Citations

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 BACKGROUND Intraductal papillary mucinous neoplasm (IPMN) is one of the two most common precursor lesions leading to the development of pancreatic ductal adenocarcinoma (PDA). IPMNs comprise a heterogeneous group of tumors with a wide range of grades and histotypes, and the emergence of single-cell RNA sequencing (RNA-seq) and multiplex digital spatial profiling have characterized unique cell populations, including dysplastic epithelial and immune cells, within the heterogeneous tumor microenvironment that carry signature gene expressions, which could be used as markers for disease progression. However, it is not clear on the heterogeneity of the epithelial and immune response of the evolution during progression of IPMN to PDA. OBJECTIVE Combining nuclear GSK-3β with oncogenic KRas mice (referred to as KNGC – KRas, nuclear GSK-3β, Cre) resulted in the development of IPMN. We have found that 4-week-old KNGC mice show progressive desmoplasia and ductal lesion development with increased M2-like macrophage infiltration. Interestingly, CX3CL1 (fractalkine), a chemokine involved in the recruitment of CX3CR1-expressing monocytes and M2-like macrophage conversion in various disease models is expressed by IPMN progenitor ductal cells. We aim to investigate expression and contribution of CX3CL1-CX3CL1 axis in the development and progression of IPMN. METHODS We utilized a newly generated CX3CL1-mCherry and well-established CX3CR1-GFP knockin/knockout mouse for crossbreeding with KNGC and KGC (KRas, GNas, Cre) for lineage tracing and function analysis by immunofluorescent staining, flow cytometry and CyTOF. RESULTS Both KNGC- and KGC-3LmCherry/+ mice harbor a large population of CX3CL1-mCherry/EPCAM+ epithelial cells as compared to 3LmCherry/+ and wildtype (WT) control mice. In KNGC and KGC mice, we show that there was a unique population of macrophages (CD45+ CD11b+ Ly6G- F4/80+ Ly6c- ) with significantly higher expression of CX3CR1 (CX3CR1Hi) that was not seen in WT mice. Significantly, Knockout of CX3CR1 in KNGC-3RGFP/GFP animals had a paucity of M2-like macrophages, reduced T regulatory cells (Tregs), substantially reduced desmoplasia and impaired development of IPMN. CONCLUSIONS The study provides important knowledge regarding the role of CX3CL1-CX3CR1 axis in recruitment and generation of M2-like macrophages, and their impact on the initiation of the immune/stroma microenvironment facilitating IPMN development. Further investigations using these models have the potential to identify new biomarkers for risk stratification and therapeutic intervention. Citation Format: Li Ding, Kaely Roeck, Easton Maeder, Cheng Zhang, Taylor Weiskittel, Esther Rodman, Mark Maynes, Bibo Zhu, Aaron Johnson, Jie Sun, Li Hu, Daniel Billadeau. Uncoupling CX3CL1-CX3CR1 Axis in IPMN Development Through Transgenic Mouse Models [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research—Emerging Science Driving Transformative Solutions; Boston, MA; 2025 Sep 28-Oct 1; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl_3):Abstract nr A064.

Abstract Aging is considered to be a major risk factor for host morbidity and mortality upon acute respiratory virus infections. To better elucidate the immune determinants of viral pathogenesis during aging, we chronological characterized lung cellular and molecular profiles following influenza virus (PR8) infection in young or aged mice till 60 days post infection. Time-course scRNAseq coupled with high dimensional flow cytometry enabled the description of changes in both immune and stromal compartment between young and aged hosts. We further zoomed into the myeloid compartment and focused on the dynamic responses of lung macrophages given their complex roles in viral pathogenesis, tissue repair and lung fibrosis. Enlarged Monocyte-derived Macrophage (MoM) population as well as decreased resident-Alveolar Macrophage (AM) population were observed in the aged mice when compared to those of the young mice. Despite the self-sustain nature of AMs during homeostasis, it has been reported that Ly6Chi monocytes can gain AM identity following severe lung damage like influenza virus infection. We found that the gain of AM identity from monocytes was abrogated in the aged hosts, which likely contributed to the age-associated impairment in lung recovery after influenzas virus infection. Additionally, trajectory analysis with scRNAseq allowed us to identify IFNα/γ signaling to be potential pathways contributing to such defect. This notion is also supported by elevated IFNγ level in BAL from the aged host during lung recovery. Our results thus have improved our understanding on the cellular and molecular mechanisms by which aged hosts exhibit severe diseases and delayed recovery after respiratory viral infection.

