Predictors of mortality in hospitalised patients with COVID-19: a 1-year case-control study.

BACKGROUND: A paucity of predictive models assessing risk factors for COVID-19 mortality that extend beyond age and gender in Latino population is evident in the current academic literature. OBJECTIVES: To determine the associated factors with mortality, in addition to age and sex during the first year of the pandemic. DESIGN: A case-control study with retrospective revision of clinical and paraclinical variables by systematic revision of clinical records was conducted. Multiple imputations by chained equation were implemented to account for missing variables. Classification and regression trees (CART) were estimated to evaluate the interaction of associated factors on admission and their role in predicting mortality during hospitalisation. No intervention was performed. SETTING: High-complexity centre above 2640 m above sea level (masl) in Colombia. PARTICIPANTS: A population sample of 564 patients admitted to the hospital with confirmed COVID-19 by PCR. Deceased patients (n=282) and a control group (n=282), matched by age, sex and month of admission, were included. MAIN OUTCOME MEASURE: Mortality during hospitalisation. MAIN RESULTS: After the imputation of datasets, CART analysis estimated 11 clinical profiles based on respiratory distress, haemoglobin, lactate dehydrogenase, partial pressure of oxygen to inspired partial pressure of oxygen ratio, chronic kidney disease, ferritin, creatinine and leucocytes on admission. The accuracy model for prediction was 80.4% (95% CI 71.8% to 87.3%), with an area under the curve of 78.8% (95% CI 69.63% to 87.93%). CONCLUSIONS: This study discloses new interactions between clinical and paraclinical features beyond age and sex influencing mortality in COVID-19 patients. Furthermore, the predictive model could offer new clues for the personalised management of this condition in clinical settings.

Metabolic fingerprinting of systemic sclerosis: a systematic review.

Introduction: Systemic sclerosis (SSc) is a chronic autoimmune disease, marked by an unpredictable course, high morbidity, and increased mortality risk that occurs especially in the diffuse and rapidly progressive forms of the disease, characterized by fibrosis of the skin and internal organs and endothelial dysfunction. Recent studies suggest that the identification of altered metabolic pathways may play a key role in understanding the pathophysiology of the disease. Therefore, metabolomics might be pivotal in a better understanding of these pathogenic mechanisms. Methods: Through a systematic review of the literature following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Guidelines (PRISMA), searches were done in the PubMed, EMBASE, Web of Science, and Scopus databases from 2000 to September 2022. Three researchers independently reviewed the literature and extracted the data based on predefined inclusion and exclusion criteria. Results: Of the screened studies, 26 fulfilled the inclusion criteria. A total of 151 metabolites were differentially distributed between SSc patients and healthy controls (HC). The main deregulated metabolites were those derived from amino acids, specifically homocysteine (Hcy), proline, alpha-N-phenylacetyl-L-glutamine, glutamine, asymmetric dimethylarginine (ADMA), citrulline and ornithine, kynurenine (Kyn), and tryptophan (Trp), as well as acylcarnitines associated with long-chain fatty acids and tricarboxylic acids such as citrate and succinate. Additionally, differences in metabolic profiling between SSc subtypes were identified. The diffuse cutaneous systemic sclerosis (dcSSc) subtype showed upregulated amino acid-related pathways involved in fibrosis, endothelial dysfunction, and gut dysbiosis. Lastly, potential biomarkers were evaluated for the diagnosis of SSc, the identification of the dcSSc subtype, pulmonary arterial hypertension, and interstitial lung disease. These potential biomarkers are within amino acids, nucleotides, carboxylic acids, and carbohydrate metabolism. Discussion: The altered metabolite mechanisms identified in this study mostly point to perturbations in amino acid-related pathways, fatty acid beta-oxidation, and in the tricarboxylic acid cycle, possibly associated with inflammation, vascular damage, fibrosis, and gut dysbiosis. Further studies in targeted metabolomics are required to evaluate potential biomarkers for diagnosis, prognosis, and treatment response.

Safety and efficacy of convalescent plasma for severe COVID-19: a randomized, single blinded, parallel, controlled clinical study.

