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.

An assessment of the airborne longevity of group A Streptococcus

Group A streptococcus (GAS) infections result in more than 500 000 deaths annually. Despite mounting evidence for airborne transmission of GAS, little is known about its stability in aerosol. Measurements of GAS airborne stability were carried out using the Controlled Electrodynamic Levitation and Extraction of Bioaerosols onto a Substrate (CELEBS) instrument. CELEBS measurements with two different isolates of GAS suggest that it is aerostable, with approximately 70 % of bacteria remaining viable after 20 min of levitation at 50 % relative humidity (RH), with lower survival as RH was reduced. GAS airborne viability loss was driven primarily by desiccation and efflorescence (i.e. salt crystallization), with high pH also potentially playing a role, given reduced survival in bicarbonate containing droplet compositions. At low enough RH for efflorescence to occur, a greater proportion of organic components in the droplet appeared to protect the bacteria from efflorescence. These first insights into the aerosol stability of GAS indicate that airborne transmission of these respiratory tract bacteria may occur, and that both the composition of the droplet containing the bacteria, and the RH of the air affect the duration of bacterial survival in this environment. Future studies will explore a broader range of droplet and air compositions and include a larger selection of GAS strains.

The potential global cost-effectiveness of prospective Strep A vaccines and associated implementation efforts

Group A Streptococcus causes a wide range of diseases from relatively mild infections including pharyngitis to more severe illnesses such as invasive diseases and rheumatic heart disease (RHD). Our aim is to estimate the cost-effectiveness of a hypothetical Strep A vaccine on multiple disease manifestations at the global-level. Cost-effectiveness analyses were carried out by building on the potential epidemiological impact of vaccines that align with the WHO's Preferred Product Characteristics for Strep A vaccines. Maximum vaccination costs for a cost-effective vaccination strategy were estimated at the thresholds of 1XGDP per capita and health opportunity costs. The maximum cost per fully vaccinated person for Strep A vaccination to be cost-effective was $385-$489 in high-income countries, $213-$312 in upper-income-income countries, $74-$132 in lower-middle-income countries, and $37-$69 in low-income countries for routine vaccination at birth and 5 years of age respectively. While the threshold costs are sensitive to vaccine characteristics such as efficacy, and waning immunity, a cost-effective Strep A vaccine will lower morbidity and mortality burden in all income settings.

Burden of Group A Streptococcal Pharyngitis, Rheumatic Fever, and Rheumatic Heart Disease in India: A Systematic Review and Meta-Analysis

OBJECTIVE

To estimate the burden of group A streptococcal pharyngitis (GAS) pharyngitis, rheumatic fever (RF), and rheumatic heart disease (RHD) in India using existing data sources, as well as to recognize the most serious gaps in GAS disease burden data.

METHODS

Four electronic databases-PubMed, Scopus, Embase, and Web of Science were searched using a comprehensive search strategy. Data were identified primarily from observational studies including school surveys, community-based and hospital-based studies. The standard methodological procedures as per Cochrane guidelines were used. Eligible studies were pooled for estimating prevalence, incidence, and case fatality rate using R software version 3.3.3. The protocol was registered with PROSPERO; registration number CRD42018075742.

RESULTS

The pooled prevalence of GAS pharyngitis among asymptomatic children and pharyngitis cases aged 5 to 15 y was estimated as 2.79 percent [95% Confidence interval (CI): 1.58-4.89] and 13 percent (95% CI: 3.18-41.97), respectively. The prevalence rate of rheumatic fever was found to be 0.04% (95% CI: 0.01-0.17). The pooled prevalence rate of RHD among children aged 5-15 y using clinical auscultation and echocardiography was estimated as 0.36 percent (95% CI: 0.02-7.52) and 0.28 percent (95% CI: 0.08-1.03), respectively.

CONCLUSION

The study emphasizes the importance of developing a population-based surveillance framework to track patterns, management strategies, and outcomes in order to develop informed recommendations for launching contextual measures to regulate RF and RHD.

High Diversity of emm Types and Marked Tetracycline Resistance of Group A Streptococci and Other ß-Hemolytic Streptococci in Gabon, Central Africa

BACKGROUND

Group A ß-hemolytic streptococcus (GABHS) is a leading pathogen worldwide and post-streptococcal sequelae is a major cause of morbidity and mortality in resource-limited countries. The M protein (coded by the emm gene) is a key virulence factor and a component of GABHS vaccine candidates. As data on BHS in Central Africa are scarce, antibiotic resistance, emm diversity and potential vaccine coverage were investigated.

METHODS

In a prospective cross-sectional study, 1014 Gabonese were screened for streptococcal throat carriage, tonsillopharyngitis and pyoderma by throat and skin smear tests. All BHS were isolated, species were identified and analysis of antibiotic resistance, emm types and emm clusters was performed.

RESULTS

One hundred sixty-five BHS were detected, comprising 76 GABHS, 36 group C ß-hemolytic streptococcus (GCBHS) and 53 group G ß-hemolytic streptococcus (GGBHS) in 140 carrier, 9 tonsillopharyngitis and 16 pyoderma isolates. Eighty percentage of GABHS, 78% of GCBHS and 79% of GGBHS were tetracycline resistant. Forty-six emm types were identified. GABHS emm58, emm65 and emm81 were most prevalent (26%). Emm diversity of GABHS was the highest, GCBHS and GGBHS were less divers. Every second GABHS, every third GCBHS and every tenth GGBHS carrier was colonized with emm types detected in tonsillopharyngitis or pyoderma isolates.

CONCLUSIONS

Tetracycline resistance and emm type diversity was high among BHS carriers in Gabon with a potential coverage of 58% by the 30-valent GABHS vaccine. A relevant overlap of carrier emm types with emm types found in tonsillopharyngitis and pyoderma characterizes a shared pool of circulating BHS strains.

Secondary prevention of rheumatic heart disease in Ethiopia: a multicenter study

BACKGROUND

Ethiopia has a high acute rheumatic fever (ARF) and rheumatic heart disease (RHD) prevalence, and to our knowledge, there are no data on the status of secondary prevention in children with RHD. This study describes the status of secondary RHD prevention.

METHODS

A multicenter, prospective study was performed on children aged 5-17 years with RHD in Ethiopia. Good adherence was defined as at least 80% completion of benzathine penicillin (BPG) or oral Amoxicillin within the previous year. The primary outcome measure was adherence to prophylaxis, expressed as a proportion. Socio-demographics, severity of RHD, and ARF recurrence were evaluated.

