Molecular Biology of Group A Streptococcus and its Implications in Vaccine Strategies

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.

Unveiling the Group A Streptococcus Vaccine-Based L-Rhamnose from Backbone of Group A Carbohydrate: Current Insight Against Acute Rheumatic Fever to Reduce the Global Burden of Rheumatic Heart Disease

Group A Streptococcus (GAS) is a widely distributed bacterium that is Gram-positive and serves as the primary cause of acute rheumatic fever (ARF) episodes. Rheumatic heart disease (RHD) is a sequela resulting from repeated ARF attacks which are also caused by repeated GAS infections. ARF/RHD morbidity and mortality rates are incredibly high in low- and middle-income countries. This is closely related to poor levels of sanitation which causes the enhanced incidence of GAS infections. Management of carditis in RHD cases is quite challenging, particularly in developing countries, considering that medical treatment is only palliative, while definitive treatment often requires more invasive procedures with high costs. Preventive action through vaccination against GAS infection is one of the most effective steps as a solution in reducing RHD morbidity and mortality due to curative treatments are expensive. Various developments of M-protein-based GAS vaccines have been carried out over the last few decades and have recently begun to enter the clinical stage. Nevertheless, this vaccination generates cross-reactive antibodies that might trigger ARF assaults as a result of the resemblance between the M-protein structure and proteins found in many human tissues. Consequently, the development of a vaccine utilizing L-Rhamnose derived from the poly-rhamnose backbone of Group A Carbohydrate (GAC) commenced. The L-Rhamnose-based vaccine was chosen due to the absence of the Rhamnose biosynthesis pathway in mammalian cells including humans thus this molecule is not found in any body tissue. Recent pre-clinical studies reveal that L-Rhamnose-based vaccines provide a protective effect by increasing IgG antibody titers without causing cross-reactive antibodies in test animal tissue. These findings demonstrate that the L-Rhamnose-based vaccine possesses strong immunogenicity, which effectively protects against GAS infection while maintaining a significantly higher degree of safety.

Group A Streptococcus Infections: Their Mechanisms, Epidemiology, and Current Scope of Vaccines

Group A streptococci (GAS) are gram-positive, cocci-shaped bacteria that cause a wide variety of infections and are a cause of significant health burden, particularly in lower- and middle-income nations. The GAS genome contains a number of virulence factors such as the M-protein, hyaluronic acid, C5a peptidase, etc. Despite its significant health burden across the globe, a proper vaccine against GAS infections is not yet available. Various candidates for an effective GAS vaccine are currently being researched. These are based on various parts of the streptococcal genome. These include candidates based on the N-terminal region of the M protein, the conserved C-terminal region of the M protein, and other parts of the streptococcal genome. The development of a vaccine against GAS infections is hampered by certain challenges, such as extensive genetic heterogeneity and high protein sequence variation. This review paper sheds light on the various virulence factors of GAS, their epidemiology, the different vaccine candidates currently being researched, and the challenges associated with M-protein and non-M-protein-based vaccines. This review also sheds light on the current scenario regarding the status of vaccine development against GAS-related infections.

Chlorogenic acid exerts antibacterial effects by affecting lipid metabolism and scavenging ROS in Streptococcus pyogenes

Chlorogenic acid (CGA), one of the most abundant polyphenols in the human diet, exhibits many biological properties, including antibacterial properties. Numerous studies have investigated the antibacterial effects of CGA, however, the molecular mechanisms governing its effects against Streptococcus pyogenes have not been fully elucidated. Streptococcus pyogenes is a Gram-positive pathogen that causes a wide range of human infections and postinfectious immune-mediated disorders. In this study, we used an isobaric tagging for relative and absolute quantitation (iTRAQ)-based proteomic technique to investigate the underlying mode of action of CGA against S. pyogenes. KEGG and GO analyses indicated that CGA affected the expression of protein alterations involved in multiple pathways, downregulating the expression of ribosomal proteins, and upregulating the expression of proteins associated with fatty acid metabolism, pyruvate metabolism, and propanoate metabolism, while activating the expression of oxidation-reduction-related proteins. Moreover, further cell-based experiments verified that CGA scavenges intracellular ROS in S. pyogenes. These results suggest that CGA may exert its antibacterial action through several actions, such as downregulating ribosomal subunits, affecting lipid metabolism, and scavenging intracellular ROS. The results of this study may help to elucidate the molecular mechanisms by which CGA combats pathogens.

