New vaccination approach using formalin-killed Streptococcus pyogenes vaccine on the liver of Oreochromis niloticus fingerlings.

Newly synthesized vaccines prepared from formalin-killed bacteria Streptococcus pyogenes were investigated in the current study to evaluate the effectiveness of the newly synthesized vaccine as well as their safety by injected intraperitoneal. The study involved several steps 1st step is the preparation of the vaccine followed by the 2nd step: Evaluate the effectiveness and vaccine safety against pathogenic S. pyogenes through 4 different groups including control (Group I). Group II (Bacterial, infected group), Group III (Vaccine), and the Last group was the challenged group after the vaccination (Vacc + Bac). Different Immunological and biochemical parameters were measured in addition to hematological and histopathological examinations. For example, oxidative/antioxidants, inflammatory biomarkers, fragmentation and cell damage, and finally the histopathological study. The current study showed an increase in all oxidative, inflammatory, and cell damage (DNA fragmentation assays), additionally markedly elevation in histopathological cell damage in the infected group (Group II) compared with the control group. The vaccine and challenged after vaccination group (vaccine + Bacteria), showed great improvement in oxidative biomarkers (LPO) and an increase in antioxidants biomarkers (GSH, SOD, GST, DPPH, ABTS, GR and GPx), Also the inflammation and histopathological examination. The newly synthesized vaccine improved the resistance of Oreochromis niloticus and can be used as a preventive therapy agent for pathogenic bacteria S. pyogenes.

Immunogenicity of a 30-valent M protein mRNA group A Streptococcus vaccine.

BACKGROUND: Group A Streptococcus (Strep A) causes both uncomplicated and severe invasive infections, as well as the post-infection complications acute rheumatic fever and rheumatic heart disease. Despite the high global burden of disease resulting from Strep A infections, there is not a licensed vaccine. A 30-valent M protein-based vaccine has previously been shown to be immunogenic in animal models and in a Phase I clinical trial (NCT02564237). Here, we assessed the immunogenicity of a 30-valent messenger (m)RNA vaccine designed to express the same M peptide targets as the 30-valent protein vaccine and compared it with the protein vaccine. METHODS: Female New Zealand white rabbits were immunized with one of four vaccine formulations (3 doses of each formulation at days 1, 28, and 56): soluble mRNA (100 µg/animal), C-terminal transmembrane mRNA (100 µg/animal), protein vaccine (400 µg/animal), or a non-translatable RNA control (100 µg/animal). Serum was collected one day prior to the first dose and on days 42 and 70. Rabbit serum samples were assayed for antibody levels against synthetic M peptides by ELISA. HL-60 opsonophagocytic killing (OPK) assays were performed to assess functional antibody levels. RESULTS: Serum IgG levels were similar for the mRNA and protein vaccines. The CtTM version of the mRNA vaccine elicited slightly higher antibody levels than the mRNA designed to express soluble proteins. OPK activity was similar for the mRNA and protein vaccines, regardless of M type. CONCLUSIONS: The total antibody responses and functional antibody levels elicited by the 30-valent mRNA Strep A vaccines were similar to those observed following immunization with the analogous protein vaccine. The mRNA vaccine platform provides potential advantages to protein-based vaccines including inherent adjuvant activity, increased production efficiency, lower cost, and the potential to rapidly change epitopes/peptides, all of which are important considerations related to multivalent Strep A vaccine development.

Increase in the incidence of invasive bacterial infections following the COVID-19 pandemic: potential links with decreased herd trained immunity - a novel concept in medicine.

