Optimized production of full-length PCV2d virus-like particles in Escherichia coli: A cost-effective and high-yield approach for potential vaccine antigen development

Porcine circovirus type 2 (PCV2) is a globally prevalent infectious pathogen affecting swine, with its capsid protein (Cap) being the sole structural protein critical for vaccine development. Prior research has demonstrated that PCV2 Cap proteins produced in Escherichia coli (E. coli) can form virus-like particles (VLPs) in vitro, and nuclear localization signal peptides (NLS) play a pivotal role in stabilizing PCV2 VLPs. Recently, PCV2d has emerged as an important strain within the PCV2 epidemic. In this study, we systematically optimized the PCV2d Cap protein and successfully produced intact PCV2d VLPs containing NLS using E. coli. The recombinant PCV2d Cap protein was purified through affinity chromatography, yielding 7.5 mg of recombinant protein per 100 ml of bacterial culture. We augmented the conventional buffer system with various substances such as arginine, β-mercaptoethanol, glycerol, polyethylene glycol, and glutathione to promote VLP assembly. The recombinant PCV2d Cap self-assembled into VLPs approximately 20 nm in diameter, featuring uniform distribution and exceptional stability in the optimized buffer. We developed the vaccine and immunized pigs and mice, evaluating the immunogenicity of the PCV2d VLPs vaccine by measuring PCV2-IgG, IL-4, TNF-α, and IFN-γ levels, comparing them to commercial vaccines utilizing truncated PCV2 Cap antigens. The HE staining and immunohistochemical tests confirmed that the PCV2 VLPs vaccine offered robust protection. The results revealed that animals vaccinated with the PCV2d VLPs vaccine exhibited high levels of PCV2 antibodies, with TNF-α and IFN-γ levels rapidly increasing at 14 days post-immunization, which were higher than those observed in commercially available vaccines, particularly in the mouse trial. This could be due to the fact that full-length Cap proteins can assemble into more stable PCV2d VLPs in the assembling buffer. In conclusion, our produced PCV2d VLPs vaccine elicited stronger immune responses in pigs and mice compared to commercial vaccines. The PCV2d VLPs from this study serve as an excellent candidate vaccine antigen, providing insights for PCV2d vaccine research.

Antibody-independent surface plasmon resonance assays for influenza vaccine quality control

Surface plasmon resonance (SPR)-based biosensors have emerged as a powerful platform for bioprocess monitoring due to their ability to detect biointeractions in real time, without the need for labeling. Paramount for the development of a robust detection platform is the immobilization of a ligand with high specificity and affinity for the in-solution species of interest. Following the 2009 H1N1 pandemic, much effort has been made toward the development of quality control platforms for influenza A vaccine productions, many of which have employed SPR for detection. Due to the rapid antigenic drift of influenza's principal surface protein, hemagglutinin, antibodies used for immunoassays need to be produced seasonally. The production of these antibodies represents a 6-8-week delay in immunoassay and, thus, vaccine availability. This review focuses on SPR-based assays that do not rely on anti-HA antibodies for the detection, characterization, and quantification of influenza A in bioproductions and biological samples. KEY POINTS: • The single radial immunodiffusion assay (SRID) has been the gold standard for the quantification of influenza vaccines since 1979. Due to antigenic drift of influenza's hemagglutinin protein, new antibody reagents for the SRID assay must be produced each year, requiring 6-8 weeks. The resulting delay in immunoassay availability is a major bottleneck in the influenza vaccine pipeline. This review highlights ligand options for the detection and quantification of influenza viruses using surface plasmon resonance biosensors.

Long-term monitoring of SARS-CoV-2 seroprevalence and variants in Ethiopia provides prediction for immunity and cross-immunity

Under-reporting of COVID-19 and the limited information about circulating SARS-CoV-2 variants remain major challenges for many African countries. We analyzed SARS-CoV-2 infection dynamics in Addis Ababa and Jimma, Ethiopia, focusing on reinfection, immunity, and vaccination effects. We conducted an antibody serology study spanning August 2020 to July 2022 with five rounds of data collection across a population of 4723, sequenced PCR-test positive samples, used available test positivity rates, and constructed two mathematical models integrating this data. A multivariant model explores variant dynamics identifying wildtype, alpha, delta, and omicron BA.4/5 as key variants in the study population, and cross-immunity between variants, revealing risk reductions between 24% and 69%. An antibody-level model predicts slow decay leading to sustained high antibody levels. Retrospectively, increased early vaccination might have substantially reduced infections during the delta and omicron waves in the considered group of individuals, though further vaccination now seems less impactful.

Gut microbial features may influence antiviral IgG levels after vaccination against viral respiratory infectious diseases: the evidence from two-sample bidirectional mendelian randomization

BACKGROUND

Vaccination is effective in preventing viral respiratory infectious diseases through protective antibodies and the gut microbiome has been proven to regulate human immunity. This study explores the causal correlations between gut microbial features and serum-specific antiviral immunoglobulin G (IgG) levels.

METHODS

We conduct a two-sample bidirectional Mendelian randomization (MR) analysis using genome-wide association study (GWAS) summary data to explore the causal relationships between 412 gut microbial features and four antiviral IgG (for influenza A, measles, rubella, and mumps) levels. To make the results more reliable, we used four robust methods and performed comprehensive sensitivity analyses.

RESULTS

The MR analyses revealed 26, 13, 20, and 18 causal associations of the gut microbial features influencing four IgG levels separately. ​Interestingly, ten microbial features, like genus Collinsella, species Bifidobacterium longum, and the biosynthesis of L-alanine have shown the capacity to regulate multiple IgG levels with consistent direction (rise or fall). The ​reverse MR analysis suggested several potential causal associations of IgG levels affecting microbial features.

CONCLUSIONS

The human immune response against viral respiratory infectious diseases could be modulated by changing the abundance of gut microbes, which provided new approaches for the intervention of viral respiratory infections.

Mucosal immunization with a low-energy electron inactivated respiratory syncytial virus vaccine protects mice without Th2 immune bias

The respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections associated with numerous hospitalizations. Recently, intramuscular (i.m.) vaccines against RSV have been approved for elderly and pregnant women. Noninvasive mucosal vaccination, e.g., by inhalation, offers an alternative against respiratory pathogens like RSV. Effective mucosal vaccines induce local immune responses, potentially resulting in the efficient and fast elimination of respiratory viruses after natural infection. To investigate this immune response to an RSV challenge, low-energy electron inactivated RSV (LEEI-RSV) was formulated with phosphatidylcholine-liposomes (PC-LEEI-RSV) or 1,2-dioleoyl-3-trimethylammonium-propane and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DD-LEEI-RSV) for vaccination of mice intranasally. As controls, LEEI-RSV and formalin-inactivated-RSV (FI-RSV) were used via i.m. vaccination. The RSV-specific immunogenicity of the different vaccines and their protective efficacy were analyzed. RSV-specific IgA antibodies and a statistically significant reduction in viral load upon challenge were detected in mucosal DD-LEEI-RSV-vaccinated animals. Alhydrogel-adjuvanted LEEI-RSV i.m. showed a Th2-bias with enhanced IgE, eosinophils, and lung histopathology comparable to FI-RSV. These effects were absent when applying the mucosal vaccines highlighting the potential of DD-LEEI-RSV as an RSV vaccine candidate and the improved performance of this mucosal vaccine candidate.

Investigation of the safety and protective efficacy of an attenuated and marker M. bovis-BoHV-1 combined vaccine in bovines

Bovine respiratory disease (BRD) is one of the most common diseases in the cattle industry worldwide; it is caused by multiple bacterial or viral coinfections, of which Mycoplasma bovis (M. bovis) and bovine herpesvirus type 1 (BoHV-1) are the most notable pathogens. Although live vaccines have demonstrated better efficacy against BRD induced by both pathogens, there are no combined live and marker vaccines. Therefore, we developed an attenuated and marker M. bovis-BoHV-1 combined vaccine based on the M. bovis HB150 and BoHV-1 gG-/tk- strain previously constructed in our lab and evaluated in rabbits. This study aimed to further evaluate its safety and protective efficacy in cattle using different antigen ratios. After immunization, all vaccinated cattle had a normal rectal temperature and mental status without respiratory symptoms. CD4+, CD8+, and CD19+ cells significantly increased in immunized cattle and induced higher humoral and cellular immune responses, and the expression of key cytokines such as IL-4, IL-12, TNF-α, and IFN-γ can be promoted after vaccination. The 1.0 × 108 CFU of M. bovis HB150 and 1.0 × 106 TCID50 BoHV-1 gG-/tk- combined strain elicited the most antibodies while significantly increasing IgG and cellular immunity after challenge. In conclusion, the M. bovis HB150 and BoHV-1 gG-/tk- combined strain was clinically safe and protective in calves; the mix of 1.0 × 108 CFU of M. bovis HB150 and 1.0 × 106 TCID50 BoHV-1 gG-/tk- strain was most promising due to its low amount of shedding and highest humoral and cellular immune responses compared with others. This study introduces an M. bovis-BoHV-1 combined vaccine for application in the cattle industry.

