High #risk of hypoxemic #COVID19 #pneumonia in #myasthenia gravis patients with type I IFN #autoantibodies

 

Abstract

Patients with myasthenia gravis (MG) may produce autoantibodies neutralizing type I interferons (AAN-I-IFN), which have been shown to underlie severe viral diseases, including critical COVID-19 pneumonia, in patients without MG. We studied an international cohort of 85 unvaccinated SARS-CoV-2-infected MG patients with no antiviral treatment. Hypoxemic pneumonia occurred in 48 of these patients, including 22 (45.8%) with AAN-I-IFN, which neutralized both IFN-α2 and IFN-ω in 14 (29.2%) patients. Six (16.2%) of the remaining 37 patients had AAN-I-IFN, which neutralized both IFN-α2 and IFN-ω in three patients. The risk of hypoxemic pneumonia was greater in MG patients with AAN-I-IFN neutralizing 10 ng/mL of both IFN-α2 and IFN-ω (odds ratio and 95% confidence interval (OR [95% CI]): 12.7 [2.1-78.9], p=0. 0010) or IFN-α2 at any dose (4.7 [1.5-15.0], p=0.0054) than in those without such autoantibodies. The risk of AAN-I-IFN production was much higher in MG patients than in the general population (28.9 [10.8-77.7], p=4.9x10-27). Fourteen patients had thymoma, which increased the risk of AAN-I-IFN (64% versus 27%, (OR [95% CI]: 5.6 [1.6-19.4], p=0.0050) and hypoxemic pneumonia (9.2 [1.9-44.2]; p=0.0019). Thymoma is, thus, associated with a higher risk of producing AAN-I-IFN, and these autoantibodies are associated with a higher risk of developing life-threatening COVID-19 pneumonia in patients with MG.

Competing Interest Statement

J.-L. C. is an inventor on patent application PCT/US2021/042741, filed July 22, 2021, submitted by The Rockefeller University and covering the diagnosis of susceptibility to, and the treatment of, viral disease, and viral vaccines, including COVID-19 and vaccine-associated diseases. None of the other authors has any conflict of interest to declare.

Funding Statement

The Laboratory of Human Genetics of Infectious Diseases is supported by the Howard Hughes Medical Institute, the Rockefeller University, the St. Giles Foundation, the National Institutes of Health (NIH) (R01AI163029), the National Center for Advancing Translational Sciences (NCATS), NIH Clinical and Translational Science Award (CTSA) program (UL1TR001866), the Fisher Center for Alzheimer s Research Foundation, the Meyer Foundation, the JPB Foundation, the Stavros Niarchos Foundation (SNF) as part of its grant to the SNF Institute for Global Infectious Disease Research at The Rockefeller University, the French Agence Nationale de la Recherche (ANR) under the France 2030 program (ANR-10-IAHU-01), the Integrative Biology of Emerging Infectious Diseases Laboratory of Excellence (ANR-10-LABX-62-IBEID), the French Foundation for Medical Research (FRM) (EQU202503020018), the ANR-RHU program ANR-21-RHUS-0008, ANR GENVIR (ANR-20-CE93-0003), ANR AABIFNCOV (ANR-20-CO11-0001) and ANR GenMISC (ANR-21-COVR-0039), AI2D (ANR-22-CE15-0046) projects, the European Union s Horizon 2020 research and innovation program under grant agreement no. 824110 (EASI-genomics), the HORIZON-HLTH-2021-DISEASE-04 program under grant agreement 101057100 (UNDINE), the Square Foundation, Grandir - Fonds de solidarite pour l enfance, the Fondation du Souffle, the SCOR Corporate Foundation for Science, the Battersea and Bowery Advisory Group; The French Ministry of Higher Education, Research, and Innovation (MESRI-COVID-19), William E. Ford, General Atlantic s Chairman and Chief Executive Officer, Gabriel Caillaux, General Atlantic s Co-President, Managing Director and Head of Business in EMEA, and the General Atlantic Foundation, Institut National de la Sante et de la Recherche Medicale (INSERM), REACTing-INSERM and Paris Cite University. For the collection and biobanking of MG samples, RLP and FT acknowledge support provided by the FP6 program (MYASTAID, LSHM-CT-2006-037833), FIGHT-MG (HEALTH-2009-242-210). N.L. was supported by the Swedish Research Council (no 2021-03118) and the Goran Gustafsson Foundation (no 2141 and 2247). TLV was supported by a Poste CCA-INSERM-Bettencourt (with the support of the Fondation Bettencourt-Schueller). P.B. was supported by the French Foundation for Medical Research (FRM, EA20170638020), the MD-PhD program of the Imagine Institute (with the support of the Fondation Bettencourt-Schueller), and a Poste CCA-INSERM-Bettencourt (with the support of the Fondation Bettencourt-Schueller).

