Serum Neutralizing Activity Research Articles

Clinical validation of an RSV neutralization assay and analysis of cross-sectional sera associated with 2021-2023 RSV outbreaks to investigate the immunity debt hypothesis.

Population surveillance studies of serum-neutralizing activity against RSV are crucial for evaluating RSV vaccine efficacy and vulnerabilities to new strains. Here, we designed and validated a high-throughput assay for assessing anti-RSV neutralizing activity, standardized its measurements for comparison with other methodologies, and demonstrated its applicability to real-world samples. Our assay is precise, linear, and yields measurements consistent with other standardized assays, offering a methodology useful for large-scale studies of RSV immunity. We also find no significant difference in neutralizing titers among adults between those taken before and after large RSV outbreaks associated with the latter stages of the coronavirus disease of 2019 (COVID-19) public health emergency, underlining the need for a greater understanding of the dynamics of serological responses to RSV infection.

Re-Evaluation and Retrospective Comparison of Serum Neutralization Induced by Three Different Types of Inactivated SARS-CoV-2 Vaccines

Background: During the COVID-19 pandemic, three different types of inactivated SARS-CoV-2 vaccines, namely BBIBP-CorV, WIBP-CorV and CoronaVac, were manufactured and used for vaccination in China. However, as far as we know, no comparison of their induced serum neutralization has been carried out so far, possibly due to the regional difference in vaccine distribution, the difficulty in undertaking a comprehensive evaluation, and the intention to avoid unnecessary bias in populations for a certain type of inactivated vaccine.Methods: Since all three of these inactivated vaccines are no longer produced and used for vaccination, here, we retrospectively compared the serum neutralizing activities induced by these three different types of inactivated SARS-CoV-2 vaccines. Results: Compared with unvaccinated uninfected control donors, primary inactivated vaccination (232 donors) induced increased serum neutralizing titers against wildtype SARS-CoV-2 in around 70% of donors during the first 100 days. However, the neutralization effect waned quickly after 100 days, and significantly diminished against Delta and Omicron (B.1.1.529) variants. Moreover, the newly emerged Omicron variants, such as BA.2.75, BA.4/5, BF.7, BQ.1.1, and XBB, almost fully evaded the induced serum neutralization activity. Conclusions: These three distinct types of inactivated vaccines, namely BBIBP-CorV, WIBP-CorV, and CoronaVac, induced serum neutralization in most vaccinated populations but in a short-term and variant-evaded manner with no significant difference among these inactivated vaccines.

Development of pseudotyped VSV-SARS-CoV-2 spike variants for the assessment of neutralizing antibodies.

Aim: Serological studies with pseudotyped viruses offer a safer alternative to live SARS-CoV-2 in evaluating neutralizing antibodies, enabling research in standard labs.Methods: The SARS-CoV-2 Spike pseudotyped vesicular stomatitis virus (VSV) pseudoviruses were generated using Spike of Wuhan strain and two variants (B.1.1.7, B.1.351) and utilized to evaluate the serum neutralizing activity of human plasma samples of vaccinated (n=13) and healthy people (n=2) compared with a plaque assay with authentic virus.Results: Neutralizing titer of convalescent plasma resulted with a good correlation (R2=0.7).Conclusion: We evaluated a safe and reliable pseudotyped virus system that effectively mimics authentic virus and correlates well with traditional assays. The developed system allows easier testing of variants and has the potential to improve vaccine development.

M protein ectodomain-specific immunity restrains SARS-CoV-2 variants replication.