Higher and Sustained Cell-Mediated Immune Responses After 3 Doses of mRNA COVID-19 Vaccine in Patients With Inflammatory Bowel Disease on Anti-Tumor Necrosis Factor Therapy

INTRODUCTION

Studies suggest that the generation of durable T-cell immunity following coronavirus disease 2019 (COVID-19) vaccination protects against severe disease. The aim of this study was to measure cell-mediated immune response (CMIR) 1-2 months and 6 months after a third dose of a COVID-19 mRNA vaccine.

METHODS

This prospective study (HumoRal and CellULar initial and Sustained immunogenicity in patients with inflammatory bowel disease [IBD]) evaluated CMIR at 28-65 days (t 1 ) after dose 2, 28-65 days (t 2 ) (n = 183) and 6 months (±45 days) (t 3 ) (n = 167) after a third dose of an mRNA COVID-19 vaccine. A small cohort had blood sample available 28-65 days (t 4 ) (n = 55) after a fourth dose. Primary outcomes were CMIR at (t 2 ) and (t 3 ). Secondary outcomes included the effect of immunosuppressing IBD medications on CMIR and response at (t 4 ).

RESULTS

All patients had measurable CMIR at all time points. CMIR increased at t 2 compared with that at t 1 (median 1,467 responding cells per million (interquartile range [IQR] 410-5,971) vs 313 (94-960) P < 0.001). There was no significant waning in t 2 vs t 3 or significant boosting at t 4 . Those on anti-tumor necrosis factor monotherapy had a higher CMIR compared with those not on this therapy at t 2 (4,132 [IQR 1,136-8,795] vs 869 [IQR 343-3,221] P < 0.001) and t 3 (2,843 [IQR 596-6,459] vs 654 [IQR 143-2,067] P < 0.001). In univariable analysis, anti-tumor necrosis factor monotherapy was associated with a higher CMIR at t 2 ( P < 0.001) and t 3 ( P < 0.001) and confirmed in a multivariable model ( P < 0.001).

DISCUSSION

A third dose of a COVID-19 vaccine boosts CMIR, and the response is sustained in patients with IBD.

Oral administration of PEDV-dissolved Alg-CS gel induces high and sustained mucosal immunity in mice

Porcine epidemic diarrhea (PED) is a serious disease in piglets that leads to high mortality. An effective measure that provides higher IgA levels in the intestine and milk is required to decrease losses. Porcine epidemic diarrhea virus (PEDV) was dissolved in calcium alginate (Alg) and combined with chitosan (CS) via electrostatic interactions between cationic chitosan and anionic alginate to create a porous gel (Alg-CS+PEDV). The gel was used to immunize mice orally or in combination with subcutaneous injections of inactivated PEDV vaccine. At 12 and 24 days after immunization, levels of IgA and IgG in Alg-CS+PEDV were higher than with normal PEDV oral administration. At 24 days after immunization, the concentration of IFN-γ in Alg-CS+PEDV was higher than with normal PEDV oral administration. Furthermore, oral administration combining subcutaneous immunization induced higher levels of IgG and IgA than oral administration alone. Our study provides a new method for the preparation and administration of oral vaccines to achieve enhanced mucosal immunity against PEDV.

Design and characterization of protective pan-ebolavirus and pan-filovirus bispecific antibodies

Monoclonal antibodies (mAbs) are an important class of antiviral therapeutics. MAbs are highly selective, well tolerated, and have long in vivo half-life as well as the capacity to induce immune-mediated virus clearance. Their activities can be further enhanced by integration of their variable fragments (Fvs) into bispecific antibodies (bsAbs), affording simultaneous targeting of multiple epitopes to improve potency and breadth and/or to mitigate against viral escape by a single mutation. Here, we explore a bsAb strategy for generation of pan-ebolavirus and pan-filovirus immunotherapeutics. Filoviruses, including Ebola virus (EBOV), Sudan virus (SUDV), and Marburg virus (MARV), cause severe hemorrhagic fever. Although there are two FDA-approved mAb therapies for EBOV infection, these do not extend to other filoviruses. Here, we combine Fvs from broad ebolavirus mAbs to generate novel pan-ebolavirus bsAbs that are potently neutralizing, confer protection in mice, and are resistant to viral escape. Moreover, we combine Fvs from pan-ebolavirus mAbs with those of protective MARV mAbs to generate pan-filovirus protective bsAbs. These results provide guidelines for broad antiviral bsAb design and generate new immunotherapeutic candidates.

Cell-engineered virus-mimetic nanovesicles for vaccination against enveloped viruses

Enveloped viruses pose a significant threat to human health, as evidenced by the recent COVID-19 pandemic. Although current vaccine strategies have proven effective in preventing viral infections, the development of innovative vaccine technologies is crucial to fortify our defences against future pandemics. In this study, we introduce a novel platform called cell-engineered virus-mimetic nanovesicles (VNVs) and demonstrate their potential as a vaccine for targeting enveloped viruses. VNVs are generated by extruding plasma membrane-derived blebs through nanoscale membrane filters. These VNVs closely resemble enveloped viruses and extracellular vesicles (EVs) in size and morphology, being densely packed with plasma membrane contents and devoid of materials from other membranous organelles. Due to these properties, VNVs express viral membrane antigens more extensively and homogeneously than EVs expressing the same antigen. In this study, we produced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) VNVs expressing the SARS-CoV-2 Spike glycoprotein (S) on their surfaces and assessed their preclinical efficacy as a COVID-19 vaccine in experimental animals. The administration of VNVs successfully stimulated the production of S-specific antibodies both systemically and locally, and immune cells isolated from vaccinated mice displayed cytokine responses to S stimulation.

CovEpiAb: a comprehensive database and analysis resource for immune epitopes and antibodies of human coronaviruses

Coronaviruses have threatened humans repeatedly, especially COVID-19 caused by SARS-CoV-2, which has posed a substantial threat to global public health. SARS-CoV-2 continuously evolves through random mutation, resulting in a significant decrease in the efficacy of existing vaccines and neutralizing antibody drugs. It is critical to assess immune escape caused by viral mutations and develop broad-spectrum vaccines and neutralizing antibodies targeting conserved epitopes. Thus, we constructed CovEpiAb, a comprehensive database and analysis resource of human coronavirus (HCoVs) immune epitopes and antibodies. CovEpiAb contains information on over 60 000 experimentally validated epitopes and over 12 000 antibodies for HCoVs and SARS-CoV-2 variants. The database is unique in (1) classifying and annotating cross-reactive epitopes from different viruses and variants; (2) providing molecular and experimental interaction profiles of antibodies, including structure-based binding sites and around 70 000 data on binding affinity and neutralizing activity; (3) providing virological characteristics of current and past circulating SARS-CoV-2 variants and in vitro activity of various therapeutics; and (4) offering site-level annotations of key functional features, including antibody binding, immunological epitopes, SARS-CoV-2 mutations and conservation across HCoVs. In addition, we developed an integrated pipeline for epitope prediction named COVEP, which is available from the webpage of CovEpiAb. CovEpiAb is freely accessible at https://pgx.zju.edu.cn/covepiab/.

Prototype and BA.5 protein nanoparticle vaccines protect against Omicron BA.5 variant in Syrian hamsters

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants with greater transmissibility or immune evasion properties has jeopardized the existing vaccine and antibody-based countermeasures. Here, we evaluated the efficacy of boosting pre-immune hamsters with protein nanoparticle vaccines (Novavax, Inc.) containing recombinant Prototype (Wuhan-1) or BA.5 S proteins against a challenge with the Omicron BA.5 variant of SARS-CoV-2. Serum antibody binding and neutralization titers were quantified before challenge, and viral loads were measured 3 days after challenge. Boosting with Prototype or BA.5 vaccine induced similar antibody binding responses against ancestral Wuhan-1 or BA.5 S proteins, and neutralizing activity of Omicron BA.1 and BA.5 variants. One and three months after vaccine boosting, hamsters were challenged with the Omicron BA.5 variant. Prototype and BA.5 vaccine-boosted hamsters had reduced viral infection in the nasal washes, nasal turbinates, and lungs compared to unvaccinated animals. Although no significant differences in virus load were detected between the Prototype and BA.5 vaccine-boosted animals, fewer breakthrough infections were detected in the BA.5-vaccinated hamsters. Thus, immunity induced by Prototype or BA.5 S protein nanoparticle vaccine boosting can protect against the Omicron BA.5 variant in the Syrian hamster model.