BACKGROUND: Convalescent plasma (CP) has been widely used to treat COVID-19 and is under study. However, the variability in the current clinical trials has averted its wide use in the current pandemic. We aimed to evaluate the safety and efficacy of CP in severe coronavirus disease 2019 (COVID-19) in the early stages of the disease. METHODS: A randomized controlled clinical study was conducted on 101 patients admitted to the hospital with confirmed severe COVID-19. Most participants had less than 14 days from symptoms onset and less than seven days from hospitalization. Fifty patients were assigned to receive CP plus standard therapy (ST), and 51 were assigned to receive ST alone. Participants in the CP arm received two doses of 250 mL each, transfused 24 h apart. All transfused plasma was obtained from "super donors" that fulfilled the following criteria: titers of anti-SARS-CoV-2 S1 IgG ≥ 1:3200 and IgA ≥ 1:800 antibodies. The effect of transfused anti-IFN antibodies and the SARS-CoV-2 variants at the entry of the study on the overall CP efficacy was evaluated. The primary outcomes were the reduction in viral load and the increase in IgG and IgA antibodies at 28 days of follow-up. The per-protocol analysis included 91 patients. RESULTS: An early but transient increase in IgG anti-S1-SARS-CoV-2 antibody levels at day 4 post-transfusion was observed (Estimated difference [ED], - 1.36; 95% CI, - 2.33 to - 0.39; P = 0.04). However, CP was not associated with viral load reduction in any of the points evaluated. Analysis of secondary outcomes revealed that those patients in the CP arm disclosed a shorter time to discharge (ED adjusted for mortality, 3.1 days; 95% CI, 0.20 to 5.94; P = 0.0361) or a reduction of 2 points on the WHO scale when compared with the ST group (HR adjusted for mortality, 1.6; 95% CI, 1.03 to 2.5; P = 0.0376). There were no benefits from CP on the rates of intensive care unit admission (HR, 0.82; 95% CI, 0.35 to 1.9; P = 0.6399), mechanical ventilation (HR, 0.66; 95% CI, 0.25 to 1.7; P = 0.4039), or mortality (HR, 3.2; 95% CI, 0.64 to 16; P = 0.1584). Anti-IFN antibodies and SARS-CoV-2 variants did not influence these results. CONCLUSION: CP was not associated with viral load reduction, despite the early increase in IgG anti-SARS-CoV-2 antibodies. However, CP is safe and could be a therapeutic option to reduce the hospital length of stay. Trial registration NCT04332835.

Autoimmunity is a hallmark of post-COVID syndrome.

Autoimmunity has emerged as a characteristic of the post-COVID syndrome (PCS), which may be related to sex. In order to further investigate the relationship between SARS-CoV-2 and autoimmunity in PCS, a clinical and serological assessment on 100 patients was done. Serum antibody profiles against self-antigens and infectious agents were evaluated by an antigen array chip for 116 IgG and 104 IgM antibodies. Thirty pre-pandemic healthy individuals were included as a control group. The median age of patients was 49 years (IQR: 37.8 to 55.3). There were 47 males. The median post-COVID time was 219 (IQR: 143 to 258) days. Latent autoimmunity and polyautoimmunity were found in 83% and 62% of patients, respectively. Three patients developed an overt autoimmune disease. IgG antibodies against IL-2, CD8B, and thyroglobulin were found in more than 10% of the patients. Other IgG autoantibodies, such as anti-interferons, were positive in 5-10% of patients. Anti-SARS-CoV-2 IgG antibodies were found in > 85% of patients and were positively correlated with autoantibodies, age, and body mass index (BMI). Few autoantibodies were influenced by age and BMI. There was no effect of gender on the over- or under-expression of autoantibodies. IgG anti-IFN-λ antibodies were associated with the persistence of respiratory symptoms. In summary, autoimmunity is characteristic of PCS, and latent autoimmunity correlates with humoral response to SARS-CoV-2.

Persistent Autoimmune Activation and Proinflammatory State in Post-Coronavirus Disease 2019 Syndrome.

BACKGROUND: The immunopathological pathways enabling post-coronavirus disease 2019 (COVID-19) syndrome (PCS) development are not entirely known. We underwent a longitudinal analysis of patients with COVID-19 who developed PCS aiming to evaluate the autoimmune and immunological status associated with this condition. METHODS: Thirty-three patients were included for longitudinal clinical and autoantibody analyses, 12 of whom were assessed for cytokines and lymphocyte populations. Patients were followed for 7-11 months after acute COVID-19. Autoimmune profile and immunological statuses were evaluated mainly by enzyme-linked-immunosorbent assays and flow cytometry. RESULTS: Latent autoimmunity and overt autoimmunity persisted over time. A proinflammatory state was observed in patients with PCS characterized by up-regulated interferon-α, tumor necrosis factor-α, granulocyte colony-stimulating factor (G-CSF), interleukin (IL)-17A, IL-6, IL-1ß, and IL-13, whereas interferon-γ-induced protein 10 (IP-10) was decreased. In addition, PCS was characterized by increased levels of Th9, CD8+ effector T cells, naive B cells, and CD4+ effector memory T cells. Total levels of immunoglobulin G S1-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies remained elevated over time. CONCLUSIONS: The clinical manifestations of PCS are associated with the persistence of a proinflammatory and effector phenotype induced by SARS-CoV-2 infection. This long-term persistent immune activation may contribute to the development of latent and overt autoimmunity. Results suggest the need to evaluate the role of immunomodulation in the treatment of PCS.