The frequent occurrence of mutations in the SARS-CoV-2 Spike (S) protein, with up to dozens of mutations, poses a severe threat to the current efficacy of authorized COVID-19 vaccines. Membrane (M) protein, which is the most abundant viral structural protein, exhibits a high level of amino acid sequence conservation. M protein ectodomain could be recognized by specific antibodies; however, the extent to which it is immunogenic and provides protection remains unclear. We designed and synthesized multiple peptides derived from coronavirus M protein ectodomains, and determined the secondary structure of specific peptides using circular dichroism (CD) spectroscopy. Enzyme-linked immunosorbent assay (ELISA) was utilized to detect IgG responses against the synthesized peptides in clinical samples. To evaluate the immunogenicity of peptide vaccines, BALB/c mice were intraperitoneally immunized with peptide-keyhole limpet hemocyanin (KLH) conjugates adjuvanted with incomplete Freund's adjuvant (IFA). The humoral and T-cell immune responses induced by peptide-KLH conjugates were assessed using ELISA and ELISpot assays, respectively. The efficacy of the S2M2-30-KLH vaccine against SARS-CoV-2 variants was evaluated in vivo using the K18-hACE2 transgenic mouse model. The inhibitory effect of mouse immune serum on SARS-CoV-2 virus replication in vitro was evaluated using microneutralization assays. The subcellular localization of the M protein was evaluated using an immunofluorescent staining method, and the Fc-mediated antibody-dependent cellular cytotoxicity (ADCC) activity of the S2M2-30-specific monoclonal antibody (mAb) was measured using an ADCC reporter assay. Seroconversion rates for ectodomain-specific IgG were observed to be high in both SARS-CoV-2 convalescent patients and individuals immunized with inactivated vaccines. To assess the protective efficacy of the M protein ectodomain-based vaccine, we initially identified a highly immunogenic peptide derived from this ectodomain, named S2M2-30. The mouse serum specific to S2M2-30 showed inhibitory effects on the replication of SARS-CoV-2 variants in vitro. Immunizations of K18-hACE2-transgenic mice with the S2M2-30-keyhole limpet hemocyanin (KLH) vaccine significantly reduced the lung viral load caused by B.1.1.7/Alpha (UK) infection. Further mechanism investigations reveal that serum neutralizing activity, specific T-cell response and Fc-mediated antibody-dependent cellular cytotoxicity (ADCC) correlate with the specific immuno-protection conferred by S2M2-30. The findings of this study suggest that the antibody responses against M protein ectodomain in the population most likely exert a beneficial effect on preventing various SARS-CoV-2 infections.

Facile quantitative diagnostic testing for neutralizing antibodies against Chikungunya virus

BackgroundViral neutralization (NT) assays can be used to determine the immune status of patients or assess the potency of candidate vaccines or therapeutic monoclonal antibodies (mAbs). Focus reduction neutralization test (FRNT) is a conventional neutralization test (cVNT) with superior specificity for measurement of neutralizing antibodies against a specific virus. Unfortunately, the application of FRNT to the chikungunya virus (CHIKV) involves a highly pathogenic bio-agent requiring biosafety level 3 (BSL3) facilities, which inevitably imposes high costs and limits accessibility. In this study, we evaluated a safe surrogate virus neutralization test (sVNT) that uses novel CHIKV replicon particles (VRPs) expressing eGFP and luciferase (Luc) to enable the rapid detection and quantification of neutralizing activity in clinical human serum samples.MethodsThis unmatched case-control validation study used serum samples from laboratory-confirmed cases of CHIKV (n = 19), dengue virus (DENV; n = 9), Japanese encephalitis virus (JEV; n = 5), and normal individuals (n = 20). We evaluated the effectiveness of sVNT, based on mosquito cell-derived CHIK VRPs (mos-CHIK VRPs), in detecting (eGFP) and quantifying (Luc) neutralizing activity, considering specificity, sensitivity, and reproducibility. We conducted correlation analysis between the proposed rapid method (20 h) versus FRNT assay (72 h). We also investigated the correlation between sVNT and FRNT in NT titrations in terms of Pearson’s correlation coefficient (r) and sigmoidal curve fitting.ResultsIn NT screening assays, sVNT-eGFP screening achieved sensitivity and specificity of 100%. In quantitative neutralization assays, we observed a Pearson’s correlation coefficient of 0.83 for NT50 values between sVNT-Luc and FRNT.ConclusionsFacile VRP-based sVNT within 24 h proved highly reliable in the identification and quantification of neutralizing activity against CHIKV in clinical serum samples.

