Streptococcal superantigens and the return of scarlet fever

Group A Streptococcus vaccine Development: An Indian public health imperative

BACKGROUND

Group A Streptococcus (GAS) is a significant pathogen responsible for a wide range of diseases, including severe complications such as Rheumatic Heart Disease (RHD), which predominantly affect low- and middle-income countries (LMICs) like India. GAS infections impact over 800 million individuals annually, resulting in approximately 639,000 deaths due to RHD complications. Despite significant advancements, developing an effective GAS vaccine has faced several challenges, including the complexity of GAS virulence mechanisms, the diversity of emm types, and the lack of suitable preclinical models. Recent vaccine research has focused on both M protein-based and non-M protein-based vaccines, with several candidates showing promising results. However, current vaccines only address 50 % of the prevalent emm types in India, highlighting the need for further research and development.

OBJECTIVE

This review aims to examine the historical and current progress in GAS vaccine development, identify key challenges, and explore future strategies, with a focus on the Indian public health context.

CONTENT

A comprehensive review of existing literature on GAS and its complications was conducted, focusing on the global and Indian burden of GAS infections, the resurgence of scarlet fever, and the emergence of virulent strains such as M1UK. The study also reviewed recent global initiatives like the Cairo Accord and the 71st World Health Assembly's resolution on RHD to emphasize the need for international collaboration in vaccine development. Continued global cooperation, intensified research efforts, and targeted public health initiatives are essential for overcoming the challenges in GAS vaccine development. Advocacy and investment in this area are crucial for reducing the global burden of GAS infections and their associated complications. This study aims to provide comprehensive genomic data on GAS isolates from India, enabling comparisons with global findings, highlighting regional differences, and contributing to a more comprehensive understanding of GAS epidemiology and pathogenicity.

Streptococcus dysgalactiae subsp. equisimilis infection and its intersection with Streptococcus pyogenes

SUMMARYStreptococcus dysgalactiae subsp. equisimilis (SDSE) is an increasingly recognized cause of disease in humans. Disease manifestations range from non-invasive superficial skin and soft tissue infections to life-threatening streptococcal toxic shock syndrome and necrotizing fasciitis. Invasive disease is usually associated with co-morbidities, immunosuppression, and advancing age. The crude incidence of invasive disease approaches that of the closely related pathogen, Streptococcus pyogenes. Genomic epidemiology using whole-genome sequencing has revealed important insights into global SDSE population dynamics including emerging lineages and spread of anti-microbial resistance. It has also complemented observations of overlapping pathobiology between SDSE and S. pyogenes, including shared virulence factors and mobile gene content, potentially underlying shared pathogen phenotypes. This review provides an overview of the clinical and genomic epidemiology, disease manifestations, treatment, and virulence determinants of human infections with SDSE with a particular focus on its overlap with S. pyogenes. In doing so, we highlight the importance of understanding the overlap of SDSE and S. pyogenes to inform surveillance and disease control strategies.

Diaper dermatitis-a narrative review of clinical presentation, subtypes, and treatment

Diaper dermatitis (DD) is an umbrella term with different clinical presentations, pathophysiology, treatments, and outcomes. The major subtypes include irritant contact dermatitis and candida-associated DD. In case of atypical presentation or unresponsiveness to treatment, other differential diagnoses should be considered. Although DD can occur at any age, it peaks in newborns and infants < 2 years of age. We will focus on this age group in our narrative review.

Mechanisms of host adaptation by bacterial pathogens

The emergence of new infectious diseases poses a major threat to humans, animals, and broader ecosystems. Defining factors that govern the ability of pathogens to adapt to new host species is therefore a crucial research imperative. Pathogenic bacteria are of particular concern, given dwindling treatment options amid the continued expansion of antimicrobial resistance. In this review, we summarize recent advancements in the understanding of bacterial host species adaptation, with an emphasis on pathogens of humans and related mammals. We focus particularly on molecular mechanisms underlying key steps of bacterial host adaptation including colonization, nutrient acquisition, and immune evasion, as well as suggest key areas for future investigation. By developing a greater understanding of the mechanisms of host adaptation in pathogenic bacteria, we may uncover new strategies to target these microbes for the treatment and prevention of infectious diseases in humans, animals, and the broader environment.

