Site-directed neutralizing antibodies targeting structural sites on SARS-CoV-2 spike protein

'Epivolve' (epitope evolution) is an innovative paratope-evolving technology using a haptenated peptide or protein immunogen as a means of directing the in vivo immune response to specifically targeted sites at a one amino acid residue resolution. Guided by protein structural analysis, Epivolve technology was tested to develop site-directed neutralizing antibodies (nAbs) in a systematic fashion against the SARS-CoV-2 Receptor Binding Domain (RBD). Thirteen solvent-exposed sites covering the ACE2 receptor-binding interface were targeted. Immunogens composed of each targeted site were used to immunize rabbits in separate cohorts. In vivo site-directed immune responses against all 13 targets were demonstrated by B cell secreted IgG and recombinant IgG testing. One site, SL13 (Y505) which mutates from tyrosine to histidine in the SARS-CoV-2 Omicron variant, was chosen as a proof-of-concept (PoC) model for further functional monoclonal antibody development. Epivolve technology demonstrated the capabilities of generating pan-variant antibodies and nAbs against the SARS-CoV-2 primary strain and the Omicron variant.

Early-stage neutralizing antibody level associated with the re-positive risk of Omicron SARS-CoV-2 RNA in patients recovered from COVID-19

Post-discharge re-positivity of Omicron SARS-CoV-2 is challenging for the sufficient control of this pandemic. However, there are few studies about the risk of re-positivity. We aimed to explore the association of neutralizing antibodies (nAbs, AU/mL) with the incidence of re-positivity among patients recovered from COVID-19. A retrospective cohort study selected 318 Omicron-infected patients was conducted in China between December 2021 and April 2022. The peak value of nAb levels (nAb-peak) within 14 days of disease onset was defined as the baseline and was mainly used for the subsequent analyses. In the unadjusted, minimally adjusted, fully adjusted, and additionally adjusted for IgG models, a per-standard deviation (SD) increase in the nAb-peak values was significantly associated with a 59 %, 59 %, 50 %, and 75 % decreased risk of Omicron SARS-CoV-2 re-positivity during post-discharge surveillance, respectively. Stratified analyses showed no significant changes in the relationship between nAbs and re-positivity. Our study suggested that the increase in baseline nAb levels independently associated with a low risk of re-positivity in patients recovered from COVID-19.

Efficacy of Genotype-matched Vaccine Against Re-emerging Genotype V Japanese Encephalitis Virus

Japanese encephalitis (JE), caused by the Japanese encephalitis virus (JEV), is a highly threatening disease with no specific treatment. Fortunately, the development of vaccines has enabled effective defense against JE. However, re-emerging genotype V (GV) JEV poses a challenge as current vaccines are genotype III (GIII)-based and provide suboptimal protection. Given the isolation of GV JEVs from Malaysia, China, and the Republic of Korea, there is a concern about the potential for a broader outbreak. Under the hypothesis that a GV-based vaccine is necessary for effective defense against GV JEV, we developed a pentameric recombinant antigen using cholera toxin B as a scaffold and mucosal adjuvant, which was conjugated with the E protein domain III of GV by genetic fusion. This GV-based vaccine antigen induced a more effective immune response in mice against GV JEV isolates compared to GIII-based antigen and efficiently protected animals from lethal challenges. Furthermore, a bivalent vaccine approach, inoculating simultaneously with GIII- and GV-based antigens, showed protective efficacy against both GIII and GV JEVs. This strategy presents a promising avenue for comprehensive protection in regions facing the threat of diverse JEV genotypes, including both prevalent GIII and GI as well as emerging GV strains.

Highly drug/target-tolerant neutralizing antibody (NAb) assay development through target-based drug depletion and drug-based NAb extraction for an anti-EGFR therapeutic monoclonal antibody

The reduction of immunogenicity is fundamental for the development of biobetter Erbitux, given that the development of an immune response reduces treatment efficacy and may lead to potential side effects. One of the requirements for the clinical research of a Erbitux biobetter candidate (CMAB009) is to develop a neutralizing antibody (NAb) assay, and sufficient drug and target tolerance for the assay is necessary. Here, we describe the development of a competitive ligand binding (CLB) assay for CMAB009 with high drug and target tolerance through target-based drug depletion and drug-based NAb extraction, the integrated experimental strategy was implemented to simultaneously mitigate drug interference and enhance target tolerance. Following troubleshooting and optimization, the NAb assay was validated for clinical sample analysis with the sensitivity of 92 ng/mL, drug tolerance of 70 μg/mL and target tolerance of 798 ng/mL. The innovative drug depletion and NAb extraction achieved though the combination of drug and target beads would enable the development of reliable NAb assays for many other therapeutics that overcome drug and its target interference for more precise and sensitive NAb assessment.

Assessment of the neutralizing antibody response in Omicron breakthrough cases in healthcare workers who received the homologous booster of Moderna mRNA-1273

Vaccines against SARS-CoV-2 were developed during the pandemic including the BNT162b2 and the mRNA-1273. We evaluated the levels of binding antibodies against the receptor binding domain and the levels of NAbs in individuals who developed a breakthrough infection after having received three doses of mRNA-1273. A total of 51 participants were included. The breakthrough group was compared to a 1:1 matched-control group. Among the 51 individuals, 18 (35%) developed a breakthrough infection. The GMT of NAbs against the BA.1 in the BK population was 278.1 (95%CI: 168.1-324.1). This titer was significantly lower compared to the matched-control group when considering all data (GMT = 477.4; 95%CI: 316.2-541.0; p = 0.0057). Results were similar for the BA.5 (GMT = 152.0 (95%CI: 76.9-172.9) for breakthrough and 262.0 (95%CI: 171.3-301.8) for control (p = 0.0043)). Our study found that individuals receiving the mRNA-1273 booster and who developed a breakthrough infection presented lower levels of binding antibodies and NAbs before the infection as compared to a matched-control group.

Feasibility of using a combination of staphylococcal superantigen-like proteins 3, 7 and 11 in a fusion vaccine for Staphylococcus aureus

Staphylococcus aureus is a significant bacterial pathogen in both community and hospital settings, and the escalation of antimicrobial-resistant strains is of immense global concern. Vaccination is an inviting long-term strategy to curb staphylococcal disease, but identification of an effective vaccine has proved to be challenging. Three well-characterized, ubiquitous, secreted immune evasion factors from the staphylococcal superantigen-like (SSL) protein family were selected for the development of a vaccine. Wild-type SSL3, 7 and 11, which inhibit signaling through Toll-like receptor 2, cleavage of complement component 5 and neutrophil function, respectively, were successfully combined into a stable, active fusion protein (PolySSL7311). Vaccination of mice with an attenuated form of the PolySSL7311 protein stimulated significantly elevated specific immunoglobulin G and splenocyte proliferation responses to each component relative to adjuvant-only controls. Vaccination with PolySSL7311, but not a mixture of the individual proteins, led to a > 102 reduction in S. aureus tissue burden compared with controls after peritoneal challenge. Comparable antibody responses were elicited after coadministration of the vaccine in either AddaVax (an analog of MF59) or an Alum-based adjuvant; but only AddaVax conferred a significant reduction in bacterial load, aligning with other studies that suggest both cellular and humoral immune responses are necessary for protective immunity to S. aureus. Anti-sera from mice immunized with PolySSL7311, but not individual proteins, partially neutralized the functional activities of SSL7. This study confirms the importance of these SSLs for the survival of S. aureus in vivo and suggests that PolySSL7311 is a promising vaccine candidate.

Neutralization of SARS-CoV-2 Omicron subvariant BA.2.87.1

A new highly mutated Omicron subvariant BA.2.87.1 has recently been identified with over 30 amino acid mutations in the Spike protein compared with BA.2, BA.5, XBB.1.5, and JN.1 variants. Mutiple mutations in BA.2.87.1 are located in the N-terminal domain (NTD) rather than in the receptor binding domain (RBD) of the Spike protein. We evaluated neutralizing antibody (NAb) responses to BA.2.87.1 because of its highly mutated sequence and its unique NTD region. Our data show that NAb responses to BA.2.87.1 were lower than to BA.2 but higher than to JN.1, suggesting that BA.2.87.1 is not a further antibody escape variant compared with other currently circulating variants. Moreover, XBB.1.5 mRNA boosting increased NAb titers to all variants tested including BA.2.87.1.

A method for screening CDV microneutralization activity in microvolume samples

OBJECTIVE

This study aims to establish a screening method for canine distemper virus (CDV) microneutralizing activity suitable for microvolume samples.

METHODS

This method is based on the Indirect immunofluorescence assay (IFA) established on Vero-slam cells. First, by comparing the sensitivities of CDV neutralizing monoclonal antibody (1C42H11) and NP protein monoclonal antibody (CDV-NP) in IFA experiments, CDV-NP was selected as the primary antibody. Then, by detecting the infection rates of multi-concentrations of CDV neutralized with water, the minimum CDV concentration with an infection rate greater than 90% was defined as the minimum stable infection concentration, which was used as the neutralizing solution for this method. Finally, the CDV-positive neutralizing serum (neutralizing titer 1:708) was diluted into multiple dilution groups as test samples, and then neutralized in equal volumes with the neutralizing solution to detect the neutralizing activity detection rates of each dilution group and the lowest detection limit of this method.

