This study characterized antibody-dependent enhancement (ADE) in serum samples from individuals exposed to SARS-CoV-2 via infection or vaccination and evaluated its association with SARS-CoV-2 variants (Wuhan and Omicron), MERS-CoV, and NL63. ADE assays were performed on sera from SARS-CoV-2-infected patients (n = 210) with varying disease severity and vaccinated individuals (n = 225) who received adenovirus vector, inactivated virus or mRNA vaccines. ADE was assessed using pseudoviruses (PVs) in BHK cells expressing FcgRIIa. Neutralizing antibody levels, total IgG, IgG subclasses, and complement activation were analyzed using ELISA and neutralization assays. ADE was observed in 6.2% of infection samples (primarily severe cases) and 5.3% of vaccinated samples (adenovirus-vector and inactivated virus groups). ADE-positive samples showed reduced neutralizing activity, while total IgG and IgG subclasses did not differ significantly between ADE-positive and negative samples. Complement activation was elevated in severe cases but did not correlate clearly with ADE. Notably, MERS-CoV PV induced ADE in a subset of infected samples, but no ADE was detected for NL63. ADE was observed in SARS-CoV-2-infected individuals, particularly in severe cases, and in those vaccinated with adenovirus-vector and inactivated virus vaccines, but not with mRNA vaccines. Cross-reactivity leading to ADE was detected for MERS-CoV but not for NL63. ADE was associated with reduced neutralizing antibody activity and elevated complement activation in severe infections, though the specific role of complement in ADE remains unclear. These findings highlight the need to investigate the mechanisms underlying ADE and its implications for vaccine design and post-infection immunity against respiratory viruses.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spread rapidly, leading to an Omicron outbreak in Shanghai in mid-December after adjustments to the Coronavirus Disease 2019 (COVID-19) control strategy. To investigate the impact of COVID-19 infection among hypothyroid patients, we gathered data on the hypothyroid outpatients with COVID-19 infection during this time at the Thyroid Disease Center (TDC) of Shanghai Central Hospital. Patients were divided into two groups based on whether their hypothyroidism was caused by Hashimoto's Thyroiditis (HT): the HT and the non-HT group. We assessed the differences between pre-infection and clinical follow-up at one month (day (D) 30) and three months (D90) after COVID-19 infection. In HT group, thyroid-stimulating hormone (TSH) levels decreased significantly compared to pre-infection levels (p = 0.013), while free triiodothyronine (FT3) levels increased at D90 compared to both D30 post-infection and pre-infection levels (p < 0.001 and p = 0.005). Hemoglobin levels also increased after COVID-19 infection (p = 0.033). For non-HT patients, FT3 levels increased at D30 compared to pre-infection levels (p = 0.017). Moreover, inactivated SARS-CoV-2 vaccination can preserve thyroid function stability in patients with hypothyroidism.

Orf virus (ORFV) has been demonstrated to infect both goat non-immune cells, specifically goat epithelial cells, and goat blood immune cells. Our previous studies have indicated that ORFV gains entry into goat epithelial cells via clathrin-mediated endocytosis and macropinocytosis pathways. However, the pathway by which ORFV enters goat blood immune cells has not yet been elucidated. Our findings revealed a differential viral internalization pathway in ORFV-infects goat immune cells contrasting the internalization pathways in goat epithelial cells, potentially involving an antibody-related mechanism. Therefore, our hypothesis posits that ORFV gains entry into goat immune cells via the antibody-dependent enhancement (ADE) pathway. Our experimental findings confirm the presence of the ADE effect in ORFV-infected goat immune cells, mediated by Fc receptors (FcRs) as demonstrated in antibody-blocking experiments. Furthermore, the ADE effect was also observed in goat epithelial cells. Nevertheless, the ADE effect observed in goat epithelial cells was not found to be dependent on the interaction between the virus-antibody complex and Fc receptors, as demonstrated by antibody-blocking experiments. Instead, it is suggested that an alternative mechanism involving the complement factor and complement receptors (CRs) may be responsible. Overall, this research offers insights into the unique ADE pathway of ORFV infection in different cell types, offering a novel perspective on the infection and pathogenic mechanisms of ORFV.

COVID-19 patients face an increased risk of thromboembolic complications, yet the exact pathophysiological role of platelets in the disease remains unclear. Considering the multifaceted nature of COVID-19 symptoms, including platelet hyperactivation and inflammation, the development of compounds that simultaneously target both represents a promising therapeutic strategy. The monoterpene 1.8-cineole (CNL-1976) is known for its anti-inflammatory and anti-aggregatory effects. Thus, understanding the mechanism behind platelet hyperactivation and the effect of 1.8-cineole during COVID-19 is crucial when aiming for a reduction of disease severity. In this study, we investigated the mechanism of platelet activation triggered by the SARS-CoV-2 S1 spike protein (S1). Utilizing S1-coupled beads, we discovered that platelet activation and aggregation were dependent on plasma components, particularly S1-specific IgG antibodies. The formation of immune complexes through IgG binding to S1 facilitated the crosslinking of the platelet expressed FcγRIIa receptor, initiating platelet activation and aggregation, as well as formation of platelet-leukocyte aggregates (PLAs). Importantly, treatment with 1.8-cineole significantly inhibited S1-bead-induced platelet activity and PLA formation. These findings strongly suggest that antibody-mediated platelet activation via FcγRIIa directly contributes to the well-recognized prothrombotic environment during COVID-19. Moreover, our data indicate that 1.8-cineole can serve as a potential therapeutic compound, alleviating platelet-driven thromboinflammatory complications associated with COVID-19 and post-acute sequelae of SARS-CoV-2 (PASC).