New insights into the taxonomy of autoimmune diseases based on polyautoimmunity.

OBJECTIVE: The clinical coexistence of two or more autoimmune diseases (ADs) fulfilling classification criteria is termed "overt polyautoimmunity" (PolyA), whereas the presence of autoantibodies unrelated to an index AD, without clinical criteria fulfillment, is known as "latent PolyA". We aimed to explore a new taxonomy of ADs based on PolyA. METHODS: In a cross-sectional study of 292 subjects, we evaluated the presence of PolyA in 146, 45, 29, 17, and 17 patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), autoimmune thyroid disease (AITD) and systemic sclerosis (SSc), respectively, and 38 healthy controls. Clinical assessment, autoantibody profile (by autoantigen array chip), lymphocytes immunophenotype and cytokine profile (by flow cytometry) were evaluated simultaneously. A mixed cluster methodology was used to classify ADs. RESULTS: Latent PolyA was more frequent than overt PolyA, ranging from 69.9% in RA to 100% in SSc. Nevertheless, both latent and overt PolyA clustered together. Over-expressed IgG autoantibodies were found to be hallmarks for the identification of index ADs. The combination of autoantibodies allowed high accuracy in the classification of ADs. Three well-defined clusters based on PolyA were observed with distinctive clinical and immunological phenotypes. CONCLUSIONS: This proof-of-concept study indicates that ADs can be classified according to PolyA. PolyA should be considered in all studies dealing with ADs, including epidemiological, genetic, and clinical trials.

Post-COVID syndrome. A case series and comprehensive review.

The existence of a variety of symptoms with a duration beyond the acute phase of COVID-19, is referred to as post-COVID syndrome (PCS). We aimed to report a series of patients with PCS attending a Post-COVID Unit and offer a comprehensive review on the topic. Adult patients with previously confirmed SARS-CoV-2 infection and PCS were systematically assessed through a semi-structured and validated survey. Total IgG, IgA and IgM serum antibodies to SARS-CoV-2 were evaluated by an electrochemiluminescence immunoassay. A systematic review of the literature and meta-analysis were conducted, following PRISMA guidelines. Univariate and multivariate methods were used to analyze data. Out of a total of 100 consecutive patients, 53 were women, the median of age was 49 years (IQR: 37.8-55.3), the median of post-COVID time after the first symptoms was 219 days (IQR: 143-258), and 65 patients were hospitalized during acute COVID-19. Musculoskeletal, digestive (i.e., diarrhea) and neurological symptoms including depression (by Zung scale) were the most frequent observed in PCS patients. A previous hospitalization was not associated with PCS manifestation. Arthralgia and diarrhea persisted in more than 40% of PCS patients. The median of anti-SARS-CoV-2 antibodies was 866.2 U/mL (IQR: 238.2-1681). Despite this variability, 98 patients were seropositive. Based on autonomic symptoms (by COMPASS 31) two clusters were obtained with different clinical characteristics. Levels of anti-SARS-CoV-2 antibodies were not different between clusters. A total of 40 articles (11,196 patients) were included in the meta-analysis. Fatigue/muscle weakness, dyspnea, pain and discomfort, anxiety/depression and impaired concentration were presented in more than 20% of patients reported. In conclusion, PCS is mainly characterized by musculoskeletal, pulmonary, digestive and neurological involvement including depression. PCS is independent of severity of acute illness and humoral response. Long-term antibody responses to SARS-CoV-2 infection and a high inter-individual variability were confirmed. Future studies should evaluate the mechanisms by which SARS-CoV-2 may cause PCS and the best therapeutic options.

Latent rheumatic, thyroid and phospholipid autoimmunity in hospitalized patients with COVID-19.

