Genotypic definition of monogenic inborn errors of immunity (IEIs) continues to accelerate with broader access to next generation sequencing, underscoring this aggregated group of disorders as a ...major health burden impacting both civilian and military populations. At an estimated prevalence of 1 in 1200 individuals, IEIs affect ~8,000 patients within the Military Health System (MHS). Despite access to targeted gene/exome panels at military treatment facilities, most affected patients never receive a definitive genetic diagnosis that would significantly improve clinical care. To address this gap, we established the first registry of IEI patients within the MHS with the goal of identifying known and novel pathogenic genetic defects to increase diagnosis rates and enhance clinical care. Using the registry, a research protocol was opened in July 2022. Since July we have enrolled 75 IEI patients encompassing a breadth of phenotypes including severe and recurrent infections, bone marrow failure, autoimmunity/autoinflammation, atopic disease, and malignancy. Enrolled patients provide blood and bone marrow samples for whole genome, ultra-deep targeted panel and comprehensive transcriptome sequencing, plus cryopreservation of peripheral blood mononuclear cells for future functional studies. We are also implementing and developing analytical methods for identifying and interrogating non-coding and structural variants. Suspected pathogenic variants are adjudicated by a clinical molecular geneticist using state-of-the-art analysis pipelines. These analyses subsequently inform in vitro experiments to validate causative mutations using cell reporter systems and primary patient cells. Clinical variant validation and return of genetic results are planned with genetic counseling provided. As a proof of principle, this integrated genetic evaluation pipeline revealed a novel, candidate TLR7 nonsense variant in two adolescent brothers who both endured critical COVID-19 pneumonia, requiring mechanical ventilation and extracorporeal membrane oxygenation. Our protocol is therefore poised to greatly enrich clinical genetics resources available in the MHS for IEI patients, contributing to better diagnosis rates, informed family counseling, and targeted treatments that collectively improve the health and readiness of the military community. Moreover, our efforts should yield new mechanistic insights on immune pathogenesis for a broad variety of known and novel IEIs.
Recently, loss-of-function variants in TLR7 were identified in two families in which COVID-19 segregates like an X-linked recessive disorder environmentally conditioned by SARS-CoV-2. We investigated ...whether the two families represent the tip of the iceberg of a subset of COVID-19 male patients.
This is a nested case-control study in which we compared male participants with extreme phenotype selected from the Italian GEN-COVID cohort of SARS-CoV-2-infected participants (<60 y, 79 severe cases versus 77 control cases). We applied the LASSO Logistic Regression analysis, considering only rare variants on young male subsets with extreme phenotype, picking up TLR7 as the most important susceptibility gene.
Overall, we found TLR7 deleterious variants in 2.1% of severely affected males and in none of the asymptomatic participants. The functional gene expression profile analysis demonstrated a reduction in TLR7-related gene expression in patients compared with controls demonstrating an impairment in type I and II IFN responses.
Young males with TLR7 loss-of-function variants and severe COVID-19 represent a subset of male patients contributing to disease susceptibility in up to 2% of severe COVID-19.
Funded by private donors for the Host Genetics Research Project, the Intesa San Paolo for 2020 charity fund, and the Host Genetics Initiative.
NCT04549831.
Unc-93 homolog B1 (UNC93B1) is a key regulator of nucleic acid (NA)-sensing Toll-like receptors (TLRs). Loss of NA-sensing TLR responses in UNC93B1-deficient patients facilitates Herpes simplex virus ...type 1 (HSV-1) encephalitis. UNC93B1 is thought to guide NA-sensing TLRs from the endoplasmic reticulum (ER) to their respective endosomal signaling compartments and to guide the flagellin receptor TLR5 to the cell surface, raising the question of how UNC93B1 mediates differential TLR trafficking. Here, we report that UNC93B1 regulates a step upstream of the differential TLR trafficking process. We discovered that UNC93B1 deficiency resulted in near-complete loss of TLR3 and TLR7 proteins in primary splenic mouse dendritic cells and macrophages, showing that UNC93B1 is critical for maintaining TLR expression. Notably, expression of an ER-retained UNC93B1 version was sufficient to stabilize TLRs and largely restore endosomal TLR trafficking and activity. These data are critical for an understanding of how UNC93B1 can regulate the function of a broad subset of TLRs.
