Improving the Immunoprotective Effect of Carbohydrate Vaccine Against Bacterial Pneumonia

High mortality rates of bacterial pneumonia and increased antibiotic resistance are major reasons to develop novel vaccine strategies against Streptococcus pneumoniae. S. pneumoniae serotype 3 (ST3) is one of the most frequent serotypes isolated from patients with invasive pneumococcal diseases, even though it is included in the routine immunization schedule. To improve the immunogenic properties of ST3, synthetic antigenic tetrasaccharide based on capsular polysaccharide repeating units have been conjugated to a carrier protein and used as a vaccine candidate. The study illustrates the principle of proper optimization of variable aspects of vaccine formulation, such as dosage, adjuvant, and carrier protein. Use of highly pure and well-characterized synthetic oligosaccharide allowed to significantly decreased the dosage of antigen while maintaining sufficient protection shown by in-vitro opsonophagocytic killing assay. In defiance of the general notion “the more, the better”, the higher dose did not improve the protective effect of immunization but could even diminish the final success of the vaccination. In order to improve the immunogenicity of semi-synthetic ST3-glycoconjugates, several commercially available adjuvants were used and incorporated into biodegradable poly-lactic-acid (PLA) microparticles. Screening experiments in mice yielded promising results for agonists of TLR7/8, namely resimiquimod (R848) and bacterial RNA, as well as MPLA, a TRIF-biased TLR4 agonist used in several commercial vaccines. The carrier protein derived from S.pneumoanie can serve as “double-action bullet”, being both a carrier essential for glycan presentation and an additional vaccine antigen providing broader protection, so-called "additional valency". Hence, ST3-tetrasaccharide was conjugated to pneumolysin and PspA protein and vaccine were evaluated in-vivo in the mouse and swine model. The mouse study showed that ST3-tetrasaccharide pneumolysin conjugates decrease the bacteria load in blood and lungs as well as reduce the disease severity in mice challenged with S.pneumoniae serotype 3. Additionally, the synthetic oligosaccharide conjugated to pneumolysin and PspA inhibited colonization of the nasopharynx after infection with bacteria. The immunization of piglets provides the first evidence for the immunogenicity of the synthetic glycoconjugate vaccine in a swine model. The generated antibodies were able to kill pneumococci and neutralize the toxic effect of pneumolysin in-vitro. However, the protective activity of the glycoconjugate vaccines in the swine in-vivo infection model has to be further investigated. The study presented in the thesis combined a series of innovations, which enhance the efficacy and applicability of glycoconjugate vaccines and help to further clarify the principles of anti-carbohydrate- and anti-bacterial immunity

Hybrid immunity expands the functional humoral footprint of both mRNA and vector-based SARS-CoV-2 vaccines

Funding Information: We thank Nancy Zimmerman, Mark and Lisa Schwartz, an anonymous donor (financial support), Terry and Susan Ragon, and the SAMANA Kay MGH Research Scholars award for support. We acknowledge support from the Ragon Institute of Mass General, MIT, and Harvard (to G.A.) the Massachusetts Consortium on Pathogen Readiness (MassCPR) (to G.A.), and the National Institutes of Health ( 3R37AI080289-11S1 , R01AI146785 , U19AI42790–01 , U19AI135995–02 , U19AI42790-01 , 1U01CA260476 – 01 , and CIVIC75N93019C00052 ) (to G.A.). Publisher Copyright: © 2023Despite the successes of current coronavirus disease 2019 (COVID-19) vaccines, waning immunity, the emergence of variants of concern, and breakthrough infections among vaccinees have begun to highlight opportunities to improve vaccine platforms. Real-world vaccine efficacy studies have highlighted the reduced risk of breakthrough infections and diseases among individuals infected and vaccinated, referred to as hybrid immunity. Thus, we sought to define whether hybrid immunity shapes the humoral immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) following Pfizer/BNT162b2, Moderna mRNA-1273, ChadOx1/AZD1222, and Ad26.COV2.S vaccination. Each vaccine exhibits a unique functional humoral profile in vaccination only or hybrid immunity. However, hybrid immunity shows a unique augmentation of S2-domain-specific functional immunity that was poorly induced for the vaccination only. These data highlight the importance of natural infection in breaking the immunodominance away from the evolutionarily unstable S1 domain and potentially affording enhanced cross-variant protection by targeting the more highly conserved S2 domain of SARS-CoV-2.publishersversionPeer reviewe

Hybrid immunity expands the functional humoral footprint of both mRNA and vector-based SARS-CoV-2 vaccines