Novel Competitive ELISA Utilizing Trimeric Spike Protein of SARS-CoV-2, Could Identify More Than RBD-RBM Specific Neutralizing Antibodies in Hybrid Sera.

Since the initiation of the COVID-19 pandemic, there has been a need for the development of diagnostic methods to determine the factors implicated in mounting an immune response against the virus. The most promising indicator has been suggested to be neutralizing antibodies (nAbs), which mainly block the interaction between the Spike protein (S) of SARS-CoV-2 and the host entry receptor ACE2. In this study, we aimed to develop and optimize conditions of a competitive ELISA to measure serum neutralizing titer, using a recombinant trimeric Spike protein modified to have six additional proline residues (S(6P)-HexaPro) and h-ACE2. The results of our surrogate Virus Neutralizing Assay (sVNA) were compared against the commercial sVNT (cPass, Nanjing GenScript Biotech Co., Nanjing City, China), using serially diluted sera from vaccinees, and a high correlation of ID50-90 titer values was observed between the two assays. Interestingly, when we tested and compared the neutralizing activity of sera from eleven fully vaccinated individuals who subsequently contracted COVID-19 (hybrid sera), we recorded a moderate correlation between the two assays, while higher sera neutralizing titers were measured with sVNA. Our data indicated that the sVNA, as a more biologically relevant model assay that paired the trimeric S(6P) with ACE2, instead of the isolated RBD-ACE2 pairing cPass test, could identify nAbs other than the RBD-RBM specific ones.

Low pre-infection levels of neutralizing antibody in breakthrough infections after bivalent BA.4–5 vaccine and practical application of dried blood spots

The level of neutralizing antibodies required to confer protection against COVID-19 breakthrough infections (BIs) is unclear, and the ability to know the immune status of individuals against the rapidly changing endemic variants is limited. We assessed longitudinal serum anti-RBD antibody levels and neutralizing activities (NTs) against Omicron BA.5 and XBB.1.5 in healthcare workers following the fourth monovalent and fifth bivalent BA.4–5 vaccines. The occurrence of BIs was also followed, and pre-infection antibody levels were compared between patients who developed BI and those who did not. In addition, we collected whole blood samples on the same day as the sera and stored them on filter papers (nos. 545, 590, and 424) for up to two months, then measured their NTs using dried blood spots (DBS) eluates, and compared them with the NTs in paired sera. Pre-infection levels of NTs were lower in patients who developed BI than those who did not, but the anti-RBD antibody levels were not different between them. The NTs below 50 % using 200-fold diluted sera might be one of the indicators of high risk for COVID-19 BI. However, the NTs against XBB.1.5 at 6 months after the fifth dose of bivalent BA.4–5 vaccine were lower than this threshold in almost half of infection-naïve participants. NTs measured using DBS eluates were strongly correlated with those measured using paired sera, but the time and temperature stability varied with the type of filter paper; no. 545 filter paper was found to most suitable for NT evaluation.

The Equal Neutralizing Effectiveness of BNT162b2, ChAdOx1 nCoV-19, and Sputnik V Vaccines in the Palestinian Population.

Since the beginning of the COVID-19 pandemic, different viral vector-based and mRNA vaccines directed against the SARS-CoV-2 "S" spike glycoprotein have been developed and have shown a good profile in terms of safety and efficacy. Nevertheless, an unbiased comparison of vaccination efficiency, including post-vaccination neutralizing activity, between the different vaccines remains largely unavailable. This study aimed to compare the efficacy of one mRNA (BNT162b2) and two non-replicating adenoviral vector vaccines (ChAdOx1 nCoV-19 and Sputnik V) in a cohort of 1120 vaccinated Palestinian individuals who received vaccines on an availability basis and which displayed a unique diversity of genetic characteristics. We assessed the level of anti-S antibodies and further determined the antibody neutralizing activity in 261 of those individuals vaccinated with BNT162b2a (121), ChAdOx1 (72) or Sputnik V (68). Our results showed no significant difference in the distribution of serum-neutralizing activity or S-antibody serum levels for the three groups of vaccines, proving equivalence in efficacy for the three vaccines under real-life conditions. In addition, none of the eight demographic parameters tested had an influence on vaccination efficacy. Regardless of the vaccine type, the vaccination campaign ultimately played a pivotal role in significantly reducing the morbidity and mortality associated with COVID-19 in Palestine.

