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- Calander, Ann-Marie, 1957, et al.
(author)
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Impact of staphylococcal protease expression on the outcome of infectious arthritis
- 2004
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In: Microbes Infect. - : Elsevier BV. - 1286-4579. ; 6:2, s. 202-6
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Journal article (peer-reviewed)abstract
- The exoproteases of Staphylococcus aureus have been proposed as virulence factors during S. aureus infections. To investigate this, we used the wild-type S. aureus strain 8325-4 and its mutants devoid of aureolysin, serine protease, and cysteine protease, respectively, in a well-established model of septic arthritis in mice. The inactivation of the exoprotease genes did not affect the frequency or the severity of joint disease. We conclude that in the model of haematogenously spread staphylococcal arthritis, the bacterial proteases studied do not act as virulence factors.
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| 4. |
- Gjertsson, Inger, 1962, et al.
(author)
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The role of B cell CD22 expression in Staphylococcus aureus arthritis and sepsis
- 2004
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In: Microbes Infect. - 1286-4579. ; 6:4, s. 377-82
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Journal article (peer-reviewed)abstract
- Severe Staphylococcus aureus infections give rise to a pronounced antigen-specific and polyclonal B cell response with elevated serum immunoglobulin levels. However, it has been difficult to correlate the antibody levels with the clinical outcome of sepsis and/or arthritis concerning both protection and pathogenic aspects. Earlier studies have shown that macrophages and neutrophils are of great importance for bacterial clearance. However, deletion of the complete B cell compartment affected neither S. aureus-induced arthritis nor survival. MZ B cells are believed to be of importance for clearance of blood-borne antigens and have been implicated in protection against S. aureus infections. CD22 is a B-cell-specific inhibitory receptor binding to alpha2,6-linked sialic acids, and deficiency in CD22 leads to a 75% reduction of the MZ B cell compartment. CD22-/- mice and congeneic controls were inoculated intravenously with an arthritogenic dose of live S. aureus. No differences between the groups were detected regarding frequency and severity of arthritis, survival, bacterial clearance, or induction of inflammatory response. This study shows explicitly that a reduced MZ B cell compartment in the absence of CD22 expression does not interfere with the inflammatory response during S. aureus infection.
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| 5. |
- Hultgren, Olof H., 1970, et al.
(author)
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T-box transcription-factor-deficient mice display increased joint pathology and failure of infection control during staphylococcal arthritis.
- 2004
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In: Microbes and infection / Institut Pasteur. - : Elsevier BV. - 1286-4579. ; 6:6, s. 529-35
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Journal article (peer-reviewed)abstract
- To study the impact of T-box transcription factor (T-bet) on initiation and progression of Staphylococcus aureus sepsis and arthritis, T-bet-deficient mice (T-bet(-/-)) and their wild-type controls (T-bet(+/+)) were intravenously inoculated with 8 x 10(6) S. aureus. Already 48 h after inoculation of S. aureus, T-bet-deficient mice displayed increased frequency (62% versus 19%, P = 0.002) as well as severity of arthritis compared with wild-type controls. The bacterial counts were significantly increased in T-bet(-/-) mice compared with T-bet(+/+) as measured in kidneys 72 h after the inoculation (4.3 +/- 1.8 x 10(7) versus 3.2 +/- 3.2 x 10(6) colony-forming units (CFU); P = 0.003). As expected, T-bet-deficient mice displayed significantly decreased production of IFN-gamma (10-15-fold) at 24 and 72 h after bacterial inoculation compared with wild-type mice. Interestingly, in the absence of T-bet, serum IL-4 was decreased at 24 h. IL-6 did not differ at early stage of infection but was sixfold increased in T-bet(-/-) mice over T-bet(+/+) animals at 72 h postinoculation. Ten days after the inoculation, T-bet(-/-) mice still displayed significantly more pronounced weight loss and increased serum IL-6 levels, probably due to increased bacterial burden compared with T-bet(+/+) mice. The cumulative mortality was 19% in T-bet mice (5/27) and 0% (0/27) in control animals (P = 0.05). In conclusion, T-bet plays an important role in early response to S. aureus infection, protecting against bacterial accumulation, cachexia and septic death. Furthermore T-bet downregulates joint inflammation in the early phase of disease.
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| 8. |
- Palmqvist, Niklas, 1974, et al.
