Cross-reactive Antibodies Research Articles

Beta-variant recombinant SARS CoV-2 vaccine induces durable cross-reactive antibodies against Omicron BA variants

BackgroundWe previously reported the safety and immunogenicity data from a randomized trial comparing the booster responses of vaccinees who received monovalent (MV) recombinant protein Beta-variant (MVB.1.351) and MV ancestral protein (MVD614) vaccines with AS03 adjuvant (Sanofi/GSK) to booster response of vaccinees who received mRNA MV ancestral strain BNT162b2 vaccine (Pfizer-BioNTech).MethodsFirst booster of the vaccines was administered in adult participants previously primed with 2 doses of MV ancestral strain BNT162b2. A subset of these participants with available blood samples collected at Day 0 (D0), at 28 days (D28), and 3 months (M3) post-booster were contacted for additional testing (195/208 participants). The persistence of cross-neutralizing antibodies, including against Omicron BA.1 and BA.4/5, up to 3 months after boosting was evaluated using a validated pseudovirus neutralization assay.ResultsAcross the whole population, MVB.1.351 vaccine induces highest NAbs titers against Omicron BA.1 and BA.4/5 variants at D28 and M3 post-booster. In participants with SARS-CoV-2 infection between D28 and M3, both MVB.1.351 and BNT162b2 vaccine groups show an increase in GMTs against Omicron BA.1 and Omicron BA.4/5 following infection. Among uninfected participants, the ratio of M3 to D28 GMTs was higher for the MVB.1.351 group than the BNT162b2 group against Omicron BA.1 (0.64 [0.53;0.77] versus 0.43 [0.35;0.53]), Omicron BA.4/5 (0.61 [0.50; 0.75] versus 0.44 [0.34; 0.56]), and D614 (0.68 [0.58,0.81] versus 0.46 [0.39,0.55]).ConclusionsThe MVB.1.351 vaccine induces higher and durable cross-neutralizing antibodies against Omicron subvariants up to 3 months after boosting compared to an MV ancestral and mRNA BNT162b2 booster vaccine.

Rational selection of TbpB variants yields a bivalent vaccine with broad coverage against Neisseria gonorrhoeae

Neisseria gonorrhoeae is an on-going public health problem due in part to the lack of success with efforts to develop an efficacious vaccine to prevent this sexually transmitted infection. The gonococcal transferrin binding protein B (TbpB) is an attractive candidate vaccine antigen. However, it exhibits high levels of antigenic variability, posing a significant obstacle in evoking a broadly protective immune response. Here, we utilize phylogenetic information to rationally select TbpB variants for inclusion into a gonococcal vaccine and identify two TbpB variants that together elicit a highly cross-reactive antibody response against a diverse panel of TbpB variants and clinically relevant gonococcal strains. This formulation performed well in experimental proxies of real-world usage, including eliciting bactericidal activity against diverse gonococcal strains and decreasing the median duration of colonization after vaginal infection in female mice. These data support the use of a combination of TbpB variants for a broadly protective gonococcal vaccine.

Spatiotemporal Dynamic Immunomodulation by Infection-Mimicking Gels Enhances Broad and Durable Protective Immunity Against Heterologous Viruses.

Despite their safety and widespread use, conventional protein antigen-based subunit vaccines face significant challenges such as low immunogenicity, insufficient long-term immunity, poor CD8+ T-cell activation, and poor adaptation to viral variants. To address these issues, an infection-mimicking gel (IM-Gel) is developed that is designed to emulate the spatiotemporal dynamics of immune stimulation in acute viral infections through in situ supramolecular self-assembly of nanoparticulate-TLR7/8a (NP-TLR7/8a) and an antigen with tannic acid (TA). Through collagen-binding properties of TA, the IM-Gel enables sustained delivery and enhanced retention of NP-TLR7/8a and protein antigen in the lymph node subcapsular sinus of mice for over 7 days, prolonging the exposure of vaccine components in both B cell and T cell zones, leading to robust humoral and cellular responses. The IM-Gel system with the influenza A antigen confers cross-protection against multiple influenza subtypes (H1N1, H5N2, H3N2, H7N3, and H9N2) with long-term immune responses. Combination of the IM-Gel with the SARS-CoV-2 spike protein also elicits strong cross-reactive antibody responses against multiple SARS-CoV-2 variants (Alpha, Beta, NY510+D614G, Gamma, Kappa, and Delta). The IM-Gel, as a programmable immunomodulatory material, provides a vaccine design principle for the development of next-generation universal vaccines that can elicit broad and durable protective immunity against emerging viruses.