Escalating Dose Immunization Regimen in Non-Human Primates to Improve Immunogen-Specific Responses

Abstract HIV-1 remains a major health threat, highlighting the need for a vaccine that induces broadly neutralizing antibodies. Epitope-based vaccine designs that focus humoral responses to vulnerable sites on the HIV-1 Env trimer protein are promising approaches, including those targeting the HIV-1 fusion peptide (FP). Escalating dose (ED) immunizations are a strategy to increase immunogen uptake into germinal centers and boost affinity maturation of the antiviral antibody response. In this study, we tested the impact of an ED immunization scheme on enhancing the FP-directed humoral response. Five groups of non-human primates were immunized: four received an ED immunization of either FP or a cocktail of FP+trimer, and one control group was dosed with a bolus FP+trimer cocktail. Two ED groups were adjuvanted with SMNP. The remaining groups used 3M052/alum. Fourteen weeks post-immunization, all ED groups had higher anti-FP IgG titers compared to the control, with the cocktail ED group adjuvanted with 3M052/alum characterized by 14.5-fold higher titers than the bolus control. While the ED cocktail and bolus groups had similar anti-trimer IgG titers, the ED groups had a higher non-base trimer response, shown by an 8.6-fold IgG increase between the 3M052/alum cocktail ED group and its bolus control. ED prime seems promising in raising anti-immunogen titers and lowering responses to the artificial trimer base, and further boosts will be administered to elicit serum neutralizing activity.

Antibody-dependent enhancement (ADE) of SARS-CoV-2 in patients exposed to MERS-CoV and SARS-CoV-2 antigens.

This study evaluated the potential for antibody-dependent enhancement (ADE) in serum samples from patients exposed to Middle East respiratory syndrome coronavirus (MERS-CoV). Furthermore, we evaluated the effect of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination on ADE in individuals with a MERS infection history. We performed ADE assay in sera from MERS recovered and SARS-CoV-2-vaccinated individuals using BHK cells expressing FcgRIIa, SARS-CoV-2, and MERS-CoV pseudoviruses (PVs). Further, we analyzed the association of ADE to serum IgG levels and neutralization. Out of 16 MERS patients, nine demonstrated ADE against SARS-CoV-2 PV, however, none of the samples demonstrated ADE against MERS-CoV PV. Furthermore, out of the seven patients exposed to SARS-CoV-2 vaccination after MERS-CoV infection, only one patient (acutely infected with MERS-CoV) showed ADE for SARS-CoV-2 PV. Further analysis indicated that IgG1, IgG2, and IgG3 against SARS-CoV-2 S1 and RBD subunits, IgG1 and IgG2 against the MERS-CoV S1 subunit, and serum neutralizing activity were low in ADE-positive samples. In summary, samples from MERS-CoV-infected patients exhibited ADE against SARS-CoV-2 and was significantly associated with low levels of neutralizing antibodies. Subsequent exposure to SARS-CoV-2 vaccination resulted in diminished ADE activity while the PV neutralization assay demonstrated a broadly reactive antibody response in some patient samples.

Tixagevimab/Cilgavimab: Still a Valid Prophylaxis against COVID-19 New Variants?

