Virus Infection Research Articles

Inhibition of mitophagy via the EIF2S1-ATF4-PRKN pathway contributes to viral encephalitis

IntroductionMitophagy, a selective form of autophagy responsible for maintaining mitochondrial homeostasis, regulates the antiviral immune response and acts as viral replication platforms to facilitate infection with various viruses. However, its precise role in herpes simplex virus 1 (HSV-1) infection and herpes simplex encephalitis (HSE) remains largely unknown. ObjectivesWe aimed to investigate the regulation of mitophagy by HSV-1 neurotropic infection and its role in viral encephalitis, and to identify small compounds that regulate mitophagy to affect HSV-1 infection. MethodsThe antiviral effects of compounds were investigated by Western blot, RT-PCR and plaque assay. The changes of Parkin (PRKN)-mediated mitophagy and Nuclear Factor kappa B (NFKB)-mediated neuroinflammation were examined by TEM, RT-qPCR, Western blot and ELISA. The therapeutic effect of taurine or PRKN-overexpression was confirmed in the HSE mouse model by evaluating survival rate, eye damage, neurodegenerative symptoms, immunohistochemistry analysis and histopathology. ResultsHSV-1 infection caused the accumulation of damaged mitochondria in neuronal cells and in the brain tissue of HSE mice. Early HSV-1 infection led to mitophagy activation, followed by inhibition in the later viral infection. The HSV-1 proteins ICP34.5 or US11 deregulated the EIF2S1-ATF4 axis to suppress PRKN/Parkin mRNA expression, thereby impeding PRKN-dependent mitophagy. Consequently, inhibition of mitophagy by specific inhibitor midiv-1 promoted HSV-1 infection, whereas mitophagy activation by PRKN overexpression or agonists (CCCP and rotenone) attenuated HSV-1 infection and reduced the NF-κB-mediated neuroinflammation. Moreover, PRKN-overexpressing mice showed enhanced resistance to HSV-1 infection and ameliorated HSE pathogenesis. Furthermore, taurine, a differentially regulated gut microbial metabolite upon HSV-1 infection, acted as a mitophagy activator that transcriptionally promotes PRKN expression to stimulate mitophagy and to limit HSV-1 infection both in vitro and in vivo. ConclusionThese results reveal the protective function of mitophagy in HSE pathogenesis and highlight mitophagy activation as a potential antiviral therapeutic strategy for HSV-1-related diseases.

Andrographolide Attenuates RSV-induced Inflammation by Suppressing Apoptosis and Promoting Pyroptosis after Respiratory Syncytial Virus Infection In Vitro.

Respiratory syncytial virus (RSV), which is the predominant viral pathogen responsible for causing acute lower respiratory tract infections in children, currently lacks specific therapeutic drugs. Despite andrographolide's demonstrated effectiveness against various viral infections, its effects on RSV infection remain unclear. In this study, RSV infection and andrographolide-intervened A549 cell lines were used. The virus load of RSV and the levels of IL-6 and IL-8 in the cell supernatant were quantified. The potential targets of andrographolide in the treatment of RSV-infected airway epithelial cells were analyzed using the Gene Expression Omnibus (GEO) database and the PharmMapper Database, and the changes in mRNA expression of these target genes were measured. To further illustrate the effect of andrographolide on the death pattern of RSV-infected airway epithelial cells, Annexin V-FITC/PI apoptosis assays and Western blotting were conducted. Andrographolide decreased the viral load and attenuated IL-6 and IL-8 levels in cell supernatant post-RSV infection. A total of 25 potential targets of andrographolide in the treatment of RSV-infected airway epithelial cells were discovered, and CASP1, CCL5, JAK2, and STAT1 were identified as significant players. Andrographolide noticeably suppressed the increased mRNA expressions of these genes post-RSV infection as well as IL-1β. The flow cytometry analysis demonstrated that andrographolide alleviated apoptosis in RSV-infected cells. Additionally, RSV infection decreased the protein levels of caspase-1, cleaved caspase-1, cleaved IL-1β, N-terminal of GSDMD, and Bcl-2. Conversely, andrographolide increased their levels. These results suggest that andrographolide may reduce RSV-induced inflammation by suppressing apoptosis and promoting pyroptosis in epithelial cells, leading to effective viral clearance.