A global increase in the incidence of various infectious diseases has been observed since the end of the COVID­19 pandemic. This may be due to 2 independent phenomena. One of them is impaired immunity of long­COVID patients. The second (major) one is associated with long­term isolation of many people during the global pandemic­related lockdown, resulting in an extreme reduction of exposure to natural environmental human microbiota. This, in turn, led to a silencing state of the body's defense systems, including a decline of the prepandemic trained immunity (innate memory), which only persists for weeks to months after exposure to a pathogen. This decrease in the performance of trained immunity may be especially important for morbidity of infectious diseases without currently available vaccines, such as invasive group A Streptococcus pyogenes (GAS) infections, primarily streptococcal toxic shock syndrome. This review discusses data that support an important role of trained macrophages in host defense, and demonstrates the potential clinical implications of ß­glucan, the major inducer of trained macrophages, for prophylactic and therapeutic use in individuals with impaired personal innate immunity. Altogether, it might be speculated that trained innate immunity within an entire population can lead to the development of herd trained immunity (HTI), a newly­coined medical term. HTI can supplement classic, antigen­specific herd immunity (memory B and T cells), and it plays a key role in preventing the spread of various infectious diseases, including invasive GAS infections. Unfortunately, the global HTI has been overthrown during the COVID­19 pandemic; however, it should be restored shortly.

Cyclic Peptide Conjugate Vaccines and Physically Mixed Cyclic Peptide Vaccines for Subcutaneous Immunization.

Immune stimulants (adjuvants) enhance immune system recognition to provide an effective and individualized immune response when delivered with an antigen. Synthetic cyclic deca-peptides, co-administered with a toll-like receptor targeting lipopeptide, have shown self-adjuvant properties, dramatically boosting the immune response in a murine model as a subunit peptide-based vaccine containing group A Streptococcus peptide antigens.Here, we designed a novel peptide and lipid adjuvant system for the delivery of group A Streptococcus peptide antigen and a T helper peptide epitope. Following linear peptide synthesis on 2-chlorotrityl chloride resin, the linear peptide was cleaved and head-to-tail cyclized in solution. The selective arrangement of amino acids in the deca-peptide allowed for selective conjugation of lipids and/or peptide antigens following cyclisation. Using both solution-phase peptide chemistry and copper-catalyzed azide-alkyne cycloaddition reaction were covalently (and selectively) ligated lipid and/or peptide antigens onto the cyclic deca-peptide core. Subcutaneous administration of the vaccine design to mice resulted in the generation of a large number of serum immunoglobulin (Ig) G antibodies.

Self-assembled monovalent lipidated mannose ligand as a standalone nanoadjuvant.

Subunit vaccines require an immunostimulant (adjuvant) and/or delivery system to induce immunity. However, currently, available adjuvants are either too dangerous in terms of side effects for human use (experimental adjuvants) or have limited efficacy and applicability. In this study, we examined the capacity of mannose-lipopeptide ligands to enhance the immunogenicity of a vaccine consisting of polyleucine(L15)-antigen conjugates anchored to liposomes. The clinically tested Group A Streptococcus (GAS) B-cell epitope, J8, combined with universal T helper PADRE (P) was used as the antigen. Six distinct mannose ligands were incorporated into neutral liposomes carrying L15PJ8. While induced antibody titers were relatively low, the ligand carrying mannose, glycine/lysine spacer, and two palmitic acids as liposomal membrane anchoring moieties (ligand 3), induced significantly higher IgG titers than non-mannosylated liposomes. The IgG titers were significantly enhanced when positively charged liposomes were employed. Importantly, the produced antibodies were able to kill GAS bacteria. Unexpectedly, the physical mixture of only ligand 3 and PJ8 produced self-assembled nanorods that induced antibody titers as high as those elicited by the lead liposomal formulation and antigen adjuvanted with the potent, but toxic, complete Freund's adjuvant (CFA). Antibodies produced upon immunization with PJ8 + 3 were even more opsonic than those induced by CFA + PJ8. Importantly, in contrast to CFA, ligand 3 did not induce observable adverse reactions or excessive inflammatory responses. Thus, we demonstrated that a mannose ligand, alone, can serve as an effective vaccine nanoadjuvant.

Manganese uptake by MtsABC contributes to the pathogenesis of human pathogen group A streptococcus by resisting host nutritional immune defenses.