this study aims to evaluate the efficacy of tixagevimab/cilgavimab (Evusheld™) against various SARS-CoV-2 variants, including newer Omicron sublineages, in an immunocompromised cohort and in vitro. Conducted in Italy, this research involves immunocompromised patients who received Evusheld. It evaluates serum neutralization activity against different SARS-CoV-2 strains (20A.EU1, BA.5, BQ.1, XBB.1.5, XBB.1.16, and EG.5) before (T0), after 14 (T1), and after 30 (T2) days from the tixagevimab/cilgavimab injection. Furthermore, the in vitro activity of Evusheld against SARS-CoV-2 VOCs was evaluated. The cohort was composed of 72 immunocompromised patients. The serum neutralizing activity of tixagevimab/cilgavimab-treated patients was notably lower against newer variants such as BQ.1, XBB.1.5, XBB.1.16, and EG.5. Then, the in vitro study detailed specific EC50 values to quantify the activity of tixagevimab/cilgavimab against various SARS-CoV-2 VOCs. Newer variants like BQ.1 and XBB.1.5 exhibited notably lower neutralization, underscoring the challenges in effectively countering the evolving virus. Interestingly, tixagevimab/cilgavimab maintained reduced but still valid activity against EG.5 with an EC50 of 189 ng/mL and Cmax/EC90 of 110.7. Tixagevimab/cilgavimab efficacy wanes against novel subvariants. This underscores the critical need for ongoing adaptation and vigilance in prophylactic strategies to effectively counter the dynamic and unpredictable nature of the COVID-19 pandemic.

Potent and broadly neutralizing antibodies against sarbecoviruses induced by sequential COVID-19 vaccination

The current SARS-CoV-2 variants strikingly evade all authorized monoclonal antibodies and threaten the efficacy of serum-neutralizing activity elicited by vaccination or prior infection, urging the need to develop antivirals against SARS-CoV-2 and related sarbecoviruses. Here, we identified both potent and broadly neutralizing antibodies from a five-dose vaccinated donor who exhibited cross-reactive serum-neutralizing activity against diverse coronaviruses. Through single B-cell sorting and sequencing followed by a tailor-made computational pipeline, we successfully selected 86 antibodies with potential cross-neutralizing ability from 684 antibody sequences. Among them, PW5-570 potently neutralized all SARS-CoV-2 variants that arose prior to Omicron BA.5, and the other three could broadly neutralize all current SARS-CoV-2 variants of concern, SARS-CoV and their related sarbecoviruses (Pangolin-GD, RaTG13, WIV-1, and SHC014). Cryo-EM analysis demonstrates that these antibodies have diverse neutralization mechanisms, such as disassembling spike trimers, or binding to RBM or SD1 to affect ACE2 binding. In addition, prophylactic administration of these antibodies significantly protects nasal turbinate and lung infections against BA.1, XBB.1, and SARS-CoV viral challenge in golden Syrian hamsters, respectively. Importantly, post-exposure treatment with PW5-5 and PW5-535 also markedly protects against XBB.1 challenge in these models. This study reveals the potential utility of computational process to assist screening cross-reactive antibodies, as well as the potency of vaccine-induced broadly neutralizing antibodies against current SARS-CoV-2 variants and related sarbecoviruses, offering promising avenues for the development of broad therapeutic antibody drugs.

A SARS-CoV-2 RBD vaccine fused to the chemokine MIP-3α elicits sustained murine antibody responses over 12 months and enhanced lung T-cell responses.