Group A Streptococcal Infection During Pregnancy and the Postpartum Period

Group A Streptococcus, the causative organism for "childbed fever," continues to pose a threat to women during pregnancy and the postpartum period, despite advances in hygiene and the development of antibiotic therapy. This resilient bacterium has resurfaced with intensified virulence, and, for reasons not entirely clear, causes severe disease in some women. Sepsis and toxic shock syndrome caused by Group A Streptococcus contribute to the alarming rates of maternal morbidity and mortality in the United States. Early recognition of the subtle signs and symptoms of sepsis is critical to decrease the risk for mortality; however, early signs can be elusive during the perinatal period because of the physiologic changes of pregnancy. Care management requires a coordinated, collaborative, multidisciplinary team approach. Sepsis is a clinical emergency, and health care providers need to respond as a well-prepared team.

Decoding the molecular epidemiology of group A streptococcus - an Indian perspective

PURPOSE

Unlike western countries the knowledge of group A streptococcus (GAS) epidemiology in India remains patchy and incomplete. Typing is crucial for surveillance as well as in predicting the efficacy of multivalent M protein vaccine. The present study aimed to explore the emm types of 206 invasive and non-invasive GAS isolates from South India as well as reviewing all the published literature on GAS molecular epidemiology from India thereby generating a pan-Indian data to predict the conjectural coverage of the 30-valent M-protein vaccine in this population.

METHODOLOGY

emm typing and superantigen (SAg) profiling of GAS along with reviewing literatures on GAS molecular epidemiology from India.

RESULTS

This study revealed a high diversity of emm types with emm 63, 82, 183, 85, 92, 169, 42, 44, 106, 74, 12 being frequently encountered, belonging to twenty emm clusters. The pan-Indian data on prevalent emm types further supports our study findings with 135 emm different types. Six clusters dominated accounting for 80 % of the GAS isolates: E3(26 %), E6(20 %), E2(11 %), E4(10 %), D4(7 %), E1(6 %). No significant association was noted between emm types and the nature of infection (P≥0.05) while a few SAg profiles were significantly associated with certain emm types. Pan Indian data revealed that only 16 % of the emm types encountered were included in proposed 30-valent M protein based vaccine.

CONCLUSION

The coverage among the South Indian GAS isolates was 28.2 % which increased to only 46.6 % with the cross-opsonic effect, thus highlighting the importance of developing a specific multivalent vaccine including the prevalent emm types in India or considering the use of conserved C-repeat vaccines and non-M protein based vaccines.

Whole genome shotgun sequences of Streptococcus pyogenes causing acute pharyngitis from India

Streptococcus pyogenes, belonging to group A streptococcus (GAS), causes over 600 million infections annually being a predominant human pathogen. Lack of genomic data on GAS from India is one limitation to understand its virulence and antimicrobial resistance determinants. The genome of GAS isolates from clinical samples collected at Navi Mumbai, India was sequenced and annotated. Sequencing was performed on Ion Torrent PGM platform. The size of annotated S. pyogenes genomes ranged from ~1.69 to ~1.85 Mb with coverage of 38× to 189×. Most of the isolates had msr(D) and mef(A), and four isolates had erm(B) gene for macrolide resistance. The genome harboured multiple virulence factors including exotoxins in addition to phage elements in all GAS genomes. Four isolates belonged to sequence type ST28, 7 were identified as ST36 and 1 as ST55.