The Queensland Institute of Medical Research (QIMR) is working on a vaccine to prevent rheumatic fever (RF) and rheumatic heart disease (RHD). Rheumatic fever and rheumatic heart disease are a secondary complication of a bacterial infection. The bacteria, group A streptococcus (GAS) affects people of all ages and socio-economic backgrounds and is responsible for strep throat and tonsillitis. The more serious RF and RHD are more prevalent in developing countries where over-crowding and poor access to health care are contributing factors.
Around 12 million people are affected by RF and RHD worldwide with 500,000 deaths occurring each year. Australia’s Aboriginal population experiences the highest rate of the disease in the world, with the incidence of RF being as high as 651 per 100,000 per year, and RHD being as high as 30 per 1,000. The average age of onset of RF in Aboriginal children is 11 years and the mean life expectancy of Aborigines with RHD is 33 years. In developing countries RHD is a very common cause for admission to hospital relative to other cardiac conditions. In India, for example, up to 50% of all cardiac admissions are for RHD, with similar statistics reported in many other developing countries.
Since both RF and RHD follow an infection with GAS, a practical strategy to prevent the disease is to prevent streptococcal infection. This is what QIMR aims to do through the development of an effective vaccine. QIMR’s Dr Colleen Olive is heading a research team working on a vaccine that uses small protein fragments of the bacteria to promote an immune response against GAS. One of the key components of the vaccine is a peptide fragment taken from a part of the bacteria called M protein. One of the major challenges associated with this is that there are currently more than 100 different GAS strains and therefore more than 100 different M proteins. However, Dr Olive’s group has shown that a small part of the M protein, called J8, is virtually identical amongst all GAS strains and can be used to target protective antibodies. In preliminary experiments this common region was used to immunise mice and these mice have been able to generate protective antibodies against multiple GAS strains. A new technology used in making the vaccine involves coating the protein with lipid (fat) components to improve the immune response to the vaccine.
This vaccine will potentially replace antibiotic therapy for controlling GAS infection.