The interplay between host nutritional immune mechanisms and bacterial nutrient uptake systems has a major impact on the disease outcome. The host immune factor calprotectin (CP) limits the availability of essential transition metals, such as manganese (Mn) and zinc (Zn), to control the growth of invading pathogens. We previously demonstrated that the competition between CP and the human pathogen group A streptococcus (GAS) for Zn impacts GAS pathogenesis. However, the contribution of Mn sequestration by CP in GAS infection control and the role of GAS Mn acquisition systems in overcoming host-imposed Mn limitation remain unknown. Using a combination of in vitro and in vivo studies, we show that GAS-encoded mtsABC is a Mn uptake system that aids bacterial evasion of CP-imposed Mn scarcity and promotes GAS virulence. Mn deficiency caused by either the inactivation of mtsC or CP also impaired the protective function of GAS-encoded Mn-dependent superoxide dismutase. Our ex vivo studies using human saliva show that saliva is a Mn-scant body fluid, and Mn acquisition by MtsABC is critical for GAS survival in human saliva. Finally, animal infection studies using wild-type (WT) and CP-/- mice showed that MtsABC is critical for GAS virulence in WT mice but dispensable in mice lacking CP, indicating the direct interplay between MtsABC and CP in vivo. Together, our studies elucidate the role of the Mn import system in GAS evasion of host-imposed metal sequestration and underscore the translational potential of MtsABC as a therapeutic or prophylactic target.

Emergent emm4 group A Streptococcus evidences a survival strategy during interaction with immune effector cells.

The major gram-positive pathogen group A Streptococcus (GAS) is a model organism for studying microbial epidemics as it causes waves of infections. Since 1980, several GAS epidemics have been ascribed to the emergence of clones producing increased amounts of key virulence factors such as streptolysin O (SLO). Herein, we sought to identify mechanisms underlying our recently identified temporal clonal emergence among emm4 GAS, given that emergent strains did not produce augmented levels of virulence factors relative to historic isolates. By creating and analyzing isoallelic strains, we determined that a conserved mutation in a previously undescribed gene encoding a putative carbonic anhydrase was responsible for the defective in vitro growth observed in the emergent strains. We also identified that the emergent strains survived better inside macrophages and killed macrophages at lower rates than the historic strains. Via the creation of isogenic mutant strains, we linked the emergent strain "survival" phenotype to the downregulation of the SLO encoding gene and upregulation of the msrAB operon which encodes proteins involved in defense against extracellular oxidative stress. Our findings are in accord with recent surveillance studies which found a high ratio of mucosal (i.e., pharyngeal) relative to invasive infections among emm4 GAS. Since ever-increasing virulence is unlikely to be evolutionarily advantageous for a microbial pathogen, our data further understanding of the well-described oscillating patterns of virulent GAS infections by demonstrating mechanisms by which emergent strains adapt a "survival" strategy to outcompete previously circulating isolates.

Group A Streptococcus induces lysosomal dysfunction in THP-1 macrophages.

The human-specific bacterial pathogen group A Streptococcus (GAS) is a significant cause of morbidity and mortality. Macrophages are important to control GAS infection, but previous data indicate that GAS can persist in macrophages. In this study, we detail the molecular mechanisms by which GAS survives in THP-1 macrophages. Our fluorescence microscopy studies demonstrate that GAS is readily phagocytosed by macrophages, but persists within phagolysosomes. These phagolysosomes are not acidified, which is in agreement with our findings that GAS cannot survive in low pH environments. We find that the secreted pore-forming toxin Streptolysin O (SLO) perforates the phagolysosomal membrane, allowing leakage of not only protons but also large proteins including the lysosomal protease cathepsin B. Additionally, GAS recruits CD63/LAMP-3, which may contribute to lysosomal permeabilization, especially in the absence of SLO. Thus, although GAS does not inhibit fusion of the lysosome with the phagosome, it has multiple mechanisms to prevent proper phagolysosome function, allowing for persistence of the bacteria within the macrophage. This has important implications for not only the initial response but also the overall functionality of the macrophages, which may lead to the resulting pathologies in GAS infection. Our data suggest that therapies aimed at improving macrophage function may positively impact patient outcomes in GAS infection.