Autoimmune responses mediated by autoantibodies have been observed in SARS-CoV-2 infection. Herein, we evaluate the presence of rheumatic, thyroid and phospholipid autoantibodies in sera samples from 120 adult hospitalized patients with COVID-19 in comparison to pre-pandemic samples from 100 healthy individuals. In addition, to estimate the frequency of these autoantibodies in COVID-19, a meta-analysis of selected articles was conducted. Hospitalized patients with COVID-19 had latent autoimmunity characterized by a high frequency of anti-thyroid peroxidase antibodies, rheumatoid factor (RF), anti-cyclic citrullinated peptide third generation antibodies, antinuclear antibodies (ANAs), IgM anti-ß2-glycoprotein I (ß2GP1) and IgM anti-cardiolipin antibodies. The meta-analysis confirmed our results, with RF and ANAs being the most common autoantibodies. In addition, cluster analysis revealed that those patients with high frequency of RF, IgM anti-ß2GP1 antibodies and ANAs had a longer hospital stay, required more vasopressors during hospitalization, and were more likely to develop critical disease. These data suggest that latent autoimmunity influences the severity of COVID-19, and support further post-COVID studies in order to evaluate the development of overt autoimmunity.

COVID-19 convalescent plasma composition and immunological effects in severe patients.

Convalescent plasma (CP) has emerged as a treatment for COVID-19. However, the composition and mechanism of action are not fully known. Therefore, we undertook a two-phase controlled study in which, first the immunological and metabolomic status of recovered and severe patients were evaluated. Secondly, the 28-day effect of CP on the immune response in severe patients was assessed. Nineteen recovered COVID-19 patients, 18 hospitalized patients with severe disease, and 16 pre-pandemic controls were included. Patients with severe disease were treated with CP transfusion and standard therapy (i.e., plasma recipients, n = 9) or standard therapy alone (n = 9). Clinical and biological assessments were done on day 0 and during follow-up on days 4, 7, 14, and 28. Clinical parameters, viral load, total immunoglobulin (Ig) G and IgA anti-S1-SARS-CoV-2 antibodies, neutralizing antibodies (NAbs), autoantibodies, cytokines, T and B cells, and metabolomic and lipidomic profiles were examined. Total IgG and IgA anti-S1-SARS-CoV-2 antibodies were key factors for CP selection and correlated with NAbs. In severe COVID-19 patients, mostly interleukin (IL)-6 (P = <0.0001), IL-10 (P = <0.0001), IP-10 (P = <0.0001), fatty acyls and glycerophospholipids were higher than in recovered patients. Latent autoimmunity and anti-IFN-α antibodies were observed in both recovered and severe patients. COVID-19 CP induced an early but transient cytokine profile modification and increases IgG anti-S1-SARS-CoV-2 antibodies. At day 28 post-transfusion, a decrease in activated, effector and effector memory CD4+ (P < 0.05) and activated and effector CD8+ (P < 0.01) T cells and naïve B cells (P = 0.001), and an increase in non-classical memory B cells (P=<0.0001) and central memory CD4+ T cells (P = 0.0252) were observed. Moreover, IL-6/IFN-γ (P = 0.0089) and IL-6/IL-10 (P = 0.0180) ratios decreased in plasma recipients compared to those who received standard therapy alone. These results may have therapeutic implications and justify further post-COVID-19 studies.

Neutrophil extracellular traps in autoimmune diseases / Trampas extracelulares de neutrófilos en enfermedades autoinmunes

ABSTRACT Neutrophils play an important role in immune defence against several pathogens. These cells actively participate in the innate immune response through different functions, such as chemotaxis, phagocytosis, oxidative burst and degranulation, which have been widely studied. However, in the last few years, a new function has been described; activated neutrophils are able to release web-like chromatin structures known as neutrophil extracellular traps (NETs). These structures formed by DNA, histones, and proteins, immobilize and kill microorganisms. Disruption in NET formation is associated with the pathophysiology of several disorders, including the autoimmune diseases. NETs are an important source of the autoantigens involved in the production of autoantibodies and maintenance of the inflammatory milieu. This review provides a summary of the contribution of NETs to the pathogenesis of anti-neutrophil cytoplasmic antibodies-associated vasculitis, systemic lupus erythematosus, and rheumatoid arthritis. The preliminary findings on NETs components in Sjögren.'s syndrome will also be described.

