Serum Neutralizing Activity Research Articles

Mixed formulation of mRNA and protein-based COVID-19 vaccines triggered superior neutralizing antibody responses.

Integrating different types of vaccines into a singular immunization regimen is an effective and accessible approach to strengthen and broaden the immunogenicity of existing coronavirus disease 2019 (COVID-19) vaccine candidates. To optimize the immunization strategy of the novel mRNA-based vaccine and recombinant protein subunit vaccine that attracted much attention in COVID-19 vaccine development, we evaluated the immunogenicity of different combined regimens with the mRNA vaccine (RNA-RBD) and protein subunit vaccine (PS-RBD) in mice. Compared with homologous immunization of RNA-RBD or PS-RBD, heterologous prime-boost strategies for mRNA and protein subunit vaccines failed to simultaneously enhance neutralizing antibody (NAb) and Th1 cellular response in this study, showing modestly higher serum neutralizing activity and antibody-dependent cell-mediated cytotoxicity for "PS-RBD prime, RNA-RBD boost" and robust Th1 type cellular response for "RNA-RBD prime, PS-RBD boost". Interestingly, immunizing the mice with the mixed formulation of the two aforementioned vaccines in various proportions further significantly enhanced the NAb responses against ancestral, Delta, and Omicron strains and manifested increased Th1-type responses, suggesting that a mixed formulation of mRNA and protein vaccines might be a more prospective vaccination strategy. This study provides basic research data on the combined vaccination strategies of mRNA and protein-based COVID-19 vaccines.

Humoral immune response and live-virus neutralization of the SARS-CoV-2 omicron (BA.1) variant after COVID-19 mRNA vaccination in children and young adults with chronic kidney disease

BackgroundData on humoral immune response to standard COVID-19 vaccination are scarce in adolescent patients and lacking for children below 12 years of age with chronic kidney disease including kidney transplant recipients.MethodsWe therefore investigated in this retrospective two-center study (DRKS00024668; registered 23.03.2021) the humoral immune response to a standard two-dose mRNA vaccine regimen in 123 CKD patients aged 5–30 years. A live-virus assay was used to assess the serum neutralizing activity against the SARS-CoV-2 omicron (BA.1) variant.ResultsChildren aged 5–11 years had a comparable rate and degree of immune response to adolescents despite lower vaccine doses (10 µg vs. 30 µg BNT162b2). Treatment with two (odds ratio 9.24) or three or more (odds ratio 17.07) immunosuppressants was an independent risk factor for nonresponse. The immune response differed significantly among three patient cohorts: 48 of 77 (62.3%) kidney transplant recipients, 21 of 26 (80.8%) patients on immunosuppressive therapy, and 19 of 20 (95.0%) patients with chronic kidney disease without immunosuppressive therapy responded. In the kidney transplant recipients, immunosuppressive regimens comprising mycophenolate mofetil, an eGFR of < 60 mL/min/1.73 m2, and female sex were independent risk factors for nonresponse. Two of 18 (11.1%) and 8 of 16 (50.0%) patients with an anti-S1-RBD IgG of 100–1411 and > 1411 BAU/mL, respectively, showed a neutralization activity against the omicron variant.ConclusionA standard mRNA vaccine regimen in immunosuppressed children and adolescents with kidney disease elicits an attenuated humoral immune response with effective live virus neutralization against the omicron variant in approximately 10% of the patients, underlying the need for omicron-adapted vaccination.Graphical abstractA higher resolution version of the Graphical abstract is available as Supplementary information

Saliva and Plasma Neutralizing Activity Induced by the Administration of a Third bnt162b2 Vaccine Dose.