Streptococcal pyrogenic exotoxin B is a superantigen that induces murine splenocyte proliferation and secretion of IL-2 and IFN-γ ex vivo.

Streptococcus pyogenes is a significant human pathogen, producing a range of virulence factors, including streptococcal pyrogenic exotoxin B (SpeB) that is associated with foodborne outbreaks. It was only known that this cysteine protease mediates cleavage of transmembrane proteins to permit bacterial penetration and is found in 25% of clinical isolates from streptococcal toxic shock syndrome patients with extreme inflammation. Its interaction with host and streptococcal proteins has been well characterized, but doubt remains about whether it constitutes a superantigen. In this study, for the first time it is shown that SpeB acts as a superantigen, similarly to other known superantigens such as staphylococcal enterotoxin A or streptococcal pyrogenic exotoxin type C, by inducing proliferation of murine splenocytes and cytokine secretion, primarily of interleukin-2 (IL-2), as shown by cytometric bead array analysis. IL-2 secretion was confirmed by enzyme-linked immunosorbent assay (ELISA) as well as secretion of interferon-γ. ELISA showed a dose-dependent relationship between SpeB concentration in splenocyte cells and IL-2 secretion levels, and it was shown that SpeB retains activity in milk pasteurized for 30 min at 63°C.

Multimodal Mass Spectrometry Identifies a Conserved Protective Epitope in S. pyogenes Streptolysin O.

An important element of antibody-guided vaccine design is the use of neutralizing or opsonic monoclonal antibodies to define protective epitopes in their native three-dimensional conformation. Here, we demonstrate a multimodal mass spectrometry-based strategy for in-depth characterization of antigen-antibody complexes to enable the identification of protective epitopes using the cytolytic exotoxin Streptolysin O (SLO) from Streptococcus pyogenes as a showcase. We first discovered a monoclonal antibody with an undisclosed sequence capable of neutralizing SLO-mediated cytolysis. The amino acid sequence of both the antibody light and the heavy chain was determined using mass-spectrometry-based de novo sequencing, followed by chemical cross-linking mass spectrometry to generate distance constraints between the antibody fragment antigen-binding region and SLO. Subsequent integrative computational modeling revealed a discontinuous epitope located in domain 3 of SLO that was experimentally validated by hydrogen-deuterium exchange mass spectrometry and reverse engineering of the targeted epitope. The results show that the antibody inhibits SLO-mediated cytolysis by binding to a discontinuous epitope in domain 3, likely preventing oligomerization and subsequent secondary structure transitions critical for pore-formation. The epitope is highly conserved across >98% of the characterized S. pyogenes isolates, making it an attractive target for antibody-based therapy and vaccine design against severe streptococcal infections.

Glycan-Reactive Innate-like B Cells and Developmental Checkpoints.

Using an Ig H chain conferring specificity for N-acetyl-d-glucosamine (GlcNAc), we developed transgenic (VHHGAC39 TG) mice to study the role of self-antigens in GlcNAc-reactive B-1 B cell development. In VHHGAC39 TG mice, GlcNAc-reactive B-1 B cell development during ontogeny and in adult bone marrow was normal. However, adult TG mice exhibited a block at transitional-2 immature B cell stages, resulting in impaired allelic exclusion and accumulation of a B cell subset coexpressing endogenous Ig gene rearrangements. Similarly, VHHGAC39 B cell fitness was impeded compared with non-self-reactive VHJ558 B TG cells in competitive mixed bone marrow chimeras. Nonetheless, adult VHHGAC39 mice immunized with Streptococcus pyogenes produce anti-GlcNAc Abs. Peritoneal cavity B cells transferred from VHHGAC39 TG mice into RAG-/- mice also exhibited robust expansion and anti-GlcNAc Ab production. However, chronic treatment of young VHHGAC39 mice with GlcNAc-specific mAbs leads to lower GlcNAc-binding B cell frequencies while increasing the proportion of GlcNAc-binding B1-a cells, suggesting that Ag masking or clearance of GlcNAc Ags impedes maturation of newly formed GlcNAc-reactive B cells. Finally, BCR H chain editing promotes expression of endogenous nontransgenic BCR alleles, allowing potentially self-reactive TG B cells to escape anergy or deletion at the transitional stage of precursor B cell development. Collectively, these observations indicate that GlcNAc-reactive B cell development is sensitive to the access of autologous Ags.