RESULTS

The results showed that the neutralizing activity of serum with a CDV neutralizing titer of 1:708 diluted 212 times was the lowest limit of detection, and the detection rate of microneutralizing activity was 63.54 ± 4.774%.

CONCLUSION

This study established an economical, stable, and easy-to-operate CDV microneutralizing activity high-throughput screening method, laying a methodological foundation for the development of native CDV neutralizing antibodies based on single B cells.

Neutralizing antibodies to block viral entry and for identification of entry inhibitors

Neutralizing antibodies (NAbs) are naturally produced by our immune system to combat viral infections. Clinically, neutralizing antibodies with potent efficacy and high specificity have been extensively used to prevent and treat a wide variety of viral infections, including Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), Human Immunodeficiency Virus (HIV), Dengue Virus (DENV) and Hepatitis B Virus (HBV). An overwhelmingly large subset of clinically effective NAbs operates by targeting viral envelope proteins to inhibit viral entry into the host cell. Binding of viral envelope protein to the host receptor is a critical rate limiting step triggering a cascade of downstream events, including endocytosis, membrane fusion and pore formation to allow viral entry. In recent years, improved structural knowledge on these processes have allowed researchers to also leverage NAbs as an indispensable tool in guiding discovery of novel antiviral entry inhibitors, providing drug candidates with high efficacy and pan-genus specificity. This review will summarize the latest progresses on the applications of NAbs as effective entry inhibitors and as important tools to develop antiviral therapeutics by high-throughput drug screenings, rational design of peptidic entry inhibitor mimicking NAbs and in silico computational modeling approaches.

Beta-variant recombinant booster vaccine elicits broad cross-reactive neutralization of SARS-CoV-2 including Omicron variants

Background

SARS-CoV-2 Omicron lineage contains variants with multiple sequence mutations relative to the ancestral strain particularly in the viral spike gene. These mutations are associated inter alia with loss of neutralization sensitivity to sera generated by immunization with vaccines targeting ancestral strains or prior infection with circulating (non-Omicron) variants. Here we present a comparison of vaccine formulation elicited cross neutralization responses using two different assay readouts from a subpopulation of a Phase II/III clinical trial.

Methods

Human sera from a Phase II/III trial (NCT04762680) was collected and evaluated for neutralizing responses to SARS-CoV-2 spike antigen protein vaccines formulated with AS03 adjuvant, following a primary series of two-doses of ancestral strain vaccine in individuals who were previously unvaccinated or as an ancestral or variant strain booster vaccine among individuals previously vaccinated with the mRNA BNT162b2 vaccine.

Results

We report that a neutralizing response to Omicron BA.1 is induced by the two-dose primary series in 89% of SARS-CoV-2-seronegative individuals. A booster dose of each vaccine formulation raises neutralizing antibody titers that effectively neutralizes Omicron BA.1 and BA.4/5 variants. Responses are highest after the monovalent Beta variant booster and similar in magnitude to human convalescent plasma titers.

Conclusion

The findings of this study suggest the possibility to generate greater breadth of cross-neutralization to more recently emerging viral variants through use of a diverged spike vaccine in the form of a Beta variant booster vaccine.

Distinct Patterns of SARS-CoV-2 BA.2.87.1 and JN.1 Variants in Immune Evasion, Antigenicity and Cell-Cell Fusion

The rapid evolution of SARS-CoV-2 variants presents a constant challenge to the global vaccination effort. In this study, we conducted a comprehensive investigation into two newly emerged variants, BA.2.87.1 and JN.1, focusing on their neutralization resistance, infectivity, antigenicity, cell-cell fusion, and spike processing. Neutralizing antibody (nAb) titers were assessed in diverse cohorts, including individuals who received a bivalent mRNA vaccine booster, patients infected during the BA.2.86/JN.1-wave, and hamsters vaccinated with XBB.1.5-monovalent vaccine. We found that BA.2.87.1 shows much less nAb escape from WT-BA.4/5 bivalent mRNA vaccination and JN.1-wave breakthrough infection sera compared to JN.1 and XBB.1.5. Interestingly. BA.2.87.1 is more resistant to neutralization by XBB.15-monovalent-vaccinated hamster sera than BA.2.86/JN.1 and XBB.1.5, but efficiently neutralized by a class III monoclonal antibody S309, which largely fails to neutralize BA.2.86/JN.1. Importantly, BA.2.87.1 exhibits higher levels of infectivity, cell-cell fusion activity, and furin cleavage efficiency than BA.2.86/JN.1. Antigenically, we found that BA.2.87.1 is closer to the ancestral BA.2 compared to other recently emerged Omicron subvariants including BA.2.86/JN.1 and XBB.1.5. Altogether, these results highlight immune escape properties as well as biology of new variants and underscore the importance of continuous surveillance and informed decision-making in the development of effective vaccines.

Microfluidic Diffusional Sizing (MDS) Measurements of Secretory Neutralizing Antibody Affinity Against SARS-CoV-2

SARS-CoV-2 has rampantly spread around the globe and continues to cause unprecedented loss through ongoing waves of (re)infection. Increasing our understanding of the protection against infection with SARS-CoV-2 is critical to ending the pandemic. Serological assays have been widely used to assess immune responses, but secretory antibodies, the essential first line of defense, have been studied to only a limited extent. Of particular interest and importance are neutralizing antibodies, which block the binding of the spike protein of SARS-CoV-2 to the human receptor angiotensin-converting enzyme-2 (ACE2) and thus are essential for immune defense. Here, we employed Microfluidic Diffusional Sizing (MDS), an immobilization-free technology, to characterize neutralizing antibody affinity to SARS-CoV-2 spike receptor-binding domain (RBD) and spike trimer in saliva. Affinity measurement was obtained through a contrived sample and buffer using recombinant SARS-CoV-2 RBD and monoclonal antibody. Limited saliva samples demonstrated that MDS applies to saliva neutralizing antibody measurement. The ability to disrupt a complex of ACE2-Fc and spike trimer is shown. Using a quantitative assay on the patient sample, we determined the affinity and binding site concentration of the neutralizing antibodies.

The CDE region of feline Calicivirus VP1 protein is a potential candidate subunit vaccine

BACKGROUND

Feline calicivirus (FCV) infection causes severe upper respiratory disease in cats, but there are no effective vaccines available for preventing FCV infection. Subunit vaccines have the advantages of safety, low cost and excellent immunogenicity, but no FCV subunit vaccine is currently available. The CDE protein is the dominant neutralizing epitope region of the main antigenic structural protein of FCV, VP1. Therefore, this study evaluated the effectiveness of the CDE region as a truncated FCV VP1 protein in preventing FCV infection to provide a strategy for developing potential FCV subunit vaccines.

RESULTS

Through the prediction of FCV VP1 epitopes, we found that the E region is the dominant neutralizing epitope region. By analysing the spatial structure of VP1 protein, 13 amino acid sites in the CD and E regions were found to form hydrogen bonding interactions. The results show the presence of these interaction forces supports the E region, helping improve the stability and expression level of the soluble E protein. Therefore, we selected the CDE protein as the immunogen for the immunization of felines. After immunization with the CDE protein, we found significant stimulation of IgG, IgA and neutralizing antibody production in serum and swab samples, and the cytokine TNF-α levels and the numbers of CD4+ T lymphocytes were increased. Moreover, a viral challenge trial indicated that the protection generated by the CDE subunit vaccine significantly reduced the incidence of disease in animals.

CONCLUSIONS

For the first time, we studied the efficacy of the CDE protein, which is the dominant neutralizing epitope region of the FCV VP1 protein, in preventing FCV infection. We revealed that the CDE protein can significantly activate humoral, mucosal and cellular immunity, and the resulting protective effect can significantly reduce the incidence of animal disease. The CDE region of the FCV capsid is easy to produce and has high stability and excellent immunogenicity, which makes it a candidate for low-cost vaccines.

Inactivated whole virion vaccine protects K18-hACE2 Tg mice against the Omicron SARS-CoV-2 variant via cross-reactive T cells and nonneutralizing antibody responses

COVID-19 is a systemic inflammatory disease initiated by SARS-CoV-2 virus infection. Multiple vaccines against the Wuhan variant of SARS-CoV-2 have been developed including a whole virion beta-propiolactone-inactivated vaccine based on the B.1.1 strain (CoviVac). Since most of the population has been vaccinated by targeting the original or early variants of SARS-CoV-2, the emergence of novel mutant variants raises concern over possible evasion of vaccine-induced immune responses. Here, we report on the mechanism of protection by CoviVac, a whole virion-based vaccine, against the Omicron variant. CoviVac-immunized K18-hACE2 Tg mice were protected against both prototype B.1.1 and BA.1-like (Omicron) variants. Subsequently, vaccinated K18-hACE2 Tg mice rapidly cleared the infection via cross-reactive T-cell responses and cross-reactive, non-neutralizing antibodies recognizing the Omicron variant Spike protein. Thus, our data indicate that efficient protection from SARS-CoV-2 variants can be achieved by the orchestrated action of cross-reactive T cells and non-neutralizing antibodies.

