Immunogenicity of a 26-valent group A streptococcal vaccine

Disease manifestations and pathogenic mechanisms of Group A Streptococcus

Streptococcus pyogenes, also known as group A Streptococcus (GAS), causes mild human infections such as pharyngitis and impetigo and serious infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. Furthermore, repeated GAS infections may trigger autoimmune diseases, including acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease. Combined, these diseases account for over half a million deaths per year globally. Genomic and molecular analyses have now characterized a large number of GAS virulence determinants, many of which exhibit overlap and redundancy in the processes of adhesion and colonization, innate immune resistance, and the capacity to facilitate tissue barrier degradation and spread within the human host. This improved understanding of the contribution of individual virulence determinants to the disease process has led to the formulation of models of GAS disease progression, which may lead to better treatment and intervention strategies. While GAS remains sensitive to all penicillins and cephalosporins, rising resistance to other antibiotics used in disease treatment is an increasing worldwide concern. Several GAS vaccine formulations that elicit protective immunity in animal models have shown promise in nonhuman primate and early-stage human trials. The development of a safe and efficacious commercial human vaccine for the prophylaxis of GAS disease remains a high priority.

Beta-hemolytic streptococcal infections in trauma patients

PURPOSE

β-hemolytic streptococci (βHS) causes a diverse array of human infections. The molecular epidemiology of β-hemolytic streptococcal infections in trauma patients has not been studied. This study reports the molecular and clinical epidemiology of β-hemolytic streptococcal infections at a level 1 trauma centre of India.

METHODS

A total of 117 isolates of βHS were recovered from clinical samples of trauma patients. The isolates were identified to species level and subjected to antimicrobial susceptibility testing. Polymerase chain reaction (PCR) assay was done to detect exotoxin virulence genes. The M protein gene (emm gene) types of GAS strains were ascertained by sequencing.

RESULTS

Group A Streptococcus (GAS) was the most common isolate (64 %), followed by group G Streptococcus (23 %). A large proportion of GAS produced speB (99 %), smeZ (91 %), speF (95 %) and speG (87 %). smeZ was produced by 22 % of GGS. A total of 25 different emm types/subtypes were seen in GAS, with emm 11 being the most common. Resistance to tetracycline (69 %) and erythromycin (33 %) was commonly seen in GAS.

CONCLUSIONS

β-hemolytic streptococcal infections in Indian trauma patients are caused by GAS and non-GAS strains alike. A high diversity of emm types was seen in GAS isolates, with high macrolide and tetracycline resistance. SpeA was less commonly seen in Indian GAS isolates. There was no association between disease severity and exotoxin gene production.

Disease manifestations and pathogenic mechanisms of Group A Streptococcus

Streptococcus pyogenes, also known as group A Streptococcus (GAS), causes mild human infections such as pharyngitis and impetigo and serious infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. Furthermore, repeated GAS infections may trigger autoimmune diseases, including acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease. Combined, these diseases account for over half a million deaths per year globally. Genomic and molecular analyses have now characterized a large number of GAS virulence determinants, many of which exhibit overlap and redundancy in the processes of adhesion and colonization, innate immune resistance, and the capacity to facilitate tissue barrier degradation and spread within the human host. This improved understanding of the contribution of individual virulence determinants to the disease process has led to the formulation of models of GAS disease progression, which may lead to better treatment and intervention strategies. While GAS remains sensitive to all penicillins and cephalosporins, rising resistance to other antibiotics used in disease treatment is an increasing worldwide concern. Several GAS vaccine formulations that elicit protective immunity in animal models have shown promise in nonhuman primate and early-stage human trials. The development of a safe and efficacious commercial human vaccine for the prophylaxis of GAS disease remains a high priority.

Evaluation of emm gene types, toxin gene profiles and clonal relatedness of group A streptococci

The aim of this study is to evaluate antibiotic susceptibilities, emm gene types, toxin gene profiles and clonal relatedness of group A streptococci (GAS) isolates obtained from patients and carriers. A total of 79 clinical isolates from patients and 60 isolates from carriers were included in the study. Emm typing, toxin gene detection for speA, speB, speC, speG and smeZ genes and pulsed-field gel electrophoresis (PFGE) was performed. Twenty-one distinct emm types were detected; the most common types were emm12, emm89, emm1, emm77, emm4 and emm3. The detection rates of both emm types and the toxin genes didn't differ significantly between patients and carriers. The presence of speA and smeZ was significantly higher in emm1 and speG was significantly lower in emm4 when compared to the other emm types. The rate of clustering obtained with PFGE wasn't significantly different in patients and carriers. As a result, twelve of the 21 emm types detected in this study were covered by the 26-valent vaccine, constituting 77.7% of the emm typeable isolates; however the emm4 type which is one of the most common types in the present study is not among this coverage.

Preventing rheumatic fever: M-protein based vaccine

Group A beta hemolytic streptococcus (GAS), the organism which initiates rheumatic fever (RF) continues to be sensitive to penicillin. However, penicillin cannot prevent RF if the preceding sore throat is asymptomatic in more than 70 percent children. Prevention of rheumatic fever (RF) may be possible only with the use of a vaccine. Efforts to design a vaccine based on emm gene identification of GAS, M-protein going on for more than 40 years, is unlikely to succeed. M-protein is strain specific. Infection with one strain does not provide immunity from infection with another strain. Based on the emm gene identification, of 250 or more identified strains of GAS, the distribution is heterogenous and keeps changing. The M-protein gene sequence of the organism tends to mutate. A vaccine prepared from available strains may not be effective against a strain following mutation.