IMPORTANCE

As SARS-CoV-2 continues to evolve, there may be a need to update the vaccines to match the newly emerging variants. Here, we compared the protective efficacy of the updated BA.5 and the original Wuhan-1 COVID-19 vaccine against a challenge with the BA.5 Omicron variant of SARS-CoV-2 in hamsters. Both vaccines induced similar levels of neutralizing antibodies against multiple variants of SARS-CoV-2. One and three months after the final immunization, hamsters were challenged with BA.5. No differences in protection against the BA.5 variant virus were observed between the two vaccines, although fewer breakthrough infections were detected in the BA.5-vaccinated hamsters. Together, our data show that both protein nanoparticle vaccines are effective against the BA.5 variant of SARS-CoV-2 but given the increased number of breakthrough infections and continued evolution, it is important to update the COVID-19 vaccine for long-term protection.

Outpatient COVID-19 convalescent plasma recipient antibody thresholds correlated to reduced hospitalizations within a randomized trial

BACKGROUNDCOVID-19 convalescent plasma (CCP) virus-specific antibody levels that translate into recipient posttransfusion antibody levels sufficient to prevent disease progression are not defined.METHODSThis secondary analysis correlated donor and recipient antibody levels to hospitalization risk among unvaccinated, seronegative CCP recipients within the outpatient, double-blind, randomized clinical trial that compared CCP to control plasma. The majority of COVID-19 CCP arm hospitalizations (15/17, 88%) occurred in this unvaccinated, seronegative subgroup. A functional cutoff to delineate recipient high versus low posttransfusion antibody levels was established by 2 methods: (i) analyzing virus neutralization-equivalent anti-Spike receptor-binding domain immunoglobulin G (anti-S-RBD IgG) responses in donors or (ii) receiver operating characteristic (ROC) curve analysis.RESULTSSARS-CoV-2 anti-S-RBD IgG antibody was volume diluted 21.3-fold into posttransfusion seronegative recipients from matched donor units. Virus-specific antibody delivered was approximately 1.2 mg. The high-antibody recipients transfused early (symptom onset within 5 days) had no hospitalizations. A CCP-recipient analysis for antibody thresholds correlated to reduced hospitalizations found a statistical significant association between early transfusion and high antibodies versus all other CCP recipients (or control plasma), with antibody cutoffs established by both methods-donor-based virus neutralization cutoffs in posttransfusion recipients (0/85 [0%] versus 15/276 [5.6%]; P = 0.03) or ROC-based cutoff (0/94 [0%] versus 15/267 [5.4%]; P = 0.01).CONCLUSIONIn unvaccinated, seronegative CCP recipients, early transfusion of plasma units in the upper 30% of study donors' antibody levels reduced outpatient hospitalizations. High antibody level plasma units, given early, should be reserved for therapeutic use.TRIAL REGISTRATIONClinicalTrials.gov NCT04373460.FUNDINGDepartment of Defense (W911QY2090012); Defense Health Agency; Bloomberg Philanthropies; the State of Maryland; NIH (3R01AI152078-01S1, U24TR001609-S3, 1K23HL151826NIH); the Mental Wellness Foundation; the Moriah Fund; Octapharma; the Healthnetwork Foundation; the Shear Family Foundation; the NorthShore Research Institute; and the Rice Foundation.

Differential interferon responses to influenza A and B viruses in primary ferret respiratory epithelial cells

Influenza B viruses (IBV) cocirculate with influenza A viruses (IAV) and cause periodic epidemics of disease, yet antibody and cellular responses following IBV infection are less well understood. Using the ferret model for antisera generation for influenza surveillance purposes, IAV resulted in robust antibody responses following infection, whereas IBV required an additional booster dose, over 85% of the time, to generate equivalent antibody titers. In this study, we utilized primary differentiated ferret nasal epithelial cells (FNECs) which were inoculated with IAV and IBV to study differences in innate immune responses which may result in differences in adaptive immune responses in the host. FNECs were inoculated with IAV (H1N1pdm09 and H3N2 subtypes) or IBV (B/Victoria and B/Yamagata lineages) and assessed for 72 h. Cells were analyzed for gene expression by quantitative real-time PCR, and apical and basolateral supernatants were assessed for virus kinetics and interferon (IFN), respectively. Similar virus kinetics were observed with IAV and IBV in FNECs. A comparison of gene expression and protein secretion profiles demonstrated that IBV-inoculated FNEC expressed delayed type-I/II IFN responses and reduced type-III IFN secretion compared to IAV-inoculated cells. Concurrently, gene expression of Thymic Stromal Lymphopoietin (TSLP), a type-III IFN-induced gene that enhances adaptive immune responses, was significantly downregulated in IBV-inoculated FNECs. Significant differences in other proinflammatory and adaptive genes were suppressed and delayed following IBV inoculation. Following IBV infection, ex vivo cell cultures derived from the ferret upper respiratory tract exhibited reduced and delayed innate responses which may contribute to reduced antibody responses in vivo.IMPORTANCEInfluenza B viruses (IBV) represent nearly one-quarter of all human influenza cases and are responsible for significant clinical and socioeconomic impacts but do not pose the same pandemic risks as influenza A viruses (IAV) and have thus received much less attention. IBV accounts for greater severity and deaths in children, and vaccine efficacy remains low. The ferret can be readily infected with human clinical isolates and demonstrates a similar course of disease and immune responses. IBV, however, generates lower antibodies in ferrets than IAV following the challenge. To determine whether differences in initial innate responses following infection may affect the development of robust adaptive immune responses, ferret respiratory tract cells were isolated, infected with IAV/IBV, and compared. Understanding the differences in the initial innate immune responses to IAV and IBV may be important in the development of more effective vaccines and interventions to generate more robust protective immune responses.

SARS-CoV-2 spike-FLIPr fusion protein plus lipidated FLIPr protects against various SARS-CoV-2 variants in hamsters

Vaccine-induced mucosal immunity and broad protective capacity against various severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants remain inadequate. Formyl peptide receptor-like 1 inhibitory protein (FLIPr), produced by Staphylococcus aureus, can bind to various Fcγ receptor subclasses. Recombinant lipidated FLIPr (rLF) was previously found to be an effective adjuvant. In this study, we developed a vaccine candidate, the recombinant Delta SARS-CoV-2 spike (rDS)-FLIPr fusion protein (rDS-F), which employs the property of FLIPr binding to various Fcγ receptors. Our study shows that rDS-F plus rLF promotes rDS capture by dendritic cells. Intranasal vaccination of mice with rDS-F plus rLF increases persistent systemic and mucosal antibody responses and CD4/CD8 T-cell responses. Importantly, antibodies induced by rDS-F plus rLF vaccination neutralize Delta, Wuhan, Alpha, Beta, and Omicron strains. Additionally, rDS-F plus rLF provides protective effects against various SARS-CoV-2 variants in hamsters by reducing inflammation and viral loads in the lung. Therefore, rDS-F plus rLF is a potential vaccine candidate to induce broad protective responses against various SARS-CoV-2 variants.IMPORTANCEMucosal immunity is vital for combating pathogens, especially in the context of respiratory diseases like COVID-19. Despite this, most approved vaccines are administered via injection, providing systemic but limited mucosal protection. Developing vaccines that stimulate both mucosal and systemic immunity to address future coronavirus mutations is a growing trend. However, eliciting strong mucosal immune responses without adjuvants remains a challenge. In our study, we have demonstrated that using a recombinant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike-formyl peptide receptor-like 1 inhibitory protein (FLIPr) fusion protein as an antigen, in combination with recombinant lipidated FLIPr as an effective adjuvant, induced simultaneous systemic and mucosal immune responses through intranasal immunization in mice and hamster models. This approach offered protection against various SARS-CoV-2 strains, making it a promising vaccine candidate for broad protection. This finding is pivotal for future broad-spectrum vaccine development.