The BNT162b2 vaccine induces neutralizing activity (NA) in serum, but no data are available on whether a third-dose activates specific-immunity within the oral mucosa, representing the primary route of viral-entry. To carefully address this issue, we investigated if such immunity is boosted by SARS-CoV-2-infection; how long it is maintained over-time; and if it protects against the SARS-CoV-2 lineage B.1 (EU) and the emerging Delta and Omicron variants. NA was measured in plasma and saliva samples from: uninfected SARS-CoV-2-Vaccinated (SV), subjects infected prior to vaccination (SIV), and subjects who were infected after the second (SIV2) or the third (SIV3) vaccine dose. Samples were collected immediately before (T0), 15 days (T1), and 90 days (T2) post third-dose administration (SV and SIV), or 15 days post-infection (SIV2 and SIV3). In all the enrolled groups, NA in plasma and saliva: (i) was higher against EU compared to the other variants at all time-points (SV: T0 and T1, EU vs. both Delta and Omicron p &lt; 0.001; T2 p &lt; 0.01) (SIV: T0, EU vs. Delta p &lt; 0.05; EU vs. Omi p &lt; 0.01; T1 and T2 EU vs. Delta p &lt; 0.01; EU vs. Omi p &lt; 0.001); (ii) was boosted by the administration of the third dose; iii) declined over-time, albeit being detectable in almost all subjects at T2. The monitoring of NA over time will be important in clarifying if different NA levels may influence either acquisition or course of infection to properly plan the timing of a fourth vaccine dose administration.

Diminished neutralization responses towards SARS-CoV-2 Omicron VoC after mRNA or vector-based COVID-19 vaccinations

SARS-CoV-2 variants accumulating immune escape mutations provide a significant risk to vaccine-induced protection against infection. The novel variant of concern (VoC) Omicron BA.1 and its sub-lineages have the largest number of amino acid alterations in its Spike protein to date. Thus, they may efficiently escape recognition by neutralizing antibodies, allowing breakthrough infections in convalescent and vaccinated individuals in particular in those who have only received a primary immunization scheme. We analyzed neutralization activity of sera from individuals after vaccination with all mRNA-, vector- or heterologous immunization schemes currently available in Europe by in vitro neutralization assay at peak response towards SARS-CoV-2 B.1, Omicron sub-lineages BA.1, BA.2, BA.2.12.1, BA.3, BA.4/5, Beta and Delta pseudotypes and also provide longitudinal follow-up data from BNT162b2 vaccinees. All vaccines apart from Ad26.CoV2.S showed high levels of responder rates (96–100%) towards the SARS-CoV-2 B.1 isolate, and minor to moderate reductions in neutralizing Beta and Delta VoC pseudotypes. The novel Omicron variant and its sub-lineages had the biggest impact, both in terms of response rates and neutralization titers. Only mRNA-1273 showed a 100% response rate to Omicron BA.1 and induced the highest level of neutralizing antibody titers, followed by heterologous prime-boost approaches. Homologous BNT162b2 vaccination, vector-based AZD1222 and Ad26.CoV2.S performed less well with peak responder rates of 48%, 56% and 9%, respectively. However, Omicron responder rates in BNT162b2 recipients were maintained in our six month longitudinal follow-up indicating that individuals with cross-protection against Omicron maintain it over time. Overall, our data strongly argue for booster doses in individuals who were previously vaccinated with BNT162b2, or a vector-based primary immunization scheme.

Co-immunization with hemagglutinin stem immunogens elicits cross-group neutralizing antibodies and broad protection against influenza A viruses

Current influenza vaccines predominantly induce immunity to the hypervariable hemagglutinin (HA) head, requiring frequent vaccine reformulation. Conversely, the immunosubdominant yet conserved HA stem harbors a supersite that is targeted by broadly neutralizing antibodies (bnAbs), representing a prime target for universal vaccines. Here, we showed that the co-immunization of two HA stem immunogens derived from group 1 and 2 influenza A viruses elicits cross-group protective immunity and neutralizing antibody responses in mice, ferrets, and nonhuman primates (NHPs). Immunized mice were protected from multiple group 1 and 2 viruses, and all animal models showed broad serum-neutralizing activity. A bnAb isolated from an immunized NHP broadly neutralized and protected against diverse viruses, including H5N1 and H7N9. Genetic and structural analyses revealed strong homology between macaque and human bnAbs, illustrating common biophysical constraints for acquiring cross-group specificity. Vaccine elicitation of stem-directed cross-group-protective immunity represents a step toward the development of broadly protective influenza vaccines.