Lethal toxic shock syndrome due to GAS infection has been described with organisms without identifiable or functional M-protein. M-protein has been excluded as the antigen responsible for acute glomerulonephritis (GN). Therefore M-protein plays no role in one suppurative (toxic shock syndrome) and one non-suppurative (acute GN) manifestation due to GAS infection. Lastly there is no direct evidence to indicate that M-protein is involved in inducing RF. The role of M-protein and the GAS component resulting in the suppurative manifestations of GAS infections like pyoderma, septic arthritis or necrotizing fasciitis etc is unknown. For a vaccine to be effective, an epitope of the streptococcus which is stable and uniformly present in all strains, needs to be identified and tested for its safety and efficacy. The vaccine if and when available is expected to prevent GAS infection. Preventing GAS infection will prevent all the suppurative as well as non-suppurative manifestations including RF.

Nationwide laboratory-based surveillance of invasive beta-haemolytic streptococci in Denmark from 2005 to 2011

The aim of this work was to describe national surveillance of invasive beta-haemolytic streptococci (BHS) in Denmark and to report overall trends and major findings by groups and types of BHS causing laboratory-confirmed disease from 2005 to 2011. A total of 3063 BHS isolates were received from 2872 patients. Based on confirmed cases the overall annual incidence increased from 6.2 to 8.9 per 100 000 persons between 2005 and 2011. In 2011 the incidences of group A, B, C and G streptococci were 3.1, 2.3, 0.9 and 2.6 per 100 000 persons, respectively. An increase was observed for all groups of BHS, but in particular for group G in men above 65 years of age. Among group A streptococci (GAS), five T-types (1, 28,12, 3,13,B3264 and B3264) represented 71% and five emm-types (1, 28, 3, 89 and 12) 76% of all isolates. Among group B streptococci (GBS) four types (III, Ia, V, Ib) represented 79% of the isolates. Potential coverage for future vaccines against GAS and GBS disease was 76% compared with the 26-valent GAS vaccine and 89% based on GBS serotypes Ia, Ib, II, III and V. The number of reported cases of invasive BHS disease increased in Denmark from 2005 to 2011. Nationwide laboratory-based surveillance of BHS is required to monitor epidemiological changes, explore potential outbreaks and determine potential vaccine coverage.

Seven-year surveillance of emm types of pediatric Group A streptococcal pharyngitis isolates in Western Greece

Background

An experimental 26-valent M protein Group A streptococcal (GAS) vaccine has entered clinical studies. Pharyngeal GAS emm type surveillances in different areas and time-periods enhance the understanding of the epidemiology of GAS pharyngitis. Moreover, these surveillances, combined with the data on GAS invasive disease, can play a significant role in the formulation of multivalent type-specific vaccines.

Methods

During a 7-year period (1999–2005), 2408 GAS isolates were recovered from consecutive children with pharyngitis in Western Greece. The overall macrolide resistance rate was 22.8%. Along the study period we noted a tendency towards significantly decreased rates of resistance, with the lowest rates occurring in 2002 (15.3%), 2003 (15%) and 2004 (16.7%). A random sample of isolates from each year, 338 (61.7%) of the 548 macrolide-resistant and 205 (11%) of the macrolide-susceptible, underwent molecular analysis, including emm typing.

Results

The 543 typed isolates had 28 different emm types. A statistically significant association was found between macrolide resistance and emm4, emm22 and emm77, whereas emm1, emm3, emm6, emm12, emm87 and emm89 were associated with macrolide susceptibility. A significant yearly fluctuation was observed in emm4, emm28 and emm77. The most common macrolide-resistant GAS were emm77 isolates harboring erm(A), either alone or in combination with mef(A), emm4 carrying mef(A), emm28 possessing erm(B), emm75 carrying mef(A), emm12 harboring mef(A) and emm22 carrying erm(A). We estimated that 82.8% of the isolates belonged to emm types included in the novel 26-valent M protein vaccine. The vaccine coverage rate was determined mainly by the increased frequency of nonvaccine emm4 isolates.

Conclusions

A limited number of emm types dominated among macrolide-susceptible and macrolide-resistant GAS isolates. We observed seasonal fluctuations, which were significant for emm4, emm28 and emm77. This type of data can serve as baseline information if the novel 26-valent M protein GAS vaccine is introduced into practice.

Potential coverage of a multivalent M protein-based group A streptococcal vaccine

BACKGROUND

The greatest burden of group A streptococcal (GAS) disease worldwide is due to acute rheumatic fever (ARF) and rheumatic heart disease (RHD). Safe, effective and affordable vaccines designed to prevent GAS infections that trigger ARF could reduce the overall global morbidity and mortality from RHD. The current study evaluated the potential coverage of a new 30-valent M protein-based vaccine using GAS isolates from school children in Bamako, Mali, a population at high risk for the development of RHD.

METHODS

The bactericidal activity of rabbit antisera against the 30-valent vaccine was assessed using a collection of GAS isolates recovered during a study of the epidemiology of pharyngitis in Bamako.

