The receptor-type protein tyrosine phosphatase CD45 promotes onset and severity of IL-1ß-mediated autoinflammatory osteomyelitis.

A number of human autoinflammatory diseases manifest with severe inflammatory bone destruction. Mouse models of these diseases represent valuable tools that help us to understand molecular mechanisms triggering this bone autoinflammation. The Pstpip2cmo mouse strain is among the best characterized of these; it harbors a mutation resulting in the loss of adaptor protein PSTPIP2 and development of autoinflammatory osteomyelitis. In Pstpip2cmo mice, overproduction of interleukin-1ß (IL-1ß) and reactive oxygen species by neutrophil granulocytes leads to spontaneous inflammation of the bones and surrounding soft tissues. However, the upstream signaling events leading to this overproduction are poorly characterized. Here, we show that Pstpip2cmo mice deficient in major regulator of Src-family kinases (SFKs) receptor-type protein tyrosine phosphatase CD45 display delayed onset and lower severity of the disease, while the development of autoinflammation is not affected by deficiencies in Toll-like receptor signaling. Our data also show deregulation of pro-IL-1ß production by Pstpip2cmo neutrophils that are attenuated by CD45 deficiency. These data suggest a role for SFKs in autoinflammation. Together with previously published work on the involvement of protein tyrosine kinase spleen tyrosine kinase, they point to the role of receptors containing immunoreceptor tyrosine-based activation motifs, which after phosphorylation by SFKs recruit spleen tyrosine kinase for further signal propagation. We propose that this class of receptors triggers the events resulting in increased pro-IL-1ß synthesis and disease initiation and/or progression.

Dysregulated NADPH Oxidase Promotes Bone Damage in Murine Model of Autoinflammatory Osteomyelitis.

Autoinflammatory diseases are characterized by dysregulation of the innate immune system, leading to spontaneous inflammation. Pstpip2cmo mouse strain is a well-characterized model of this class of disorders. Because of the mutation leading to the lack of adaptor protein PSTPIP2, these animals suffer from autoinflammatory chronic multifocal osteomyelitis similar to several human syndromes. Current evidence suggests that it is driven by hyperproduction of IL-1ß by neutrophil granulocytes. In this study, we show that in addition to IL-1ß, PSTPIP2 also negatively regulates pathways governing reactive oxygen species generation by neutrophil NOX2 NADPH oxidase. Pstpip2cmo neutrophils display highly elevated superoxide production in response to a range of stimuli. Inactivation of NOX2 NADPH oxidase in Pstpip2cmo mice did not affect IL-1ß levels, and the autoinflammatory process was initiated with similar kinetics. However, the bone destruction was almost completely alleviated, suggesting that dysregulated NADPH oxidase activity is a key factor promoting autoinflammatory bone damage in Pstpip2cmo mice.

MyD88 and IL-1R signaling drive antibacterial immunity and osteoclast-driven bone loss during Staphylococcus aureus osteomyelitis.

Staphylococcus aureus is able to infect virtually all organ systems and is a frequently isolated etiologic agent of osteomyelitis, a common and debilitating invasive infection of bone. Treatment of osteomyelitis requires invasive surgical procedures and prolonged antibiotic therapy, yet is frequently unsuccessful due to extensive pathogen-induced bone damage that can limit antibiotic penetration and immune cell influx to the infectious focus. We previously established that S. aureus triggers profound alterations in bone remodeling in a murine model of osteomyelitis, in part through the production of osteolytic toxins. However, staphylococcal strains lacking osteolytic toxins still incite significant bone destruction, suggesting that host immune responses are also major drivers of pathologic bone remodeling during osteomyelitis. The objective of this study was to identify host immune pathways that contribute to antibacterial immunity during S. aureus osteomyelitis, and to define how these immune responses alter bone homeostasis and contribute to bone destruction. We specifically focused on the interleukin-1 receptor (IL-1R) and downstream adapter protein MyD88 given the prominent role of this signaling pathway in both antibacterial immunity and osteo-immunologic crosstalk. We discovered that while IL-1R signaling is necessary for local control of bacterial replication during osteomyelitis, it also contributes to bone loss during infection. Mechanistically, we demonstrate that S. aureus enhances osteoclastogenesis of myeloid precursors in vitro, and increases the abundance of osteoclasts residing on bone surfaces in vivo. This enhanced osteoclast abundance translates to trabecular bone loss, and is dependent on intact IL-1R signaling. Collectively, these data define IL-1R signaling as a critical component of the host response to S. aureus osteomyelitis, but also demonstrate that IL-1R-dependent immune responses trigger collateral bone damage through activation of osteoclast-mediated bone resorption.