The lipid globotriaosylceramide promotes germinal center B cell responses and antiviral immunity

Influenza viruses escape immunity owing to rapid antigenic evolution, which requires vaccination strategies that allow for broadly protective antibody responses. We found that the lipid globotriaosylceramide (Gb3) expressed on germinal center (GC) B cells is essential for the production of high-affinity antibodies. Mechanistically, Gb3 bound and disengaged CD19 from its chaperone CD81, permitting CD19 to translocate to the B cell receptor complex to trigger signaling. Moreover, Gb3 regulated major histocompatibility complex class II expression to increase diversity of T follicular helper and GC B cells reactive with subdominant epitopes. In influenza infection, elevating Gb3, either endogenously or exogenously, promoted broadly reactive antibody responses and cross-protection. These data demonstrate that Gb3 determines the affinity and breadth of B cell immunity and has potential as a vaccine adjuvant.

VP1 codon deoptimization and high-fidelity substitutions in 3D polymerase as potential vaccine strategies for eliciting immune responses against enterovirus A71

Enterovirus A71 (EV-A71) can induce severe neurological complications and even fatal encephalitis in children, and it has caused several large outbreaks in Taiwan since 1998. We previously generated VP1 codon-deoptimized (VP1-CD) reverse genetics (rg) EV-A71 viruses (rgEV-A71s) that harbor a high-fidelity (HF) 3D polymerase. These VP1-CD-HF rgEV-A71s showed lower replication kinetics in vitro and decreased virulence in an Institute of Cancer Research (ICR) mouse model of EV-A71 infection, while still retaining their antigenicity in comparison to the wild-type virus. In this study, we aimed to further investigate the humoral and cellular immune responses elicited by VP1-CD-HF rgEV-A71s to assess the potential efficacy of these EV-A71 vaccine candidates. Following intraperitoneal (i.p.) injection of VP1-CD-HF rgEV-A71s in mice, we observed a robust induction of EV-A71-specific neutralizing IgG antibodies in the antisera after 21 days. Splenocytes isolated from VP1-CD-HF rgEV-A71s-immunized mice exhibited enhanced proliferative activities and cytokine production (IL-2, IFN-γ, IL-4, IL-6, and TNF-α) upon re-stimulation with VP1-CD-HF rgEV-A71, as compared to control mice treated with adjuvant only. Importantly, administration of antisera from VP1-CD-HF rgEV-A71s-immunized mice protected against lethal EV-A71 challenge in neonatal mice. These findings highlight that our generated VP1-CD-HF rgEV-A71 viruses are capable of inducing both cellular and humoral immune responses, supporting their potential as next-generation EV-A71 vaccines for combating EV-A71 infection.IMPORTANCEEV-A71 can cause severe neurological diseases and cause death in young children. Here, we report the development of synthetic rgEV-A71s with the combination of codon deoptimization and high-fidelity (HF) substitutions that generate genetically stable reverse genetics (rg) viruses as potential attenuated vaccine candidates. Our work provides insight into the development of low-virulence candidate vaccines through a series of viral genetic editing for maintaining antigenicity and genome stability and suggests a strategy for the development of an innovative next-generation vaccine against EV-A71.

Repeated Omicron exposures override ancestral SARS-CoV-2 immune imprinting

The continuing emergence of SARS-CoV-2 variants highlights the need to update COVID-19 vaccine compositions. However, immune imprinting induced by vaccination based on the ancestral (hereafter referred to as WT) strain would compromise the antibody response to Omicron-based boosters1-5. Vaccination strategies to counter immune imprinting are critically needed. Here we investigated the degree and dynamics of immune imprinting in mouse models and human cohorts, especially focusing on the role of repeated Omicron stimulation. In mice, the efficacy of single Omicron boosting is heavily limited when using variants that are antigenically distinct from WT-such as the XBB variant-and this concerning situation could be mitigated by a second Omicron booster. Similarly, in humans, repeated Omicron infections could alleviate WT vaccination-induced immune imprinting and generate broad neutralization responses in both plasma and nasal mucosa. Notably, deep mutational scanning-based epitope characterization of 781 receptor-binding domain (RBD)-targeting monoclonal antibodies isolated from repeated Omicron infection revealed that double Omicron exposure could induce a large proportion of matured Omicron-specific antibodies that have distinct RBD epitopes to WT-induced antibodies. Consequently, immune imprinting was largely mitigated, and the bias towards non-neutralizing epitopes observed in single Omicron exposures was restored. On the basis of the deep mutational scanning profiles, we identified evolution hotspots of XBB.1.5 RBD and demonstrated that these mutations could further boost the immune-evasion capability of XBB.1.5 while maintaining high ACE2-binding affinity. Our findings suggest that the WT component should be abandoned when updating COVID-19 vaccines, and individuals without prior Omicron exposure should receive two updated vaccine boosters.

Anti-neuraminidase immunity in the combat against influenza

INTRODUCTION

Anti-neuraminidase (NA) immunity correlates with the protection against influenza virus infection in both human and animal models. The aim of this review is to better understand the mechanism of anti-NA immunity, and also to evaluate the approaches on developing NA-based influenza vaccines or enhancing immune responses against NA for current influenza vaccines.

AREAS COVERED

In this review, the structure of influenza neuraminidase, the contribution of anti-NA immunity to protection, as well as the efforts and challenges of targeting the immune responses to NA were discussed. We also listed some of the newly discovered anti-NA monoclonal antibodies and discussed their contribution in therapeutic as well as the antigen design of a broadly protective NA vaccine.

EXPERT OPINION

Targeting the immune response to both HA and NA may be critical for achieving the optimal protection since there are different mechanisms of HA and NA elicited protective immunity. Monoclonal antibodies (mAbs) that target the conserved protective lateral face or catalytic sites are effective therapeutics. The epitope discovery using monoclonal antibodies may benefit NA-based vaccine elicited broadly reactive antibody responses. Therefore, the potential for a vaccine that elicits cross-reactive antibodies against neuraminidase is a high priority for next-generation influenza vaccines.

Cryptic-site-specific antibodies to the SARS-CoV-2 receptor binding domain can retain functional binding affinity to spike variants

IMPORTANCE

Multiple SARS-CoV-2 variants of concern have emerged and caused a significant number of infections and deaths worldwide. These variants of concern contain mutations that might significantly affect antigen-targeting by antibodies. It is therefore important to further understand how antibody binding and neutralization are affected by the mutations in SARS-CoV-2 variants. We highlighted how antibody epitope specificity can influence antibody binding to SARS-CoV-2 spike protein variants and neutralization of SARS-CoV-2 variants. We showed that weakened spike binding and neutralization of Beta (B.1.351) and Omicron (BA.1) variants compared to wildtype are not universal among the panel of antibodies and identified antibodies of a specific binding footprint exhibiting consistent enhancement of spike binding and retained neutralization to Beta variant. These data and analysis can inform how antigen-targeting by antibodies might evolve during a pandemic and prepare for potential future sarbecovirus outbreaks.

An ACE2-Based Bimodular Fusion Protein Enables Reorientation of Endogenous Anti-Epstein-Barr Virus Antibodies Toward SARS-CoV-2 Spike

The use of soluble recombinant angiotensin-converting enzyme 2 (rACE2) as a decoy capable of blocking SARS-CoV-2 entry into cells has been envisaged as a therapeutic strategy to reduce viral loads in patients with severe COVID-19. We engineered a novel form of rACE2, fused to the Epstein-Barr virus antigen P18F3 (rACE2-P18F3), to reorient a preexisting humoral response toward Epstein-Barr virus against SARS-CoV-2 particles. Recombinant ACE2-P18F3 was able to bind to the SARS-CoV-2 spike protein, neutralize viral entry into cells, and promote the phagocytosis of spheres coated with different spike variants by monocytic cells. The results position rACE2-P18F3 as a promising therapeutic candidate to universally block coronavirus cell entry and clear viral particles.

Mapping immunological and host receptor binding determinants of SARS-CoV spike protein utilizing the Qubevirus platform

The motifs involved in tropism and immunological interactions of SARS-CoV spike (S) protein were investigated utilizing the Qubevirus platform. We showed that separately, 14 overlapping peptide fragments representing the S protein (F1-14 of 100 residues each) could be inserted into the C terminus of A1 on recombinant Qubevirus without affecting its viability. Additionally, recombinant phage expression resulted in the surface exposure of different engineered fragments in an accessible manner. The F6 from S425-525 was found to contain the binding determinant of the recombinant human angiotensin-converting enzyme 2, with the shortest active binding motif situated between residues S437-492. Upstream, another fragment, F7, containing an overlapping portion of F6 would not bind to recombinant human angiotensin-converting enzyme 2, confirming that a contiguous stretch of residues could adopt the appropriate structural orientation of F6 as an insertion within the Qubevirus. The F6 (S441-460) and other inserts, including F7/F8 (S601-620) and F10 (S781-800), were demonstrated to contain important immunological determinants through recognition and binding of S protein specific (anti-S) antibodies. An engineered chimeric insert bearing the fusion of all three anti-S reactive epitopes improved substantially the recognition and binding to their cognate antibodies. These results provide insights into humoral immune relevant epitopes and tropism characteristics of the S protein with implications for the development of subunit vaccines or other biologics against SARS-CoV.