RESULTS

A total of 337 children with a mean age of 12.9 ± 2.6 years were included. The majority (73%) had severe aortic/mitral disease. Participants were on BPG (80%) or Amoxicillin (20%) prophylaxis. Female sex (P = 0.04) use of BPG (0.03) and shorter mean duration of prophylaxis in months (48.5 ± 31.5 vs. 60.7 ± 33, respectively, P < 0.008) predicted good adherence. Running out of medications (35%), interrupted follow-up (27%), and the COVID-19 pandemic (26%) were the most common reasons for missing prophylaxis. Recurrence of ARF was higher in participants on Amoxicillin compared with BPG (40% vs. 16%, P < 0.001) and in those with poor adherence compared with good adherence (36.8% vs. 17.9%, respectively, P = 0.005). Type and duration of prophylaxis (OR 0.5, CI = 0.24, 0.9, P = 0.02; OR = 1.1, CI = 1.1, 1.2, P = 0.04, respectively), and sex (OR = 1.9, CI = 1.1, 3.4, P = 0.03) were independent predictors of poor adherence.

CONCLUSION

Poor adherence is prevalent in Ethiopian children living with RHD. Amoxicillin is a suboptimal option for prophylaxis as its use is associated with lower adherence and a higher rate of ARF recurrence.

Pediatric rheumatic carditis in Italy and Rwanda: The same disease, different socio-economic settings

BACKGROUND

Acute Rheumatic Fever and Rheumatic Heart Disease are the leading cause of acquired heart disease in Low-Income Countries, and a common cause in High-Income Countries. We compared rheumatic carditis, its echocardiographic presentation at diagnosis and its progression in Italy and Rwanda.

METHODS

Retrospective study including all consecutive patients diagnosed with rheumatic carditis in an Italian (IT) and two Rwandan Hospitals (RW). Echocardiography was performed at diagnosis and three follow-up visits. Baseline characteristics, history of primary and secondary prophylaxis and cardiovascular complications data were collected.

RESULTS

Seventy-nine and 135 patients were enrolled in IT and RW, respectively. Mitral regurgitation was the most common lesion (IT: 70%, RW: 96%) in both cohorts; mixed valve lesions and severe lesions were more prevalent in RW. Age at diagnosis (IT: 8.4 ± 2.9 yrs.; RW: 11.1 ± 2.7 yrs.; P < 0.001), adherence to secondary prophylaxis (IT: 99%; RW: 48%; P < 0.001) and history of primary prophylaxis (IT: 65%; RW: 6%; P < 0.001) were different. During the follow-up, native valve lesions completely resolved in 38% of IT and in 2% of RW patients (P < 0.001). By contrast, cardiac surgery was performed in 31% of RW and 5% of IT patients (P < 0.001). Cardiovascular complications and death were only observed in RW.

CONCLUSIONS

The more severe cardiac involvement, the higher rate of valve surgery, CV complications and deaths in RW, could be due to delayed diagnosis and treatment, scarce adherence to secondary prophylaxis and differences in social determinants of health.

Transcatheter Aortic Valve Replacement in Rheumatic Aortic Stenosis: A Comprehensive Review

Rheumatic heart disease (RHD) mainly affects people in developing, low-income countries. However, due to globalization and migration, developed countries are now seeing more cases of RHD. In RHD patients who develop severe symptomatic aortic stenosis, surgical aortic valve replacement remains the treatment of choice. In the past decade, there has been an extension of transcatheter aortic valve replacement (TAVR) to intermediate-risk and lower-risk patients with aortic stenosis. This review suggests the possible utility of TAVR for the treatment of rheumatic aortic stenosis. Rheumatic aortic stenosis has been excluded from major TAVR studies due to the predominantly noncalcific pathology of the rheumatic aortic valve. However, there have been case reports and case series showing successful implantation of the valve even in patients with and without significant leaflet calcification. In this review article, we summarize the latest evidence of severe rheumatic aortic stenosis treated with TAVR and discuss the procedure's impact on patient care, safety, and efficacy.

Disparate Effects of Invasive Group A Streptococcus on Native Americans

Active surveillance of invasive group A Streptococcus (iGAS) disease indicates that its incidence in the US general population is low, but limited studies show rates for American Indians and Alaska Natives (AI/AN) are severalfold higher. Major disparities in rates of iGAS exist between Indigenous and non-Indigenous populations of Australia, New Zealand, and Canada, but much less is understood about iGAS among AI/AN in the United States. Although complex host-pathogen interactions influence the rates of iGAS, including strain variation and virulence, the number and type of concurrent conditions, and socioeconomic status, the relative contribution of each remains unclear. We highlight the poor correlation between the substantial effect of iGAS among Indigenous persons in industrialized countries and the current understanding of factors that influence iGAS disease in these populations. Prospective, large-scale, population-based studies of iGAS are needed that include AI/AN as a necessary first step to understanding the effects of iGAS.

Case Ascertainment on Australian Registers for Acute Rheumatic Fever and Rheumatic Heart Disease

In Australia, disease registers for acute rheumatic fever (ARF) and rheumatic heart disease (RHD) were previously established to facilitate disease surveillance and control, yet little is known about the extent of case-ascertainment. We compared ARF/RHD case ascertainment based on Australian ARF/RHD register records with administrative hospital data from the Northern Territory (NT), South Australia (SA), Queensland (QLD) and Western Australia (WA) for cases 3-59 years of age. Agreement across data sources was compared for persons with an ARF episode or first-ever RHD diagnosis. ARF/RHD registers from the different jurisdictions were missing 26% of Indigenous hospitalised ARF/RHD cases overall (ranging 17-40% by jurisdiction) and 10% of non-Indigenous hospitalised ARF/RHD cases (3-28%). The proportion of hospitalised RHD cases (36%) was half the proportion of hospitalised ARF cases (70%) notified to the ARF/RHD registers. The registers were found to capture few RHD cases in metropolitan areas (SA Metro: 13%, QLD Metro: 35%, WA Metro: 14%). Indigenous status, older age, comorbidities, drug/alcohol abuse and disease severity were predictors of cases appearing in the hospital data only (p < 0.05); sex was not a determinant. This analysis confirms that there are biases associated with the epidemiological analysis of single sources of case ascertainment for ARF/RHD using Australian data.

