Ayasoufi, Katayoun

Abstract Introduction Bone marrow (BM) is the primary immune organ responsible for stem cell maintenance. Neurotropic infections elicit sequestration of T cells within the BM. Changes of the BM niche during brain viral infections are unknown. Intracranial infection with the neurotropic Theiler’s Murine Encephalomyelitis Virus (TMEV) in C57BL/6 mouse is cleared by 30 days due to generation of an antigen-specific CD8 T cell response. Methods We used brain viral infection and injury models to test T cell responses against brain antigens in the bone marrow. Results We determined that 1-10% of CD8 T cells present in the sternal, femoral, and cranial BM were virus antigen-specific 7 days post intracranial infection. Over 70% of these CD8 T cells were tissue resident. We determined antigen-specific CD8 T cells were generated in the BM within 4 days of infection. Continuous treatment with FTY720, which sequesters T cells outside of the blood, did not eliminate antigen-specific CD8 T cells in any BM compartment. CD8 T cells in the BM established durable memory populations and were reactivated upon antigen reencounter. In the memory phase (200 days post brain TMEV infection), bone marrow resident CD8 T cell could be reactivated upon cognate peptide delivery. Such reactivation of antigen specific memory CD8 T cells caused an increase in lineage-, Sca-1+, ckit + (LSK) cells in the BM in a CD8 dependent manner. Similarly, injection of the model antigen AF488-conjugated OVA mixed with Poly IC into the brain recapitulated antigen specific CD8 T cell generation within the bone marrow and further demonstrated the antigen presenting cell involved in the response to be a CD103 expressing myeloid DC. We conclude that viral infections and inflammatory stimulation in the brain induce in situ effector and memory T cell responses within the BM which is associated with significant stem cell dysregulation. Conclusion Our data paves the way for crucial studies of BM resident antigen-specific CD8 T cells in health and disease. Funding Source NIH K99/R00 Topic Categories Viral Immunology (VIR)

Abstract Introduction Peripheral nervous system innervation of various organs has been associated with the development and maintenance of the immune system. Yet, the intricate details of thymic innervation remain less well-studied. Interestingly, various neurological insults including brain tumors, and neurotropic infections have been shown to have profound impacts on thymic size and cellularity and T cell development. Methods We used flow cytometry, confocal microscopy, neuro tracers, and genetic knockout mice to evaluate developing T cell-neuron interactions within the thymus. Results We have identified neuronal cell bodies within the thymus. These cells express neuronal markers such as NeuN and tyrosine hydroxylase and lack TEC identifiers, such as EpCAM, UEA-1, and Ly51. Thymic neurons can be infected with a neurotropic rabies vector, further cementing their neuronal identity. Considering the thymus consists mostly of T cells, we next investigated a potential interaction between T cells and thymic neurons. Interestingly, loss of T cell development results in a lack of thymic neuron development indicating T cell-neuron coregulation during development. However, thymic neurons can be recovered following a bone marrow transplant, suggesting the provision of a differentiation and/or survival signal for neurons provided by the developing T cells. Using knockout mice lacking the T cell lineage at various stages of development, we determined that TCR beta selection is required for the development of thymic neurons. Finally, we determined that a lack of transition from DN4 to DP severely diminishes the development of thymic neurons. Analysis of the publicly available bulk RNA-sequencing data comparing thymic DP to DN cell populations indicates the potential involvement of IL34 in neuronal development in the thymus. Conclusion We describe a novel population of neuronal cells within the thymus that interact with developing thymocytes to establish optimal thymic architecture. Funding Source NIH K99/R00 Topic Categories Neuroimmunology (NEUR)

