Abstract: Anti-MDA5 (Melanoma differentiation-associated protein-5) positive dermatomyositis (MDA5

Abstract: Intron-containing RNA expressed from the HIV-1 provirus activates type 1 interferon in primary human blood cells, including CD4

Abstract: Abstract As a RIG-I-like receptor, MDA5 plays a critical role in antiviral innate immunity by acting as a cytoplasmic double-stranded RNA sensor capable of initiating type I interferon pathways. Here, we show that RNF144B specifically interacts with MDA5 and promotes K27/K33-linked polyubiquitination of MDA5 at lysine 23 and lysine 43, which promotes autophagic degradation of MDA5 by p62. Rnf144b deficiency greatly promotes IFN production and inhibits EMCV replication in vivo. Importantly, Rnf144b −/− mice has a significantly higher overall survival rate than wild-type mice upon EMCV infection. Collectively, our results identify RNF144B as a negative regulator of innate antiviral response by targeting CARDs of MDA5 and mediating autophagic degradation of MDA5.

Abstract: Evidence has accumulated to demonstrate that intestinal microbiome can inhibit viral infection. However, our knowledge of the signaling pathways and identity of specific commensal microbes that mediate the antiviral response is limited. Zebrafish have emerged as a powerful animal model for study of vertebrate-microbiota interactions. Here, a rhabdoviral infection model in zebrafish allows us to investigate the modes of action of microbiome-mediated antiviral effect. We observed that oral antibiotics-treated and germ-free zebrafish exhibited greater spring viremia of carp virus (SVCV) infection. Mechanistically, depletion of the intestinal microbiome alters TLR2-Myd88 signaling and blunts neutrophil response and type I interferon (IFN) antiviral innate immunity. Through 16S rRNA sequencing of the intestinal contents from control and antibiotic(s)-treated fish, we identified a single commensal bacterial species, Cetobacterium somerae, that can restore the TLR2- and neutrophil-dependent type I IFN response to restrict SVCV infection in gnotobiotic zebrafish. Furthermore, we found that C. somerae exopolysaccharides (CsEPS) was the effector molecule that engaged TLR2 to mediate the type I IFN-dependent antiviral function. Together, our results suggest a conserved role of intestinal microbiome in regulating type I IFN antiviral response among vertebrates and reveal that the intestinal microbiome inhibits viral infection through a CsEPS-TLR2-type I IFN signaling axis in zebrafish.

Abstract: Anti-melanoma differentiation-associated gene 5-positive (anti-MDA5) dermatomyositis (DM) is a rare autoimmune disease associated with rapidly-progressive interstitial lung disease (RP-ILD.) The reported morbidity and 6-month mortality remains high from 33-66% with RP-ILD most often developing within three months of diagnosis. Most cases require aggressive immunosuppression with combination therapy. Asymptomatic or slowly progressive cases of anti-MDA5 ILD are not well described in the literature. We report three cases of Latino patients with asymptomatic or slowly progressive anti-MDA5 ILD. Case 1: A 56-year-old woman from Honduras with known diagnosis of anti-MDA5 dermatomyositis presented for erythroderma. She denied respiratory symptoms. Computed tomography (CT) chest showed multifocal patchy areas of scattered groundglass opacities throughout all lobes of the lungs, predominately in a subpleural distribution within the lower lobes. Pulmonary function testing (PFTs) showed mild-to-moderate restriction. She was treated with mycophenolate mofetil monotherapy for her skin manifestations. At 18 months follow-up, she denied respiratory symptoms, and PFTs were normal. An 80-year-old man from Cuba was seen in pulmonary clinic to establish care. He was diagnosed with pulmonary fibrosis 11 years earlier with positive anti-MDA5. He denied respiratory symptoms. PFTs showed moderate obstruction and mild to moderate restriction. CT chest showed reduced lung volumes and findings compatible with usual interstitial pneumonia. He was started on nintedanib. Fifteen months following the initial visit, his PFTs remained stable. Follow-up CT chest showed stable pulmonary fibrosis. At all subsequent visits, he reported stability of his respiratory status and was maintained on nintedanib. Thirteen years after his initial ILD diagnosis, he was diagnosed with pancreatic adenocarcinoma. A 70-year-old woman from Peru presented to pulmonary clinic with cough for two months. She also reported pain in several metacarpophalangeal joints. She denied dyspnea. Rheumatologic serologies revealed positive anti-MDA5. PFTs were normal. Her cough was treated with cough suppressants and resolved. At a subsequent visit 8 months after presentation, she denied respiratory symptoms, and her joint pain remained mild. Given her lack of respiratory symptoms and normal PFTs, she was not initiated on ILD-specific treatment. While anti-MDA5 ILD is certainly associated with RP-ILD, clinicians should maintain awareness that there may be cases of asymptomatic or slowly progressive ILD as well.

