Mild respiratory COVID can cause multi-lineage neural cell and myelin dysregulation.

COVID survivors frequently experience lingering neurological symptoms that resemble cancer-therapy-related cognitive impairment, a syndrome for which white matter microglial reactivity and consequent neural dysregulation is central. Here, we explored the neurobiological effects of respiratory SARS-CoV-2 infection and found white-matter-selective microglial reactivity in mice and humans. Following mild respiratory COVID in mice, persistently impaired hippocampal neurogenesis, decreased oligodendrocytes, and myelin loss were evident together with elevated CSF cytokines/chemokines including CCL11. Systemic CCL11 administration specifically caused hippocampal microglial reactivity and impaired neurogenesis. Concordantly, humans with lasting cognitive symptoms post-COVID exhibit elevated CCL11 levels. Compared with SARS-CoV-2, mild respiratory influenza in mice caused similar patterns of white-matter-selective microglial reactivity, oligodendrocyte loss, impaired neurogenesis, and elevated CCL11 at early time points, but after influenza, only elevated CCL11 and hippocampal pathology persisted. These findings illustrate similar neuropathophysiology after cancer therapy and respiratory SARS-CoV-2 infection which may contribute to cognitive impairment following even mild COVID.

Distinguishing features of long COVID identified through immune profiling.

Post-acute infection syndromes may develop after acute viral disease1. Infection with SARS-CoV-2 can result in the development of a post-acute infection syndrome known as long COVID. Individuals with long COVID frequently report unremitting fatigue, post-exertional malaise, and a variety of cognitive and autonomic dysfunctions2-4. However, the biological processes that are associated with the development and persistence of these symptoms are unclear. Here 275 individuals with or without long COVID were enrolled in a cross-sectional study that included multidimensional immune phenotyping and unbiased machine learning methods to identify biological features associated with long COVID. Marked differences were noted in circulating myeloid and lymphocyte populations relative to the matched controls, as well as evidence of exaggerated humoral responses directed against SARS-CoV-2 among participants with long COVID. Furthermore, higher antibody responses directed against non-SARS-CoV-2 viral pathogens were observed among individuals with long COVID, particularly Epstein-Barr virus. Levels of soluble immune mediators and hormones varied among groups, with cortisol levels being lower among participants with long COVID. Integration of immune phenotyping data into unbiased machine learning models identified the key features that are most strongly associated with long COVID status. Collectively, these findings may help to guide future studies into the pathobiology of long COVID and help with developing relevant biomarkers.

Diverse functional autoantibodies in patients with COVID-19.

COVID-19 manifests with a wide spectrum of clinical phenotypes that are characterized by exaggerated and misdirected host immune responses1-6. Although pathological innate immune activation is well-documented in severe disease1, the effect of autoantibodies on disease progression is less well-defined. Here we use a high-throughput autoantibody discovery technique known as rapid extracellular antigen profiling7 to screen a cohort of 194 individuals infected with SARS-CoV-2, comprising 172 patients with COVID-19 and 22 healthcare workers with mild disease or asymptomatic infection, for autoantibodies against 2,770 extracellular and secreted proteins (members of the exoproteome). We found that patients with COVID-19 exhibit marked increases in autoantibody reactivities as compared to uninfected individuals, and show a high prevalence of autoantibodies against immunomodulatory proteins (including cytokines, chemokines, complement components and cell-surface proteins). We established that these autoantibodies perturb immune function and impair virological control by inhibiting immunoreceptor signalling and by altering peripheral immune cell composition, and found that mouse surrogates of these autoantibodies increase disease severity in a mouse model of SARS-CoV-2 infection. Our analysis of autoantibodies against tissue-associated antigens revealed associations with specific clinical characteristics. Our findings suggest a pathological role for exoproteome-directed autoantibodies in COVID-19, with diverse effects on immune functionality and associations with clinical outcomes.

Sex differences in immune responses that underlie COVID-19 disease outcomes.