Current Concepts of Osteomyelitis: From Pathologic Mechanisms to Advanced Research Methods.

Osteomyelitis is an inflammation of the bone and bone marrow that is most commonly caused by a Staphylococcus aureus infection. Much of our understanding of the underlying pathophysiology of osteomyelitis, from the perspective of both host and pathogen, has been revised in recent years, with notable discoveries including the role played by osteocytes in the recruitment of immune cells, the invasion and persistence of S. aureus in submicron channels of cortical bone, and the diagnostic role of polymorphonuclear cells in implant-associated osteomyelitis. Advanced in vitro cell culture models, such as ex vivo culture models or organoids, have also been developed over the past decade, and have become widespread in many fields, including infectious diseases. These models better mimic the in vivo environment, allow the use of human cells, and can reduce our reliance on animals in osteomyelitis research. In this review, we provide an overview of the main pathologic concepts in osteomyelitis, with a focus on the new discoveries in recent years. Furthermore, we outline the value of modern in vitro cell culture techniques, with a focus on their current application to infectious diseases and osteomyelitis in particular.

Deriving a dose and regimen for anti-glucosaminidase antibody passive-immunisation for patients with Staphylococcus aureus osteomyelitis.

Staphylococcus aureus (S. aureus) osteomyelitis remains a major clinical problem. Anti-glucosaminidase (Gmd) antibodies (1C11) are efficacious in prophylactic and therapeutic murine models. Feasibility, safety and pharmacokinetics of 1C11 passive immunisation in sheep and endogenous anti-Gmd levels were quantified in osteomyelitis patients. 3 sheep received a 500 mg intravenous (i.v.) bolus of 1C11 and its levels in sera were determined by enzyme-linked immunosorbent assay (ELISA) over 52 d. A humanised anti-Gmd monoclonal antibody, made by grafting the antigen-binding fragment (Fab) portion of 1C11 onto the fragment crystallisable region (Fc) of human IgG1, was used to make a standard curve of mean fluorescent intensity versus concentration of anti-Gmd. Anti-Gmd serum levels were determined in 297 patients with culture-confirmed S. aureus osteomyelitis and 40 healthy controls. No complications or adverse events were associated with the sheep 1C11 i.v. infusion and the estimated circulating half-life of 1C11 was 23.7 d. Endogenous anti-Gmd antibody levels in sera of osteomyelitis patients ranged from < 1 ng/mL to 300 µg/mL, with a mean concentration of 21.7 µg/mL. The estimated circulating half-life of endogenous anti-Gmd antibodies in sera of 12 patients with cured osteomyelitis was 120.4 d. A clinically relevant administration of anti-Gmd (500 mg i.v. = 7 mg/kg/70 kg human) was safe in sheep. This dose was 8 times more than the endogenous anti-Gmd levels observed in osteomyelitis patients and was predicted to have a half-life of > 3 weeks. Anti-Gmd passive immunisation has potential to prevent and treat S. aureus osteomyelitis. Further clinical development is warranted.

MRI and clinical features of acute fungal discitis/osteomyelitis.