Abstract: Anti-MDA5 dermatomyositis is associated with an increased risk of developing rapidly progressive interstitial lung disease with a high mortality. We describe FDG PET/CT findings in a case of rapidly progressive noninfectious interstitial lung disease associated with anti-MDA5 dermatomyositis. The lung disease showed bilateral diffuse ground-glass opacities with diffuse heterogeneous FDG activity predominantly in middle and lower zones, mimicking infectious pneumonia. Familiarity with the imaging features of this rapidly progressive noninfectious interstitial lung disease can help to suggest the diagnosis and guide appropriate management.

Abstract: The RIG-I-like receptors (RLRs), comprising retinoic acid-inducible gene I (RIG-I), melanoma differentiation-associated gene 5 (MDA5), and laboratory of genetics and physiology 2 (LGP2), are pattern recognition receptors belonging to the DExD/H-box RNA helicase family of proteins. RLRs detect viral RNAs in the cytoplasm and respond by initiating a robust antiviral response that up-regulates interferon and cytokine production. RIG-I and MDA5 complement each other by recognizing different RNA features, and LGP2 regulates their activation. RIG-I's multilayered RNA recognition and proofreading mechanisms ensure accurate viral RNA detection while averting harmful responses to host RNAs. RIG-I's C-terminal domain targets 5'-triphosphate double-stranded RNA (dsRNA) blunt ends, while an intrinsic gating mechanism prevents the helicase domains from non-specifically engaging with host RNAs. The ATPase and RNA translocation activity of RIG-I adds another layer of selectivity by minimizing the lifetime of RIG-I on non-specific RNAs, preventing off-target activation. The versatility of RIG-I's ATPase function also amplifies downstream signaling by enhancing the signaling domain (CARDs) exposure on 5'-triphosphate dsRNA and promoting oligomerization. In this review, we offer an in-depth understanding of the mechanisms RIG-I uses to facilitate viral RNA sensing and regulate downstream activation of the immune system.

Abstract: Abstract Previous studies through targeted mutagenesis of K-D-K-E motif have demonstrated that 2′-O-MTase activity is essential for efficient viral replication and immune evasion. However, the K-D-K-E catalytic motif of 2′-O-MTase is highly conserved across numerous viruses, including flaviviruses, vaccinia viruses, coronaviruses, and extends even to mammals. Here, we observed a stronger 2′-O-MTase activity in SARS-CoV-2 compared to SARS-CoV, despite the presence of a consistently active catalytic center. We further identified critical residues (Leu-36, Asn-138 and Ile-153) which served as determinants of discrepancy in 2′-O-MTase activity between SARS-CoV-2 and SARS-CoV. These residues significantly enhanced the RNA binding affinity of 2′-O-MTase and boosted its versatility toward RNA substrates. Of interest, a triple substitution (Leu 36 → Ile 36 , Asn 138 → His 138 , Ile 153 → Leu 153 , from SARS-CoV-2 to SARS-CoV) within nsp16 resulted in a proportional reduction in viral 2′-O-methylation and impaired viral replication. Furthermore, it led to a significant upregulation of type I interferon (IFN-I) and proinflammatory cytokines both in vitro and vivo , relying on the cooperative sensing of melanoma differentiation-associated protein 5 (MDA5) and laboratory of genetics and physiology 2 (LGP2). In conclusion, our findings demonstrated that alterations in residues other than K-D-K-E of 2′-O-MTase may affect viral replication and subsequently influence pathogenesis. Monitoring changes in nsp16 residues is crucial as it may aid in identifying and assessing future alteration in viral pathogenicity resulting from natural mutations occurring in nsp16.