There is increasing evidence that coronavirus disease 2019 (COVID-19) produces more severe symptoms and higher mortality among men than among women1-5. However, whether immune responses against severe acute respiratory syndrome coronavirus (SARS-CoV-2) differ between sexes, and whether such differences correlate with the sex difference in the disease course of COVID-19, is currently unknown. Here we examined sex differences in viral loads, SARS-CoV-2-specific antibody titres, plasma cytokines and blood-cell phenotyping in patients with moderate COVID-19 who had not received immunomodulatory medications. Male patients had higher plasma levels of innate immune cytokines such as IL-8 and IL-18 along with more robust induction of non-classical monocytes. By contrast, female patients had more robust T cell activation than male patients during SARS-CoV-2 infection. Notably, we found that a poor T cell response negatively correlated with patients' age and was associated with worse disease outcome in male patients, but not in female patients. By contrast, higher levels of innate immune cytokines were associated with worse disease progression in female patients, but not in male patients. These findings provide a possible explanation for the observed sex biases in COVID-19, and provide an important basis for the development of a sex-based approach to the treatment and care of male and female patients with COVID-19.

Longitudinal analyses reveal immunological misfiring in severe COVID-19.

Recent studies have provided insights into the pathogenesis of coronavirus disease 2019 (COVID-19)1-4. However, the longitudinal immunological correlates of disease outcome remain unclear. Here we serially analysed immune responses in 113 patients with moderate or severe COVID-19. Immune profiling revealed an overall increase in innate cell lineages, with a concomitant reduction in T cell number. An early elevation in cytokine levels was associated with worse disease outcomes. Following an early increase in cytokines, patients with moderate COVID-19 displayed a progressive reduction in type 1 (antiviral) and type 3 (antifungal) responses. By contrast, patients with severe COVID-19 maintained these elevated responses throughout the course of the disease. Moreover, severe COVID-19 was accompanied by an increase in multiple type 2 (anti-helminths) effectors, including interleukin-5 (IL-5), IL-13, immunoglobulin E and eosinophils. Unsupervised clustering analysis identified four immune signatures, representing growth factors (A), type-2/3 cytokines (B), mixed type-1/2/3 cytokines (C), and chemokines (D) that correlated with three distinct disease trajectories. The immune profiles of patients who recovered from moderate COVID-19 were enriched in tissue reparative growth factor signature A, whereas the profiles of those with who developed severe disease had elevated levels of all four signatures. Thus, we have identified a maladapted immune response profile associated with severe COVID-19 and poor clinical outcome, as well as early immune signatures that correlate with divergent disease trajectories.

Lack of association between pandemic chilblains and SARS-CoV-2 infection.

An increased incidence of chilblains has been observed during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic and attributed to viral infection. Direct evidence of this relationship has been limited, however, as most cases do not have molecular evidence of prior SARS-CoV-2 infection with PCR or antibodies. We enrolled a cohort of 23 patients who were diagnosed and managed as having SARS-CoV-2-associated skin eruptions (including 21 pandemic chilblains [PC]) during the first wave of the pandemic in Connecticut. Antibody responses were determined through endpoint titration enzyme-linked immunosorbent assay and serum epitope repertoire analysis. T cell responses to SARS-CoV-2 were assessed by T cell receptor sequencing and in vitro SARS-CoV-2 antigen-specific peptide stimulation assays. Immunohistochemical and PCR studies of PC biopsies and tissue microarrays for evidence of SARS-CoV-2 were performed. Among patients diagnosed and managed as "covid toes" during the pandemic, we find a percentage of prior SARS-CoV-2 infection (9.5%) that approximates background seroprevalence (8.5%) at the time. Immunohistochemistry studies suggest that SARS-CoV-2 staining in PC biopsies may not be from SARS-CoV-2. Our results do not support SARS-CoV-2 as the causative agent of pandemic chilblains; however, our study does not exclude the possibility of SARS-CoV-2 seronegative abortive infections.

Site-Specific Identification of Protein S-Acylation by IodoTMT0 Labeling and Immobilized Anti-TMT Antibody Resin Enrichment.

Protein S-acylation is a reversible post-translational modification (PTM). It is present on diverse proteins and has important roles in regulating protein function. Aminolysis with hydroxylamine is widely used in the global identification of the PTM. However, the identification is indirect. Distinct criteria have been used for identification, and the false discovery rate has not been addressed. Here, we report a site-specific method for S-acylation identification based on tagging of S-acylation sites with iodoTMT0. Efforts to improve the performance of the method and confidence of identification are discussed, highlighting the importance of reducing contaminant peptides and keeping the recovery rate consistent between aliquots with or without hydroxylamine treatment. With very stringent criteria, presumptive S-acylation sites of 269, 684, 695, and 780 were identified from HK2 cells, HK11 cells, mouse brain, and mouse liver samples, respectively. Among them, the newly identified protein S-acylation sites are equivalent to 34% of human and 24% of mouse S-acylation sites reported previously. In addition, false-positive rates for S-acylation identification and S-acylation abundances were estimated. Significant differences in S-acylation abundance were found from different samples (from 0.08% in HK2 cells to 0.76% in mouse brain), and the false-positive rates were significantly higher for samples with a low abundance of S-acylation.