RESULTS

Single isolates representing 42 of 67 emm-types, accounting for 85% of the GAS infections during the study, were evaluated. All (14/14) of the vaccine emm-types in the collection were opsonized (bactericidal killing >50%) and 26/28 non-vaccine types were opsonized. Bactericidal activity was observed against 60% of the total emm-types recovered in Bamako, which accounted for 81% of all infections.

CONCLUSIONS

Multivalent vaccines comprised of N-terminal M peptides elicit bactericidal antibodies against a broad range of GAS serotypes, indicating that their efficacy may extend beyond the emm-types included in the vaccine.

Identification of potential universal vaccine candidates against group A Streptococcus by using high throughput in silico and proteomics approach

Streptococcus pyogenes or group A Streptococcus (GAS) causes ~700 million human infections each year, resulting in over 500,000 deaths. The development of a commercial GAS vaccine is hampered due to high strain and serotype diversity in different geographical regions, and the generation of cross-reactive antibodies that may induce autoimmune disease. There is an urgent need to search for alternative vaccine candidates. High throughput multigenome data mining coupled with proteomics seems to be a promising approach to identify the universal vaccine candidates. In the present study, in silico analysis led to prediction of 147 proteins as universal vaccine candidates. Distribution pattern of these predicted candidates was explored in nonsequenced Indian GAS strains (n = 20) by using DNA array hybridization validating in silico analysis. High throughput analyses of surface proteins using 1D-SDS-PAGE coupled with ESI-LC-MS/MS was applied on highly (M49) and less (M1) invasive GAS strains of Indian origin. Comparative proteomics analysis revealed that highly invasive GAS M49 had metabolically more active membrane associated protein machinery than less invasive M1. Further, by overlapping proteomics data with in silico predicted vaccine candidate genes, 52 proteins were identified as probable universal vaccine candidates, which were expressed in these GAS serotypes. These proteins can further be investigated as universal vaccine candidates against GAS. Moreover, this robust approach may serve as a model that can be applied to identify the universal vaccine candidates in case of other pathogenic bacteria with high strain and genetic diversity.

Human pathogenic streptococcal proteomics and vaccine development

Gram-positive streptococci are non-motile, chain-forming bacteria commonly found in the normal oral and bowel flora of warm-blooded animals. Over the past decade, a proteomic approach combining 2-DE and MS has been used to systematically map the cellular, surface-associated and secreted proteins of human pathogenic streptococcal species. The public availability of complete streptococcal genomic sequences and the amalgamation of proteomic, genomic and bioinformatic technologies have recently facilitated the identification of novel streptococcal vaccine candidate antigens and therapeutic agents. The objective of this review is to examine the constituents of the streptococcal cell wall and secreted proteome, the mechanisms of transport of surface and secreted proteins, and describe the current methodologies employed for the identification of novel surface-displayed proteins and potential vaccine antigens.

Variability in the distribution of genes encoding virulence factors and putative extracellular proteins of Streptococcus pyogenes in India, a region with high streptococcal disease burden, and implication for development of a regional multisubunit vaccine

Streptococcus pyogenes causes a wide variety of human diseases and is a significant cause of morbidity and mortality. Attempts to develop a vaccine were hampered by the genetic diversity of S. pyogenes across different regions of the world. This study sought to identify streptococcal antigens suitable for a region-specific vaccine in India. We used a two-step approach, first performing epidemiological analysis to identify the conserved antigens among Indian isolates. The second step consisted of validating the identified antigens by serological analysis. The 201 streptococcal clinical isolates from India used in this study represented 69 different emm types, with emm12 being the most prevalent. Virulence profiling of the North and South Indian S. pyogenes isolates with a custom-designed streptococcal virulence microarray identified seven conserved putative vaccine candidates. Collagen-like surface protein (SCI), putative secreted 5'-nucleotidase (PSNT), and C5a peptidase were found in 100% of the isolates, while R28, a putative surface antigen (PSA), and a hypothetical protein (HYP) were found in 90% of the isolates. A fibronectin binding protein, SfbI, was present in only 78% of the isolates. In order to validate the identified potential vaccine candidates, 185 serum samples obtained from patients with different clinical manifestations were tested for antibodies. Irrespective of clinical manifestations, serum samples showed high antibody titers to all proteins except for SCI and R28. Thus, the data indicate that PSNT, C5a peptidase, PSA, HYP, and SfbI are promising candidates for a region-specific streptococcal vaccine for the different parts of India.

Immunogenicity of a divalent group A streptococcal vaccine

We designed and recombined the polypeptide based on the M protein of group A streptococci (GAS)--the causative pathogen of rheumatic fever and rheumatic heart disease, which would be a divalent vaccine to prevent and defend the diseases in relation to the different GAS strains. A divalent vaccine comprising three different peptide epitopes of the antiphagocytic M protein of GAS--an aminoterminal specific sequences, respectively, from the M1 and M12 proteins and J14 peptide (ASREAKKQVEKALE) within the highly conserved C-terminal repeat region of the M1 and M12 proteins--was subcutaneously delivered to mice with the adjuvant. Furthermore, the antisera titers of mice inoculated with the divalent vaccine were assayed by ELISA, and then opsonization and percentage killing against two different GAS serotypes were completed. Our data demonstrated that antisera raised against the divalent vaccine containing amino acids and M-protein-conserved C repeat region are able to kill several GAS strains isolated from the Guangzhou population. Therefore, the divalent vaccine can be used to prevent those diseases caused by GAS in an endemic area. We successfully construct the M-protein-based divalent vaccine that can bring out a high-level antisera titer of mice vaccinated with it. So, the vaccine has the potential to be used to prevent diseases caused by GAS in our country.