OBJECTIVES: To compare imaging and clinical features of fungal and Staphylococcus aureus discitis-osteomyelitis (DO) for patients presenting for CT-guided biopsies. METHODS: Our study was IRB-approved and HIPAA-compliant. A group of 11 fungal DO (FG) with MRI within 7 days of the biopsy and a control group (CG) of 19 Staphylococcus aureus DO were evaluated. Imaging findings (focal vs diffuse paravertebral soft tissue abnormality, partial vs complete involvement of the disc/endplate), biopsy location, pathology, duration of back pain, immune status, history of intravenous drug, history of prior infection, current antibiotic treatment, and history of invasive intervention. Differences were assessed using the Fisher exact test and Kruskal-Wallis test. Naïve Bayes predictive modeling was performed. RESULTS: The most common fungal organisms were Candida species (9/11, 82%). The FG was more likely to have focal soft tissue abnormality (p = 0.040) and partial disc/endplate involvement (p = 0.053). The clinical predictors for fungal DO, in order of importance, back pain for 10 or more weeks, current antibiotic use for 1 week or more, and current intravenous drug use. History of invasive instrumentation within 1 year was more predictive of Staphylococcus aureus DO. CONCLUSION: MRI features (focal partial soft tissue abnormality and partial involvement of the disc/endplate) in combination with clinical features may help to predict fungal species as a causative organism for DO. KEY POINTS: • MRI features of discitis-osteomyelitis (focal partial soft tissue abnormality and partial involvement of the disc/endplate) in combination with clinical features may help to predict fungal species as a causative organism for DO.

Chronic Mycobacterium avium skin and soft tissue infection complicated with scalp osteomyelitis possibly secondary to anti-interferon-γ autoantibody formation.

BACKGROUND: Nontuberculous mycobacterial (NTM) disease is commonly an opportunistic infection frequently found in immunocompromised individuals, but sometimes can also be found in the immunocompetent hosts, especially in East Asians. The NTM separation rate in China is increasing, which reminds us to focus on NTM infections in immunocompromised populations. CASE PRESENTATION: A 43-year-old woman with a recurrent fever for more than 8-month and a right forehead surgical wounds unhealed for more than 6-month was admitted to our hospital on February 22, 2018. On arrival, several elliptic ulcers were obvious on the right forehead with pus and fibrin exudation, and the skin around the lesions was tender, reddish, no sense of fluctuation. The result of HIV serology test was negative. CD4+ T cell count was normal and tuberculosis antibody was negative. CT of the chest and head showed bone destruction. Skin biopsy on the right forehead was performed on March 13, 2018, and pathological examination of the excisional biopsy specimen found inflammatory granuloma and suppurative inflammatory changes. Broad-spectrum antibiotics were treated but the effect seemed discontent. Then debridement and skin grafting were performed on the right frontal ulcer under general anesthesia on April 3, 2018. The skin tissue culture that resected on March 13, 2018 found Nontuberculous mycobacteria grown after 78 days, so clarithromycin, ethambutol, protionamide, and amoxicillin clavulanate potassium were prescribed for anti-nontuberculous mycobacteria treatment beginning on May 31, 2018. In reviewing the case, Mycobacterium avium (M. avium) was identified in the skin tissue resected on April 3, 2018 by polymerase chain reaction (PCR) and the serum test of anti-interferon-γ autoantibodies was positive. CONCLUSIONS: This is a case report of "Mycobacterium avium SSTI (skin and soft tissue infection) and OM (osteomyelitis) with possible secondary immunodeficiency syndrome induced by anti-interferon-γ autoantibody".

Mechanisms of Immune Evasion and Bone Tissue Colonization That Make Staphylococcus aureus the Primary Pathogen in Osteomyelitis.