Advances in proteomic profiling of pediatric kidney diseases.

Chronic kidney disease (CKD) can progress to kidney failure and require dialysis or transplantation, while early diagnosis can alter the course of disease and lead to better outcomes in both pediatric and adult patients. Significant CKD comorbidities include the manifestation of cardiovascular disease, heart failure, coronary disease, and hypertension. The pathogenesis of chronic kidney diseases can present as subtle and especially difficult to distinguish between different glomerular pathologies. Early detection of adult and pediatric CKD and detailed mechanistic understanding of the kidney damage can be helpful in delaying or curtailing disease progression via precise intervention toward diagnosis and prognosis. Clinically, serum creatinine and albumin levels can be indicative of CKD, but often are a lagging indicator only significantly affected once kidney function has severely diminished. The evolution of proteomics and mass spectrometry technologies has begun to provide a powerful research tool in defining these mechanisms and identifying novel biomarkers of CKD. Many of the same challenges and advances in proteomics apply to adult and pediatric patient populations. Additionally, proteomic analysis of adult CKD patients can be transferred directly toward advancing our knowledge of pediatric CKD as well. In this review, we highlight applications of proteomics that have yielded such biomarkers as PLA2R, SEMA3B, and other markers of membranous nephropathy as well as KIM-1, MCP-1, and NGAL in lupus nephritis among other potential diagnostic and prognostic markers. The potential for improving the clinical toolkit toward better treatment of pediatric kidney diseases is significantly aided by current and future development of proteomic applications.

Serine Protease HTRA1 as a Novel Target Antigen in Primary Membranous Nephropathy.

BACKGROUND: Identification of target antigens PLA2R, THSD7A, NELL1, or Semaphorin-3B can explain the majority of cases of primary membranous nephropathy (MN). However, target antigens remain unidentified in 15%-20% of patients. METHODS: A multipronged approach, using traditional and modern technologies, converged on a novel target antigen, and capitalized on the temporal variation in autoantibody titer for biomarker discovery. Immunoblotting of human glomerular proteins followed by differential immunoprecipitation and mass spectrometric analysis was complemented by laser-capture microdissection followed by mass spectrometry, elution of immune complexes from renal biopsy specimen tissue, and autoimmune profiling on a protein fragment microarray. RESULTS: These approaches identified serine protease HTRA1 as a novel podocyte antigen in a subset of patients with primary MN. Sera from two patients reacted by immunoblotting with a 51-kD protein within glomerular extract and with recombinant human HTRA1, under reducing and nonreducing conditions. Longitudinal serum samples from these patients seemed to correlate with clinical disease activity. As in PLA2R- and THSD7A- associated MN, anti-HTRA1 antibodies were predominantly IgG4, suggesting a primary etiology. Analysis of sera collected during active disease versus remission on protein fragment microarrays detected significantly higher titers of anti-HTRA1 antibody in active disease. HTRA1 was specifically detected within immune deposits of HTRA1-associated MN in 14 patients identified among three cohorts. Screening of 118 "quadruple-negative" (PLA2R-, THSD7A-, NELL1-, EXT2-negative) patients in a large repository of MN biopsy specimens revealed a prevalence of 4.2%. CONCLUSIONS: Conventional and more modern techniques converged to identify serine protease HTRA1 as a target antigen in MN.

Proteomic Analysis Identifies Distinct Glomerular Extracellular Matrix in Collapsing Focal Segmental Glomerulosclerosis.