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•The trafficking of UNC93B1 and its client TLRs are separable events•ER-retained UNC93B1 is sufficient to restore UNC93B1-dependent TLR activities•UNC93B1 is essential for stabilizing nucleic-acid-sensing TLRs•UNC93B1-dependent TLR proteins are severely reduced in Unc93b1−/− and Unc93b13d/3d mice
UNC93B1 is known as a trafficking chaperone for both endosomal TLRs and cell-surface TLR5, but how UNC93B1 transports its client TLRs to different compartments remains to be determined. Pelka and colleagues show that, in fact, UNC93B1 functions upstream of differential trafficking pathways and is crucial for stabilizing UNC93B1-dependent TLRs.
Toll-like receptor 7 (TLR7) is essential for recognition of RNA viruses and initiation of antiviral immunity. TLR7 contains two ligand-binding pockets that recognize different RNA degradation ...products: pocket 1 recognizes guanosine, while pocket 2 coordinates pyrimidine-rich RNA fragments. We found that the endonuclease RNase T2, along with 5′ exonucleases PLD3 and PLD4, collaboratively generate the ligands for TLR7. Specifically, RNase T2 generated guanosine 2′,3′-cyclic monophosphate-terminated RNA fragments. PLD exonuclease activity further released the terminal 2′,3′-cyclic guanosine monophosphate (2',3'-cGMP) to engage pocket 1 and was also needed to generate RNA fragments for pocket 2. Loss-of-function studies in cell lines and primary cells confirmed the critical requirement for PLD activity. Biochemical and structural studies showed that PLD enzymes form homodimers with two ligand-binding sites important for activity. Previously identified disease-associated PLD mutants failed to form stable dimers. Together, our data provide a mechanistic basis for the detection of RNA fragments by TLR7.
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•RNase T2 and PLD exonucleases process RNA upstream of TLR7•PLD exonucleases release terminal 2′,3′-cyclic GMPs to engage TLR7 pocket 1•PLD enzymes are also critical to generate RNA fragments for TLR7 pocket 2•PLDs dimer formation is needed for RNA substrate processing
TLR7 is critical for recognizing RNA virus infection and initiating antiviral responses. Bérouti et al. demonstrate how RNase T2 and PLD exonucleases generate RNA fragments for TLR7 activation, thus providing insights into immune recognition of exogenous RNAs, with potential therapeutic implications.
Class-switched antibodies to double-stranded DNA (dsDNA) are prevalent and pathogenic in systemic lupus erythematosus (SLE), yet mechanisms of their development remain poorly understood. Humans and ...mice lacking secreted DNase DNASE1L3 develop rapid anti-dsDNA antibody responses and SLE-like disease. We report that anti-DNA responses in Dnase1l3−/− mice require CD40L-mediated T cell help, but proceed independently of germinal center formation via short-lived antibody-forming cells (AFCs) localized to extrafollicular regions. Type I interferon (IFN-I) signaling and IFN-I-producing plasmacytoid dendritic cells (pDCs) facilitate the differentiation of DNA-reactive AFCs in vivo and in vitro and are required for downstream manifestations of autoimmunity. Moreover, the endosomal DNA sensor TLR9 promotes anti-dsDNA responses and SLE-like disease in Dnase1l3−/− mice redundantly with another nucleic acid-sensing receptor, TLR7. These results establish extrafollicular B cell differentiation into short-lived AFCs as a key mechanism of anti-DNA autoreactivity and reveal a major contribution of pDCs, endosomal Toll-like receptors (TLRs), and IFN-I to this pathway.
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•Anti-DNA antibody response is driven by T-dependent extrafollicular plasmablasts•IFN-I signaling propagates anti-DNA responses and SLE-like disease•IFN-I produced by pDCs promotes plasmablast proliferation and differentiation•TLR9 drives anti-DNA responses and autoimmunity redundantly with TLR7
Autoantibodies to self-DNA are a defining feature of systemic lupus erythematosus (SLE), yet the mechanisms of their development remain poorly understood. Soni et al. show that anti-DNA autoreactivity is driven by extrafollicular B cell differentiation into short-lived plasmablasts, which is facilitated by plasmacytoid dendritic cells, type I interferon, and endosomal Toll-like receptors 7 and 9.
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•Vesatolimod was safe and well-tolerated in patients with chronic HBV infection.•Dose-dependent pharmacodynamic induction of ISGs was demonstrated with vesatolimod.•No significant ...HBsAg declines were observed with vesatolimod treatment.