Postinfectious Glomerulonephritis

Postinfectious glomerulonephritis continues to be the most common cause of acute glomerulonephritis in children. Although in the past it was considered to be mainly a complication of streptococcal infections, today it is well known that infection with many other pathogens may trigger an immune response that results in glomerular injury. Most children with postinfectious glomerulonephritis have an excellent prognosis with complete recovery of renal function and no recurrence. This article summarizes the history, presentation, evaluation, differential diagnosis, and management of children with postinfectious glomerulonephritis. [Pediatr Ann. 2020;49(6):e273-e277.].

Systematic Review of Group A Streptococcal emm Types Associated with Acute Post-Streptococcal Glomerulonephritis

Acute post-streptococcal glomerulonephritis (APSGN) is a postinfectious immune-mediated kidney disease associated with group A Streptococcus (GAS). The prevalence of APSGN varies within and between countries and is influenced by socioeconomic, host, and bacterial factors. The disease is more prevalent in developing countries and resource-poor settings of developed countries, such as the Indigenous populations residing in tropical Australia. The M-protein is a universally present GAS surface antigen that is the focus of molecular typing and vaccine research. Early reports suggested that some M-proteins (emm types) are more likely to cause APSGN than others. Here, we present the first systematic review of the global distribution of APSGN-associated GAS emm types. There were 46 emm types among the 676 cases described in 15 reviewed articles. Only 43% APSGN cases would have had theoretical coverage from the experimental M protein-based GAS vaccine. Vaccine coverage was higher in regions such as North America (97%) and the United Kingdom (98%) than Africa (67%) and Australia (38%). Variable vaccine coverage against APSGN- associated emm types highlights the need for further research into this disease, particularly in settings of poverty, where APSGN prevalence is higher. Three GAS emm types (emm49, emm60, and emm55) consistently occur in APSGN cases around the world. Future studies would therefore benefit from examining the genomic epidemiology of these emm types to unravel potential markers of APSGN.

Group A Streptococcus

Group A Streptococcus (GAS) or Streptococcus pyogenes, affects an estimated 800 million people each year. Most of the resulting estimated 639,000 annual deaths are related to rheumatic heart disease (RHD) and its complications. Resource-limited areas account for the vast majority of cases, although outbreaks still occur in industrialized countries. GAS has several mechanisms to avoid phagocytosis, including prevention of opsonization and the use of surface proteins to block complement fixation. The mechanisms behind the immunologic phenomenon are not well understood. Clinical presentations range from benign, short-lived impetigo or pharyngitis through to lifelong RHD. In its most invasive form, GAS can cause a rapidly progressive, often lethal infection: streptococcal toxic shock syndrome. S. pyogenes remains universally sensitive to penicillin, which is the mainstay of treatment.

Skin infections in Australian Aboriginal children: a narrative review

Impetigo, scabies, cellulitis and abscesses are common in Australian Aboriginal children. These conditions adversely affect wellbeing and are associated with serious long term sequelae, including invasive infection and post‐infectious complications, such as acute post‐streptococcal glomerulonephritis and acute rheumatic fever, which occurs at the highest documented rates in the world in remote Aboriginal communities.

Observational research in remote communities in northern Australia has demonstrated a high concurrent burden of scabies and impetigo and their post‐infectious complications.

Few data are available for other Australian states, especially for urban Aboriginal children; however, nationwide hospital data indicate that the disparity between Aboriginal and non‐Aboriginal children in skin infection prevalence also exists in urban settings.

The Australian National Healthy Skin Guideline summarises evidence‐based treatment of impetigo, scabies and fungal infections in high burden settings such as remote Aboriginal communities. It recommends systemic antibiotics for children with impetigo, and either topical permethrin or oral ivermectin (second line) for the individual and their contacts as equally efficacious treatments for scabies. β‐Lactams are the treatment of choice and trimethoprim–sulfamethoxazole and clindamycin are effective alternatives for treatment of paediatric cellulitis. Abscesses require incision and drainage and a 5‐day course of trimethoprim–sulfamethoxazole or clindamycin.

Addressing normalisation of skin infections and the social determinants of skin health are key challenges for the clinician. Research is underway on community‐wide skin health programs and the role for mass drug administration which will guide future management of these common, treatable diseases.

Acute Post-Streptococcal Glomerulonephritis in the Northern Territory of Australia: A Review of Data from 2009 to 2016 and Comparison with the Literature

Acute post-streptococcal glomerulonephritis (APSGN) is an inflammatory kidney disease following infection with nephritogenic strains of Group A Streptococcus. In 1991, APSGN became notifiable in the Northern Territory (NT) of Australia with cases recorded on the NT Notifiable Disease Database (NTNDS). The case definition of a confirmed case requires laboratory definitive evidence or laboratory suggestive evidence in conjunction with a clinically compatible illness. Probable cases require clinical evidence only. Acute post-streptococcal glomerulonephritis notifications from 2009 to 2016 were extracted from the NTNDS. Of the 322 cases, 261 were confirmed and 61 probable. The majority, 304 (94%), were Aboriginal and the median age was 8 years (range: 0–62 years). Incidence for confirmed cases was 13.8/100,000 person-years, with inclusion of probable cases increasing incidence to 17.0/100,000 person-years. Highest incidence of confirmed cases was in Aboriginal children less than 15 years of age at 124.0 cases/100,000 person-years. The rate ratio of confirmed cases in Aboriginal to non-Aboriginal Australians was 18.9 (95% confidence interval: 11.4–33.6). Recent trends show a consistently high number of notifications annually with less frequent outbreaks. The Aboriginal population of the NT continues to have high rates of APSGN with recent trends showing higher rates than previously reported. Sustained preventative efforts and continued surveillance strategies are needed.

An ion for an iron: streptococcal metal homeostasis under oxidative stress

The ability of opportunistic pathogens such as Group A Streptococcus (GAS) to transition between mucosal colonisation and invasive disease requires complex systems for adapting to markedly different host environments. The battle to acquire essential trace metals such as manganese and iron from the host is central to pathogenesis. Using a molecular genetic approach, Turner et al. [Biochem. J. (2019) 476, 595-611] show that it is not just individual metal concentrations that are important, but the ratio of iron to manganese within cells. Increasing this ratio by knocking out pmtA, encoding the Fe(II) exporter PmtA, or by disrupting mtsA, encoding an MtsABC Mn(II)-import system component, led to reductions in superoxide dismutase (SodA) activity and increased sensitivity to oxidative stress. The authors show that SodA is at least 4-fold more active with Mn bound than with Fe and speculate that high intracellular Fe:Mn ratios reduce superoxide dismutase activity through the mismetalation of SodA. Challenging wild-type GAS with 1 mM H₂O₂ led to a decrease in Fe:Mn ratio and a 3-fold increase in SodA activity, indicating that modulation of the balance between intracellular Fe and Mn may play an important role in adaptation to oxidative stress. This work unravels some of the key mechanisms for maintaining appropriate Mn and Fe concentrations within bacterial cells and underscores the need for future studies that take an holistic view to metal ion homeostasis in bacteria. Strategies aimed at interfering with the balance of intracellular metal ions represent a promising approach for the control of invasive microbial infections.

