Biology subjects

Horwitz, M. S.

Publications and source records attributed to Horwitz, M. S..

10 recordsLinked to original sources

bioRxiv2026

STAT1 expression in myeloid cells restrains murine norovirus-induced hepatitis and fibrosis

Background & AimsRare cases of non-hepatotropic virus (NHV) infection in humans can cause severe hepatitis and even acute liver failure. Clinically relevant animal models of NHV-induced hepatitis are limited, contributing to the incomplete understanding of pathological mechanisms. Murine norovirus (MNV) elicits hepatosplenomegaly in mice lacking the antiviral immune effector Signal Transducer and Activator of Transcription-1 (STAT1), providing a model to investigate mechanisms of NHV-induced hepatic pathology. MethodsSTAT1-sufficient and -deficient (Stat1Het, Stat1KO) littermates infected intravenously (i.v.) with MNV strain CR6 were assessed for hepatic inflammation and viral burden. Cell types and molecular pathways associated with hepatic pathology in CR6-infected Stat1KO mice were identified by flow cytometry and RNAseq of liver tissue. The relative importance of hematopoietic vs non-hematopoietic expression of STAT1 in restricting CR6 replication and maintaining tissue homeostasis was assessed in bone marrow chimeras. ResultsMNV CR6 Stat1KO mice developed severe hepatitis with patchy hepatocellular necrosis and localized enrichment of CR6-infected myeloid cells, particularly macrophages. Gene set enrichment analysis (GSEA) of hepatic biopsies isolated from CR6-infected Stat1KO mice suggested dysregulated myeloid cell activation and indicated similarities between murine and human hepatic pathologies. STAT1 expression in hematopoietic cells was protective against hepatic viral dissemination, but hematopoietic STAT1-deficiency permitted persistent hepatic MNV infection, facilitating dysregulated myeloid cell activation and hepatic fibrosis. ConclusionsThese results demonstrate that the role of STAT1 extends beyond restricting MNV dissemination and suggest that STAT1-dependent regulation of myeloid cell activation prevents acute hepatic necroinflammation and secondary fibrosis. This model of MNV-induced hepatitis may prove valuable in elucidating mechanisms of rare clinical complications. SynopsisMechanisms driving acute hepatitis caused by non-hepatotropic viruses are not well understood. We describe a model of non-hepatotropic murine norovirus infection that reliably induces liver pathology and identify a requirement for STAT1 expression in myeloid cells to promote antiviral immunity and hepatic tissue protection. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/720966v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@4ef59forg.highwire.dtl.DTLVardef@1dfac58org.highwire.dtl.DTLVardef@1abe41dorg.highwire.dtl.DTLVardef@d59e9_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2026

Ultra-deep duplex sequencing reveals unique features of somatic evolution in the normal tissues of a family with Li-Fraumeni syndrome

Li-Fraumeni Syndrome (LFS) is caused by germline pathogenic variants in TP53 which predispose carriers to early onset cancer across multiple tissues. While genomically profiling those cancers has revealed factors contributing to their formation, little is understood about how LFS impacts clonal evolution in healthy tissues preceding cancer. Here, we use ultra-deep duplex sequencing (mean [~]15,000x depth) to investigate somatic mutation and selection in a family carrying the germline TP53 p.R181H pathogenic variant and a cohort of non-carrier controls. In blood samples, the germline variant is associated with more mutations in a panel designed to capture genomewide mutagenesis, and with reduced positive selection on somatic TP53 mutations, despite confounding by chemotherapy treatment in one individual. DNMT3A and TET2 mutations appear positively selected and GATA2 mutations negatively selected across the cohort, independent of the p.R181H status. Extensive multi-tissue sampling of 22 non-cancerous and 6 cancerous samples was also performed at autopsy in one individual with LFS who succumbed to esophageal cancer. Cross-tissue analysis reveals excess mutations in sun-exposed skin, esophagus and chronically-inflamed stomach tissue, and concordant mutations in the p.R248 hotspot of TP53 across most (18/28) tissue samples. Most somatic TP53 mutations in LFS that can be assessed for phase arose on the chromosomal copy lacking the p.R181H variant. Our study reveals how the germline p.R181H variant reshapes baseline somatic mutation and selection in normal tissues and highlights the importance of understanding early somatic evolution in LFS prior to cancer development and treatment.

cancer biology↗

bioRxiv2025

Helminth infection induces neuroimmune remodeling and clinical remission in a mouse model of multiple sclerosis