Source: 

Link: https://www.medrxiv.org/content/10.64898/2026.03.27.26349525v1

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Intravenous #immunoglobulin #treatment for #longCOVID: a case report of clinical and immunological findings

 

Summary

A previously healthy 39-year-old man developed highly symptomatic post-COVID-19 condition (also known as long COVID) marked by cognitive dysfunction, disabling fatigue, and autonomic symptoms unresponsive to multiple multidisciplinary interventions. Given the presence of markedly elevated serum autoantibodies against G protein-coupled receptors, high-dose intravenous immunoglobulin therapy was initiated at 400 mg/kg per day for 5 consecutive days. After 4 weeks, a maintenance dose of 500 mg/kg was administered for 1 day, followed by two further maintenance cycles consisting of 500 mg/kg per day for 3 consecutive days, each given at 4-week intervals. In parallel, the patient underwent a cognitive stimulation intervention. Neurological symptoms were assessed with the Fatigue Assessment Scale and the WHO Disability Assessment Schedule 2.0, and the immunological profile was longitudinally analysed during intravenous immunoglobulin treatment. Fatigue scores normalised, neurocognitive performance returned to normal value, and quality of life improved after the first infusion and fully recovered within 1 year. Immunological profiling revealed the presence of an inverted CD4 to CD8 T-cell ratio that persisted during the whole follow-up. We also identified a CD8+ T cell–monocyte complex and spontaneous IFNγ release. Intravenous immunoglobulin therapy was associated with a significant reduction of these complexes, spontaneous IFNγ and TNF production, markers of endothelial inflammation, and circulating autoantibody titres. This patient provides exploratory evidence that high-dose intravenous immunoglobulin was associated with sustained clinical recovery from long COVID over 1 year of follow-up, accompanied by immunological changes consistent with modulation of post-viral immune dysregulation, including a reduction in pathogenic T cell–monocyte synapses. Although causal inference cannot be established from a single patient, these findings suggest that this cellular interaction can contribute to long COVID and that immunomodulation could represent a rational therapeutic approach to be evaluated in selected patients.

Source: 

Link: https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(26)00063-0/abstract?rss=yes

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Defining #influenza-specific B cells in #vaccine #responders, non-responders and influenza breakthrough #infections

 

Abstract

Although seasonal influenza vaccination programs are effective at a population level, our data from inactivated influenza vaccine (IIV) cohorts in years 2015-2022 reveal that 50-60% of individuals do not seroconvert following immunization. The underlying mechanisms of vaccine non-responsiveness are far from understood. In this study, we sought to define key determinants of optimal B cell immune responses elicited by seasonal influenza vaccination, and to explore why some individuals fail to elicit humoral immunity following immunization. Immune responses associated with seroconversion and vaccine failure from individuals immunized with IIVs were compared at cellular and molecular levels using single-cell transcriptomics. We analyzed HA-specific B cell immunity across vaccine-responders, breakthrough infections and patients hospitalized with acute influenza. Droplet-based single-cell RNA sequencing and VDJ-sequencing of influenza-specific B cells from stored PBMCs was performed using 10x Genomics. Our results show that atypical B cells are the major subset of B cell responses in vaccine non-responders on day 28 post-vaccination. Conversely, individuals who seroconvert had diverse B cell phenotypes. The use of recombinant influenza-specific HA probes allowed us to dissect expression patterns on influenza HA-specific B cells. We found that HA-specific B cells of vaccine non-responders for A/H1N1 and A/H3N2 components displayed elevated atypical-like markers (CD11c, FcRL-5) at baseline, compared to responders. Analysis of differentially expressed genes (DEGs) between responders and non-responders identified differential expression of HLA-DR, CD74, CD83, and CXCR3 genes. We subsequently demonstrated reduced frequencies of HLA-DR-, CD74- and CD83-expressing B cells in patients hospitalized with influenza, compared to healthy participants. Hospitalized influenza patients also had significantly higher proportions of atypical CD21-CD27- B cells. Overall, our data demonstrate an association between elevated frequencies of atypical-like B cells with both lack of seroconversion following immunization and severe influenza infection. These findings broaden our understanding of humoral immunity in influenza vaccination and infection, providing novel insights for vaccination strategies and design.

