Some Drugs Have Two Faces: Paradoxical Colitis in a Patient with Psoriatic Arthritis Previously Treated with Etanercept and IL-17 Inhibitors

Tumor necrosis factor-alpha (TNF-α) and interleukin-17 (IL-17) inhibitors are among the most potent treatments for inflammatory arthropathies including rheumatoid arthritis, psoriasis, and spondyloarthropathies. The availability of these biologic agents have revolutionized the management of these conditions and improved patient outcomes. Though generally safe, these biologics may contribute to the induction or exacerbation of colitis. This paradoxical colitis has been observed in patients on TNF-α inhibitor etanercept and IL-17 inhibitors (secukinumab and ixekizumab). We report a case of a 46-year-old female with psoriasis and psoriatic arthritis who presented with gastrointestinal symptoms after treatment with etanercept and IL-17 inhibitors. She was later diagnosed with paradoxical indeterminate colitis that was masked and treated by subsequent biologics given for her RA and psoriatic arthritis. In this report, we will discuss the importance of considering paradoxical colitis in the differential diagnosis for patients even several years after TNF-α/IL-17 inhibitor initiation and explain why careful consideration must be made when initiating these colitis-inducing agents to treat patients with inflammatory disorders.

Mapping the T cell repertoire to a complex gut bacterial community

Certain bacterial strains from the microbiome induce a potent, antigen-specific T cell response1-5. However, the specificity of microbiome-induced T cells has not been explored at the strain level across the gut community. Here, we colonize germ-free mice with complex defined communities (roughly 100 bacterial strains) and profile T cell responses to each strain. The pattern of responses suggests that many T cells in the gut repertoire recognize several bacterial strains from the community. We constructed T cell hybridomas from 92 T cell receptor (TCR) clonotypes; by screening every strain in the community against each hybridoma, we find that nearly all the bacteria-specific TCRs show a one-to-many TCR-to-strain relationship, including 13 abundant TCR clonotypes that each recognize 18 Firmicutes. By screening three pooled bacterial genomic libraries, we discover that these 13 clonotypes share a single target: a conserved substrate-binding protein from an ATP-binding cassette transport system. Peripheral regulatory T cells and T helper 17 cells specific for an epitope from this protein are abundant in community-colonized and specific pathogen-free mice. Our work reveals that T cell recognition of commensals is focused on widely conserved, highly expressed cell-surface antigens, opening the door to new therapeutic strategies in which colonist-specific immune responses are rationally altered or redirected.

Strain dropouts reveal interactions that govern the metabolic output of the gut microbiome

The gut microbiome is complex, raising questions about the role of individual strains in the community. Here, we address this question by constructing variants of a complex defined community in which we eliminate strains that occupy the bile acid 7α-dehydroxylation niche. Omitting Clostridium scindens (Cs) and Clostridium hylemonae (Ch) eliminates secondary bile acid production and reshapes the community in a highly specific manner: eight strains change in relative abundance by >100-fold. In single-strain dropout communities, Cs and Ch reach the same relative abundance and dehydroxylate bile acids to a similar extent. However, Clostridium sporogenes increases >1,000-fold in the ΔCs but not ΔCh dropout, reshaping the pool of microbiome-derived phenylalanine metabolites. Thus, strains that are functionally redundant within a niche can have widely varying impacts outside the niche, and a strain swap can ripple through the community in an unpredictable manner, resulting in a large impact on an unrelated community-level phenotype.

Design, construction, and in vivo augmentation of a complex gut microbiome

Efforts to model the human gut microbiome in mice have led to important insights into the mechanisms of host-microbe interactions. However, the model communities studied to date have been defined or complex, but not both, limiting their utility. Here, we construct and characterize in vitro a defined community of 104 bacterial species composed of the most common taxa from the human gut microbiota (hCom1). We then used an iterative experimental process to fill open niches: germ-free mice were colonized with hCom1 and then challenged with a human fecal sample. We identified new species that engrafted following fecal challenge and added them to hCom1, yielding hCom2. In gnotobiotic mice, hCom2 exhibited increased stability to fecal challenge and robust colonization resistance against pathogenic Escherichia coli. Mice colonized by either hCom2 or a human fecal community are phenotypically similar, suggesting that this consortium will enable a mechanistic interrogation of species and genes on microbiome-associated phenotypes.

A play in four acts: Staphylococcus aureus abscess formation

Staphylococcus aureus is an important human pathogen that causes skin and soft tissue abscesses. Abscess formation is not unique to staphylococcal infection and purulent discharge has been widely considered a physiological feature of healing and tissue repair. Here we present a different view, whereby S. aureus deploys specific virulence factors to promote abscess lesions that are distinctive for this pathogen. In support of this model, only live S. aureus is able to form abscesses, requiring genes that act at one or more of four discrete stages during the development of these infectious lesions. Protein A and coagulases are distinctive virulence attributes for S. aureus, and humoral immune responses specific for these polypeptides provide protection against abscess formation in animal models of staphylococcal disease.