Development of rapid neutralization assay of viral hemorrhagic septicemia virus (VHSV) based on chimeric rhabdovirus expressing heterologous glycoprotein

The titer of neutralizing antibodies (NAbs) against viral hemorrhagic septicemia virus (VHSV) has been determined by conventional neutralization assay based on the observation of cytopathic effect (CPE) and plaque formation in cultured cells. However, this method requires several days for the determination and can be affected by operator bias. To develop a rapid and high-throughput neutralization assay against VHSV, we rescued a surrogate chimeric snakehead rhabdovirus, rSHRV-Gvhsv-eGFP, which has the enhanced green fluorescent protein (eGFP) gene between N and P genes and has VHSV G gene instead of SHRV G gene in the genome. The efficacy of rSHRV-Gvhsv-eGFP to determine serum neutralization activity was evaluated using various serum samples derived from New Zealand white rabbits and olive flounder (Paralichthys oliavaceus). Although neutralization titers analyzed using rSHRV-Gvhsv-eGFP were similar to the titers measured using rVHSV-A-eGFP, the time needed for the determination of neutralization titer was much shortened (24 h for rSHRV-Gvhsv-eGFP and 48 h for rVHSV-A-eGFP), proving the usefulness of rSHRV-Gvhsv-eGFP for the neutralization assay against VHSV. In addition, as the neutralization activities using rSHRV-Gvhsv-eGFP could be well-observed without adding fresh serum as a complement source, no preparation is required for the optimization of control fresh serum from naïve fish. The present results suggest that the rapid neutralization assay using rSHRV-Gvhsv-eGFP can be used to investigate neutralization activities against VHSV.

Serum neutralization of SARS coronavirus 2 Omicron sublineages BA.1 and BA.2 and cellular immune responses 3 months after booster vaccination

ObjectivesWe investigated serum neutralizing activity against BA.1 and BA.2 Omicron sublineages and T cell response before and 3 months after administration of the booster vaccine in healthcare workers (HCWs). MethodsHCWs aged 18–65 years who were vaccinated and received booster doses of the BNT162b2 vaccine were included. Anti–SARS coronavirus 2 IgG levels and cellular response (through interferon γ ELISpot assay) were evaluated in all participants, and neutralizing antibodies against Delta, BA.1, and BA.2 were evaluated in participants with at least one follow-up visit 1 or 3 months after the administration of the booster dose. ResultsAmong 118 HCWs who received the booster dose, 102 and 84 participants attended the 1-month and 3-month visits, respectively. Before the booster vaccine dose, a low serum neutralizing activity against Delta, BA.1, and BA.2 was detectable in only 39/102 (38.2%), 8/102 (7.8%), and 12/102 (11.8%) participants, respectively. At 3 months, neutralizing antibodies against Delta, BA.1, and BA.2 were detected in 84/84 (100%), 79/84 (94%), and 77/84 (92%) participants, respectively. Geometric mean titres of neutralizing antibodies against BA.1 and BA.2 were 2.2-fold and 2.8-fold reduced compared with those for Delta. From 1 to 3 months after the administration of the booster dose, participants with a recent history of SARS coronavirus 2 infection (n = 21/84) had persistent levels of S1 reactive specific T cells and neutralizing antibodies against Delta and BA.2 and 2.2-fold increase in neutralizing antibodies against BA.1 (p 0.014). Conversely, neutralizing antibody titres against Delta (2.5-fold decrease, p < 0.0001), BA.1 (1.5-fold, p 0.02), and BA.2 (2-fold, p < 0.0001) declined from 1 to 3 months after the administration of the booster dose in individuals without any recent infection. DiscussionThe booster vaccine dose provided significant and similar response against BA.1 and BA.2 Omicron sublineages; however, the immune response declined in the absence of recent infection.

Seroprevalence of SARS-CoV-2 in Mexican Health Care Workers after Two Years of the Pandemic: The Picture of an Ophthalmic Medical Centre

ABSTRACT Objective In this study, we investigated the impact of the SARS-CoV-2 vaccination on seroprevalence in a cohort of healthcare workers (HCW) at an ophthalmic medical center. Methods IgG antibodies against the N, S1, and S2 antigens of SARS-CoV-2 as well as their serum neutralizing activity were determined. Results In the present study, we observed that 98.4% of HCW were seropositive for S1/S2 proteins of SARS-CoV-2 due to the national vaccination program. Interestingly, 78.4% of the participants had anti-N protein antibodies, suggesting previous COVID-19 infection. We also evaluated the neutralizing antibodies and found that the mean value was high (90.7%). Conclusion These results indicate that our HCWs cohort presented a robust hybrid humoral response owing to the massive national vaccination program and natural infections.