Group A Streptococcus emm gene types in pharyngeal isolates, Ontario, Canada, 2002-2010

Determination of emm variations may help improve vaccine design.

Group A Streptococcus (GAS) is a human-adapted pathogen that causes a variety of diseases, including pharyngitis and invasive infections. GAS strains are categorized by variation in the nucleotide sequence of the gene (emm) that encodes the M protein. To identify the emm types of GAS strains causing pharyngitis in Ontario, Canada, we sequenced the hypervariable region of the emm gene in 4,635 pharyngeal GAS isolates collected during 2002–2010. The most prevalent emm types varied little from year to year. In contrast, fine-scale geographic analysis identified inter-site variability in the most common emm types. Additionally, we observed fluctuations in yearly frequency of emm3 strains from pharyngitis patients that coincided with peaks of emm3 invasive infections. We also discovered a striking increase in frequency of emm89 strains among isolates from patients with pharyngitis and invasive disease. These findings about the epidemiology of GAS are potentially useful for vaccine research.

Immunological evaluation of lipopeptide group A streptococcus (GAS) vaccine: structure-activity relationship

Streptococcus pyogenes (group A streptococcus, GAS) is a Gram-positive bacterial pathogen responsible for a wide variety of diseases. To date, GAS vaccine development has focused primarily on the M-protein. The M-protein is highly variable at the amino (N)-terminus (determining serotype) but is conserved at the carboxyl (C)-terminus. Previously a 29 amino acid peptide (named J14) from the conserved region of the M-protein was identified as a potential vaccine candidate. J14 was capable of eliciting protective antibodies that recognized many GAS serotypes when co-administered with immuno-stimulants. This minimal epitope however showed no immunogenicity when administered alone. In an attempt overcome this immunological non-responsiveness, we developed a self-adjuvanting vaccine candidate composed of three components: the B-cell epitope (J14), a universal helper T-cell epitope (P25) and a lipid moiety consisting of lipoamino acids (Laas) which target Toll-like receptor 2 (TLR2). Immunological evaluation in B10.BR (H-2k) mice demonstrated that the epitope attachment to the point of lipid moiety, and the length of the Laa alkyl chain have a profound effect on vaccine immunogenicity after intranasal administration. It was demonstrated that a vaccine featuring C-terminal lipid moiety containing alkyl chains of 16 carbons, with P25 located at the N-terminus, and J14 attached to the side chain of a central lysine residue was capable of inducing optimal antibody response. These findings have considerable relevance to the development of a broad spectrum J14-based GAS vaccine and in particular provided a rational basis for peptide vaccine design based on this self-adjuvanting lipopeptide technology.

Group a streptococcal vaccine candidates: potential for the development of a human vaccine

Currently there is no commercial Group A Streptococcus (GAS; S. pyogenes) vaccine available. The development of safe GAS vaccines is challenging, researchers are confronted with obstacles such as the occurrence of many unique serotypes (there are greater than 150 M types), antigenic variation within the same serotype, large variations in the geographical distribution of serotypes, and the production of antibodies cross-reactive with human tissue which can lead to host auto-immune disease. Cell wall anchored, cell membrane associated, secreted and anchorless proteins have all been targeted as GAS vaccine candidates. As GAS is an exclusively human pathogen, the quest for an efficacious vaccine is further complicated by the lack of an animal model which mimics human disease and can be consistently and reproducibly colonized by multiple GAS strains.

Molecular analysis of Streptococcus pyogenes strains isolated from Chinese children with pharyngitis

Streptococcus pyogenes is an important gram-positive bacterial pathogen that causes various human diseases, of which streptococcal pharyngitis is the most common. In this work, a total of 185 S. pyogenes isolated from Chinese children with pharyngitis was analyzed by superantigen (SAg) genes, emm genotyping, and pulsed-field gel electrophoresis (PFGE). Fifty-eight (31.4%) isolates were also typed by multilocus sequence typing (MLST). The results indicate that most of the emm1 isolates possessed speA (88.5%) and speJ (83.6%), and few isolates possessed speI gene (13.1%). In contrast, none of the emm12-type isolates possessed speJ; few isolates possessed speA (5.2%); and most of the isolates possessed speI (91.7%). PFGE analysis revealed 25 different clusters, and MLST was performed for 2 predominant emm-type isolates; emm12 isolates belonged to ST36 while emm1 isolates belonged to ST28. As far as this collection is concerned, emm1 and emm12 are the prevalent genotypes among S. pyogenes strains associated with children's pharyngitis in China. Most of the pharyngitis strains can be covered by a 26-valent vaccine. A strong correspondence is found only in the direction of emm type for both SAg profiles and PFGE types but not in the reverse direction.

New 30-valent M protein-based vaccine evokes cross-opsonic antibodies against non-vaccine serotypes of group A streptococci

Our previous studies have shown that recombinant multivalent vaccines containing amino-terminal M protein fragments from as many as 26 different serotypes of group A streptococci (GAS) evoked opsonic antibodies in animals and humans. In the present study, we constructed a new 30-valent vaccine containing M protein peptides from GAS serotypes prevalent in North America and Europe. The vaccine was immunogenic in rabbits and evoked bactericidal antibodies against all 30 vaccine serotypes of GAS. In addition, the vaccine antisera also contained significant levels of bactericidal antibodies against 24 of 40 non-vaccine serotypes of GAS. These results indicate that the potential efficacy of the new multivalent vaccine may be greater than predicted based on the "type-specific" M peptides represented.