Previous studies have demonstrated enhanced efficacy of vaccine formulations that incorporate the chemokine macrophage inflammatory protein 3α (MIP-3α) to direct vaccine antigens to immature dendritic cells. To address the reduction in vaccine efficacy associated with a mutation in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mutants, we have examined the ability of receptor-binding domain vaccines incorporating MIP-3α to sustain higher concentrations of antibody when administered intramuscularly (IM) and to more effectively elicit lung T-cell responses when administered intranasally (IN). BALB/c mice aged 6-8 weeks were immunized intramuscularly or intranasally with DNA vaccine constructs consisting of the SARS-CoV-2 receptor-binding domain alone or fused to the chemokine MIP-3α. In a small-scale (n = 3/group) experiment, mice immunized IM with electroporation were followed up for serum antibody concentrations over a period of 1 year and for bronchoalveolar antibody levels at the termination of the study. Following IN immunization with unencapsulated plasmid DNA (n = 6/group), mice were evaluated at 11 weeks for serum antibody concentrations, quantities of T cells in the lungs, and IFN-γ- and TNF-α-expressing antigen-specific T cells in the lungs and spleen. At 12 months postprimary vaccination, recipients of the IM vaccine incorporating MIP-3α had significantly, approximately threefold, higher serum antibody concentrations than recipients of the vaccine not incorporating MIP-3α. The area-under-the-curve analyses of the 12-month observation interval demonstrated significantly greater antibody concentrations over time in recipients of the MIP-3α vaccine formulation. At 12 months postprimary immunization, only recipients of the fusion vaccine had concentrations of serum-neutralizing activity deemed to be effective. After intranasal immunization, only recipients of the MIP-3α vaccine formulations developed T-cell responses in the lungs significantly above those of PBS controls. Low levels of serum antibody responses were obtained following IN immunization. Although requiring separate IM and IN immunizations for optimal immunization, incorporating MIP-3α in a SARS-CoV-2 vaccine construct demonstrated the potential of a stable and easily produced vaccine formulation to provide the extended antibody and T-cell responses that may be required for protection in the setting of emerging SARS-CoV-2 variants. Without electroporation, simple, uncoated plasmid DNA incorporating MIP-3α administered intranasally elicited lung T-cell responses.

A method for screening CDV microneutralization activity in microvolume samples

ObjectiveThis study aims to establish a screening method for canine distemper virus (CDV) microneutralizing activity suitable for microvolume samples. MethodsThis 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. ResultsThe 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%. ConclusionThis 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.

High interleukin-6 levels induced by COVID-19 pneumonia correlate with increased circulating follicular helper T cell frequency and strong neutralization antibody response in the acute phase of Omicron breakthrough infection.

Acute immune responses to coronavirus disease 2019 (COVID-19) are influenced by variants, vaccination, and clinical severity. Thus, the outcome of these responses may differ between vaccinated and unvaccinated patients and those with and without COVID-19-related pneumonia. In this study, these differences during infection with the Omicron variant were investigated. A total of 67 patients (including 47 vaccinated and 20 unvaccinated patients) who were hospitalized within 5 days after COVID-19 symptom onset were enrolled in this prospective observational study. Serum neutralizing activity was evaluated using a pseudotyped virus assay and serum cytokines and chemokines were measured. Circulating follicular helper T cell (cTfh) frequencies were evaluated using flow cytometry. Twenty-five patients developed COVID-19 pneumonia on hospitalization. Although the neutralizing activities against wild-type and Delta variants were higher in the vaccinated group, those against the Omicron variant as well as the frequency of developing pneumonia were comparable between the vaccinated and unvaccinated groups. IL-6 and CXCL10 levels were higher in patients with pneumonia than in those without it, regardless of their vaccination status. Neutralizing activity against the Omicron variant were higher in vaccinated patients with pneumonia than in those without it. Moreover, a distinctive correlation between neutralizing activity against Omicron, IL-6 levels, and cTfh proportions was observed only in vaccinated patients. The present study demonstrates the existence of a characteristic relationship between neutralizing activity against Omicron, IL-6 levels, and cTfh proportions in Omicron breakthrough infection.

A First-in-Human Randomized Study to Assess the Safety, Tolerability, Pharmacokinetics, and Neutralization Profile of Two Investigational Long-Acting Anti-SARS-CoV-2 Monoclonal Antibodies.