An efficient approach for SARS-CoV-2 monoclonal antibody production via modified mRNA-LNP immunization

Throughout the COVID-19 pandemic, many prophylactic and therapeutic drugs have been evaluated and introduced. Among these treatments, monoclonal antibodies (mAbs) that bind to and neutralize SARS-CoV-2 virus have been applied as complementary and alternative treatments to vaccines. Although different methodologies have been utilized to produce mAbs, traditional hybridoma fusion technology is still commonly used for this purpose due to its unmatched performance record. In this study, we coupled the hybridoma fusion strategy with mRNA-lipid nanoparticle (LNP) immunization. This time-saving approach can circumvent biological and technical hurdles, such as difficult-to-express membrane proteins, antigen instability, and the lack of posttranslational modifications on recombinant antigens. We used mRNA-LNP immunization and hybridoma fusion technology to generate mAbs against the receptor binding domain (RBD) of SARS-CoV-2 spike (S) protein. Compared with traditional protein-based immunization approaches, inoculation of mice with RBD mRNA-LNP induced higher titers of serum antibodies and markedly increased serum neutralizing activity. The mAbs we obtained can bind to SARS-CoV-2 RBDs from several variants. Notably, RBD-mAb-3 displayed particularly high binding affinities and neutralizing potencies against both Alpha and Delta variants. In addition to introducing specific mAbs against SARS-CoV-2, our data generally demonstrate that mRNA-LNP immunization may be useful to quickly generate highly functional mAbs against emerging infectious diseases.

Omicron BA.2 breakthrough infection enhances cross-neutralization of BA.2.12.1 and BA.4/BA.5.

BNT162b2-vaccinated individuals after Omicron BA.1 breakthrough infection have strong serum neutralizing activity against Omicron BA.1, BA.2, and previous SARS-CoV-2 variants of concern (VOCs), yet less against the highly contagious Omicron sublineages BA.4 and BA.5 that have displaced previous variants. As the latter sublineages are derived from Omicron BA.2, we characterized serum neutralizing activity of COVID-19 mRNA vaccine triple-immunized individuals who experienced BA.2 breakthrough infection. We demonstrate that sera of these individuals have broadly neutralizing activity against previous VOCs as well as all tested Omicron sublineages, including BA.2 derived variants BA.2.12.1, BA.4/BA.5. Furthermore, applying antibody depletion we showed that neutralization of BA.2 and BA.4/BA.5 sublineages by BA.2 convalescent sera is driven to a significant extent by antibodies targeting the N-terminal domain (NTD) of the spike glycoprotein. However, neutralization by Omicron BA.1 convalescent sera depends exclusively on antibodies targeting the receptor binding domain (RBD). These findings suggest that exposure to Omicron BA.2, in contrast to BA.1 spike glycoprotein, triggers significant NTD specific recall responses in vaccinated individuals and thereby enhances the neutralization of BA.4/BA.5 sublineages. Given the current epidemiology with a predominance of BA.2 derived sublineages like BA.4/BA.5 and rapidly ongoing evolution, these findings helped to inform development of our Omicron BA.4/BA.5-adapted vaccine.

Enhanced antibody responses in fully vaccinated individuals against pan-SARS-CoV-2 variants following Omicron breakthrough infection

SummaryOmicron has become the globally dominant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant, creating additional challenges due to its ability to evade neutralization. Here, we report that neutralizing antibodies against Omicron variants are undetected following COVID-19 infection with ancestral or past SARS-CoV-2 variant viruses or after two-dose mRNA vaccination. Compared with two-dose vaccination, a three-dose vaccination course induces broad neutralizing antibody responses with improved durability against different SARS-CoV-2 variants, although neutralizing antibody titers against Omicron remain low. Intriguingly, among individuals with three-dose vaccination, Omicron breakthrough infection substantially augments serum neutralizing activity against a broad spectrum of SARS-CoV-2 variants, including Omicron variants BA.1, BA.2, and BA.5. Additionally, after Omicron breakthrough infection, memory T cells respond to the spike proteins of both ancestral and Omicron SARS-CoV-2 by producing cytokines with polyfunctionality. These results suggest that Omicron breakthrough infection following three-dose mRNA vaccination induces pan-SARS-CoV-2 immunity that may protect against emerging SARS-CoV-2 variants of concern.

Receptor-Binding Domain (RBD) Antibodies Contribute More to SARS-CoV-2 Neutralization When Target Cells Express High Levels of ACE2.