IsdA and IsdB antibodies protect mice against Staphylococcus aureus abscess formation and lethal challenge

Staphylococcus aureus is the most frequent cause of bacteremia and hospital-acquired infection, however a vaccine that prevents staphylococcal disease is currently not available. Two sortase-anchored surface proteins, IsdA and IsdB, have been identified as subunit vaccines that, following active immunization, protect experimental animals against intravenous challenge with staphylococci. Here we investigate the molecular basis of this immunity and report that, when passively transferred to naïve mice, purified antibodies directed against IsdA or IsdB protected against staphylococcal abscess formation and lethal intravenous challenge. When added to mouse blood, IsdA- or IsdB-specific antibodies did not promote rapid opsonophagocytic killing of wild-type staphylococci. Antibodies directed against IsdA interfered with heme-binding and IsdB antibodies perturbed the ability of this surface protein to bind hemoglobin. As the structural genes for isdA and isdB are required for heme-iron scavenging during the pathogenesis of infection, we hypothesize that IsdA and IsdB antibodies may at least in part provide protection against staphylococci by interfering with the pathogen's heme-iron scavenging mechanisms.

Nontoxigenic protein A vaccine for methicillin-resistant Staphylococcus aureus infections in mice

The current epidemic of hospital- and community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections has caused significant human morbidity, but a protective vaccine is not yet available. Prior infection with S. aureus is not associated with protective immunity. This phenomenon involves staphylococcal protein A (SpA), an S. aureus surface molecule that binds to Fcgamma of immunoglobulin (Ig) and to the Fab portion of V(H)3-type B cell receptors, thereby interfering with opsonophagocytic clearance of the pathogen and ablating adaptive immune responses. We show that mutation of each of the five Ig-binding domains of SpA with amino acid substitutions abolished the ability of the resulting variant SpA(KKAA) to bind Fcgamma or Fab V(H)3 and promote B cell apoptosis. Immunization of mice with SpA(KKAA) raised antibodies that blocked the virulence of staphylococci, promoted opsonophagocytic clearance, and protected mice against challenge with highly virulent MRSA strains. Furthermore, SpA(KKAA) immunization enabled MRSA-challenged mice to mount antibody responses to many different staphylococcal antigens.

Genetic requirements for Staphylococcus aureus abscess formation and persistence in host tissues

Staphylococcus aureus infections are associated with abscess formation and bacterial persistence; however, the genes that enable this lifestyle are not known. We show here that following intravenous infection of mice, S. aureus disseminates rapidly into organ tissues and elicits abscess lesions that develop over weeks but cannot be cleared by the host. Staphylococci grow as communities at the center of abscess lesions and are enclosed by pseudocapsules, separating the pathogen from immune cells. By testing insertional variants in genes for cell wall-anchored surface proteins, we are able to infer the stage at which these molecules function. Fibrinogen-binding proteins ClfA and ClfB are required during the early phase of staphylococcal dissemination. The heme scavenging factors IsdA and IsdB, as well as SdrD and protein A, are necessary for abscess formation. Envelope-associated proteins, Emp and Eap, are either required for abscess formation or contribute to persistence. Fluorescence microscopy revealed Eap deposition within the pseudocapsule, whereas Emp was localized within staphylococcal abscess communities. Antibodies directed against envelope-associated proteins generated vaccine protection against staphylococcal abscess formation. Thus, staphylococci employ envelope proteins at discrete stages of a developmental program that enables abscess formation and bacterial persistence in host tissues.

Relationship between osteopenia and lumbar intervertebral disc degeneration in ovariectomized rats

Ovariectomy (OVX) can cause bone loss in rats, but little is known about how it also induces lumbar intervertebral disc degeneration (LVD). This study investigated how estrogen deficiency affected intervertebral discs in OVX rats. Thirty 3-month-old female Sprague-Dawley rats were divided randomly into three equal groups. The baseline control group (BL) was killed at the beginning of the experiment. An ovariectomy was performed in 10 rats (OVX group) and another group of 10 rats was subjected to a sham surgery (Sham group). The OVX rats were untreated after the surgery to allow for the development of moderate osteopenia. Bone mineral density (BMD) measurement and bone histomorphometric analysis were applied to the segments of lumbar spines in all rats killed 6 months after surgery. The pathological changes of intervertebral discs were observed and the degree of LVD was scored by a histological scoring system. The BMD of the spines (L3-L5) in the OVX group decreased significantly compared with the Sham group. The bone volume indices in the OVX group were significantly lower, but the bone turnover rate parameters were significantly higher than those in the Sham group (P < 0.01). The histological scores for LVD in the OVX group were significantly higher than those in the Sham group (P < 0.01). There was a significant negative correlation between the BMD and Grade II discs in the OVX rats (P = 0.042). In conclusion, LVD occurs in the OVX rats and the degeneration of cartilage end plates may be a pathogenic factor in disc degeneration.

