Antibiotics with Interleukin-15 inhibition reduces joint inflammation and bone erosions but not cartilage destruction in Staphylococcus aureus-induced arthritis

Background: Staphylococcus aureus-induced arthritis causes rapid joint destruction, often leading to disabling joint damage despite antibiotics. We have previously shown that IL-15 inhibition without antibiotics is beneficial in S. aureus-induced arthritis. We therefore hypothesized that inhibition of IL-15, in combination with antibiotics, might represent a useful therapy that would both reduce inflammation and joint destruction, but preserve the host's ability to clear the infection. Methods: Female wildtype C57BL/6 mice were intravenously inoculated with the TSST-1-producing LS-1 strain of S. aureus with 0.8x108 S. aureus LS-1/mouse. Three days later the treatment was started consisting of cloxacillin followed by flucloxacillin, together with either anti-IL-15 antibodies (aIL-15ab) or control antibodies. Outcomes included survival, weight change, bacterial clearance, and joint damage. Results: The addition of aIL-15ab to antibiotics in S. aureus-induced arthritis reduced synovitis and bone erosions compared to controls. The number of bone-resorbing osteoclasts in the joints was reduced, whereas cartilage destruction was not significantly altered. Importantly, the combination therapy did not adversely affect the clinical outcome of S. aureus-induced arthritis, such as survival, weight change or compromise the host's ability to clear the infection. Conclusions: As the clinical outcome of S. aureus-induced arthritis was not affected, the addition of aIL-15ab to antibiotics ought to be safe. Taken together, the combination of aIL-15ab and antibiotics is a beneficial, but not optimal, treatment of S. aureus-induced arthritis as it reduces synovitis and bone erosions but has a limited effect on cartilage destruction

Identification and Characterization of σS, a Novel Component of the Staphylococcus aureus Stress and Virulence Responses

S. aureus is a highly successful pathogen that is speculated to be the most common cause of human disease. The progression of disease in S. aureus is subject to multi-factorial regulation, in response to the environments encountered during growth. This adaptive nature is thought to be central to pathogenesis, and is the result of multiple regulatory mechanisms employed in gene regulation. In this work we describe the existence of a novel S. aureus regulator, an as yet uncharacterized ECF-sigma factor (σS), that appears to be an important component of the stress and pathogenic responses of this organism. Using biochemical approaches we have shown that σS is able to associates with core-RNAP, and initiate transcription from its own coding region. Using a mutant strain we determined that σS is important for S. aureus survival during starvation, extended exposure to elevated growth temperatures, and Triton X-100 induced lysis. Coculture studies reveal that a σS mutant is significantly outcompeted by its parental strain, which is only exacerbated during prolonged growth (7 days), or in the presence of stressor compounds. Interestingly, transcriptional analysis determined that under standard conditions, S. aureus SH1000 does not initiate expression of sigS. Assays performed hourly for 72h revealed expression in typically background ranges. Analysis of a potential anti-sigma factor, encoded downstream of sigS, revealed it to have no obvious role in the upregulation of sigS expression. Using a murine model of septic arthritis, sigS-mutant infected animals lost significantly less weight, developed septic arthritis at significantly lower levels, and had increased survival rates. Studies of mounted immune responses reveal that sigS-mutant infected animals had significantly lower levels of IL-6, indicating only a weak immunological response. Finally, strains of S. aureus lacking sigS were far less able to undergo systemic dissemination, as determined by bacterial loads in the kidneys of infected animals. These results establish that σS is an important component in S. aureus fitness, and in its adaptation to stress. Additionally it appears to have a significant role in its pathogenic nature, and likely represents a key component in the S. aureus regulatory network

Inactivation of the Ecs ABC Transporter of Staphylococcus aureus Attenuates Virulence by Altering Composition and Function of Bacterial Wall

Peer reviewe

RA-MAP, molecular immunological landscapes in early rheumatoid arthritis and healthy vaccine recipients