Pro-inflammatory interactions of streptolysin O toxin with human neutrophils in vitro.

The recent global resurgence of severe infections caused by the Group A streptococcus (GAS) pathogen, Streptococcus pyogenes, has focused attention on this microbial pathogen, which produces an array of virulence factors, such as the pore-forming toxin, streptolysin O (SOT). Importantly, the interactions of SOT with human neutrophils (PMN), are not well understood. The current study was designed to investigate the effects of pretreatment of isolated human PMN with purified SOT on several pro-inflammatory activities, including generation of reactive oxygen species (ROS), degranulation (elastase release), influx of extracellular calcium (Ca2+) and release of extracellular DNA (NETosis), using chemiluminescence, spectrophotometric and fluorimetric procedures, respectively. Exposure of PMN to SOT alone caused modest production of ROS and elastase release, while pretreatment with the toxin caused significant augmentation of chemoattractant (fMLP)-activated ROS generation and release of elastase by activated PMN. These effects of treatment of PMN with SOT were associated with both a marked and sustained elevation of cytosolic Ca2+concentrations and significant increases in the concentrations of extracellular DNA, indicative of NETosis. The current study has identified a potential role for SOT in augmenting the Ca2+-dependent pro-inflammatory interactions of PMN, which, if operative in a clinical setting, may contribute to hyper-activation of PMN and GAS-mediated tissue injury.

The hinge-engineered IgG1-IgG3 hybrid subclass IgGh47 potently enhances Fc-mediated function of anti-streptococcal and SARS-CoV-2 antibodies.

Streptococcus pyogenes can cause invasive disease with high mortality despite adequate antibiotic treatments. To address this unmet need, we have previously generated an opsonic IgG1 monoclonal antibody, Ab25, targeting the bacterial M protein. Here, we engineer the IgG2-4 subclasses of Ab25. Despite having reduced binding, the IgG3 version promotes stronger phagocytosis of bacteria. Using atomic simulations, we show that IgG3's Fc tail has extensive movement in 3D space due to its extended hinge region, possibly facilitating interactions with immune cells. We replaced the hinge of IgG1 with four different IgG3-hinge segment subclasses, IgGhxx. Hinge-engineering does not diminish binding as with IgG3 but enhances opsonic function, where a 47 amino acid hinge is comparable to IgG3 in function. IgGh47 shows improved protection against S. pyogenes in a systemic infection mouse model, suggesting that IgGh47 has promise as a preclinical therapeutic candidate. Importantly, the enhanced opsonic function of IgGh47 is generalizable to diverse S. pyogenes strains from clinical isolates. We generated IgGh47 versions of anti-SARS-CoV-2 mAbs to broaden the biological applicability, and these also exhibit strongly enhanced opsonic function compared to the IgG1 subclass. The improved function of the IgGh47 subclass in two distant biological systems provides new insights into antibody function.

Quantification of Adaptive Immune Responses Against Protein-Binding Interfaces in the Streptococcal M1 Protein.