PURPOSE OF REVIEW: Staphylococcus aureus is the primary pathogen responsible for osteomyelitis, which remains a major healthcare burden. To understand its dominance, here we review the unique pathogenic mechanisms utilized by S. aureus that enable it to cause incurable osteomyelitis. RECENT FINDINGS: Using an arsenal of toxins and virulence proteins, S. aureus kills and usurps immune cells during infection, to produce non-neutralizing pathogenic antibodies that thwart adaptive immunity. S. aureus also has specific mechanisms for distinct biofilm formation on implants, necrotic bone tissue, bone marrow, and within the osteocyte lacuno-canicular networks (OLCN) of live bone. In vitro studies have also demonstrated potential for intracellular colonization of osteocytes, osteoblasts, and osteoclasts. S. aureus has evolved a multitude of virulence mechanisms to achieve life-long infection of the bone, most notably colonization of OLCN. Targeting S. aureus proteins involved in these pathways could provide new targets for antibiotics and immunotherapies.

Actinomycotic osteomyelitis of a long bone in an immunocompetent adult: a case report and literature review.

BACKGROUND: Actinomycosis is a rare, chronic granulomatous disease caused by Gram-positive anaerobic bacteria that colonize the oral cavity. Cervicofacial actinomycosis is the most frequent clinical presentation of actinomycosis, but hematogenous osteomyelitis at distant sites can occur in rare instance in immunocompromised or pediatric patients, only a few cases have been reported in healthy patients. Here we described a new case of distal femur osteomyelitis caused by Actinomyces in an adult patient who was immunocompetent and had no predisposing factors. CASE PRESENTATION: A woman aged 52 years with no history of trauma presented with severe pain, swelling, and increased local heat in the proximal area of the right knee 3 weeks after she first noticed discomfort. Magnetic resonance imaging showed persistent osteomyelitis of the distal metaphysis and diaphysis of the femur with a multifocal intraosseous abscess pocket. An incision and drainage of the abscess were conducted. The tissue culture, fungus culture, acid fast bacillus (AFB) culture, AFB smear, and tuberculosis polymerase chain reaction test results were negative. A pathologic examination confirmed the presence of actinomycosis. The patient was successfully treated with intravenous penicillin G for 8 weeks followed by oral amoxicillin-clavulanate for 6 weeks with repeated surgical debridement and drainage. After a 5-year follow up, the patient had no signs of recurring infection or complications and she had full range of movement in the affected knee. CONCLUSIONS: Although rare, actinomycotic osteomyelitis can occur in healthy people. Furthermore, actinomycotic osteomyelitis is easily misdiagnosed as tuberculosis in areas with a high prevalence of tuberculosis. To detect and identify the bacteria accurately, pathologic examination should be performed as well as culture tests, because the probability for culture confirmation of actinomycosis is quite low. The initial treatment is vital to a successful outcome without ostectomy or amputation.

CD14+ monocytes contribute to inflammation in chronic nonbacterial osteomyelitis (CNO) through increased NLRP3 inflammasome expression.

The pathophysiology of chronic nonbacterial osteomyelitis (CNO) remains incompletely understood. Increased NLRP3 inflammasome activation and IL-1ß release in monocytes from CNO patients was suggested to contribute to bone inflammation. Here, we dissect immune cell infiltrates and demonstrate the involvement of monocytes across disease stages. Differences in cell density and immune cell composition may help to discriminate between BOM and CNO. However, differences are subtle and infiltrates vary in CNO. In contrast to other cells involved, monocytes are a stable element during all stages of CNO, which makes them a promising candidate in the search for "drivers" of inflammation. Furthermore, we link increased expression of inflammasome components NLRP3 and ASC in monocytes with site-specific DNA hypomethylation around the corresponding genes NLRP3 and PYCARD. Our observations deliver further evidence for the involvement of pro-inflammatory monocytes in the pathophysiology of CNO. Cellular and molecular alterations may serve as disease biomarkers and/or therapeutic targets.

Chronic recurrent multifocal osteomyelitis in children and adults: current understanding and areas for development.