Factors associated with treatment outcome of acute post streptococcal glomerulonephritis among patients less than 18 years in Mekelle City, Public Hospitals, North Ethiopia

Objective

To assess factors associated treatment outcomes of acute post streptococcal glomerular nephritis among patients less than 18 years old in Mekelle City Public Hospitals.

Results

About 334 medical records c of children with acute post streptococcal glomerular nephritis were revised during the study period. Of these 244 (73.1%) had a positive outcome. acute post streptococcal glomerular nephritis was found to be statically significant associated with age < 5 years, duration of infection, the source of infection and length of stay in Hospital.

Acute rheumatic fever

Acute rheumatic fever is caused by an autoimmune response to throat infection with Streptococcus pyogenes. Cardiac involvement during acute rheumatic fever can result in rheumatic heart disease, which can cause heart failure and premature mortality. Poverty and household overcrowding are associated with an increased prevalence of acute rheumatic fever and rheumatic heart disease, both of which remain a public health problem in many low-income countries. Control efforts are hampered by the scarcity of accurate data on disease burden, and effective approaches to diagnosis, prevention, and treatment. The diagnosis of acute rheumatic fever is entirely clinical, without any laboratory gold standard, and no treatments have been shown to reduce progression to rheumatic heart disease. Prevention mainly relies on the prompt recognition and treatment of streptococcal pharyngitis, and avoidance of recurrent infection using long-term antibiotics. But evidence for the effectiveness of either approach is not strong. High-quality research is urgently needed to guide efforts to reduce acute rheumatic fever incidence and prevent progression to rheumatic heart disease.

Evaluation of safety and immunogenicity of a group A streptococcus vaccine candidate (MJ8VAX) in a randomized clinical trial

BACKGROUND

Group A streptococcus (GAS) is a serious human pathogen that affects people of different ages and socio-economic levels. Although vaccination is potentially one of the most effective methods to control GAS infection and its sequelae, few prototype vaccines have been investigated in humans. In this study, we report the safety and immunogenicity of a novel acetylated peptide-protein conjugate vaccine candidate MJ8VAX (J8-DT), when delivered intramuscularly to healthy adults.

METHODS

A randomized, double-blinded, controlled Phase I clinical trial was conducted in 10 healthy adult participants. Participants were randomized 4:1 to receive the vaccine candidate (N = 8) or placebo (N = 2). A single dose of the vaccine candidate (MJ8VAX), contained 50 μg of peptide conjugate (J8-DT) adsorbed onto aluminium hydroxide and re-suspended in PBS in a total volume of 0.5 mL. Safety of the vaccine candidate was assessed by monitoring local and systemic adverse reactions following intramuscular administration. The immunogenicity of the vaccine was assessed by measuring the levels of peptide (anti-J8) and toxoid carrier (anti-DT)-specific antibodies in serum samples.

RESULTS

No serious adverse events were reported over 12 months of study. A total of 13 adverse events (AEs) were recorded, two of which were assessed to be associated with the vaccine. Both were mild in severity. No local reactogenicity was recorded in any of the participants. MJ8VAX was shown to be immunogenic, with increase in vaccine-specific antibodies in the participants who received the vaccine. The maximum level of vaccine-specific antibodies was detected at 28 days post immunization. The level of these antibodies decreased with time during follow-up. Participants who received the vaccine also had a corresponding increase in anti-DT serum antibodies.

CONCLUSIONS

Intramuscular administration of MJ8VAX was demonstrated to be safe and immunogenic. The presence of DT in the vaccine formulation resulted in a boost in the level of anti-DT antibodies.

TRIAL REGISTRATION

ACTRN12613000030774.

Contribution of cryptic epitopes in designing a group A streptococcal vaccine

A successful vaccine needs to target multiple strains of an organism. Streptococcus pyogenes is an organism that utilizes antigenic strain variation as a successful defence mechanism to circumvent the host immune response. Despite numerous efforts, there is currently no vaccine available for this organism. Here we review and discuss the significant obstacles to vaccine development, with a focus on how cryptic epitopes may provide a strategy to circumvent the obstacles of antigenic variation.

Protective immunity induced by an intranasal multivalent vaccine comprising 10 Lactococcus lactis strains expressing highly prevalent M-protein antigens derived from Group A Streptococcus

Streptococcus pyogenes (group A Streptococcus) causes diseases ranging from mild pharyngitis to severe invasive infections. The N-terminal fragment of streptococcal M protein elicits protective antibodies and is an attractive vaccine target. However, this N- terminal fragment is hypervariable: there are more than 200 different M types. In this study, an intranasal live bacterial vaccine comprising 10 strains of Lactococcus lactis, each expressing one N-terminal fragment of M protein, has been developed. Live bacterial-vectored vaccines cost less to manufacture because the processes involved are less complex than those required for production of protein subunit vaccines. Moreover, intranasal administration does not require syringes or specialized personnel. Evaluation of individual vaccine types (M1, M2, M3, M4, M6, M9, M12, M22, M28 and M77) showed that most of them protected mice against challenge with virulent S. pyogenes. All 10 strains combined in a 10-valent vaccine (M×10) induced serum and bronchoalveolar lavage IgG titers that ranged from three- to 10-fold those of unimmunized mice. After intranasal challenge with M28 streptococci, survival of M×10-immunized mice was significantly higher than that of unimmunized mice. In contrast, when mice were challenged with M75 streptococci, survival of M×10-immunized mice did not differ significantly from that of unimmunized mice. Mx-10 immunized mice had significantly less S. pyogenes in oropharyngeal washes and developed less severe disease symptoms after challenge than did unimmunized mice. Our L. lactis-based vaccine may provide an alternative solution to development of broadly protective group A streptococcal vaccines.