Despite the successes of current coronavirus disease 2019 (COVID-19) vaccines, waning immunity, the emergence of variants of concern, and breakthrough infections among vaccinees have begun to highlight opportunities to improve vaccine platforms. Real-world vaccine efficacy studies have highlighted the reduced risk of breakthrough infections and diseases among individuals infected and vaccinated, referred to as hybrid immunity. Thus, we sought to define whether hybrid immunity shapes the humoral immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) following Pfizer/BNT162b2, Moderna mRNA-1273, ChadOx1/AZD1222, and Ad26.COV2.S vaccination. Each vaccine exhibits a unique functional humoral profile in vaccination only or hybrid immunity. However, hybrid immunity shows a unique augmentation of S2-domain-specific functional immunity that was poorly induced for the vaccination only. These data highlight the importance of natural infection in breaking the immunodominance away from the evolutionarily unstable S1 domain and potentially affording enhanced cross-variant protection by targeting the more highly conserved S2 domain of SARS-CoV-2

SARS-CoV-2 mRNA vaccination elicits robust antibody responses in children

Publisher Copyright: Copyright © 2022 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY)Although children have been largely spared from coronavirus disease 2019 (COVID-19), the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) with increased transmissibility, combined with fluctuating mask mandates and school reopenings, has led to increased infections and disease among children. Thus, there is an urgent need to roll out COVID-19 vaccines to children of all ages. However, whether children respond equivalently to adults to mRNA vaccines and whether dosing will elicit optimal immunity remain unclear. Here, we aimed to deeply profile the vaccine-induced humoral immune response in 6- to 11-year-old children receiving either a pediatric (50 μg) or adult (100 μg) dose of the mRNA-1273 vaccine and to compare these responses to vaccinated adults, infected children, and children who experienced multisystem inflammatory syndrome in children (MIS-C). Children elicited an IgG-dominant vaccine-induced immune response, surpassing adults at a matched 100-μg dose but more variable immunity at a 50-μg dose. Irrespective of titer, children generated antibodies with enhanced Fc receptor binding capacity. Moreover, like adults, children generated cross-VOC humoral immunity, marked by a decline of omicron-specific receptor binding domain, but robustly preserved omicron spike protein binding. Fc receptor binding capabilities were also preserved in a dose-dependent manner. These data indicate that both the 50- and 100-μg doses of mRNA vaccination in children elicit robust cross-VOC antibody responses and that 100-μg doses in children result in highly preserved omicron-specific functional humoral immunity.publishersversionPeer reviewe

mRNA vaccine boosting enhances antibody responses against SARS-CoV-2 Omicron variant in individuals with antibody deficiency syndromes

Individuals with primary antibody deficiency (PAD) syndromes have poor humoral immune responses requiring immunoglobulin replacement therapy. We followed individuals with PAD after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination by evaluating their immunoglobulin replacement products and serum for anti-spike binding, Fcγ receptor (FcγR) binding, and neutralizing activities. The immunoglobulin replacement products tested have low anti-spike and receptor-binding domain (RBD) titers and neutralizing activity. In coronavirus disease 2019 (COVID-19)-naive individuals with PAD, anti-spike and RBD titers increase after mRNA vaccination but wane by 90 days. Those vaccinated after SARS-CoV-2 infection develop higher and more sustained responses comparable with healthy donors. Most vaccinated individuals with PAD have serum-neutralizing antibody titers above an estimated correlate of protection against ancestral SARS-CoV-2 and Delta virus but not against Omicron virus, although this is improved by boosting. Thus, some immunoglobulin replacement products likely have limited protective activity, and immunization and boosting of individuals with PAD with mRNA vaccines should confer at least short-term immunity against SARS-CoV-2 variants, including Omicron

Janus Emulsions for the Detection of Bacteria

Janus emulsion assays that rely on carbohydrate-lectin binding for the detection of Escherichia coli bacteria are described. Surfactants containing mannose are self-assembled at the surface of Janus droplets to produce particles with lectin binding sites. Janus droplets orient in a vertical direction as a result of the difference in densities between the hydrocarbon and fluorocarbon solvents. Binding of lectin to mannose(s) causes agglutination and a tilted geometry. The distinct optical difference between naturally aligned and agglutinated Janus droplets produces signals that can be detected quantitatively. The Janus emulsion assay sensitively and selectively binds to E. coli at 10 4 cfu/mL and can be easily prepared with long-time stability. It provides the basis for the development of inexpensive portable devices for fast, on-site pathogen detection

Tuberculin skin test reaction is related to memory, but not naive CD4+ T cell responses to mycobacterial stimuli in BCG-vaccinated young adults