The coronavirus disease 2019 (COVID-19) global health crisis, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has presented unprecedented challenges to global healthcare systems, leading to rapid advances in treatment development. This review comprehensively examines the current therapeutic approaches for managing COVID-19, including direct-acting antivirals, immunomodulators, anticoagulants, and adjuvant therapies, as well as emerging and experimental approaches. Direct-acting antivirals target various stages of the viral life cycle, offering specific intervention points, while immunomodulators aim to modulate the host's immune response, reducing disease severity. Anticoagulant therapies address the coagulopathy frequently observed in severe cases, and adjuvant treatments provide supportive care to improve overall outcomes. We also explore the challenges and limitations of implementing these treatments, such as drug resistance, variable patient responses, and access to therapies, especially in resource-limited settings. The review also discusses future perspectives, including the potential of next-generation vaccines, personalized medicine, and global collaboration in shaping future COVID-19 treatment paradigms. Continuous innovation, combined with an integrated and adaptable approach, will be crucial to effectively managing COVID-19 and mitigating the impact of future pandemics.

Defining the kinetics of SARS-CoV-2 antibody responses is critical for informing the management of reinfections, vaccinations, and therapeutics of Coronavirus disease 2019 (COVID-19).

Using four antibody assays, we evaluated antibody titers against SARS-CoV-2 nucleocapsid (N), spike (S), and receptor binding domain (RBD) in 98 convalescent participants with varying COVID-19 disease severities (asymptomatic, mild, moderate or severe) at 1, 3, 6, and 12-months post-SARS-CoV-2-positive PCR and in 17 non-vaccinated, non-infected controls.

Increasing acute COVID-19 disease severity correlates with higher anti-N and anti-RBD titers throughout 12 months post-infection. Anti-N and anti-RBD titers decline over time in all participants, except for increased anti-RBD titers post-vaccination, with hospitalized participants exhibiting faster decay rates. Less than 50% of participants retain anti-N titers above controls at 12 months, with non-hospitalized participants falling below controls sooner. Nearly all participants maintain anti-RBD titers above controls for 12 months, suggesting long-term protection against severe reinfections. Nonetheless, by 6 months, few participants retain >50% of their initial 1-month anti-N or anti-RBD titers. Notably, vaccine-induced anti-RBD titers are higher in non-hospitalized participants. Lastly, early convalescent titers correlate with age but not with Post-Acute Sequelae of SARS-CoV-2 infection (PASC) status or steroid use.

Hospitalized participants initially develop higher anti-SARS-CoV-2 antibody titers that decline faster relative to non-hospitalized participants. While anti-N titers fall below control levels in some participants, anti-RBD titers remain above controls over 12 months, demonstrating long-lived antibody responses known to protect against severe disease. These findings advance our understanding of COVID-19 antibody dynamics.

The antibody-dependent enhancement (ADE) of viral entry has been documented for SARS-CoV-2 infection both in vitro and in vivo. However, the potential for the SARS-CoV-2 vaccination to elicit similar ADE effects remains unclear.

In this study, we assessed the in vitro ADE potential of monoclonal antibodies (mAbs) derived from individuals vaccinated with the inactivated SARS-CoV-2 vaccine and compared them to those from one convalescent donor.

Our analysis revealed no significant difference in binding affinity or neutralizing capacity between the vaccinated and convalescent mAbs. However, the inactivated SARS-CoV-2 vaccination induced fewer ADE-inducing mAbs, particularly those targeting the Class III epitope on the receptor-binding domain (RBD) compared to those from the convalescent individual. Moreover, no significant in vitro ADE was detected in either vaccinated or convalescent sera, indicating low levels of ADE-inducing antibodies in the sera.

An inactivated SARS-CoV-2 vaccination induces fewer ADE-inducing antibodies compared to natural infection, further emphasizing the safety of inactivated SARS-CoV-2 vaccines.

Vaccination has been instrumental in curbing the transmission of SARS-CoV-2 and mitigating the severity of clinical manifestations associated with COVID-19. Numerous COVID-19 vaccines have been developed to this effect, including BioNTech-Pfizer and Moderna's mRNA vaccines, as well as adenovirus vector-based vaccines such as Oxford-AstraZeneca. However, the emergence of new variants and subvariants of SARS-CoV-2, characterized by enhanced transmissibility and immune evasion, poses significant challenges to the efficacy of current vaccination strategies. In this review, we aim to comprehensively outline the landscape of emerging SARS-CoV-2 variants of concern (VOCs) and sub-lineages that have recently surfaced in the post-pandemic years. We assess the effectiveness of existing vaccines, including their booster doses, against these emerging variants and subvariants, such as BA.2-derived sub-lineages, XBB sub-lineages, and BA.2.86 (Pirola). Furthermore, we discuss the latest advancements in vaccine technology, including multivalent and pan-coronavirus approaches, along with the development of several next-generation coronavirus vaccines, such as exosome-based, virus-like particle (VLP), mucosal, and nanomaterial-based vaccines. Finally, we highlight the key challenges and critical areas for future research to address the evolving threat of SARS-CoV-2 subvariants and to develop strategies for combating the emergence of new viral threats, thereby improving preparedness for future pandemics.