Differential methylation patterns in paternally imprinted gene promoter regions in sperm from hepatitis B virus infected individuals

BackgroundHepatitis B virus (HBV) infection poses a substantial threat to human health, impacting not only infected individuals but also potentially exerting adverse effects on the health of their offspring. The underlying mechanisms driving this phenomenon remain elusive. This study aims to shed light on this issue by examining alterations in paternally imprinted genes within sperm.MethodsA cohort of 35 individuals with normal semen analysis, comprising 17 hepatitis B surface antigen (HBsAg)-positive and 18 negative individuals, was recruited. Based on the previous research and the Online Mendelian Inheritance in Man database (OMIM, https://www.omim.org/), targeted promoter methylation sequencing was employed to investigate 28 paternally imprinted genes associated with various diseases.ResultsBioinformatic analyses revealed 42 differentially methylated sites across 29 CpG islands within 19 genes and four differentially methylated CpG islands within four genes. At the gene level, an increase in methylation of DNMT1 and a decrease in methylation of CUL7, PRKAG2, and TP53 were observed. DNA methylation haplotype analysis identified 51 differentially methylated haplotypes within 36 CpG islands across 22 genes.ConclusionsThis is the first study to explore the effects of HBV infection on sperm DNA methylation and the potential underlying mechanisms of intergenerational influence of paternal HBV infection.

Elucidation of the solution structure of macrocyclic paritaprevir and exploration of its antitumor potential through molecular docking

Macrocyclic molecules have emerged as significant contenders in drug development and supramolecular chemistry. Paritaprevir is a 15-membered macrocycle approved for the treatment of chronic Hepatitis C virus infection. The structural flexibility inherent in paritaprevir enables the presentation of diverse conformational features in solutions, thereby influencing its binding pattern with proteins. In this paper, we investigated the structural characteristics of paritaprevir in protic solvents (methanol and trifluoroethanol) as well as an aprotic solvent (acetonitrile) by using experimental electronic circular dichroism spectra combined with density functional theory calculations. Our study reveals that paritaprevir can adopt different molecular conformations due to its flexible carbon chain and the solvent environment. Conformer B is particularly stable in polar solvents because of the planar hydrophobic interactions between the phenanthridine and methylpyrazine groups. Density functional theory calculations-assisted structural analyses further disclosed the weak noncovalent interactions within the stable conformations of paritaprevir. Molecular docking of paritaprevir on different cancer proteins showed that the macrocycle was highly selective against lymphoma, endometrial carcinoma, colorectal cancer, and breast cancer. This suggests that paritaprevir could potentially serve as a promising lead compound for drug design targeting these specific types of cancers. The comparison between the low energy conformation and pharmacophore conformation (docking conformation) indicates that conformer B is the primary pharmacophore conformation of paritaprevir, providing important macrocyclic structural characteristics for future macrocyclic drug development.

UBXN3B is crucial for B lymphopoiesis

The ubiquitin regulatory X (UBX) domain-containing proteins (UBXNs) are putative adaptors for ubiquitin ligases and valosin-containing protein; however, their invivo physiological functions remain poorly characterised. We recently showed that UBXN3B is essential for activating innate immunity to DNA viruses and controlling DNA/RNA virus infection. Herein, we investigate its role in adaptive immunity. We evaluated the antibody responses to multiple viruses and pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza in tamoxifen-inducible global and constitutive B cell-specific Ubxn3b knockout mice; quantified various immune populations, B lineage progenitors/precursors, B cell receptor (BCR) signalling and apoptosis by flow cytometry, immunoblotting and immunofluorescence microscopy. We also performed bone marrow transfer, single-cell and bulk RNA sequencing. Both global and B cell-specific Ubxn3b knockout mice present a marked reduction in small precursor B-II (>60%), immature (>70%) and mature B (>95%) cell numbers. Transfer of wildtype bone marrow to irradiated global Ubxn3b knockouts restores normal B lymphopoiesis, while reverse transplantation does not. The mature B population shrinks rapidly with apoptosis and higher pro and activated caspase-3 protein levels were observed following induction of Ubxn3b knockout. Mechanistically, Ubxn3b deficiency leads to impaired pre-BCR signalling and cell cycle arrest. Ubxn3b knockout mice are highly vulnerable to respiratory viruses, with increased viral loads and prolonged immunopathology in the lung, and reduced production of virus-specific IgM/IgG. UBXN3B is essential for B lymphopoiesis by maintaining constitutive pre-BCR signalling and cell survival in a cell-intrinsic manner. United States National Institutes of Health grants, R01AI132526 and R21AI155820.