Vesatolimod (GS-9620) is an oral agonist of toll-like receptor 7, an activator of innate and adaptive immune responses. Herein the safety and efficacy of vesatolimod is assessed after once-weekly treatment in patients with chronic hepatitis B (CHB) infection suppressed on oral antiviral treatment.
In a phase II, double-blind, randomized, placebo (PBO)-controlled study, 162 patients stratified by hepatitis B surface antigen (HBsAg) levels and serum hepatitis B e antigen (HBeAg) status were randomized 1:3:3:3 to once-weekly oral PBO or vesatolimod (1-, 2-, or 4-mg doses) for 4, 8 or 12 weeks per cohort. Efficacy was assessed by change in baseline HBsAg (log10 IU/ml) at the primary endpoint (Week 24). Safety assessments included adverse events (AE) and laboratory abnormality monitoring. Pharmacodynamic assessments included peripheral cytokine level quantification and interferon-stimulated gene (ISG) mRNA expression evaluation.
The majority of patients were male (76%) and HBeAg-negative (79%) at baseline. Most (41–80%) experienced ≥1 AE during the study with the majority of AEs mild or moderate in severity. No significant declines in HBsAg were observed at the primary (Week 24) or secondary endpoints (Weeks 4, 8, 12, and 48). ISG15 induction was dose-dependent and consistent after repeat dosing, returning closer to baseline by one week after treatment at all dose levels; no patient demonstrated significant serum interferon alpha (IFNα) expression at any timepoint evaluated. Multivariate analyses showed that ≥2-fold ISG15 induction is associated with 2- or 4-mg vesatolimod dose and female sex.
Vesatolimod was safe and well-tolerated in patients with CHB, demonstrating consistent dose-dependent pharmacodynamic induction of ISG15 without significant systemic induction of IFNα expression or related symptoms. However, no significant HBsAg declines were observed.
In a phase II study, vesatolimod, an oral, once-weekly, experimental immune-activating drug for the treatment of hepatitis B virus (HBV), is safe and well-tolerated in chronic HBV patients who are virally suppressed on oral antiviral treatment. Despite demonstrating on-target biomarker responses in patients, no significant declines in hepatitis B surface antigen were observed.
Clinical Trial Number: GS-US-283-1059; NCT 02166047.
At least two members of the Toll-like receptor (TLR) family, TLR7 and TLR9, can recognize self-RNA and self-DNA, respectively. Despite the structural and functional similarities between these ...receptors, their contributions to autoimmune diseases such as systemic lupus erythematosus can differ. For example, TLR7 and TLR9 have opposing effects in mouse models of systemic lupus erythematosus-disease is exacerbated in TLR9-deficient mice but attenuated in TLR7-deficient mice
. However, the mechanisms of negative regulation that differentiate between TLR7 and TLR9 are unknown. Here we report a function for the TLR trafficking chaperone UNC93B1 that specifically limits signalling of TLR7, but not TLR9, and prevents TLR7-dependent autoimmunity in mice. Mutations in UNC93B1 that lead to enhanced TLR7 signalling also disrupt binding of UNC93B1 to syntenin-1, which has been implicated in the biogenesis of exosomes
. Both UNC93B1 and TLR7 can be detected in exosomes, suggesting that recruitment of syntenin-1 by UNC93B1 facilitates the sorting of TLR7 into intralumenal vesicles of multivesicular bodies, which terminates signalling. Binding of syntenin-1 requires phosphorylation of UNC93B1 and provides a mechanism for dynamic regulation of TLR7 activation and signalling. Thus, UNC93B1 not only enables the proper trafficking of nucleic acid-sensing TLRs, but also sets the activation threshold of potentially self-reactive TLR7.
Understanding the molecular pathways driving the acute antiviral and inflammatory response to SARS‐CoV‐2 infection is critical for developing treatments for severe COVID‐19. Here, we find decreasing ...number of circulating plasmacytoid dendritic cells (pDCs) in COVID‐19 patients early after symptom onset, correlating with disease severity. pDC depletion is transient and coincides with decreased expression of antiviral type I IFNα and of systemic inflammatory cytokines CXCL10 and IL‐6. Using an in vitro stem cell‐based human pDC model, we further demonstrate that pDCs, while not supporting SARS‐CoV‐2 replication, directly sense the virus and in response produce multiple antiviral (interferons: IFNα and IFNλ1) and inflammatory (IL‐6, IL‐8, CXCL10) cytokines that protect epithelial cells from de novo SARS‐CoV‐2 infection. Via targeted deletion of virus‐recognition innate immune pathways, we identify TLR7‐MyD88 signaling as crucial for production of antiviral interferons (IFNs), whereas Toll‐like receptor (TLR)2 is responsible for the inflammatory IL‐6 response. We further show that SARS‐CoV‐2 engages the receptor neuropilin‐1 on pDCs to selectively mitigate the antiviral interferon response, but not the IL‐6 response, suggesting neuropilin‐1 as potential therapeutic target for stimulation of TLR7‐mediated antiviral protection.