COVID-19 remains a significant risk for the immunocompromised given their lower responsiveness to vaccination or infection. Therefore, passive immunity through long-acting monoclonal antibodies (mAbs) offers a needed approach for pre-exposure prophylaxis (PrEP). Our study evaluated safety, anti-SARS-CoV-2 neutralizing activity, nasal penetration, and pharmacokinetics (PK) of two half-life-extended investigational mAbs, AER001 and AER002, providing the first demonstration of upper airway penetration of mAbs with the LS-modification. This randomized, double-blind, placebo-controlled phaseI study enrolled healthy adults (n = 80) who received two long-acting COVID mAbs (AER001 and AER002), AER002 alone, or placebo. The dose ranged from 100mg (mg) to 1200mg per mAb component. The primary objective was to describe the safety and tolerability following intravenous (IV) administration. Secondary objectives were to describe PK, anti-drug antibodies (ADA), neutralization activity levels, and safety evaluation through 6months of follow-up. The majority (97.6%) of the reported adverse events (AE) post administration were of grade1 severity. There were no serious adverse events (SAE) or ADAs. AER001 and AER002 successfully achieved an extended half-life of 105days and 97.5days, respectively. Participants receiving AER001 and AER002 (300mg each) or AER002 (300mg) alone showed 15- and 26-fold higher neutralization levels against D614G and omicron BA.1 than the placebo group24h post-administration. Single 300 or 1200mg IV dose of AER001 and AER002 resulted in nasal mucosa transudation of approximately 2.5% and 2.7%, respectively. AER001 and AER002 showed an acceptable safety profile and extended half-life. High serum neutralization activity was observed against D614G and Omicron BA.1 compared to the placebo group. These data support that LS-modified mAbs can achieve durability, safety, potency, and upper airway tissue penetration and will guide the development of the next generation of mAbs for COVID-19 prevention and treatment. EudraCT Number 2022-001709-35 (COV-2022-001).

Dynamics and durability of HIV-1 neutralization are determined by viral replication

Human immunodeficiency virus type 1 (HIV-1)-neutralizing antibodies (nAbs) that prevent infection are the main goal of HIV vaccine discovery. But as no nAb-eliciting vaccines are yet available, only data from HIV-1 neutralizers—persons with HIV-1 who naturally develop broad and potent nAbs—can inform about the dynamics and durability of nAb responses in humans, knowledge which is crucial for the design of future HIV-1 vaccine regimens. To address this, we assessed HIV-1-neutralizing immunoglobulin G (IgG) from 2,354 persons with HIV-1 on or off antiretroviral therapy (ART). Infection with non-clade B viruses, CD4+ T cell counts <200 µl−1, being off ART and a longer time off ART were independent predictors of a more potent and broad neutralization. In longitudinal analyses, we found nAb half-lives of 9.3 and 16.9 years in individuals with no- or low-level viremia, respectively, and 4.0 years in persons who newly initiated ART. Finally, in a potent HIV-1 neutralizer, we identified lower fractions of serum nAbs and of nAb-encoding memory B cells after ART initiation, suggesting that a decreasing neutralizing serum activity after antigen withdrawal is due to lower levels of nAbs. These results collectively show that HIV-1-neutralizing responses can persist for several years, even at low antigen levels, suggesting that an HIV-1 vaccine may elicit a durable nAb response.

Neutralization against Omicron sublineages (BA.2/BA.5/BQ.1.1/XBB/XBB.1.5) in bivalent BNT162b2-vaccinated HCWs with or without risk factors, or following BT infection with Omicron

SARS-CoV-2-BA.4/5-adapted-bivalent-BNT162b2-vaccine (bvBNT), developed in response to the recent emergence of immune-evasive Omicron-variants, has been given to individuals who completed at least 2-doses of the monovalent-BNT162b2-vaccine (mvBNT). In the present cohort study, we evaluated neutralization-titers (NT50s) against Wuhan-strain (SCoV2Wuhan) and Omicron-sublineages including BA.2/BA.5/BQ.1.1/XBB/XBB.1.5, and vaccine-elicited S1-binding-IgG in sera from participants-vaccinated with 5th-bvBNT following 4th-mvBNT. The 5th-bvBNT-dose elicited good protective-activity against SCoV2Wuhan with geometric-mean (gMean)-NT50 of 1966–2091, higher than the peak-values post-4th-mvBNT with no statistical significance, and favorable neutralization-activity against not only BA.5 but also BA.2, with ~ 3.2-/~ 2.2-fold greater gMean-NT50 compared to the peak-values post-4th-mvBNT-dose, in participants with or without risk factors. However, neutralization-activity of sera post-5th-bvBNT-dose was low against BQ.1.1/XBB/XBB.1.5. Interestingly, participants receiving bvBNT following breakthrough (BT) infection during Omicron-wave had significantly enhanced neutralization-activity against SCoV2Wuhan/BA.2/BA.5 with ~ 4.6-/~ 6.3-/~ 8.1-fold greater gMean-NT50, respectively, compared to uninfected participants receiving bvBNT. Sera from BT-infected-participants receiving bvBNT had enhanced neutralization-activity against BQ.1.1/XBB/XBB.1.5 by ~ 3.8-fold compared to those from the same participants post-4th-mvBNT-dose, and had enhanced gMean-NT50 ~ 5.4-fold greater compared to those of uninfected-participants’ sera post-bvBNT. These results suggest that repeated stimulation brought about by exposure to BA.5’s-Spike elicit favorable cross-neutralization-activity against various SARS-CoV-2-variants.

