Developing a Vaccine for Rheumatic Fever and Rheumatic Heart Disease: A Review of Current Research Strategies and Challenges

Rheumatic heart disease (RHD) is an auto immune sequelae of rheumatic fever (RF) caused by Group A Streptococcal (GAS) pharyngitis, rather than the direct bacterial infection of the heart, which leads to chronic heart valve damage. Although antibiotics like penicillin are effective against GAS infection, improper medical care such as poor patient compliance, overcrowding, poverty, and repeated exposure to GAS, leads to acute rheumatic fever and RHD. Thus, effort to design a vaccine based on emm gene identification of GAS, M-protein going on for more than 40 years, is unlikely to succeed. M-protein is strain specific. Infection with one strain does not provide immunity from infection with another strain. Based on the emm gene identification, of 250 or more identified strains of GAS, the distribution is heterogenous and keeps changing. The M-protein gene sequence of the organism tends to mutate. A vaccine prepared from available strains may not be effective against a strain following mutation.

Epidemiology of group a streptococcal pharyngitis & impetigo: A cross-sectional & follow up study in a rural community of northern India.

Background & objectives: Group A streptococcus (GAS) causes a wide array of human diseases. Epidemiological picture of streptococcal infection in India is not complete. Hence, disease burden due to GAS in 5-15 yr old school children in northern India was studied and emm typing of GAS isolates was carried out to help in designing prevention strategies. Methods: A cross-sectional survey was carried out among 4249 school children (5-15 yr) from Raipur Rani Block of Panchkula district in Haryana during 2000-2002; 334 children were followed up fortnightly for one year. Standard clinical and microbiological procedures were used for collection of swabs from throat and skin and confirmation of GAS and its emm types. Results: Of the 4249 children studied, 658 (15.5%) had pharyngitis; 579 of them could be swabbed, of which 2.8 per cent had GAS. From 3591 children without pharyngitis, 3385 who could be swabbed, GAS was found in 1.3 per cent of them. Impetigo was rare (0.7%), but 7.1 per cent (2/28) children had GAS. In the followup study, 17.4 per cent (776/4447 child-contacts) had pharyngitis, 761 could be swabbed and 2.4 per cent had GAS; among those without pharyngitis, 2016 swabs could be taken and GAS was found in 1.3 per cent; whereas only 2.6 per cent (2/75) of skin sores had GAS. Three children had GAS pharyngitis twice during follow up. Fourteen different GAS emm types were found. emm 71, 77 and 81 constituted 69 per cent of the pharyngeal isolates. GAS pharyngitis and impetigo were more common in winters and summers respectively. Interpretation & conclusions: In north India, pharyngitis was more common than impetigo. Most prevalent emm types of GAS in this region differ from those included in M protein-based vaccines.

Construction of eukaryotic expression plasmid encoding Fba protein of group A streptococcus and elicitation of immune responses by it / 中国免疫学杂志

Objective:To construct eukaryotic expression plasmid ecording a novel surface protein Fba of GAS, and to explore its impact on host immune responses.Methods:Fba gene was amplified by PCR using strain SSI-9 (GAS M1 serotype isolates) as the template, then cloned into pcDNA3.1 for constructing eukaryotic expression plasmid pcDNA3.1/fba and sequenced. Female CD1 mice were randomly individed into 6 groups, and immunized respectively with Fba protein, M protein, pcDNA3.1/fba + Fba protein, pcDNA3.1/fba, pcDNA3.1 and PBS as control. Blood was obtained from the mice and specific antibody of IgG was detected by ELISA. Spleen cells were assessed with lymphocyte proliferation assays.CD4+T cell and CD8+T cell were detected by flow cytometry (FCM). Assay results were analyzed with SPSS10.0.Results:The IgG against Fba protein kept hightest levels in group immunized with Fba protein. The levels of lymphocyte proliferation, CD4+, CD8+T cell were significantly high in the group pcDNA3.1/fba. Conclusion:(1) Just as M protein, the antibody to Fba protein could be efficiently induced by immunization with Fba protein, which showed that Fba protein was hopefully to be a candidate protein for vaccine against GAS.(2) Eukaryotic expression plasmid pcDNA3.1/fba was successfully constructed and this recombinant plasmid could efficiently induce antibody and CD4+ T cell for againsting GAS.