The global burden of paediatric heart disease

An estimated 15 million children die or are crippled annually by treatable or preventable heart disease in low- and middle-income countries. Global efforts to reduce under-5 mortality have focused on reducing death from communicable diseases in low- and middle-income countries with little to no attention focusing on paediatric CHD and acquired heart disease. Lack of awareness of CHD and acquired heart disease, access to care, poor healthcare infrastructure, competing health priorities, and a critical shortage of specialists are important reasons why paediatric heart disease has not been addressed in low resourced settings. Non-governmental organisations have taken the lead to address these challenges. This review describes the global burden of paediatric heart disease and strategies to improve the quality of care for paediatric heart disease. These strategies would improve outcomes for children with heart disease.

Patterns of paediatric emergency presentations to a tertiary referral centre in the Northern Territory

OBJECTIVE

To describe epidemiological data concerning paediatric attendances at the ED of Royal Darwin Hospital (RDH).

METHODS

We conducted a retrospective cohort study of paediatric emergency presentations to the RDH ED during 2004 and 2013. Epidemiological data, including demographics, admission rates and diagnostic grouping, were analysed using descriptive and comparative statistical methods. We compared data with findings from a baseline epidemiological study by the Paediatric Research in Emergency Departments International Collaborative (PREDICT) conducted in 2004.

RESULTS

A total of 12 745 and 15 378 paediatric presentations (age 0-18 years) to the RDH ED were analysed for the years 2004 and 2013 respectively. In 2004, the mean age of children presenting to RDH was 7.1 years, and 56.0% were female. Indigenous patients accounted for 31.2% of presentations at RDH and were significantly more likely to be admitted than non-Indigenous patients (31.6% vs 12.8%, OR 3.24, 95% CI 2.95-3.55). Children <5 years old accounted for the highest number of presentations (45.2%) and admissions (51.2%), and there was a high proportion of adolescent presentations (18.0%). Similar to the PREDICT study, viral infectious conditions (bronchiolitis, gastroenteritis, upper respiratory tract infections) were the most common cause for presentations. Key differences included a higher proportion of patients presenting with cellulitis and head injury at RDH and an increasing proportion of adolescent psychiatric presentations at RDH from 2004 to 2013.

CONCLUSION

This study provides important information regarding paediatric presentations to a major referral hospital in the Northern Territory. Overall, there was a disproportionate rate of presentation and admission among Indigenous children. Other key findings were higher proportions of cellulitis, head injury and adolescent presentations. These findings can assist in service planning and in directing future research specific to children in the Northern Territory.

Rheumatic Heart Disease in the Twenty-First Century

Rheumatic heart disease (RHD) is a chronic valvular disease resulting after severe or repetitive episodes of acute rheumatic fever (ARF), an autoimmune response to group A Streptococcus infection. RHD has been almost eliminated with improved social and health infrastructure in affluent countries while it remains a neglected disease with major cause of morbidity and mortality in many low- and middle-income countries, and resource-limited regions of high-income countries. Despite our evolving understanding of the pathogenesis of RHD, there have not been any significant advances to prevent or halt progression of disease in recent history. Long-term penicillin-based treatment and surgery remain the backbone of a RHD control program in the absence of an effective vaccine. The advent of echocardiographic screening algorithms has improved the accuracy of diagnosing RHD and has shed light on the enormous burden of disease. Encouragingly, this has led to a rekindled commitment from researchers in the most affected countries to advocate and take bold actions to end this disease of social inequality.

Bivalent mucosal peptide vaccines administered using the LCP carrier system stimulate protective immune responses against Streptococcus pyogenes infection

Despite the broad knowledge about the pathogenicity of Streptococcus pyogenes there is still a controversy about the correlate of protection in GAS infections. We aimed in further improving the immune responses stimulated against GAS comparing different vaccine formulations including bis-(3',5')-cyclic dimeric adenosine monophosphate (c-di-AMP) and BPPCysMPEG, a derivative of the macrophage-activating lipopeptide (MALP-2), as adjuvants, respectively, to be administered with and without the universal T helper cell epitope P25 along with the optimized B cell epitope J14 of the M protein and B and T cell epitopes of SfbI. Lipopeptide based nano carrier systems (LCP) were used for efficient antigen delivery across the mucosal barrier. The stimulated immune responses were efficient in protecting mice against a respiratory challenge with a lethal dose of a heterologous S. pyogenes strain. Moreover, combination of the LCP based peptide vaccine with c-di-AMP allowed reduction of antigen dose at the same time maintaining vaccine efficacy.

Lutembacher syndrome variant: Rheumatic heart disease involving all four valves and associated with an atrial septal defect in a child

Rheumatic heart disease (RHD) is the most common cause of acquired heart disease in children and young adults in developing countries. It results from throat infection with group A beta hemolytic streptococcus that proceeds to acute rheumatic fever (ARF). We report a 13 years old girl from Darfur presenting with recurrent acute rheumatic fever for 4 years that led to affection of all her heart valves with severe mitral and tricuspid regurgitation together with moderate pulmonary and mild aortic valve regurgitation. There was an associated atrial septal defect (Lutembacher syndrome variant). The disease was severe and led to cardiogenic shock and death while awaiting surgery. The case highlights the impact of RHD on young people and the need to implement control programs for RHD in Sudan.

Children with post-rheumatic valvulopathies in natural history: five years follow-up in the cardiac centre, St. Elizabeth Catholic General hospital Shisong (Cameroon)

The aim of the study was to investigate the pattern of valvular lesions, the mortality and the challenges in five years follow-up in children with post-rheumatic valvulopathies in natural history in St. Elizabeth Catholic General hospital Shisong, cardiac centre. This retrospective analysis included 270 patients aged between 5 and 16 years old suffering from post-rheumatic valvulopathies who consulted in the cardiac centre from July 2008 through July 2013. Postrheumatic valvulopathies were diagnosed according to the World heart federation criteria. Data from patients' records, two-dimensional echocardiographic studies, and electrocardiograms were reviewed. Patients and their family were contacted every six months. The duration of the follow-up was 60months. Patients aged between 5 and 16 years old with a mean age of 12.4±4.5 years. Female gender was representing 63% (n=170) of the population. Surgery was indicated in 256 cases. Lesions of the valves needing prophylaxis with penicillin was diagnosed in 14 cases. In 95 patients surgical correction could not be performed. Mitral regurgitation was the commonest echocardiographic diagnosis present in 61.5%, n=164 patients; 38.5%, n=103 patients had aortic regurgitation. Mitral stenosis and mitral disease were also represented in 6%, n=16, and 8%, n= 21 patients respectively. Pulmonary hypertension was the common echocardiographic complication of the disease in=234, 87% of cases. Clinically, complications of the disease included congestive heart failure (n=229, 85%), growth retardation (n=162, 60%), sudden death (n=27, 10%). On presentation, n=210, 78% of cases were admitted. Mortality in two years was 35%, (p≤0.05, 95% CI=2.5-6.5), in five years was 65% (p≤ 0.05, 93% CI= 2.7-7.21). The challenges faced are patients' negligence and poor discipline, wrong beliefs, poverty. Post-rheumatic mitral valve regurgitation is the pathology the most encountered. Pulmonary hypertension is the most common echocardiographic complication of the disease. Five years mortality is very high in our setting. Due to financial limitation and illiteracy of parents, the follow up of patients is difficult.