Cell-mediated and Neutralizing Antibody Responses to the SARS-CoV-2 Omicron BA.4/BA.5-adapted Bivalent Vaccine Booster in Kidney and Liver Transplant Recipients.

The immunogenicity elicited by the Omicron BA.4/BA.5-adapted bivalent booster vaccine after solid organ transplantation (SOT) has not been characterized. We assessed cell-mediated and neutralizing IgG antibody responses against the BA.4/BA.5 spike receptor-binding domain at baseline and 2 wk after the administration of an mRNA-based bivalent (ancestral strain and BA.4/BA.5 subvariants) vaccine among 30 SOT recipients who had received ≥3 monovalent vaccine doses. Previous coronavirus disease 2019 history was present in 46.7% of them. We also recruited a control group of 19 nontransplant healthy individuals. Cell-mediated immunity was measured by fluorescent ELISpot assay for interferon (IFN)-γ secretion, whereas the neutralizing IgG antibody response against the BA.4/BA.5 spike receptor-binding domain was quantified with a competitive ELISA. The median number of BA.4/BA.5 spike-specific IFN-γ-producing spot-forming units (SFUs) increased from baseline to 2 wk postbooster (83.8 versus 133.0 SFUs/106 peripheral blood mononuclear cells; P = 0.0017). Seropositivity rate also increased (46.7%-83.3%; P = 0.001), as well as serum neutralizing activity (4.2%-78.3%; P < 0.0001). Patients with no prior coronavirus disease 2019 history experienced higher improvements in cell-mediated and neutralizing responses after booster vaccination. There was no correlation between BA.4/BA.5 spike-specific IFN-γ-producing SFUs and neutralizing activity. Nontransplant controls showed more robust postbooster cell-mediated immunity than SOT recipients (591.1 versus 133.0 IFN-γ-producing SFUs/106 peripheral blood mononuclear cells; P < 0.0001), although no differences were observed for antibody responses in terms of postbooster seropositivity rates or neutralizing activity. Booster with the BA.4/BA.5-adapted bivalent vaccine generated strong subvariant-specific responses among SOT recipients. Booster-induced cell-mediated immunity, however, remained lower than in immunocompetent individuals.

Activity of domain III-specific antibodies in early convalescence: A case study

The Dengue virus complex (DENV), formed by four serotypes, constitutes the most important arbovirus affecting humans. The structural domain III of their envelope protein (DIII) elicits strongly neutralizing serotype-specific antibodies. Contrasting results have been obtained regarding their role in the serum neutralizing activity of infected patients. We used a DENV immune serum from a secondary infection to examine the impact of characterizing the anti-DIII antibody response after affinity purification with recombinant DIII proteins to eliminate potential interferences from the interactions with human plasma proteins and other anti-DENV antibodies. Total anti-DENV IgG repertoire and anti-DIIIE antibodies were compared in functionality. In early convalescence, reactivity of anti-DIII antibodies is serotype specific and exhibits the strongest reactivity with infecting serotypes. Purification of anti-DIII antibodies emphasizes the reactivity profile as compared to total IgG fraction and serum. Serotype-specificity of the virus neutralization activity correlated with the apparent kD of the binding to recombinant DIIIs.