Antigenicity and receptor affinity of SARS-CoV-2 BA.2.86 spike

A severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron subvariant, BA.2.86, has emerged and spread to numerous countries worldwide, raising alarm because its spike protein contains 34 additional mutations compared with its BA.2 predecessor1. We examined its antigenicity using human sera and monoclonal antibodies (mAbs). Reassuringly, BA.2.86 was no more resistant to human sera than the currently dominant XBB.1.5 and EG.5.1, indicating that the new subvariant would not have a growth advantage in this regard. Importantly, sera from people who had XBB breakthrough infection exhibited robust neutralizing activity against all viruses tested, suggesting that upcoming XBB.1.5 monovalent vaccines could confer added protection. Although BA.2.86 showed greater resistance to mAbs to subdomain 1 (SD1) and receptor-binding domain (RBD) class 2 and 3 epitopes, it was more sensitive to mAbs to class 1 and 4/1 epitopes in the 'inner face' of the RBD that is exposed only when this domain is in the 'up' position. We also identified six new spike mutations that mediate antibody resistance, including E554K that threatens SD1 mAbs in clinical development. The BA.2.86 spike also had a remarkably high receptor affinity. The ultimate trajectory of this new SARS-CoV-2 variant will soon be revealed by continuing surveillance, but its worldwide spread is worrisome.

Inhaled SARS-CoV-2 vaccine for single-dose dry powder aerosol immunization

The COVID-19 pandemic has fostered major advances in vaccination technologies1-4; however, there are urgent needs for vaccines that induce mucosal immune responses and for single-dose, non-invasive administration4-6. Here we develop an inhalable, single-dose, dry powder aerosol SARS-CoV-2 vaccine that induces potent systemic and mucosal immune responses. The vaccine encapsulates assembled nanoparticles comprising proteinaceous cholera toxin B subunits displaying the SARS-CoV-2 RBD antigen within microcapsules of optimal aerodynamic size, and this unique nano-micro coupled structure supports efficient alveoli delivery, sustained antigen release and antigen-presenting cell uptake, which are favourable features for the induction of immune responses. Moreover, this vaccine induces strong production of IgG and IgA, as well as a local T cell response, collectively conferring effective protection against SARS-CoV-2 in mice, hamsters and nonhuman primates. Finally, we also demonstrate a mosaic iteration of the vaccine that co-displays ancestral and Omicron antigens, extending the breadth of antibody response against co-circulating strains and transmission of the Omicron variant. These findings support the use of this inhaled vaccine as a promising multivalent platform for fighting COVID-19 and other respiratory infectious diseases.

Distinguishing features of long COVID identified through immune profiling

Post-acute infection syndromes may develop after acute viral disease1. Infection with SARS-CoV-2 can result in the development of a post-acute infection syndrome known as long COVID. Individuals with long COVID frequently report unremitting fatigue, post-exertional malaise, and a variety of cognitive and autonomic dysfunctions2-4. However, the biological processes that are associated with the development and persistence of these symptoms are unclear. Here 275 individuals with or without long COVID were enrolled in a cross-sectional study that included multidimensional immune phenotyping and unbiased machine learning methods to identify biological features associated with long COVID. Marked differences were noted in circulating myeloid and lymphocyte populations relative to the matched controls, as well as evidence of exaggerated humoral responses directed against SARS-CoV-2 among participants with long COVID. Furthermore, higher antibody responses directed against non-SARS-CoV-2 viral pathogens were observed among individuals with long COVID, particularly Epstein-Barr virus. Levels of soluble immune mediators and hormones varied among groups, with cortisol levels being lower among participants with long COVID. Integration of immune phenotyping data into unbiased machine learning models identified the key features that are most strongly associated with long COVID status. Collectively, these findings may help to guide future studies into the pathobiology of long COVID and help with developing relevant biomarkers.

Vaccination with prefusion-stabilized respiratory syncytial virus fusion protein elicits antibodies targeting a membrane-proximal epitope

IMPORTANCE

Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis and pneumonia in infants, infecting all children by age 5. RSV also causes substantial morbidity and mortality in older adults, and a vaccine for older adults based on a prefusion-stabilized form of the viral F glycoprotein was recently approved by the FDA. Here, we investigate a set of antibodies that belong to the same public clonotype and were isolated from individuals vaccinated with a prefusion-stabilized RSV F protein. Our results reveal that these antibodies are highly potent and recognize a previously uncharacterized antigenic site on the prefusion F protein. Vaccination with prefusion RSV F proteins appears to boost the elicitation of these neutralizing antibodies, which are not commonly elicited by natural infection.

Variant-adapted COVID-19 booster vaccines

Current vaccines should be tailored to combat future SARS-CoV-2 variants.

Risk factors and titers of COVID-19 infection in a longitudinal statewide seroepidemiology cohort

BACKGROUND

Virginia is a large state in the USA, yet it remains unclear what percentage of the population has had natural COVID-19 infection and whether risk factors for infection have changed over time.

METHODS

Using a longitudinal cohort, from December 2021-July 2022 we performed follow up serology and a questionnaire on 784 individuals from across Virginia who had previously participated in a statewide COVID-19 seroepidemiology study in 2020. Children were also invited to participate and an additional 62 children also completed the study. Serology was performed using Roche nucleocapsid and spike serological assays.

RESULTS

The majority of participants were white (78.6%), over 50 years old (60.9%), and reported having received COVID-19 vaccine (93.4%). 28.6% had evidence of prior COVID-19 infection (nucleocapsid positive). Reweighted by region, age, and sex to match the Virginia census data, the seroprevalence of nucleocapsid antibodies was estimated to be 30.6% (95% CI: 24.7, 36.6). We estimated that 25-53% of COVID-19 infections were asymptomatic. Infection rates were lower in individuals > 60 years old and were higher in Blacks and Hispanics. Infection rates were also higher in those without health insurance, in those with greater numbers of household children, and in those that reported a close contact or having undergone quarantine for COVID-19. Participants from Southwest Virginia had lower seropositivity (16.2%, 95% CI 6.5, 26.0) than other geographic regions. Boosted vaccinees had lower infection rates than non-boosted vaccinees. Frequenting indoor bars was a risk factor for infection, while frequently wearing an N95 mask was protective, though the estimates of association were imprecise. Infection rates were higher in children than adults (56.5% vs. 28.6%). Infection in the parent was a risk factor for child infection. Spike antibody levels declined with time since last vaccination, particularly in those that were vaccinated but not previously infected. Neutralizing antibody positivity was high (97-99%) for wild type, alpha, beta, gamma, delta, and omicron variants. Neutralizing antibody levels were higher in the follow-up survey compared to the first survey in 2020 and among individuals with evidence of natural infection compared to those without.

CONCLUSIONS

In this longitudinal statewide cohort we observed a lower-than-expected COVID-19 infection rate as of August 2022. Boosted vaccinees had lower infection rates. Children had higher infection rates and infections tracked within households. Previously identified demographic risk factors for infection tended to persist. Even after the omicron peak, a large number of Virginians remain uninfected with COVID-19, underscoring the need for ongoing vaccination strategies.

Mapping SARS-CoV-2 antigenic relationships and serological responses

During the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, multiple variants escaping preexisting immunity emerged, causing reinfections of previously exposed individuals. Here, we used antigenic cartography to analyze patterns of cross-reactivity among 21 variants and 15 groups of human sera obtained after primary infection with 10 different variants or after messenger RNA (mRNA)-1273 or mRNA-1273.351 vaccination. We found antigenic differences among pre-Omicron variants caused by substitutions at spike-protein positions 417, 452, 484, and 501. Quantifying changes in response breadth over time and with additional vaccine doses, our results show the largest increase between 4 weeks and >3 months after a second dose. We found changes in immunodominance of different spike regions, depending on the variant an individual was first exposed to, with implications for variant risk assessment and vaccine-strain selection.

