisms of COVID-19-associated AKI may provide insights into therapeutic strategies.

To get vaccinated or not? Social psychological factors associated with vaccination intent for COVID-19

Pandemic control not only requires effective COVID-19 vaccines but also that they are accepted by at least 80% of the population. For this reason, understanding the social psychological variables associated with vaccination intent is essential to achieve herd immunity. Drawing on the theory of reasoned action, this study seeks to analyze vaccination intent using the beliefs about vaccine effectiveness, conspiracy theories, and injunctive norms as predictors. A non-probabilistic national online survey was conducted during December 2020. A sample of 1,033 people in Chile answered a questionnaire with the study variables. Using structural equation models, it was found that vaccination intent was explained in 62.1% by beliefs about vaccine effectiveness and injunctive norms, controlling for age, political orientation, socioeconomic status, educational level, and gender. Specifically, beliefs about vaccine effectiveness are based on people's experience with previous immunization processes, which predict vaccination intent. Regarding injunctive norms, they act by influencing and encouraging vaccination by seeking the approval of significant others. Contrary to expected, conspiracy beliefs were not directly associated with the intention to receive a COVID-19 vaccine but were highly related to lower beliefs about vaccine effectiveness. This study suggests that to enhance the vaccination intent, socio-psychological and structural variables need to be considered.

Boosting of Cross-Reactive Antibodies to Endemic Coronaviruses by SARS-CoV-2 Infection but not Vaccination with Stabilized Spike

Pre-existing antibodies to endemic coronaviruses (CoV) that cross-react with SARS-CoV-2 have the potential to influence the antibody response to COVID-19 vaccination and infection for better or worse. In this observational study of mucosal and systemic humoral immunity in acutely infected, convalescent, and vaccinated subjects, we tested for cross reactivity against endemic CoV spike (S) protein at subdomain resolution. Elevated responses, particularly to the β-CoV OC43, were observed in all natural infection cohorts tested and were correlated with the response to SARS-CoV-2. The kinetics of this response and isotypes involved suggest that infection boosts preexisting antibody lineages raised against prior endemic CoV exposure that cross react. While further research is needed to discern whether this recalled response is desirable or detrimental, the boosted antibodies principally targeted the better conserved S2 subdomain of the viral spike and were not associated with neutralization activity. In contrast, vaccination with a stabilized spike mRNA vaccine did not robustly boost cross-reactive antibodies, suggesting differing antigenicity and immunogenicity. In sum, this study provides evidence that antibodies targeting endemic CoV are robustly boosted in response to SARS-CoV-2 infection but not to vaccination with stabilized S, and that depending on conformation or other factors, the S2 subdomain of the spike protein triggers a rapidly recalled, IgG-dominated response that lacks neutralization activity.

Antibody-Dependent Enhancement of SARS-CoV-2 Infection Is Mediated by the IgG Receptors FcγRIIA and FcγRIIIA but Does Not Contribute to Aberrant Cytokine Production by Macrophages

The coronavirus disease 2019 (COVID-19) pandemic has raised concerns about the detrimental effects of antibodies. Antibody-dependent enhancement (ADE) of infection is one of the biggest concerns in terms of not only the antibody reaction to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) upon reinfection with the virus but also the reaction to COVID-19 vaccines. In this study, we evaluated ADE of infection by using COVID-19 convalescent-phase plasma and BHK cells expressing human Fcγ receptors (FcγRs). We found that FcγRIIA and FcγRIIIA mediated modest ADE of infection against SARS-CoV-2. Although ADE of infection was observed in monocyte-derived macrophages infected with SARS-CoV-2, including its variants, proinflammatory cytokine/chemokine expression was not upregulated in macrophages. SARS-CoV-2 infection thus produces antibodies that elicit ADE of infection, but these antibodies do not contribute to excess cytokine production by macrophages. IMPORTANCE Viruses infect cells mainly via specific receptors at the cell surface. Antibody-dependent enhancement (ADE) of infection is an alternative mechanism of infection for viruses to infect immune cells that is mediated by antibodies and IgG receptors (FcγRs). Because ADE of infection contributes to the pathogenesis of some viruses, such as dengue virus and feline coronavirus, it is important to evaluate the precise mechanism of ADE and its contribution to the pathogenesis of SARS-CoV-2. Here, using convalescent-phase plasma from COVID-19 patients, we found that two types of FcγRs, FcγRIIA and FcγRIIIA, mediate ADE of SARS-CoV-2 infection. Although ADE of infection was observed for SARS-CoV-2 and its recent variants, proinflammatory cytokine production in monocyte-derived macrophages was not upregulated. These observations suggest that SARS-CoV-2 infection produces antibodies that elicit ADE of infection, but these antibodies may not be involved in aberrant cytokine release by macrophages during SARS-CoV-2 infection.