Rheumatoid arthritis (RA) is a chronic inflammatory disorder with poorly defined aetiology characterised by synovial inflammation with variable disease severity and drug responsiveness. To investigate the peripheral blood immune cell landscape of early, drug naive RA, we performed comprehensive clinical and molecular profiling of 267 RA patients and 52 healthy vaccine recipients for up to 18 months to establish a high quality sample biobank including plasma, serum, peripheral blood cells, urine, genomic DNA, RNA from whole blood, lymphocyte and monocyte subsets. We have performed extensive multi-omic immune phenotyping, including genomic, metabolomic, proteomic, transcriptomic and autoantibody profiling. We anticipate that these detailed clinical and molecular data will serve as a fundamental resource offering insights into immune-mediated disease pathogenesis, progression and therapeutic response, ultimately contributing to the development and application of targeted therapies for RA.</p

Toll-Like Receptor 2 Stimulation of Osteoblasts Mediates Staphylococcus Aureus Induced Bone Resorption and Osteoclastogenesis through Enhanced RANKL

Severe Staphylococcus aureus (S. aureus) infections pose an immense threat to population health and constitute a great burden for the health care worldwide. Inter alia, S. aureus septic arthritis is a disease with high mortality and morbidity caused by destruction of the infected joints and systemic bone loss, osteoporosis. Toll-Like receptors (TLRs) are innate immune cell receptors recognizing a variety of microbial molecules and structures. S. aureus recognition via TLR2 initiates a signaling cascade resulting in production of various cytokines, but the mechanisms by which S. aureus causes rapid and excessive bone loss are still unclear. We, therefore, investigated how S. aureus regulates periosteal/endosteal osteoclast formation and bone resorption. S. aureus stimulation of neonatal mouse parietal bone induced ex vivo bone resorption and osteoclastic gene expression. This effect was associated with increased mRNA and protein expression of receptor activator of NF-kappa B ligand (RANKL) without significant change in osteoprotegerin (OPG) expression. Bone resorption induced by S. aureus was abolished by OPG. S. aureus increased the expression of osteoclastogenic cytokines and prostaglandins in the parietal bones but the stimulatory effect of S. aureus on bone resorption and Tnfsf11 mRNA expression was independent of these cytokines and prostaglandins. Stimulation of isolated periosteal osteoblasts with S. aureus also resulted in increased expression of Tnfsf11 mRNA, an effect lost in osteoblasts from Tlr2 knockout mice. S. aureus stimulated osteoclastogenesis in isolated periosteal cells without affecting RANKL-stimulated resorption. In contrast, S. aureus inhibited RANKL-induced osteoclast formation in bone marrow macrophages. These data show that S. aureus enhances bone resorption and periosteal osteoclast formation by increasing osteoblast RANKL production through TLR2. Our study indicates the importance of using different in vitro approaches for studies of how S. aureus regulates osteoclastogenesis to obtain better understanding of the complex mechanisms of S. aureus induced bone destruction in vivo

Estradiol ameliorates arthritis and protects against systemic bone loss in Staphylococcus aureus infection in mice

INTRODUCTION: Staphylococcus aureus is a common cause of bacterial arthritis, which is associated with progressive bone loss in affected joints. We have recently shown that S. aureus infection also induces a significant systemic bone loss in mice. This study was performed to assess the effect of estradiol treatment on the clinical course and outcome of S. aureus arthritis and on infection-induced bone loss in experimental S. aureus infection. METHODS: Mice were ovariectomized, treated with estradiol or placebo, and S. aureus infection established by intravenous inoculation of bacteria. RESULTS: Estradiol treatment was found to significantly decrease the frequency and clinical severity of S. aureus arthritis, a finding that was accompanied with significantly higher serum levels of interleukin-10 in estradiol treated mice. Estradiol was also highly protective against S. aureus-induced systemic trabecular and cortical bone loss. Lack of endogenous estrogens and S. aureus infection had additive effects on trabecular bone loss. In fact, S. aureus infected, ovariectomized mice lost as much as 76% of their trabecular bone mass. CONCLUSIONS: Treatment with estradiol ameliorates S. aureus arthritis and is protective against infection-induced systemic bone loss in experimental S. aureus infection

