Bacterial surface proteins play a fundamental role in the interaction between cell and its environment. They constitute a diverse group of molecules with important functions. Moreover, they are potential drug targets, and targets for vaccines, as they are molecules with the highest probability to be recognized by the elements of the immune system.
The aim of this project is the identification in a fast and highly reliable manner of a set of protein vaccine candidates against two Gram-positive bacteria: i) Streptococcus pneumoniae, a Gram-positive bacterium which is pathogen in humans, being the leading cause of infective pneumonia in children and adollescents. Pneumococcal infections have increased in frequency and severity in the last decade in the developed countries, and they are a major problem in developing countries. This resurgence has heightened public concern, largely because no highly effective vaccine is available, resistance to certain antibiotics has recently emerged, and pneumococcal infections can cause high morbidity and mortality. ii) S. suis, which infects pigs causing various pathologies, which, in addition to causing economic losses, are also a public health problem for humans, since they cause serious zoonoses in people who come into contact with the animals.
The post-genomic era offers exciting new opportunities for vaccine research, which are expected to shorten the time of vaccine discovery. In this proposal, a novel shotgun proteomics-based approach will be applied to identify protein vaccine candidates against the pneumococcus, consisting of the surface digestion of live bacteria with proteases in mild conditions that avoid cell lysis, the recovery of generated peptides and their separation and identification by LC-MS/MS. This will allow a fast and reliable identification of highly expressed and exposed proteins. The proteins identified will be validated to assess their in vivo accessibility to antibodies. Finally, protection assays on animal models will be carried out with the selected proteins, in order to find new candidates that can enter the pipeline for vaccine development.
ACHIEVEMENTS:
In this project we have defined by proteomics the pansurfome of a collection of swine clinical isolates of S. suis, and we have obtained two recombinant proteins present in most of them, being these proteins highly expressed, exposed and accessible to antibodies. One of them has been tested in both mice and pigs, giving rise to an immunogenic and even protective response. With regard to the pneumococcus, we have started the production of a collection of recombinant proteins for protective assays and future diagnostic platforms. We have also obtained and characterised membrane vesicles produced by the pneumococcus. All these results have been materialized in 8 articles in journals, as well as two Ph.D. theses and three Master theses.