MIS-C, inherited metabolic diseases and methylmalonic acidemia: a case report and review of the literature (preprint)

Bacground Methylmalonic acidemia (MMA) secondary to mutase deficiency, mut0, is an inborn error of metabolism causing complete enzyme deficiency. Multisystem Inflammatory Syndrome in Children (MIS-C) is a hyperinflammatory syndrome characterized by fever, inflammation, multiorgan impairment that manifests 14–60 days after the SARS-CoV-2 infection in patients aged < 21 years. Case presentation We describe the clinical case of a 2-year-old child with MMA secondary to mutase deficiency, with the documented homozygous mutation c.2179 C > T of MMUT gene, associated to mut0 phenotype. One month after SARS-CoV-2 infection, he presented fever, rash, significant increase of C-reactive protein (CRP), ferritin, triglycerides, (interleukin) IL-6, PRO-BNP, compatible with the diagnosis of MIS-C. He was treated with intravenous immunoglobulins (2gr/Kg), methylprednisolone (2 mg/Kg/day), with rapid clinical improvement. Ten days later, he showed the worsening of clinical conditions, with the recurrence of fever, vasculitic rash with palmoplantar extension, further increase of ferritin (1033 ug/l), IL-6 (146 pg/ml), PRO-BNP (5117 pg/ml), triglycerides, anemia, thrombocytopenia, metabolic acidosis with hyperlactatemia (180 mg/dl), increased urinary methylmalonic acid (200 mmol/mCreat), multiorgan failure. He was treated with sodium bicarbonate, thiamine, coenzyme Q, vitamin C, methylprednisolone and anakinra (2 mg/Kg/day). Three days after the start of anakinra, he showed a significant improvement of clinical and biochemical parameters and defervescence. 20 days later, a sepsis from Staphylococcus Aureus and Candida Albicans required the interruption of anakinra, with the worsening of the clinical and haematological parameters and the exitus. Conclusions Only a few cases of patients with inherited metabolic diseases (IMD) and MIS-C are described. However, to our knowledge, this is the first case of MIS-C in MMA described. The description of these clinical cases is a precious lesson for pediatricians to manage IMD therapeutic emergencies. Anakinra must be considered as a safe treatment of choice in IMD patients with MIS-C. The use of anakinra in patients with a severe form of MMA is safe and can be employed to treat MIS-C, gaining a substantial clinical and biochemical improvement.

Rethinking immunologic risk: a retrospective cohort study of severe SARS-CoV-2 infections in individuals with congenital immunodeficiencies (preprint)

Background. Debates on the allocation of medical resources during the COVID-19 pandemic revealed the need for a better understanding of immunologic risk. Studies highlighted variable clinical outcomes of SARS-CoV-2 infections in individuals with defects in both adaptive and innate immunity, suggesting additional contributions from other factors. Notably, none of these studies controlled for variables linked with social determinants of health. Objective. To determine the contributions of determinants of health to risk of hospitalization for SARS-CoV-2 infection among individuals with inborn errors of immunodeficiencies. Methods. This is a retrospective, single-center cohort study of 166 individuals with inborn errors of immunity, aged two months through 69 years, who developed SARS-CoV-2 infections from March 1, 2020 through March 31, 2022. Risks of hospitalization was assessed using a multivariable logistic regression analysis. Results. The risk of SARS-CoV-2-related hospitalization was associated with underrepresented racial and ethnic populations (odds ratio [OR] 5.29; confidence interval [CI], 1.76-17.0), a diagnosis of any genetically-defined immunodeficiency (OR 4.62; CI, 1.60-14.8), use of B cell depleting therapy within one year of infection (OR 6.1; CI, 1.05-38.5), obesity (OR 3.74; CI, 1.17-12.5), and neurologic disease (OR 5.38; CI, 1.61-17.8). COVID-19 vaccination was associated with reduced hospitalization risk (OR 0.52; CI, 0.31-0.81). Defective T cell function, immune-mediated organ dysfunction, and social vulnerability were not associated with increased risk of hospitalization after controlling for covariates. Conclusions. The associations between race, ethnicity, and obesity with increased risk of hospitalization for SARS-CoV-2 infection indicate the importance of variables linked with social determinants of health as immunologic risk factors for individuals with inborn errors of immunity.

Vaccination strategies for people living with inborn errors of metabolism in Brazil.