Competing Interest Statement

Katherine Kedzierska has received paid honoraria from Pfizer. Hayley McQuilten has a consultancy role for Ena Therapeutics

Funder Information Declared

NHMRC

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.03.19.710321v1

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Empiric #azithromycin alters the upper respiratory #microbiome and #resistome without anti-inflammatory benefit in #COVID19

 

Abstract

Azithromycin is a widely used antibiotic and was frequently used to treat hospitalized patients during the COVID-19 pandemic. The impact of empiric azithromycin use on the respiratory microbiome in patients with viral respiratory infections is unclear. Here we used longitudinal metatranscriptomics on nasal swabs from a prospective multicentre cohort of 1,164 patients hospitalized for COVID-19. We compared the upper respiratory microbiome, resistome and systemic immune response in patients treated with azithromycin (n = 366) with those who received no antibiotics (n = 474) or other antibiotics (n = 324). We found that azithromycin altered microbiome composition and increased the expression and relative proportion of macrolide/lincosamide/streptogramin (MLS) resistance genes. These changes occurred after 1 day of exposure and persisted for over a week. MLS resistance gene expression was associated with commensals and potential pathogens, while there were no differences in host inflammatory gene expression in blood and airways. This demonstrates that empiric azithromycin treatment impacts the upper respiratory microbiome and resistome without apparent anti-inflammatory benefit.

Source: 

Link: https://www.nature.com/articles/s41564-026-02285-8

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PA-X 122V broadly determines the #host shutoff #activity of #influenza A viruses

 

ABSTRACT

Multiple genes are involved in the pathogenicity of influenza A virus. Our previous study reported two naturally occurring amino acid mutations in the polymerase acidic (PA) protein as crucial determinants of the virulence of Eurasian avian-like H1N1 (EA H1N1) influenza viruses. PA-X, an accessory protein encoded by the PA gene, is thought to play a role in viral pathogenicity and regulation of host immune response, but its specific function remains unclear. In this study, we found that two genetically similar EA H1N1 influenza viruses, A/swine/Liaoning/FX38/2017 (FX38) and A/swine/Liaoning/SY72/2018 (SY72), induced significantly different suppression levels of host protein synthesis. The difference in host shutoff activity induced by PA-X protein was the key factor affecting the inhibition of host gene expression. Loss of PA-X expression significantly reduced its host shutoff activity, thereby enhancing host antiviral immune response. PA-X deficiency had no apparent effect on polymerase activity or replication capacity. We pinpointed a single residue 122V involved in the ability of PA-X to inhibit host gene expression and thereby modulate the host antiviral response. Notably, PA-X 122V was highly conserved among multiple subtypes of influenza A viruses and vital for maintaining the inhibitory effects on the host protein synthesis. Together, these findings demonstrate that the PA-X protein plays a major role in the suppression of host protein synthesis during influenza virus infection and elucidate the molecular mechanism by which the amino acid residue 122V in PA-X facilitates its suppression effects on host innate immune responses.

Source: 

Link: https://journals.asm.org/doi/full/10.1128/mbio.03433-25?af=R

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Resistance of #endothelial cells to #SARS-CoV-2 #infection in vitro

 

ABSTRACT

The secondary thrombotic/vascular clinical syndrome of COVID-19 suggests that SARS-CoV-2 infects the endothelium; however, robust in vitro infection of endothelial cells by various strains of SARS-CoV-2 remains to be demonstrated and continues to be debated. Here, we revisit the question of endothelial cell permissiveness to SARS-CoV-2 using isolated endothelial cells (from the lung, aorta, and endothelial cell progenitors), and additionally, to overcome limitations associated with cultured cells, using native endothelial cells within living precision cut human lung slices and single-cell RNA sequencing to track viral presence. Cellular infection in endothelial monocultures was determined using fluorescence imaging. Mediator release was measured by ELISA, and gene expression was assessed by RT-qPCR. Infection in lung slices was determined using single-cell RNA sequencing, capturing molecular identifiers that aligned to the SARS-CoV-2 viral genome (for lung slices). Each cultured endothelial cell type displayed functional viral responses by increased release of IP-10 when stimulated with Poly-IC (TLR3) or Imiquimod (TLR7/8). Compared to nasal epithelial cells, endothelial cells expressed low or undetectable levels of ACE2 and showed susceptibility to Ebola and Vesicular Stomatitis Virus glycoprotein-expressing pseudoviruses but not live SARS-CoV-2. Importantly, native endothelial cells within human lung slices displayed minimal infectability with SARS-CoV-2. To our knowledge, this is the first study to demonstrate that neither cultured nor native human endothelial cells are particularly, directly permissive to SARS-CoV-2, likely due to the lack of sufficient AEC2 expression. These observations confirm that the vascular inflammation and cardiovascular consequences of COVID-19 are largely an indirect result of paracrine inflammatory responses.