The antibody-mediated immune response is crucial for the development of protective immunity against SARS-CoV-2, the virus responsible for the COVID-19 pandemic. Understanding the interaction between SARS-CoV-2 and the immune system is critical because new variants emerge as a result of the virus's ongoing evolution. Understanding the function of B cells in the SARS-CoV-2 infection process is critical for developing effective and long-lasting vaccines against this virus. Triggered by the innate immune response, B cells transform into memory B cells (MBCs). It is fascinating to observe how MBCs provide enduring immune defence, not only eradicating the infection but also safeguarding against future reinfection. If there is a lack of B cell activation or if the B cells are not functioning properly, it can lead to a serious manifestation of the disease and make immunisation less effective. Individuals with disruptions in the B cells have shown increased production of cytokines and chemokines, resulting in a poor prognosis for the disease. Therefore, we have developed an updated review article to gain insight into the involvement of B cells in SARS-CoV-2 infection. The discussion has covered the generation, functioning, and dynamics of neutralising antibodies (nAbs). Furthermore, we have emphasised immunotherapeutics that rely on nAbs.

Background: Hospitalized patients with severe COVID-19 are at high risk of clinical deterioration. Methods: A global, randomized, double-blinded, and placebo-controlled phase II trial that investigated the clinical efficacy of SCTA01, an Fc-modified monoclonal antibody, in patients hospitalized with severe COVID-19 during the Delta variant wave was performed. The primary outcome was time to clinical improvement up to Day 29. Secondary outcomes measured the all-cause mortality rate up to Day 29, time to SARS-CoV-2 RNA negativity up to Day 29, and the number of antibody-dependent enhancements. Results: From 27 March 2021, to 11 February 2022, 102 hospitalized adults with severe COVID-19 received a single intravenous infusion of SCTA01 15 mg/kg or 50 mg/kg or placebo in a 1:1:1 ratio. The median time to clinical improvement in the SCTA01 group was numerically shorter than that in the placebo group; however, the between group difference was statistically non-significant (SCTA01 15 mg/kg vs. placebo, HR 0.99, 95% CI 0.55-1.77, p = 0.742; SCTA01 50 mg/kg vs. placebo, HR 1.07, 95% CI 0.61-1.88, p = 0.095). The median time to achieve a negative SARS-CoV-2 status was shorter in the SCTA01 15 mg/kg group (14.0 days vs. 27.0 days) but not in the SCTA01 50 mg/kg group (28.0 days vs. 27.0 days) compared to the placebo group. Adverse events were comparable across all groups, and no treatment-related serious adverse event or antibody-dependent enhancement was reported. Conclusions: The Fc-modified antibody was safe but lacked significant clinical efficacy in vivo, likely due to the SARS-CoV-2 viral mutation.

Sarbecoviruses, such as SARS-CoV-2, utilize angiotensin-converting enzyme 2 (ACE2) as the entry receptor; while merbecoviruses, such as MERS-CoV, use dipeptidyl peptidase 4 (DPP4) for viral entry. Recently, several MERS-related coronaviruses, NeoCoV and PDF-2180, were reported to use ACE2, the same receptor as SARS-CoV-2, to enter cells, raising the possibility of potential recombination between SARS-CoV-2 and MERS-related coronaviruses within the co-infected ACE2-expressing cells. However, facing this potential recombination risk, the serum and antibody cross-reactivity against MERS/MERS-related coronaviruses after SARS-CoV-2 vaccination and/or infection is still elusive. Here, in this study, we showed that the serological cross-reactivity against MERS/MERS-related S proteins could be induced by SARS-CoV-2 infection but not by inactivated SARS-CoV-2 vaccination. Further investigation revealed that this serum cross-reactivity is due to monoclonals recognizing relatively conserved S2 epitopes, such as fusion peptide and stem helix, but not by antibodies against the receptor-binding domain (RBD), N-terminal domain (NTD) or subdomain-1 (SD1). Some of these anti-S2 cross-reactive mAbs showed cross-neutralizing activity, while none of them exhibited antibody-dependent enhancement (ADE) effect of viral entry in vitro. Together, these results dissected the SARS-CoV-2 infection-induced serological cross-reactivity against MERS/MERS-related coronaviruses, and highlighted the significance of conserved S2 region for the design and development of pan-β-coronaviruses vaccines.

SpikoGen® is a subunit recombinant Wuhan spike protein produced in insect cells and formulated with Advax-CpG55.2™ adjuvant. It is approved for adult and pediatric use in the Middle East. This study tested the safety and immunogenicity of SpikoGen® as a 3rd, 4th or 5th dose booster following a primary immunisation course of mRNA, adenovirus or SpikoGen® vaccine.

The trial recruited participants who had received a previous doses of COVID-19 vaccine more than 3 months prior. Each received a single intramuscular booster dose of SpikoGen® vaccine. Spike and nuclear protein antibody levels were measured at 1 and 3 months post-booster, together with collection of data on SARS-CoV-2 breakthrough infections and symptoms of long COVID.