Estradiol ameliorates arthritis and protects against systemic bone loss in Staphylococcus aureus infection in mice

INTRODUCTION: Staphylococcus aureus is a common cause of bacterial arthritis, which is associated with progressive bone loss in affected joints. We have recently shown that S. aureus infection also induces a significant systemic bone loss in mice. This study was performed to assess the effect of estradiol treatment on the clinical course and outcome of S. aureus arthritis and on infection-induced bone loss in experimental S. aureus infection. METHODS: Mice were ovariectomized, treated with estradiol or placebo, and S. aureus infection established by intravenous inoculation of bacteria. RESULTS: Estradiol treatment was found to significantly decrease the frequency and clinical severity of S. aureus arthritis, a finding that was accompanied with significantly higher serum levels of interleukin-10 in estradiol treated mice. Estradiol was also highly protective against S. aureus-induced systemic trabecular and cortical bone loss. Lack of endogenous estrogens and S. aureus infection had additive effects on trabecular bone loss. In fact, S. aureus infected, ovariectomized mice lost as much as 76% of their trabecular bone mass. CONCLUSIONS: Treatment with estradiol ameliorates S. aureus arthritis and is protective against infection-induced systemic bone loss in experimental S. aureus infection

<i>S</i>. <i>aureus</i> stimulates RANKL in isolated mouse calvarial osteoblasts independent on cytokine but dependent on prostaglandin productions and TLR2.

<p>(<b>A</b>) <i>S</i>. <i>aureus</i> time-dependently stimulated <i>Tnfsf11</i> mRNA without affecting <i>Tnfrsf11b</i> mRNA in mouse osteoblasts. (<b>B</b>) Concentration-dependent stimulation of <i>Tnfsf11</i> mRNA, with no effect on <i>Tnfrsf11b</i> mRNA, by <i>S</i>. <i>aureus</i> (3x10⁶ CFU/ml). (<b>C</b>) <i>S</i>. <i>aureus</i> (3x10⁶ CFU/ml) upregulated the mRNA expression of <i>Il1b</i>, <i>Il11</i>, <i>Il6</i>, <i>Lif</i>, <i>Osm</i> and <i>Tnfsf2</i> in osteoblasts. (<b>D</b>) The stimulatory effect by <i>S</i>. <i>aureus</i> (3x10⁶ CFU/ml) on <i>Tnfsf11</i> mRNA expression in osteoblasts was unaffected by adding a mixture of antibodies neutralizing IL-1β, IL-6, IL-11, LIF, OSM and TNF-α. (<b>E</b>) <i>S</i>. <i>aureus</i> (3x10⁶ CFU/ml) stimulated <i>Ptgs2</i> mRNA in mouse osteoblasts. (<b>F</b>) Indomethacin (1 μmol/l) abolished <i>Tnfsf11</i> mRNA in osteoblasts induced by <i>S</i>. <i>aureus</i> (3x10⁶ CFU/ml). (<b>G, H</b>) The stimulatory effect by <i>S</i>. <i>aureus</i> (3x10⁶ CFU/ml) on <i>Tnfsf11</i> and <i>Ptgs2</i> mRNA was observed in osteoblasts from <i>wild type</i> mice but not from <i>Tlr2</i> deficient mice. Data are means of 5 observations and SEM is given as vertical bars when larger than the radius of the symbol. In Fig 4A, effects on <i>Tnfsf11</i> mRNA were statistically significant at 1–48 h (<i>P</i><0.001). In Fig 4B, effects on <i>Tnfsf11</i> mRNA were statistically significant at 10⁶ and 3x10⁶ (<i>P</i><0.01) and at 10⁷ and 3x10⁷ (<i>P</i><0.001) CFU/ml. ***<i>P</i><0.001 compared to unstimulated control (D-G) or to <i>S</i>. <i>aureus</i> stimulated osteoblasts (G).</p