BACKGROUND: The mechanisms leading to extracellular matrix (ECM) replacement of areas of glomerular capillaries in histologic variants of FSGS are unknown. This study used proteomics to test the hypothesis that glomerular ECM composition in collapsing FSGS (cFSGS) differs from that of other variants. METHODS: ECM proteins in glomeruli from biopsy specimens of patients with FSGS not otherwise specified (FSGS-NOS) or cFSGS and from normal controls were distinguished and quantified using mass spectrometry, verified and localized using immunohistochemistry (IHC) and confocal microscopy, and assessed for gene expression. The analysis also quantified urinary excretion of ECM proteins and peptides. RESULTS: Of 58 ECM proteins that differed in abundance between cFSGS and FSGS-NOS, 41 were more abundant in cFSGS and 17 in FSGS-NOS. IHC showed that glomerular tuft staining for cathepsin B, cathepsin C, and annexin A3 in cFSGS was significantly greater than in other FSGS variants, in minimal change disease, or in membranous nephropathy. Annexin A3 colocalized with cathepsin B and C, claudin-1, phosphorylated ERK1/2, and CD44, but not with synaptopodin, in parietal epithelial cells (PECs) infiltrating cFSGS glomeruli. Transcripts for cathepsins B and C were increased in FSGS glomeruli compared with normal controls, and urinary excretion of both cathepsins was significantly greater in cFSGS compared with FSGS-NOS. Urinary excretion of ECM-derived peptides was enhanced in cFSGS, although in silico analysis did not identify enhanced excretion of peptides derived from cathepsin B or C. CONCLUSIONS: ECM differences suggest that glomerular sclerosis in cFSGS differs from that in other FSGS variants. Infiltration of activated PECs may disrupt ECM remodeling in cFSGS. These cells and their cathepsins may be therapeutic targets.

Association between ALS and retroviruses: evidence from bioinformatics analysis.

BACKGROUND: Emerging evidence suggests retroviruses play a role in the pathophysiology of amyotrophic lateral sclerosis (ALS). Specifically, activation of ancient viral genes embedded in the human genome is theorized to lead to motor neuron degeneration. We explore whether connections exist between ALS and retroviruses through protein interaction networks (PIN) and pathway analysis, and consider the potential roles in drug target discovery. Protein database and pathway/network analytical software including Ingenuity Pathway BioProfiler, STRING, and CytoScape were utilized to identify overlapping protein interaction networks and extract core cluster (s) of retroviruses and ALS. RESULTS: Topological and statistical analysis of the ALS-PIN and retrovirus-PIN identified a shared, essential protein network and a core cluster with significant connections with both networks. The identified core cluster has three interleukin molecules IL10, Il-6 and IL-1B, a central apoptosis regulator TP53, and several major transcription regulators including MAPK1, ANXA5, SQSTM1, SREBF2, and FADD. Pathway enrichment analysis showed that this core cluster is associated with the glucocorticoid receptor singling and neuroinflammation signaling pathways. For confirmation purposes, we applied the same methodology to the West Nile and Polio virus, which demonstrated trivial connectivity with ALS, supporting the unique connection between ALS and retroviruses. CONCLUSIONS: Bioinformatics analysis provides evidence to support pathological links between ALS and retroviral activation. The neuroinflammation and apoptotic regulation pathways are specifically implicated. The continuation and further analysis of large scale genome studies may prove useful in exploring genes important in retroviral activation and ALS, which may help discover new drug targets.

CureGN Study Rationale, Design, and Methods: Establishing a Large Prospective Observational Study of Glomerular Disease.

RATIONALE & OBJECTIVES: Glomerular diseases, including minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, and immunoglobulin A (IgA) nephropathy, share clinical presentations, yet result from multiple biological mechanisms. Challenges to identifying underlying mechanisms, biomarkers, and new therapies include the rarity of each diagnosis and slow progression, often requiring decades to measure the effectiveness of interventions to prevent end-stage kidney disease (ESKD) or death. STUDY DESIGN: Multicenter prospective cohort study. SETTING & PARTICIPANTS: Cure Glomerulonephropathy (CureGN) will enroll 2,400 children and adults with minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, or IgA nephropathy (including IgA vasculitis) and a first diagnostic kidney biopsy within 5 years. Patients with ESKD and those with secondary causes of glomerular disease are excluded. EXPOSURES: Clinical data, including medical history, medications, family history, and patient-reported outcomes, are obtained, along with a digital archive of kidney biopsy images and blood and urine specimens at study visits aligned with clinical care 1 to 4 times per year. OUTCOMES: Patients are followed up for changes in estimated glomerular filtration rate, disease activity, ESKD, and death and for nonrenal complications of disease and treatment, including infection, malignancy, cardiovascular, and thromboembolic events. ANALYTICAL APPROACH: The study design supports multiple longitudinal analyses leveraging the diverse data domains of CureGN and its ancillary program. At 2,400 patients and an average of 2 years' initial follow-up, CureGN has 80% power to detect an HR of 1.4 to 1.9 for proteinuria remission and a mean difference of 2.1 to 3.0mL/min/1.73m2 in estimated glomerular filtration rate per year. LIMITATIONS: Current follow-up can only detect large differences in ESKD and death outcomes. CONCLUSIONS: Study infrastructure will support a broad range of scientific approaches to identify mechanistically distinct subgroups, identify accurate biomarkers of disease activity and progression, delineate disease-specific treatment targets, and inform future therapeutic trials. CureGN is expected to be among the largest prospective studies of children and adults with glomerular disease, with a broad goal to lessen disease burden and improve outcomes.