One-month post-booster, anti-spike IgG, sVNT, and pVNT levels were increased in all groups and there was ∼4-fold neutralizing antibodies against the heterologous Omicron BA.2 and BA.4/5 strains. The SpikoGen®-prime group had the highest levels of anti-spike IgG3, consistent with the Advax-CpG adjuvant driving IgG3 induction. There was no effect of age on the vaccine response. The booster dose was well tolerated with no vaccine-associated serious adverse events. Nine participants (9/74, 12.2 %) had a breakthrough SARS-CoV-2 infection between 2 weeks and 3 months post-booster. No long COVID was observed after breakthrough infections. Breakthrough infection was negatively correlated with baseline anti-nuclear protein IgG seropositivity.

A single SpikoGen® booster was well tolerated and stimulated cross- antibody responses against Omicron variants, regardless of the primary vaccine course received. With SARS-CoV-2 variants continuing to evolve, ongoing research is needed into optimum booster strategies.

gov registration. NCT05542862.

Virus-induced antibodies represent a dual-edged sword in the immune response to viral infections. While antibodies are critical for neutralizing pathogens, some can paradoxically exacerbate disease severity through mechanisms such as antibody-dependent enhancement (ADE), autoantibody, and prolonged inflammation. Long coronavirus disease (COVID) and dengue hemorrhagic fever (DHF) exemplify conditions where pathogenic antibodies play a pivotal role in disease progression. Long COVID is associated with persistent immune dysregulation and autoantibody production, leading to chronic symptoms and tissue damage. In DHF, pre-existing antibodies against dengue virus contribute to ADE, amplifying viral replication, immune activation, and vascular permeability. This review explores the mechanisms underlying these pathogenic antibody responses, highlighting the shared pathways of immune dysregulation and comparing the distinct features of both conditions. By examining these studies, we identify key lessons for therapeutic strategies, vaccine design, and future research aimed at mitigating the severe outcomes of viral infections.

ACE2 (angiotensin-converting enzyme 2) is a monocarboxypeptidase that cleaves Ang II (angiotensin II) among other substrates. ACE2 is present in the cell membrane of many organs, most abundantly in epithelial cells of kidney proximal tubules and the small intestine, and also exists in soluble forms in plasma and body fluids. Membrane-bound ACE2 exerts a renoprotective action by metabolizing Ang II and therefore attenuating the undesirable actions of excess Ang II. Therefore, soluble ACE2, by downregulating this peptide, may exert a therapeutic action. Our laboratory has designed ACE2 truncates that pass the glomerular filtration barrier to target the kidney renin-angiotensin system directly and, therefore, compensate for loss of kidney membrane-bound ACE2. Membrane-bound ACE2 is also the essential receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Soluble ACE2 proteins have been studied as a way to intercept SARS-CoV-2 from binding to membrane-bound ACE2 and prevent cell entry of SARS-CoV-2 altogether. We bioengineered a soluble ACE2 protein, termed ACE2 618-DDC-ABD, with increased binding affinity for SARS-CoV-2 and prolonged duration of action, which, when administered intranasally, provides near-complete protection from lethality in k18hACE2 mice infected with different SARS-CoV-2 variants. The main advantage of soluble ACE2 proteins for the neutralization of SARS-CoV-2 is their immediate onset of action and universality for current and future emerging SARS-CoV-2 variants. It is notable that ACE2 is critically involved in 2 dissimilar functions: as a receptor for cell entry of many coronaviruses and as an enzyme in the metabolism of Ang II, and yet in both cases, it is a therapeutic target.

Background: Although mRNA vaccines encapsulated in lipid nanoparticles (LNPs) have demonstrated a safety profile with minimal serious adverse events in clinical trials, there is opportunity to further reduce mRNA reactogenicity. The development of naked mRNA vaccines could improve vaccine tolerability. Naked nucleic acid delivery using the jet injection method may be a solution. Methods: In the first part of the study, the optimal conditions providing low traumatization and high expression of the model mRNA-GFP molecule in the tissues of laboratory animals were determined. Then, we used the selected protocol to immunize BALB/c mice with mRNA-RBD encoding the SARS-CoV-2 receptor-binding domain (RBD). It was demonstrated that mice vaccinated with naked mRNA-RBD developed a high level of specific antibodies with virus-neutralizing activity. The vaccine also induced a strong RBD-specific T-cell response and reduced the viral load in the lungs of the animals after infection with the SARS-CoV-2 virus. The level of immune response in mice immunized with mRNA-RBD using a spring-loaded jet injector was comparable to that in animals immunized with mRNA-RBD encapsulated in LNPs. Results: In this study, the efficacy of an inexpensive, simple, and safe method of mRNA delivery using a spring-loaded jet injector was evaluated and validated. Conclusions: Our findings suggest that the jet injection method may be a possible alternative to LNPs for delivering mRNA vaccines against SARS-CoV-2 infection.

Recent avian influenza outbreaks have heightened global concern over viral threats with the potential to significantly impact human health. Influenza is particularly alarming due to its history of causing pandemics and zoonotic reservoirs. In response, significant progress has been made toward the development of universal influenza vaccines, largely driven by the discovery of broadly neutralising antibodies (bnAbs), which have the potential to neutralise a broad range of influenza viruses, extending beyond the traditional strain-specific response. This could lead to longer-lasting immunity, reducing the need for seasonal vaccinations, and improve preparedness for future pandemics. This review offers a comprehensive analysis of these antibodies, their application in clinical studies, and both their potential and possible shortcomings in managing future influenza outbreaks.