IMPORTANCE

SARS-CoV-2 is recognized not only for its acute effects and links with cardiovascular events but also for its ability to cause long COVID syndrome, which is now a major concern particularly since its long-term implications remain poorly understood. Revisiting endothelial cell permissivity to SARS-CoV-2 is therefore critical in this setting. We show that SARS-CoV-2, and several strains, do not infect cultured different types of endothelial cells cultured alone or native endothelial cells in situ in human lung tissue. Our findings are in line with the idea that vascular inflammation and thrombosis seen in COVID-19 are independent of direct endothelial cell infection and likely to be mediated by factors released by adjacent infected cells or circulating systemic inflammatory mediators. Our work also suggests that where viremia occurs, SARS-CoV-2 passes through the endothelium, facilitated by loss of barrier function because of local inflammation at the site of infection.

Source: 

Link: https://journals.asm.org/doi/full/10.1128/jvi.01205-25?af=R

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Rebalancing viral and immune #damage versus repair prevents #death from lethal #influenza #infection

 

Abstract

Maintaining tissue function while eliminating infected cells is fundamental, and inflammatory damage plays a major contribution to lethality after lung infection. We tested 50 immunomodulatory regimes to determine their ability to protect mice from lethal infection. Only neutrophil depletion soon after infection prevented death from influenza. This result suggests that the infected host passed an early tipping point after which limiting innate damage alone could not rescue lung function. We investigated treatments that could have efficacy when administered later in infection. We found that partial limitation of viral spread together with enhancement of epithelial repair, by interferon blockade or limiting CD8+ T cell–mediated killing of epithelial cells, reduced lethality. This finding highlights the importance of rebalancing repair and damage processes in the survival of pulmonary infections.

Source: 

Link: https://www.science.org/doi/10.1126/science.adr4635

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A #cattle-derived #human #H5N1 isolate suppresses innate #immunity despite efficient #replication in human respiratory #organoids

 

Abstract

The H5N1 high pathogenicity avian influenza virus (HPAIV) of clade 2.3.4.4b, which spreads globally via wild birds, has become a major public health concern because it can infect a variety of mammals, including humans. In 2024, infection of dairy cattle with H5N1 HPAIV clade 2.3.4.4b was confirmed in the United States, and subsequent human cases were reported. Although these viruses are highly pathogenic in animal models, human infections have generally been mild, revealing a striking discrepancy. Here, we characterized the cattle-derived human H5N1 isolate A/Texas/37/2024 (TX37-H5N1) using three-dimensional human respiratory organoids derived from induced pluripotent stem (iPS) cells. Despite efficient replication, TX37-H5N1 induced minimal interferon and inflammatory cytokine responses. Bulk and single-cell RNA sequencing revealed reduced STAT1-mediated transcriptional activity in TX37-H5N1-infected organoids compared to the historic H5N1 human isolate A/Vietnam/1203/2004. These findings suggest that TX37-H5N1 fails to trigger the strong innate responses, including robust cytokine production, that are typically associated with severe H5N1 disease and are thought to contribute to cytokine storm-medicated pathogenesis. This attenuated response may help explain the discrepancy between the high pathogenicity of TX37-H5N1 in animal models and its mild clinical presentation in humans. While zoonotic influenza risk is often assessed using cell lines or animal models, our study highlights the value of using human respiratory organoids to evaluate human-specific virus-host interactions. This platform provides a complementary tool for assessing the risk of emerging avian influenza viruses.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Japan Society for the Promotion of Science, JP24K09264

Japan Agency for Medical Research and Development, JP223fa627005, JP243fa627003h0003, JP24gm1810009, JP223fa627002, JP233fa827018

Japan Agency for Medical Research and Development, JP21gm1610005, JP22gm1610010

Japan Science and Technology Agency, JPMJMS2025

Takeda Science Foundation, https://ror.org/02y123g31

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.11.02.684669v1

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Maternal #Influenza A Virus #Infection Induces Antiviral and Immune Dysregulation in the #Placenta and #Fetus Without Vertical Transmission

 