Global Perspectives On Pediatric Cardiac Critical Care

OBJECTIVES

The objectives of this review are to discuss the global epidemiology of cardiovascular disease, emphasizing congenital heart disease; to discuss the concept of epidemiologic transition and its role in studying the evolving epidemiology of disease; and to assess and address the global burden of congenital heart disease including its prevention and treatment.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSIONS

Despite impressive reductions in mortality from congenital and acquired cardiovascular disease in high-income countries, these reductions have not been observed on a global scale. It will be necessary to continue our attempts to extend rational programs of care to middle- and low-income countries based on community empowerment, economics, and population health. The specialist in pediatric cardiac critical care can be a central driver of these programs.

Prevalence of rheumatic heart disease among school children in Ethiopia: A multisite echocardiography-based screening

BACKGROUND

Auscultation-based surveys in Ethiopia conducted in the late 1990's reported a rural prevalence of 4.6/1000 and an urban prevalence of 6.4/1000 of rheumatic heart disease (RHD). With echo-based screening, we aimed to estimate the national prevalence of RHD in school children by taking school-based samples from six regions across the country using the 2012 World Heart Federation echocardiographic criteria.

PATIENTS AND METHODS

We conducted a cross-sectional echocardiographic screening of RHD in school children aged 6-18years from 28 randomly selected primary and secondary schools found in six different geographic regions of Ethiopia. We used the standardized WHF echocardiographic criteria.

RESULTS

A total of 3238 children (48.5% females) were screened. The mean age was 13.2±3.2years. Of these, 44 patients (1.4%) met the WHF criteria for definite RHD, while 15 (0.5%) met the criteria for borderline disease, yielding a prevalence of 19 [13.9-23.4, 95% CI] cases per 1000 school children between the ages of 6-18years. The majority of those who tested positive were girls (26/44). The prevalence was lowest in children aged 6-9years and otherwise uniformly distributed across ages 10-18years. Definite RHD involved the mitral valve in 42 subjects, 39 of whom had mitral regurgitation and 3 with mitral stenosis. The aortic valve was affected in 6 children. The ratio of definite to borderline cases was 2.9.

CONCLUSION

This study demonstrated a consistent pattern of high prevalence of asymptomatic RHD with definite disease predominating over borderline involvement across six regions of Ethiopia.

Feasibility study of first-year medical students identifying cardiac anatomy using ultrasound in rural Panama

BACKGROUND

There are over 15 million children who have cardiac anomalies around the world, resulting in a significant morbidity and mortality. Early recognition and treatment can improve the outcomes and lengthen life-expectancy of these patients. The NIH and WHO have promoted guidelines for screening for congenital cardiac anomalies using ultrasound in rural environments.

METHODS

Our study took place in Bocas Del Toro, Panama where a mobile clinic was established for community healthcare screening and ultrasonographic evaluation by medical student volunteers and volunteer clinical faculty. This was a non-blinded, investigational study utilizing a convenience sample of pediatric patients presenting for voluntary evaluation. Seven first-year medical students were recruited for the study. These students underwent a training program for advanced cardiac ultrasound instruction, termed "Pediatric Echocardiography Cardiac Screening (PECS)".

RESULTS

Ten patients were enrolled in the study. Nine patients had adequate images as defined by the PECS criteria and were all classified as normal cardiac pathology by the medical students, resulting in a sensitivity and specificity of 100%. A single patient was identified by medical students as having a pathologic pulmonic stenosis. This was confirmed as correct by a blinded ultrasonographer.

CONCLUSIONS

In this pilot study, the first-year medical students were able to correctly identify pediatric cardiac anatomy and pathology in rural Panama after undergoing a 12-hour ultrasound PECS training session. We believe that with this knowledge, minimally trained practitioners can be used to screen for cardiac anomalies in rural Panama using ultrasound.

Rheumatic Heart Disease-Attributable Mortality at Ages 5-69 Years in Fiji: A Five-Year, National, Population-Based Record-Linkage Cohort Study

Background

Rheumatic heart disease (RHD) is considered a major public health problem in developing countries, although scarce data are available to substantiate this. Here we quantify mortality from RHD in Fiji during 2008–2012 in people aged 5–69 years.

Methods and Findings

Using 1,773,999 records derived from multiple sources of routine clinical and administrative data, we used probabilistic record-linkage to define a cohort of 2,619 persons diagnosed with RHD, observed for all-cause mortality over 11,538 person-years. Using relative survival methods, we estimated there were 378 RHD-attributable deaths, almost half of which occurred before age 40 years. Using census data as the denominator, we calculated there were 9.9 deaths (95% CI 9.8–10.0) and 331 years of life-lost (YLL, 95% CI 330.4–331.5) due to RHD per 100,000 person-years, standardised to the portion of the WHO World Standard Population aged 0–69 years. Valuing life using Fiji’s per-capita gross domestic product, we estimated these deaths cost United States Dollar $6,077,431 annually. Compared to vital registration data for 2011–2012, we calculated there were 1.6-times more RHD-attributable deaths than the number reported, and found our estimate of RHD mortality exceeded all but the five leading reported causes of premature death, based on collapsed underlying cause-of-death diagnoses.

Conclusions

Rheumatic heart disease is a leading cause of premature death as well as an important economic burden in this setting. Age-standardised death rates are more than twice those reported in current global estimates. Linkage of routine data provides an efficient tool to better define the epidemiology of neglected diseases.