Factors leading to severe COVID-19 remain partially known. New biomarkers predicting COVID-19 severity that are also causally involved in disease pathogenesis could improve patient management and contribute to the development of innovative therapies. Autophagy, a cytosolic structure degradation pathway is involved in the maintenance of cellular homeostasis, degradation of intracellular pathogens and generation of energy for immune responses. Acyl-CoA binding protein (ACBP) is a key regulator of autophagy in the context of diabetes, obesity and anorexia. The objective of our work was to assess whether circulating ACBP levels are associated with COVID-19 severity, using proteomics data from the plasma of 903 COVID-19 patients.

Somalogic proteomic analysis was used to detect 5000 proteins in plasma samples collected between March 2020 and August 2021 from hospitalized participants in the province of Quebec, Canada. Plasma samples from 903 COVID-19 patients collected during their admission during acute phase of COVID-19 and 295 hospitalized controls were assessed leading to 1198 interpretable proteomic profiles. Levels of anti-SARS-CoV-2 IgG were measured by ELISA and a cell-binding assay.

The median age of the participants was 59 years, 46% were female, 65% had comorbidities. Plasma ACBP levels correlated with COVID-19 severity, in association with inflammation and anti-SARS-CoV-2 antibody levels, independently of sex or the presence of comorbidities. Samples collected during the second COVID-19 wave in Quebec had higher levels of plasma ACBP than during the first wave. Plasma ACBP levels were negatively correlated with biomarkers of T and NK cell responses interferon-γ, tumor necrosis factor-α and interleukin-21, independently of age, sex, and severity.

Circulating ACBP levels can be considered a biomarker of COVID-19 severity linked to inflammation. The contribution of extracellular ACBP to immunometabolic responses during viral infection should be further studied.

Antibody-dependent enhancement (ADE) of infectious disease is a phenomenon whereby host antibodies increase the severity of an infection. It is well established in viral infections but ADE also has an underappreciated role during bacterial, fungal and parasitic infections. ADE can occur during both primary infections and re-infections with the same or a related pathogen; therefore, understanding the underlying mechanisms of ADE is critical for understanding the pathogenesis and progression of many infectious diseases. Here, we review the four distinct mechanisms by which antibodies increase disease severity during an infection. We discuss the most established mechanistic explanation for ADE, where cross-reactive, disease-enhancing antibodies bound to pathogens interact with Fc receptors, thereby enhancing pathogen entry or replication, ultimately increasing the total pathogen load. Additionally, we explore how some pathogenic antibodies can shield bacteria from complement-dependent killing, thereby enhancing bacterial survival. We interrogate the molecular mechanisms by which antibodies can amplify inflammation to drive severe disease, even in the absence of increased pathogen replication. We also examine emerging roles for autoantibodies in enhancing the pathogenesis of infectious diseases. Finally, we discuss how we can leverage these insights to improve vaccine design and future treatments for infectious diseases.

The relationship between inborn errors of immunity (IEIs) and COVID-19 severity and incidence rates remains unclear due to limited and diverse data. This study aimed to address this gap by identifying specific IEIs associated with an increased risk of severe COVID-19 or a predisposition to severe disease before vaccination.

Data were collected from the medical records of 15 patients with various IEIs, supplemented by interviews with individuals from an IEIs registry who had experienced COVID-19 before vaccination.

Among the participants, only three patients (20%) experienced severe-prolonged COVID-19. Notably, this severity was predominantly observed in two male patients with Bruton's disease (BD) and one female patient with autosomal recessive hypogammaglobinemia. Moderate and severe COVID-19 cases were equally distributed (13.33%). In the female subgroup, one patient with common variable immunodeficiency and another with combined immunodeficiency experienced moderate and severe COVID-19, respectively. Conversely, both male patients with moderate and severe COVID-19 had BD.

Despite the limited number of severe cases, the absence of cytokine storm manifestation suggests potential protective mechanisms, possibly due to intravenous immunoglobulin therapy and inherent deficiencies within cytokine-producing cells (B and T cells). While IEIs may not be significant risk factors for COVID-19, they offer promising avenues for further research into therapeutic strategies targeting specific immune system components to mitigate severe COVID-19.

Severe acute respiratory coronavirus-2 (SARS-CoV-2) emerged in 2019 as a new virus and caused worldwide outbreaks, quickly turning into a pandemic disease called coronavirus disease-19 (COVID-19). All the existing methodologies were used for developing vaccines for this virus. But sporadic infections of this virus and the emergence of new strains to date suggest the incomplete protection offered by the developed vaccines and the need for new research. In this direction, we identified five epitopes present in the non-RBD region and on the surface of the spike protein by in silico analysis. They are epitope I (aa 80-90), epitope II (aa 262-270), and a small protein with three epitopes (aa 1059-1124). Antigenicity scores of these epitopes were found to be higher than the full length spike protein and its RBD region. These epitopes showed high conserveness across the emerging strains, high immunogenicity, non-toxicity, no homology with human sequences and high affinity for MHC class I & II molecules. Antibodies raised against these epitopes interacted with the bacterially expressed spike protein in western blotting. The antiserum of COVID-19 recovered participants reacted with the developed epitopes (small protein). Furthermore, in the presence of the respective antiserum and COVID-19 convalescent serum, these epitopes successfully fixed the complement, implying a possible role in innate immunity. The epitopes were also found to activate the peripheral blood mononuclear cells (PBMCs) isolated from the blood samples of COVID-19 recovered/vaccinated participants, suggesting a possible role in adaptive immunity. The need for the new SARS-CoV-2 vaccines is further highlighted in light of current reports about the side effects of a developed vaccine (AstraZeneca) and the circulating new strains. The epitopes presented in this study represent the potential immunogens and expect certain pitfalls of the existing vaccines would be sealed.