Expert consensus on the benefits of neuraminidase in conventional influenza vaccines: a Delphi study

BackgroundSeasonal vaccination is the mainstay of human influenza prevention. Licensed influenza vaccines are regularly updated to account for viral mutations and antigenic drift and are standardised for their haemagglutinin content. However, vaccine effectiveness remains suboptimal. Neuraminidase (NA) evolves more gradually than hemagglutinin and has been demonstrated to provide added clinical benefits. However, NA is not currently a mandated or standardised component of influenza vaccines.MethodsHere, we collated expert opinions on the importance of NA in influenza vaccines in a two-stage Delphi survey. Nine statements about NA were formulated by a steering committee based on a targeted literature review. In the survey’s first round, panellists recruited from three continents were requested to report on their agreement with each statement and estimate the strength of evidence for each statement. Panellists were also requested to explain their choice of answer and suggest revisions to the statements. Consensus was considered reached if ≥ 75% of panellists agreed with a statement. If consensus was not reached for a statement, this statement was revised and included in the survey’s second round.ResultsNine panellists with a broad range of NA-related expertise, including clinical, research, and public health experience, completed the survey. They agreed that anti-NA responses acquired via natural infection or vaccination are associated with protective immunity independently of haemagglutinin and that NA provided additional advantages including improving disease severity metrics. The experts identified several knowledge gaps concerning heterologous cross-reactivity of vaccine-induced anti-NA antibodies, correlations between anti-NA titres and reduced transmission or infection risks, and differences in anti-NA responses to seasonal influenza vaccines.ConclusionsNA is an important influenza vaccine component and is associated with specific benefits. These benefits would likely be greater if NA content were standardised. Additional research is needed to optimise vaccines for anti-NA effects.

Structural determinants of peanut induced anaphylaxis.

Human monoclonal IgE antibodies recognizing peanut allergens have recently become available, but we lack a detailed understanding of how these IgEs target allergens. To determine the molecular details of the antibody-allergen interaction for a panel of clinically important human IgE monoclonal antibodies and to develop strategies to disrupt disease causing antibody-allergen interactions. We identified candidates from a panel of epitope binned human IgE monoclonals that recognize two important and homologous peanut allergens, Ara h 2 and Ara h 6. Crystal structures were determined revealing the interfaces (antigenic sites) of exemplars of five common IgE bins. Among the common antigenic sites on Ara h 2 and Ara h 6, two sites (A and B) are highly conserved between the allergens, explaining the cross reactivity of antibodies that recognize these sites. Three sites (C, D, and F) involve residues that are not conserved between the allergens. Of the five common sites, three Sites (B, C, and D) involve residues that are only near each other when the allergens are properly folded, such that these sites are conformational. Two additional sites (sites A and F) involve largely linear stretches of amino acids. Site F targeted antibody, 38B7, binds to a peptide sequence DPYSPOHS, in which hydroxylation of the last proline is critical for binding. This sequence is repeated two or three times depending on the Ara h 2 isoform, enabling 38B7 to induce anaphylaxis as a single monoclonal, without a second antibody. We have mutated key residues in each site and created a panel of hypoallergens, having reduced IgE mAb binding and lacking the ability to induce anaphylaxis in our murine model. We created a structural map of the IgE antibody response to the most important peanut allergen proteins to enable the design of new allergy immunotherapies and vaccines.

