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Infection and Immunity, December 2001, p. 7527-7534, Vol. 69, No. 12
Oral Health Sciences Unit, School of Dental
Science, The University of Melbourne, Melbourne, Victoria,
Australia
Received 22 November 2000/Returned for modification 27 March
2001/Accepted 11 September 2001
Extracellular Arg-x- and Lys-x-specific cysteine proteinases
are considered important virulence factors and pathogenic markers for
Porphyromonas gingivalis, a bacterium implicated as a
major etiological agent of chronic periodontitis. Three genes.
rgpA, rgpB, and kgp,
encode an Arg-x-specific proteinase and adhesins (RgpA), an
Arg-x-specific proteinase (RgpB), and a Lys-x-specific proteinase and
adhesins (Kgp), respectively. The contribution to pathogenicity of each
of the proteinase genes of P. gingivalis W50 was
investigated in a murine lesion model using isogenic mutants lacking
RgpA, RgpB, and Kgp. Whole-cell Arg-x-specific proteolytic activity of
both the RgpA
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.12.7527-7534.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Role of RgpA, RgpB, and Kgp Proteinases in
Virulence of Porphyromonas gingivalis W50 in a Murine
Lesion Model
and RgpB
isogenic mutants was
significantly reduced (3- to 4-fold) relative to that of the wild-type
W50. However, for the Kgp
isogenic mutant, whole-cell
Arg-x activity was similar to that of the wild-type strain. Whole-cell
Lys-x proteolytic activity of the RgpA
and
RgpB
mutants was not significantly different from that of
wild-type W50, whereas the Kgp
mutant was devoid of Lys-x
whole-cell proteolytic activity. Sodium dodecyl sulfate-polyacrylamide
gel electrophoresis and Western blot analysis using proteinase-specific
antibodies of cell sonicates of the wild-type and mutant strains showed
that the proteinase catalytic domain of each of the mutants was not
expressed. This analysis further showed that RgpB appeared as
72- and 80-kDa bands, and the catalytic domains of RgpA and Kgp
appeared as processed 45-kDa and 48-kDa bands, respectively. In the
murine lesion model, mice were challenged with three doses of each
mutant and wild-type strain. At the lower dose (3.0 × 109 viable-cells), no lesions were recorded for each of the
mutants, whereas wild-type W50 induced large ulcerative lesions. At a
dose of 6.0 × 109 viable-cells, all the mice
challenged with the wild-type strain died, whereas mice challenged with
the RgpA
and RgpB
isogenic mutants did not
die but developed lesions. Mice challenged with the Kgp
isogenic mutant at this dose did not develop lesions. At a 1.2 × 1010 viable-cell dose, only 40% of mice challenged with
the Kgp
mutant developed lesions, and these lesions were
significantly smaller than lesions induced by the wild-type strain at
the 3.0 × 109 viable-cell dose. All the mice
challenged with the RgpA
mutant died at the 1.2 × 1010 viable-cell dose, whereas only 20% died when
challenged with the RgpB
mutant at this dose. Wild-type
phenotype was restored to the RgpB
mutant by
complementation with plasmid pNJR12::rgpB
containing the rgpB gene. There was no difference
between the pNJR12::rgpB-complemented RgpB
mutant and the wild-type W50 strain in whole-cell
Arg-x activity, protein profile, or virulence in the murine lesion
model. These results show that the three proteinases, RgpA, RgpB, and
Kgp, all contributed to virulence of P. gingivalis W50
in the murine lesion model and that the order in which they contributed
was Kgp
RgpB
RgpA.
*
Corresponding author. Mailing address: Oral Health
Sciences Unit, School of Dental Science, The University of Melbourne,
711 Elizabeth Street, Melbourne, Victoria 3000, Australia. Phone: 61 3 9341 0270. Fax: 61 3 9341 0236. E-mail:
e.reynolds{at}unimelb.edu.au.
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