Grasping the roles of epitopes in viral glycoproteins is essential for unraveling the structure and function of these proteins. Up to now, all identified epitopes have been found to either neutralize, have no effect on, or enhance viral entry into cells. Here, we used nanobodies (single-domain antibodies) as probes to investigate a unique epitope on the SARS-CoV-2 spike protein, located outside the protein's receptor-binding domain. Nanobody binding to this epitope enhances the cell entry of prototypic SARS-CoV-2, while neutralizing the cell entry of SARS-CoV-2 Omicron variant. Moreover, nanobody binding to this epitope promotes both receptor binding activity and post-attachment activity of prototypic spike, explaining the enhanced viral entry. The opposite occurs with Omicron spike, explaining the neutralized viral entry. This study reveals a unique epitope that can both enhance and neutralize viral entry across distinct viral variants, suggesting that epitopes may vary their roles depending on the viral context. Consequently, antibody therapies should be assessed across different viral variants to confirm their efficacy and safety.

The COVID-19 outbreak has highlighted the importance of pandemic preparedness for the prevention of future health crises. One virus family with high pandemic potential are Arenaviruses, which have been detected almost worldwide, particularly in Africa and the Americas. These viruses are highly understudied and many questions regarding their structure, replication and tropism remain unanswered, making the design of an efficacious and molecularly-defined vaccine challenging. We propose that structure-driven computational vaccine design will contribute to overcome these challenges. Computational methods for stabilization of viral glycoproteins or epitope focusing have made progress during the last decades and particularly during the COVID-19 pandemic, and have proven useful for rational vaccine design and the establishment of novel diagnostic tools. In this review, we summarize gaps in our understanding of Arenavirus molecular biology, highlight challenges in vaccine design and discuss how structure-driven and computationally informed strategies will aid in overcoming these obstacles.

Since the emergence of the coronavirus disease 2019 (COVID-19). Several autoimmune and subacute thyroiditis (SAT) cases are on the rise all over the world. COVID-19 vaccine-associated SAT cases have also been reported. In this article, we present our data on 5 vaccine-associated SAT cases. We evaluated the type of vaccine received, the time between vaccination and the onset of SAT symptoms, laboratory findings, treatments administered, and response to treatment. The age of patients ranged from 31 to 43 years old. Three (60 %) patients had been diagnosed as SAT after the first dose, and tow (40 %) after the second dose. Patients' symptoms appeared approximately 25.2 days (2-44) after vaccination. Subacute thyroiditis occurring after COVID-19 vaccination is rare, we hope practitioners should be early aware of post-vaccine SAT, that can improve clinical evolution and outcome.

Major efforts were deployed to study the antibody response against SARS-CoV-2. Antibodies neutralizing SARS-CoV-2 have been extensively studied in the context of infections, vaccinations, and breakthrough infections. Antibodies, however, are pleiotropic proteins that have many functions in addition to neutralization. These include Fc-effector functions such as antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). Although important to combat viral infections, these Fc-effector functions were less studied in the context of SARS-CoV-2 compared with binding and neutralization. This is partly due to the difficulty in developing reliable assays to measure Fc-effector functions compared to antibody binding and neutralization. Multiple assays have now been developed and can be used to measure different Fc-effector functions. Here, we review these assays and what is known regarding anti-SARS-CoV-2 Fc-effector functions. Overall, this review summarizes and updates our current state of knowledge regarding anti-SARS-CoV-2 Fc-effector functions.

As an antibody-based therapy, plasma therapy has been used as an emergency therapeutic strategy against severe acute respiratory syndrome coronavirus type 2 infection. Due to the critical role of macrophages in coronavirus disease-19 (COVID-19)-associated hyperinflammation, the main objective of this study was to assess the effect of plasma transfusion on the expression levels of the inflammatory biomarkers involved in activation and pulmonary infiltration of macrophages. The target population included 50 severe hospitalized COVID-19 patients who were randomly assigned into 2 groups, including intervention and control. Serum levels of chemokine (C-C motif) ligand (CCL)-2, CCL-3, tumor necrosis factor (TNF)-α, and interleukin (IL)-6 were measured by enzyme-linked immunosorbent assay. Moreover, quantitative real-time polymerase chain reaction (PCR) was carried out to assess the relative expression of nuclear factor (NF)-κB1, NF-κB2, nuclear factor erythroid 2 p45-related factor 2 (NRF-2), and thioredoxin-interacting protein genes. Sampling was done at baseline and 72 h after receiving plasma. The intervention group demonstrated significantly lower serum levels of IL-6, TNF-α, and CCL-3. In addition, real-time PCR data analyses showed that the relative expression of NF-κB2 was significantly declined in the patients who received plasma. The use of convalescent plasma probably has a significant inhibitory effect on the cytokines, chemokines, and inflammatory genes related to macrophage activation, which are closely associated with the worsening of clinical outcomes in severe COVID-19.

The evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in variants that can escape neutralization by therapeutic antibodies. Here, we describe AZD3152, a SARS-CoV-2-neutralizing monoclonal antibody designed to provide improved potency and coverage against emerging variants. AZD3152 binds to the back left shoulder of the SARS-CoV-2 spike protein receptor binding domain and prevents interaction with the human angiotensin-converting enzyme 2 receptor. AZD3152 potently neutralized a broad panel of pseudovirus variants, including the currently dominant Omicron variant JN.1 but has reduced potency against XBB subvariants containing F456L. In vitro studies confirmed F456L resistance and additionally identified T415I and K458E as escape mutations. In a Syrian hamster challenge model, prophylactic administration of AZD3152 protected hamsters from weight loss and inflammation-related lung pathologies and reduced lung viral load. In the phase 1 sentinel safety cohort of the ongoing SUPERNOVA study (ClinicalTrials.gov: NCT05648110), a single 600-mg intramuscular injection of AZD5156 (containing 300 mg each of AZD3152 and cilgavimab) was well tolerated in adults through day 91. Observed serum concentrations of AZD3152 through day 91 were similar to those observed with cilgavimab and consistent with predictions for AZD7442, a SARS-CoV-2-neutralizing antibody combination of cilgavimab and tixagevimab, in a population pharmacokinetic model. On the basis of its pharmacokinetic characteristics, AZD3152 is predicted to provide durable protection against symptomatic coronavirus disease 2019 caused by susceptible SARS-CoV-2 variants, such as JN.1, in humans.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in December 2019 with staggering economic fallout and human suffering. The unique structure of SARS-CoV-2 and its underlying pathogenic mechanism were responsible for the global pandemic. In addition to the direct damage caused by the virus, SARS-CoV-2 triggers an abnormal immune response leading to a cytokine storm, culminating in acute respiratory distress syndrome and other fatal diseases that pose a significant challenge to clinicians. Therefore, potential treatments should focus not only on eliminating the virus but also on alleviating or controlling acute immune/inflammatory responses. Current management strategies for COVID-19 include preventative measures and supportive care, while the role of the host immune/inflammatory response in disease progression has largely been overlooked. Understanding the interaction between SARS-CoV-2 and its receptors, as well as the underlying pathogenesis, has proven to be helpful for disease prevention, early recognition of disease progression, vaccine development, and interventions aimed at reducing immunopathology have been shown to reduce adverse clinical outcomes and improve prognosis. Moreover, several key mutations in the SARS-CoV-2 genome sequence result in an enhanced binding affinity to the host cell receptor, or produce immune escape, leading to either increased virus transmissibility or virulence of variants that carry these mutations. This review characterizes the structural features of SARS-CoV-2, its variants, and their interaction with the immune system, emphasizing the role of dysfunctional immune responses and cytokine storm in disease progression. Additionally, potential therapeutic options are reviewed, providing critical insights into disease management, exploring effective approaches to deal with the public health crises caused by SARS-CoV-2.

Antibodies perform both neutralizing and non-neutralizing effector functions that protect against certain pathogen-induced diseases. A human antibody directed at the SARS-CoV-2 Spike N-terminal domain (NTD), DH1052, was recently shown to be non-neutralizing, yet it protected mice and cynomolgus macaques from severe disease. The mechanisms of NTD non-neutralizing antibody-mediated protection are unknown. Here we show that Fc effector functions mediate NTD non-neutralizing antibody (non-nAb) protection against SARS-CoV-2 MA10 viral challenge in mice. Though non-nAb prophylactic infusion did not suppress infectious viral titers in the lung as potently as neutralizing antibody (nAb) infusion, disease markers including gross lung discoloration were similar in nAb and non-nAb groups. Fc functional knockout substitutions abolished non-nAb protection and increased viral titers in the nAb group. Fc enhancement increased non-nAb protection relative to WT, supporting a positive association between Fc functionality and degree of protection from SARS-CoV-2 infection. For therapeutic administration of antibodies, non-nAb effector functions contributed to virus suppression and lessening of lung discoloration, but the presence of neutralization was required for optimal protection from disease. This study demonstrates that non-nAbs can utilize Fc-mediated mechanisms to lower viral load and prevent lung damage due to coronavirus infection.

The novel coronavirus disease 2019 (COVID-19) pandemic outbreak caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has garnered unprecedented global attention. It caused over 2.47 million deaths through various syndromes such as acute respiratory distress, hypercoagulability, and multiple organ failure. The viral invasion proceeds through the ACE2 receptor, expressed in multiple cell types, and in some patients caused serious damage to tissues, organs, immune cells, and the microbes that colonize the gastrointestinal tract (GIT). Some patients who survived the SARS-CoV-2 infection have developed months of persistent long-COVID-19 symptoms or post-acute sequelae of COVID-19 (PASC). Diagnosis of these patients has revealed multiple biological effects, none of which are mutually exclusive. However, the severity of COVID-19 also depends on numerous comorbidities such as obesity, age, diabetes, and hypertension and care must be taken with respect to other multiple morbidities, such as host immunity. Gut microbiota in relation to SARS-CoV-2 immunopathology is considered to evolve COVID-19 progression via mechanisms of biochemical metabolism, exacerbation of inflammation, intestinal mucosal secretion, cytokine storm, and immunity regulation. Therefore, modulation of gut microbiome equilibrium through food supplements and probiotics remains a hot topic of current research and debate. In this review, we discuss the biological complications of the physio-pathological effects of COVID-19 infection, GIT immune response, and therapeutic pharmacological strategies. We also summarize the therapeutic targets of probiotics, their limitations, and the efficacy of preclinical and clinical drugs to effectively inhibit the spread of SARS-CoV-2.