Abstract: The posttranslational modification (PTM) of innate immune sensor proteins by ubiquitin or ubiquitin-like proteins is crucial for regulating antiviral host responses. The cytoplasmic dsRNA receptor melanoma differentiation-associated protein 5 (MDA5) undergoes several PTMs including ISGylation within its first caspase activation and recruitment domain (CARD), which promotes MDA5 signaling. However, the relevance of MDA5 ISGylation for antiviral immunity in an infected organism has been elusive. Here, we generated knock-in mice (MDA5K23R/K43R) in which the two major ISGylation sites, K23 and K43, in MDA5 were mutated. Primary cells derived from MDA5K23R/K43R mice exhibited abrogated endogenous MDA5 ISGylation and an impaired ability of MDA5 to form oligomeric assemblies leading to blunted cytokine responses to MDA5 RNA-agonist stimulation or infection with encephalomyocarditis virus (EMCV) or West Nile virus. Phenocopying MDA5-/- mice, the MDA5K23R/K43R mice infected with EMCV displayed increased mortality, elevated viral titers, and an ablated induction of cytokines and chemokines compared to WT mice. Molecular studies identified human HERC5 (and its functional murine homolog HERC6) as the primary E3 ligases responsible for MDA5 ISGylation and activation. Taken together, these findings establish the importance of CARD ISGylation for MDA5-mediated RNA virus restriction, promoting potential avenues for immunomodulatory drug design for antiviral or anti-inflammatory applications.

Abstract: Innate immune responses are induced after viral infections, being these responses essential to establish an antiviral response in the host. The RIG-I-like receptors (RLRs), RIG-I and MDA5 are pivotal for virus detection by recognizing viral RNAs in the cytoplasm of infected cells, initiating these responses. However, since excessive responses can have a negative effect on the host, regulatory feedback mechanisms are needed. In this work, we describe that IFN alpha-inducible protein 27 (IFI27) co-immunoprecipitates with melanoma differentiation-associated protein 5 (MDA5), being this interaction likely mediated by RNAs. In addition, by using IFI27 overexpression, knock-out, and knock-down cells, we show that IFI27 inhibits MDA5 oligomerization and activation, counteracting the innate immune responses induced after SARS-CoV-2 infections or after polyinosinic-polycytidylic acid (poly(I:C)) transfection. Furthermore, our data indicate that IFI27 competes with MDA5 for poly(I:C) binding, providing a likely explanation for the effect of IFI27 in inhibiting MDA5 activation. This new function of IFI27 could be used to design target-driven compounds to treat diseases associated with an exacerbated induction of innate immune responses, such as those induced by SARS-CoV-2.

Abstract: Cells are equipped with intracellular RIG-like Receptors (RLRs) detecting double stranded (ds)RNA, a molecule with Pathogen-Associated Molecular Pattern (PAMPs) generated during the life cycle of many viruses. Melanoma Differentiation-Associated protein 5 (MDA5), a helicase enzyme member of the RLRs encoded by the ifih1 gene, binds to long dsRNA molecules during a viral infection and initiates production of type I interferon (IFN1) which orchestrates the antiviral response. In order to understand the contribution of MDA5 to viral resistance in fish cells, we have isolated a clonal Chinook salmon Oncorhynchus tshawytscha epithelial-like cell line invalidated for the ifih1 gene by CRISPR/Cas9 genome editing. We demonstrated that IFN1 induction is impaired in this cell line after infection with the Snakehead Rhabdovirus (SHRV), the Salmon Alphavirus (SAV) or Nervous Necrosis Virus (NNV). The cell line, however, did not show any increase in cytopathic effect when infected with SHRV or SAV. Similarly, no cytopathic effect was observed in the ifih1 -/- cell line when infected with Infectious Pancreatic Necrosis Virus (IPNV), Infectious Haemorrhagic Necrotic Virus (IHNV). These results indicate the redundancy of the antiviral innate defence system in CHSE-derived cells, which helps with circumventing viral evasion strategies.