A tetravalent bispecific antibody outperforms the combination of its parental antibodies and neutralizes diverse SARS-CoV-2 variants

The devastating impact of COVID-19 on global health shows the need to increase our pandemic preparedness. Recombinant therapeutic antibodies were successfully used to treat and protect at-risk patients from COVID-19. However, the currently circulating Omicron subvariants of SARS-CoV-2 are largely resistant to therapeutic antibodies, and novel approaches to generate broadly neutralizing antibodies are urgently needed. Here, we describe a tetravalent bispecific antibody, A7A9 TVB, which actively neutralized many SARS-CoV-2 variants of concern, including early Omicron subvariants. Interestingly, A7A9 TVB neutralized more variants at lower concentration as compared to the combination of its parental monoclonal antibodies, A7K and A9L. A7A9 also reduced the viral load of authentic Omicron BA.1 virus in infected pseudostratified primary human nasal epithelial cells. Overall, A7A9 displayed the characteristics of a potent broadly neutralizing antibody, which may be suitable for prophylactic and therapeutic applications in the clinics, thus highlighting the usefulness of an effective antibody-designing approach.

SDF-1 involvement in orthodontic tooth movement after tooth extraction

The stromal cell-derived factor 1 (SDF-1)/chemokine receptor type 4 (CXCR4) axis plays a key role in alveolar bone metabolism during orthodontic tooth movement (OTM). Herein, the effects of the SDF-1/CXCR4 axis on the regional acceleratory phenomenon (RAP) in OTM velocity and on changes in the surrounding periodontium after adjacent tooth extraction in rats were investigated. Six-week-old male Wistar/ST rats underwent left maxillary first molar (M1) extraction and mesial OTM of the left maxillary second molar (M2) with a 10-g force closed-coil spring. Phosphate-buffered saline, immunoglobulin G (IgG) isotype control antibody, or anti-SDF-1 neutralizing monoclonal antibody were injected at the M1 and M2 interproximal areas (10 μg/0.1 mL) for the first three days. Analyses were performed after 1, 3, and 7 days (n = 7). The results demonstrated a significant increase in SDF-1 expression from day 1, which was effectively blocked via anti-SDF-1 neutralizing monoclonal antibody injection. On day 3, the M2 OTM distance and the number of positively stained osteoclasts significantly reduced alongside a reduction in inflammatory markers in the experimental group. Our results demonstrated that serial local injection of the anti-SDF-1 neutralizing monoclonal antibody reduces M2 OTM, osteoclast accumulation, and localized inflammatory responses in an OTM model with tooth extraction-induced RAP.

Detection methods and dynamic characteristics of specific antibodies in patients with COVID-19: A review of the early literature

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused a global pandemic. Early and accurate diagnosis and quarantine remain the most effective mitigation strategy. Although reverse transcriptase polymerase chain reaction (RT-qPCR) is the gold standard for COVID-19 diagnosis, recent studies suggest that nucleic acids were undetectable in a significant number of cases with clinical features of COVID-19.Serological assays for SARS-CoV-2 play a role in diagnosis of COVID-19, in understanding viral epidemiology and screening convalescent sera for therapeutic and prophylactic purposes, to better understand the immune response to the virus, and to assess the degree and duration of the response of specific antibodies. In this article, we retrieved PubMed, Embase, China National Knowledge Infrastructure (CNKI) and WEB OF SCI databases for articles and reviews published before December 1, 2022. Using "IgM, IgG,IgA, neutralizing antibody, specific antibody,COVID-19, dynamic characteristics" as keywords, and comprehensively reviewed on their basis.According to the authors' criteria, only articles deemed relevant were included, covering original articles, case series, experimental studies, reviews, and case reports. Articles on performance evaluation, opinion pieces, and technical issues were excluded. From the onset of COVID-19 symptoms, the median time of seroconversion was 11 days for immunoglobulin A (IgA), the median time of peak antibody titer was 23 (16-30 days) for IgA.Immunoglobulin M (IgM) is detected prior to immunoglobulin G (IgG), peaking 2-5 weeks post symptom onset and detectable for a minimum of 8 weeks in the immunocompetent.Neutralizing antibodies were earliest detectable within 6-7 days following disease onset, with levels increasing until days 14-22 before levelling and then decreasing, but titres were lower in clinically mild disease. Different clinical types of patients showed different antibody responses to SARS-CoV-2, with severe COVID-19 patients > non-severe COVID-19 patients > asymptomatic infected persons, but no difference in the early stage of the disease. Usually, IgM and IgA antibodies are detectable earlier than IgG antibodies.IgA antibodys plays an important role in local mucosal immunity.Detection of IgM antibodies tends to indicate recent exposure to SARS-CoV-2, whereas the detection of COVID-19 IgG antibodies indicates virus exposure some time ago. The detection of potent neutralizing antibodies in convalescent plasma is important in the context of development of therapeutics and vaccines.With the emergence of immune escape variants of SARS-CoV-2, humoral immunity is being challenged, and a detailed understanding of Specific antibodies is critical to guide vaccine design strategies and antibody-mediated therapies.

Novel neutralizing SARS-CoV-2-specific mAbs offer detection of RBD linear epitopes

BACKGROUND

To stop the spread of the COVID-19 disease, it is crucial to create molecular tools to investigate and diagnose COVID-19. Current efforts focus on developing specific neutralizing monoclonal antibodies (NmAbs) elicited against the receptor-binding domain (RBD).

METHODS

In the present study, recombinant RBD (rRBD) protein was produced in E. coli, followed by immunizing mice with purified rRBD. ELISA was applied to screen the hybridomas for positive reactivity with rRBD protein. The linear and conformational epitopes of the mAbs were subsequently identified using western blot. Finally, the reactivity, affinity, and neutralization activity of the purified mAbs were evaluated using ELISA.

RESULTS

All mAbs exhibited similar reactivity trends towards both eukaryotic RBD and prokaryotic rRBD in ELISA. Among them, 2E7-D2 and 2B4-G8 mAbs demonstrated higher reactivity than other mAbs. Additionally, in western blot assays, these two mAbs could detect reducing and non-reducing rRBD, indicating recognition of linear epitopes. Notably, five mAbs effectively blocked rRBD- angiotensin-converting enzyme 2 (ACE2) interaction, while two high-affinity mAbs exhibited potent neutralizing activity against eukaryotic RBD.

CONCLUSION

In the current study, we generated and characterized new RBD-specific mAbs using the hybridoma technique that recognized linear and conformational epitopes in RBD with neutralization potency. Our mAbs are novel candidates for diagnosing and treating SARS-CoV-2.

Integrating artificial intelligence-based epitope prediction in a SARS-CoV-2 antibody discovery pipeline: caution is warranted

BACKGROUND

SARS-CoV-2-neutralizing antibodies (nABs) showed great promise in the early phases of the COVID-19 pandemic. The emergence of resistant strains, however, quickly rendered the majority of clinically approved nABs ineffective. This underscored the imperative to develop nAB cocktails targeting non-overlapping epitopes.

METHODS

Undertaking a nAB discovery program, we employed a classical workflow, while integrating artificial intelligence (AI)-based prediction to select non-competing nABs very early in the pipeline. We identified and in vivo validated (in female Syrian hamsters) two highly potent nABs.

FINDINGS

Despite the promising results, in depth cryo-EM structural analysis demonstrated that the AI-based prediction employed with the intention to ensure non-overlapping epitopes was inaccurate. The two nABs in fact bound to the same receptor-binding epitope in a remarkably similar manner.

INTERPRETATION

Our findings indicate that, even in the Alphafold era, AI-based predictions of paratope-epitope interactions are rough and experimental validation of epitopes remains an essential cornerstone of a successful nAB lead selection.

FUNDING

Full list of funders is provided at the end of the manuscript.

High diagnostic accuracy of quantitative SARS-CoV-2 spike-binding-IgG assay and correlation with in vitro viral neutralizing activity

Background

Antibody testing can easily evaluate the clinical status of patients, aid in the diagnosis of multisystem inflammatory syndrome, and monitor the immunity level in the population. However, the applicability of serological tests in detecting antibodies against the severe acute respiratory syndrome 2 (SARS-CoV-2) spike-binding protein remains limited. This study aimed to quantify both serum-derived neutralizing immunoglobulin-G (IgG) antibody activity and the amount of anti-SARS-CoV-2 Spike-IgG (S-IgG) in convalescent sera/plasmas and evaluate the direct correlation between the in vitro IgG-EC50 values and S-IgG values.

Methods

We evaluated the neutralizing activity of purified IgG (IgG-EC50), quantified S-IgG in the serum/plasma of consecutive COVID-19 convalescent individuals using a cell-based virus-neutralizing assay, and determined the correlation between IgG-EC50 and S-IgG. In addition, we evaluated rational cut-off values using the receiver operating characteristic (ROC) curve and calculated the sensitivity and specificity of the quantitative S-IgG assay for moderate and high IgG-EC50.