LDL Receptor-Related Protein 2 (Megalin) as a Target Antigen in Human Kidney Anti-Brush Border Antibody Disease.

Primary renal tubulointerstitial disease resulting from proximal tubule antigen-specific antibodies and immune complex formation has not been well characterized in humans. We report a cohort of patients with a distinct, underappreciated kidney disease characterized by kidney antibrush border antibodies and renal failure (ABBA disease). We identified ten patients with ABBA disease who had a combination of proximal tubule damage, IgG-positive immune deposits in the tubular basement membrane, and circulating antibodies reactive with normal human kidney proximal tubular brush border. All but one of the patients also had segmental glomerular deposits on renal biopsy specimen. Patients with ABBA disease were elderly and presented with AKI and subnephrotic proteinuria. Serum from all patients but not controls recognized a high molecular weight protein in renal tubular protein extracts that we identified as LDL receptor-related protein 2 (LRP2), also known as megalin, by immunoprecipitation and mass spectrometry. Immunostaining revealed that LRP2 specifically colocalized with IgG in the tubular immune deposits on the ABBA biopsy specimen but not the control specimen analyzed. Finally, ABBA serum samples but not control samples showed reactivity against recombinantly expressed N-terminal LRP2 fragments on Western blots and immunoprecipitated the recombinantly expressed N-terminal region of LRP2. This case series details the clinicopathologic findings of patients with ABBA disease and shows that the antigenic target of these autoantibodies is LRP2. Future studies are needed to determine the disease prevalence, stimulus for ABBA, and optimal treatment.

Compassion cultivation training promotes medical student wellness and enhanced clinical care.

BACKGROUND: Compassionate health care is associated with positive patient outcomes. Educational interventions for medical students that develop compassion may also increase wellness, decrease burnout, and improve provider-patient relationships. Research on compassion training in medical education is needed to determine how students learn and apply these skills. The authors evaluated an elective course for medical students modeled after the Compassion Cultivation Training course developed by the Stanford Center for Compassion and Altruism Research and Education. The elective goals were to strengthen student compassion, kindness, and wellness through compassion training and mindfulness meditation training modeled by a faculty instructor. The research objectives were to understand students' applications and perceptions of this training. METHODS: Over three years, 45 students participated in the elective at the University of Louisville School of Medicine. The course administered a pre/post Kentucky Inventory of Mindfulness Skills that measured observing, describing, acting with awareness, and accepting without judgment. Qualitative analyses of self-reported experiences were used to assess students' perceptions of compassion training and their application of skills learned through the elective. RESULTS: The mindfulness inventory showed significant improvements in observing (t = 3.62, p = 0.005) and accepting without judgment skills (t = 2.87, p = 0.017) for some elective cohorts. Qualitative data indicated that students across all cohorts found the elective rewarding, and they used mindfulness, meditation, and compassion skills broadly outside the course. Students described how the training helped them address major stressors associated with personal, academic, and clinical responsibilities. Students also reported that the skills strengthened interpersonal interactions, including with patients. CONCLUSIONS: These outcomes illuminate students' attitudes toward compassion training and suggest that among receptive students, a brief, student-focused intervention can be enthusiastically received and positively influence students' compassion toward oneself and others. To underscore the importance of interpersonal and cognitive skills such as compassion and mindfulness, faculty should consider purposefully modeling these skills to students. Modeling compassion cultivation and mindfulness skills in the context of patient interactions may address student empathy erosion more directly than stress management training alone. This pilot study shows compassion training could be an attractive, efficient option to address burnout by simultaneously promoting student wellness and enhanced patient interactions.