M-protein gene-type distribution and hyaluronic acid capsule in group AStreptococcusclinical isolates in Chile: association ofemmgene markers withcsrRalleles

Streptococcus pyogenescauses a variety of infections because of virulence factors such as capsular hyaluronic acid and M protein. The aim of this study was to determineemmtypes and capsule phenotype in 110 isolates ofS. pyogenesfrom patients with invasive (sterile sites) and non-invasive (mainly pharyngitis) infections in Chile, and the relationship between both virulence factors. The most abundant types found wereemm12,emm1,emm4andemm28and their distribution was similar to that seen in Latin America and developed countries, but very different from that in Asia and Pacific Island countries. Ten of 16emmtypes identified in pharyngeal isolates were found in sterile-site isolates, and three of nineemmtypes of sterile-site isolates occurred in pharyngeal isolates; threeemmsubtypes were novel. The amount of hyaluronic acid was significantly higher in sterile-site isolates but did not differ substantially amongemmtypes. Only three isolates were markedly capsulate and two of them had mutations in thecsrRgene that codes for a repressor of capsule synthesis genes. We found a non-random association betweenemmtypes andcsrRgene alleles suggesting that horizontal gene transfer is not freely occurring in the population.

HLA class II transgenic mice develop a safe and long lasting immune response against StreptInCor, an anti-group A streptococcus vaccine candidate

Streptococcus pyogenes infections remain a health problem in several countries because of post-streptococcal sequelae, such as rheumatic fever and rheumatic heart disease. We developed a vaccine epitope (StreptInCor) composed of 55 amino acid residues of the C-terminal portion of the M protein that encompasses both T and B cell protective epitopes. Recently, by using human blood samples, we showed that the StreptInCor epitope is able to bind to different HLA class II molecules and that it could be considered a universal vaccine epitope. In the present work, we evaluated the immune response of HLA class II transgenic mice against aluminum hydroxide-absorbed StreptInCor. After a period of one year, several organs were analyzed histologically to verify the safety of the candidate vaccine epitope. Our results showed that StreptInCor is able to induce robust and safe and long lasting immune response without deleterious reactions in several organs. In conclusion, the results presented here indicate that StreptInCor could be considered a safe vaccine against severe streptococcus-induced diseases.

Genes, autoimmunity and pathogenesis of rheumatic heart disease

Pathogenesis of rheumatic heart disease (RHD) remains incompletely understood. Several genes associated with RHD have been described; most of these are involved with immune responses. Single nucleotide polymorphisms in a number of genes affect patients with RHD compared to controls. Molecular mimicry between streptococcal antigens and human proteins, including cardiac myosin epitopes, vimentin and other intracellular proteins is central to the pathogenesis of RHD. Autoreactive T cells migrate from the peripheral blood to the heart and proliferate in the valves in response to stimulation with specific cytokines. The types of cells involved in the inflammation as well as different cytokine profiles in these patients are being investigated. High TNF alpha, interferon gamma, and low IL4 are found in the rheumatic valve suggesting an imbalance between Th1 and Th2 cytokines and probably contributing to the progressive and permanent valve damage. Animal model of ARF in the Lewis rat may further contribute towards understanding the ARF.

Inactivated and live, attenuated influenza vaccines protect mice against influenza: Streptococcus pyogenes super-infections

Mortality associated with influenza virus super-infections is frequently due to secondary bacterial complications. To date, super-infections with Streptococcus pyogenes have been studied less extensively than those associated with Streptococcus pneumoniae. This is significant because a vaccine for S. pyogenes is not clinically available, leaving vaccination against influenza virus as our only means for preventing these super-infections. In this study, we directly compared immunity induced by two types of influenza vaccine, either inactivated influenza virus (IIV) or live, attenuated influenza virus (LAIV), for the ability to prevent super-infections. Our data demonstrate that both IIV and LAIV vaccines induce similar levels of serum antibodies, and that LAIV alone induces IgA expression at mucosal surfaces. Upon super-infection, both vaccines have the ability to limit the induction of pro-inflammatory cytokines within the lung, including IFN-γ which has been shown to contribute to mortality in previous models of super-infection. Limiting expression of these pro-inflammatory cytokines within the lungs subsequently limits recruitment of macrophages and neutrophils to pulmonary surfaces, and ultimately protects both IIV- and LAIV-vaccinated mice from mortality. Despite their overall survival, both IIV- and LAIV-vaccinated mice demonstrated levels of bacteria within the lung tissue that are similar to those seen in unvaccinated mice. Thus, influenza virus:bacteria super-infections can be limited by vaccine-induced immunity against influenza virus, but the ability to prevent morbidity is not complete.