Abstract: Purpose of review Antimelanoma differentiation antigen 5-dermatomyositis (MDA5-DM) is a complex and serious systemic autoimmune disease that primarily affects the skin and lungs. In this review, we aimed to provide new insights into the clinical features, pathogenesis, and practical management approach for this disease. Recent findings Although lung lesions are prominent in most patients with MDA5-DM, they are now recognized as heterogeneous diseases. Peripheral blood lymphocyte count can serve as a simple and reliable laboratory parameter for categorizing MDA5-DM into three subgroups: mild, medium, and severe. Recent studies have implicated viral infection, genetic factors, autoimmunity against MDA5, multiple immune cells, and interferons as significant contributors to MDA5-DM pathogenesis. In addition to traditional treatments with glucocorticoids and immunosuppressants, many new approaches, including new biologics and targeted agents, have been explored. Additionally, infection is a common complication of MDA5-DM, and prophylaxis or treatment of the infection is as important as treating the primary disease. Summary Knowledge of clinical characteristics and pathogenesis of MDA5-DM has grown in recent years. Although many new therapeutic approaches have been explored, further studies are required to confirm their efficacy.

Abstract: Abstract The IFIH1 gene, encoding melanoma differentiation‐associated protein 5 (MDA5), is an indispensable innate immune regulator involved in the early detection of viral infections. Previous studies described MDA5 dysregulation in weakened immunological responses, and increased susceptibility to microbial infections and autoimmune disorders. Monoallelic gain‐of‐function of the IFIH1 gene has been associated with multisystem disorders, namely Aicardi–Goutieres and Singleton–Merten syndromes, while biallelic loss causes immunodeficiency. In this study, nine patients suffering from recurrent infections, inflammatory diseases, severe COVID‐19 or multisystem inflammatory syndrome in children (MIS‐C) were identified with putative loss‐of‐function IFIH1 variants by whole‐exome sequencing. All patients revealed signs of lymphopaenia and an increase in inflammatory markers, including CRP, amyloid A, ferritin and IL‐6. One patient with a pathogenic homozygous variant c.2807+1G>A was the most severe case showing immunodeficiency and glomerulonephritis. The c.1641+1G>C variant was identified in the heterozygous state in patients suffering from periodic fever, COVID‐19 or MIS‐C, while the c.2016delA variant was identified in two patients with inflammatory bowel disease or MIS‐C. There was a significant association between IFIH1 monoallelic loss of function and susceptibility to infections in males. Expression analysis showed that PBMCs of one patient with a c.2016delA variant had a significant decrease in ISG15 , IFNA and IFNG transcript levels, compared to normal PBMCs, upon stimulation with Poly(I:C), suggesting that MDA5 receptor truncation disrupts the immune response. Our findings accentuate the implication of rare monogenic IFIH1 loss‐of‐function variants in altering the immune response, and severely predisposing patients to inflammatory and infectious diseases, including SARS‐CoV‐2‐related disorders.

Abstract: The incessant arms race between viruses and hosts has led to numerous evolutionary innovations that shape the evolution of life. During this process, the interactions between viral receptors and viruses have garnered significant interest since viral receptors are cell surface proteins exploited by viruses to initiate infection. To further understand the interaction between viruses and receptors, our study sheds light on the arms race between the MDA5 receptor and 5’ppp-RNA in vertebrates. Firstly, the frequent and independent loss events of RIG-I in vertebrates prompted us to search for alternative immune substitutes, with homology-dependent genetic compensation response (HDGCR) being the main pathway. Our further analysis suggested that MDA5, the homolog of RIG-I, can replace RIG-I in recognizing 5’ppp-RNA and bind STING for signal transduction, which may lead to redundancy of RIG-I and loss from the species genome during evolution. Secondly, as an adversarial strategy, 5’ppp-RNA SCRV can utilize the m 6 A methylation mechanism to degrade MDA5 and weaken its antiviral immune ability, thus promoting its own replication and immune evasion. In summary, our study has revealed the molecular mechanisms underlying the interaction and coevolution between vertebrate and virus, which providing valuable insights into the ecological and evolutionary factors that contribute to the diversity of the immune system.

Abstract: Loss-of-function variants in MDA5, a key sensor of double-stranded RNA from viruses and retroelements, have been associated with protection from type 1 diabetes (T1D) in genome-wide association studies (GWAS). MDA5 loss-of-function variants have also been reported to increase the risk of inflammatory bowel disease (IBD). Whether these associations are linked or extend to other diseases remains unclear. Here, fine-mapping analysis of four large GWAS datasets shows that T1D-protective loss-of-function MDA5 variants also protect against psoriasis and hypothyroidism, while increasing the risk of IBD. The degree of autoimmune protection and IBD risk were linearly proportional. The magnitudes of the odds ratios for autoimmune protection and IBD risk were larger for rare MDA5 variants than for common variants, which were differentially expressed in different geographic populations. Our analysis suggests MDA5 genetic variants offer a direct fitness trade-off between viral clearance and autoimmune tissue damage.