Abstract

Influenza A virus (IAV) infection during pregnancy is associated with stillbirth and preterm birth, possibly by disrupting placental and fetal immunity. To investigate this, pregnant pigtail macaques were inoculated with IAV [A/California/07/2009 (H1N1)] and examined at necropsy 5 days post-infection (N=11) versus uninfected controls (N=16). Stillbirth occurred in 18% of infected pregnancies but not in controls. While vertical transmission was not observed, low levels of viral RNA were detected in two placentas. Maternal IAV infection was associated with increased placental IL-1β and IFN-β levels and an upregulated type I interferon and integrated stress transcriptional response. Fetuses exposed to IAV had greater frequencies of innate immune cells in lymph nodes and CD4+ T cells in lungs. These results suggest that placental and fetal immune environments undergo immune activation independent of the severity of maternal lung infection. Influenza vaccination during pregnancy may protect against potentially harmful effects on fetal development.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

National Institutes of Health, https://ror.org/01cwqze88, AI164588, AI176777, AI007509

Foundation for the National Institutes of Health, https://ror.org/00k86s890, OD010425, TR002318, GM007266, OD011123

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.10.06.675688v1

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Repeated #oral #exposure to #H5N1 #influenza virus in pasteurized #milk does not cause adverse responses to subsequent influenza #infection

 

Abstract

In March 2024, a highly pathogenic avian influenza H5N1 (HPAI) clade 2.3.4.4b virus was identified in US dairy cows, with spillover to cats, poultry, and humans. Up to 30% of commercial pasteurized milk tested contained viral genome copies. The impact of residual viral remnants on host immunity is unknown. Orally ingested proteins can stimulate gut-associated lymphoid tissues, potentially inducing tolerance and altering responses to later infection. We found that milk pasteurization fully inactivated pandemic H1N1 and bovine H5N1 influenza viruses yet preserved hemagglutinin (HA) protein integrity. In mice, repeated oral exposure to inactivated virus did not alter mortality after H5N1 virus challenge. Preliminary data showed that naïve mice exposed to improperly pasteurized milk containing live H5N1 virus developed lethal infection, whereas prior H1N1 infection conferred protection. Mice with preexisting H1N1 immunity remained protected when challenged with bovine H5N1 virus after exposure to H5N1 pasteurized in milk. These findings suggest that pasteurized milk containing inactivated H5N1 virus poses minimal health risks.

Source: Science Advances, https://www.science.org/doi/10.1126/sciadv.aeb3906

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#Autoantibodies in #longCOVID: a systematic #review

 

Summary

Post-COVID-19 condition (also known as long COVID) affects a substantial proportion of individuals who have been infected with SARS-CoV-2, profoundly affecting their daily lives and work. Diagnosis and prognosis of long COVID are complex and hindered by heterogeneous symptoms and the absence of validated biomarkers. This systematic review synthesises current evidence on the association between autoantibodies and long COVID, with the goal of evaluating their prognostic and diagnostic utility. Studies published in the PubMed and MEDLINE databases between Jan 1, 2020, and June 10, 2025, were considered. Study selection and quality assessment were done independently by two researchers. Of the 1113 publications screened, 44 studies met the inclusion criteria, with a total of 7571 participants, including 3372 individuals with long COVID. 31 (71%) studies reported an association between autoantibodies and long COVID; however, there was substantial heterogeneity in study design, type and timing of antibody measurements, and long COVID definitions. Several autoantibodies have been associated with long COVID occurrence, symptoms, and severity. Antinuclear antibodies, and autoantibodies targeting G protein-coupled receptors and chemokines, have emerged as potential biomarkers for aiding in the diagnosis, prognosis, and assessment of disease severity in long COVID. However, larger studies are needed to confirm the diagnostic and prognostic utility of these autoantibodies in the context of long COVID.

Source: Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00411-6/abstract?rss=yes

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Single-Cell #Network #Analysis Identifies CLEC4E as a Key Mediator of Proinflammatory mDC Responses in #Influenza #Infection

 

Abstract

The severity of influenza is often driven by an excessive host immune response rather than the virus itself, yet the key molecular drivers within specific immune cells remain poorly understood. While recent single-cell RNA sequencing studies have successfully identified immune populations involved, they have largely not identified the upstream drivers modulating their pro-inflammatory functions. Here we employed an integrated single-cell co-expression network to address this gap. Our analysis identified myeloid dendritic cells (mDCs) as central to pro-inflammatory response during infection. Through a multi-layered key driver analysis, we pinpointed C-type lectin, CLEC4E as a top candidate modulating this pathological inflammatory response. The role of CLEC4E was confirmed in an independent single-cell dataset from influenza-infected patients and further validated in vivo. Pharmacological inhibition of CLEC4E in a murine influenza model significantly reduced disease severity and lower viral titers in the lungs. This study not only clarifies that CLEC4E overexpression in mDCs contributes to pro-inflammatory signaling pathways influencing influenza severity but also shows the power of single-cell network approaches to uncover novel and robust therapeutic targets hidden within complex immune responses.