Results

A high correlation was observed between S-IgG and IgG-EC50 with a Spearman's ρ value of -0.748 (95 % confidence interval [CI]: -0.804-0.678). Using an IgG-EC50 of 50 μg/mL and 20 μg/mL as the cut-off values for moderate and high in vitro neutralizing activity, respectively, the Youden's index values of 287.5 binding antibody units (BAU)/mL and 454.1 BAU/mL determined from the ROC curve showed the highest diagnostic accuracy, with Kappa values of 0.884 (95 % CI: 0.823-0.946) and 0.920 (95 % CI: 0.681-0.979), respectively.

Conclusions

Quantitative S-IgG tests are a useful and convenient tool for estimating in vitro virus-neutralizing activity, with a high correlation with IgG-EC50 when the rational cut-off value is carefully determined.

Immunogenicity and durability against Omicron BA.1, BA.2 and BA.4/5 variants at 3-4 months after a heterologous COVID-19 booster vaccine in healthy adults with a two-doses CoronaVac vaccination

Background

Several countries have authorized a booster vaccine campaign to combat the spread of COVID-19. Data on persistence of booster vaccine-induced immunity against new Omicron subvariants are still limited. Therefore, our study aimed to determine the serological immune response of COVID-19 booster after CoronaVac-priming.

Methods

A total of 187 CoronaVac-primed participants were enrolled and received an inactivated (BBIBP), viral vector (AZD1222) or mRNA vaccine (full-/half-dose BNT162B2, full-/half-dose mRNA-1273) as a booster dose. The persistence of humoral immunity both binding and neutralizing antibodies against wild-type and Omicron was determined on day 90-120 after booster.

Results

A waning of total RBD immunoglobulin (Ig) levels, anti-RBD IgG, and neutralizing antibodies against Omicron BA.1, BA.2, and BA.4/5 variants was observed 90-120 days after booster vaccination. Participants who received mRNA-1273 had the highest persistence of the immunogenicity response, followed by BNT162b2, AZD1222, and BBIBP-CorV. The responses between full and half doses of mRNA-1273 were comparable. The percentage reduction of binding antibody ranged from 50 % to 75 % among all booster vaccine.

Conclusions

The antibody response substantially waned after 90-120 days post-booster dose. The heterologous mRNA and the viral vector booster demonstrated higher detectable rate of humoral immune responses against the Omicron variant compared to the inactivated BBIBP booster. Nevertheless, an additional fourth dose is recommended to maintain immune response against infection.

Current state and challenges in respiratory syncytial virus drug discovery and development

Human respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections (LRTI) in young children and elderly people worldwide. Recent significant progress in our understanding of the structure and function of RSV proteins has led to the discovery of several clinical candidates targeting RSV fusion and replication. These include both the development of novel small molecule interventions and the isolation of potent monoclonal antibodies. In this review, we summarize the state-of-the-art of RSV drug discovery, with a focus on the characteristics of the candidates that reached the clinical stage of development. We also discuss the lessons learned from failed and discontinued clinical developments and highlight the challenges that remain for development of RSV therapies.

The value of serum neutralizing antibody in evaluating predictability of COVID-19 after recovery and the validation of vaccine

BACKGROUND

This work aimed to study natural humoral immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

METHODS

Chemiluminescent immunoassay (CLIA) was used to detect the neutralizing antibody (Nabs) and IgG.

RESULTS

Nabs peaked on days 57-96 after symptom onset and remained detected on days 97-132. The Nabs in the 32 patients who were dynamically monitored showed four changing patterns. The titers of Nabs and IgG were correlated, and three modes of relationship were found between them.

CONCLUSIONS

Nabs showed a regular change in the course of coronavirus disease 2019 (COVID-19). The detection of Nabs is very important for monitoring the course of COVID-19 and predicting the strength of antibody protection.

The development and application of pseudoviruses: assessment of SARS-CoV-2 pseudoviruses

Although most Coronavirus disease (COVID-19) patients can recover fully, the disease remains a significant cause of morbidity and mortality. In addition to the consequences of acute infection, a proportion of the population experiences long-term adverse effects associated with SARS-CoV-2. Therefore, it is still critical to comprehend the virus's characteristics and how it interacts with its host to develop effective drugs and vaccines against COVID-19. SARS-CoV-2 pseudovirus, a replication-deficient recombinant glycoprotein chimeric viral particle, enables investigations of highly pathogenic viruses to be conducted without the constraint of high-level biosafety facilities, considerably advancing virology and being extensively employed in the study of SARS-CoV-2. This review summarizes three methods of establishing SARS-CoV-2 pseudovirus and current knowledge in vaccine development, neutralizing antibody research, and antiviral drug screening, as well as recent progress in virus entry mechanism and susceptible cell screening. We also discuss the potential advantages and disadvantages.

Association of selenium profile with neutralizing antibody response to inactivated SARS-CoV-2 vaccination

BACKGROUND

Selenium profile has been related with humoral immune response after vaccination, but evidence with regard to inactivated SARS-CoV-2 vaccine is lacking.

OBJECTIVE

The current study aimed to examine the relationship between selenium profile and neutralizing antibody response to inactivated SARS-CoV-2 vaccine.

METHODS

Plasma selenium and selenoprotein P concentrations, neutralizing antibody against the wild-type and Omicron variant were measured at baseline and at 14 days, 98 days after the third dose of inactivated SARS-CoV-2 vaccine.

RESULTS

Neutralizing antibody against the wild-type and Omicron variant increased significantly after the third vaccination dose. Both higher plasma selenium and selenoprotein P were associated with increased neutralizing antibody against the wild-type strain at baseline. Moreover, higher plasma selenoprotein P was associated with increased neutralizing antibody against Omicron variant at baseline. However, nonsignificant association were observed after the third vaccine dose.

CONCLUSION

Higher selenium profile was associated with neutralizing antibody response before the third dose of inactivated SARS-CoV-2 vaccine, but not after the third dose. Further prospective cohort studies are warranted to confirm our findings.

Generation of whole-porcine neutralizing antibodies of an alphacoronavirus by single B cell antibody technology

Porcine epidemic diarrhea virus (PEDV) is an alphacoronavirus that causes severe morbidity and mortality in piglets, resulting in substantial economic losses to the swine industry. While vaccination is currently the most effective preventive measure, existing vaccines fail to provide complete and reliable protection against PEDV infection. Consequently, there is a need to explore alternative or complementary strategies to address this issue. In this study, we utilized single B cell antibody technology to obtain a potent neutralizing antibody, C62, which specifically targets the receptor binding domain S1B of the PEDV-S1 protein. C62 exhibited potent neutralizing activity against PEDV and inhibited viral attachment to the cell surface in vitro. Furthermore, the effectiveness of C62 in mitigating PEDV infection was demonstrated in vivo, as evidenced by the delayed onset of diarrhea and reduced mortality rates observed in piglets following oral administration of C62. Our study provides an alternative approach for controlling PEDV infection. Meanwhile, C62 holds promise as a therapeutic biological agent to complement existing vaccines. More importantly, our study forms a solid foundation for the development of whole-porcine neutralizing antibodies against other swine coronaviruses, thus contributing to the overall improvement of swine health.

Age and prior vaccination determine the antibody level in children with primary SARS-CoV-2 Omicron infection

BACKGROUND

Protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection relies on immunity generated after primary infection. However, humoral immunity following primary infection with the Omicron variant is not well understood.

METHODS

We prospectively recruited children <19 years with virologically-confirmed SARS-CoV-2 infection at National Cheng Kung University Hospital from February 2022 to September 2022 during the first wave of Omicron BA.2 outbreak in Taiwan. Serum samples were collected one month after acute infection to measure anti-spike protein receptor binding domain antibody levels and surrogate virus neutralizing antibody (NAb) levels against wild type disease and variants.

RESULTS

Of the 164 patients enrolled, most were under 5 years (65.2%) with a diagnosis of upper respiratory tract infection. Children under 6 months with maternal coronavirus disease 2019 (COVID-19) vaccination had higher levels of both anti-SARS-CoV-2 spike antibody (119.0 vs 27.4 U/ml, p < 0.05) and anti-wild type NAb (56.9% vs 27.6% inhibition, p = 0.001) than those without. Children aged 5-12 years with prior vaccination had higher anti-spike antibody, anti-wild type, and anti-Omicron BA.2 NAb levels than those without (all p < 0.05). In previously naïve children without maternal or self-vaccination, those 6 months to 2 years had the highest antibody levels. Multivariable linear regression analysis showed age was the only independent factor associated with antibody level.

CONCLUSIONS

In our study, children aged 6 months to 2 years have the highest antibody responses to SARS-CoV-2 Omicron variant infection. Age and prior vaccination are the main factors influencing the immunogenicity of SARS-CoV-2 infection.

Analysis of ocular fluid in patients with ranibizumab-recalcitrant neovascular age-related macular degeneration who have serum anti-ranibizumab antibodies

PURPOSE

To evaluate whether anti-drug antibodies (ADAs) are present in the ocular fluid of patients with ranibizumab-recalcitrant neovascular age-related macular degeneration (nAMD).