RESUMEN Los neutrófilos juegan un papel muy importante en la defensa inmune contra diferentes patógenos. Estas células participan activamente en la respuesta inmune innata a través de diferentes funciones como quimiotaxis, fagocitosis, estallido oxidativo y degranulación, las cuales han sido estudiadas ampliamente. Sin embargo, en los últimos años se ha descrito una nueva función; los neutrófilos activados son capaces de liberar redes de cromatina llamadas trampas extracelulares de neutrófilos (NETs). Estas estructuras están formadas por ADN, histonas y proteínas capaces de inmovilizar y matar microorganismos. Alteraciones en la formación de estas NETs están asociadas con la fisiopatología de varios trastornos, incluyendo las enfermedades autoinmunes (EAI). Las NETs son consideradas una fuente de autoantígenos que ayudan a la producción de autoanticuerpos y al mantenimiento de un ambiente inflamatorio. Esta revisión resume la contribución de las NETs a la patogénesis de vasculitis asociada a anticuerpos contra el citoplasma de los neutrófilos, lupus eritematoso sistémico y artritis reumatoide. Adicionalmente, se describirán los resultados preliminares de la detección de componentes de las NETs en pacientes con síndrome de Sjögren.

Latent autoimmune thyroid disease.

OBJECTIVE: To determine the prevalence of thyroid autoantibodies and the associated factors in euthyroid subjects. METHODS: 300 euthyroid subjects, chosen by stratified sampling from an inception cohort of 1335 individuals, were included. Thyroid function was evaluated by measuring the serum levels of TSH (0.3-4.5 µIU/mL) and FT4 (5.2-12.7µg/dL). Anti-peroxidase (TPOAbs), anti-thyroglobulin (TgAbs), and anti-TSH receptor (TrAbs) antibodies were evaluated with 23 additional autoantibodies as well as vitamin D (VitD) levels. The analysis included sociodemographic, clinical, and environmental characteristics. Data were analyzed by bivariate and multivariate tests. RESULTS: Thyroid autoimmunity was observed in 15.3% of the subjects (TPOAbs 11.3% and TgAbs 2.0%). In six individuals, both autoantibodies were positive. TrAbs were not detected in any individual. Familial thyroid disease (ߠ​= â€‹3.4, 95% CI: 1.2-9.5, P â€‹= â€‹0.021), the presence of other autoimmune diseases (ߠ​= â€‹10.8, 95% CI: 1.6-72.9, P â€‹= â€‹0.014) VitD insufficiency (P â€‹= â€‹0.030), never smoke (ߠ​= â€‹6.9, 95% CI: 1.6-30.4, P â€‹= â€‹0.010), drinking more than 4 cups of coffee (ߠ​= â€‹3.8, 95% CI: 1.1-13.1, P â€‹= â€‹0.036), and a higher number of years exposed to wood smoke (P â€‹= â€‹0.04) were associated with thyroid autoimmunity. In the case of TPOAbs, familial thyroid disease (ߠ​= â€‹4.9, 95% CI: 1.7-14.0, P â€‹= â€‹0.003), never smoke (ߠ​= â€‹5.7, 95% CI: 1.4-21.0, P â€‹= â€‹0.002), and drinking more than 4 cups of coffee (ߠ​= â€‹3.6, 95% CI: 1.1-13.1, P â€‹= â€‹0.047) were associated with their positivity. In addition, the presence of anti-SS-A/Ro52 (ߠ​= â€‹36.7, 95% CI: 2.5-549.9, P â€‹= â€‹0.009) and anti-Ku antibodies (ߠ​= â€‹10.2, 95% CI: 1.1-100.7, P â€‹= â€‹0.046) was also associated with TPOAbs. The presence of African ancestry (ߠ​= â€‹10.5, 95% CI: 1.7-63.2, P â€‹= â€‹0.01), anti-SS-A/Ro52 (ߠ​= â€‹15.8, 95% CI: 1.2-198.6, P â€‹= â€‹0.03), and anti-CENP-B antibodies (ߠ​= â€‹31.2, 95% CI: 1.8-565.9 â€‹P â€‹= â€‹0.02) were associated with TgAbs. CONCLUSION: Latent thyroid autoimmunity is not rare. Environmental, genetic, and immunological factors as well as ancestry are associated risk factors. These results would facilitate the implementation of screening strategies in order to provide timely diagnosis and treatment.

Autoinflammatory and autoimmune conditions at the crossroad of COVID-19.