Monoclonal antibodies (mAb) targeting the SARS-CoV-2 Spike (S) glycoprotein have been exploited for the treatment of severe COVID-19. In this study, we evaluated the immune-regulatory features of two neutralizing anti-S mAbs (nAbs), named J08 and F05, with wild-type (WT) conformation or silenced Fc functions. In the presence of D614G SARS-CoV-2, WT nAbs enhance intracellular viral uptake in immune cells and amplify antiviral type I Interferon and inflammatory cytokine and chemokine production without viral replication, promoting the differentiation of CD16+ inflammatory monocytes and innate/adaptive PD-L1+ and PD-L1+CD80+ plasmacytoid Dendritic Cells. In spite of a reduced neutralizing property, WT J08 nAb still promotes the IL-6 production and differentiation of CD16+ monocytes once binding Omicron BA.1 variant. Fc-mediated regulation of antiviral and inflammatory responses, in the absence of viral replication, highlighted in this study, might positively tune immune response during SARS-CoV-2 infection and be exploited also in mAb-based therapeutic and prophylactic strategies against viral infections.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has caused more than 676 million cases in the global human population with approximately 7 million deaths and vaccination has been proved as the most effective countermeasure in reducing clinical complications and mortality rate of SARS-CoV-2 infection in people. However, the protective elements and correlation of protection induced by vaccination are still not completely understood. Various antibodies with multiple protective mechanisms can be induced simultaneously by vaccination in vivo, thereby complicating the identification and characterization of individual correlate of protection. Recently, an increasing body of observations suggests that antibody-induced Fc-effector functions play a crucial role in combating SARS-CoV-2 infections, including neutralizing antibodies-escaping variants. Here, we review the recent progress in understanding the impact of Fc-effector functions in broadly disarming SARS-CoV-2 infectivity and discuss various efforts in harnessing this conserved antibody function to develop an effective SARS-CoV-2 vaccine that can protect humans against infections by SARS-CoV-2 virus and its variants of concern.

Understanding the antibody response to SARS-CoV-2, the virus responsible for COVID-19, is crucial to comprehending disease progression and the significance of vaccine and therapeutic development. The emergence of highly contagious variants poses a significant challenge to humoral immunity, underscoring the necessity of grasping the intricacies of specific antibodies. This review emphasizes the pivotal role of antibodies in shaping immune responses and their implications for diagnosing, preventing, and treating SARS-CoV-2 infection. It delves into the kinetics and characteristics of the antibody response to SARS-CoV-2 and explores current antibody-based diagnostics, discussing their strengths, clinical utility, and limitations. Furthermore, we underscore the therapeutic potential of SARS-CoV-2-specific antibodies, discussing various antibody-based therapies such as monoclonal antibodies, polyclonal antibodies, anti-cytokines, convalescent plasma, and hyperimmunoglobulin-based therapies. Moreover, we offer insights into antibody responses to SARS-CoV-2 vaccines, emphasizing the significance of neutralizing antibodies in order to confer immunity to SARS-CoV-2, along with emerging variants of concern (VOCs) and circulating Omicron subvariants. We also highlight challenges in the field, such as the risks of antibody-dependent enhancement (ADE) for SARS-CoV-2 antibodies, and shed light on the challenges associated with the original antigenic sin (OAS) effect and long COVID. Overall, this review intends to provide valuable insights, which are crucial to advancing sensitive diagnostic tools, identifying efficient antibody-based therapeutics, and developing effective vaccines to combat the evolving threat of SARS-CoV-2 variants on a global scale.

Most available neutralizing antibodies are ineffective against highly mutated SARS-CoV-2 Omicron subvariants. Therefore, it is crucial to develop potent and broad-spectrum alternatives to effectively manage Omicron subvariants. Here, we constructed a high-diversity nanobody phage display library and identified nine nanobodies specific to the SARS-CoV-2 receptor-binding domain (RBD). Five of them exhibited cross-neutralization activity against the SARS-CoV-2 wild-type (WT) strain and the Omicron subvariants BA.1 and BA.4/5, and one nanobody demonstrated marked efficacy even against the Omicron subvariants BQ.1.1 and XBB.1. To enhance the therapeutic potential, we engineered a panel of multivalent nanobodies with increased neutralizing potency and breadth. The most potent multivalent nanobody, B13-B13-B13, cross-neutralized all tested pseudoviruses, with a geometric mean of the 50% inhibitory concentration (GM IC50) value of 20.83 ng/mL. An analysis of the mechanism underlying the enhancement of neutralization breadth by representative multivalent nanobodies demonstrated that the strategic engineering approach of combining two or three nanobodies into a multivalent molecule could improve the affinity between a single nanobody and spike, and could enhance tolerance toward escape mutations such as R346T and N460K. Our engineered multivalent nanobodies may be promising drug candidates for treating and preventing infection with Omicron subvariants and even future variants.