Bacteroides Fragilis OMP A: Utility as a Live Vaccine Vector for Biodefense Agents.

摘要

We are studying the utility of using B. fragilis OmpA as a vehicle on which to put antigenic epitopes of organisms that can be used in bioterror, with the aim of eventually constructing a vaccine vehicle vector. OmpA is the major outer membrane protein of B. fragilis, a gram negative anaerobe that normally resides in the gut. There are four ompA in the genome. The purpose of this study was to construct a B. fragilis ompA deletant and to begin to characterize the function of OmpA, as well as the specific function(s) of the various loops exposed on the surface. We constructed an ompA1 deletant (WAL 186) and confirmed the deletion by sequence analysis of the deletion junction. RT PCR indicated that all 4 ompAs are transcribed in the parental strain, and confirmed that ompA1 is not transcribed in WAL 186 (the ompA1 deletant). However, we found that ompA4 was also not transcribed in the deletion mutant. No significant change was seen in MICs of a variety of antimicrobials for the deletion mutant compared to the parental strain. WAL 186 was more sensitive than WAL 108 to high salt and to SDS. Gram stain analysis showed no change was seen between WAL 108 and WAL 186 grown overnight in normal media (long, somewhat pleomorphic rods). but overnight growth in hyperosmolar media (200 mM NaCI) resulted in very small, round forms for both WAL 108 and WAL 186. In addition. expression of ompA1 and ompA4 was diminished in WAL 108 (the parental strain.). We will use this OmpA deletant to determining specific loop functions and design a vaccine.