METHODS

Two serum ADA-positive ranibizumab-recalcitrant patients and two serum ADA-negative controls were recruited from patients with nAMD treated with ranibizumab monotherapy. Recalcitrance was defined as persistent fluid after ≥6 monthly ranibizumab injections. Serum and aqueous humor ADAs were detected by enzyme-linked immunosorbent assay and immunoprecipitation, respectively.

RESULTS

Two of 156 ranibizumab-treated patients were ADA-positive. The patients received six and 14 ranibizumab injections, respectively, up to 4 weeks prior to blood collection. The serum ADA concentration was estimated to be approximately 50,000 ng/mL. Neutralizing ADAs were confirmed in both samples. A specific band was detected by immunoprecipitation only in ADA-positive samples, consistent with the results of enzyme-linked immunosorbent assay. Based on an assessment of the degree of sensitivity of commercially available anti-ranibizumab antibodies, it was estimated that the immunoprecipitation method could detect ADA levels >30 ng. Nevertheless, ADAs were not detected in the aqueous humor of either the experimental or control group.

CONCLUSION

In the aqueous humor, ADAs are either not present or are present at a lower concentration than that which can be detected by immunoprecipitation. This presumably reflects the fact that blood ADA is the product of systemic circulation clearance through anterior elimination of intravitreal ranibizumab. Based on our results, ADAs do not return to the eye in sufficient quantities to interfere with the action of ranibizumab in the vitreous cavity.

Evaluation of immune response to SARS-CoV-2 Omicron sublineages six months after different vaccination regimens in Italy

The Omicron variant is the most divergent, displaying more mutations than previous SARS-CoV-2 variants, particularly in the gene that encodes the spike protein. This study aimed to assess the persistence of neutralizing antibodies towards the SARS-CoV-2 Omicron sublineages (BA.2, BA.5, BQ.1, XBB and XBB1.5) six months after the third dose in different vaccination regimens. Subjects who received 3 doses of mRNA vaccine retained their neutralization activity against BA.2 and BA.5, even though 56.3% and 66.7% showed a ≥ 2-fold reduction in the neutralizing antibody titre, respectively. Subjects who had received the adenovirus-based vaccine plus a booster dose of mRNA vaccine retained their neutralization activity especially against BA.2. With regard to BQ.1, XBB and XBB.1.5, the majority of the subjects showed a ≥ 2-fold reduction in neutralizing antibody titre, with the greatest evasion being observed in the case of XBB. Overall, our results provide further evidence that triple homologous/heterologous vaccination and hybrid immunity result in detectable neutralizing antibodies against the ancestral virus; however, emerging Omicron sublineages, such as XBB and XBB.1.5, show a great evasive capacity, which compromises the effectiveness of current COVID-19 vaccines.

Boosted production of antibodies that neutralized different SARS-CoV-2 variants in a COVID-19 convalescent following messenger RNA vaccination - a case study

Vaccinated convalescents do not develop severe COVID-19 after infection with new SARS-CoV-2 variants. We questioned how messenger RNA (mRNA) vaccination of convalescents provides protection from emerging virus variants. From the cohort of 71 convalescent plasma donors, we identified a patient who developed immune response to infection with SARS-CoV-2 variant of 20A clade and who subsequently received mRNA vaccine encoding spike (S) protein of strain of 19A clade. We showed that vaccination increased the production of immune cells and anti-S antibodies in the serum. Serum antibodies neutralized not only 19A and 20A, but also 20B, 20H, 21J, and 21K virus variants. One of the serum antibodies (100F8) completely neutralized 20A, 21J, and partially 21K strains. 100F8 was structurally similar to published Ab188 antibody, which recognized non-conserved epitope on the S protein. We proposed that 100F8 and other serum antibodies of the patient which recognized non- and conserved epitopes of the S protein, could have additive or synergistic effects to neutralize various virus variants. Thus, mRNA vaccination could be beneficial for convalescents because it boosts production of neutralizing antibodies with broad-spectrum activity.

Neutralization escape by SARS-CoV-2 Omicron subvariant BA.2.86

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) variant BA.2.86 has over 30 mutations in spike compared with BA.2 and XBB.1.5, which raised the possibility that BA.2.86 might evade neutralizing antibodies (NAbs) induced by vaccination or infection. In this study, we show that NAb titers are substantially lower to BA.2.86 compared with BA.2 but are similar or slightly higher than to other current circulating variants, including XBB.1.5, EG.5.1, and FL.1.5.1. Moreover, NAb titers against all these variants were higher in vaccinated individuals with a history of XBB.1.5 infection compared with vaccinated individuals with no history of XBB.1.5 infection, suggesting the potential utility of the monovalent XBB.1.5 mRNA boosters.

Kinetics of adaptive immune responses after administering mRNA-Based COVID-19 vaccination in individuals with and without prior SARS-CoV-2 infections

OBJECTIVE

We aimed to compare the adaptive immune response in individuals with or without prior SARS-CoV-2 infections following the administration of mRNA-based COVID-19 vaccines.

METHODS

A total of 54 participants with ages ranging from 37 to 56 years old, consisting of 23 individuals without a history of SARS-CoV-2 infection (uninfected group) and 31 individuals with prior infection of SARS-CoV-2 (infected group) who have received two doses of mRNA SARS-CoV-2 vaccines were enrolled in this study. We measured the IFN-γ level upon administration of BNT162b2 (PF) or mRNA-1273 (MO) by QuantiFERON SARS-CoV-2. The production of neutralizing antibodies was evaluated by a surrogate virus neutralization assay, and the neutralizing capacity was assessed by a plaque reduction neutralization test (PRNT50). The immune response was compared between the two groups.

RESULTS

A significantly higher level of IFN-γ (p < 0.001) and neutralization antibodies (p < 0.001) were observed in the infected group than those in the uninfected group following the first administration of vaccines. The infected group demonstrated a significantly higher PRNT50 titer than the uninfected group against the Wuhan strain (p < 0.0001). Still, the two groups were not significantly different against Delta (p = 0.07) and Omicron (p = 0.14) variants. Following the second vaccine dose, T- and B-cell levels were not significantly increased in the infected group.

CONCLUSION

A single dose of mRNA-based COVID-19 vaccines would boost immune responses in individuals who had previously contracted SARS-CoV-2.

Sequential heterologous immunization with COVID-19 vaccines induces broader neutralizing responses against SARS-CoV-2 variants in comparison with homologous boosters

The recently prevalent variants of concerns (VOCs) of SARS-CoV-2 belong to Omicron variants which display increased transmissibility and evade from immune protection generated by vaccines and/or natural infections. Better immunization strategies should be explored to induce broader immune responses against evolving SARS-CoV-2 variants. Here, we used inactivated vaccines derived from ancestral (Wu), Delta (Del) and Omicron (Omi) strains to immunize mice with homologous booster (3 × Wu, 3 × Del and 3 × Omi) or heterologous sequential booster (Wu/Del/Omi and Omi/Wu/Del) to evaluate their responses against two pre-Omicron (Wu and Del) and four Omicron variants. Even though neutralization responses against Wu and Del variants were similar in heterologous and homologous immunization groups, heterologous immunization groups induced significantly stronger neutralizing antibody against BA.1 (4.1-11 folds higher) and BA.2 (4.7-14.2 folds higher) than those of homologous immunization groups. While homologous immunization only induced strong neutralizing responses to either pre-Omicron variants (Wu and Del) in 3 × Wu and 3 × Del groups or to Omicron variants (BA.1 and BA.2) in 3 × Omi group, heterologous immunization groups induced strong and broader neutralizing responses to both pre-Omicron (Wu, Del) and Omicron variants (BA.1 and BA.2). Homologous and heterologous immunization groups elicited similar antigen-specific T cell (IFN-γ+) and B cell responses. Compared with homologous immunization, heterologous immunization could induce stronger plasma cell responses, which have the potential to generate broader and stronger neutralizing antibodies. However, neither heterologous nor homologous immunization groups induced strong neutralizing antibody against variants with bigger genetic deviation, such as BA.4/5 or BF.7, only weak neutralizing responses were induced. Surveillance on SARS-CoV2 variants evolution and immunization strategy are needed to explore better vaccines with broader and stronger neutralizing antibodies against post pandemic COVID-19.

Blockade of TGF-β signalling alleviates human adipose stem cell senescence induced by native ECM in obesity visceral white adipose tissue

BACKGROUND

Abdominal obesity is appreciated as a major player in insulin resistance and metabolically dysfunctional adipose tissue. Inappropriate extracellular matrix (ECM) remodelling and functional alterations in human adipose stromal/stem cells (hASCs) have been linked with visceral white adipose tissue (vWAT) dysfunction in obesity. Understanding the interactions between hASCs and the native ECM environment in obese vWAT is required for the development of future therapeutic approaches for obesity-associated metabolic complications.

METHODS

The phenotypes and transcriptome properties of hASCs from the vWAT of obese patients and lean donors were assessed. The hASC-derived matrix from vWAT of obese or lean patients was generated in vitro using a decellularized method. The topography and the major components of the hASC-derived matrix were determined. The effects of the obese hASC-derived matrix on cell senescence and mitochondrial function were further determined.

