HEMOGLOBIN-INDUCED VIRULENCE IN STREPTOCOCCUSPNEUMONIAE

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1 Project summary 2 3 Streptococcus pneumoniae (Spn) colonizes the human upper airways of most children forming biofilms. Due 4 to mechanisms still not understood, nasopharyngeal carriage leads to invasive pneumococcal disease (IPD) 5 that kills more than one million individuals every year worldwide. IPD is characterized by colonization of the 6 lungs with subsequent translocation to the pleural cavity, and bloodstream, to cause lethal bacteremia. Once 7 in circulation, Spn translocates to the meninges causing meningitis or invades cardiomyocytes forming 8 intracellular biofilms that lead to cardiac damage. Although pneumococcal vaccination has reduced the 9 burden of disease, vaccines only target a subset of strains and have little to no impact against pneumococcal 10 bacteremia and meningitis. Efforts made in the last few years by this proposal's PIs have resulted in the 11 groundbreaking discovery that hemoglobin (Hb), a molecule that is accessible to Spn during carriage in the 12 upper airways and colonization of lung and heart, triggers the formation of robust biofilms and translocation 13 of pneumococci through human lung cells. These observations strongly support a new scientific premise that 14 Hb signaling is key to Spn colonization and disease processes. Our overarching goal is to identify the proteins 15 by which hemoglobin (Hb) triggers Spn virulence leading to the pathophysiology of pneumococcal disease 16 and to begin to describe the mechanism of Hb signaling in Spn. Specific Aim 1 will use a reverse genetic 17 approach to identify the proteins required for Hb to transduce a signal leading to the formation of biofilms, 18 and invasion of lung cells and cardiomyocytes. Whether this signal acts along with, or it is separated from, an 19 increased pool of intracellular iron will also be investigated. Specific Aim 2 will implement an agnostic 20 strategy (Tn-seq) to determine additional surface proteins and the regulators necessary for Hb signaling and 21 test key candidates defective in Hb signaling in vivo using murine models for pneumococcal colonization and 22 disease. At completion, this work will identify new proteins key for the pathophysiology of IPD, new antigens 23 for pneumococcal vaccines, and new targets for inhibitors that interfere with the establishment and 24 progression of IPD. 25 26 27 28 29 30