Influenza A Virus H7 nanobody recognizes a conserved immunodominant epitope on hemagglutinin head and confers heterosubtypic protection

Influenza remains a persistent global health challenge, largely due to the virus’ continuous antigenic drift and occasional shift, which impede the development of a universal vaccine. To address this, the identification of broadly neutralizing antibodies and their epitopes is crucial. Nanobodies, with their unique characteristics and binding capacity, offer a promising avenue to identify such epitopes. Here, we isolate and purify a hemagglutinin (HA)-specific nanobody that recognizes an H7 subtype of influenza A virus. The nanobody, named E10, exhibits broad-spectrum binding, cross-group neutralization and in vivo protection across various influenza A subtypes. Through phage display and in vitro characterization, we demonstrate that E10 specifically targets an epitope on HA head which is part of the conserved lateral patch and is highly immunodominant upon H7 infection. Importantly, immunization with a peptide including the E10 epitope elicits cross-reactive antibodies and mediates partial protection from lethal viral challenge. Our data highlights the potential of E10 and its associated epitope as a candidate for future influenza prevention strategies.

Cross-reactive sarbecovirus antibodies induced by mosaic RBD-nanoparticles.

Therapeutic monoclonal antibodies (mAbs) against SARS-CoV-2 become obsolete as spike substitutions reduce antibody binding. To induce antibodies against conserved receptor-binding domain (RBD) regions for protection against SARS-CoV-2 variants of concern and zoonotic sarbecoviruses, we developed mosaic-8b RBD-nanoparticles presenting eight sarbecovirus RBDs arranged randomly on a 60-mer nanoparticle. Mosaic-8b immunizations protected animals from challenges from viruses whose RBDs were matched or mismatched to those on nanoparticles. Here, we describe neutralizing mAbs from mosaic-8b-immunized rabbits, some on par with Pemgarda (the only currently FDA-approved therapeutic mAb). Deep mutational scanning, in vitro selection of spike resistance mutations, and cryo-EM structures of spike-antibody complexes demonstrated targeting of conserved epitopes. Rabbit mAbs included critical D-gene segment features in common with human anti-RBD mAbs, despite rabbit genomes lacking an equivalent human D-gene segment. Thus, mosaic RBD-nanoparticle immunization coupled with multiplexed screening represent an efficient way to generate and select therapeutic pan-sarbecovirus and pan-SARS-2 variant mAbs.

Targets and mechanisms of neutralizing monoclonal antibodies against Dengue virus

Dengue fever is a mosquito-borne disease prevalent in tropical and subtropical regions, with its prevalence expanding due to increased global travel. The dengue virus, the causative agent of dengue fever, often co-circulates in the form of four distinct serotypes. Cross-reactive antibodies generated during a primary infection pose a significant risk during secondary infections with different serotypes, and fully protective vaccines and antiviral drugs are yet to be developed. Over the past decade, advances in antibody technology have led to the isolation of numerous monoclonal antibodies against dengue virus, with their neutralizing epitopes elucidated through structure-based analyses. This review highlights the key epitopes associated with neutralizing antibodies against dengue virus and discusses their potential applications in vaccine design and therapeutic antibody development. This review helps systematically summarize the progress in dengue virus neutralizing antibody research, providing a theoretical foundation and technical guidance for the development of novel vaccines and antibody therapeutics.

Guillain-Barré syndrome.

Guillain-Barré syndrome (GBS) is a rare immune-mediated polyradiculoneuropathy. Patients typically develop rapidly progressive weakness and sensory deficits that can result in complete paralysis requiring mechanical ventilation. GBS is usually a monophasic disease in which an aberrant immune response to an infection or other trigger damages the peripheral nerves. For example, in patients with preceding Campylobacter jejuni infection, molecular mimicry causes a cross-reactive antibody response to nerve gangliosides. Diagnosis is based on clinical features, supported by cerebrospinal fluid analysis and nerve conduction studies. Effective treatments include plasma exchange and intravenous immunoglobulins. However, ~20% of patients who received treatment are unable to walk after 6 months and ~5% die as a consequence of GBS. Important knowledge gaps in GBS include its pathogenesis, especially after viral infections. In addition, there is a lack of specific biomarkers to improve thediagnosis, monitor thedisease activity, and predict the clinical course and outcome of GBS. Major challenges for the future include finding more effective and personalized treatments, which are affordable in low-income and middle-income countries, and preparation for outbreaks of infections as potential triggers for GBS.