RESULTS

We showed that hASCs derived from the vWAT of obese patients exhibited senescence and were accompanied by the increased production of ECM. The matrix secreted by obese hASCs formed a fibrillar suprastructure with an abundance of fibronectin, type I collagen, and transforming growth factor beta 1 (TGF-β1), which resembles the native matrix microenvironment of hASCs in vWAT derived from obese patients. Furthermore, the obese hASC-derived matrix promoted lean hASC ageing and induced mitochondrial dysfunction compared to the lean hASC-derived matrix. Blockade of TGF-β1 signalling using an anti-TGF-β1 neutralizing antibody alleviated the lean hASC senescence and mitochondrial dysfunction induced by the obese hASC-derived matrix.

CONCLUSIONS

Native ECM in obesity vWAT initiates hASC senescence through TGF-β1-mediated mitochondrial dysfunction. These data provide a key mechanism for understanding the importance of cell-ECM interactions in hASCs senescence in obesity.

Homologous or heterologous COVID-19 vaccine schemes: comparison of immune responses and side effects

Real-life data are needed regarding the appropriate time and selection of vaccination strategies, homologous or heterologous. We aimed to compare neutralizing antibody levels and side effects in different vaccination schemes. The study included 310 Health Care Workers (HCWs) vaccinated with 5 different schemes. Antispike/RBD IgG levels were measured between 28 and 60 days after the last dose. Side effects in participants were recorded, and pharmacovigilance records were reviewed from the outpatient vaccine clinic. Mean age of the participants was 38 ± 11 years of whom 226 (72.9%) were female, and 84 (27.1%) were male. After booster doses, increasing antibody levels were detected in all groups. Mean antibody levels were detected to be statistically lower in 3 doses of inactivated vaccines group. The side effects were no significant difference between groups. Booster dose administration with mRNA vaccines stands out as the most accurate strategy for those at risk of contracting severe COVID-19 and HCWs caring for this population.

Lack of neutralizing antibodies against influenza A viruses in adults during the 2022/2023 winter season - a serological study using retrospective samples collected in Hong Kong

OBJECTIVES

Since the onset of the COVID-19 pandemic in 2020, there has been a significant decline in seasonal influenza infection cases in Hong Kong. However, this decline has also resulted in reduced opportunities for the development of influenza-specific antibodies in the community. The levels of antibodies required for protection against recently circulating influenza A viruses in the post-COVID-19 era remain unclear.

METHODS

This study involved the analysis of paired plasma samples collected from 479 healthy adults in Hong Kong in 2021 and 2022. The neutralizing titers of plasma against influenza A (H1N1) and (H3N2) viruses circulating before and after the COVID-19 outbreak were determined using a microneutralization assay.

RESULTS

The H1N1 and H3N2 vaccine strains selected for the 2022/23 season were found to be closely related to the recently circulating viruses. However, in the samples collected in 2022, only 14.61% and 0.42% showed a neutralization titer (MN50) ≥1:20 against H1N1 A/Wisconsin/588/2019 (H1/Wis19) and H3N2 A/Darwin/6/2021 (H3/Dar21), respectively. Notably, participants who reported receiving annual flu vaccinations exhibited a higher seropositive rate for H1/Wis19 compared to those who had never received the flu vaccine (28.06% vs. 5.30%).

CONCLUSION

Our results indicate that adults in Hong Kong generally lack neutralizing antibodies against circulating influenza A viruses, particularly H3N2. These findings underscore the importance of promoting flu vaccination in the post-COVID-19 era.

Antigenic variation in hemagglutinin-neuraminidase of Newcastle disease virus isolated from Tibet, China

Vaccines are widely used to prevent Newcastle disease virus (NDV). Under the pressure of immunization, NDVs with mutations among epitopes of F and HN protein were isolated, which indicates that the efficiency of vaccine may decrease in terms of preventing emerged NDV. However, the lack of evidences to support whether these mutations contribute to antigenic mutation and immune escape in NDV leading to the controversy that the matched vaccine is more effective than the mismatched vaccine. In this study, a genotype VII velogenic NDV strain (C22) was isolated from a vaccinated farm in Tibet, China. We found that this strain was close to NDV from east China, but it had a specific mutation (K138R) in one epitope (131DYIGGIGKE139) of HN protein. This mutation might change the interaction between amino acids in stalk-head link region of HN protein and then induce the specific antibody to worse recognize the C22 strain, but it did not alter viral virulence and growth ability. Then, the C22 strain was attenuated via modification of the F protein cleavage site to generate a matched vaccine. Comparing to a mismatched vaccine (LaSota), this matched vaccine showed advantages in inhibiting viral shedding and tissue damage. However, both vaccines induced chicken to generate similar level of neutralizing antibodies against C22, C22mut (R138K) and LaSota. These results suggest that the epitope mutation is insufficient to help NDV escaping neutralizing antibodies of vaccinated chicken, supporting that the merits of NDV matched vaccine are not totally related to humoral immunity.

A fine-tuned yeast surface-display/secretion platform enables the rapid discovery of neutralizing antibodies against Clostridioides difficile toxins

BACKGROUND

Neutralizing antibody plays a key role in protecting hosts from invasive pathogens and their virulent components. Current high-throughput assays for antibody screening are based on binding activities. However, those antibodies with high affinity may not have neutralizing activities. Subsequent functionality assays are necessary to identify neutralizing antibodies from binders with high affinity to their target antigens, which is laborious and time-consuming. Therefore, a versatile platform that can rapidly identify antibodies with both high binding affinity and neutralizing activity is desired to curb future pandemics like COVID-19.

RESULTS

In this proof-of-concept study, we adapted Saccharomyces cerevisiae to either display human antibodies on the yeast surface or secrete soluble antibodies into the cultivation supernatant under a controllable 'switch' through different carbon source induced promoters. Initially, an engineered chimeric-bispecific Fab antibody, derived from humanized nanobodies against both Clostridioides difficile toxin A and B (TcdA and TcdB), was successfully expressed either on the yeast cell surface or in the culture medium with intact bioactivity, suggesting the applicability of our system in antibody display and secretion. Next, a combinatorial Fab library was constructed from B cells isolated from a convalescent patient with a high serological neutralizing titer against TcdB. Following three rounds of magnetic bead enrichment and one round of flow cytometry sorting, antibodies against TcdB were enriched efficiently. We then sorted out single binders with high binding affinity and induced them to express soluble antibodies in culture medium. The neutralizing activity of culture supernatant was analyzed using cell-based assay immediately. This way, we rapidly identified two unique neutralizers (out of seven binders) that can neutralize the cytotoxicity of TcdB.

CONCLUSION

The antibody screening platform described here simplifies the neutralizing antibody discovery procedure and will be an attractive alternative for screening functional antibodies against infectious diseases.

Dynamics of neutralizing antibodies against severe fever with thrombocytopenia syndrome virus

OBJECTIVES

Severe fever with thrombocytopenia syndrome (SFTS) virus (SFTSV) is an emerging tick-borne bunyavirus with a high pathogenicity. Little is known about the longitudinal dynamics of the SFTSV-specific neutralizing antibody (NAb) and the related factors in patients with SFTS.

METHODS

A prospective cohort study of patients with laboratory-confirmed SFTS were conducted. Antiglomerulonephritis-immunoglobulin G (anti-Gn-IgG) and NAb titers were examined in serially collected serum samples, and their dynamic features were analyzed.

RESULTS

NAb was initially detected at 15 days after symptom onset in surviving patients with SFTS, with positive rates of 37.21% (16/43), whereas neither anti-Gn-IgG antibody nor NAb was detected in patients with fatal SFTS during their hospitalization. The NAb levels reached the peak at 2 months after symptom onset, and then gradually declined, with a rapid downward trend from 6 months to 4 years and a relatively slow downward trend from 5 to 10 years. There was a positive correlation between NAb and anti-Gn-IgG titers in surviving patients with SFTS (r = 0.699, P <0.001). Patients with a mild illness or low viral load experienced early NAb seroconversion. Six different dynamic patterns of NAb were noted in surviving patients.

CONCLUSION

These data provide useful information regarding the dynamic changes in NAb in patients with SFTS during the acute and convalescent phases and the follow-up period.

Safety and immunogenicity against ancestral, Delta and Omicron virus variants following a booster dose of an inactivated whole-virus COVID-19 vaccine (VLA2001): Interim analysis of an open-label extension of the randomized, controlled, phase 3 COV-COMPARE trial

OBJECTIVES

Booster doses for COVID-19 vaccinations have been shown to amplify the waning immune response after primary vaccination and to enhance protection against emerging variants of concern (VoCs). Here, we aimed to assess the immunogenicity and safety of a booster dose of an inactivated whole-virus COVID-19 vaccine (VLA2001) after primary vaccination with 2 doses of either VLA2001 or ChAdOx1-S (Oxford-Astra Zeneca), including the cross-neutralization capacity against the Delta and Omicron VoCs.