Neutralization assays are experimental surrogates for the effectiveness of infection- or vaccine-elicited polyclonal antibodies and therapeutic monoclonal antibodies targeting SARS-CoV-2. However, the measured neutralization can depend on the details of the experimental assay. Here, we systematically assess how ACE2 expression in target cells affects neutralization by antibodies to different spike epitopes in lentivirus pseudovirus neutralization assays. For high ACE2-expressing target cells, receptor-binding domain (RBD) antibodies account for nearly all neutralizing activity in polyclonal human sera. However, for lower ACE2-expressing target cells, antibodies targeting regions outside the RBD make a larger (although still modest) contribution to serum neutralization. These serum-level results are mirrored for monoclonal antibodies: N-terminal domain (NTD) antibodies and RBD antibodies that do not compete for ACE2 binding incompletely neutralize on high ACE2-expressing target cells, but completely neutralize on cells with lower ACE2 expression. Our results show that the ACE2 expression level in the target cells is an important experimental variable, and that high ACE2 expression emphasizes the role of a subset of RBD-directed antibodies.

Serum neutralization activity declines but memory B cells persist after cure of chronic hepatitis C

The increasing incidence of hepatitis C virus (HCV) infections underscores the need for an effective vaccine. Successful vaccines to other viruses generally depend on a long-lasting humoral response. However, data on the half-life of HCV-specific responses are lacking. Here we study archived sera and mononuclear cells that were prospectively collected up to 18 years after cure of chronic HCV infection to determine the role of HCV antigen in maintaining neutralizing antibody and B cell responses. We show that HCV-neutralizing activity decreases rapidly in potency and breadth after curative treatment. In contrast, HCV-specific memory B cells persist, and display a restored resting phenotype, normalized chemokine receptor expression and preserved ability to differentiate into antibody-secreting cells. The short half-life of HCV-neutralizing activity is consistent with a lack of long-lived plasma cells. The persistence of HCV-specific memory B cells and the reduced inflammation after cure provide an opportunity for vaccination to induce protective immunity against re-infection.

Evaluation of a rapid semiquantitative lateral flow assay for the prediction of serum neutralizing activity against SARS-CoV-2 variants.

BackgroundNeutralizing antibodies (NAbs) against SARS-CoV-2 have been shown to correlate with protection against infection. Simple tools such as lateral flow assays (LFA) that can accurately measure NAbs may be useful for monitoring anti-SARS-CoV-2 immunity in the future.ObjectivesWe assessed the performance of the ichroma™ COVID-19 nAb test, a rapid semiquantitative LFA, for the prediction of serum neutralizing activity against SARS-CoV-2 variants.Study designSerum samples were collected from COVID-19 recovered patients and vaccinated individuals. The result of the ichroma assay was provided as inhibition rate, and was compared to anti-SARS-CoV-2 IgG levels, and NAbs against Alpha, Delta and Omicron variants.ResultsA total of 90 sera from recovered unvaccinated patients and 209 sera from the vaccine cohort were included in this study. In post-infection samples, the ichroma inhbition rate was found to be correlated with IgG levels (ρ = 0.83), and with anti-Alpha NAbs levels (ρ = 0.78). In the vaccine cohort, a good correlation was also observed between the ichroma inhibition rate and IgG levels (ρ = 0.84), as well as NAbs against Alpha (ρ = 0.62), Delta (ρ = 0.88) and Omicron (ρ = 0.74). An ichroma inhbition rate of 77.2%, 90.8% and 99.6% accurately predicted neutralization against Alpha, Delta and Omicron variants respectively.ConclusionsThe ichroma™ COVID-19 nAb assay, with appropriate variant cut-offs, can be useful for the monitoring of anti-SARS-CoV-2 immunization and may provide a rapid prediction of protection, especially in individuals with significant levels of NAbs.

Different Neutralization Profiles After Primary SARS-CoV-2 Omicron BA.1 and BA.2 Infections.