Anti-group A streptococcal vaccine epitope: structure, stability, and its ability to interact with HLA class II molecules

Streptococcus pyogenes infections remain a health problem in several countries due to poststreptococcal sequelae. We developed a vaccine epitope (StreptInCor) composed of 55 amino acids residues of the C-terminal portion of the M protein that encompasses both T and B cell protective epitopes. The nuclear magnetic resonance (NMR) structure of the StreptInCor peptide showed that the structure was composed of two microdomains linked by an 18-residue α-helix. A chemical stability study of the StreptInCor folding/unfolding process using far-UV circular dichroism showed that the structure was chemically stable with respect to pH and the concentration of urea. The T cell epitope is located in the first microdomain and encompasses 11 out of the 18 α-helix residues, whereas the B cell epitope is in the second microdomain and showed no α-helical structure. The prediction of StreptInCor epitope binding to different HLA class II molecules was evaluated based on an analysis of the 55 residues and the theoretical possibilities for the processed peptides to fit into the P1, P4, P6, and P9 pockets in the groove of several HLA class II molecules. We observed 7 potential sites along the amino acid sequence of StreptInCor that were capable of recognizing HLA class II molecules (DRB1*, DRB3*, DRB4*, and DRB5*). StreptInCor-overlapping peptides induced cellular and humoral immune responses of individuals bearing different HLA class II molecules and could be considered as a universal vaccine epitope.

The worldwide epidemiology of acute rheumatic fever and rheumatic heart disease

Acute rheumatic fever (ARF) and rheumatic heart disease (RHD) are significant public health concerns around the world. Despite decreasing incidence, there is still a significant disease burden, especially in developing nations. This review provides background on the history of ARF, its pathology and treatment, and the current reported worldwide incidence of ARF and prevalence of RHD.

Factors associated with Group A Streptococcus emm type diversification in a large urban setting in Brazil: a cross-sectional study

BACKGROUND

Group A Streptococcus (GAS) strain diversity varies across different regions of the world, according to low versus high-income countries. These differences may be related to geographic, environmental, socioeconomic, or host-related factors. However, local factors may also affect strain diversity. We compared the emm types of GAS isolates from children with and without sore throat in one large urban setting in Brazil.

METHODS

Children 3-15 years of age were consecutively recruited from slum and non-slum pediatric outpatient clinics between April-October, 2008. Throat cultures were performed and data intake forms were completed. GAS isolates were typed by emm sequencing.

RESULTS

From 2194 children, 254 (12%) GAS isolates were obtained. Of 238 GAS isolates that were emm-typed, 61 unique emm types were identified. Simpson's diversity index of the emm types was higher among isolates from slum children [97% (96%-98%)] than those of non-slum children [92% (89%-96%)]. Two emm types (66.0, 12.0) were more frequently isolated from children with sore throat (p < 0.05), and one emm type (27G.0) demonstrated a protective effect.

CONCLUSIONS

The emm type diversity from children attending slum clinics resembled the emm diversity of low income countries rather than that of children attending a non-slum clinic in the same city. Local factors, such as crowding, may enhance the frequency of GAS transmission and horizontal gene transfers that contribute to increased strain diversity in the slums. GAS vaccine coverage and control of GAS infections will need to take these local factors and strain differences into consideration.

Diversity of emm sequence types in group A beta-haemolytic streptococci in two remote Northern Territory Indigenous communities: implications for vaccine development

There is a high burden of disease due to group A streptococcus (GAS) in remote Northern Territory (NT) Indigenous communities. A proposed 26-valent GAS M-type vaccine covers 80-90% of pharyngeal and invasive isolates in the US. We examined the diversity and distribution of emm types in two remote Indigenous communities in the NT Top End over a 17-year period and compared them to the proposed vaccine types. Eighty emm types were identified between 1991 and 2007. Diversity in both communities was high (overall Simpson's index 0.976), but varied between communities. Prior to 2004, 71 emm types were identified and an additional 9 emm types were identified during a period of active surveillance in 2004-2005. The proposed 26-valent vaccine would be expected to cover only 20% of emm types recovered in this study. Of the 80 emm types, 16 (20%) were new sequence types identified since the last assignment of M types in 2002. The diversity of streptococcal isolates was higher than that reported from most industrialized countries, and similar to that described in several developing countries. A vaccine based on such a variable antigen is unlikely to provide effective protection in the highest risk populations.

Progress in the development of effective vaccines to prevent selected gram-positive bacterial infections

Infections caused by virulent Gram-positive bacteria, such as Staphylococcus aureus, group B streptococci and group A streptococci, remain significant causes of morbidity and mortality despite progress in antimicrobial therapy. Despite significant advances in the understanding of the pathogenesis of infection caused by these organisms, there are only limited strategies to prevent infection. In this article, we review efforts to develop safe and effective vaccines that would prevent infections caused by these 3 pathogens.

Invasive infection caused by Streptococcus dysgalactiae subsp. equisimilis: characteristics of strains and clinical features

Among clinically isolated β-hemolytic streptococci, Streptococcus pyogenes and S. agalactiae were considered the main pathogens in humans until recently. In 1996, S. dysgalactiae subsp. equisimilis (SDSE) was proposed as a novel taxon among human-derived streptococcal isolates. SDSE has Lancefield group C or G antigens, exhibits strong β-hemolysis, and exerts streptokinase activity upon human plasminogen and proteolytic activity upon human fibrin. Similarly to group A streptococci, SDSE possesses virulence factors including M protein, streptolysin O, streptolysin S, streptokinase, hyaluronidase, C5a peptidase, and others. SDSE may exist among the normal flora of the skin, oropharynx, and gastrointestinal and genitourinary tracts. In the twenty-first century, invasive SDSE infection (i.e., cellulitis, urosepsis, and pneumonia) leading to various disseminated diseases is being diagnosed increasingly in Japan, elsewhere in Asia, in Europe, and in America. Particularly, among elderly patients, these invasive diseases are encountered increasingly in Japanese hospital emergency departments. Analysis of the part of the emm gene encoding the amino acid sequence at the N-terminal end of the M protein is used to determine the molecular epidemiology of SDSE. The distribution of emm types from patients with invasive or noninvasive infections differs between surveillance results from different countries. In this review, we summarize the characteristics of phenotypes and virulence factors in SDSE strains; the review also focuses on emerging SDSE infectious disease and future vaccination research.