Sociodemographic and clinical features related to hepatitis B virus infection among rejected blood donors in Luanda, Angola.

Hepatitis B virus (HBV) remains a public health concern. Blood donors screened for HBV surface antigen (HBsAg) along with aspartate transaminase (AST)/alanine aminotransferase (ALT) could play a key in providing safe blood products. We investigated the features related to HBV infection among rejected blood donors in Luanda, Angola. This was a cross-sectional study conducted with 164 rejected donors. Donors were screened for HBsAg from March to May 2022. Overall, 63.4% tested positive for HBV. The mean age of the HBV-positive (29.2 ± 8.02) was lower than the HBV-negative (33.9 ± 10.0) (p < 0.001). Donors between 20 and 40 years (odds ratio [OR]: 2.34, p = 0.045), females (OR: 1.40, p = 0.516), residents in urbanized areas (OR: 1.23, p = 0.530), low educational (OR: 1.54, p = 0.458), unemployed (OR: 1.65, p = 0.271), and unmarried (OR:1.41, p = 0.616) might be likely to contract HBV. AST/ALT ratio was higher in HBV-infected (2.07 ± 1.42) than in HBV-uninfected (1.90 ± 1.14). About 20% of HBV-positive were classified as having acute liver disease, while 80% with chronic liver disease, based on AST/ALT ratio. Age ranged from 20 to 40 years (OR: 1.97, p = 0.305), females (OR: 1.61, p = 0.557), donors from non-urbanized (OR: 1.69, p = 0.557), a low educational (OR: 1.64, p = 0.571), and unemployed donors (OR: 1.81, p = 0.289) were likely to develop chronic liver disease. Our findings indicated the failure of viral hepatitis control measures. Authorities should consider including HBV nucleic acid testing to ensure early identification of HBV in Angola.

Dysglycaemia in Ebola virus disease: a retrospective analysis from the 2018 to 2020 outbreak

BackgroundEbola virus disease (EVD) is associated with multisystem organ failure and high mortality. Severe hypoglycaemia is common, life-threatening, and correctable in critically ill patients, but glucose monitoring may be limited in EVD treatment units. MethodsWe conducted a retrospective review of patients admitted to EVD treatment units in Butembo and Katwa, Eastern DRC. Glucose measurements were done using a handheld glucometer at the bedside or using the Piccolo xpress Chemistry Analyzer on venous samples. Findings384 patients (median age 30 years (interquartile range, IQR, 20-45), 57% female) and 6,422 glucose measurements (median 11 per patient, IQR 4 to 22) were included in the analysis. Severe hypoglycaemia (≤2.2mmol/L) and hyperglycaemia (>10mmol/L) were recorded at least once during the ETU admission in 97 (25%) and 225 (59%) patients, respectively. A total of 2,004 infusions of glucose-containing intravenous solutions were administered to 302 patients (79%) with a median cumulative dose of 175g (IQR 100 to 411). The overall case fatality rate was 157/384 (41%) and was 2.2-fold higher (95%CI 1.3 to 3.8) in patients with severe hypoglycaemia than those without hypoglycaemia (p=0.0042). In a multivariable Cox proportional hazards model, periods of severe hypoglycaemia (adjusted hazard ratio (aHR) 6.2, 95%CI 3.2-12, p<0.0001) and moderate hypoglycaemia (aHR 3.0, 95%CI 1.9-4.8, p<0.0001) were associated with elevated mortality. InterpretationHypoglycaemia is common in EVD, requires repeated correction with intravenous dextrose solutions, and is associated with mortality. FundingThis study was not supported by any specific funding.

Hyper IgE Syndromes.

The Hyper IgE Syndromes are rare primary immunodeficiencies characterized by eczema, recurrent skin and respiratory infections and elevated serum IgE levels. Nowadays a geneticmolecular characterization is possible and allows the distinction in various monogenic pathologies, which share some clinical characteristics but also important differences. In addition to long-known STAT3 and DOCK8 gene mutations, in fact, also ZNF341, CARD11, ERBB2IP, IL6R and IL6ST genes mutations can cause the disease. The main clinical manifestations are represented by newborn rash, eczema similar to atopic dermatitis, bacterial and viral skin infections, cold abscesses, respiratory infections with possible pulmonary complications, allergies, gastrointestinal manifestations, malignancies and connective tissue abnormalities. Diagnosis is still a challenge because, especially in the early stages of life, it is difficult to distinguish from other pathologies characterized by eczema and high IgE, such as atopic dermatitis. Several scores and diagnostic pathways have been developed, but it is essential to seek a genetic diagnosis. Treatment is based on prevention and early treatment of infections, meticulous skincare, intravenous immunoglobulins and HSCT, which, in some HIES subtypes, can modify the prognosis. Prognosis is related to the affected gene, but also to early diagnosis, timely treatment of infections and early HSCT.