Background and MethodsThe SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) Omicron (B.1.1.529) variant is the antigenically most distinct variant to date. As the heavily mutated spike protein enables neutralization escape, we studied serum-neutralizing activities of naïve and vaccinated individuals after Omicron BA.1 or BA.2 sub-lineage infections in live virus neutralization tests with Omicron BA.1, Omicron BA.2, wildtype (WT, B1.1), and Delta (B.1.617.2) strains. Serum samples obtained after WT infections and three-dose mRNA vaccinations with and without prior infection were included as controls.ResultsPrimary BA.1 infections yielded reduced neutralizing antibody levels against WT, Delta, and Omicron BA.2, while samples from BA.2-infected individuals showed almost no cross-neutralization against the other variants. Serum neutralization of Omicron BA.1 and BA.2 variants was detectable after three-dose mRNA vaccinations, but with reduced titers. Vaccination-breakthrough infections with either Omicron BA.1 or BA.2, however, generated equal cross-neutralizing antibody levels against all SARS-CoV-2 variants tested.ConclusionsOur study demonstrates that although Omicron variants are able to enhance cross-neutralizing antibody levels in pre-immune individuals, primary infections with BA.1 or BA.2 induced mostly variant-specific neutralizing antibodies, emphasizing the differently shaped humoral immunity induced by the two Omicron variants. These data thus contribute substantially to the understanding of antibody responses induced by primary Omicron infections or multiple exposures to different SARS-CoV-2 variants and are of particular importance for developing vaccination strategies in the light of future emerging variants.

Evidence of Neutralizing and Non-Neutralizing Anti-Glucosaminidase Antibodies in Patients With S. Aureus Osteomyelitis and Their Association With Clinical Outcome Following Surgery in a Clinical Pilot.

Staphylococcus aureus osteomyelitis remains a very challenging condition; recent clinical studies have shown infection control rates following surgery/antibiotics to be ~60%. Additionally, prior efforts to produce an effective S. aureus vaccine have failed, in part due to lack of knowledge of protective immunity. Previously, we demonstrated that anti-glucosaminidase (Gmd) antibodies are protective in animal models but found that only 6.7% of culture-confirmed S. aureus osteomyelitis patients in the AO Clinical Priority Program (AO-CPP) Registry had basal serum levels (>10 ng/ml) of anti-Gmd at the time of surgery (baseline). We identified a small subset of patients with high levels of anti-Gmd antibodies and adverse outcomes following surgery, not explained by Ig class switching to non-functional isotypes. Here, we aimed to test the hypothesis that clinical cure following surgery is associated with anti-Gmd neutralizing antibodies in serum. Therefore, we first optimized an in vitro assay that quantifies recombinant Gmd lysis of the M. luteus cell wall and used it to demonstrate the 50% neutralizing concentration (NC50) of a humanized anti-Gmd mAb (TPH-101) to be ~15.6 μg/ml. We also demonstrated that human serum deficient in anti-Gmd antibodies can be complemented by TPH-101 to achieve the same dose-dependent Gmd neutralizing activity as purified TPH-101. Finally, we assessed the anti-Gmd physical titer and neutralizing activity in sera from 11 patients in the AO-CPP Registry, who were characterized into four groups post-hoc. Group 1 patients (n=3) had high anti-Gmd physical and neutralizing titers at baseline that decreased with clinical cure of the infection over time. Group 2 patients (n=3) had undetectable anti-Gmd antibodies throughout the study and adverse outcomes. Group 3 (n=3) had high titers +/− neutralizing anti-Gmd at baseline with adverse outcomes. Group 4 (n=2) had low titers of non-neutralizing anti-Gmd at baseline with delayed high titers and adverse outcomes. Collectively, these findings demonstrate that both neutralizing and non-neutralizing anti-Gmd antibodies exist in S. aureus osteomyelitis patients and that screening for these antibodies could have a value for identifying patients in need of passive immunization prior to surgery. Future prospective studies to test the prognostic value of anti-Gmd antibodies to assess the potential of passive immunization with TPH-101 are warranted.

Updated International Society of Geriatric Oncology COVID-19 working group recommendations on COVID-19 vaccination among older adults with cancer

Updated International Society of Geriatric Oncology COVID-19 working group recommendations on COVID-19 vaccination among older adults with cancer

Neutralization of Omicron sublineages and Deltacron SARS-CoV-2 by three doses of BNT162b2 vaccine or BA.1 infection