Coronavirus disease 2019 (COVID-19) has been categorized as evolving in overlapping phases. First, there is a viral phase that may well be asymptomatic or mild in the majority, perhaps 80% of patients. The pathophysiological mechanisms resulting in minimal disease in this initial phase are not well known. In the remaining 20% of cases, the disease may become severe and/or critical. In most patients of this latter group, there is a phase characterized by the hyperresponsiveness of the immune system. A third phase corresponds to a state of hypercoagulability. Finally, in the fourth stage organ injury and failure occur. Appearance of autoinflammatory/autoimmune phenomena in patients with COVID-19 calls attention for the development of new strategies for the management of life-threatening conditions in critically ill patients. Antiphospholipid syndrome, autoimmune cytopenia, Guillain-Barré syndrome and Kawasaki disease have each been reported in patients with COVID-19. Here we present a scoping review of the relevant immunological findings in COVID-19 as well as the current reports about autoinflammatory/autoimmune conditions associated with the disease. These observations have crucial therapeutic implications since immunomodulatory drugs are at present the most likely best candidates for COVID-19 therapy. Clinicians should be aware of these conditions in patients with COVID-19, and these observations should be considered in the current development of vaccines.

Convalescent plasma in Covid-19: Possible mechanisms of action.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible of the coronavirus disease 2019 (COVID-19) pandemic. Therapeutic options including antimalarials, antivirals, and vaccines are under study. Meanwhile the current pandemic has called attention over old therapeutic tools to treat infectious diseases. Convalescent plasma (CP) constitutes the first option in the current situation, since it has been successfully used in other coronaviruses outbreaks. Herein, we discuss the possible mechanisms of action of CP and their repercussion in COVID-19 pathogenesis, including direct neutralization of the virus, control of an overactive immune system (i.e., cytokine storm, Th1/Th17 ratio, complement activation) and immunomodulation of a hypercoagulable state. All these benefits of CP are expected to be better achieved if used in non-critically hospitalized patients, in the hope of reducing morbidity and mortality.

Ebola virus disease: An emerging and re-emerging viral threat.

The genus Ebolavirus from the family Filoviridae is composed of five species including Sudan ebolavirus, Reston ebolavirus, Bundibugyo ebolavirus, Taï Forest ebolavirus, and Ebola virus (previously known as Zaire ebolavirus). These viruses have a large non-segmented, negative-strand RNA of approximately 19 kb that encodes for glycoproteins (i.e., GP, sGP, ssGP), nucleoproteins, virion proteins (i.e., VP 24, 30,40) and an RNA dependent RNA polymerase. These viruses have become a global health concern because of mortality, their rapid dissemination, new outbreaks in West-Africa, and the emergence of a new condition known as "Post-Ebola virus disease syndrome" that resembles inflammatory and autoimmune conditions such as rheumatoid arthritis, systemic lupus erythematosus and spondyloarthritis with uveitis. However, there are many gaps in the understanding of the mechanisms that may induce the development of such autoimmune-like syndromes. Some of these mechanisms may include a high formation of neutrophil extracellular traps, an uncontrolled "cytokine storm", and the possible formation of auto-antibodies. The likely appearance of autoimmune phenomena in Ebola survivors suppose a new challenge in the management and control of this disease and opens a new field of research in a special subgroup of patients. Herein, the molecular biology, pathogenesis, clinical manifestations, and treatment of Ebola virus disease are reviewed and some strategies for control of disease are discussed.

Bystander activation and autoimmunity.

The interaction over time of genetic, epigenetic and environmental factors (i.e., autoimmune ecology) increases or decreases the liability an individual would have to develop an autoimmune disease (AD) depending on the misbalance between risk and protective effects. Pathogens have been the most common antecedent events studied, but multiple other environmental factors including xenobiotic chemicals, drugs, vaccines, and nutritional factors have been implicated into the development of ADs. Three main mechanisms have been offered to explain the development of autoimmunity: molecular mimicry, epitope spreading, and bystander activation. The latter is characterized by auto-reactive B and T cells that undergo activation in an antigen-independent manner, influencing the development and course of autoimmunity. Activation occurs due to a combination of an inflammatory milieu, co-signaling ligands, and interactions with neighboring cells. In this review, we will discuss the studies performed seeking to define the role of bystander activation in systemic and organ-specific ADs. In all cases, we are cognizant of individual differences between hosts and the variable latency time for clinical expression of disease, all of which have made our understanding of the etiology of loss of immune tolerance difficult and enigmatic.