Measurement of Serum Free Vitamin D Concentrations: Importance, Challenges, and the Emerging Role of Mass Spectrometry.

Serum total 25-hydroxyvitamin D [25(OH)D] concentration is the most widely used clinical biomarker for vitamin D status. Under certain physiological and pathological conditions, however, total 25(OH)D may not always be the best index for vitamin D status. Instead, the nonprotein-bound (free) fraction of total 25(OH)D has been suggested as a more appropriate marker in certain clinical situations. Free 25(OH)D levels can either be calculated or measured directly. Calculated free 25(OH)D depends on the concentrations of total serum 25(OH)D, vitamin D binding protein (VDBP), and albumin, as well as the affinity between analyte and binding proteins. Differences in VDBP concentrations are observed between populations as a result of health status, gene polymorphisms, and the assay used for determination. Direct measurement methods for free 25(OH)D are often complicated (dialysis, ultrafiltration) or susceptible to interferences, cross-reactivity, and type of antibody (immunoassays). Therefore, it is very important to develop tools that allow either accurate and precise measurement of VDBP or direct measurement of free 25(OH)D. For the latter, liquid chromatography combined with tandem mass spectrometry (LC-MS/MS) has recently shown promise for analysis of free vitamin D. In the current review, we present the importance and challenges regarding free 25(OH)D determination and the role of LC-MS-based methods in future studies. More research is required to determine the role of free 25(OH)D in the assessment of vitamin D status in healthy subjects and in various clinical conditions. Recent advances in technology, including mass spectrometry, can provide the required assays for this purpose.

Multiplex sample-sparing assay for detecting type-specific antibodies to Zika and dengue viruses: an assay development and validation study

Serology for dengue viruses (DENV) and Zika virus (ZIKV) has been hindered by antibody cross-reactivity, which limits the utility of these tests for surveillance and assessment of sero-status. Our aim was to develop a multiplexed IgG-based assay with increased accuracy to assess the history of previous DENV and ZIKV infections. We developed and assessed the analytical performance of a sample-sparing, multiplexed, microsphere-based serological assay using domain III of the envelope protein (EDIII) of DENV serotypes 1-4 and ZIKV, the most variable region between each virus. We used a reference panel of well-characterised serum samples from US-based travellers or residents of southeast Asia, central America, or Puerto Rico, who were naive or immune to either or both DENV and ZIKV, to develop an algorithm for detecting previous exposure to DENV and ZIKV and identify optimal positivity cutoffs to maximise assay performance. To independently confirm the performance of the assay and algorithm, we used a second test set of previously collected samples from healthy children (aged 9-16years) living in Puerto Rico, whose DENV and ZIKV serostatus had been defined using the gold-standard virus neutralisation assay. Weevaluated the performance of the multiplex assay compared with the gold-standard assay by estimating sensitivity and specificity for identification of past exposure to ZIKV and DENV. The multiplexed EDIII assay showed reproducible results over different days and a linearity range from μg to pg levels for various EDIII antigens. Using a reference panel of serum samples from individuals who were DENV naive (n=136), DENV immune (n=38), ZIKV naive (n=67), and ZIKV immune (n=28), we optimised the assay and developed a testing algorithm that was 94·9% (95% CI 83·1-99·1) sensitive and 97·1% (92·7-98·9) specific for identifying previous exposure to DENV, and 100% (95% CI 88·0-100) sensitive and 97·0% (89·8-99·5) specific for identifying previous exposure to ZIKV. In an analysis with an independent test set of 389samples, the assay and algorithm had 94·2% (89·9-97·1) sensitivity and 92·9% (87·3-96·5) specificity for DENV, and 94·1% (88·7-97·4) sensitivity and 95·0% (90·0-98·0) specificity for ZIKV. The multiplexed EDIII serology assay can accurately identify the history of previous infection with either DENV or ZIKV. This high-throughput and sample-sparing assay is a promising new tool for supporting flavivirus surveillance, epidemiological and clinical studies, and serological testing for dengue vaccine eligibility. Further studies are needed to reduce the cost of the assay, eliminate high background in some samples, and to assess performance in DENV-endemic and ZIKV-endemic countries. US National Institutes of Health.