ABSTRACT Distinct SARS-CoV-2 Omicron sublineages have evolved showing increased fitness and immune evasion than the original Omicron variant BA.1. Here, we report the neutralization activity of sera from BNT162b2 vaccinated individuals or unimmunized Omicron BA.1-infected individuals against Omicron sublineages and “Deltacron” variant (XD). BNT162b2 post-dose 3 immune sera neutralized USA-WA1/2020, Omicron BA.1-, BA.2-, BA.2.12.1-, BA.3-, BA.4/5-, and XD-spike SARS-CoV-2s with geometric mean titres (GMTs) of 1335, 393, 298, 315, 216, 103, and 301, respectively; thus, BA.4/5 SARS-CoV-2 spike variant showed the highest propensity to evade vaccine neutralization compared to the original Omicron variants BA.1. BA.1-convalescent sera neutralized USA-WA1/2020, BA.1-, BA.2-, BA.2.12.1-, BA.3-, BA.4/5-, and Deltacron-spike SARS-CoV-2s with GMTs of 15, 430, 110, 109, 102, 25, and 284, respectively. The unique mutation F486V in the BA.4/5 spike contributes to the increased evasion of antibody neutralization by sublineage BA.4/5. The low neutralization titres of vaccinated sera or convalescent sera from BA.1 infected individuals against the emerging and rapidly spreading Omicron BA.4/5 variants provide important results for consideration in the selection of an updated vaccine in the current Omicron wave. Trial registration: ClinicalTrials.gov; identifier: NCT04368728.

An In Vitro Microneutralization Assay for Influenza Virus Serology.

Influenza is an infectious respiratory disease with significant morbidity and mortality rates among people of all ages. Influenza viruses spread and evolve rapidly in the human population. Different immune histories, given by previous exposures to influenza virus infections and/or vaccinations, result in a great diversity of humoral and cellular immune responses. Understanding protective immune responses induced against circulating virus strains and potential pandemic strains is vital for infection prevention and disease mitigation. Vaccine formulations for seasonal influenza must be reformulated annually to stay abreast of occurring virus mutations. Assays to measure the capacity of antibodies to neutralize influenza viruses provide a good estimate of protection against future infections with strains similar or identical to those used in the assay. Here, we describe a detailed protocol of our standard in vitro microneutralization assay to assess the neutralization activity of polyclonal sera or purified monoclonal antibodies. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC.This article was corrected on 27 August 2022. See the end of the full text for details. Basic Protocol: Microneutralization assay to assess virus inhibition by serum or monoclonal antibodies Support Protocol 1: Preparation of cDMEM Support Protocol 2: Preparation and aliquoting of TPCK‐treated trypsin Support Protocol 3: Inactivation of serum samples by RDE treatment

Pre and Post-Monoclonal Infusion Neutralizing Activity in a Subgroup of Patients Treated in the Presence of two SARS-CoV-2 Dominant Variant of Concern (VOCs) and an Ongoing Vaccination. Overall Clinical Efficacy of Two Monoclonal Antibodies Association in Umbria.

Background and ObjectiveIn patients with mild-to-moderate COVID-19 and at high risk of progression, casirivimab/imdevimab and bamlanivimab/etesivimab were utilized in Umbria from late April to November 2021. This period was characterized by an initial prevalence of alpha (B1.1.1.7) and its progressive substitution with the delta variant (B1.617.2). Many delta infections occurred in patients already recently vaccinated.Our study aimed to observe the clinical outcome of patients treated with mAbs associations in a subgroup in which viral isolation was obtained, the pre and post-infusion neutralizing antibody activity against their viral isolate.MethodsIn this retrospective observational study, the clinical outcome before and 30 days after infusion, the baseline neutralizing activity of sera against their viral isolate, and the titers of neutralizing antibodies (NAbTs) one-hour post-infusion relative to the type of mAbs associations were evaluated.ResultsBetter efficacy of the mAbs combinations relative to monotherapy regarding global hospitalization (p = 0.021) and 30 days symptoms (p<0.001) were seen. Infections after vaccination mostly occurred in the absence of neutralizing antibody titers (NAbT). SARS-CoV-2 delta variants were isolated within 2–4 months from vaccinations without NAbTs, or in the presence of high specific neutralizing activity after 5–6 months. NAbTs were higher after casirivimab/imdevimab infusion (p=0.001).ConclusionsAlpha infections occurred prevalently in unvaccinated patients or after 5–6 months, while delta infections prevailed in vaccinated ones. A poor neutralizing activity in most of these patients was seen. A higher NAbT after infusion of casirivimab/imdevimab was observed.