Since the first descriptions of chronic recurrent multifocal osteomyelitis in the 1970s, there have been numerous case reports in the literature; both unusual case reports and case series from all over the world. Our understanding of the pathogenesis has significantly changed, with it now being regarded as an autoinflammatory condition. Treatment options have also expanded, but little progress has been made in developing the evidence for treatments. Advancing gene studies have provided a mouse model, but the quest for a single gene to match the phenotype has been elusive. Early cohorts of patients have grown up into adults, allowing prospective data to inform the expected outcomes.

PSTPIP2, a Protein Associated with Autoinflammatory Disease, Interacts with Inhibitory Enzymes SHIP1 and Csk.

Mutations in the adaptor protein PSTPIP2 are the cause of the autoinflammatory disease chronic multifocal osteomyelitis in mice. This disease closely resembles the human disorder chronic recurrent multifocal osteomyelitis, characterized by sterile inflammation of the bones and often associated with inflammation in other organs, such as the skin. The most critical process in the disease's development is the enhanced production of IL-1ß. This excessive IL-1ß is likely produced by neutrophils. In addition, the increased activity of macrophages, osteoclasts, and megakaryocytes has also been described. However, the molecular mechanism of how PSTPIP2 deficiency results in this phenotype is poorly understood. Part of the PSTPIP2 inhibitory function is mediated by protein tyrosine phosphatases from the proline-, glutamic acid-, serine- and threonine-rich (PEST) family, which are known to interact with the central part of this protein, but other regions of PSTPIP2 not required for PEST-family phosphatase binding were also shown to be indispensable for PSTPIP2 function. In this article, we show that PSTPIP2 binds the inhibitory enzymes Csk and SHIP1. The interaction with SHIP1 is of particular importance because it binds to the critical tyrosine residues at the C terminus of PSTPIP2, which is known to be crucial for its PEST-phosphatase-independent inhibitory effects in different cellular systems. We demonstrate that in neutrophils this region is important for the PSTPIP2-mediated suppression of IL-1ß processing and that SHIP1 inhibition results in the enhancement of this processing. We also describe deregulated neutrophil response to multiple activators, including silica, Ab aggregates, and LPS, which is suggestive of a rather generalized hypersensitivity of these cells to various external stimulants.

Chronic Recurrent Multifocal Osteomyelitis (CRMO): Presentation, Pathogenesis, and Treatment.

PURPOSE OF REVIEW: Chronic non-bacterial osteomyelitis (CNO) with its most severe form chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory bone disorder. We summarize the clinical presentation, diagnostic approaches, most recent advances in understanding the pathophysiology, and available treatment options and outcomes in CNO/CRMO. RECENT FINDINGS: Though the exact molecular pathophysiology of CNO/CRMO remains somewhat elusive, it appears likely that variable defects in the TLR4/MAPK/inflammasome signaling cascade result in an imbalance between pro- and anti-inflammatory cytokine expressions in monocytes from CNO/CRMO patients. In this context, we present previously unpublished data on cytokine and chemokine expression in monocytes and tissues. CNO/CRMO is an autoinflammatory bone disorder resulting from imbalanced cytokine expression from innate immune cells. Though the exact molecular pathophysiology remains unclear, variable molecular defects appear to result in inflammasome activation and pro-inflammatory cytokine expression in monocytes from CNO/CRMO patients. Recent advances suggest signaling pathways and single molecules as biomarkers for CNO/CRMO as well as future treatment targets.

Inflammasome-independent IL-1ß mediates autoinflammatory disease in Pstpip2-deficient mice.

