The bacterium streptococcus pneumoniae (S. pneumoniae) is the most common cause of pneumonia, and is responsible for over one million avoidable deaths worldwide each year. S. pneumoniae also frequently causes milder lung infections, resulting in exacerbations of common lung conditions like chronic obstructive pulmonary disease. Vaccines exist but are either very expensive and only protect against a limited number of the wide range of different S. pneumoniae strains that cause disease, or are not effective at preventing lung disease in children or older people – the groups that are at the most risk of lung infections. New, more effective vaccines are desperately needed to protect people from developing lung diseases caused by S. pneumoniae.
Most existing S. pneumoniae vaccines are based on sugars found in the bacteria. During this BLF project grant, Dr Brown and his team attempted to develop and test new vaccines based on proteins found in the bacteria. As these proteins exist in all strains of the bacteria, they hoped that these vaccines would be effective against most S. pneumoniae infections.
The team tested several different types of protein and although several effects on the immune system were noted, protection against infection in the lung was very limited. However, the team also tested a live form of the bacteria which was altered to make it unable to cause infection. Excitingly, they found that this live version can protect against pneumonia.
This work has highlighted the difficulty in using proteins as vaccines against S. pneumoniae infections, but has shown that using modified live bacteria can be effective. Further work is now needed to explore how this modified live bacteria might be converted into a reliable vaccine for worldwide use.
Dr Brown is Reader in Respiratory Infection and Honorary Consultant at University College London.
His work focuses on the biochemistry of lung infection, particularly in pneumonia, with the aim of producing new ways to prevent or treat infection.