Repetition in social contacts: implications in modelling the transmission of respiratory infectious diseases in pre-pandemic and pandemic settings.

The spread of viral respiratory infections is intricately linked to human interactions, and this relationship can be characterized and modelled using social contact data. However, many analyses tend to overlook the recurrent nature of these contacts. To bridge this gap, we undertake the task of describing individuals' contact patterns over time by characterizing the interactions made with distinct individuals during a week. Moreover, we gauge the implications of this temporal reconstruction on disease transmission by juxtaposing it with the assumption of random mixing over time. This involves the development of an age-structured individual-based model, using social contact data from a pre-pandemic scenario (the POLYMOD study) and a pandemic setting (the Belgian CoMix study), respectively. We found that accounting for the frequency of contacts impacts the number of new, distinct, contacts, revealing a lower total count than a naive approach, where contact repetition is neglected. As a consequence, failing to account for the repetition of contacts can result in an underestimation of the transmission probability given a contact, potentially leading to inaccurate conclusions when using mathematical models for disease control. We, therefore, underscore the necessity of acknowledging contact repetition when formulating effective public health strategies.

Novel sialidase inhibitors suppress mumps virus replication and infection.

The prevalent human pathogen, mumps virus (MuV; orthorubulavirus parotitidis) causes various complications and serious sequelae, such as meningitis, encephalitis, deafness, and impaired fertility. Direct-acting antivirals (DAAs) targeting MuV which can prevent mumps and mumps-associated complications and sequelae are yet to be developed. Paramyxoviridae family members, such as MuV, possess viral surface hemagglutinin-neuraminidase (HN) protein with sialidase activity which facilitates efficient viral replication. Therefore, to develop DAAs targeting MuV we synthesized MuV sialidase inhibitors. It is proposed that the viral HN has a single functional site for N-acetylneuraminic acid (Neu5Ac) binding and sialidase activity. Further, the known MuV sialidase inhibitor is an analog of Neu5Ac-2,3-didehydro-2-deoxy-N-acetylneuraminic acid (DANA)-which lacks potency. DANA derivatives with higher MuV sialidase inhibitory potency are lacking. The MuV-HN-Neu5Ac binding site has a hydrophobic cavity adjacent to the C4 position of Neu5Ac. Exploiting this, here, we synthesized DANA derivatives with increasing hydrophobicity at its C4 position and created 3 novel sialidase inhibitors (Compounds 1, 2 and 3) with higher specificity for MuV-HN than DANA; they inhibited MuV replication step to greater extent than DANA. Furthermore, they also inhibited hemagglutination and the MuV infection step. The insight-that these 3 novel DANA derivatives possess linear hydrocarbon groups at the C4-hydroxyl group of DANA-could help develop highly potent sialidase inhibitors with high specificity for MuV sialidase, which may function as direct-acting MuV-specific antivirals.

Incidence of laboratory-confirmed influenza and RSV and associated presenteeism and absenteeism among healthcare personnel, Israel, influenza seasons 2016 to 2019.

BackgroundHealthcare personnel (HCP) are at high risk for respiratory infections through occupational exposure to respiratory viruses.AimWe used data from a prospective influenza vaccine effectiveness study in HCP to quantify the incidence of acute respiratory infections (ARI) and their associated presenteeism and absenteeism.MethodsAt the start and end of each season, HCP at two Israeli hospitals provided serum to screen for antibodies to influenza virus using the haemagglutination inhibition assay. During the season, active monitoring for the development of ARI symptoms was conducted twice a week by RT-PCR testing of nasal swabs for influenza and respiratory syncytial virus (RSV). Workplace presenteeism and absenteeism were documented. We calculated incidences of influenza- and RSV-associated ARI and applied sampling weights to make estimates representative of the source population.ResultsThe median age of 2,505 participating HCP was 41 years, and 70% were female. Incidence was 9.1 per 100 person-seasons (95% CI: 5.8-14.2) for RT-PCR-confirmed influenza and 2.5 per 100 person-seasons (95% CI: 0.9-7.1) for RSV illness. Each season, 18-23% of unvaccinated and influenza-negative HCP seroconverted. The incidence of seroconversion or RT-PCR-confirmed influenza was 27.5 per 100 person-seasons (95% CI: 17.8-42.5). Work during illness occurred in 92% (95% CI: 91-93) of ARI episodes, absence from work in 38% (95% CI: 36-40).ConclusionInfluenza virus and RSV infections and associated presenteeism and absenteeism were common among HCP. Improving vaccination uptake among HCP, infection control, and encouraging sick HCP to stay home are important strategies to reduce ARI incidence and decrease the risk of in-hospital transmission.