Abstract Introduction Glioblastoma is an aggressive brain cancer with poor prognosis for which immunotherapies have fared poorly. In part, the failure in immunotherapies is attributed to the existence of severe local and systemic immunosuppression in GBM. We determined that majority of hallmark features of systemic immunosuppression were linked to immunosuppressive factors in serum. Our data indicate that serum of glioma-bearing mice harbors heightened levels of cell-free DNA (CF-DNA). Methods We evaluated the extent to which CF-DNA contributes to systemic T cell dysfunction in mouse models of GBM and GBM patient plasma samples. Results We determined that majority of hallmark features of systemic immunosuppression were linked to immunosuppressive factors in serum. Our data indicate that serum of glioma-bearing mice harbors heightened levels of cell-free DNA (CF-DNA). Removing CF-DNA from serum improves T cell responses while adding CF-DNA derived from serum of glioma-bearing subjects to healthy T cells directly inhibits their functions. We have also verified that CF-DNA is detectible in sera isolated from patients with GBM. When compared to healthy controls, GBM patients have higher quantities of CF-DNA is their plasma. Interestingly, our preliminary data implicates neutrophil NETosis as the likely source of CF-DNA in sera of GBM patients. Moreover, we stained GBM tumor sections with citrullinated histone 3 (cit-H3) to evaluate the extent of NETosis in GBM patients. We determined evidence of significant NETosis within patient brain tumors. Systemic immunosuppression is detrimental to the success of immune-modulating therapies and patient survival. By identifying and removing the source of systemic immunosuppression, we will enhance immune responses against the tumor likely improving patient survival. Conclusion Glioblastoma causes immune suppression outside of the brain via the released CF-DNA. Our studies in GBM patients and mouse models help develop strategies to reverse immune dysfunction and improve outcomes. Funding Source NIH K99/R00 Topic Categories Immune Mechanisms of Human Disease (HUM)

Abstract Introduction The anatomical locations of generating adaptive immune responses to neurotropic viruses are still being investigated. Skull bone marrow (BM) has recently been identified as a pivotal immune site that can sense and respond to a local insult in the brain. Yet, there is a lack of understanding of the role of skull BM during viral encephalitis. We hypothesized that the skull BM is an important niche for antiviral CD8 T cells priming, expansion, and maintenance during Theiler’s murine encephalomyelitis virus infection. Methods Using peptide:MHC tetramer analysis, we determined that antiviral CD8 T cells are primed in the skull BM in early infection, at time points comparable to cervical lymph nodes. Employing MHC class I conditional knockout mice generated by our research group, we inactivated H-2Kb and H-2Db class I molecules on discrete antigen-presenting cell types. Results We determined using these transgenic mice that viral antigen presentation on dendritic cells (DCs) and endothelial cells is essential for the generation of virus-specific T cells in skull BM during acute viral encephalitis. However, antigen presentation by DCs is not required for long-lived antiviral CD8 T cells that reside in skull BM. Moreover, the use of FTY720 to block lymphocyte migration diminished skull antiviral CD8 T cell numbers, suggesting that peripheral trafficking is required for generating skull antiviral CD8 T cells. Conclusion We present compelling evidence for the importance of skull BM as a responsive site that is highly suitable for rapid generation of antiviral CD8 T cells during acute viral encephalitis. Skull BM also serves as a reservoir for memory T cells, long after the resolution of a neurotropic virus infection. This work sheds light on the skull as a potential target for further modulation of the immune response to viral infections in the brain. Funding Source NIH grants R01 NS5103212 and RF1 NS122174 Topic Categories Viral Immunology (VIR)

Abstract Skull bone marrow (BM) is a recently identified site for immune activation responsive to CNS insults. The extent to which adaptive immunity is generated through skull BM is poorly understood. In this study, we evaluated how skull BM supports the early expansion of antiviral CD8 T cells during acute neurotropic virus infection. Virus antigen-specific CD8 T cells were rapidly identified in skull BM at a rate comparable to lymphoid compartments during acute Theiler’s murine encephalomyelitis viral (TMEV) infection. We therefore employed MHC class I conditional knockout mice and demonstrated the necessity of CD11c+ antigen-presenting cells (APCs) for the generation of various subsets of TMEV-specific CD8 T cells in skull BM. Importantly, the early expansion of skull BM-derived antiviral T cells was impeded by FTY720 treatment and restored upon shared circulation with a mouse exhibiting intact antigen presentation by CD11c+ APCs. Additionally, TMEV-specific CD8 T cells were retained in skull BM during both chronic CNS infection and long after infection has been resolved. Overall, we determined that skull BM responds to acute neurotropic viral infection through the rapid recruitment of virus-specific CD8 T cells primed in the periphery before serving as a reservoir for immunologic memory.