Appendix A. Supplementary materialInternational audienceBacillus Calmette-Guérin (BCG) is the only vaccine available against tuberculosis and the tuberculin skin test (TST) is the most widely used method to detect BCG take. However, subjects may remain TST-negative, even after several BCG administrations. To investigate some of the potential reasons underlying this inability of developing tuberculin sensitivity in response to BCG we compared the effect of different mycobacterial stimuli in the groups differently responding to tuberculin. TST was performed on 71 healthy adults aged 25-30 years, who had received BCG in their childhood, and considered TST-positive at ≥10 mm. Dendritic cells (DCs) were incubated with PPD, live BCG or rBCGhIL-18, producing human IL-18. The latter strain was used to investigate whether the production of IL-18 could overcome some of the immune read-out limitations in the TST-negative subjects. CD86, CD80, CD40, and DC-specific intracellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN) expression was analysed by flow cytometry and IL-10, IL-23 and IP-10 secretion in culture supernatants by ELISA. In DCs-T cell co-cultures with naive and memory CD4+ T cells, the IFN-γ and IL-10 levels were determined by ELISA. We found no difference in IL-10 and IFN-γ production by naive T cells between the TST-negative and TST-positive subjects. However, IFN-γ was produced in significantly higher amounts by memory T cells incubated with PPD, BCG or rBCGhIL-18-pulsed DCs in TST-positive than in TST-negative subjects, whereas the numbers of the IFN-γ-producing T cells were similar in both groups. This difference may be partially due to a decreased CD40 and enhanced reduction in DC-SIGN expression by DCs of TST-negative versus TST-positive subjects. A strong effect of IL-18 expression by rBCGhIL-18 on IL-23 production by the DC was seen in both groups, which likely was the reason for the increased IFN-γ production by naïve T cells upon incubation with mycobacteria-pulsed DC, regardless of the TST status

Development of an Efficacious, Semisynthetic Glycoconjugate Vaccine Candidate against <i>Streptococcus pneumoniae</i> Serotype 1

Infections with <i>Streptococcus pneumoniae</i> are a major health burden. Glycoconjugate vaccines based on capsular polysaccharides (CPSs) successfully protect from infection, but not all pneumococcal serotypes are covered with equal potency. Marketed glycoconjugate vaccines induce low levels of functional antibodies against the highly invasive serotype 1 (ST1), presumably due to the obscuring of protective epitopes during chemical activation and conjugation to carrier proteins. Synthetic oligosaccharide antigens can be designed to carry linkers for site-selective protein conjugation while keeping protective epitopes intact. Here, we developed an efficacious semisynthetic ST1 glycoconjugate vaccine candidate. A panel of synthetic oligosaccharides served to reveal a critical role of the rare aminosugar, 2-acetamido-4-amino-2,4,6-trideoxy-d-galactose (d-AAT), for ST1 immune recognition. A monovalent ST1 trisaccharide carrying d-AAT at the nonreducing end induced a strong antibacterial immune response in rabbits and outperformed the ST1 component of the multivalent blockbuster vaccine Prevenar 13, paving the way for a more efficacious vaccine

Development of an Efficacious, Semisynthetic Glycoconjugate Vaccine Candidate against <i>Streptococcus pneumoniae</i> Serotype 1

Infections with <i>Streptococcus pneumoniae</i> are a major health burden. Glycoconjugate vaccines based on capsular polysaccharides (CPSs) successfully protect from infection, but not all pneumococcal serotypes are covered with equal potency. Marketed glycoconjugate vaccines induce low levels of functional antibodies against the highly invasive serotype 1 (ST1), presumably due to the obscuring of protective epitopes during chemical activation and conjugation to carrier proteins. Synthetic oligosaccharide antigens can be designed to carry linkers for site-selective protein conjugation while keeping protective epitopes intact. Here, we developed an efficacious semisynthetic ST1 glycoconjugate vaccine candidate. A panel of synthetic oligosaccharides served to reveal a critical role of the rare aminosugar, 2-acetamido-4-amino-2,4,6-trideoxy-d-galactose (d-AAT), for ST1 immune recognition. A monovalent ST1 trisaccharide carrying d-AAT at the nonreducing end induced a strong antibacterial immune response in rabbits and outperformed the ST1 component of the multivalent blockbuster vaccine Prevenar 13, paving the way for a more efficacious vaccine

The Kinetics of SARS-CoV-2 Antibody Development Is Associated with Clearance of RNAemia

We showed that persistent SARS-CoV-2 RNAemia is an independent predictor of severe COVID-19. We observed that SARS-CoV-2-targeted antibody maturation, specifically Fc-effector functions rather than neutralization, was strongly linked with the ability to rapidly clear viremia.</jats:p