Abstract: The incessant arms race between viruses and hosts has led to numerous evolutionary innovations that shape life’s evolution. During this process, the interactions between viral receptors and viruses have garnered significant interest since viral receptors are cell surface proteins exploited by viruses to initiate infection. Our study sheds light on the arms race between the MDA5 receptor and 5’ppp-RNA virus in a lower vertebrate fish, M. miiuy . Firstly, the frequent and independent loss events of RIG-I in vertebrates prompted us to search for alternative immune substitutes, with homology-dependent genetic compensation response (HDGCR) being the main pathway. Our further analysis suggested that MDA5 of M. miiuy and G. gallus , the homolog of RIG-I, can replace RIG-I in recognizing 5’ppp-RNA virus, which may lead to redundancy of RIG-I and loss from the species genome during evolution. Secondly, as an adversarial strategy, 5’ppp-RNA SCRV can utilize the m 6 A methylation mechanism to degrade MDA5 and weaken its antiviral immune ability, thus promoting its own replication and immune evasion. In summary, our study provides a snapshot into the interaction and coevolution between vertebrate and virus, offering valuable perspectives on the ecological and evolutionary factors that contribute to the diversity of the immune system.

Abstract: Microglia play a pivotal role in brain homeostasis and are essential to protective immunity within the central nervous system by coordinating the innate immune response to neuroinvasive pathogens. Bacterial endotoxin (lipopolysaccharide, LPS) is the most used pro-inflammatory stimulus for microglia, both in vitroand in vivo. However, the impact of LPS in microglia response to viral infection, including coronaviruses remains ill-defined. Murine coronaviruses productively infect microglia and are well established models of RNA virus-induced encephalitis and demyelination. In the present study, we investigated the effects of TLR4 stimulation with a TLR4-specific agonist [smooth (s)-form LPS (E. coli 0111:B4)] on murine coronavirus MHV-JHM and -A59 infection of microglia in vitro. Mechanistically, our data revealed that LPS stimulation of microglia restrict coronavirus replication through TLR4-dependent induction of interferon (IFN-b) with concomitant modulation of dsRNA sensors melanoma differentiation-associated gene 5 (MDA5) and toll-like receptor 3 (TLR3). Moreover, in the absence of coronavirus infection, LPS induces TLR4-dependent upregulation of MDA5 expression and activation of TLR3, as measured by phosphorylation of its residue Y759, a hallmark of TLR3 signaling initiation. Supporting LPS-induced TLR3 activation, we demonstrated that TLR3 selectively contributes to TLR4-dependent, LPS-induced neuroinflammation even in the absence of virus infection. Overall, the present study provides novel mechanistic insights regarding microglia responses to coronavirus infection and highlights a previously unrecognized crosstalk between bacterial TLR4 and dsRNA sensors in microglia with implications beyond viral infection.