Competing Interest Statement

The M.S. laboratory has received unrelated funding support in sponsored research agreements from Phio Pharmaceuticals, 7Hills Pharma, ArgenX NV, Ziphius and Moderna.

Funder Information Declared

NIH Common Fund, R21AI149013, R01AI170112, U01AG088351

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.08.21.671587v1

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#SARS-CoV-2 #infection induces pro-fibrotic and pro-thrombotic #foam cell #formation

 

Abstract

COVID-19 and long COVID are characterized by a dysregulated immune response. However, the role of macrophages during viral infection is poorly defined. Here we demonstrate that SARS-CoV-2 infection results in increased macrophage numbers and extensive formation of enlarged lipid-laden macrophages or foam cells using humanized mice, rhesus macaques and post-mortem human lung tissue. Notably, infection by other coronaviruses tested, SARS-CoV-1, MERS-CoV and two bat coronaviruses (SHC014-CoV or WIV1-CoV), did not result in macrophage proliferation or foam cell formation. Foam cells in SARS-CoV-2-infected human lung tissue display a pro-fibrotic and pro-thrombotic phenotype as they are enriched for genes associated with platelet activation and aggregation, as well as extracellular matrix organization and collagen synthesis. After viral clearance, macrophage numbers remain elevated, and lung fibrosis and thrombi persist. Importantly, we show that pre-exposure prophylaxis or early treatment with a SARS-CoV-2 antiviral, EIDD-2801, prevents increases in macrophage cell numbers and foam cell formation, and reduces fibrosis markers. These observations highlight the contribution of macrophages to lung inflammation and tissue injury leading to the pulmonary fibrosis observed in COVID-19 patients.

Source: Nature Microbiology, https://www.nature.com/articles/s41564-025-02090-9

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The #pathogenicity and multi-organ proteomic profiles of #Mpox virus #infection in SIVmac239-infected rhesus #macaques

 

Abstract

Mpox poses a heightened risk of severe disease and mortality among individuals with HIV, yet the molecular mechanisms and immunopathology underlying multi-organ damage caused by the mpox virus (MPXV), particularly in the context of HIV co-infection, remain poorly understood. Here, we observe increased MPXV replication, more extensive skin lesions, and impaired humoral and cellular immune responses in SIV-MPXV co-infected rhesus macaques compared to those infected with MPXV alone. Multi-organ proteomic and phosphoproteomic analyses reveals upregulation of proteins involved in immune and inflammatory pathways in skin lesions and across multiple organs, especially in immune-related tissues. Abnormal activation of DNA replication and cell cycle signaling pathways, which may contribute to enhanced viral replication, is evident in both MPXV and SIV-MPXV co-infected groups. CDK4/6 may present a potential therapeutic target to suppress MPXV replication. These comprehensive proteomic datasets offer valuable insights into the pathogenesis of MPXV in the context of SIV co-infection and support ongoing efforts to mitigate the impact of mpox.

Source: Nature Communications, https://www.nature.com/articles/s41467-025-62919-z

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#MERS-related #coronavirus circulating in #pangolins exhibits strong fusogenicity in #human #cells and high sensitivity to fusion inhibitors

Highlights

• MjHKU4r-CoV-1 with high fusogenicity induces inflammatory responses in human cells

• 6-HB structure determination unveils MjHKU4r-S-mediated membrane fusion mechanism

• MjHKU4r-CoV-1 HR2 peptides exhibit potent activity by targeting viral HR1 domain

• Stapled peptide MjHKU4r-HR2P10 shows potent and broad-spectrum anti-CoV activity

Summary

Unlike preceding MERS-related coronaviruses, the recently identified MjHKU4r-CoV-1 strain can directly infect human cells. Nonetheless, its potential pathogenic attributes and underlying molecular mechanisms remain unclear. We find that MjHKU4r-CoV-1 induces significant inflammation, including interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α), and exhibits pronounced fusogenicity mediated by its spike (S) protein, leading to extensive syncytium formation. This suggests the possibility that MjHKU4r-CoV-1 possesses strong pathogenic potential in humans. Further, we successfully reveal the molecular mechanism of MjHKU4r-S-driven membrane fusion by crystallizing the six-helix bundle (6-HB) structure, a fusion apparatus composed of HR1 and HR2 domains. Concurrently, we develop a series of peptide-based fusion inhibitors that target the viral HR1 domain to impede the formation of viral 6-HB. Among these fusion inhibitors, a stapled peptide, MjHKU4r-HR2P10, shows the most potent inhibitory activity against MjHKU4r-CoV-1, MERS-CoV, SARS-CoV-2, and HCoV-OC43 infections at nanomolar level and thus holds considerable promise for further development as effective antiviral agents in clinic.

