Degree Name

PhD (Doctor of Philosophy)

Program

Biomedical Sciences

Date of Award

12-2013

Committee Chair or Co-Chairs

Alok Agrawal, Ph.D.

Committee Members

Gregory A. Ordway, Ph.D., Antonio E. Rusiñol, Ph.D., Donald A. Ferguson, Jr., Ph.D., Richard M. Kostrzewa, Ph.D., Scott. S. Champney, Ph.D.

Abstract

Human C-reactive protein (CRP) increases survival of and decreases bacteremia in mice infected with Streptococcus pneumoniae. Such protection of mice against pneumococcal infection is seen only when CRP is administered into mice 6 hours before to 2 hours after the injection of pneumococci, but not when CRP is given to mice at a later time. Our first aim was to define the mechanism of CRP-mediated initial protection of mice against infection. It was proposed that CRP binds to phosphocholine (PCh) moieties present in the cell wall and activates the complement system on the pneumococcal surface that kills the pathogen. We generated a CRP mutant F66A/T76Y/E81A incapable of binding to PCh. Mutant CRP did not protect mice from pneumococcal infection. Thus, the proposed hypothesis was correct; the PCh-binding property of CRP contributes to the protection of mice against pneumococcal infection. Our second aim was to investigate why CRP was not protective during the late stages of infection. Pneumococci are known to recruit an inhibitor of complement activation, factor H, from the host to their surface to escape complement attack. We considered the ability of CRP, in its nonnative form, to bind to factor H, and generated a CRP mutant E42Q/F66A/T76Y/E81A capable of binding to factor H. In vivo experiments using the quadruple CRP mutant are in progress. We anticipate that the combination of wild-type and quadruple mutant CRP should be protective during the late stages of infection; wild-type CRP would bind to PCh and activate complement while mutant CRP would cover factor H to prevent its complement-inhibitory activity. Our long-term goal is to explore the possibility of developing a CRP-based strategy to treat pneumococcal infection.

Document Type

Dissertation - Open Access

Copyright

Copyright by the authors.

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