Abstract: Abstract Anti-MDA5 dermatomyositis (DM) is a rare systemic autoimmune condition associated with clinically amyopathic DM and rapidly progressive interstitial lung disease (RP-ILD). It is associated with unique skin features including cutaneous ulceration, eyelid oedema, palmar papules and mechanic’s hands. We present two challenging cases of anti-MDA5 DM with atypical skin manifestations, complicated by RP-ILD, which unfortunately resulted in death in both patients. The first case is a 47-year-old Egyptian woman who initially presented with erythema and burning sensation of the fingertips, thigh rash, arthralgia, joint swelling, dry cough and reduced exercise tolerance. She was diagnosed with undifferentiated inflammatory arthritis and possible amyopathic DM and started on methotrexate and systemic steroids. An autoimmune panel showed weakly positive rheumatoid factor but negative antinuclear antibodies, extractable nuclear antigen, dsDNA, antineutrophil cytoplasmic antibodies and anti-Jo1. Subsequently she presented to accident and emergency with worsening breathlessness and productive cough and was admitted to the intensive care unit, treated for pneumonia. A high-resolution computed tomography (CT) scan was reviewed at a tertiary multidisciplinary team, showing an RP-ILD picture, most likely due to MDA5 DM. She was started on pulsed intravenous methylprednisolone and transferred to a tertiary centre for extracorporeal membrane oxygenation (ECMO) and consideration of rituximab. Unfortunately, she died shortly after. She demonstrated positive anti-MDA5 serology. The second case is a 60-year-old Chinese woman who initially presented to ophthalmology with left-eye oedema and was diagnosed with preseptal cellulitis. Subsequently, she presented again to accident and emergency with fatigue, unintentional weight loss, and reduced mobility. She was cachectic with ulcerating skin lesions on her shoulders and hips. Initial CT of the chest–abdomen–pelvis showed patchy consolidation in both lungs, with nodularity and ground-glass changes. She developed pyrexia and mild hypoxia and was treated for bilateral pneumonia. During admission, fasciculations in her upper limbs and tongue prompted a neurology review. Nerve conduction studies demonstrated myopathic changes. Creatine kinase was elevated, and magnetic resonance imaging of the lower limbs confirmed diffuse oedema. Concurrently, she was noted to have mechanic’s hands and Gottron papules. She developed severe type 1 respiratory failure, requiring transfer to intensive care. Repeat CT imaging showed worsening bilateral consolidation and ground-glass changes, with pleural effusions. Her rapidly progressive respiratory failure in the context of likely DM prompted urgent referral to a tertiary centre for ECMO and aggressive immunosuppression. Unfortunately, she died 3 weeks later. Autoantibody testing confirmed positive anti-MDA5 and Ro52 antibodies.

Abstract: Anti-melanoma differentiation-associated gene 5-positive (Anti-MDA5) dermatomyositis (DM) is an aggressive phenotype of DM associated with rapidly progressive interstitial lung disease (RP-ILD). It is a rare condition that carries high mortality. Diagnosis and management of patients with anti-MDA5 DM RP-ILD presents several challenges, including uncertainty around treatment algorithms and a lack of evidence to inform practice. This case report of a patient with anti-MDA5 DM RP-ILD highlights these challenges, emphasising the fulminant course of this disease despite aggressive immunosuppression. Further research is required to guide management and to minimise morbidity and mortality, and greater awareness of the condition is required to minimise delays in diagnosis.

Abstract: Purpose: Amyopathic dermatomyositis (ADM) is a rare, idiopathic, connective tissue disease and melanoma differentiation-associated protein 5 (MDA5) antibody-positive ADM is more treatment-resistant, especially in patients with interstitial lung disease (ILD). The purpose of this article is to report a case of anti-MDA5-positive ADM successfully treated with JAK inhibitor Upadacitinib.

Abstract: In an Egyptian girl born to consanguineous parents, whole-exome sequencing (WES) identified a homozygous mutation in PHGDH, c.1273G>A (p.Val425Met), indicating 3-phosphoglycerate dehydrogenase deficiency. This diagnosis was compatible with the patient's microcephaly, severe psychomotor retardation, seizures and cataracts. However, she additionally suffered from recurrent (at least monthly) episodes of prolonged and severe chest infections requiring hospitalization, suggesting a secondary, predisposing and potentially Mendelian, condition. A local reactivation of an EBV infection in the respiratory tract was detected after a recent chest infection, likely representing an opportunistic infection based on a compromised immune system. Further inspection of WES data revealed a homozygous nonsense mutation, c.2665A>T (p.Lys889∗), in IFIH1, encoding MDA5. MDA5 detects long viral double-stranded RNA that is generated during replication of picorna viruses, and thereby activates the type I interferon signaling pathway. The results of Western blot analysis of protein from cultured fibroblasts of the patient indicates absence of wild type MDA5/IFIH1, compatible with NMD. We propose that, analogous to the severe course of primary influenza infection due to biallelic deficiency of a downstream effector, IRF7, homozygous loss of IFIH1 defines a novel Mendelian immunodeficiency disorder that increases susceptibility to severe viral infections. This is contrasted to heterozygous gain-of-function IFIH1 mutations in autoimmune diseases. Our findings highlight the potential of comprehensive genomic investigations in patients from consanguineous families to identify monogenic predispositions to severe infections.