Epidemiology and risk stratification of young infants presenting to the emergency department with hypothermia.

Hypothermic infants are presumed to be at high risk for a serious bacterial infection (SBI) or herpes simplex virus (HSV) infection. In contrast to febrile infants, the emergency department (ED) management of hypothermic infants is variable in the absence of consensus guidelines, potentially resulting in low-value care and missed diagnoses. We investigated the diagnostic workup conducted for hypothermic infants in our academic pediatric ED, the incidence of SBI and HSV infection, and risk factors associated with infection. We conducted a single-center retrospective study of infants ≤90 days of age with a rectal temperature ≤36.5°C in the ED between 2013 and 2022. From their medical records, we abstracted the type(s) of testing each infant received in the ED and the diagnosis of SBI and HSV, analyzing characteristics associated with each. Of 1095 hypothermic infants identified, 402 (37%) underwent testing for SBI or HSV. Among these, 34/402 (8.5%) had an SBI or HSV. A minimum temperature below 36°C and hospital admission were characteristics associated with higher rates of infectious testing. Infants aged 29‒90 days, compared to 0‒28 days, were more likely to have a urinary tract infection (odds ratio 3.28, 95% confidence interval 1.47‒7.32). Hypothermic infants have slightly lower rates of SBI or HSV than febrile infants, for whom infectious studies are widely recommended, but still high enough to warrant an infectious workup in most cases. Further research is required to risk stratify hypothermic infants in the ED to standardize care and improve outcomes while optimizing resource utilization.

Weak association of Usutu virus and haemosporidian infection in birds collected in Germany

The Usutu Virus (USUV) is a mosquito-borne flavivirus originated in Africa. The virus circulates in Germany since 2010. It is primarily transmitted and maintained in the natural cycle by Culex mosquitoes and primarily affects birds, particularly Eurasian blackbird (Turdus merula), leading to significant mortality. Several studies have reported a high co-infection rate of European birds with both USUV and haemosporidians. Haemosporidians are blood parasites which maintain an enzootic life cycle with birds via different arthropod vectors. This study conducted screenings of birds from Germany received through a citizen's science project for both, USUV and haemosporidians between 2016 and 2021. The prevalence of USUV reached its peak in 2018, when it was first detected throughout most parts of Germany rather than being limited to localised hotspots. Subsequently, USUV prevalence consistently declined. On the other hand, the prevalence of haemosporidians initially declined between 2016 and 2019, but experienced a subsequent increase in the following years, exhibiting a more or less inverse pattern compared to the prevalence of USUV. In 2020, a statistically significant positive association between both pathogens was found, which was also detected across all years combined, indicating if at all a weak relationship between these pathogens.

Modeling hepatocyte apoptosis in chronic HCV infection with impulsive drug control

Chronic hepatitis C virus (HCV) infection is one of the leading life-threatening diseases owing to its non-cytopathic nature and scarcity of vaccines to combat. Hepatocyte apoptosis casts extensive impact in regulating chronic HCV infection. We propose a four dimensional deterministic model scheming the role of hepatocyte apoptosis and significance of HCV-specific CTL response in the intermediate stages of chronic HCV infection. Numerical simulation indicates that unregulated behavior of hepatocyte apoptosis triggers hepatocellular carcinoma and prolonged continuation of apoptosis induces liver damages. The system undergoes backward bifurcation and the value of the basic reproduction number R0=0.98<1 shows recurrence of infection. Local sensitivity analysis has been performed to reveal the most sensitive parameters responsible for the progression and mitigation of infection. In order to control of chronic HCV infection through pan-genotypic direct acting antiviral drugs (DAAs), impulsive differential equations are considered to study the effect of perfect drug adherence to both fixed and non-fixed dosing. For possible eradication of the chronic HCV infection, impulsive drug control suggests significant viral load reduction. The analytical results obtained for both non-impulsive and impulsive models are quantified biologically.