Analytical Ultracentrifugation Detects Quaternary Rearrangements and Antibody-Induced Conformational Selection of the SARS-CoV-2 Spike Trimer

Analytical ultracentrifugation (AUC) analysis shows that the SARS-CoV-2 trimeric Spike (S) protein adopts different quaternary conformations in solution. The relative abundance of the "open" and "close" conformations is temperature-dependent, and samples with different storage temperature history have different open/close distributions. Neutralizing antibodies (NAbs) targeting the S receptor binding domain (RBD) do not alter the conformer populations; by contrast, a NAb targeting a cryptic conformational epitope skews the Spike trimer toward an open conformation. The results highlight AUC, which is typically applied for molecular mass determination of biomolecules as a powerful tool for detecting functionally relevant quaternary protein conformations.

A study of fibrinolytic system components in donor groups depending on various titers of circulating anti-SARS-CoV-2 IgG in the bloodstream

The fibrinolytic system plays an important role in controlling blood coagulation at each stage, from thrombin generation to fibrin clot cleavage. Currently, long-term multiorgan dysfunction post-coronavirus disease 2019 (COVID-19) may include coagulation disorders. Little information is available about the potential causes of post-COVID-19 coagulopathy, but one of them may be subpopulation IgG produced by the immune system against SARS-CoV-2. This article describes the changes in the main parameters of the fibrinolytic system in donors with various titers of anti-SARS-CoV-2 IgG, which is part of a complex study of the hemostasis system in these donor groups. We determined the most significant parameters of the fibrinolytic system, such as potential activity and amount of plasminogen and tissue plasminogen activator (tPA), amount of plasminogen activator inhibitor-1 (PAI-1), inhibitory potentials of α-2-antiplasmin, α-1-antitrypsin, α-2-macroglobulin in the blood plasma of donor groups. The obtained results represent the maximum and minimum values of measurement parameters among donor groups with titers of anti-SARS-CoV-2 IgG at least 10 ± 3 Index (S/C), and their statistical differences from the reference point [donor group with titer of anti-SARS-CoV-2 IgG 0 Index (S/C)]. We established the changes in fibrinolytic parameters depending on the titers of anti-SARS-CoV-2 IgG. One conclusion can be drawn from this: anti-SARS-CoV-2 IgG population may influence coagulation in the post-COVID-19 period. Further research in-vitro and in-vivo experimental models using selected and purified IgG may confirm our previous findings.

SARS-CoV-2 Infection and Development of Islet Autoimmunity in Early Childhood

Importance

The incidence of diabetes in childhood has increased during the COVID-19 pandemic. Elucidating whether SARS-CoV-2 infection is associated with islet autoimmunity, which precedes type 1 diabetes onset, is relevant to disease etiology and future childhood diabetes trends.

Objective

To determine whether there is a temporal relationship between SARS-CoV-2 infection and the development of islet autoimmunity in early childhood.

Design, Setting, and Participants

Between February 2018 and March 2021, the Primary Oral Insulin Trial, a European multicenter study, enrolled 1050 infants (517 girls) aged 4 to 7 months with a more than 10% genetically defined risk of type 1 diabetes. Children were followed up through September 2022.

Exposure

SARS-CoV-2 infection identified by SARS-CoV-2 antibody development in follow-up visits conducted at 2- to 6-month intervals until age 2 years from April 2018 through June 2022.

Main Outcomes and Measures

The development of multiple (≥2) islet autoantibodies in follow-up in consecutive samples or single islet antibodies and type 1 diabetes. Antibody incidence rates and risk of developing islet autoantibodies were analyzed.

Results

Consent was obtained for 885 (441 girls) children who were included in follow-up antibody measurements from age 6 months. SARS-CoV-2 antibodies developed in 170 children at a median age of 18 months (range, 6-25 months). Islet autoantibodies developed in 60 children. Six of these children tested positive for islet autoantibodies at the same time as they tested positive for SARS-CoV-2 antibodies and 6 at the visit after having tested positive for SARS-CoV-2 antibodies. The sex-, age-, and country-adjusted hazard ratio for developing islet autoantibodies when the children tested positive for SARS-CoV-2 antibodies was 3.5 (95% CI, 1.6-7.7; P = .002). The incidence rate of islet autoantibodies was 3.5 (95% CI, 2.2-5.1) per 100 person-years in children without SARS-CoV-2 antibodies and 7.8 (95% CI, 5.3-19.0) per 100 person-years in children with SARS-CoV-2 antibodies (P = .02). Islet autoantibody risk in children with SARS-CoV-2 antibodies was associated with younger age (<18 months) of SARS-CoV-2 antibody development (HR, 5.3; 95% CI, 1.5-18.3; P = .009).

Conclusion and relevance

In young children with high genetic risk of type 1 diabetes, SARS-CoV-2 infection was temporally associated with the development of islet autoantibodies.

Study of efficacy and antibody duration to fourth-dose booster of Ad5-nCoV or inactivated SARS-CoV-2 vaccine in Chinese adults: a prospective cohort study

Introduction

China experienced a record surge of coronavirus disease 2019 cases in December 2022, during the pandemic.

Methods

We conducted a randomized, parallel-controlled prospective cohort study to evaluate efficacy and antibody duration after a fourth-dose booster with Ad5-nCoV or inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine.

Results

A total of 191 participants aged ≥18 years who had completed a three-dose regimen of the inactivated SARS-CoV-2 vaccine 6 months earlier were recruited to receive the intramuscular Ad5-nCoV booster or the inactivated SARS-CoV-2 vaccine. The Ad5-nCoV group had significantly higher antibody levels compared with the inactivated vaccine group at 6 months after the fourth vaccination dose. After the pandemic, the breakthrough infection rate for the Ad5-nCoV and the inactivated vaccine groups was 77.89% and 78.13%, respectively. Survival curve analysis (p = 0.872) and multivariable logistic regression analysis (p = 0.956) showed no statistically significant differences in breakthrough infection between the two groups.

Discussion

Compared with a homologous fourth dose, a heterologous fourth dose of Ad5-nCoV elicited a higher immunogenic response in healthy adults who had been immunized with three doses of inactivated vaccine. Nevertheless, the efficacy of the two vaccine types was equivalent after the pandemic.

Humoral immunity to an endemic coronavirus is associated with postacute sequelae of COVID-19 in individuals with rheumatic diseases

Beyond the acute illness caused by severe acute respiratory coronavirus 2 (SARS-CoV-2) infection, about one-fifth of infections result in long-term persistence of symptoms despite the apparent clearance of infection. Insights into the mechanisms that underlie postacute sequelae of COVID-19 (PASC) will be critical for the prevention and clinical management of long-term complications of COVID-19. Several hypotheses have been proposed that may account for the development of PASC, including persistence of virus and dysregulation of immune responses. Among the immunological changes noted in PASC, alterations in humoral immunity have been observed in some patient subsets. To begin to determine whether SARS-CoV-2- or other pathogen-specific humoral immune responses evolve uniquely in PASC, we performed comprehensive antibody profiling against SARS-CoV-2, a panel of endemic pathogens, and a panel of routine vaccine antigens using systems serology in two cohorts of patients with preexisting systemic autoimmune rheumatic disease (SARD) who either developed or did not develop PASC. A distinct qualitative shift observed in Fcγ receptor (FcγR) binding was observed in individuals with PASC. Specifically, individuals with PASC harbored weaker FcγR-binding anti-SARS-CoV-2 antibodies and stronger FcγR-binding antibody responses against the endemic coronavirus OC43. Individuals with PASC developed an OC43 S2-specific antibody response with stronger FcγR binding, linked to cross-reactivity across SARS-CoV-2 and common coronaviruses. These findings identify previous coronavirus imprinting as a potential marker for the development of PASC in individuals with SARDs.

Binding and Avidity Signatures of Polyclonal Sera From Individuals With Different Exposure Histories to Severe Acute Respiratory Syndrome Coronavirus 2 Infection, Vaccination, and Omicron Breakthrough Infections

BACKGROUND

The number of exposures to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and to vaccine antigens affect the magnitude and avidity of the polyclonal response.

METHODS

We studied binding and avidity of different antibody isotypes to the spike, the receptor-binding domain (RBD), and the nucleoprotein (NP) of wild-type (WT) and BA.1 SARS-CoV-2 in convalescent, mRNA vaccinated and/or boosted, hybrid immune individuals and in individuals with breakthrough cases during the peak of the BA.1 wave.

RESULTS

We found an increase in spike-binding antibodies and antibody avidity with increasing number of exposures to infection and/or vaccination. NP antibodies were detectible in convalescent individuals and a proportion of breakthrough cases, but they displayed low avidity. Omicron breakthrough infections elicited high levels of cross-reactive antibodies between WT and BA.1 antigens in vaccinated individuals without prior infection directed against the spike and RBD. The magnitude of the antibody response and avidity correlated with neutralizing activity against WT virus.