OBJECTIVE: Through a literature review, make recommendations regarding immunizations in people living with Inborn Error of Metabolism (IEM) in Brazil, assess the possible impact on metabolic decompensations after immunization, and if this specific population may have an impaired immune response to vaccines. SOURCE OF DATA: The MeSH Terms vaccination OR vaccine OR immunization associated with the term inborn error of metabolism AND recommendation were used in combination with search databases. Only articles published after 1990, in the languages English, Spanish, French or Portuguese, human-related were included. SYNTHESIS OF DATA: A total of 44 articles were included to make the following recommendations. Individuals with IEMs need to be up to date with their immunizations. Regarding which vaccines should be offered, children and adults should follow the routine immunization schedules locally available, including the COVID-19 vaccines. The only exception is the rotavirus vaccine for hereditary fructose intolerance. The benefit of immunization outweighs the very low risk of metabolic decompensation. Since not all patients will have an adequate immune response, measuring antibody conversion and titers is recommended CONCLUSIONS: All patients should receive age-appropriate immunizations in their respective schedules without delays. The only situation when vaccination may be contraindicated is with oral rotavirus vaccine in hereditary fructose intolerance. Monitoring the levels of antibodies should be done to detect any immune dysfunction or the necessity for boosters. A personalized immunization schedule is ideal for patients with IEMs. The reference organizations could improve their recommendations to address all IEMs, not only some of them.

Inborn errors of metabolism and coronavirus disease 2019: Evaluation of the metabolic outcome.

BACKGROUND: Infectious diseases can result in a catabolic state and possibly trigger an acute metabolic decompensation in inborn errors of metabolism (IEM), which could be life threatening. Studies regarding the course of severe acute respiratory syndrome coronavirus 2 infections in patients with IEM are generally limited to case reports. Here, we aimed to evaluate the clinical findings of coronavirus disease 2019 (COVID-19) and describe the impact of severe acute respiratory syndrome coronavirus 2 infections on metabolic outcomes in IEM patients. METHODS: Patients who were diagnosed with different types of IEM and developed microbiologically confirmed COVID-19 infection were included. Clinical findings and laboratory results were recorded retrospectively in terms of both IEM and COVID-19. RESULTS: Eleven patients with diagnosis of intoxication type metabolic disorders, five patients with energy metabolism disorders, and six patients with complex molecular disorders were enrolled. The most frequent clinical finding was fever (52.1%) followed by fatigue/myalgia (47.8%). None of the patients was younger than 1 year. None of the patients presented severe or critical disease. In terms of metabolic decompensation, two patients diagnosed with propionic acidemia, one patient with methylmalonic acidemia and one patient with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency presented clinical and biochemical findings of an acute metabolic attack. CONCLUSIONS: Based on our results, IEM are not found to be an additional risk factor for severe COVID-19 infection. However, patients with intoxication type and energy metabolism disorders should be considered as a vulnerable population for COVID-19 and have a major risk of developing acute metabolic decompensation that can lead to life-threatening complications.

A Next Generation Sequencing (NGS)-based approach to diagnosing Algerian patients with suspected Inborn Errors of Immunity (IEIs) (preprint)

The advent of next-generation sequencing (NGS) technologies has greatly expanded our understanding of both the clinical spectra and genetic landscape of inborn errors of immunity (IEIs). As history has shown and recent large-scale studies of monogenic risk for severe COVID have confirmed, endogamous populations may be enriched for unique, ancestry-specific disease-causing variants as a consequence of geography and/or culture. From a diagnostic perspective, this consideration may significantly impact molecular testing and analysis strategies. Herein, we report on the diagnostic yield of a 2-step NGS-based testing approach beginning with targeted gene panels (TGPs) and reflexing to whole exome sequencing (WES) if negative for Northwest Algerian patients with suspected IEIs. A total of fourteen families were screened using TGPs tailored to their IEI subtypes of common variable immunodeficiency (CVID), inflammatory bowel disease (IBD) or chronic mucocutaneous candidiasis (CMC)-hyperIgE syndrome (HIES), resulting in a total of four definitive or highly likely molecular diagnoses (29% yield). Subsequent application of WES to eight of the ten remaining unsolved cases yielded an additional four diagnoses, giving a 57% overall yield. At least two additional individuals were found to harbor suggestive candidate variants on exome warranting further investigation, while others carried candidate variants or known risk alleles likely contributing to their clinical findings. Only in one patient’s case did we fail to identify any viable potential candidates. By achieving diagnostic yields comparable to those currently quoted for application of short-read NGS to IEI detection, our study demonstrates the viability of a 2-step NGS-based testing strategy in a selected endogamous population. Data from our localized cohort also showed some similarities and differences from NGS studies performed on larger regional IEI cohorts. Finally, our results also highlight many short-comings currently inherent to the application of genomics for clinical IEI diagnostics. Not only does the global community need to address ongoing inequities in representation, access, and infrastructure, but the ability to obtain precise and detailed clinical data remains paramount for achieving diagnostic certainty in the face of complex genotype-phenotype relationships.