Oxidative stress-induced apoptosis of cochlear sensory cells: otoprotective strategies

Apoptosis is an important process, both for normal development of the inner ear and for removal of oxidative-stress damaged sensory cells from the cochlea. Oxidative-stressors of auditory sensory cells include: loss of trophic factor support, ischemia-reperfusion, and ototoxins. Loss of trophic factor support and cisplatin ototoxicity, both initiate the intracellular production of reactive oxygen species and free radicals. The interaction of reactive oxygen species and free radicals with membrane phospholipids of auditory sensory cells creates aldehydic lipid peroxidation products. One of these aldehydes, 4-hydroxynonenal, functions as a mediator of apoptosis for both auditory neurons and hair cells. We present several approaches for the prevention of auditory sensory loss from reactive oxygen species-induced apoptosis: 1) preventing the formation of reactive oxygen species; (2) neutralizing the toxic products of membrane lipid peroxidation; and 3) blocking the damaged sensory cells' apoptotic pathway.

Calpain inhibitors protect auditory sensory cells from hypoxia and neurotrophin-withdrawal induced apoptosis

Inhibitors of calpain have been shown to protect nerve growth factor (NGF)-deprived ciliary ganglion neurons and hypoxic cortical neurons. Calpains have been identified in the cochlea and are active during ischemic injury. Since apoptosis can be initiated by loss of neurotrophic support, hypoxia, and ototoxins (e.g., cisplatin, CDDP), the role of calpain inhibitors under these conditions was examined in auditory hair cells and neurons. Dissociated spiral ganglion neuron (SGN) cell cultures and organ of Corti explants from P3 rats were used to test the efficacy of calpain inhibitors as otoprotective molecules. Our results indicate that calpain inhibitor I, calpain inhibitor II, and leupeptin all provided significant protection of SGNs against neurotrophin-withdrawal and hypoxia-induced apoptosis. The increase in neuronal survival ranged from 2.16 to 2.31 times greater than in untreated neurotrophin-withdrawn SGN cell cultures. BOC-Asp(Ome)-Fluoromethyl Ketone (B-D-FMK), a general caspase inhibitor, increased neuronal survival 2.16 times more. Neuronal survival rates were from 1.88 to 2.27 times greater than in untreated, hypoxic neurons and hair cell survival rates were from 1.98 to 2.03 times greater than untreated, hypoxic organ of Corti explants. However, protection of auditory hair cells and neurons from CDDP-induced damage (10 and 6 micrograms/ml, respectively) was limited with any of these calpain inhibitors. Apoptotic pathways initiated by neurotrophin-deprivation and ototoxic stress (e.g., CDDP) have been shown to be different. Our results agree with this finding, with neurotrophin-withdrawal and hypoxia, but not CDDP damage-induced apoptosis being calpain-dependent.

Lateral ventricular effacement as an isolated sonographic finding in premature infants: prevalence and significance

OBJECTIVE

The sonographic finding of effaced lateral ventricles in premature infants, defined as the absence of visible CSF within the lateral ventricles on both coronal and sagittal sonograms, may be cause to suspect diffuse cerebral edema, especially as published reference standards do not address this phenomenon. This investigation was undertaken to determine the prevalence and significance of effaced lateral ventricles without associated parenchymal abnormality (isolated lateral ventricular effacement, or ILVE) in premature infants.

MATERIALS AND METHODS

Sonographic records of 398 consecutive newborns examined from January 1 to December 31, 1993, were reviewed retrospectively to identify those premature infants (< 36 weeks of gestational age) whose initial sonograms showed no evidence of intracranial hemorrhage, ventriculomegaly, structural abnormality, or abnormal parenchymal echogenicity. We identified 142 neonates who met these criteria. Patients were separated into two groups on the basis of whether they had at least one sonographic study in which CSF was not visible within both lateral ventricles on coronal and sagittal images. Medical records were reviewed to assess neurologic outcome.

RESULTS

Forty patients (28%) had at least one sonogram demonstrating ILVE, with neurologic follow-up in 33 (representing group A). One hundred two patients (72%) never demonstrated ILVE, with neurologic follow-up established in 86 (representing group B). A comparison of the two groups showed no significant difference in the development of ischemic injury (one patient in each group). ILVE was first detected on the initial sonogram obtained (mean, 4 days) in 30 of the 33 neonates in group A. ILVE was demonstrated beyond the seventh day of life in 30%. Of the 89 patients whose initial sonograms showed CSF in the lateral ventricles (86 in group B and three in group A), three (3%) subsequently had sonograms that showed ILVE; all three were normal at follow-up.

CONCLUSION

ILVE in premature infants is common and not associated with neurologic deficits indicative of hypoxic-ischemic encephalopathy. By itself, ILVE is not a significant finding.