TCR-like bispecific antibodies toward eliminating infected hepatocytes in HBV mouse models

Therapeutics for eradicating hepatitis B virus (HBV) infection are still limited and current nucleos(t)ide analogs (NAs) and interferon are effective in controlling viral replication and improving liver health, but they cannot completely eradicate the hepatitis B virus and only a very small number of patients are cured of it. The TCR-like antibodies recognising viral peptides presented on human leukocyte antigens (HLA) provide possible tools for targeting and eliminating HBV-infected hepatocytes. Here, we generated three TCR-like antibodies targeting three different HLA-A2.1-presented peptides derived from HBV core and surface proteins. Bispecific antibodies (BsAbs) were developed by fusing variable fragments of these TCR-like mAbs with an anti-CD3ϵ antibody. Our data demonstrate that the BsAbs could act as T cell engagers, effectively redirecting and activating T cells to target HBV-infected hepatocytes in vitro and in vivo. In HBV-persistent mice expressing human HLA-A2.1, two infusions of BsAbs induced marked and sustained suppression in serum HBsAg levels and also reduced the numbers of HBV-positive hepatocytes. These findings highlighted the therapeutic potential of TCR-like BsAbs as a new strategy to cure hepatitis B.

Global epidemiology, natural history, maternal-to-child transmission, and treatment with DAA of pregnant women with HCV: a systematic review and meta-analysis

Pregnant women with hepatitis C virus (HCV) infection represent a special population in which treatment access remains limited despite its increasing prevalence. A reliable estimate of the burden and clinical outcomes of pregnant women with HCV infection is crucial for HCV elimination. We aimed to determine the prevalence, maternal-to-child transmission (MTCT), maternal and fetal complication rates, and direct acting antivirals (DAA) treatment outcomes of chronic HCV infection in pregnant women. We searched PubMed, EMBASE, Scopus, Web of Science from inception until March 1, 2024, for studies reporting on the prevalence, MTCT, complications of HCV infection, and treatment outcomes of DAA in pregnant women. Study quality was assessed using the Newcastle-Ottawa Scale. We performed subgroup analysis based on 9 variables to explore the source of heterogeneity in HCV prevalence. The PROSPERO registration number is CRD42024500023. From a total of 311,905,738 pregnant women from 333 studies, the pooled global seroprevalence of HCV in pregnant women was 2.6% (95% CI: 2.0-3.2, I 2=100%) which increased in patients with intravenous drug use and HIV. Majority of the HCV cases in pregnant women (75%) are diagnosed through universal screening. The pooled MTCT rate was 9.0% (95% CI: 6.6-11.7, I 2=79%), which was higher with HIV co-infection (OR: 3.1, 95% CI: 2.1-4.6, I 2=10%), but was not influenced by the mode of delivery or breastfeeding. Pregnant women with HCV infection had more maternal complications, including intrahepatic cholestasis, preterm delivery, and antepartum hemorrhage. Neonates of mothers with HCV had higher odds of being small for gestational age. The pooled rate of sustained virologic response (SVR12) among the 74 women treated with DAA during pregnancy was 98.4%, with no serious adverse events reported. HCV prevalence in pregnant women varies by geographic region and patient population, while MTCT occurs in almost one in ten viremic mothers. The incidence of both maternal and neonatal complications is significantly higher in patients with HCV infection. Limited data suggest that DAA are safe in pregnant women with HCV infection. None.

Selective autophagy receptor p62/SQSTM1 inhibits TBK1-IRF7 innate immune pathway in triploid hybrid fish