Bacterial or viral antigens can contain subdominant protein regions that elicit weak antibody responses upon vaccination or infection although there is accumulating evidence that antibody responses against subdominant regions can enhance the protective immune response. One proposed mechanism for subdominant protein regions is the binding of host proteins that prevent antibody production against epitopes hidden within the protein binding interfaces. Here, we used affinity purification combined with quantitative mass spectrometry (AP-MS) to examine the level of competition between antigen-specific antibodies and host-pathogen protein interaction networks using the M1 protein from Streptococcus pyogenes as a model system. As most humans have circulating antibodies against the M1 protein, we first used AP-MS to show that the M1 protein interspecies protein network formed with human plasma proteins is largely conserved in naïve mice. Immunizing mice with the M1 protein generated a time-dependent increase of anti-M1 antibodies. AP-MS analysis comparing the composition of the M1-plasma protein network from naïve and immunized mice showed significant enrichment of 292 IgG peptides associated with 56 IgG chains in the immune mice. Despite the significant increase of bound IgGs, the levels of interacting plasma proteins were not significantly reduced in the immune mice. The results indicate that the antigen-specific polyclonal IgG against the M1 protein primarily targets epitopes outside the other plasma protein binding interfaces. In conclusion, this study demonstrates that AP-MS is a promising strategy to determine the relationship between antigen-specific antibodies and host-pathogen interaction networks that could be used to define subdominant protein regions of relevance for vaccine development.

Application of Transthoracic Echocardiography for Cardiac Safety Evaluation in the Clinical Development Process of Vaccines Against Streptococcus pyogenes.

Superficial infections with Streptococcus pyogenes (Strep A), pharyngitis and impetigo can induce acute rheumatic fever, an autoimmune sequela manifesting mostly with arthritis and rheumatic carditis. Valvular heart damage can persist or advance following repeated episodes of acute rheumatic fever, causing rheumatic heart disease. Acute rheumatic fever and rheumatic heart disease disproportionately affect children and young adults in developing countries and disadvantaged communities in developed countries. People living with rheumatic heart disease are at risk of experiencing potentially fatal complications such as heart failure, bacterial endocarditis or stroke. Transthoracic echocardiography plays a central role in diagnosing both rheumatic carditis and rheumatic heart disease. Despite the obvious medical need, no licensed Strep A vaccines are currently available, as their clinical development process faces several challenges, including concerns for cardiac safety. However, the development of Strep A vaccines has been recently relaunched by many vaccine developers. In this context, a reliable and consistent safety evaluation of Strep A vaccine candidates, including the use of transthoracic echocardiography for detecting cardiac adverse events, could greatly contribute to developing a safe and efficacious product in the near future. Here, we propose a framework for the consistent use of transthoracic echocardiography to proactively detect cardiac safety events in clinical trials of Strep A vaccine candidates.

Throat and skin infections caused by certain types of bacteria, named Streptococcus pyogenes, are frequent worldwide; however, in many children from less developed countries and disadvantaged communities, infections with S. pyogenes lead to a condition called acute rheumatic fever, which usually affects the joints and the heart. Damage to the heart valves may evolve to rheumatic heart disease, a permanent condition with often life-threatening complications. Rheumatic heart disease is an important health problem in places and communities where S. pyogenes infections occur frequently. A vaccine against these bacteria would help lower the number of people with valvular heart disease; however, no such vaccine exists yet. Research on vaccines against S. pyogenes was on hold for almost 30 years because of initial concerns that vaccinated children might develop acute rheumatic fever more frequently. Recently, researchers started working again on vaccines against S. pyogenes, but concerns about the safety of such vaccines persist. Doctors can reliably use echocardiography to diagnose cases of rheumatic carditis (as a sign of acute rheumatic fever) and rheumatic heart disease. Here, we propose a simple approach for the consistent use of echocardiography in clinical research of vaccines against S. pyogenes that will allow the detection of any potential heart-related side effects of the vaccine.

Angiotensin II and post-streptococcal glomerulonephritis.