Role of route of delivery on Chlamydia abortus vaccine-induced immune responses and genital tract immunity in mice.

We investigated if the efficacy of a Chlamydia abortus (Cab) subunit vaccine is influenced by route of administration. Thus, female CBA/J mice were immunized either by mucosal or systemic routes with Vibrio cholerae ghost (VCG)-based vaccine expressing T and B cell epitopes of Cab polymorphic membrane protein (Pmp) 18D, termed rVCG-Pmp18.3. Vaccine evaluation revealed that all routes of vaccine delivery induced a Th1-type antibody response after a prime boost or three-dose immunization regimen. Also, the intranasal and rectal mucosal and intramuscular systemic routes induced cross-reactive neutralizing antibodies against homologous and heterologous Cab strains. Irrespective of the route of immunization, the vaccine elicited a Th1-type cytokine response (IFN-γ/IL-4 >1) in immunized mice. Analysis of reduction in genital Cab burden as an index of protection showed that immunization induced substantial degrees of protection against infection, irrespective of route of delivery with the intranasal and rectal mucosal routes showing superior levels of protection 12 days postchallenge. Furthermore, there was correlation between the humoral and cellular immune response and protection was associated with the Cab-specific serum IgG antibody avidity and IFN-γ. Thus, while route of administration impacts vaccine efficacy, the rVCG-Pmp18.3-induced protective immunity against Cab respiratory infection can be accomplished by both mucosal and systemic immunization.

SARS-CoV-2 Omicron XBB infections boost cross-variant neutralizing antibodies, potentially explaining the observed delay of the JN.1 wave in some Brazilian regions

ObjectivesThe SARS-CoV-2 JN.1 lineage emerged in late 2023 and quickly replaced the XBB lineages, becoming the predominant Omicron variant worldwide in 2024. We estimate the epidemiological impact of this SARS-CoV-2 lineage replacement in Brazil and we further assessed the cross-reactive neutralizing antibody (NAb) responses in a cohort of convalescent Brazilian patients infected during 2023. MethodsWe analyzed the evolution of SARS-CoV-2 lineages and severe acute respiratory infection (SARI) cases in Brazil between July 2023 and March 2024. We evaluated the cross-reactive NAb responses to the JN.1 variant in a cohort of convalescent Brazilian patients, both before and after infection with XBB.1* lineages. ResultsJN.1 replaced XBB with similar temporal dynamics across all country regions, though its epidemiological impact varied between locations. The Southeastern, Southern, and Central-Western regions experienced a brief XBB wave around October 2023, shortly before the introduction of JN.1, without any immediate upsurge of SARI cases during viral lineage replacement. By contrast, the Northeastern and Northern regions did not experience an XBB wave in the latter half of 2023 and displayed a rapid surge in SARI cases driven by the emergence of the JN.1. We found that recent XBB infections in the Brazilian population significantly boosted cross-reactive NAb levels against JN.1. ConclusionsThe XBB wave observed in the second half of 2023 in some Brazilian states likely acted as a booster for population immunity, providing short-term protection against JN.1 infections and delaying the rise of SARI cases in certain regions of the country.

Igome Graphs Suggest the Changes in the IgM and IgG Repertoires in Antiphospholipid Syndrome Are in Part Idiotypically Defined

Antiphospholipid Syndrome (APS) is characterized by the persistence of high-affinity antiphospholipid antibodies, manifesting clinically as pregnancy complications, thrombosis, or neurological symptoms. This study explores the changes in the IgM and IgG antibody repertoires in APS patients using igome graphs, which represent antibody repertoires through peptide libraries selected from phage display on the complete immunoglobulin fraction of the serum. Serum samples from healthy women and APS patients were processed to isolate IgM and IgG fractions, which were then used for phage selection and next-generation sequencing. Peptide sequences were analyzed using graph representation, clustering, and spectral embedding to identify significant differences between the repertoires. The study revealed that while IgM repertoires in APS patients exhibit a loss of public reactivities, the IgG repertoires do not follow this trend. Three orthogonal sequence motifs were identified in the IgM and IgG repertoires, suggesting potential idiotypic interactions. These findings highlight the intricate mechanisms of antibody selection and cross-reactivity in APS, offering insights into potential therapeutic approaches. The study underscores the importance of system-level analysis in understanding immune mechanisms and suggests that idiotypic interactions, though complex, could play a crucial role in APS pathogenesis.