BNT162b2 COVID-19 vaccination elicited protective robust immune responses in pediatric patients with inborn errors of metabolism.

Introduction: SARS-CoV-2 infection can lead to a life-threatening acute metabolic decompensation in children with inborn errors of metabolism (IEM), so vaccination is mandatory. However, IEMs can also impair innate or adaptive immunity, and the impact of these immune system alterations on immunogenicity and vaccine efficacy is still unknown. Here, we investigated humoral immune responses to the BNT162b2 mRNA COVID-19 vaccine and clinical outcomes in pediatric IEM patients. Methods: Fifteen patients between 12-18 years of age with a confirmed diagnosis of IEM, and received BNT162b2 were enrolled to the study. Patients with an anti-SARS-CoV-2 IgG concentration >50 AU/mL before vaccination were defined as "COVID-19 recovered" whereas patients with undetectable anti-SARS-CoV-2 IgG concentration were defined as "COVID-19 naïve". Anti-SARS-CoV-2 Immunoglobulin G (IgG) and SARS-CoV-2 neutralizing antibody (nAb) titers were measured to assess humoral immune response. Results: Anti-SARS-CoV-2 IgG titers and nAb IH% increased significantly after the first dose. The increase in antibody titers after first and second vaccination remained significant in COVID-19 naïve patients. Complete anti-SARS-CoV-2 IgG seropositivity and nAb IH% positivity was observed in all patients after the second dose. Vaccination appears to be clinically effective in IEM patients, as none of the patients had COVID-19 infection within six months of the last vaccination. Discussion: Humoral immune response after two doses of BNT162b2 in pediatric IEM patients was adequate and the immune response was not different from that of healthy individuals.

Rare predicted loss-of-function variants of type I IFN immunity genes are associated with critical COVID-19 (preprint)

Background We previously reported inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity in 1-5% of unvaccinated patients with life-threatening COVID-19, and autoantibodies against type I IFN in another 15-20% of cases. Methods We report here a genome-wide rare variant burden association analysis in 3,269 unvaccinated patients with life-threatening COVID-19 (1,301 previously reported and 1,968 new patients), and 1,373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. A quarter of the patients tested had antibodies against type I IFN (234 of 928) and were excluded from the analysis. Results No gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7, with an OR of 27.68 (95%CI:1.5-528.7, P=1.1x10-4), in analyses restricted to biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR=3.70 [95%CI:1.3-8.2], P=2.1x10-4). Adding the recently reported TYK2 COVID-19 locus strengthened this enrichment, particularly under a recessive model (OR=19.65 [95%CI:2.1-2635.4]; P=3.4x10-3). When these 14 loci and TLR7 were considered, all individuals hemizygous (n=20) or homozygous (n=5) for pLOF or bLOF variants were patients (OR=39.19 [95%CI:5.2-5037.0], P=4.7x10-7), who also showed an enrichment in heterozygous variants (OR=2.36 [95%CI:1.0-5.9], P=0.02). Finally, the patients 13 with pLOF or bLOF variants at these 15 loci were significantly younger (mean age [SD]=43.3 [20.3] years) than the other patients (56.0 [17.3] years; P=1.68x10-5). Conclusions Rare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie lifethreatening COVID-19, particularly with recessive inheritance, in patients under 60 years old.

RNA solutions to treat inborn errors of metabolism.

RNA-based therapies are a new, rapidly growing class of drugs that until a few years ago were being used mainly in research in rare diseases. However, the clinical efficacy of recently approved oligonucleotide drugs and the massive success of COVID-19 RNA vaccines has boosted the interest in this type of molecules of both scientists and industry, as wells as of the lay public. RNA drugs are easy to design and cost effective, with greatly improved pharmacokinetic properties thanks to progress in oligonucleotide chemistry over the years. Depending on the type of strategy employed, RNA therapies offer the versatility to replace, supplement, correct, suppress, or eliminate the expression of a targeted gene. Currently, there are more than a dozen RNA-based drugs approved for clinical use, including some for specific inborn errors of metabolism (IEM), and many other in different stages of development. New initiatives in n-of-1 RNA drug development offer new hope for patients with rare diseases and/or ultra-rare mutations. RNA-based therapeutics include antisense oligonucleotides, aptamers, small interfering RNAs, small activating RNAs, microRNAs, lncRNAs and messenger RNAs. Further research and collaborations in the fields of chemistry, biology and medicine will help to overcome major challenges in their delivery to target tissues. Herein, we review the mechanism of action of the different therapeutic approaches using RNA drugs, focusing on those approved or in clinical trials to treat IEM.