Urine inositol pentakisphosphate 2-kinase and changes in kidney structure in early diabetic kidney disease in type 1 diabetes.

We examined the association of urine inositol 1,3,4,5,6-pentakisphosphate 2-kinase (IPP2K) with the presence and progression of diabetic kidney disease (DKD) lesions. Urine IPP2K was measured at baseline by quantitative liquid chromatography-mass spectrometry in 215 participants from the Renin-Angiotensin System Study who had type 1 diabetes and were normoalbuminuric and normotensive with normal or increased glomerular filtration rate (GFR). Urine IPP2K was detectable in 166 participants. Participants with IPP2K below the limit of quantification (LOQ) were assigned concentrations of LOQ/√2. All concentrations were then standardized to urine creatinine (Cr) concentration. Kidney morphometric data were available from biopsies at baseline and after 5 yr. Relationships of IPP2K/Cr with morphometric variables were assessed by linear regression after adjustment for age, sex, diabetes duration, hemoglobin A1c, mean arterial pressure, treatment assignment, and, for longitudinal analyses, baseline structure. Baseline mean age was 29.7 yr, mean diabetes duration 11.2 yr, median albumin excretion rate 5.0 µg/min, and mean iohexol GFR 129 ml·min-1·1.73m-2. Higher IPP2K/Cr was associated with higher baseline peripheral glomerular total filtration surface density [Sv(PGBM/glom), tertile 3 vs. tertile 1 ß = 0.527, P = 0.011] and with greater preservation of Sv(PGBM/glom) after 5 yr ( tertile 3 vs. tertile 1 ß = 0.317, P = 0.013). Smaller increases in mesangial fractional volume ( tertile 3 vs. tertile 1 ß = -0.578, P = 0.018) were observed after 5 yr in men with higher urine IPP2K/Cr concentrations. Higher urine IPP2K/Cr is associated with less severe kidney lesions at baseline and with preservation of kidney structure over 5 yr in individuals with type 1 diabetes and no clinical evidence of DKD at baseline.

Poly-ubiquitin profile in Alzheimer disease brain.

Alzheimer disease (AD) is a neurodegenerative disorder characterized by progressive loss of memory, reasoning and other cognitive functions. Pathologically, patients with AD are characterized by deposition of senile plaques (SPs), formed by ß-amyloid (Aß), and neurofibrillary tangles (NTFs) that consist of aggregated hyperphosphorylated tau protein. The accumulation of insoluble protein aggregates in AD brain can be associated with an impairment of degradative systems. This current study investigated if the disturbance of protein polyubiquitination is associated with AD neurodegeneration. By using a novel proteomic approach, we found that 13 brain proteins are increasingly polyubiquitinated in AD human brain compared to age-matched controls. Moreover, the majority of the identified proteins were previously found to be oxidized in our prior proteomics, and these proteins are mainly involved in protein quality control and glucose metabolism. This is the first study showing alteration of the poly-ubiquitin profile in AD brain compared with healthy controls. Understanding the onset of the altered ubiquitin profile in AD brain may contribute to identification of key molecular regulators of cognitive decline. In AD, deficits of the proteolytic system may further exacerbate the accumulation of oxidized/misfolded/polyubiquitinated proteins that are not efficiently degraded and may become harmful to neurons and contribute to AD neuropathology and cognitive decline.

Biomarker enhanced risk prediction for development of AKI after cardiac surgery.