CONCLUSIONS

The magnitude and quality of the antibody response increased with the number of antigenic exposures, including breakthrough infections. However, cross-reactivity of the antibody response after BA.1 breakthroughs, was affected by the number of prior exposures.

Anti-Epstein-Barr Virus BNLF2b for Mass Screening for Nasopharyngeal Cancer

BACKGROUND

Population screening of asymptomatic persons with Epstein-Barr virus (EBV) DNA or antibodies has improved the diagnosis of nasopharyngeal carcinoma and survival among affected persons. However, the positive predictive value of current screening strategies is unsatisfactory even in areas where nasopharyngeal carcinoma is endemic.

METHODS

We designed a peptide library representing highly ranked B-cell epitopes of EBV coding sequences to identify novel serologic biomarkers for nasopharyngeal carcinoma. After a retrospective case-control study, the performance of the novel biomarker anti-BNLF2b total antibody (P85-Ab) was validated through a large-scale prospective screening program and compared with that of the standard two-antibody-based screening method (EBV nuclear antigen 1 [EBNA1]-IgA and EBV-specific viral capsid antigen [VCA]-IgA).

RESULTS

P85-Ab was the most promising biomarker for nasopharyngeal carcinoma screening, with high sensitivity (94.4%; 95% confidence interval [CI], 86.4 to 97.8) and specificity (99.6%; 95% CI, 97.8 to 99.9) in the retrospective case-control study. Among the 24,852 eligible participants in the prospective cohort, 47 cases of nasopharyngeal carcinoma (38 at an early stage) were identified. P85-Ab showed higher sensitivity than the two-antibody method (97.9% vs. 72.3%; ratio, 1.4 [95% CI, 1.1 to 1.6]), higher specificity (98.3% vs. 97.0%; ratio, 1.01 [95% CI, 1.01 to 1.02]), and a higher positive predictive value (10.0% vs. 4.3%; ratio, 2.3 [95% CI, 1.8 to 2.8]). The combination of P85-Ab and the two-antibody method markedly increased the positive predictive value to 44.6% (95% CI, 33.8 to 55.9), with sensitivity of 70.2% (95% CI, 56.0 to 81.4).

CONCLUSIONS

Our results suggest that P85-Ab is a promising novel biomarker for nasopharyngeal carcinoma screening, with higher sensitivity, specificity, and positive predictive value than the standard two-antibody method. (Funded by the National Key Research and Development Program of China and others; ClinicalTrials.gov number, NCT04085900.).

IgG3 subclass antibodies recognize antigenically drifted influenza viruses and SARS-CoV-2 variants through efficient bivalent binding

The constant domains of antibodies are important for effector functions, but less is known about how they can affect binding and neutralization of viruses. Here, we evaluated a panel of human influenza virus monoclonal antibodies (mAbs) expressed as IgG1, IgG2, or IgG3. We found that many influenza virus-specific mAbs have altered binding and neutralization capacity depending on the IgG subclass encoded and that these differences result from unique bivalency capacities of the subclasses. Importantly, subclass differences in antibody binding and neutralization were greatest when the affinity for the target antigen was reduced through antigenic mismatch. We found that antibodies expressed as IgG3 bound and neutralized antigenically drifted influenza viruses more effectively. We obtained similar results using a panel of SARS-CoV-2-specific mAbs and the antigenically advanced B.1.351 and BA.1 strains of SARS-CoV-2. We found that a licensed therapeutic mAb retained neutralization breadth against SARS-CoV-2 variants when expressed as IgG3, but not IgG1. These data highlight that IgG subclasses are not only important for fine-tuning effector functionality but also for binding and neutralization of antigenically drifted viruses.

Combined Antibodies Evusheld against the SARS-CoV-2 Omicron Variants BA.1.1 and BA.5: Immune Escape Mechanism from Molecular Simulation

The Omicron lineage of SARS-CoV-2, which was first reported in November 2021, has spread globally and become dominant, splitting into several sublineages. Experiments have shown that Omicron lineage has escaped or reduced the activity of existing monoclonal antibodies, but the origin of escape mechanism caused by mutation is still unknown. This work uses molecular dynamics and umbrella sampling methods to reveal the escape mechanism of BA.1.1 to monoclonal antibody (mAb) Tixagevimab (AZD1061) and BA.5 to mAb Cilgavimab (AZD8895), both mAbs were combined to form antibody cocktail, Evusheld (AZD7442). The binding free energy of BA.1.1-AZD1061 and BA.5-AZD8895 has been severely reduced due to multiple-site mutated Omicron variants. Our results show that the two Omicron variants, which introduce a substantial number of positively charged residues, can weaken the electrostatic attraction between the receptor binding domain (RBD) and AZD7442, thus leading to a decrease in affinity. Additionally, using umbrella sampling along dissociation pathway, we found that the two Omicron variants severely impaired the interaction between the RBD of SARS-CoV-2's spike glycoprotein (S protein) and complementary determining regions (CDRs) of mAbs, especially in CDR3H. Although mAbs AZD8895 and AZD1061 are knocked out by BA.5 and BA.1.1, respectively, our results confirm that the antibody cocktail AZD7442 retains activity against BA.1.1 and BA.5 because another antibody is still on guard. The study provides theoretical insights for mAbs interacting with BA.1.1 and BA.5 from both energetic and dynamic perspectives, and we hope this will help in developing new monoclonals and combinations to protect those unable to mount adequate vaccine responses.

Omicron infection following vaccination enhances a broad spectrum of immune responses dependent on infection history

Pronounced immune escape by the SARS-CoV-2 Omicron variant has resulted in many individuals possessing hybrid immunity, generated through a combination of vaccination and infection. Concerns have been raised that omicron breakthrough infections in triple-vaccinated individuals result in poor induction of omicron-specific immunity, and that prior SARS-CoV-2 infection is associated with immune dampening. Taking a broad and comprehensive approach, we characterize mucosal and blood immunity to spike and non-spike antigens following BA.1/BA.2 infections in triple mRNA-vaccinated individuals, with and without prior SARS-CoV-2 infection. We find that most individuals increase BA.1/BA.2/BA.5-specific neutralizing antibodies following infection, but confirm that the magnitude of increase and post-omicron titres are higher in the infection-naive. In contrast, significant increases in nasal responses, including neutralizing activity against BA.5 spike, are seen regardless of infection history. Spike-specific T cells increase only in infection-naive vaccinees; however, post-omicron T cell responses are significantly higher in the previously-infected, who display a maximally induced response with a highly cytotoxic CD8+ phenotype following their 3rd mRNA vaccine dose. Responses to non-spike antigens increase significantly regardless of prior infection status. These findings suggest that hybrid immunity induced by omicron breakthrough infections is characterized by significant immune enhancement that can help protect against future omicron variants.

Despite delayed kinetics, people living with HIV achieve equivalent antibody function after SARS-CoV-2 infection or vaccination

The kinetics of Fc-mediated functions following SARS-CoV-2 infection or vaccination in people living with HIV (PLWH) are not known. We compared SARS-CoV-2 spike-specific Fc functions, binding, and neutralization in PLWH and people without HIV (PWOH) during acute infection (without prior vaccination) with either the D614G or Beta variants of SARS-CoV-2, or vaccination with ChAdOx1 nCoV-19. Antiretroviral treatment (ART)-naïve PLWH had significantly lower levels of IgG binding, neutralization, and antibody-dependent cellular phagocytosis (ADCP) compared with PLWH on ART. The magnitude of antibody-dependent cellular cytotoxicity (ADCC), complement deposition (ADCD), and cellular trogocytosis (ADCT) was differentially triggered by D614G and Beta. The kinetics of spike IgG-binding antibodies, ADCC, and ADCD were similar, irrespective of the infecting variant between PWOH and PLWH overall. However, compared with PWOH, PLWH infected with D614G had delayed neutralization and ADCP. Furthermore, Beta infection resulted in delayed ADCT, regardless of HIV status. Despite these delays, we observed improved coordination between binding and neutralizing responses and Fc functions in PLWH. In contrast to D614G infection, binding responses in PLWH following ChAdOx-1 nCoV-19 vaccination were delayed, while neutralization and ADCP had similar timing of onset, but lower magnitude, and ADCC was significantly higher than in PWOH. Overall, despite delayed and differential kinetics, PLWH on ART develop comparable responses to PWOH, supporting the prioritization of ART rollout and SARS-CoV-2 vaccination in PLWH.