Safety and Immunogenicity of 3 Doses of BNT162b2 and CoronaVac in Children and Adults with Inborn Errors of Immunity (preprint)

Background: Safety and immunogenicity of 3 doses of BNT162b2 and CoronaVac in adult and pediatric patients with inborn errors of immunity (IEIs) remain unknown. Intradermal vaccination may improve immunogenicity in immunocompromised patients. Our study (NCT04800133) aimed to determine the safety and immunogenicity in patients with IEIs receiving a 3-dose primary series of mRNA vaccine BNT162b2 (age 12+) or inactivated whole-virion vaccine CoronaVac (age 3+) in Hong Kong, including Omicron BA.1 neutralization, in a nonrandomized manner. Intradermal vaccination was also studied. Methods Thirty-nine patients were vaccinated, including 16 with homologous intramuscular 0.3ml BNT162b2 and 17 with homologous intramuscular 0.5ml CoronaVac. Two patients received 3 doses of intradermal 0.5ml CoronaVac, and 4 patients received 2 doses of intramuscular BNT162b2 and the third dose with intradermal BNT162b2. Adverse reactions and adverse events were tracked for 7 and 28 days after each dose. Antibody responses assessed included binding IgG antibody to wild-type (WT) spike receptor-binding domain (S-RBD IgG) and surrogate neutralization activity to WT and BA.1 viruses. T cell responses were examined by intracellular cytokine staining following stimulation with SARS-CoV-2 peptide pool(s). Results No safety concerns were identified. Inadequate antibody responses were found after 2 doses in patients with humoral immunodeficiencies and especially so against BA.1. Dose 3 of either vaccine increased S-RBD IgG response. T cell responses against SARS-CoV-2 antigens were detected in vaccinated IEI patients. Intradermal third dose vaccine led to high antibody response in 4 patients. Conclusions The primary vaccination series of BNT162b2 and CoronaVac in adults and children with IEIs should include 3 doses for optimal immunogenicity.

Inborn error of metabolism precipitated by COVID-19: challenges in the absence of an expanded newborn screening as state health programmes.

Inborn errors of metabolism constitute a differential diagnosis in infants presenting with encephalopathy in developing countries where expanded newborn screening is not a state health programme. Acute neurological presentation with encephalopathy is documented in paediatric COVID-19. The pandemic has also altered parents' healthcare-seeking behaviour, leading to delays in emergency care. We illustrate the challenges faced in diagnosing and managing an 18-month-old child who presented with acute metabolic crisis due to methylmalonic acidaemia on the background of the COVID-19 pandemic. We discuss the current global status of expanded newborn screening services for inborn error of metabolism and the impact of the pandemic on the healthcare of children.

Acquired long QT syndrome due to antiemetics, COVID-19 and Blastocystis hominis induced exacerbation of congenital chloride losing diarrhoea.

Congenital chloride losing diarrhoea (CCLD) is a rare disease caused by mutations in an intestinal chloride/bicarbonate ion exchange channel. Few reports describe CCLD in adults and none has described the impact of a parasitic infection on CCLD. Severe diarrhoea may result in hypokalaemia with QT interval prolongation. Treatment with antiemetics may further increase the QT interval. To raise awareness of this preventable complication, we describe the course of a woman in her 20s with CCLD who developed COVID-19 and a Blastocystis hominis infestation. Treatment with antiemetics and hypokalaemia resulted in prolongation of the QT interval to 640 ms. While, the QT interval normalised with discontinuation of antiemetics and electrolyte replacement, patients with CCLD must take precautions to prevent gastrointestinal infections. Regardless, whenever patients with CCLD present to hospital, the authors recommend monitoring the QT interval and avoiding medications that predispose to torsade de pointes.