BACKGROUND: Acute kidney injury (AKI) is a common post-cardiac surgery complication and influences patient morbidity and prognosis. This study was designed to identify preoperative candidate urine biomarkers in patients undergoing cardiac surgery. METHODS: A prospective cohort study of adults undergoing cardiac surgery at increased risk for AKI at a single hospital between July 2010 and September 2012 was performed. The primary outcome was the development of AKI, defined as an absolute serum creatinine (SCr) level increase ≥ 0.5 mg/dL or a ≥ 50% relative increase within 72 h of surgery. A secondary outcome was development of AKI defined by Kidney Disease Improving Global Outcomes (KDIGO). Urine collected by voiding within 4 h prior to surgery was used for proteomic analysis and confirmatory enzyme linked immunosorbent assays (ELISAs) studies. Biomarkers were tested for AKI-prediction using Cox and Snell R2, area under the receiver operating curve (AUROC), and percent of corrected classifications. To evaluate the added effect of each candidate biomarker on AKI discrimination, receiver operator characteristic (ROC) curves, integrated discrimination improvement (IDI), and net reclassification improvement (NRI) were calculated. RESULTS: Forty-seven of 755 patients met screening criteria including 15 with AKI. Proteomic analysis identified 29 proteins with a significant ≥2-fold change. Confirmatory ELISA measurements of five candidate markers showed urinary complement factor B (CFB) and histidine rich glycoprotein (HRG) concentrations were significantly increased in patients with AKI. By multivariate analysis, NRI, and IDI the addition of CFB and HRG to the standard clinical assessment significantly improved risk prediction for the primary outcome. Only HRG was a significant predictor in the 21 patients with AKI defined by KDIGO criteria. CONCLUSIONS: Pre-operative urine measurement of CFB or HRG significantly enhanced the current post-surgery AKI risk stratification for more restrictive definition of AKI. HRG, but not CFB or clinical risk stratification, predicted AKI defined by KDIGO. The ability of these biomarkers to predict risk for dialysis-requiring AKI or death could not be reliably assessed in our study due to a small number of patients with either outcome.

Common Elements in Rare Kidney Diseases: Conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference.

Rare kidney diseases encompass at least 150 different conditions, most of which are inherited. Although individual rare kidney diseases raise specific issues, as a group these rare diseases can have overlapping challenges in diagnosis and treatment. These challenges include small numbers of affected patients, unidentified causes of disease, lack of biomarkers for monitoring disease progression, and need for complex care. To address common clinical and patient issues among rare kidney diseases, the KDIGO Controversies Conference entitled, Common Elements in Rare Kidney Diseases, brought together a panel of multidisciplinary clinical providers and patient advocates to address five central issues for rare kidney diseases. These issues encompassed diagnostic challenges, management of kidney functional decline and progression of chronic kidney disease, challenges in clinical study design, translation of advances in research to clinical care, and provision of practical and integrated patient support. Thus, by a process of consensus, guidance for addressing these challenges was developed and is presented here.

Thrombospondin type-1 domain-containing 7A in idiopathic membranous nephropathy.

BACKGROUND: Idiopathic membranous nephropathy is an autoimmune disease. In approximately 70% of patients, it is associated with autoantibodies against the phospholipase A2 receptor 1 (PLA2R1). Antigenic targets in the remaining patients are unknown. METHODS: Using Western blotting, we screened serum samples from patients with idiopathic membranous nephropathy, patients with other glomerular diseases, and healthy controls for antibodies against human native glomerular proteins. We partially purified a putative new antigen, identified this protein by means of mass spectrometry of digested peptides, and validated the results by analysis of recombinant protein expression, immunoprecipitation, and immunohistochemical analysis. RESULTS: Serum samples from 6 of 44 patients in a European cohort and 9 of 110 patients in a Boston cohort with anti-PLA2R1-negative idiopathic membranous nephropathy recognized a glomerular protein that was 250 kD in size. None of the serum samples from the 74 patients with idiopathic membranous nephropathy who were seropositive for anti-PLA2R1 antibodies, from the 76 patients with other glomerular diseases, and from the 44 healthy controls reacted against this antigen. Although this newly identified antigen is clearly different from PLA2R1, it shares some biochemical features, such as N-glycosylation, membranous location, and reactivity with serum only under nonreducing conditions. Mass spectrometry identified this antigen as thrombospondin type-1 domain-containing 7A (THSD7A). All reactive serum samples recognized recombinant THSD7A and immunoprecipitated THSD7A from glomerular lysates. Moreover, immunohistochemical analyses of biopsy samples from patients revealed localization of THSD7A to podocytes, and IgG eluted from one of these samples was specific for THSD7A. CONCLUSIONS: In our cohort, 15 of 154 patients with idiopathic membranous nephropathy had circulating autoantibodies to THSD7A but not to PLA2R1, a finding that suggests a distinct subgroup of patients with this condition. (Funded by the French National Center for Scientific Research and others.).