Protein-Based Pneumococcal Vaccine May Provide Universal Protection

A novel vaccine that targets protein antigens common to all strains of Streptococcus pneumoniae successfully protected mice from becoming infected with the bacteria during a preclinical trial.

Investigators at Children's Hospital Boston (MA, USA) and their collaborators at Genocea Biosciences, Inc. (Cambridge, MA, USA) used a powerful proteomic screening protocol to identify protein antigens from S. pneumoniae that would stimulate the immune system's TH17 cells (CD4+ T cells) to secrete the potent cytokine IL-17A.

In their paper published in the February 17, 2011, issue of the journal Cell Host & Microbe, the investigators reported that the identified antigens were effective mucosal immunogens that protected mice from nasopharyngeal colonization by S. pneumoniae in a CD4+ T cell- and IL-17A-dependent manner. The identified antigens stimulated IL-17A secretion from splenocytes isolated from mice previously exposed to live pneumococcus, indicating that the antigens were effectively presented during mucosal colonization. Similarly, human peripheral blood mononuclear cells (PBMCs) secreted IL-17A when stimulated with the antigens, indicating similar TH17 responses were primed during natural exposure to pneumococcus.

"By combining advances in molecular biology, immunology, and bioinformatics, the strategy we use at Genocea allows comprehensive, rapid, and unbiased screens of every protein produced by an infectious agent to identify the most effective T cell- stimulating antigens,” said contributing author Dr. Jessica Flechtner, vice president for research at Genocea Biosciences. "We look forward to our continued collaboration and the development of an improved pneumococcal vaccine.”

The identified antigens represent strong candidates for a protein subunit vaccine designed to prevent colonization by S. pneumoniae. "The next steps, already in motion, are to optimize the formulation of this vaccine, confirm its efficacy and safety in animals, and then proceed to human trials,” said senior author Dr. Richard Malley, associate professor of pediatrics at Children's Hospital Boston.

The findings of this study suggest that the proteomic screening method described here will be a powerful tool for vaccine development against pathogens where infection of the human host begins with mucosal colonization.

Related Links:
Children's Hospital Boston
Genocea Biosciences, Inc.