Protective efficacy of group A streptococcal vaccines containing type-specific and conserved M protein epitopes

The amino terminal region of group A streptococcal M proteins evokes type-specific immunity while the conserved C-repeat epitopes evoke cross-protective immunity against multiple serotypes. The present studies were undertaken to compare the protective efficacy of vaccines containing either type-specific (hexavalent vaccine) or conserved C-repeat (J14 vaccine) M protein epitopes and to determine if combination vaccines resulted in enhanced levels of protection. Our results indicated that the protective efficacy of the type-specific vaccine was significantly greater than that of J14 and that the addition of J14 to vaccine formulations did not enhance the level of protection achieved with type-specific formulations.

The NH(2)-terminal region of Streptococcus pyogenes M5 protein confers protection against degradation by proteases and enhances mucosal colonization of mice

BACKGROUND

The NH(2)-terminal sequence of the M protein from group A streptococci defines the serotype of the organism and contains epitopes that evoke bactericidal antibodies.

METHODS

To identify additional roles for this region of the M protein, we constructed a mutant of M5 group A streptococci expressing an M protein with a deletion of amino acid residues 3-22 (DeltaNH(2)).

RESULTS

M5 streptococci and the DeltaNH(2) mutant were resistant to phagocytosis and were similarly virulent in mice. However, DeltaNH(2) was significantly less hydrophobic, contained less lipoteichoic acid on its surface, and demonstrated reduced adherence to epithelial cells. These differences were abolished when organisms were grown in the presence of protease inhibitors. Treatment with cysteine proteases or with human saliva resulted in the release of M protein from the DeltaNH(2) mutant at a significantly greater rate than observed with the wild-type M5 strain. Compared with the parent strain, the DeltaNH(2) strain also showed a significant reduction in its ability to colonize the upper respiratory mucosa of mice.

CONCLUSIONS

The NH(2) terminus of M5 protein has an important role in protecting the surface protein from proteolytic cleavage, thus preserving its function as an anchor for lipoteichoic acid, which is a primary mediator of adherence to epithelial cells and colonization.

Group A streptococcal genotypes from throat and skin isolates in the United Arab Emirates

Background

The bacterium Streptococcus pyogenes causes a variety of human diseases that range from relatively mild skin infections to severe invasive diseases, such as acute rheumatic fever, glomerulonephritis, puerperal sepsis, necrotizing fasciitis, meningitis, and streptococcal toxic shock syndrome. Accurate identification and typing of group A hemolytic streptococci (GAS) is essential for epidemiological and pathogenetic studies of streptococcal diseases. For this reason, The genetic diversity of group A streptococcal (GAS) isolates from subjects in the United Arab Emirates with streptococcal disease was studied using emm gene sequence analysis. The emm typing system which is based on sequence analysis of PCR products of the N-terminal hypervariable region of the M protein gene, concurs with M serotyping almost 1:1.

Findings

A total of 38 GAS isolates were analyzed, including 35 isolates from throat and 3 from skin. Among the 38 isolates, a total of 25 different emm/st types were detected: 20 isolates (53%) belonged to 16 validated standard reference emm types and 18 isolates (47%) belonged to 9 recognized sequence types.

Conclusions

This is the first emm typing study in the United Arab Emirates to demonstrate the heterogeneity of the GAS population.

Epidemiological analysis of Streptococcus pyogenes infections in Hong Kong

AIMS

The aim of this study was to characterise clinical and microbiological features of isolates obtained from both invasive and non-invasive Streptococcus pyogenes infections in Hong Kong, between October 2005 and April 2008.

METHOD

Clinical data of invasive isolates were collected retrospectively. Altogether 281 isolates were emm sequence typed and tested for antimicrobial susceptibility using disk diffusion method. Detection of the presence of the streptococcal pyrogenic exotoxin genes was also carried out.

RESULTS

emm1, emm4 and emm12 were the most prevalent in both the invasive and non-invasive groups with an increase in incidence of emm22 compared with a previous study. emm22 was associated with invasive cellulitis and wound infection. The overall rate of erythromycin resistance was 25.6% and was significantly higher in emm22 strains (85.7%). The phage-encoded superantigen gene speA was exclusively associated with emm1 in both invasive and non-invasive isolates.

CONCLUSION

This study revealed a changing epidemiology of S. pyogenes infection in Hong Kong, with a unique pattern compared with other Asian countries. Invasiveness is not related to the presence of speA, speC or ssa genes and the antimicrobial resistance rate was high for macrolides. The findings have an implication on the use and efficacy of the polyvalent S. pyogenes vaccine under development.

Differences among group A streptococcus epidemiological landscapes: consequences for M protein-based vaccines?