The production of type I interferon is tightly regulated to prevent excessive immune activation. However, the role of selective autophagy receptor SQSTM1 in this regulation in teleost remains unknown. In this study, we cloned the triploid fish SQSTM1 (3nSQSTM1), which comprises 1371 nucleotides, encoding 457 amino acids. qRT-PCR data revealed that the transcript levels of SQSTM1 in triploid fish were increased both in vivo and in vitro following spring viraemia of carp virus (SVCV) infection. Immunofluorescence analysis confirmed that 3nSQSTM1 was mainly distributed in the cytoplasm. Luciferase reporter assay results showed that 3nSQSTM1 significantly blocked the activation of interferon promoters induced by 3nMDA5, 3nMAVS, 3nTBK1, and 3nIRF7. Co-immunoprecipitation assays further confirmed that 3nSQSTM1 could interact with both 3nTBK1 and 3nIRF7. Moreover, upon co-transfection, 3nSQSTM1 significantly inhibited the antiviral activity mediated by TBK1 and IRF7. Mechanistically, 3nSQSTM1 decreased the TBK1 phosphorylation and its interaction with 3nIRF7, thereby suppressing the subsequent antiviral response. Notably, we discovered that 3nSQSTM1 also interacted with SVCV N and P proteins, and these viral proteins may exploit 3nSQSTM1 to further limit the host's antiviral innate immune responses. In conclusion, our study demonstrates that 3nSQSTM1 plays a pivotal role in negatively regulating the interferon signaling pathway by targeting 3nTBK1 and 3nIRF7.

Chronic HBV and HDV infection

About 0,5% of the population in Germany has a chronic hepatitis B virus (HBV) infection. Untreated, chronic HBV infection can progress to liver cirrhosis and hepatocellular carcinoma (HCC). If diagnosed early, antiviral therapy can effectively prevent liver disease progression, but a cure is currently hardly achievable. About 5% of those chronically infected with HBV are also co-infected with the hepatitis D virus (HDV). HBV/HDV co-infection leads to liver cirrhosis in approximately 50% of patients within 5-10 years. Since 2020, the cell entry inhibitor bulevirtide is available as a specific therapy for HBV/HDV co-infection.

Protein arginine methyltransferase 6 mediates antiviral immunity in plants.

Viral suppressor RNA silencing (VSR) is essential for successful infection. Nucleotide-binding and leucine-rich repeat (NLR)-based and autophagy-mediated immune responses have been reported to target VSR as counter-defense strategies. Here, we report a protein arginine methyltransferase 6 (PRMT6)-mediated defense mechanism targeting VSR. The knockout and overexpression of PRMT6 in tomato plants lead to enhanced and reduced disease symptoms, respectively, during tomato bush stunt virus (TBSV) infection. PRMT6 interacts with and inhibits the VSR function of TBSV P19 by methylating its key arginine residues R43 and R115, thereby reducing its dimerization and small RNA-binding activities. Analysis of the natural tomato population reveals that two major alleles associated with high and low levels of PRMT6 expression are significantly associated with high and low levels of viral resistance, respectively. Our study establishes PRMT6-mediated arginine methylation of VSR as a mechanism of plant immunity against viruses.

Sustained chronic inflammation and altered childhood vaccine responses in children exposed to Zika virus

Congenital Zika virus (ZIKV) infection leads to severe newborn abnormalities, but its long-term impact on childhood immunity is not well understood. This study aims to investigate the serum proteomics in children exposed to ZIKV during pregnancy to understand potential immunological consequences during early childhood. The study included ZIKV-exposed infants (ZEI) at birth (n=42) and children exposed to ZIKV (ZEC) at two years of age (n=20) exposed to ZIKV during pregnancy, as well as healthy controls. Serum proteomic analysis was performed on these groups to assess inflammation and immune profiles. Additionally, antibody titres against two common childhood vaccines, DTaP and MMR, were measured in healthy controls (n=50) and ZEC (n=92) to evaluate vaccine-induced immunity. Results showed elevated inflammation in ZEI with birth abnormalities. Among ZEC, despite most having normal clinical outcomes at two years, their serum proteomics indicated a bias towards Th1-mediated immune responses. Notably, ZEC displayed reduced anti-Diphtheria toxin and anti-Clostridium tetani IgG levels against DTaP and MMR vaccines. They also exhibited lower antibody titres particularly against Th2-biased DTaP vaccines, but not Th1-biased MMR vaccines. In conclusion, the study highlights the long-term immunological consequences of congenital ZIKV exposure. Heightened inflammation was observed in ZEI with abnormalities at birth, while ZEC maintained a chronic Th1-biased immune profile. The impaired response to Th2-biased vaccines raises concerns about lasting effects of ZIKV exposure on immune responses. Consequently, there is a need for continued longitudinal clinical monitoring to identify potential immune-related complications arising from prenatal exposure to ZIKV. This work was partially funded by the National Institute of Allergy and Infectious Diseases (NIAID) and National Institute of Dental and Craniofacial Research (NIDCR).