All ETDs from UAB

Advisory Committee Chair

David E Briles

Advisory Committee Members

Scott R Barnum

William Benjamin

Moon H Nahm

Allan J Zajac

Document Type

Dissertation

Date of Award

2013

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

PCV13 is the current pneumococcal protein conjugated vaccine made up of the 13 most clinically relevant capsular polysaccharides. While protective, it is limited to a small portion of the overall serotypes of Streptococcus pneumoniae. The possibility of "serotype replacement" by serotypes not covered by the vaccine and the high cost of producing this conjugated polysaccharide vaccine stress the need for a protein based vaccine, one that is more broad in its protection. Pneumococcal surface protein A (PspA) has been shown to be both immunogenic and protective in mice and is a promising protein vaccine candidate. However, there are no current accepted methods to assay the protective capacity of immunized human serum to passively protect mice from challenge, a major first step in vaccine development. For polysaccharide based pneumococcal vaccines, an Opsonization Phagocytosis Killing Assay (OPKA) can measure the ability of immune serum to protect against pneumococcal challenge. This OPKA does not function well enough with antibodies against proteins to serve as a surrogate for a PspA based vaccine. By using the phenomenon of "surface phagocytosis", the ability of immune cells to phagocytose bacteria on the surface of an agar plate, we developed a Modified Surface Killing Assay (MSKA) in which we could test various monoclonal antibodies raised against PspA for their ability to passively protect mice form lethal pneumococcal challenge. Furthermore, we were able to differentiate between monoclonal antibodies that had better protection against pneumococcal challenge than others, and were able to use the MSKA to determine portions of the PspA protein that were more/less immunogenic and protective than others. We present here the MSKA as a potential and useful surrogate assay for protection to screening immune sera in the design of a pneumococcal vaccine based on PspA.

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