(author)
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Clumping factor A-mediated virulence during Staphylococcus aureus infection is retained despite fibrinogen depletion
- 2004
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In: Microbes Infect. - : Elsevier BV. - 1286-4579. ; 6:2, s. 196-201
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Journal article (peer-reviewed)abstract
- Clumping factor A (ClfA), a fibrinogen-binding protein expressed on the Staphylococcus aureus cell surface, has previously been shown to act as a virulence factor in experimental septic arthritis. Although the interaction between ClfA and fibrinogen is assumed to be of importance for the virulence of S. aureus, this has not been demonstrated in any in vivo model of infection. Therefore, the objective of this study was to investigate the contribution of this interaction to ClfA-mediated virulence in murine S. aureus-induced arthritis. Ancrod, a serine protease with thrombin-like activity, was used to induce in vivo depletion of fibrinogen in mice. Ancrod treatment significantly aggravated septic arthritis following inoculation with a ClfA-expressing strain (Newman) compared to control treatment. Also, ancrod treatment tended to enhance the arthritis induced by a clfA mutant strain (DU5876), indicating that fibrinogen depletion exacerbates septic arthritis in a ClfA-independent manner. Most importantly, the ClfA-expressing strain was much more arthritogenic than the isogenic clfA mutant, following inoculation of fibrinogen-depleted mice. This finding indicates that the interaction between ClfA and free fibrinogen is not required for ClfA-mediated functions contributing to S. aureus virulence. It is conceivable that ClfA contributes to the virulence of S. aureus through interactions with other host ligands than fibrinogen.
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| 9. |
- Palmqvist, Niklas, 1974, et al.
(author)
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Expression of staphylococcal clumping factor A impedes macrophage phagocytosis
- 2004
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In: Microbes Infect. - : Elsevier BV. - 1286-4579. ; 6:2, s. 188-95
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Journal article (peer-reviewed)abstract
- Clumping factor A (ClfA), a fibrinogen-binding protein linked to the Staphylococcus aureus cell wall, is an important virulence factor in infection models, e.g., of septic arthritis. However, the mechanism(s) by which ClfA contributes to the virulence of the bacterium is unknown. In the present study, the impact of ClfA expression on the phagocytosis of S. aureus by macrophages was investigated using clfA-positive and clfA-negative isogenic strains. Furthermore, the possible contribution of ClfA to the proinflammatory and immunostimulatory activity of S. aureus was studied. Our results indicate that ClfA expression significantly protects S. aureus against macrophage phagocytosis. This protection does not require the presence of intact fibrinogen, a ligand for ClfA. ClfA expression by S. aureus enhanced the proliferative response of spleen cells. On the other hand, a clfA mutant strain caused more release of proinflammatory mediators by macrophages than its clfA-positive parental strain. Both the protection against phagocytosis and the enhanced immunostimulatory activity provided by ClfA expression are likely to contribute to the in vivo virulence of S. aureus.
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| 10. |
- Verdrengh, Margareta, 1942, et al.
(author)
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IL-1 receptor-associated kinase 1 mediates protection against Staphylococcus aureus infection.
- 2004
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In: Microbes and infection / Institut Pasteur. - : Elsevier BV. - 1286-4579. ; 6:14, s. 1268-72
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Journal article (peer-reviewed)abstract
- The interleukin-1 receptor-associated kinase-1 (IRAK-1) mediates signal transduction from Toll-like/IL-1/IL-18 receptors. Though a critical protective role against Staphylococcus aureus infection has been previously attributed to myeloid differentiation factor 88 (MyD88) and IRAK-4, both also involved in TLR/IL-1/IL-18 signaling, the role of IRAK-1 is unknown. IRAK-1-deficient (IRAK-1-/-) and wild-type mice were inoculated i.v. with 2 x 10(7) or 1 x 10(6) S. aureus per mouse to evaluate the role of IRAK-1 in S. aureus sepsis. Since IRAK-1 transduces IL-1R signals, IL-1R-/- mice were also included in experiments. IRAK-1-/- mice are susceptible to a high dose of S. aureus compared to wild-type controls. In contrast to the high mortality and extensive weight loss seen in IL-1R-deficient mice in response to 1 x 10(6) S. aureus, IRAK-1-/- mice are resistant to this low dose of S. aureus. Thus IRAK-1 plays an important role in the host response to staphylococcal sepsis.
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