METHODS

This interim analysis of an open-label extension of a randomized, controlled phase 3 trial assessed a single booster dose of an inactivated whole-virus COVID-19 vaccine (VLA2001) in healthy or medically stable adults aged 18 years and above, recruited in 21 clinical sites in the UK, who had previously received two doses of either VLA2001 or ChAdOx1-S. Safety outcomes were frequency and severity of solicited injection site and systemic reactions within 7 days after booster vaccination as well as frequency and severity of any unsolicited adverse events (AE) after up to 6 months. Immunogenicity outcomes were the immune response to ancestral SARS-CoV-2 assessed 14 days post booster expressed as geometric mean titres (GMT), GMT fold ratios and seroconversion of specific neutralizing antibodies and S-protein binding IgG antibodies. Immunogenicity against the Delta and Omicron VoCs was assessed as a post-hoc outcome with a pseudovirus neutralization antibody assay. This study is registered with ClinicalTrials.gov, NCT04864561, and is ongoing.

RESULTS

A booster dose of VLA2001 was administered to 958 participants, of whom 712 had been primed with VLA2001, and 246 with ChAdOx1-S. Within 7 days following these booster doses, 607 (63.4%) participants reported solicited injection site reactions, and 487 (50.8%) reported solicited systemic reactions. Up to 14 days post booster, 751 (78.4%) participants reported at least one adverse event. The tolerability profile of a booster dose of VLA2001 was similar in VLA2001-primed and ChAdOx1-S-primed participants. In VLA2001-primed participants, the GMT (95% CI) of neutralizing antibodies increased from 32.5 (22.8, 46.3) immediately before to 521.5 (413.0, 658.6) 2 weeks after administration of the booster dose, this corresponds to a geometric mean fold rise (GMFR) of 27.7 (20.0, 38.5). Compared to 2 weeks after the second priming dose, the GMFR was 3.6 (2.8, 4.7). In the ChAdOx1-S primed group, the GMT (95% CI) of neutralizing antibodies increased from 65.8 (43.9, 98.4) immediately before to 188.3 (140.3, 252.8) 2 weeks after administration of the booster dose, a geometric mean fold rise (GMFR) of 3.0 (2.2, 4.0). Compared to 2 weeks after the second priming dose, the GMFR was 1.6 (1.1, 2.2). For S-protein binding IgG antibodies, the pre- versus post-booster GMT fold ratio (95% CI) was 34.6 (25.0, 48.0) in the VLA2001-primed group and 4.0 (3.0, 5.2) in the ChAdOx1-S-primed group. Compared to 2 weeks after the second priming dose, the GMT fold rise of IgG antibodies was 3.8 (3.2, 4.6) in the VLA2001-primed group and 1.2 (0.9, 1.6) in the ChAdOx1-S-primed group. The GMT against Delta (B.1.617.2) and Omicron (BA.4/5) increased from 4.2 to 260, and from 2.7 to 56.7, respectively, when boosting subjects previously primed with VLA2001. Following the boost, 97% of subjects primed with VLA2001 had detectable Delta- and 94% Omicron-neutralizing antibodies. In subjects primed with ChAdOx1-S, the GMT against Delta and Omicron titres increased from 9.1 to 92.5, and from 3.6 to 12.3, respectively. After boosting, 99% of subjects primed with ChAdOx1-S had detectable Delta- and 70% Omicron-neutralizing antibodies. In both VLA2001 and ChAdOx1-S primed subjects, the additional VLA2001 dose boosted T cell responses against SARS-CoV-2 antigens to levels above those observed before the booster dose.

CONCLUSION

A booster dose of VLA2001 was safe and well tolerated after primary immunization with VLA2001 and ChAdOx1-S. The tolerability of a booster dose of VLA2001 was similar to the favourable profile observed after the first and second priming doses. Both in a homologous and a heterologous setting, boosting resulted in higher neutralizing antibody titres than after primary immunization and significant increases in cross-neutralization titres against Delta and Omicron were observed after the booster dose. These data support the use of VLA2001 in booster programmes in ChadOx1-S primed groups.

Cross-neutralizing protection of vaginal and oral mucosa from HPV challenge by vaccination in a mouse model

The species and tissue specificities of HPV (human papillomavirus) for human infection and disease complicates the process of prophylactic vaccine development in animal models. HPV pseudoviruses (PsV) that carry only a reporter plasmid have been utilized in vivo to demonstrate cell internalization in mouse mucosal epithelium. The current study sought to expand the application of this HPV PsV challenge model with both oral and vaginal inoculation and to demonstrate its utility for testing vaccine-mediated dual-site immune protection against several HPV PsV types. We observed that passive transfer of sera from mice vaccinated with the novel experimental HPV prophylactic vaccine RG1-VLPs (virus-like particles) conferred HPV16-neutralizing as well as cross-neutralizing Abs against HPV39 in naïve recipient mice. Moreover, active vaccination with RG1-VLPs also conferred protection to challenge with either HPV16 or HPV39 PsVs at both vaginal and oral sites of mucosal inoculation. These data support the use of the HPV PsV challenge model as suitable for testing against diverse HPV types at two sites of challenge (vaginal vault and oral cavity) associated with the origin of the most common HPV-associated cancers, cervical cancer and oropharyngeal cancer.

SARS-CoV-2 vaccine breakthrough infections (VBI) by Omicron variant (B.1.1.529) and consequences in structural and functional impact

This study investigated the efficacy of existing vaccines against hospitalization and infection due to the Omicron variant of COVID-19, particularly for those who received two doses of Moderna or Pfizer vaccines and one dose of Johnson & Johnson vaccine or who were vaccinated more than five months before. A total of 36 variants in Omicron's spike protein, targeted by all three vaccinations, have made antibodies less effective at neutralizing the virus. The genotyping of the SARS-CoV-2 viral sequence revealed clinically significant variants such as E484K in three genetic mutations (T95I, D614G, and del142-144). A woman showed two of these mutations, indicating a potential risk of infection after successful immunization, as recently reported by Hacisuleyman (2021). We examine the effects of mutations on domains (NID, RBM, and SD2) found at the interfaces of the spike domains Omicron B.1.1529, Delta/B.1.1529, Alpha/B.1.1.7, VUM B.1.526, B.1.575.2, and B.1.1214 (formerly VOI Iota). We tested the affinity of Omicron for ACE2 and found that the wild- and mutant-spike proteins were using atomistic molecular dynamics simulations. According to the binding free energies calculated during mutagenesis, the ACE2 bound Omicron spikes more strongly than the wild strain SARS-CoV-2. T95I, D614G, and E484K are three substitutions that significantly contribute to RBD, corresponding to ACE2 binding energies and a doubling of the electrostatic potential of Omicron spike proteins. The Omicron appears to bind to ACE2 with greater affinity, increasing its infectivity and transmissibility. The spike virus was designed to strengthen antibody immune evasion through binding while boosting receptor binding by enhancing IgG and IgM antibodies that stimulate human β-cell, as opposed to the wild strain, which has more vital stimulation of both antibodies.

Neutralizing antibody levels associated with injectable and aerosolized Ad5-nCoV boosters and BA.2 infection

BACKGROUND

Several COVID-19 vaccines are in widespread use in China. Few data exist on comparative immunogenicity of different COVID-19 vaccines given as booster doses. We aimed to assess neutralizing antibody levels raised by injectable and inhaled aerosolized recombinant adenovirus type 5 (Ad5)-vectored COVID-19 vaccine as a heterologous booster after an inactivated COVID-19 vaccine two-dose primary series.

METHODS

Using an open-label prospective cohort design, we recruited 136 individuals who had received inactivated vaccine primary series followed by either injectable or inhaled Ad5-vectored vaccine and measured neutralizing antibody titers against ancestral SARS-CoV-2 virus and Omicron BA.1 and BA.5 variants. We also measured neutralizing antibody levels in convalescent sera from 39 patients who recovered from Omicron BA.2 infection.

RESULTS

Six months after primary series vaccination, neutralizing immunity against ancestral SARS-CoV-2 was low and neutralizing immunity against Omicron (B.1.1.529) was lower. Boosting with Ad5-vectored vaccines induced a high immune response against ancestral SARS-CoV-2. Neutralizing responses against Omicron BA.5 were ≥ 80% lower than against ancestral SARS-CoV-2 in sera from prime-boost subjects and in convalescent sera from survivors of Omicron BA.2 infection. Inhaled aerosolized Ad5-vectored vaccine was associated with greater neutralizing titers than injectable Ad5-vectored vaccine against ancestral and Omicron SARS-CoV-2 variants.

CONCLUSIONS

These findings support the current strategy of heterologous boosting with injectable or inhaled Ad5-vectored SARS-CoV-2 vaccination of individuals primed with inactivated COVID-19 vaccine.

