Structural and Functional Analysis of Moraxella catarrhalis Adhesins MCAP and OMPCD
Moraxella catarrhalis is a Gram-negative bacterium and is an important cause of otitis media in children and respiratory tract infections in adults with chronic obstructive pulmonary disease. Because of the emergence of antibiotic resistance among M. catarrhalis clinical isolates and the prevalence of M. catarrhalis infections, it is desirable to develop a vaccine for this organism. Most efforts towards designing a vaccine against M. catarrhalis infections are directed at studying surface antigens, especially outer membrane proteins. Adhesins are good vaccine candidates because they are often conserved within the bacterial species, and may contain conserved surface exposed epitope(s). In addition, targeting adhesins may interfere with adherence to mucosal surfaces, thus preventing bacteria from establishing an infection. The purpose of this dissertation research was to study the adherence mechanism of the Moraxella catarrhalis adhesin protein (McaP) and the outer membrane protein CD (OMPCD), and to define their vaccine potential. Our first set of studies demonstrated that McaP is an autotransporter protein containing a passenger domain, aa 51-336, that mediates adherence to human lung cells. In addition, we demonstrated that antibodies against McaP significantly reduce adherence to A549 human lung cells; thus, McaP is an important M. catarrhalis adhesin. This study also demonstrated that McaP protein is well conserved among the 16 clinical isolates tested, and contains surface exposed epitopes, which are all characteristics of a vaccine antigen. Our second set of studies demonstrated that OMPCD contains two domains specifying adherence to A549 human lung cells using three complementary approaches: E. coli cells expressing truncated OMPCD proteins, direct binding of recombinant His-tagged OMPCD proteins, and OMPCD polypeptides expressed on the surface of E. coli through the McaP display system. These cell-binding domains were delineated to aa 16-150 and aa 261-300 of O35E-OMPCD protein. These domains may be used as vaccine antigens in future studies.
School:University of Toledo Health Science Campus
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:outer membrane protein cd mcap surface display system vaccine antigens adhesin of moraxella catarrhalis cell binding domain
Date of Publication:01/01/2007