The central nervous system (CNS) is under constant immunosurveillance and influenced by immune-related effector molecules, including type 2-associated cytokines. Long-lasting type 2 immunity elicited by intestinal helminth infections can modify immune responses and wound repair locally and in peripheral tissues, but direct effects of helminth infection on the CNS are poorly understood. Here, we explore whether naturally-evoked type 2 immune responses can modify neuroimmune interactions for therapeutic gain in a mouse model of multiple sclerosis. Chronic infection with the helminth Trichinella spiralis (Ts) remodelled the neuroimmune landscape, including establishment of a robust population of CNS-resident T helper 2 cells, which subsequently minimized CNS inflammation and demyelination during experimental autoimmune encephalomyelitis (EAE). Clinical remission could be achieved with prophylactic or therapeutic infection, was Stat6-dependent, and adoptive transfer of Th2 cells promoted remission in the absence of overt infection. These findings highlight the potential for harnessing type 2 immunity to modify outcomes of neuroinflammation and neurodegeneration. SummaryFettig et al. demonstrate that infection with the helminth Trichinella spiralis elicits rapid recruitment and sustained presence of Th2 cells in the central nervous system where they modify microglia function and are implicated in resolving autoimmune-mediated paralysis and neuroinflammation.

immunology↗

bioRxiv2022

The dietary fiber guar gum ameliorates experimental autoimmune encephalomyelitis via attenuated Th1 activation and differentiation

Dietary fibers are potent modulators of immune responses that can restrain inflammation in multiple disease contexts. However, dietary fibers encompass a biochemically diverse family of carbohydrates, and it remains unknown how different fiber sources influence immunity. In a head-to-head comparison of four different high-fiber diets, we demonstrate a unique and potent ability of guar gum to reduce neuroinflammation in experimental autoimmune encephalomyelitis (EAE), a T cell-mediated mouse model of multiple sclerosis. CD4+ T cells from guar gum-fed mice have blunted Th1-skewing, reduced migratory capacity, and limited activation and proliferative capabilities. These changes are not explained by guar gum-specific alterations to the microbiota at the 16S rRNA level, nor by specific alterations in short chain fatty acids. These findings demonstrate specificity in the host response to fiber sources, and define a new pathway of fiber-induced CD4+ T cell immunomodulation that protects against pathologic neuroinflammation.

immunology↗

bioRxiv2022

Virus Infection Causes Intestinal Dysbiosis to Promote Type 1 Diabetes Onset

Autoimmune disorders like type 1 diabetes (T1D) are complex diseases caused by numerous factors including both genetic variance and environmental influences. Two such exogenous factors, intestinal microbial composition and enterovirus infection, have been independently associated with T1D onset in both humans and animal models. Since environmental factors rarely work in isolation, we examined the cross-talk between the microbiome and Coxsackievirus B4 (CVB4), an enterovirus that accelerates T1D onset in non-obese diabetic (NOD) mice. We demonstrate that CVB4-infection induced restructuring of the intestinal microbiome prior to T1D onset that was associated with thinning of the mucosal barrier, bacterial translocation to the pancreatic lymph node, and increased detection of circulating and intestinal commensal-reactive antibodies. Notably, the CVB4-induced change in community composition was strikingly similar to that of uninfected NOD mice that spontaneously developed diabetes, thus implying a mutual "diabetogenic" microbiome. Furthermore, fecal microbiome transfer (FMT) of the diabetogenic microbiota from CVB4-infected mice was sufficient to enhance T1D susceptibility in naive NOD recipients. These findings support a model whereby CVB infection disrupts the microbiome and intestinal homeostasis in a way that promotes activation of autoreactive immune cells and T1D.

microbiology↗

bioRxiv2022

Epstein-Barr virus infection promotes Th1-mediated disease in a humanized immune mouse model of multiple sclerosis

Infection with the human-tropic Epstein-Barr virus (EBV) is a strong risk factor for multiple sclerosis (MS), though the underlying mechanisms remain unclear. To investigate the immunomodulatory effects of latent EBV infection, we induced experimental autoimmune encephalomyelitis (EAE) in immunocompromised mice humanized with peripheral blood mononuclear cells (PBMCs) from individuals with or without a history of EBV infection and/or a diagnosis of relapsing MS. HuPBMC EAE mice generated from EBV seronegative healthy donors were less susceptible to developing severe clinical disease than EBV seropositive healthy donor and RRMS cohorts. Donor EBV seropositivity and RRMS led to a significant incremental increase in the number of brain and spinal cord infiltrating effector T cells, in the absence of viral reactivation, due to enhanced proliferation of donor T cells and reduced regulatory T cell expansion. The data indicate that a history of EBV infection, further compounded by a diagnosis of RRMS, promotes T cell-mediated disease in a novel humanized mouse model of MS. SUMMARYIn a novel humanized mouse model of multiple sclerosis (MS), donor history of Epstein-Barr virus (EBV) infection exacerbates disease severity by skewing the balance of effector and regulatory T cells in the brain and spinal cord. These results reveal an immunomodulatory mechanism by which latent EBV infection could predispose to the development of autoimmune disease.