Rheumatic heart disease is the result of an abnormal immune response to the bacteria Streptococcus pyogenes. The disease causes permanent scarring of the heart values, which results in heart failure, stroke and early death. It primarily affects the world’s poorest and most disadvantaged populations and despite the availability of cheap and effective prevention strategies receives little attention from policy-makers and funders. One of the major difficulties has been measuring how many people die prematurely from this disease. Simply counting up deaths is highly inaccurate and so an alternate strategy was needed. Focusing on Fiji in the Western Pacific, we pulled together information from several different health databases using a process called record-linkage. We then worked out how much more frequently rheumatic heart disease patients die than you might expect when comparing them to persons of similar age, gender and ethnicity in the general population. From these data we estimate about twice as many patients were dying from the disease than had been previously suggested. Most of these deaths occurred earlier than was thought with substantial knock-on effects for the economy. On balance we think this strategy for measuring mortality is useful and robust, and it will be increasingly possible to employ it elsewhere.

The Global Epidemiology of Impetigo: A Systematic Review of the Population Prevalence of Impetigo and Pyoderma

Objective

We conducted a comprehensive, systematic review of the global childhood population prevalence of impetigo and the broader condition pyoderma.

Methods

PubMed was systematically searched for impetigo or pyoderma studies published between January 1 1970 and September 30 2014. Two independent reviewers extracted data from each relevant article on the prevalence of impetigo.

Findings

Sixty-six articles relating to 89 studies met our inclusion criteria. Based on population surveillance, 82 studies included data on 145,028 children assessed for pyoderma or impetigo. Median childhood prevalence was 12·3% (IQR 4·2–19·4%). Fifty-eight (65%) studies were from low or low-middle income countries, where median childhood prevalences were 8·4% (IQR 4·2–16·1%) and 14·5% (IQR 8·3–20·9%), respectively. However, the highest burden was seen in underprivileged children from marginalised communities of high-income countries; median prevalence 19·4%, (IQR 3·9–43·3%).

Conclusion

Based on data from studies published since 2000 from low and low-middle income countries, we estimate the global population of children suffering from impetigo at any one time to be in excess of 162 million, predominantly in tropical, resource-poor contexts. Impetigo is an under-recognised disease and in conjunction with scabies, comprises a major childhood dermatological condition with potential lifelong consequences if untreated.

Rheumatic heart disease among adults in a mining community of Papua, Indonesia: findings from an occupational cohort

Background

Rheumatic heart disease (RHD) remains a significant cause of cardiovascular morbidity and mortality in developing countries such as Indonesia. Yet, despite being one of the most readily preventable chronic diseases, RHD has received scant research or policy attention, particularly in South-East Asia.

Aim

To describe the pattern of RHD occurrence in a sample of presenting cases from an occupational cohort in Papua Province, Indonesia.

Methods

Clinical records of 15 608 mining workers (96.4% men, mean age 36.3±7.4 years) were reviewed retrospectively to identify and extract data on all rheumatic fever (RF) and RHD cases admitted to two hospitals in Papua during 2008–2013. Collected data included basic demographics, employment history and echocardiographic findings.

Results

83 RHD cases (95.6% men, mean age 39.6±12.5 years) and 3 RF cases were identified between 2008 and 2013. Increased RHD risk was observed among those aged 35–44 (HR=3.60) and 45–68 (HR=4.46) years relative to the youngest age group (p<0.01). RHD incidence density was 6.84 per 10 000 person years of follow-up. Among cases, mitral stenosis was the most common valvular lesion at initial presentation (41.0%), and 6.0% were multivalvular.

Conclusions

The prevalence of RHD in Papuan mining workers correlates with adult prevalence data in other populations with a high RHD burden, highlighting RHD as a significant health issue into adulthood. The late stage at which most patients presented points to a strong need for earlier intervention. Both primary and secondary preventive measures must be considered critical tools to prevent and reduce RHD burden, particularly among older age groups.

[Outcome of rapidly progressive glomerulonephritis post-streptococcal disease in children]

BACKGROUND

Rapidly progressive glomerulonephritis is a rare form of postinfectious glomerulonephritis. The aim of this study was to describe the outcome of our patients with severe post-streptococcal glomerulonephritis.

METHODS

This retrospective study was conducted in the department of pediatrics in Charles-Nicolle Hospital during a period of 13 years (1997-2009).

RESULTS

Twenty-seven children were identified. The mean age was 8.7 years. All patients presented renal failure at presentation. The mean serum creatinine at presentation was 376.9 μmol/L. Six patients presented nephrotic syndrome. Twenty-six children had renal biopsies. Renal biopsies showed crescents in 24 cases. Eighteen children received pulse dose of corticosteroids (66.6%) and 6 children (22%) received pulse dose of corticosteroids and cyclophosphamide. Eleven patients required dialysis. At last follow-up, 22 patients (81.5%) had normal kidney function, 2 had renal dysfunction and 3 reached end stage renal disease. The only significant determinant for renal survival was the supportive dialysis (P=0.015).

CONCLUSION

Rapidly progressive glomerulonephritis is uncommon. There have been significant advancements in supportive, as well as specific therapy, but the outcome continues to be poor.

Application of the C3-binding motif of streptococcal pyrogenic exotoxin B to protect mice from invasive group a streptococcal infection

Group A streptococcus (GAS) is an important human pathogen that produces several extracellular exotoxins to facilitate invasion and infection. Streptococcal pyrogenic exotoxin B (SPE B) has been demonstrated to be an important virulence factor of GAS. Our previous studies indicate that SPE B cleaves complement 3 (C3) and inhibits the activation of complement pathways. In this study, we constructed and expressed recombinant fragments of SPE B to examine the C3-binding site of SPE B. Using enzyme-linked immunosorbent assays and pull-down assays, we found that the C-terminal domain, containing amino-acid residues 345–398, of SPE B was the major binding site of human serum C3. We further identified a major, Ala³⁷⁶-Pro³⁹⁸, and a minor C3-binding motif, Gly³⁴⁶-Gly³⁶⁰, that both mediated the binding of C3 complement. Immunization with the C3-binding motifs protected mice against challenge with a lethal dose of non-invasive M49 strain GAS but not invasive M1 strains. To achieve higher efficiency against invasive M1 GAS infection, a combination of synthetic peptides derived from C-terminal epitope of streptolysin S (SLSpp) and from the major C3-binding motif of SPE B (PP6, Ala³⁷⁶-Pro³⁹⁸) was used to elicit specific immune response to those two important streptococcal exotoxins. Death rates and the severity of skin lesions decreased significantly in PP6/SLSpp-immunized mice that were infected with invasive M1 strains of GAS. These results indicate a combination of the C3-binding motif of SPE B and the protective epitope of SLS could be used as a subunit vaccine against invasive M1 strains group A streptococcal infection.