Trio-based whole exome sequencing in patients with suspected sporadic inborn errors of immunity: a retrospective cohort study (preprint)

Background D e novo variants (DNVs) are currently not routinely evaluated as part of diagnostic whole exome sequencing (WES) analysis in patients with suspected inborn errors of immunity (IEI). Methods This study explored the potential added value of systematic assessment of DNVs in a retrospective cohort of 123 patients with a suspected sporadic IEI who underwent patient-parent trio-based WES. Results A likely molecular diagnosis for (part) of the immunological phenotype was achieved in 12 patients with the diagnostic in silico IEI WES gene panel. Exome-wide evaluation of rare, non-synonymous DNVs affecting coding or splice site regions led to the identification of 14 candidate DNVs in genes with an annotated immune function. DNVs were identified in IEI genes ( NLRP3 and RELA ) and potentially novel candidate genes, including PSMB10 , DDX1 , KMT2C and FBXW11 . The FBXW11 canonical splice site DNV, in a patient with autoinflammatory disease, was shown to lead to defective RNA splicing, increased NF-κB p65 signalling, and elevated IL-1β production in primary immune cells. Conclusions This retrospective cohort study advocates the implementation of trio-based sequencing in routine diagnostics of patients with sporadic IEI. Furthermore, we have provided functional evidence supporting a causal role for FBXW11 loss-of-function mutations in autoinflammatory disease. Funding This research was supported by grants from the European Union, ZonMW and the Radboud Institute for Molecular Life Sciences.

Rare Variants in Inborn Errors of Immunity Genes Associated with Covid-19 Severity (preprint)

Covid-19 is a contagious disease caused by SARS-CoV-2, a novel severe acute respiratory syndrome coronavirus. Common variants and networks underlying host genetic mechanisms have been extensively studied to identify disease-associated genetic factors. However, there are few studies about the rare variants, typically inborn errors of immunity, in understanding the host genetics behind Covid-19 infection, especially in the Chinese population. To fill this gap, we investigate likely-deleterious missense and high-confidence predicted loss-of-function variants by (a) performing gene- and pathway-level association analyses, (b) examining known genes involved in type I interferon signaling and others previously reported in Covid-19 disease, and (c) identifying candidate genes with accumulating mutations and their potential protein-protein interactions with known genes. Based on our analyses, several putative genes and pathways are uncovered and worth further investigation, for example, genes IL12RB1, TBK1, and TLR3, and pathways Tuberculosis (hsa:05152), Primary Immunodeficiency (hsa:05340), and Influenza A (hsa:05164). These regions generally play an essential role in regulating antiviral innate immunity responses to foreign pathogens and in responding to many inflammatory diseases. We believe that to some extent, as an acute inflammatory disease, Covid-19 is also affected by these inborn errors of immunity. We hope that the identification of these rare genetic factors will provide new insights into the genetic architecture of Covid-19.

Inborn errors of immunity: Recent progress.

Recent advances in the field of inborn errors of immunity (IEIs) have been wide in scope, including progress in mechanisms of disease, diagnosis, and management. New gene defects affecting the immune response continue to be reported, as many as 26 in the year 2020. It was noted that the presentation of IEIs might not include recurrent infections in 9% of cases, and that current diagnostic methods can identify molecular causes in 92% of patients with severe combined immunodeficiency. Progress in immunopathogenesis explained mechanisms leading to symptoms of autosomal-recessive hyper-IgE syndrome. There was an emphasis on research in primary antibody deficiencies. The benefit of antibiotic prophylaxis to reduce the frequency of infections was demonstrated in these patients. The regimen of rituximab and azathioprine or mycophenolate was proven effective for chronic granulocytic interstitial pneumonia. The efficacy and adverse events of hematopoietic stem cell transplant in different IEI conditions were reported, as well as different strategies to improve outcomes, supporting its use in immunodeficiency and immunodysregulatory syndromes. The recent pandemic of coronavirus disease 2019 affected patients with IEIs, in particular those with deficiency in the interferon-mediated activation of the immune response. Initial data suggest that coronavirus disease 2019 vaccines might elicit anti-coronavirus disease 2019-neutralizing antibody responses in some patients with IEI conditions.