Synopsis
Plasmacytoid dendritic cells (pDCs) sense SARS‐CoV‐2 via two distinct innate immune pathways. The endosomal TLR7 pathway is activated upon sensing of viral RNA and this leads to type I IFN production. The TLR2 pathway is triggered by sensing of the viral envelope protein, inducing IL‐6 production. Interestingly, SARS‐CoV‐2 is able to specifically antagonize the TLR7‐IFN pathway via a CD304‐mediated signaling cascade.
Sensing of SARS‐CoV‐2 RNA by pDCs triggers a signaling cascade involving TLR7‐MyD88‐IRAK4‐TRAF6 to induce CXCL10 and, via IRF7 phosphorylation and translocation, type I and III Interferons. In parallel, SARS‐CoV‐2 envelope (E) glycoprotein is sensed by the extracellular TLR2/6 heterodimer facilitating production of IL‐6.
The secreted type I and III IFNs initiate autocrine and paracrine signals that induce the expression of IFN stimulated genes (ISGs), thereby facilitating an antiviral response that protects local epithelial cells against SARS‐CoV‐2 infection.
SARS‐CoV‐2 can counteract the protective IFN effects by inducing CD304 signaling, potentially interfering with IRF7 nuclear translocation, thereby inhibiting type I IFNα production and thus reducing the antiviral response generated by pDCs.
Sensing of SARS‐CoV‐2 by plasmacytoid dendritic cells (pDC) contributes to the anti‐viral and immunopathological responses.
Introduction
Loss-of-function
TLR7
variants have been recently reported in a small number of males to underlie strong predisposition to severe COVID-19. We aimed to determine the presence of these ...rare variants in young men with severe COVID-19.
Methods
We prospectively studied males between 18 and 50 years-old without predisposing comorbidities that required at least high-flow nasal oxygen to treat COVID-19. The coding region of
TLR7
was sequenced to assess the presence of potentially deleterious variants.
Results
TLR7
missense variants were identified in two out of 14 patients (14.3%). Overall, the median age was 38 (IQR 30-45) years. Both variants were not previously reported in population control databases and were predicted to be damaging by
in silico
predictors. In a 30-year-old patient a maternally inherited variant c.644A>G; p.(Asn215Ser) was identified, co-segregating in his 27-year-old brother who also contracted severe COVID-19. A second variant c.2797T>C; p.(Trp933Arg) was found in a 28-year-old patient, co-segregating in his 24-year-old brother who developed mild COVID-19. Functional testing of this variant revealed decreased type I and II interferon responses in peripheral mononuclear blood cells upon stimulation with the TLR7 agonist imiquimod, confirming a loss-of-function effect.
Conclusions
This study supports a rationale for the genetic screening for
TLR7
variants in young men with severe COVID-19 in the absence of other relevant risk factors. A diagnosis of TLR7 deficiency could not only inform on treatment options for the patient, but also enables pre-symptomatic testing of at-risk male relatives with the possibility of instituting early preventive and therapeutic interventions.
Hepatic injury is often accompanied by pulmonary inflammation and tissue damage, but the underlying mechanism is not fully elucidated. Here we identify hepatic miR-122 as a mediator of pulmonary ...inflammation induced by various liver injuries. Analyses of acute and chronic liver injury mouse models confirm that liver dysfunction can cause pulmonary inflammation and tissue damage. Injured livers release large amounts of miR-122 in an exosome-independent manner into the circulation compared with normal livers. Circulating miR-122 is then preferentially transported to mouse lungs and taken up by alveolar macrophages, in which it binds Toll-like receptor 7 (TLR7) and activates inflammatory responses. Depleting miR-122 in mouse liver or plasma largely abolishes liver injury-induced pulmonary inflammation and tissue damage. Furthermore, alveolar macrophage activation by miR-122 is blocked by mutating the TLR7-binding GU-rich sequence on miR-122 or knocking out macrophage TLR7. Our findings reveal a causative role of hepatic miR-122 in liver injury-induced pulmonary dysfunction.
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