BACKGROUND: Post-streptococcal glomerulonephritis (PSGN) is a consequence of the infection by group A beta-hemolytic streptococcus. During this infection, various immunological processes generated by streptococcal antigens are triggered, such as the induction of antibodies and immune complexes. This activation of the immune system involves both innate and acquired immunity. The immunological events that occur at the renal level lead to kidney damage with chronic renal failure as well as resolution of the pathological process (in most cases). Angiotensin II (Ang II) is a molecule with vasopressor and pro-inflammatory capacities, being an important factor in various inflammatory processes. During PSGN some events are defined that make Ang II conceivable as a molecule involved in the inflammatory processes during the disease. CONCLUSION: This review is focused on defining which reported events would be related to the presence of this hormone in PSGN.

A conserved 3D pattern in a Streptococcus pyogenes M protein immunogen elicits M-type crossreactivity.

Coiled coil-forming M proteins of the widespread and potentially deadly bacterial pathogen Streptococcus pyogenes (strep A) are immunodominant targets of opsonizing antibodies. However, antigenic sequence variability of M proteins into >220 M types, as defined by their hypervariable regions (HVRs), is considered to limit M proteins as vaccine immunogens because of type specificity in the antibody response. Surprisingly, a multi-HVR immunogen in clinical vaccine trials was shown to elicit M-type crossreactivity. The basis for this crossreactivity is unknown but may be due in part to antibody recognition of a 3D pattern conserved in many M protein HVRs that confers binding to human complement C4b-binding protein (C4BP). To test this hypothesis, we investigated whether a single M protein immunogen carrying the 3D pattern would elicit crossreactivity against other M types carrying the 3D pattern. We found that a 34-amino acid sequence of S. pyogenes M2 protein bearing the 3D pattern retained full C4BP-binding capacity when fused to a coiled coil-stabilizing sequence from the protein GCN4. We show that this immunogen, called M2G, elicited cross-reactive antibodies against a number of M types that carry the 3D pattern but not against those that lack the 3D pattern. We further show that the M2G antiserum-recognized M proteins displayed natively on the strep A surface and promoted the opsonophagocytic killing of strep A strains expressing these M proteins. As C4BP binding is a conserved virulence trait of strep A, we propose that targeting the 3D pattern may prove advantageous in vaccine design.

Immune signature of acute pharyngitis in a Streptococcus pyogenes human challenge trial.

Streptococcus pyogenes causes at least 750 million infections and more than 500,000 deaths each year. No vaccine is currently available for S. pyogenes and the use of human challenge models offer unique and exciting opportunities to interrogate the immune response to infectious diseases. Here, we use high-dimensional flow cytometric analysis and multiplex cytokine and chemokine assays to study serial blood and saliva samples collected during the early immune response in human participants following challenge with S. pyogenes. We find an immune signature of experimental human pharyngitis characterised by: 1) elevation of serum IL-1Ra, IL-6, IFN-γ, IP-10 and IL-18; 2) increases in peripheral blood innate dendritic cell and monocyte populations; 3) reduced circulation of B cells and CD4+ T cell subsets (Th1, Th17, Treg, TFH) during the acute phase; and 4) activation of unconventional T cell subsets, γδTCR + Vδ2+ T cells and MAIT cells. These findings demonstrate that S. pyogenes infection generates a robust early immune response, which may be important for host protection. Together, these data will help advance research to establish correlates of immune protection and focus the evaluation of vaccines.

Developing an Effective Glycan-Based Vaccine for Streptococcus Pyogenes.

Streptococcus pyogenes is a primary infective agent that causes approximately 700 million human infections each year, resulting in more than 500 000 deaths. Carbohydrate-based vaccines are proven to be one of the most promising subunit vaccine candidates, as the bacterial glycan pattern(s) are different from mammalian cells and show increased pathogen serotype conservancy than the protein components. In this Review we highlight reverse vaccinology for use in the development of subunit vaccines against S. pyogenes, and report reproducible methods of carbohydrate antigen production, in addition to the structure-immunogenicity correlation between group A carbohydrate epitopes and alternative vaccine antigen carrier systems. We also report recent advances used to overcome hurdles in carbohydrate-based vaccine development.