Transplacental transfer of anti-SARS-CoV-2 neutralizing antibodies in comparison to other pathogens total antibodies

BACKGROUNDS

Due to immaturity of their immune system, passive maternal immunization is essential for newborns during their first months of life. Therefore, in the current context of intense circulation of SARS-CoV-2, identifying factors influencing the transfer ratio (TR) of neutralizing antibodies against SARS-CoV-2 (NAb) appears important.

METHODS

Our study nested in the COVIPREG cohort (NCT04355234), included mothers who had a SARS-CoV-2 PCR positive during their pregnancy and their newborns. Maternal and neonatal NAb levels were measured with the automated iFlash system.

RESULTS

For the 173 mother-infant pairs included in our study, the median gestational age (GA) at delivery was 39.4 weeks of gestation (WG), and 29.7 WG at maternal SARS-CoV-2 infection. Using a multivariate logistic model, having a NAb TR above 1 was positively associated with a longer delay from maternal positive SARS-CoV-2 PCR to delivery (aOR 1.09, 95% CI: 1.03 - 1.17) and with a later GA at delivery (aOR = 1.58, 95% CI: 1.09 - 2.52). It was negatively associated with being a male newborn (aOR 0.21, 95% CI: 0.07 - 0.59). In 3rd trimester SARS-CoV-2 infected mothers, NAb TR was inferior to VZV, toxoplasmosis, CMV, measle and rubella's TR. However, in 1st or 2nd trimester infected mothers, only measle TR was different from NAb TR.

CONCLUSION

Male newborn of mothers infected by SARS-CoV-2 during their pregnancy appear to have less protection against SARS-CoV-2 in their first months of life than female newborns. Measle TR was superior to NAb TR even in case of 1st or 2nd trimester maternal SARS-CoV-2 infection. Future studies are needed to investigate possible differences in transmission of NAb following infection vs vaccination and its impact on TR.

A Safe and Efficient Double-Gene-Deleted Live Attenuated Immersion Vaccine to Prevent the Disease Caused by the Infectious Spleen and Kidney Necrosis Virus

Infectious diseases seriously threaten sustainable aquaculture development, resulting in more than $10 billion in economic losses annually. Immersion vaccines are emerging as the key technology for aquatic disease prevention and control. Here, a safe and efficacious candidate immersion vaccine strain (Δorf103r/tk) of infectious spleen and kidney necrosis virus (ISKNV), in which the orf103r and tk genes were knocked out by homologous recombination, is described. Δorf103r/tk was severely attenuated in mandarin fish (Siniperca chuatsi), inducing mild histological lesions, a mortality rate of only 3%, and eliminated within 21 days. A single Δorf103r/tk immersion-administered dose provided long-lasting protection rates over 95% against lethal ISKNV challenge. Δorf103r/tk also robustly stimulated the innate and adaptive immune responses. For example, interferon expression was significantly upregulated, and the production of specific neutralizing antibodies against ISKNV was markedly induced postimmunization. This work provides proof-of-principle evidence for orf103r- and tk-deficient ISKNV for immersion vaccine development to prevent ISKNV disease in aquaculture production. IMPORTANCE Global aquaculture production reached a record of 122.6 million tons in 2020, with a total value of 281.5 billion U.S. dollars (USD). However, approximately 10% of farmed aquatic animal production is lost due to various infectious diseases, resulting in more than 10 billion USD of economic waste every year. Therefore, the development of vaccines to prevent and control aquatic infectious diseases is of great significance. Infectious spleen and kidney necrosis virus (ISKNV) infection occurs in more than 50 species of freshwater and marine fish and has caused great economic losses to the mandarin fish farming industry in China during the past few decades. Thus, it is listed as a certifiable disease by the World Organization for Animal Health (OIE). Herein, a safe and efficient double-gene-deleted live attenuated immersion vaccine against ISKNV was developed, providing an example for the development of aquatic gene-deleted live attenuated immersion vaccine.

Characterization of epitopes of human monoclonal antibodies against cytomegalovirus glycoprotein B for neutralization and antibody-dependent phagocytosis

As congenital cytomegalovirus (CMV) infections are the leading non-genetic cause of sensorineural hearing loss and significant neurological disabilities in children, the development of CMV vaccines should be given the highest public health priority. Although MF59-adjuvanted glycoprotein B (gB) vaccine (gB/MF59) is safe and immunogenic, its efficacy in terms of protection from natural infection was around 50 % in clinical trials. Although gB/MF59 induced high antibody titers, anti-gB antibodies contributed little to the neutralization of infection. Recent studies have found that non-neutralizing functions, including antibody-dependent phagocytosis of virions and virus-infected cells, are likely to play important roles in pathogenesis and vaccine design. Previously, we isolated human monoclonal antibodies (MAbs) that reacted with the trimeric form of gB ectodomain and found that preferential epitopes for neutralization were present on Domains (Doms) I and II of gB, while there were abundant non-neutralizing antibodies targeting Dom IV. In this study, we analyzed the phagocytosis activities of these MAbs and found the following: 1) MAbs effective for phagocytosis of the virions targeted Doms I and II, 2) the MAbs effective for phagocytosis of the virions and those of virus-infected cells were generally distinct, and 3) the antibody-dependent phagocytosis showed little correlation with neutralizing activities. Taking account of the frequency and levels of neutralization and phagocytosis, incorporation of the epitopes on Doms I and II into developing vaccines is considered desirable for the prevention of viremia.

PLSCR1 is a cell-autonomous defence factor against SARS-CoV-2 infection

Understanding protective immunity to COVID-19 facilitates preparedness for future pandemics and combats new SARS-CoV-2 variants emerging in the human population. Neutralizing antibodies have been widely studied; however, on the basis of large-scale exome sequencing of protected versus severely ill patients with COVID-19, local cell-autonomous defence is also crucial1-4. Here we identify phospholipid scramblase 1 (PLSCR1) as a potent cell-autonomous restriction factor against live SARS-CoV-2 infection in parallel genome-wide CRISPR-Cas9 screens of human lung epithelia and hepatocytes before and after stimulation with interferon-γ (IFNγ). IFNγ-induced PLSCR1 not only restricted SARS-CoV-2 USA-WA1/2020, but was also effective against the Delta B.1.617.2 and Omicron BA.1 lineages. Its robust activity extended to other highly pathogenic coronaviruses, was functionally conserved in bats and mice, and interfered with the uptake of SARS-CoV-2 in both the endocytic and the TMPRSS2-dependent fusion routes. Whole-cell 4Pi single-molecule switching nanoscopy together with bipartite nano-reporter assays found that PLSCR1 directly targeted SARS-CoV-2-containing vesicles to prevent spike-mediated fusion and viral escape. A PLSCR1 C-terminal β-barrel domain-but not lipid scramblase activity-was essential for this fusogenic blockade. Our mechanistic studies, together with reports that COVID-associated PLSCR1 mutations are found in some susceptible people3,4, identify an anti-coronavirus protein that interferes at a late entry step before viral RNA is released into the host-cell cytosol.

Identification and Analysis of Monoclonal Antibodies with Neutralizing Activity against Diverse SARS-CoV-2 Variants

We identified neutralizing monoclonal antibodies against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) variants (including Omicron variants BA.5 and BA.2.75) from individuals who received two doses of mRNA vaccination after they had been infected with the D614G virus. We named them MO1, MO2, and MO3. Among them, MO1 showed particularly high neutralizing activity against authentic variants: D614G, Delta, BA.1, BA.1.1, BA.2, BA.2.75, and BA.5. Furthermore, MO1 suppressed BA.5 infection in hamsters. A structural analysis revealed that MO1 binds to the conserved epitope of seven variants, including Omicron variants BA.5 and BA.2.75, in the receptor-binding domain of the spike protein. MO1 targets an epitope conserved among Omicron variants BA.1, BA.2, and BA.5 in a unique binding mode. Our findings confirm that D614G-derived vaccination can induce neutralizing antibodies that recognize the epitopes conserved among the SARS-CoV-2 variants. IMPORTANCE Omicron variants of SARS-CoV-2 acquired escape ability from host immunity and authorized antibody therapeutics and thereby have been spreading worldwide. We reported that patients infected with an early SARS-CoV-2 variant, D614G, and who received subsequent two-dose mRNA vaccination have high neutralizing antibody titer against Omicron lineages. It was speculated that the patients have neutralizing antibodies broadly effective against SARS-CoV-2 variants by targeting common epitopes. Here, we explored human monoclonal antibodies from B cells of the patients. One of the monoclonal antibodies, named MO1, showed high potency against broad SARS-CoV-2 variants including BA.2.75 and BA.5 variants. The results prove that monoclonal antibodies that have common neutralizing epitopes among several Omicrons were produced in patients infected with D614G and who received mRNA vaccination.