Group A streptococcus (GAS) is a bacterial pathogen responsible for a wide array of disease pathologies in humans. GAS surface M protein plays multiple key roles in pathogenesis, and serves as a target for typing and vaccine development. In this review, we have compiled GAS epidemiological studies from several countries around the world to highlight the consequences on the theoretical efficacy of two different M protein-based vaccine strategies.

Group A streptococcal vaccines: facts versus fantasy

PURPOSE OF REVIEW

This review provides an overview of progress of the development of group A streptococcal (GAS) vaccines with a focus on recent advances.

RECENT FINDINGS

Historically, GAS vaccine development has focused on the N-terminus of the M protein, which ultimately led to successful phase I/II clinical trials of a 26-valent recombinant M protein vaccine in 2004-2005. More recently, interest in antigens conserved among most, if not all, group A streptococci has increased. However, no vaccines containing these antigens have reached clinical trials. Three strategies have been used to develop conserved antigen vaccine candidates: use of the conserved region of the M protein; use of well described virulence factors as antigens, including streptococcal C5a peptidase, streptococcal carbohydrate, fibronectin-binding proteins, cysteine protease and streptococcal pili; and use of reverse vaccinology to identify novel antigens.

SUMMARY

Several vaccine candidates against GAS infection are in varying stages of preclinical and clinical development. Although there is great hope that one of these vaccine candidates will reach licensure in the next decade, only one, the multivalent N-terminal vaccine, has entered clinical trials in the last 30 years. Although strong advocacy for GAS vaccine development is important, there remains an urgent need to institute available public health control measures against GAS diseases globally, particularly in developing countries.

Global emm type distribution of group A streptococci: systematic review and implications for vaccine development

emm sequence typing is the most widely used method for defining group A streptococcal (GAS) strains, and has been applied to isolates in all regions of the world. We did a systematic review of the global distribution of GAS emm types. 102 articles and reports were included (38 081 isolates). Epidemiological data from high-income countries were predominant, with sparse data from low-income countries. The epidemiology of GAS disease in Africa and the Pacific region seems to be different from that in other regions, particularly high-income countries. In Africa and the Pacific, there were no dominant emm types, a higher diversity of emm types, and many of the common emm types in other parts of the world were less common (including emm 1, 4, 6, and 12). Our data have implications for the development of GAS vaccines. On the basis of the available data, the current formulation of the experimental multivalent emm vaccine would provide good coverage in high-income countries, particularly USA, Canada, and Europe, but poor coverage in Africa and the Pacific, and only average coverage in Asia and the Middle East.

Higher rates of streptococcal colonization among children in the Pacific Rim Region correlates with higher rates of group A streptococcal disease and sequelae

Group A streptococcal (GAS) pharyngeal colonization rates were determined among 1061 asymptomatic students in Hawaii and American Samoa where acute rheumatic fever rates are high. All GAS isolates were emm sequence typed. Although pharyngeal colonization rates were low in Hawaii (3.4%), Pacific Islander children had significantly higher colonization rates (5.7% vs. 1.2% in other ethnic groups, p <0.05). The colonization rate was higher in American Samoa (13%). Few emm types that were infrequently observed in symptomatic infections in Hawaii were repeatedly identified in both sites. These emm types were previously described among asymptomatic children suggesting a type-specific association with pharyngeal colonization.

Changing epidemiology of Streptococcus pyogenes emm types and associated invasive and noninvasive infections in Southern Taiwan

A total of 242 isolates were recovered from 76 patients with invasive diseases, 89 with scarlet fever, and 77 with pharyngitis. The most frequent emm types were types 12 (43.4%), 4 (18.2%), and 1 (16.9%). emm12 reemerged in 2005 and peaked in 2007. emm11 was recovered only from patients with invasive disease.

emm and C-repeat region molecular typing of beta-hemolytic Streptococci in a tropical country: implications for vaccine development

We designed a study to investigate the molecular epidemiology of group A streptococcal (GAS) and group C and G streptococcal (GCS and GGS) disease in Fiji, a country which is known to have a high burden of streptococcal disease. Molecular typing of the N-terminal portion (emm typing) of the M protein was performed with 817 isolates (535 GAS and 282 GCS/GGS). We also performed genotyping of the C-repeat region in 769 of these isolates to identify J14 sequence types. The profile of emm types for Fiji was very different from that found for the United States and Europe. There were no dominant emm types and a large number of overlapping types among clinical disease states. Commonly found GAS emm types in industrialized countries, including emm1, emm12, and emm28, were not found among GAS isolates from Fiji. Over 93% of GAS isolates and over 99% of GCS/GGS isolates that underwent J14 sequence typing contained either J14.0 or J14.1. Our data have implications for GAS vaccine development in developing countries and suggest that a vaccine based upon the conserved region of the M protein may be a feasible option for Fiji and potentially for other tropical developing countries.

Vaccines under study: non-HIV vaccines

The development of effective vaccines has been an amazing public health achievement and has resulted in countless lives being saved. Dermatologic therapy has recently been greatly advanced by the licensure of an effective human papillomavirus vaccine and herpes zoster vaccine. Despite these successes, many infectious diseases do not currently have a preventive vaccine. We review potential vaccines against selected infectious agents, including viruses, bacteria, fungi, and protozoa that have cutaneous and mucocutaneous manifestations. The road to licensure of a new vaccine begins with exhaustive preclinical and clinical studies, and many of these will fail before a successful vaccine candidate is approved. This article focuses on vaccines that have yet to be approved for licensure.