Structural characterization of human monoclonal antibodies targeting uncommon antigenic sites on spike glycoprotein of SARS-CoV.

The function of the spike protein N terminal domain (NTD) in coronavirus (CoV) infections is poorly understood. However, some rare antibodies that target the SARS-CoV-2 NTD potently neutralize the virus. This finding suggests the NTD may contribute in part to protective immunity. Pan-sarbecovirus antibodies are desirable for broad protection, but the NTD region of SARS-CoV and SARS-CoV-2 exhibit a high level of sequence divergence, and therefore, cross-reactive NTD-specific antibodies are unexpected, and there is no structure of a SARS-CoV NTD-specific antibody in complex with NTD. Here we report a monoclonal antibody COV1-65 encoded by the IGHV1-69 gene that recognizes the NTD of SARS-CoV S protein. A prophylaxis study showed the MAb COV1-65 prevented disease when administered before SARS-CoV challenge of BALB/c mice, an effect that requires intact Fc effector functions for optimal protection in vivo. The footprint on the S protein of COV1-65 is near to functional components of the S2 fusion machinery, and the selection of COV1-65 escape mutant viruses identified critical residues Y886H and Q974H, which likely affect the epitope through allosteric effects. Structural features of the mAb COV1-65-SARS-CoV antigen interaction suggest critical antigenic determinants that should be considered in the rational design of sarbecovirus vaccine candidates.

Development of a new genotype-phenotype linked antibody screening system.

Antibodies are powerful tools for the therapy and diagnosis of various diseases. In addition to conventional hybridoma-based screening, recombinant antibody-based screening has become a common choice; however, its application is hampered by two factors: (1) screening starts after Ig gene cloning and recombinant antibody production only, and (2) the antibody is composed of paired chains, heavy and light, commonly expressed by two independent expression vectors. Here, we introduce a method for the rapid screening of recombinant monoclonal antibodies by establishing a Golden Gate-based dual-expression vector and in-vivo expression of membrane-bound antibodies. Using this system, we demonstrate the rapid isolation of influenza cross-reactive antibodies with high affinity from immunized mice within 7 days. This system is particularly useful for isolating therapeutic or diagnostic antibodies, for example during foreseen pandemics.

Development of a new genotype–phenotype linked antibody screening system

Antibodies are powerful tools for the therapy and diagnosis of various diseases. In addition to conventional hybridoma-based screening, recombinant antibody-based screening has become a common choice; however, its application is hampered by two factors: (1) screening starts after Ig gene cloning and recombinant antibody production only, and (2) the antibody is composed of paired chains, heavy and light, commonly expressed by two independent expression vectors. Here, we introduce a method for the rapid screening of recombinant monoclonal antibodies by establishing a Golden Gate-based dual-expression vector and in-vivo expression of membrane-bound antibodies. Using this system, we demonstrate the rapid isolation of influenza cross-reactive antibodies with high affinity from immunized mice within 7 days. This system is particularly useful for isolating therapeutic or diagnostic antibodies, for example during foreseen pandemics.