Characterization of group A streptococci causing invasive diseases in Sri Lanka

Group A β haemolytic streptococcus (GAS) or Streptococcus pyogenes is a human pathogen that causes an array of infections, including pharyngitis, cellulitis, impetigo, scarlet fever, toxic shock syndrome, and necrotizing fasciitis. The present study characterizes 51 GAS isolates from invasive infections in Sri Lanka, focusing on resistance profiles, genetic determinants of resistance, and virulence markers. Isolates were tested for sensitivity to penicillin, erythromycin, clindamycin, and tetracycline. The presence of erm(A), erm(B), and mef(A) was detected in erythromycin-resistant isolates, while tet(M) was detected in the tetracycline-resistant isolates. PCR was used to identify SpeA, SpeB, SpeC, SpeF, SpeG, smez, and ssa as virulence markers. Selected GAS isolates were emm-typed using the updated CDC protocol. All 51 isolates were susceptible to penicillin. The number of isolates non-susceptible to erythromycin was 16. The commonest resistance determinant identified was erm(B) (11/16). Tetracycline non-susceptibility was found in 36 (70.6 %) isolates and 26 of them contained the tet(M) gene. Thirteen (25.5 %) isolates were resistant to both tetracycline and erythromycin, while 12 (23.5 %) isolates were sensitive to both antibiotics. The commonest virulence markers detected among the isolates were SpeB (44, 86.3 %), SpeG (36, 70.6 %), and SpeF (35, 68.6 %), while SpeJ (15, 29.4 %), SpeA (10, 19.6 %), and ssa (5,9.8 %) were less common. The emm types were diverse. In conclusion, the GAS isolates studied showed resistance to erythromycin and tetracycline, while retaining universal susceptibility to penicillin. Additionally, these isolates exhibited diverse genetic backgrounds, displaying varying patterns of virulence genes and emm types.

Novel insights into the immune response to bacterial T cell superantigens

Bacterial T cell superantigens (SAgs) are a family of microbial exotoxins that function to activate large numbers of T cells simultaneously. SAgs activate T cells by direct binding and crosslinking of the lateral regions of MHC class II molecules on antigen-presenting cells with T cell receptors (TCRs) on T cells; these interactions alter the normal TCR-peptide-MHC class II architecture to activate T cells in a manner that is independent of the antigen specificity of the TCR. SAgs have well-recognized, central roles in human diseases such as toxic shock syndrome and scarlet fever through their quantitative effects on the T cell response; in addition, numerous other consequences of SAg-driven T cell activation are now being recognized, including direct roles in the pathogenesis of endocarditis, bloodstream infections, skin disease and pharyngitis. In this Review, we summarize the expanding family of bacterial SAgs and how these toxins can engage highly diverse adaptive immune receptors. We highlight recent findings regarding how SAg-driven manipulation of the adaptive immune response may operate in multiple human diseases, as well as contributing to the biology and life cycle of SAg-producing bacterial pathogens.

Detection of toxigenic M1UK lineage group A Streptococcus clones in Taiwan

BACKGROUND

A new sublineage of emm1 group A Streptococcus (GAS), M1UK, has emerged in Europe, North America, and Australia. Notably, a significant portion of emm1 isolates in Asia, particularly in Hong Kong and mainland China, acquired scarlet fever-associated prophages following the 2011 Hong Kong scarlet fever outbreak. However, the presence of the M1UK sublineage has not yet been detected in Asia.

METHODS

This study included 181 GAS isolates (2011-2021). The emm type of these isolates were determined, and 21 emm1 isolates from blood or pleural fluid (2011-2021) and 10 emm1 isolates from throat swabs (2016-2018) underwent analysis. The presence of the scarlet fever-associated prophages and the specific single nucleotide polymorphisms of the M1UK clone were determined by polymerase chain reaction and the genome sequencing.

RESULTS

The M1UK lineage strains from throat swab and blood samples were identified. One of the M1UK strain in Taiwan carried the scarlet fever-associated prophage and therefore acquired the ssa, speC, and spd1 toxin repertoire. Nonetheless, the increase of M1UK was not observed until 2021, and there was a reduction in the diversity of emm types in 2020-2021, possibly due to the COVID-19 pandemic restriction policies in Taiwan.

CONCLUSIONS

Our results suggested that the M1UK lineage clone has introduced in Taiwan. In Taiwan, the COVID-19 restrictions were officially released in March 2023; therefore, it would be crucial to continuously monitor the M1UK expansion and its related diseases in the post COVID-19 era.

Blocking Superantigen-Mediated Diseases: Challenges and Future Trends

Superantigens are virulence factors secreted by microorganisms that can cause various immune diseases, such as overactivating the immune system, resulting in cytokine storms, rheumatoid arthritis, and multiple sclerosis. Some studies have demonstrated that superantigens do not require intracellular processing and instated bind as intact proteins to the antigen-binding groove of major histocompatibility complex II on antigen-presenting cells, resulting in the activation of T cells with different T-cell receptor Vβ and subsequent overstimulation. To combat superantigen-mediated diseases, researchers have employed different approaches, such as antibodies and simulated peptides. However, due to the complex nature of superantigens, these approaches have not been entirely successful in achieving optimal therapeutic outcomes. CD28 interacts with members of the B7 molecule family to activate T cells. Its mimicking peptide has been suggested as a potential candidate to block superantigens, but it can lead to reduced T-cell activity while increasing the host's infection risk. Thus, this review focuses on the use of drug delivery methods to accurately target and block superantigens, while reducing the adverse effects associated with CD28 mimic peptides. We believe that this method has the potential to provide an effective and safe therapeutic strategy for superantigen-mediated diseases.

Patterns in the Incidence of Scarlet Fever Among Children Aged 0-9 Years - China, 2010-2019

Introduction

This study investigates the patterns of scarlet fever among Chinese children aged 0-9 years from 2010 to 2019. The objective is to provide insights that may inform potential adjustments to China's current prevention and control tactics for this illness.