Abstract: Dermatomyositis is a rare inflammatory condition affecting the skin, muscles, and joints. This series of anti-melanoma differentiation-associated gene 5 (anti-MDA5) autoantibody-positive cases highlights a possible link between anti-MDA5-positive dermatomyositis and COVID-19 exposure. A retrospective analysis was performed on anti-MDA5-positive dermatomyositis patients at a district general hospital between January 2021 and July 2023. Information was gathered on the clinical profiles, diagnostics, management, and disease course. The two cases are as follows: (1) A 44-year-old Asian female presented with back pain, tender proximal muscles, symmetrical synovitis, and Gottron’s papules, which gradually began after a COVID vaccine and worsened after COVID-19 infection. Despite prompt management, she required finger amputation and a switch to immunomodulators to achieve arthritic disease control. (2) A 49-year-old Caucasian female presented with progressive dyspnea, polyarthralgia, dusky maculopapular rash, and oral ulcers, which began after a COVID vaccine and worsened after COVID-19 infection. Steroids and immunomodulators improved mobility and respiratory symptoms, while biologics subdued her skin symptoms. This case study provides growing evidence for an intriguing association between COVID-19 exposure and anti-MDA5 antibody-positive dermatomyositis. Further research is required to elucidate the underlying pathogenic mechanism. Early involvement of a multidisciplinary team, consideration of symptom variety, infection vigilance, and impact on quality of life are important factors for clinicians to consider when tailoring the management of these patients for optimized outcomes.

Abstract: (Uploaded by Plazi for the Bat Literature Project) Bats are known to harbor many zoonotic viruses, some of which are pathogenic to other mammals while they seem to be harmless in bats. As the interferon (IFN) response represents the first line of defense against viral infections in mammals, it is hypothesized that activation of the IFN system is one of the mechanisms enabling bats to co-exist with viruses. We have previously reported induction of type I IFN in a cell line from the common vampire bat, Desmodus rotundus, upon polyinosinic:polycytidylic acid (poly(I:C)) stimulation. To deepen our knowledge on D. rotundus' IFN-I antiviral response, we molecularly characterized three interferon-stimulated genes (ISGs), OAS1, PKR and ADAR1, closely implicated in the IFN-I antiviral response, and tested their functionality in our cellular model. We first found that D. rotundus encoded two OAS1 paralogs, OAS1a and OAS1b, and that the functional domains of the four ISGs characterized were highly conserved with those of other mammals. Despite their significant transcription level in the absence of stimulation, the transcription of the four ISGs characterized was enhanced by poly(I:C). In addition, the transcription of OAS1a and OAS1b appears to be differentially regulated. These findings demonstrate an active ISG antiviral response in D. rotundus in which OAS1b may play an important role.

Abstract: Abstract Retinoic acid inducible gene I (RIG-I)-like receptors (RLRs), including RIG-I, MDA5 and LGP2, recognize viral RNA to mount an antiviral interferon (IFN) response RLRs share three different protein domains: C-terminal domain, DExD/H box RNA helicase domain, and an N-terminal domain with two tandem repeats (CARDs). LGP2 lacks tandem CARD and is not able to induce an IFN response. However, LGP2 positively enhances MDA5 and negatively regulates RIG-I signaling. In this study, we determined the LGP2 alternative transcripts in humans to further comprehend the mechanism of its regulation, their evolutionary origin, and the isoforms functionallity. The results showed new eight alternative transcripts in the samples tested. The presence of these transcripts demonstrated that the main mechanisms for the regulation of LGP2 expression are both by insertion of introns and by the loss of exons. The phylogenetic analysis of the comparison between sequences from exon 1 to exon 3 of humans and those previously described in non-human primates showed three well-differentiated groups (lineages) originating from gorillas, suggesting that the transspecies evolution has been maintained for 10 million years. The corresponding protein models (isoforms) were also established, obtaining four isoforms: one complete and three others lacking the C-terminal domain or this domain and the partial or total He2 Helicase domain, which would compromise the functionality of LGP2. In conclusion, this is the first study that elucidate the large genomic organization and complex transcriptional regulation of human LGP2, its pattern of sequence generation, and a mode of evolutionary inheritance across species.