Streptococcus pyogenes: Pathogenesis and the Current Status of Vaccines

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.

Characterization of an IL-8 cleavage inhibition assay to determine the functionality of anti-SpyCEP antibodies in human sera

Exposure to Group A Streptococcus leads to a broad spectrum of disease and sequelae, as the bacterium employs a wide range of virulence factors to facilitate colonization of the host, propagation and onward transmission, disrupting both innate and adaptive immune responses. The protease SpyCEP has a crucial role in contributing to bacterial immune evasion by impairing neutrophil recruitment and killing of bacteria through the cleavage of interleukin-8 (IL-8). Given this critical function, SpyCEP represents a key vaccine antigen and quantifying functional anti-SpyCEP antibodies represents not only an important marker of vaccine efficacy, but also a tool to dissect the natural immune response. Here, we report the development and characterization of an IL-8 cleavage inhibition assay to measure the function of anti-SpyCEP antibodies in human sera. The assay was demonstrated to be sensitive, highly specific, linear and reproducible, and suitable for evaluating the function of anti-SpyCEP antibodies induced in humans in vaccine clinical trials and in observational studies of natural immunity.

Acute rheumatic fever and rheumatic heart disease: updates in diagnosis and treatment

PURPOSE OF REVIEW

To summarize the latest developments in rheumatic fever and rheumatic heart disease (RHD) prevention, (early) diagnosis, and treatment.

RECENT FINDINGS

The revised Jones criteria have demonstrated increased sensitivity and specificity for rheumatic fever diagnosis in high-risk populations. The management of rheumatic fever remains symptom-based, with no treatment options proven to alter the disease course or prevent chronic RHD. The revised World Heart Federation (WHF) guidelines for the echocardiographic diagnosis of RHD encourage task-shifting of RHD screening, extending reach in endemic regions. These guidelines also present an A-D classification of RHD and provide recommendations for the management of early disease. Integrated models for RHD screening within existing health structures are emerging and automated intelligence is showing potential to support RHD screening and diagnosis. Innovative strategies to foster adherence and equitable access to secondary prophylaxis, such as re-examination of the efficacy of oral penicillin, trials of longer acting penicillin formulations and implants are underway. There is renewed interest and investment in a well tolerated and effective GAS vaccine.

SUMMARY

We are living in a time of possibility with global acceleration to address the prevailing burden of RHD. Together, we can ensure that RHD does not once again fall off the global health agenda, until equitable elimination has been achieved.

Group A Streptococcal Infections in Pediatric Age: Updates about a Re-Emerging Pathogen

Group A Streptococcus (GAS) presents a significant global health burden due to its diverse clinical manifestations ranging from mild infections to life-threatening invasive diseases. While historically stable, the incidence of GAS infections declined during the COVID-19 pandemic but resurged following the relaxation of preventive measures. Despite general responsiveness to β-lactam antibiotics, there remains an urgent need for a GAS vaccine due to its substantial global disease burden, particularly in low-resource settings. Vaccine development faces numerous challenges, including the extensive strain diversity, the lack of suitable animal models for testing, potential autoimmune complications, and the need for global distribution, while addressing socioeconomic disparities in vaccine access. Several vaccine candidates are in various stages of development, offering hope for effective prevention strategies in the future.

Testing a Recombinant Form of Tetanus Toxoid as a Carrier Protein for Glycoconjugate Vaccines

Glycoconjugate vaccines play a major role in the prevention of infectious diseases worldwide, with significant impact on global health, enabling the polysaccharides to induce immunogenicity in infants and immunological memory. Tetanus toxoid (TT), a chemically detoxified bacterial toxin, is among the few carrier proteins used in licensed glycoconjugate vaccines. The recombinant full-length 8MTT was engineered in E. coli with eight individual amino acid mutations to inactivate three toxin functions. Previous studies in mice showed that 8MTT elicits a strong IgG response, confers protection, and can be used as a carrier protein. Here, we compared 8MTT to traditional carrier proteins TT and cross-reactive material 197 (CRM197), using different polysaccharides as models: Group A Streptococcus cell-wall carbohydrate (GAC), Salmonella Typhi Vi, and Neisseria meningitidis serogroups A, C, W, and Y. The persistency of the antibodies induced, the ability of the glycoconjugates to elicit booster response after re-injection at a later time point, the eventual carrier-induced epitopic suppression, and immune interference in multicomponent formulations were also evaluated. Overall, immunogenicity responses obtained with 8MTT glycoconjugates were compared to those obtained with corresponding TT and, in some cases, were higher than those induced by CRM197 glycoconjugates. Our results support the use of 8MTT as a good alternative carrier protein for glycoconjugate vaccines, with advantages in terms of manufacturability compared to TT.