Methods

The present study utilized data on the occurrence of scarlet fever in children from 2010 to 2019, sourced from the National Notifiable Disease Reporting System database, managed by the Chinese Center for Disease Control and Prevention. This research implemented SAS9.4 software to construct trajectory models representing the temporal incidence of scarlet fever, accounting for key variables such as sex, geographic region, urban versus rural dwellings, and various age brackets.

Results

From 2010 to 2019, a total of 554,695 scarlet fever cases were reported among children aged 0-9 years in the 31 mainland Chinese provincial-level administrative divisions, signifying a rate of 35.36 per 100,000 individuals. An inconsistent yet generally rising trend was observed, evidenced by a 3.17-fold increase in reported cases and a 3.02-fold escalation in incidence rate over this period. Examination of these trends revealed three distinctive developmental patterns for both males and females, with the lowest prevalence in the first trajectory and the highest in the third. The incidence was consistently higher among males than females in all trajectories. The urban and northern regions displayed equal or greater trajectory rates than their rural and southern counterparts, respectively. In terms of age groups, the lowest incidence was observed in the 0-1-year age group, while the highest was recorded in the 4-5 and 6-7-year age groups.

Conclusions

Between 2010 and 2019, there was a marked increase in the incidence of scarlet fever among children in China. The disease predominantly impacts urban-dwelling children, ranging from 4 to 7 years old, in the northern regions of the country. The incidence is reported to be higher among boys compared to girls.

Recrudescence of Scarlet Fever and Its Implications for Dental Professionals

A significant increase in the incidence of scarlet fever, mainly in Europe, has been noted during the COVID-19 postpandemic period. Scarlet fever is caused by a pyrogenic exotoxin-producing streptococcus-Streptococcus pyogenes-responsible for more than 500,000 deaths annually worldwide. Superantigens (SAgs) secreted by this Group A streptococcus (GAS) usually overstimulate the human immune system, causing an amplified hypersensitivity reaction leading to initial symptoms such as sore throat, high fever, and a sandpaper-like skin rash. There could be concurrent oral manifestations known as "strawberry tongue" or "raspberry tongue," which may be first noted by oral health professionals. The early diagnosis and treatment of this disease is critical to obviate the development of local and systemic sequelae such as acute rheumatic fever, endocarditis, and glomerulonephritis. Antibiotics should be prescribed early to mitigate its duration, sequelae, and community spread. Dental practitioners should be aware of the early symptoms of scarlet fever for infection detection, emergency patient management, and appropriate referral. This concise review outlines the prevalence, pathogenicity, oral and systemic manifestations, as well as the dental implications of scarlet fever.

Methods to Analyze the Contribution of Complement Evasion Factor (CEF) to Streptococcus pyogenes Virulence

Group A Streptococcus (GAS, Streptococcus pyogenes) is an exclusively human pathogen that causes a range of diseases, including pharyngitis, tonsillitis, impetigo, erysipelas, necrotizing fasciitis, and toxic shock syndrome. Post-streptococcal sequelae include acute rheumatic fever and rheumatic heart disease. The bacterium produces a large arsenal of virulence factors that contribute to host tissue adhesion/colonization, bacterial spread, and host immune evasion. Immune evasion factors include proteins that interfere with complement, a system of plasma proteins that are activated by pathogens resulting in a variety of reactions on the surface of the pathogen. This leads to the activation of active components with a variety of effector functions, such as cell lysis, opsonization, and chemotaxis of phagocytes to the site of infection. We have recently identified a novel "complement evasion factor" (CEF) in S. pyogenes. CEF directly interacts with complement proteins C1r, C1s, C3, and C5, interrupts all three complement pathways, and prevents opsonization of the bacterial surface with C3b. We here present methods used to analyze the complement interference of CEF.

Functional and Transcriptome Analysis of Streptococcus pyogenes Virulence on Loss of Its Secreted Esterase

Esterases are broadly expressed in bacteria, but much remains unknown about their pathogenic effect. In previous studies, we focused on an esterase secreted by Streptococcus pyogenes (group A Streptococcus, GAS). Streptococcal secreted esterase (Sse) can hydrolyze the sn−2 ester bonds of platelet−activating factor (PAF), converting it to an inactive form that inhibits neutrophil chemotaxis to the infection sites. However, as a virulent protein, Sse probably participates in GAS pathogenesis far beyond chemotaxis inhibition. In this study, we generated the sse gene knockout strain (Δsse) from the parent strain MGAS5005 (hypervirulent M1T1 serotype) and compared the difference in phenotypes. Absence of Sse was related to weakened skin invasion in a murine infection model, and significantly reduced GAS epithelial adherence, invasion, and intracellular survival. Reduced virulence of the Δsse mutant strain was explored through transcriptome analysis, revealing a striking reduction in the abundance of invasive virulence factors including M protein, SIC, ScpA, and SclA. Besides the influence on the virulence, Sse also affected carbohydrate, amino acid, pyrimidine, and purine metabolism pathways. By elucidating Sse−mediated pathogenic process, the study will contribute to the development of new therapeutic agents that target bacterial esterases to control clinical GAS infections.