Open AccessLipooligosaccharide P k (Galα1-4Galβ1-4Glc) Epitope of Moraxella catarrhalis Is a Factor in Resistance to Bactericidal Activity Mediated by Normal Human Serum
Author(s) -
Anthony Zaleski,
N. Karoline Scheffler,
Peter Densen,
Frank K. N. Lee,
Anthony A. Campagnari,
Bradford W. Gibson,
Michael A. Apicella
Publication year - 2000
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.68.9.5261-5268.2000
Subject(s) - moraxella catarrhalis , moraxella (branhamella) catarrhalis , microbiology and biotechnology , moraxella , biology , neisseriaceae , epitope , immunology , antibody , bacteria , haemophilus influenzae , antibiotics , genetics
Moraxella catarrhalis is a respiratory pathogen responsible for acute bacterial otitis media in children and exacerbation of chronic bronchitis in adults.M. catarrhalis strains are frequently resistant to the bactericidal activity of normal human serum. In order to determine if the lipooligosaccharide (LOS) ofM. catarrhalis has a role in serum resistance, the UDP-glucose-4-epimerase (galE ) gene was identified, cloned, and sequenced and a deletion/insertion mutation was introduced intoM. catarrhalis strain 2951. GalE enzymatic activity, measured in whole-cell lysates, was ablated inM. catarrhalis 2951galE . Mass spectrometric analysis of LOS isolated with hot phenol-water confirmed that strain 2951 produced a type A LOS. These studies showed that the LOS from 2951galE had lost two hexose residues due to thegalE mutation and that the resultant LOS structure lacked the (Galα1-4Galβ1-4Glc) Pk epitope found onM. catarrhalis 2951. Wild-typeM. catarrhalis 2951 is resistant to complement-mediated serum bactericidal activity. In contrast, a greater than 2-log10 -unit reduction in CFU occurred after incubation of 2951galE in either 50 or 25% pooled human serum (PNHS), and CFU in 10% PNHS decreased by about 1 log10 unit. These studies suggest that the Pk epitope of the LOS may be an important factor in the resistance ofM. catarrhalis to the complement-mediated bactericidal effect of normal human serum.