Chronic recurrent multifocal osteomyelitis (CRMO) is a human autoinflammatory disorder that primarily affects bone. Missense mutation (L98P) of proline-serine-threonine phosphatase-interacting protein 2 (Pstpip2) in mice leads to a disease that is phenotypically similar to CRMO called chronic multifocal osteomyelitis (cmo). Here we show that deficiency of IL-1RI in cmo mice resulted in a significant reduction in the time to onset of disease as well as the degree of bone pathology. Additionally, the proinflammatory cytokine IL-1ß, but not IL-1α, played a critical role in the pathology observed in cmo mice. In contrast, disease in cmo mice was found to be independent of the nucleotide-binding domain, leucine-rich repeat-containing family, pyrin domain-containing 3 (NLRP3) inflammasome as well as caspase-1. Neutrophils, but not bone marrow-derived macrophages, from cmo mice secreted increased IL-1ß in response to ATP, silica, and Pseudomonas aeruginosa compared with neutrophils from WT mice. This aberrant neutrophil response was sensitive to inhibition by serine protease inhibitors. These results demonstrate an inflammasome-independent role for IL-1ß in disease progression of cmo and implicate neutrophils and neutrophil serine proteases in disease pathogenesis. These data provide a rationale for directly targeting IL-1RI or IL-1ß as a therapeutic strategy in CRMO.

Primary fusobacterium osteomyelitis and pyomyositis of the thigh in an immunocompetent young adult.

An unusual case of an immunocompetent young adult with osteomyelitis and pyomyositis of his right thigh is presented. Despite the absence of typical clinical signs, a high index of suspicion and 16S RNA PCR led to an early diagnosis of Fusobacterium infection and subsequent successful multidisciplinary treatment.

Experimental Simulation of Traumatic Osteomyelitis in Rats.

A model of traumatic osteomyelitis in rats is created. The disease development was evaluated by bone marrow myelograms, results of scintigraphy, and histological studies.

[INFLUENCE OF SAUSSUREA CONTROVERSA AND FILLIPENDULA ULMARIA EXTRACTS ON IMMUNOLOGICAL REACTIVITY OF RATS WITH EXPERIMENTAL OSTEOMYELITIS.]

The influence of Saussurea controversa DC and Fillipendula ulmaria (L.) Maxim extracts on the immunological reactivity of rats with experimental osteomyelitis has been studied. The application of these extracts on the background of antibiotic therapy normalized the immunological reactivity indices: (i) reduced the levels of total immunoglobulins, IgM and IgG and (ii) increased the percentage of active neutrophils and their absorption capacity, as well as the percentage of completion of phagocytosis. The treatment with plant extracts reduced the acute inflammatory reaction and increased the total number of megakaryocites as compared to those upon antibiotic therapy.

[Chronic nonbacterial osteomyelitis]. / Krooninen-ei-bakteeriperäinen osteomyeliitti.

Chronic nonbacterial osteomyelitis is an autoinflammatory disease occurring mainly in children and adolescents, typically involving recurrent or persistent osteitic foci. The symptom is bone pain, possibly accompanied by soft tissue tenderness. Some patients exhibit symptoms of systemic inflammation. The. precise etiology of the disease is not known, but an imbalance of inflammatory and anti-inflammatory cytokines is presumed to play a role in the development of the disease. While an anti-inflammatory analgesic is in most cases sufficient to calm down the osteitis, the use of corticosteroids, anti- TNF-a inhibitors or bisphosphonates is required in some cases.

Disseminated Mycobacterium avium complex infection in a child with partial dominant interferon gamma receptor 1 deficiency in India.

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare condition characterized by clinical disease caused by weakly virulent mycobacteria. All genes mutated in MSMD patients are involved in IFN-γ immunity. Autosomal partial dominant (PD) interferon-γ receptor 1 (IFN-γR1) deficiency is the most frequent abnormality affecting the group of MSMD patients leading to impaired response of IFN-γ. We describe here a patient from India with disseminated infection due to Mycobacterium avium intracellulare (MAC) including multifocal osteomyelitis and BCG disease. A heterozygous mutation in exon 6 of IFNGR1 gene was identified, conferring an autosomal PD IFN-γR1 deficiency. Patient had recurrence of mycobacterial disease during antibiotic therapy for which subcutaneous IFN-γ was added as a modality of treatment for resistant MAC infection.