Seroprevalence of neutralizing antibodies to human mastadenovirus serotypes 3 and 7 in healthy children from guangdong province

Severe adenovirus pneumonia is becoming more common in children infected with human mastadenovirus (HAdV)-3 and HAdV-7 than in those infected with other types of adenoviruses. Recently, there has been a trend toward an increasing prevalence of pneumonia caused by HAdV-7, an important viral pathogen in Pediatric Intensive Care Unit infections. Children infected with HAdV-7 have more serious symptoms of acute respiratory infections and other complications than those infected with HAdV-3. No specific anti-adenovirus drugs or vaccines are available for treatment or prevention. Therefore, we investigated the seroprevalence and titer levels of neutralizing antibodies (NAbs) against HAdV-3 and HAdV-7 in healthy children in Guangdong Province. We found that the seropositivity rates and antibody titers for HAdV-3 NAb were higher than those for HAdV-7 NAb. In children between 6 and 12 months of age, the seropositivity rates and titers were significantly low against HAdV-3 and HAdV-7. The HAdV-7-positive rate was significantly higher in the HAdV-3-positive samples than in the HAdV-3-negative samples. The HAdV-7 NAbs carried by the 0-6-month age group were dominated by low titers. These results reveal a low level of herd immunity against HAdV-3 and HAdV-7 in children, clarifying the importance of monitoring these two highly virulent adenoviruses, developing prophylactic vaccines, and predicting potential outbreaks.

Research progress in methods for detecting neutralizing antibodies against SARS-CoV-2

The emergence of SARS-CoV-2 has seriously affected the lives of people worldwide. Clarifying the attenuation rule of SARS-CoV-2 neutralizing antibody (NAb) in vivo is the key to prevent reinfection and recurrence of virus. Currently, the commonly used methods for detecting NAb include virus neutralization tests, pseudovirus neutralization assays, lateral flow immunochromatography and enzyme-linked immunosorbent assays. The detection of NAb not only can be used to evaluate the level of immunity after vaccination or infection but also can provide important theoretical support for virus reinfection, recurrence and vaccine iteration. In this research, the related technologies of SARS-CoV-2 NAb detection were reviewed, aiming to provide better research ideas for SARS-CoV-2 epidemic prevention and control.

Fourth mRNA vaccination increases cross-neutralizing antibody titers against SARS-CoV-2 variants, including BQ.1.1 and XBB, in a very elderly population

BACKGROUND

Omicron variants with immune evasion have emerged, and they continue to mutate rapidly, raising concerns about the weakening of vaccine efficacy, and the very elderly populations are vulnerable to Coronavirus Disease 2019 (COVID-19). Therefore, to investigate the effect of multiple doses of mRNA vaccine for the newly emerged variants on these populations, cross-neutralizing antibody titers were examined against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) variants, including BQ.1.1 and XBB.

METHODS

Blood samples were taken from residents at four long-term care facilities in Hyogo prefecture, Japan (median age, 91 years), after 3rd (n = 67) and 4th (n = 48) mRNA vaccinations, from April to October 2022. A live virus microneutralization assay was performed to determine the neutralizing antibody titers in participants' sera.

RESULTS

After 3rd vaccination, cross-neutralizing antibody prevalence against conventional (D614G) virus, Delta, Omicron BA.2, BA.5, BA.2.75, BQ.1.1, and XBB were 100%, 97%, 81%, 51%, 67%, 4%, and 21%, respectively. After 4th vaccination, the antibody positivity rates increased to 100%, 100%, 98%, 79%, 92%, 31%, and 52%, respectively. The 4th vaccination significantly increased cross-neutralizing antibody titers against all tested variants.

CONCLUSION

The positivity rates for BQ.1.1 and XBB increased after 4th vaccination, although the titer value was lower than those of BA.5 and BA.2.75. Considering the rapid mutation of viruses and the efficacy of vaccines, it may be necessary to create a system that can develop vaccines suitable for each epidemic in consideration of the epidemic of the virus.

Omicron BA.1 neutralizing antibody response following Delta breakthrough infection compared with booster vaccination of BNT162b2

BACKGROUND

Longitudinal data are lacking to compare booster effects of Delta breakthrough infection versus third vaccine dose on neutralizing antibodies (NAb) against Omicron.

METHODS

Participants were the staff of a national research and medical institution in Tokyo who attended serological surveys on June 2021 (baseline) and December 2021 (follow-up); in between, the Delta-dominant epidemic occurred. Of 844 participants who were infection-naïve and had received two doses of BNT162b2 at baseline, we identified 11 breakthrough infections during follow-up. One control matched to each case was selected from boosted and unboosted individuals. We compared live-virus NAb against Wild-type, Delta, and Omicron BA.1 across groups.

RESULTS

Breakthrough infection cases showed marked increases in NAb titers against Wild-type (4.1-fold) and Delta (5.5-fold), and 64% had detectable NAb against Omicron BA.1 at follow-up, although the NAb against Omicron after breakthrough infection was 6.7- and 5.2-fold lower than Wild-type and Delta, respectively. The increase was apparent only in symptomatic cases and as high as in the third vaccine recipients.

CONCLUSIONS

Symptomatic Delta breakthrough infection increased NAb against Wild-type, Delta, and Omicron BA.1, similar to the third vaccine. Given the much lower NAb against Omicron BA.1, infection prevention measures must be continued irrespective of vaccine and infection history while the immune evasive variants are circulating.

Broadly neutralizing antibodies against Omicron variants of SARS-CoV-2 derived from mRNA-lipid nanoparticle-immunized mice

The COVID-19 pandemic continues to threaten human health worldwide as new variants of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerge. Currently, the predominant circulating strains around the world are Omicron variants, which can evade many therapeutic antibodies. Thus, the development of new broadly neutralizing antibodies remains an urgent need. In this work, we address this need by using the mRNA-lipid nanoparticle immunization method to generate a set of Omicron-targeting monoclonal antibodies. Five of our novel K-RBD-mAbs show strong binding and neutralizing activities toward all SARS-CoV-2 variants of concern (Alpha, Beta, Gamma, Delta and Omicron). Notably, the epitopes of these five K-RBD-mAbs are overlapping and localized around Y453 and F486 of the spike protein receptor binding domain (RBD). Chimeric derivatives of the five antibodies (K-RBD-chAbs) neutralize Omicron sublineages BA.1 and BA.2 with low IC₅₀ values ranging from 5.7 to 12.9 ng/mL. Additionally, we performed antibody humanization on broadly neutralizing chimeric antibodies to create K-RBD-hAb-60 and -62, which still retain excellent neutralizing activity against Omicron. Our results collectively suggest that these five therapeutic antibodies may effectively combat current and emerging SARS-CoV-2 variants, including Omicron BA.1 and BA.2. Therefore, the antibodies can potentially be used as universal neutralizing antibodies against SARS-CoV-2.

Safety and efficacy of inactivated COVID-19 vaccines in women vaccinated during the first trimester of pregnancy

OBJECTIVES

This study aimed to investigate the safety of the inactivated COVID-19 vaccines in early pregnant women in view of their adverse-effect profile and associated maternal-fetal complications, as well as to evaluate their immunogenicity.

METHODS

In this prospective observational cohort study, 232 women in their first trimester or those in the periconception period who inadvertently received two doses of inactivated COVID-19 vaccine between January 21, 2021, and January 14, 2022 were analyzed. Meanwhile, 735 unvaccinated early pregnancy women were also included in the study at a case-to-control ratio of 1:3.

RESULTS

The vaccination group did not have an increased miscarriage rate compared with that of the control group (P = 0.918). Furthermore, the birth defect rates in the vaccine group and control group were 0.83% and 1.0%, respectively. Vaccination did not increase the risk of small for gestational age, gestational diabetes mellitus, preterm, or hypertensive disorders of pregnancy (P >0.01). Within 12 weeks after the second dose, the inactivated vaccine effectively produced neutralizing antibody (NAb) against SARS-CoV-2. The NAb levels in the paired umbilical cord serum and maternal serum samples during delivery were negative in both groups. The T-cell subset remained within the normal range in both groups.

CONCLUSION

Therefore, our study proves that inactivated COVID-19 vaccines are safe for mothers and fetuses and also effective in producing NAb against SARS-CoV-2.

Immunotherapy of Epstein-Barr virus (EBV) infection and EBV-associated hematological diseases with gp350/CD89-targeted bispecific antibody

Acute and persistent infection of Epstein-Barr virus (EBV) is associated with several life-threatening hematological disorders, including lymphoproliferative disorders (LPD), hemophagocytic lymphohistiocytosis (HLH), and chronic active Epstein-Barr virus infection (CAEBV). Currently, there are no efficacious virus-targeted therapies for EBV-driven hematological diseases. To explore the potential of phagocytosis-based immunotherapy, we created a bispecific antibody by targeting the viral envelope protein gp350 with a novel EBV-neutralizing antibody (named R1) that was paired with a monoclonal antibody against CD89 for redirecting macrophages and neutrophils. In vitro study showed that the bispecific antibody enabled efficient phagocytosis of EBV and killing of gp350 + lymphoma cells in the presence of PBMC. In vivo studies in NSG mice inoculated with EBV showed that bispecific antibody dramatically reduced the viral load in blood, solid organs and tissues. Treatment of mice implanted with EBV-harboring Raji lymphoma cells efficiently prevented tumor formation and massive metastasis to solid organs. Treatment of mice implanted with whole blood from EBV-HLH patients was effective in reducing viral levels in blood and solid organ. The gp350/CD89 bispecific antibody was highly effective in clearing EBV and immunotherapy of EBV-driven hematological diseases such as LPD and EBV-HLH.