Clinical Course and Characteristics of COVID-19 in Patients With Inborn Errors of Immunity: A Retrospective Multicenter Experience From Iran (preprint)

Purpose: This study aimed to assess the effect of COVID-19 on patients with IEIs, the potentially at-risk population, regarding the clinical course, complications, severity, and outcomes. Methods This two-phase study was conducted on patients from three referral immunodeficiency centers in Iran. At phase one, 98 IEI patients with COVID-19 infection were evaluated by telephone follow-up (TFU). At phase two, the demographic, clinical, and laboratory records of clinically confirmed 33 IEI patients with COVID-19 infection were collected and analyzed. Results At phase one, 16.3% represented COVID-19 infection without any report of pediatric intensive care unit (PICU) admission or death. During the second phase, combined immunodeficiency (CID) (42.4%) and predominantly antibody deficiencies (PADs) (33.3%) were the predominant immune defects. Atopy (27.3%) and lung disorders (27.3%) were the frequent pre-existing comorbidities. Organomegaly (p=0.030) and renal disorders ( p=0.033 ) were significantly associated with the development of respiratory insufficiency. Cyanosis, tachypnea, intercostal retraction, and seizure were the chief complaints of patients who were more likely to progress respiratory insufficiency (p<0.05) , being admitted to the PICU (p<0.05) , and/or deceased (p<0.05) . Laboratory evaluation revealed a marked positive correlation between D-Dimer ( p=0.045 ), prothrombin time ( p=0.045 ), C-reactive protein ( p=0.041 ), proteinuria ( p=0.013 ), ferritin ( p=0.020 ), metabolic acidosis ( p=0.003 ), and troponin ( p=0.049 ) level with mortality. We detected a significant association between the chest X-ray pattern of COVID-19 infection with PICU admission (p=0.023) and death (p=0.046) . Conclusion In the current study, patients with CID and PAD were introduced as patients at high risk of COVID-19 infection, who may need extra protective and therapeutic measurements.

Differential interferon-α subtype immune signatures suppress SARS-CoV-2 infection (preprint)

Type I interferons (IFN-I) exert pleiotropic biological effects during viral infections, balancing virus control versus immune-mediated pathologies and have been successfully employed for the treatment of viral diseases. Humans express twelve IFN-alpha () subtypes, which activate downstream signalling cascades and result in distinct patterns of immune responses and differential antiviral responses. Inborn errors in type I IFN immunity and the presence of anti-IFN autoantibodies account for very severe courses of COVID-19, therefore, early administration of type I IFNs may be protective against life-threatening disease. Here we comprehensively analysed the antiviral activity of all IFN subtypes against SARS-CoV-2 to identify the underlying immune signatures and explore their therapeutic potential. Prophylaxis of primary human airway epithelial cells (hAEC) with different IFN subtypes during SARS-CoV-2 infection uncovered distinct functional classes with high, intermediate and low antiviral IFNs. In particular IFN5 showed superior antiviral activity against SARS-CoV-2 infection. Dose-dependency studies further displayed additive effects upon co-administered with the broad antiviral drug remdesivir in cell culture. Transcriptomics of IFN-treated hAEC revealed different transcriptional signatures, uncovering distinct, intersecting and prototypical genes of individual IFN subtypes. Global proteomic analyses systematically assessed the abundance of specific antiviral key effector molecules which are involved in type I IFN signalling pathways, negative regulation of viral processes and immune effector processes for the potent antiviral IFN5. Taken together, our data provide a systemic, multi-modular definition of antiviral host responses mediated by defined type I IFNs. This knowledge shall support the development of novel therapeutic approaches against SARS-CoV-2.

Infection-induced inflammation from specific inborn errors of immunity to COVID-19.

Inborn errors of immunity (IEIs) are a group of genetically defined disorders leading to defective immunity. Some IEIs have been linked to mutations of immune receptors or signaling molecules, resulting in defective signaling of respective cascades essential for combating specific pathogens. However, it remains incompletely understood why in selected IEIs, such as X-linked lymphoproliferative syndrome type 2 (XLP-2), hypo-immune response to specific pathogens results in persistent inflammation. Moreover, mechanisms underlying the generation of anticytokine autoantibodies are mostly unknown. Recently, IEIs have been associated with coronavirus disease 2019 (COVID-19), with a small proportion of patients that contract severe COVID-19 displaying loss-of-function mutations in genes associated with type I interferons (IFNs). Moreover, approximately 10% of patients with severe COVID-19 possess anti-type I IFN-neutralizing autoantibodies. Apart from IEIs that impair immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), SARS-CoV-2 encodes several proteins that suppress early type I IFN production. One primary consequence of the lack of type I IFNs during early SARS-CoV-2 infection is the increased inflammation associated with COVID-19. In XLP-2, resolution of inflammation rescued experimental subjects from infection-induced mortality. Recent studies also indicate that targeting inflammation could alleviate COVID-19. In this review, we discuss infection-induced inflammation in IEIs, using XLP-2 and COVID-19 as examples. We suggest that resolving inflammation may represent an effective therapeutic approach to these diseases.