immunology↗

bioRxiv2021

Age-associated B cells are critical for the control of latent gammaherpesvirus 68 infection

Age-associated B cells (ABCs; CD19+CD11c+T-bet+) are a unique population that are increased in an array of viral infections, though their role during latent infection is largely unexplored. Here, we use murine gammaherpesvirus 68 ({gamma}HV68) to demonstrate that ABCs remain elevated long-term during latent infection and express IFN{gamma} and TNF. Using a strain of {gamma}HV68 that is cleared following acute infection, we show that ABCs persist in the absence of latent virus, though their expression of IFN{gamma} and TNF is decreased. With a fluorescent virus we demonstrate that ABCs are infected with {gamma}HV68 at similar rates to other previously activated B cells. We find that mice without ABCs display defects in anti-viral IgG2a/c antibodies and are more susceptible to {gamma}HV68 reactivation when challenged with heterologous infection. Together, these results indicate that ABCs are a persistent effector subset during latent viral infection that restrains {gamma}HV68 reactivation.

immunology↗

bioRxiv2021

Gammaherpesvirus infection licenses age-associated B cells for pathogenicity in MS and EAE

While age-associated B cells (ABCs) are known to expand and persist following viral infection and during autoimmunity, their interactions are yet to be studied together in these contexts. Epstein-Barr virus (EBV) infection has long been implicated in multiple sclerosis (MS), and it is not known whether ABCs could play a role in mediating viral contribution to autoimmunity. Here, we show that the circulating ABC population is expanded in people with MS and that EBV infection and MS status differentially impact the circulating ABC phenotype. We then directly compared ABCs during viral infection and autoimmunity using mouse models of EBV, gammaherpesvirus 68 ({gamma}HV68), and MS, experimental autoimmune encephalomyelitis (EAE). We observed that splenic ABCs are expanded in a sex-biased manner during both latent virus infection and EAE, and each event drives the ABC population to opposing phenotypes. We have previously shown that latent{gamma} HV68 infection exacerbates EAE and here we show that mice lacking ABCs fail to display{gamma} HV68-enhanced disease. Collectively, these findings indicate that latent viral infection and central nervous system autoimmunity differentially impact the ABC population and suggests that viral infections such as EBV prime ABCs to contribute pathogenically in MS.

immunology↗

bioRxiv2021

Latent gammaherpesvirus exacerbates arthritis and requires age-associated B cells

Epstein-Barr virus (EBV) infection is associated with rheumatoid arthritis (RA) in adults, though the nature of the relationship remains unknown. Herein, we examine the contribution of viral infection to the severity of arthritis in mice. We provide the first evidence that latent gammaherpesvirus infection enhances clinical arthritis, modeling EBVs role in RA. Mice latently infected with a murine analog of EBV, gammaherpesvirus 68 ({gamma}HV68), develop more severe collagen-induced arthritis and a Th1-skewed immune profile reminiscent of human disease. We demonstrate that disease enhancement requires viral latency and is not due to active virus stimulation of the immune response. Age-associated B cells (ABCs) are associated with several human autoimmune diseases, including arthritis, though their contribution to disease is not well understood. Using ABC knockout mice, we provide the first evidence that ABCs are mechanistically required for viral enhancement of disease, thereby establishing that latent gammaherpesvirus infection stimulates ABCs to provoke arthritis. Conflict of interest statementThe authors have declared that no conflict of interest exists.

immunology↗

bioRxiv2021

Simultaneous Identification of Brain Cell Type and Lineage via Single Cell RNA Sequencing

Acquired mutations are sufficiently frequent such that the genome of a single cell offers a record of its history of cell divisions. Among more common somatic genomic alterations are loss of heterozygosity (LOH). Large LOH events are potentially detectable in single cell RNA sequencing (scRNA-seq) datasets as tracts of monoallelic expression for constitutionally heterozygous single nucleotide variants (SNVs) located among contiguous genes. We identified runs of monoallelic expression, consistent with LOH, uniquely distributed throughout the genome in single cell brain cortex transcriptomes of F1 hybrids involving different inbred mouse strains. We then phylogenetically reconstructed single cell lineages and simultaneously identified cell types by corresponding gene expression patterns. Our results are consistent with progenitor cells giving rise to multiple cortical cell types through stereotyped expansion and distinct waves of neurogenesis. Compared to engineered recording systems, LOH events accumulate throughout the genome and across the lifetime of an organism, affording tremendous capacity for encoding lineage information and increasing resolution for later cell divisions. This approach can conceivably be computationally incorporated into scRNA-seq analysis and may be useful for organisms where genetic engineering is prohibitive, such as humans.

genomics↗