Abstract In many cancers, a major barrier to effective immunotherapy is the dominance of tumor-associated myeloid cells (TAMs), which establish a profoundly immunosuppressive tumor microenvironment (TME). This challenge is particularly pronounced in glioblastoma (GBM), where myeloid cells represent the predominant immune population and actively suppress antitumor immunity. Identifying targets that can reprogram TAMs from an immunosuppressive state toward a pro-inflammatory, antigen-presenting phenotype remains a critical unmet need. Here, we identify the voltage-gated proton channel Hv1 as an immune-restricted regulator of glioma-associated macrophage function. Hv1 is notable not only for its immune-specific expression but also for its established roles in central nervous system (CNS) pathologies, where Hv1 depletion alters microglial and macrophage polarization, reduces myeloid accumulation, dampens inflammatory cytokine production, and limits secondary tissue damage. However, Hv1’s role in shaping the GBM immune landscape—particularly in vivo—has remained poorly understood due to low Hvcn1 transcript abundance and the lack of reliable antibodies and genetic tools. Given the dominance of myeloid cells in GBM and their central role in tumor immune regulation, we sought to define Hv1 function within this highly immunosuppressive brain TME. Analysis of patient datasets revealed that elevated Hv1 expression correlates with poor clinical prognosis. Consistently, Hv1 loss significantly prolonged survival in multiple murine glioma models. Using in vivo two-photon imaging and spectral flow cytometry, we show that Hv1 depletion reprograms TAMs toward an anti-tumor phenotype characterized by enhanced tumor cell phagocytosis, improved antigen presentation, and increased T cell infiltration. By generating new Hv1 reporter and conditional mouse lines, we further demonstrate that tumor-associated microglia and infiltrating macrophages are the principal sources of Hv1 and markedly upregulate its expression in response to glioma. Notably, selective deletion of Hv1 in infiltrating macrophages phenocopied the survival benefit observed with global Hv1 loss. Mechanistically, using mass spectrometry and genetic models, we identify the Stimulator of Interferon Genes (STING) as a previously unrecognized binding partner of Hv1, placing Hv1 within the STING signaling pathway, a central regulator of innate and adaptive immune responses. Together, these findings fill a critical gap in understanding myeloid Hv1 function in GBM and identify Hv1 as a promising target for reprogramming the tumor immune microenvironment. Citation Format: Jiaying Zheng, Lingxiao Wang, Shunyi Zhao, Katayoun Ayasoufi, Meijie Wang, Praveen N. Pallegar, Peter R. Strege, Langni Liu, Yushan Wan, Wenjing Zhang, Emma N. Goddery, Manling Xie, Arthur Beyder, Aaron J. Johnson, Long-Jun Wu. Myeloid Hv1-STING axis tunes glioma immunity [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Brain Cancer; 2026 Mar 23-25; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2026;86(6_Suppl):Abstract nr A016.

Aging is a major risk factor for increased morbidity and mortality following acute respiratory virus infections. To elucidate the immune determinants underlying viral pathogenesis and delayed lung repair in the aged lung, a comprehensive time-course study was conducted. Single-cell RNA sequencing (scRNAseq) and high-dimensional flow cytometry were utilized to compare lungs from young and aged mice infected with influenza A virus (IAV). Aged hosts displayed diminished alveolar macrophage (AM) and dendritic cell (DC) but elevated monocyte-derived macrophage (MoM) and interstitial macrophage (IM) presence following infection. Additionally, enhanced accumulation of adaptive immune cells, including CD4+ tissue-resident helper (TRH) cells, CD8+ tissue-resident memory (TRM) cells, and a B cell subset resembling age-associated B cells, was observed in the memory phase. Pathway analysis revealed that elevated type I and II interferon (IFNα/γ) signaling, especially in MoM/IM subsets, distinguished the aged hosts from the young. Inhibition of IFNα/γ signaling after viral clearance improved long-term respiratory outcomes and reduced both IM and TRH populations in aged mice. These findings highlight the pivotal role of IFNα/γ signaling, likely within MoM/IM subsets, in driving the exuberant persistence of adaptive immune cells and chronic immunopathology in the aged lung following acute viral infection.

