Can class I epitope of M protein be a diagnostic marker for rheumatic fever in populations endemic for group A streptococci?

The pattern of acute rheumatic fever in children: Experience at the children's hospital, Riyadh, Saudi Arabia

BACKGROUND

The study was carried out in Riyadh City Hospital to determine the hospital prevalence of acute rheumatic fever (ARF), its characteristics and to determine the proportion of the ARF population that have recurrent attacks.

METHODS

The study was an analysis of 83 children with ARF, admitted to the Children's Hospital, Riyadh, over a 10-year period (1994-2003). The diagnosis of ARF was based on clinical features as defined in the modified Jones criteria with evidence of recent streptococcal infection. The diagnosis of recurrence of rheumatic fever in children with rheumatic heart disease was based on the presence of one major criterion apart from carditis or two minor criteria, in addition to evidence of preceding streptococcal infection.

RESULTS

The mean age at presentation was 9 years. In 31 (37%) cases, arthritis was the only major Jones criterion. In 30 (36%) others, arthritis was associated with carditis and in 3 (4%), with chorea. Cardiac involvement was documented in 44 (53%) cases; it occurred alone in 5 (6%), with arthritis in 30 (36%), and with chorea in 9 (11%) others. Among the 44 with carditis, the pattern of cardiac involvement was valvular only (mild carditis) in 30 (68%), while it was severe in the remaining 14 (32%) cases who also had heart failure. The involvement of the mitral valve alone occurred in 26 (59%) cases in the form mitral regurgitation, while both aortic and mitral valve regurgitation were present in 11 (25%) cases, and aortic valve regurgitation alone in four (9%) others. Chorea was the only major criterion of ARF in 5 children (6%), while it occurred in association with other major criteria in 12 (15%) others. Nineteen (23%) children had recurrent attacks of ARF.

CONCLUSION

ARF continues to occur in Saudi Arabia in the period (1994-2003), despite the progress made in the socio-economic development of the country, and this is often associated with severe cardiac involvement.

Acute rheumatic fever

Acute rheumatic fever (ARF) and its chronic sequela, rheumatic heart disease (RHD), have become rare in most affluent populations, but remain unchecked in developing countries and in some poor, mainly indigenous populations in wealthy countries. More than a century of research, mainly in North America and Europe, has improved our understanding of ARF and RHD. However, whether traditional views need to be updated in view of the epidemiological shift of the past 50 years is still to be established, and improved data from developing countries are needed. Doctors who work in populations with a high incidence of ARF are adapting existing diagnostic guidelines to increase their sensitivity. Group A streptococcal vaccines are still years away from being available and, even if the obstacles of serotype coverage and safety can be overcome, their cost could make them inaccessible to the populations that need them most. New approaches to primary prevention are needed given the limitations of primary prophylaxis as a population-based strategy. The most effective approach for control of ARF and RHD is secondary prophylaxis, which is best delivered as part of a coordinated control programme.

Epidemiological aspects of antibiotic resistance in respiratory pathogens

Respiratory infections are the most frequent reason for primary health care consultation. The main causes of respiratory tract infections in children are viruses and the most common types are upper respiratory tract infections: common cold, pharyngitis, otitis media and sinusitis. Pneumonia is much more serious. As well as viruses, bacteria are often involved in respiratory tract infections. Three bacterial species are most commonly isolated: Streptococcus pneumoniae, non-encapsulated Haemophilus influenzae and Moraxella (Branhamella) catarrhalis. The most common bacterial cause of pharyngitis is Streptococcus pyogenes. Bacteria isolated from community-acquired infection usually are sensitive to the majority of suitable drugs, but during the past two decades, significant antibiotic resistance has emerged. Resistance to penicillins has spread among H. influenzae and S. pneumoniae. The mechanism of penicillin resistance in H. influenzae is mainly by production of beta-lactamases TEM-1 and ROB-1, whereas in S. pneumoniae resistance is an effect of the changes in penicillin binding proteins. Among respiratory pathogens, resistance to tetracyclines, macrolides, trimethoprim-sulphamethoxazole and fluoroquinolones has also appeared. Several mechanisms depending on changes in target, active efflux and modifying enzymes are involved.

Antibody levels to the class I and II epitopes of the M protein and myosin are related to group A streptococcal exposure in endemic populations

Rheumatic fever (RF)/rheumatic heart disease (RHD) and post-streptococcal glomerulonephritis are thought to be autoimmune diseases, and follow group A streptococcal (GAS) infection. Different GAS M types have been associated with rheumatogenicity or nephritogenicity and categorized into either of two distinct classes (I or II) based on amino acid sequences present within the repeat region ('C' repeats) of the M protein. Sera from ARF patients have previously been shown to contain elevated levels of antibodies to the class I-specific epitope and myosin with the class I-specific antibodies also being cross-reactive to myosin, suggesting a disease association. This study shows that immunoreactivity of the class I-specific peptide and myosin does not differ between controls and acute RF (ARF)/RHD in populations that are highly endemic for GAS, raising the possibility that the association is related to GAS exposure, not the presence of ARF/RHD. Peptide inhibition studies suggest that the class I epitope may be conformational and residue 10 of the peptide is critical for antibody binding. We demonstrate that correlation of antibody levels between the class I and II epitope is due to class II-specific antibodies recognizing a common epitope with class I which is contained within the sequence RDL-ASRE. Our results suggest that antibody prevalence to class I and II epitopes and myosin is associated with GAS exposure, and that antibodies to these epitopes are not an indicator of disease nor a pathogenic factor in endemic populations.

Rheumatic fever

Rheumatic fever is a multisystem inflammatory disease that occurs as a delayed sequel to group A streptococcal pharyngitis. It is less common than it was 50 years ago but is still a major cause of heart disease in developing areas of the world. The relationship between the site of infection, the type of causative organism, and susceptibility of the host is essential in the development of the disease. Its major clinical manifestations include carditis, migratory polyarthritis, chorea, erythema marginatum, and subcutaneous nodules. It can manifest as an acute febrile illness consisting of migratory polyarthritis involving the large joints, as carditis and valvulitis, or as Sydenham's chorea with involvement of the central nervous system. The disorder in its milder form resolves itself without sequelae. Carditis is the condition most associated with increased mortality and morbidity and may be fatal in its severe forms. Penicillin is the most appropriate primary and secondary prophylaxis. Anti- inflammatory agents provide symptomatic relief but do not prevent rheumatic heart disease.