COVID-19 cynomolgus macaque model reflecting human COVID-19 pathological conditions

The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global threat to human health and life. A useful pathological animal model accurately reflecting human pathology is needed to overcome the COVID-19 crisis. In the present study, COVID-19 cynomolgus monkey models including monkeys with underlying diseases causing severe pathogenicity such as metabolic disease and elderly monkeys were examined. Cynomolgus macaques with various clinical conditions were intranasally and/or intratracheally inoculated with SARS-CoV-2. Infection with SARS-CoV-2 was found in mucosal swab samples, and a higher level and longer period of viral RNA was detected in elderly monkeys than in young monkeys. Pneumonia was confirmed in all of the monkeys by computed tomography images. When monkeys were readministrated SARS-CoV-2 at 56 d or later after initial infection all of the animals showed inflammatory responses without virus detection in swab samples. Surprisingly, in elderly monkeys reinfection showed transient severe pneumonia with increased levels of various serum cytokines and chemokines compared with those in primary infection. The results of this study indicated that the COVID-19 cynomolgus monkey model reflects the pathophysiology of humans and would be useful for elucidating the pathophysiology and developing therapeutic agents and vaccines.

SARS-CoV-2 Reinfection Is a New Challenge for the Effectiveness of Global Vaccination Campaign: A Systematic Review of Cases Reported in Literature

Reinfection with SARS-CoV-2 seems to be a rare phenomenon. The objective of this study is to carry out a systematic search of literature on the SARS-CoV-2 reinfection in order to understand the success of the global vaccine campaigns. A systematic search was performed. Inclusion criteria included a positive RT-PCR test of more than 90 days after the initial test and the confirmed recovery or a positive RT-PCR test of more than 45 days after the initial test that is accompanied by compatible symptoms or epidemiological exposure, naturally after the confirmed recovery. Only 117 articles were included in the final review with 260 confirmed cases. The severity of the reinfection episode was more severe in 92/260 (35.3%) with death only in 14 cases. The observation that many reinfection cases were less severe than initial cases is interesting because it may suggest partial protection from disease. Another interesting line of data is the detection of different clades or lineages by genome sequencing between initial infection and reinfection in 52/260 cases (20%). The findings are useful and contribute towards the role of vaccination in response to the COVID-19 infections. Due to the reinfection cases with SARS-CoV-2, it is evident that the level of immunity is not 100% for all individuals. These data highlight how it is necessary to continue to observe all the prescriptions recently indicated in the literature in order to avoid new contagion for all people after healing from COVID-19 or becoming asymptomatic positive.

The Curious Case of Earthworms and COVID-19

Simple Summary

Earthworms have been used for centuries in traditional medicine, and more than a century ago were praised by Charles Darwin as one of the most important organisms in the history of the world. These worms are well-studied with a wealth of information available, for example on the genome, the gene expression, the immune system, the general biology, and ecology. These worms live in many habitats, and they had to find solutions for severe environmental challenges. The common compost worm, Eisenia fetida, has developed a unique mechanism to deal with intruding (nano)materials, bacteria, and viruses. It deals with the intruders by covering these with a defence toxin (lysenin) targeted to kill the intruder. We outline how this mechanism probably can be used as a therapeutic model for human COVID-19 (Severe Acute Respiratory Syndrome Coronavirus 2, SARS-CoV-2) and other corona viruses.