Aging is a major risk factor for increased morbidity and mortality following acute respiratory virus infections. To elucidate the immune determinants underlying viral pathogenesis and delayed lung repair in the aged lung, a comprehensive time-course study was conducted. Single-cell RNA sequencing (scRNAseq) and high-dimensional flow cytometry were utilized to compare lungs from young and aged mice infected with influenza A virus (IAV). Aged hosts displayed diminished alveolar macrophage (AM) and dendritic cell (DC) but elevated monocyte-derived macrophage (MoM) and interstitial macrophage (IM) presence following infection. Additionally, enhanced accumulation of adaptive immune cells, including CD4+ tissue-resident helper (TRH) cells, CD8+ tissue-resident memory (TRM) cells, and a B cell subset resembling age-associated B cells, was observed in the memory phase. Pathway analysis revealed that elevated type I and II interferon (IFNα/γ) signaling, especially in MoM/IM subsets, distinguished the aged hosts from the young. Inhibition of IFNα/γ signaling after viral clearance improved long-term respiratory outcomes and reduced both IM and TRH populations in aged mice. These findings highlight the pivotal role of IFNα/γ signaling, likely within MoM/IM subsets, in driving the exuberant persistence of adaptive immune cells and chronic immunopathology in the aged lung following acute viral infection.

Abstract Bone marrow is the primary immune organ responsible for stem cell maintenance and hematopoiesis. However, the contribution of the bone marrow niche for the generation of adaptive immune responses is less well-understood. We therefore assessed the capacity of virus antigen-specific CD8 T cells to be generated and expanded in bone marrow following acute neurotropic virus infection. Intracranial infection with the neurotropic Theiler’s Murine Encephalomyelitis Virus (TMEV) results in an acute infection in the C57BL/6 mouse which is cleared within 4 weeks post infection due to the generation of an antigen-specific CD8 T cell response against the immunodominant epitope VP2 121-130 . We determined that 1-10% of CD8 T cells present in the femoral, and sternal bone marrow were virus antigen-specific 5-7 days after intracranial TMEV infection. We determined that antigen-specific CD8 T cells were generated in the bone marrow with similar kinetics to that of conventional responses in the secondary lymphoid organs. Importantly, continuous treatment with FTY720, which sequesters T cells outside of the blood, did not eliminate antigen-specific CD8 T cells in the bone marrow compartment indicating generation within the bone marrow niche. Similarly, injection of Poly I:C admixed with fluorescently labeled ovalbumin into the brain generated a similar antigen-specific CD8 T cell response in the bone marrow indicating these responses occur following various brain insults. This model also identified the likely antigen presenting cell (APC) responsible for scavenging antigens from the brain and trafficking into the bone marrow as a migratory myeloid-derived APC. Moreover, following clearance of TMEV infection, CD8 T cells in the bone marrow established durable memory. Antigen-specific memory CD8 T cells in the bone marrow reactivated and expanded upon cognate antigen reencounter. Antigen-specific reactivation of memory CD8 T cells within the bone marrow caused a concurrent increase in Lineage-, Sca-1+, c-Kit+ (LSK) and CD11b+ MHCII+ myeloid cells. This increase in the LSKs and myeloid cells in the bone marrow niche was abrogated with CD8 T cell depletion. We conclude that brain viral infections induce in situ effector and memory T cell responses within the bone marrow compartment. Memory recall CD8 T cell responses induce niche dysregulation by expanding LSK cells and lead to an influx of MHCII+ myeloid cells. Our data pave the way for crucial studies of bone marrow resident antigen-specific CD8 T cells in health and diseases.

Abstract Description Peripheral nervous system innervation of various organs has been associated with the development and maintenance of the immune system. Various neurological insults including brain tumors induce thymic involution. Using flow cytometry and confocal microscopy, we identified a population of cells within the thymus that contained neuronal markers and morphology. Subsets expressed tyrosine hydroxylase, BIII tubulin and/or NeuN, distinguishing them from thymic epithelial cells. These cells do not express AIRE. Neuronal cell bodies and/or axonal processes were identified within the thymus. Using retrograde rabies vector neurotracers, we confirmed axonal connections and the identity of thymic neurons. To determine developmental T cell stages that support neuronal development, we evaluated RAG1/2 KO, TCRβ KO, TCRα KO, TCRγδ KO, CD4 KO, CD8 KO and OT-I and -II transgenics. RAG1/2 and TCRβ deficiency resulted in complete loss of thymic neurons. This is while TCRα KO, TCRγδ KO, CD4/8 KO and OT-II transgenics had normal thymic neuron development. Importantly, OT-I transgenics had a significant loss of neuron-like cells, indicating developing CD8 T cells pre-alpha arrangement control thymic innervation. Finally, introduction of healthy bone marrow into irradiated RAG KO mice can restore neuron development. To summarize, we describe a novel population of neuronal cells within the thymus that interact with developing thymocytes to establish optimal thymic innervation. Funding Sources R00NS117799 Topic Categories Neuroimmunology (NEUR)