DIFFERENCES in immune responses to bacterial infections between individuals may be due to the specific bacterial strain, according to research from The Rockefeller University, New York City, New York, USA. Although variation in patient immune response is not a new concept, it is one that has puzzled researchers for some time. For example, <10% of Mycobacterium tuberculosis infections result in patients developing severe lung disease, while the majority of patients remain asymptomatic.
Previously, discoveries of genetic variations within the human genome have helped to explain the differences in human host immune responses. Although still relevant, this new research highlights that the human genome is not the only factor that can contribute to these major differences. In addition, components of the bacterial genome itself may be responsible.
The researchers analysed blood samples taken from healthy adult volunteers and exposed them to different strains of Staphylococcus aureus and Streptococcus pyogenes. They looked at the varying immune reactions when exposed to the ‘core’ genome of the bacteria (present in all strains of a species), and then when the prophages of the ‘accessory’ genome (genes unique to different isolates) were removed. When removing the prophages, the genetic component of a bacteriophage, the researchers found that the host immune responses differed significantly, with variations in both T and B cell reactions.
Uri Sela, The Rockefeller University, said: “Our findings are novel and unexpected, and may set the stage for better ways to predict a patient’s disease outcome and tailor treatment accordingly.” Previous studies have only included single bacterial strains in this type of experiment, and so these results provide a better representation of the entire species and could be applied to enhance future medical practice and treatment regimes. The researchers note that the effect the bacterial accessory genome has on the outcome of an infected patient is not yet known, leaving opportunity for further study in this novel area of research.