Source: Cell Reports Medicine, https://www.cell.com/cell-reports-medicine/fulltext/S2666-3791(25)00350-7?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2666379125003507%3Fshowall%3Dtrue

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Emerging highly pathogenic #H5N1 #influenza triggers fibrotic #remodeling in #human #airway organoids

ABSTRACT

The ongoing outbreak of highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b has affected at least 989 dairy herds across 17 states in the United States (U.S.) and resulted in 70 confirmed human infections, underscoring the urgent need to understand the pathogenesis and therapeutic interventions of emerging H5N1 viruses. In this study, we modelled infection with a highly pathogenic recombinant human A/Texas/37/2024 H5N1 (rHPh-TX H5N1) strain using human airway organoids (HAO) to investigate viral replication, innate immune response, infection-induced fibrogenesis, and potential therapeutic interventions. rHPh-TX H5N1 replicated efficiently in HAO, eliciting a robust interferon (IFN) response and pro-inflammatory cytokine production. Prolonged infection led to the accumulation of fibroblast-like cells surrounding infected regions, marked by increased alpha-smooth muscle actin (α-SMA) expression and upregulation of transforming growth factor-beta (TGF-β), indicative of fibroblast activation and extracellular matrix (ECM) remodelling. Compared to organoids infected with the pandemic A/California/04/09 H1N1 (pH1N1) strain, rHPh-TX H5N1 induced significantly higher expression of fibrosis-associated markers, including fibronectin (FN), collagen 1A (COL1A), collagen 3A (COL3A), metalloproteinases 2 and 9 (MMP2, and MMP9). Notably, the inhibition of Rho-associated coiled-coil-forming protein kinases (ROCK) signalling reduced fibrogenesis, with ROCK1 inhibition being more effective than ROCK2 inhibition. These findings highlight the potential of targeting ROCK signalling to mitigate H5N1-induced lung fibrosis, informing therapeutic strategies for severe influenza infections.

Source: Emerging Microbes and Infections, https://www.tandfonline.com/doi/full/10.1080/22221751.2025.2532684#abstract

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#ACE2-like enzymatic activity in #COVID19 #convalescents with persistent pulmonary symptoms associated with #immunoglobulin

ABSTRACT

Many difficult-to-understand clinical features characterize COVID-19 and post-acute sequelae of COVID-19 (PASC or long COVID [LC]). These can include blood pressure instability, hyperinflammation, coagulopathies, and neuropsychiatric complaints. The pathogenesis of these features remains unclear. The SARS-CoV-2 Spike protein receptor-binding domain (RBD) binds angiotensin converting enzyme 2 (ACE2) on the surface of host cells to initiate infection. We hypothesized that some people convalescing from COVID-19 may produce anti-RBD antibodies that resemble ACE2 sufficiently to have ACE2-like catalytic activity, that is, they are ACE2-like proteolytic abzymes that may help mediate the pathogenesis of COVID-19 and LC. In previous work, we showed that some people with acute COVID-19 had immunoglobulin-associated ACE2-like proteolytic activity, suggesting that some people with COVID-19 indeed produced ACE2-like abzymes. However, it remained unknown whether ACE2-like abzymes were seen only in acute COVID-19 or whether ACE2-like abzymes could also be identified in people convalescing from COVID-19. Here, we show that some people convalescing from COVID-19 attending a clinic for people with persistent pulmonary symptoms also have ACE2-like abzymes and that the presence of ACE2-like catalytic activity correlates with alterations in blood pressure in an exercise test.

