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Relapsing fever spirochaetes produce a serine protease that provides resistance to oxidative stress and killing by neutrophils
Author(s) -
Guyard Cyril,
Battisti James M.,
Raffel Sandra J.,
Schrumpf Merry E.,
Whitney Adeline R.,
Krum Jonathan G.,
Porcella Stephen F.,
Rosa Patricia A.,
DeLeo Frank R.,
Schwan Tom G.
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2006.05122.x
Subject(s) - spirochaete , biology , borrelia burgdorferi , microbiology and biotechnology , relapsing fever , virology , serine protease , lyme disease , borrelia , protease , immunology , bacteria , genetics , antibody , enzyme , biochemistry
Summary The spirochaetes that cause tick‐borne relapsing fever and Lyme disease are closely related human pathogens, yet they differ significantly in their ecology and pathogenicity. Genome sequencing of two species of relapsing fever spirochaetes, Borrelia hermsii and Borrelia turicatae, identified a chromosomal open reading frame, designated bhpA , not present in the Lyme disease spirochaete Borrelia burgdorferi . The predicted amino acid sequence of bhpA was homologous with the HtrA serine proteases, which are involved with stress responses and virulence in other bacteria. B. hermsii produced an active serine protease that was recognized by BhpA antibodies and the recombinant BhpA protein‐degraded β‐casein. bhpA was transcribed in vitro at all growth temperatures and transcription levels were slightly elevated at higher temperatures. These results correlated with the synthesis of BhpA during B. hermsii infection in mice. With the exception of Borrelia recurrentis , the bhpA gene, protein and enzymatic activity were found in all relapsing fever spirochaetes, but not in Lyme disease or related spirochaetes. Heterologous expression of bhpA in B. burgdorferi increased the spirochaete's resistance to both oxidative stress and killing by human neutrophils. Therefore, we propose that bhpA encodes a unique and functional serine protease in relapsing fever spirochaetes. This periplasmic enzyme may prevent the accumulation of proteins damaged by the innate immune response and contribute to the ability of the relapsing fever spirochaetes to achieve high cell densities in blood.