NHBA antibodies elicited by 4CMenB vaccination are key for serum bactericidal activity against Neisseria gonorrhoeae

The 4CMenB (BexseroR) vaccine contains detergent-extracted outer membrane vesicles (OMVs) from a Neisseria meningitidis (Nm) group B strain NZ98/254 and three recombinant Nm protein antigens: Neisseria adhesin A (NadA), Factor H binding protein (FHbp, as the C-terminal protein in the GNA2091-FHbp fusion), and Neisserial Heparin Binding Antigen (NHBA, as the N-terminal protein in the NHBA-GNA1030 fusion). Previous work has shown that 4CMenB generates serum antibodies to Nm and Neisseria gonorrhoeae (Ng) OMV proteins and lipooligosaccharide (LOS). Mounting evidence indicates 4CMenB can partially protect against mucosal infections with Ng. The immunologic basis for Ng cross protection remains to be fully elucidated. Ten paired human sera obtained pre- and post-immunization with 4CMenB (1 month after a third vaccine dose) were used in ELISAs and in Western blots to determine IgG and IgA serum responses to OMVs from Nm strain NZ98/254 (OMVNm) and two Ng strains, 1291 and CNG20 (OMVNg), and gonococcal recombinant NHBA (rNHBANg) proteins. Post 4CMenB sera, but not pre-sera, showed strong IgG and variable IgA responses to the OMVNm but lower (2–11-fold difference in signal intensity) recognition of OMVNg. All post (not pre) 4CMenB sera showed strong IgG, but variable IgA, recognition of rNHBANg by ELISAs and Western blots. Three post 4CMenB sera at 10% (v/v) concentration had serum bactericidal activity (SBA) against Ng strains 1291 and CNG20 (~30–40% killing), not seen in paired pre-sera. These data confirmed 4CMenB-induced cross-reactive functional antibody responses to Ng. In competitive SBA assays, in which sera were pre-incubated with rNHBA, minimal SBA against Nm strain NZ98/254 was titrated away. However, most of the SBA against Ng strains 1291 and CNG20 required NHBA-specific antibodies, and the Δnhba mutants were resistant to killing by post 4CMenB sera. Removing NHBA-specific and LOS-specific OMV antibodies simultaneously decreased SBA significantly more than the sum of removing individual antibodies alone, suggesting synergy between anti-NHBA and anti-OMV antibodies. Anti- NHBANm antibodies induced by 4CMenB vaccination cross react with NHBANg and substantially contribute to the bactericidal response toward Ng induced by the vaccine.

Development and Characterization of a 13-Plex Binding Assay to Detect Shigella Antibodies in Human Samples.

Shigella is the leading bacterial cause of diarrhea worldwide, with increasing levels of antibiotic resistance. The greatest burden is among children aged <5 years in low- and middle-income countries, and efforts are ongoing to develop vaccines against this pathogen. One of the challenges associated with the development of a vaccine against Shigella is the need for a multivalent vaccine covering the most prevalent Shigella serotypes. Epidemiologic studies to better understand the prevalence of the Shigella serotypes and inform vaccination schedules are very useful, with clinical data showing the ability of vaccines to elicit cross-reactive antibodies. Here, we set up a Luminex-based method able to reproducibly measure antibodies specific to 13 Shigella antigens in human sera. This method will allow the rapid collection of large amounts of data based on the analysis of serum samples from vaccinated individuals or people naturally exposed to Shigella, supporting the development of a vaccine against this disease.

Evidence of SARS-CoV-2 Spread in Rural Tanzania During the First 6 Months of the Global COVID-19 Pandemic.

In the first 6 months of the coronavirus disease 2019 pandemic, limited testing clouded understanding of the extent of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission in Africa. In particular, Tanzania halted all testing and reporting of SARS-CoV-2 cases after May 2020, not resuming until June 2021. In July-August 2020, we performed a seroprevalence survey in rural Bagamoyo district, 40 km outside Dar es Salaam. Among 347 asymptomatic children and adults, 64/347 (18.0%) demonstrated seroreactivity to SARS-CoV-2 spike receptor binding domain by ELISA. Given significant antibody cross-reactivity in malaria-endemic regions, seropositivity was additionally confirmed via a multitarget Luminex immunoassay. Thirty-seven, or 58% of initially seroreactive persons, were Luminex positive, leading to an estimated SARS-CoV-2 seroprevalence of 10.7% (37/347, 95% CI 7.6-14.4%). Working in health care appeared to be associated with seropositivity. Reporting of viral symptoms or health care-seeking behavior in the previous 3 months was not more frequent in seropositive individuals.