IMPORTANCE

Patients who have had COVID-19 can sometimes have troublesome symptoms, termed post-acute sequelae of COVID-19 (PASC) or long COVID (LC), which can include problems with blood pressure regulation, gastrointestinal problems, inflammation, blood clotting, and symptoms like “brain fog.” The proximate causes for these problems are not known, which makes these problems difficult to treat definitively. We previously found that some acute COVID-19 patients make antibodies against SARS-CoV-2, the virus that causes COVID-19, that act like an enzyme, angiotensin converting enzyme 2 (ACE2). ACE2 normally helps regulate blood pressure and serves as the receptor for SARS-CoV-2 in the body. We show that patients convalescing from COVID-19 also make antibodies that act like ACE2 and that the presence of those antibodies correlates with problems in blood pressure regulation. The findings provide a new opening to potentially understanding the causes of LC, and so provide direction for the development of new treatments.

Source: mBio, https://journals.asm.org/doi/full/10.1128/mbio.01735-25?af=R

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No evidence of immune #exhaustion after repeated #SARS-CoV-2 #vaccination in vulnerable and healthy populations

Abstract

Frequent SARS-CoV-2 vaccination in vulnerable populations has raised concerns that this may contribute to T cell exhaustion, which could negatively affect the quality of immune protection. Herein, we examined the impact of repeated SARS-CoV-2 vaccination on T cell phenotypic and functional exhaustion in frail older adults in long-term care (n = 23), individuals on immunosuppressive drugs (n = 10), and healthy adults (n = 43), in Canada. Spike-specific CD4+ and CD8+ T cell levels did not decline in any cohort following repeated SARS-CoV-2 vaccination, nor did the expression of exhaustion markers on spike-specific or total T cells increase. T cell production of multiple cytokines (i.e. polyfunctionality) in response to the spike protein of SARS-CoV-2 did not decline in any cohort following repeated vaccination. None of the cohorts displayed elevated levels of terminally differentiated T cells following multiple SARS-CoV-2 vaccinations. Thus, repeated SARS-CoV-2 vaccination was not associated with increased T cell exhaustion in older frail adults, immunosuppressed individuals, or healthy adults.

Source: Nature Communications, https://www.nature.com/articles/s41467-025-60216-3

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Single-Cell #Analysis of Host Responses in #Bovine #Milk Somatic Cells (bMSCs) Following #HPAIV Bovine #H5N1 #Influenza Exposure

Abstract

The 2024 outbreak of highly pathogenic avian influenza virus (HPAIV) H5N1 in U.S. dairy cattle presented an unprecedented scenario where the virus infected bovine mammary glands and was detected in milk, raising serious concerns for public health and the dairy industry. Unlike previously described subclinical influenza A virus (IAV) infections in cattle, H5N1 infection induced severe clinical symptoms, including respiratory distress, mastitis, and abnormal milk production. To understand the host immune responses and changes, particularly in the mammary gland, we performed single-cell RNA sequencing analysis on bovine milk somatic cells (bMSCs) in vitro exposed to an H5N1 isolate from an infected dairy farm. We identified ten distinct cell clusters and observed a shift toward type-2 immune responses, characterized by T cells expressing IL13 and GATA3, and three different subtypes of epithelial cells based on the expression of genes associated with milk production. Our study revealed temporal dynamics in cytokine expression, with a rapid decline in luminal epithelial cells and an increase in macrophages and dendritic cells, suggesting a role in increased antigen presentation. While viral RNA was detected in bulk-exposed bMSC samples via qRT-PCR, no viral reads were observed in the scRNA-seq data, indicating that the immune responses captured may be due to exposure to viral components rather than productive infection. This research fills a critical gap in understanding the immune responses of bovine mammary glands to H5N1 exposure and highlights the need for further investigation into therapeutic strategies for managing such outbreaks.

Source: Viruses, https://www.mdpi.com/1999-4915/17/6/811

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Temperature-dependent #modulation of aberrant #influenza A virus #RNA #synthesis affects innate immune signaling

Abstract

Fever during influenza A virus (IAV) infection is triggered by the innate immune response. Various factors contribute to this response, including IAV mini viral RNAs (mvRNA), which trigger RIG-I signaling when their replication and transcription are dysregulated by template loops (t-loop). It is presently not well understood whether the fever response to IAV infection impacts subsequent viral replication and innate immune activation. Here we show that IAV infection at temperatures that simulate fever leads to increased mvRNA synthesis and antiviral signaling. Mathematical modeling and experimental analyses reveal that differential IAV nucleoprotein and RNA polymerase production underlies the increased mvRNA level. Moreover, at the higher infection temperature mvRNAs with dysregulating t-loops contribute most to the innate immune activation. We propose that fever during IAV infection can establish a positive feedback loop in which elevated aberrant RNA synthesis and innate immune activation may contribute to the dysregulation of cytokine production.

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.05.19.654939v1

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