Role of viruses and bacteria-virus interactions in autoimmunity

A potential role for viral and bacterial-viral interactions in the pathogenesis of autoimmune disease has been long recognized. Recently, intensive investigation has begun to decipher interactions between specific microbes with the host that contribute toward autoimmunity. This work has primarily focused on known viral and bacterial pathogens. A major challenge is to determine the role of bacteria that are typically considered as commensals as well as chronic viruses. Furthermore, equally challenging is to prove causality given the potential complexity of microbe-microbe interactions. Important initial contributions to this field have shown that specific interactions of microbes with hosts that contain a background of genetic susceptibility can play a role in autoimmune pathogenesis. In this review, we describe principles of immune tolerance with a focus on its breakdown during pathogenic as well as commensal relationships between the host and the microbial world.

Evaluation and management of atrioventricular block in children

PURPOSE OF REVIEW

Pediatric brady-dysrhythmias and conduction disorders are uncommon, but timely recognition and evaluation are critical. This review will highlight the key diagnostic and management steps for first, second, and third-degree atrioventricular heart block in pediatric patients.

RECENT FINDINGS

There is a breadth of acquired and often reversible causes of atrioventricular block in childhood. Recent advances in diagnostics and pacing therapies have led to improved outcomes.

SUMMARY

A thorough evaluation is required to determine when atrioventricular block requires treatment. In symptomatic or unstable patients, the management should focus on resuscitative measures, diagnostic testing, potential reversible causes, monitoring for progression, cardiac consultation and evaluating the need for definitive pacemaker placement.

Current practice about the evaluation of antibody to streptolysin O (ASO) levels by physicians working in Antananarivo, Madagascar

INTRODUCTION

The diagnosis of post streptococcal diseases is usually confirmed by immunological tests. Only the antistreptolysin O is usually prescribed by physician. This study aimed to describe the current practice of these requests in Antananarivo.

METHODS

It was a retrospective and descriptive study conducted at the Para clinic Unit of Immunology at the University Center Hospital of Antananarivo. We analyzed all requests during seven years, from January 2003 to December 2009. We looked at age, gender, and clinical symptoms which led to the request and the result for each request.

RESULTS

We retained 4143 requests for antistreptolysin O titration in our study. The mean age of the study participants was 32.9 years with 18.3% of participants being less than 15 years old. The main symptoms leading to the request of this analysis were rheumatologic (41%), followed by neurological (13.9%) and cardiologic symptoms (8.5%) and 19.4% were prescribed for various symptoms. Only 15% of all requests had a value more than 200 U/ml.

CONCLUSION

Our study found that in most of requests, ASO titre levels were not significant.

An extracellular bacterial pathogen modulates host metabolism to regulate its own sensing and proliferation

Successful infection depends on the ability of the pathogen to gain nutrients from the host. The extracellular pathogenic bacterium group A Streptococcus (GAS) causes a vast array of human diseases. By using the quorum-sensing sil system as a reporter, we found that, during adherence to host cells, GAS delivers streptolysin toxins, creating endoplasmic reticulum stress. This, in turn, increases asparagine (ASN) synthetase expression and the production of ASN. The released ASN is sensed by the bacteria, altering the expression of ∼17% of GAS genes of which about one-third are dependent on the two-component system TrxSR. The expression of the streptolysin toxins is strongly upregulated, whereas genes linked to proliferation are downregulated in ASN absence. Asparaginase, a widely used chemotherapeutic agent, arrests GAS growth in human blood and blocks GAS proliferation in a mouse model of human bacteremia. These results delineate a pathogenic pathway and propose a therapeutic strategy against GAS infections.

Group A streptococcal emm type prevalence among symptomatic children in Cape Town and potential vaccine coverage

The molecular epidemiology of group A streptococcal pharyngeal infections in children in the Vanguard Community of Cape Town revealed 26 emm types among 157 isolates from 742 subjects. Coverage of a 30-valent vaccine is predicted to be 95% of pharyngitis cases in this population at high risk of rheumatic fever.

Congenital heart disease and rheumatic heart disease in Africa: recent advances and current priorities

Africa has one of the highest prevalence of heart diseases in children and young adults, including congenital heart disease (CHD) and rheumatic heart disease (RHD). We present here an extensive review of recent data from the African continent highlighting key studies and information regarding progress in CHD and RHD since 2005. Main findings include evidence that the CHD burden is underestimated mainly due to the poor outcome of African children with CHD. The interest in primary prevention for RHD has been recently re-emphasised, and new data are available regarding echocardiographic screening for subclinical RHD and initiation of secondary prevention. There is an urgent need for comprehensive service frameworks to improve access and level of care and services for patients, educational programmes to reinforce the importance of prevention and early diagnosis and a relevant research agenda focusing on the African context.

Determining antibody-binding site of streptococcal pyrogenic exotoxin B to protect mice from group a streptococcus infection

Streptococcal pyrogenic exotoxin B (SPE B), a cysteine protease, is an important virulence factor in group A streptococcal (GAS) infection. SPE B binds and cleaves antibody isotypes and further impairs the immune system by inhibiting complement activation. In this study, we examined the antibody-binding site of SPE B and used it to block SPE B actions during GAS infection. We constructed different segments of the spe B gene and induced them to express different recombinant fragments of SPE B. Using an enzyme-linked immunosorbent assay (ELISA), we found that residues 345–398 of the C-terminal domain of SPE B (rSPE B_345–398), but not the N-terminal domain, was the major binding site for antibody isotypes. Using a competitive ELISA, we also found that rSPE B_345–398 bound to the Fc portion of IgG. The in vitro functional assays indicate that rSPE B_345–398 not only interfered with cleavage of antibody isotypes but also interfered with SPE B-induced inhibition of complement activation. Immunization of BALB/c mice using rSPE B_345–398 was able to induce production of a high titer of anti-rSPE B_345–398 antibodies and efficiently protected mice from GAS-induced death. These findings suggest that SPE B uses its C-terminal domain to bind the Fc portion of IgG and that immunization of mice with this binding domain (rSPE B_345–398) could protect mice from GAS infection.