Abstract

Earthworms have been used for centuries in traditional medicine and are used globally as an ecotoxicological standard test species. Studies of the earthworm Eisenia fetida have shown that exposure to nanomaterials activates a primary corona-response, which is covering the nanomaterial with native proteins, the same response as to biological invaders such as a virus. We outline that the earthworm Eisenia fetida is possibly immune to COVID-19 (Severe Acute Respiratory Syndrome Coronavirus 2, SARS-CoV-2), and we describe the likely mechanisms of highly receptor-specific pore-forming proteins (PFPs). A non-toxic version of this protein is available, and we hypothesize that it is possible to use the earthworm’s PFPs based anti-viral mechanism as a therapeutic model for human SARS-CoV-2 and other corona viruses. The proteins can be used as a drug, for example, delivered with a nanoparticle in a similar way to the current COVID-19 vaccines. Obviously, careful consideration should be given to the potential risk of toxicity elicited by lysenin for in vivo usage. We aim to share this view to activate its exploration by the wider scientific community while promoting a potential therapeutic development.

Natural vaccines accumulated in facemasks during COVID-19: Underappreciated role of facial masking

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a causal agent behind coronavirus disease 2019 (COVID-19). Despite promising developments in therapeutic and preventive avenues, the importance of facial masking is a key factor for the protective measures among exposed human populations. Preclinical and clinical data on the importance of facial masking concerning asymptomatic over symptomatic COVID-19 cases is limited. The recent introduction of the concept of SARS-CoV-2 associated molecular particle patterns (SAMPPs) as a natural vaccine has opened new avenues for the comprehensive development of immunity. To take this further, the scope of natural vaccines accumulated in facemasks during facial masking needs to be highlighted that may directly or indirectly contribute to building adaptive immunity among human populations. This paper attempts to discuss the underappreciated contributions of facial masking in the management of COVID-19 at the global level.

SARS-CoV-2 monoclonal antibodies with therapeutic potential: Broad neutralizing activity and No evidence of antibody-dependent enhancement

Monoclonal antibodies (mAbs) are emerging as safe and effective therapeutics against SARS-CoV-2. However, variant strains of SARS-CoV-2 have evolved, with early studies showing that some mAbs may not sustain their efficacy in the face of escape mutants. Also, from the onset of the COVID-19 pandemic, concern has been raised about the potential for Fcγ receptor-mediated antibody-dependent enhancement (ADE) of infection. In this study, plaque reduction neutralization assays demonstrated that mAb 1741-LALA neutralizes SARS-CoV-2 strains B.1.351, D614 and D614G. MAbs S1D2-hIgG1 and S1D2-LALA mutant (STI-1499-LALA) did not neutralize B.1.351, but did neutralize SARS-CoV-2 strains D614 and D614G. LALA mutations did not result in substantial differences in neutralizing abilities between clones S1D2-hIgG1 vs STI-1499-LALA. S1D2-hIgG1, STI-1499-LALA, and convalescent plasma showed minimal ability to induce ADE in human blood monocyte-derived macrophages. Further, no differences in pharmacokinetic clearance of S1D2-hIgG1 vs STI-1499-LALA were observed in mice expressing human FcRn. These findings confirm that SARS-CoV-2 has already escaped some mAbs, and identify a mAb candidate that may neutralize multiple SARS-CoV-2 variants. They also suggest that risk of ADE in macrophages may be low with SARS-CoV-2 D614, and LALA Fc change impacts neither viral neutralization nor Ab clearance.

Pharmaceutical Aspects and Clinical Evaluation of COVID-19 Vaccines

COVID-19, the disease caused by the novel severe acute respiratory syndrome-associated coronavirus 2 (SARS-CoV-2), was first detected in December 2019 and has since morphed into a global pandemic claiming over 2.4 million human lives and severely impacting global economy. The race for a safe and efficacious vaccine was thus initiated with government agencies as well as major pharmaceutical companies as frontrunners. An ideal vaccine would activate multiple arms of the adaptive immune system to generate cytotoxic T cell responses as well as neutralizing antibody responses, while avoiding pathological or deleterious immune responses that result in tissue damage or exacerbation of the disease. Developing an effective vaccine requires an inter-disciplinary effort involving virology, protein biology, biotechnology, immunology and pharmaceutical sciences. In this review, we provide a brief overview of the pathology and immune responses to SARS-CoV-2, which are fundamental to vaccine development. We then summarize the rationale for developing COVID-19 vaccines and provide novel insights into vaccine development from a pharmaceutical science perspective, such as selection of different antigens, adjuvants, delivery platforms and formulations. Finally, we review multiple clinical trial outcomes of novel vaccines in terms of safety and efficacy.