The relationship between diabetes and coronavirus disease 2019 (COVID-19) is bidirectional: Although individuals with diabetes and high blood glucose (hyperglycemia) are predisposed to severe COVID-19, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can also cause hyperglycemia and exacerbate underlying metabolic syndrome. Therefore, interventions capable of breaking the network of SARS-CoV-2 infection, hyperglycemia, and hyperinflammation, all factors that drive COVID-19 pathophysiology, are urgently needed. Here, we show that genetic ablation or pharmacological inhibition of mitochondrial pyruvate carrier (MPC) attenuates severe disease after influenza or SARS-CoV-2 pneumonia. MPC inhibition using a second-generation insulin sensitizer, MSDC-0602K (MSDC), dampened pulmonary inflammation and promoted lung recovery while concurrently reducing blood glucose levels and hyperlipidemia after viral pneumonia in obese mice. Mechanistically, MPC inhibition enhanced mitochondrial fitness and destabilized hypoxia-inducible factor–1α, leading to dampened virus-induced inflammatory responses in both murine and human lung macrophages. We further showed that MSDC enhanced responses to nirmatrelvir (the antiviral component of Paxlovid) to provide high levels of protection against severe host disease development after SARS-CoV-2 infection and suppressed cellular inflammation in human COVID-19 lung autopsies, demonstrating its translational potential for treating severe COVID-19. Collectively, we uncover a metabolic pathway that simultaneously modulates pulmonary inflammation, tissue recovery, and host metabolic health, presenting a synergistic therapeutic strategy to treat severe COVID-19, particularly in patients with underlying metabolic disease.

Abstract Aging has been shown to be one of the major risk factors for host morbidity and mortality following infections with respiratory viruses including influenza virus and SARS-CoV-2. The unique immune properties of the aged hosts not only influence pathogen clearance and tissue damage responses, but also modulate the pathogenesis of the long-term sequalae post acute viral clearance. Currently, the dynamics and features of mucosal immune responses following acute respiratory viral infections in the aged hosts remain to be fully elucidated. Here, we characterized the lung cellular and molecular profiles following influenza virus infection in young (~3-month-old) or aged (~24-month-old) mice with a chronological manner from acute to chronic phase. Using DNA-oligo-conjugated CD45 antibody and i.v. labeling, we were able to distinguish the unique responses of circulating vs lung-resident immune cells to influenza virus infection during aging. These responses were further validated by spectral flow cytometry analysis of the lung innate and adaptive immune cells. Further data analysis and integration are warranted for this unique large data set detailing the single cell molecular profiles of mucosal responses to influenza virus infection comparing young and aged hosts.

Abstract Fetal-derived tissue-resident macrophages exhibit stem cell-like features of self-renewal in adulthood to maintain macrophage population during homeostasis and/or various insults. However, little is known about the cellular and molecular mechanisms modulating proliferative and inflammatory fate decisions of tissue-resident macrophages in vivo. Here, we show that WNT-β-catenin signaling inhibited lung-resident alveolar macrophage (AM) self-renewal, while simultaneously promoted AM inflammatory activities in vitro and in vivo during influenza virus infection. Mechanistically, WNT engagement facilitated the binding of β-catenin with HIF-1α over its conventional binding partner TCF-4. Such a binding choice led to the elevated macrophage inflammation in a glycolysis-dependent manner, while inhibited AM self-renewal by causing mitochondrial damage and impairing oxidative phosphorylation. Thus, AM self-renewal and inflammatory activity are uncoupled by WNT-β-catenin signaling through HIF-1α-mediated cellular metabolic choice. Importantly, we showed that AM with high HIF-1α activity had limited proliferative capacity and produced inflammatory cytokines, while AM with low HIF-1α activity were highly proliferative and expressed genes associated with tissue repair function in vivo during influenza virus infection. In accordance, we demonstrated that AM proliferation and repopulation were needed for optimal lung repair following the clearance of influenza virus in the respiratory tract. Our results have revealed key mechanisms modulating macrophage fate choice between progeny production versus inflammatory effector activity, and subsequent effects on tissue inflammation and repair.

Abstract Alveolar macrophages (AMs) are the most abundant immune cells in the lung during homeostasis. AMs are critical for normal lung development, surfactant metabolism and host defense against various respiratory pathogens. Despite being terminally differentiated cells, AMs are able to proliferate and self-renew to maintain their compartment without the input of the hematopoietic system in the adulthood during homeostasis. However, the molecular and metabolic mechanisms modulating AM proliferative responses are still incompletely understood. Here we have investigated the metabolic regulation of AM proliferation and self-renewal. We found that mitochondrial metabolism is critical for AM proliferation in vitro and in vivo. Interestingly, inhibition of glucose uptake or fatty acid oxidation did not significantly impact AM proliferation. Rather, inhibition of the glutamine metabolic process abolished AM proliferation in vitro and in vivo following their partial depletion during influenza infection. We further demonstrated that glutamine metabolism was required for AM mitochondrial respiration. Our data indicate that glutamine is a critical substrate fueling mitochondrial metabolism required for AM proliferation. Our study is expected to shed light on the metabolic regulation of AM maintenance and repopulation during homeostasis and following acute respiratory viral infection.

Abstract Alveolar Macrophages (AMs) are unique innate immune cells that reside in the alveolar space and accommodate the ever-changing need of the lungs against internal and external challenges. During homeostasis, AMs maintained themselves through self-renewal without the need for input from adult hematopoietic stem cells. Currently, little is known about how aging influences AM dynamics, heterogeneity and self-renewal. To this end, we have performed single-cell RNA sequencing (scRNA-seq) on murine lung AMs (CD11+ Siglec F+) isolated from young (~8w) and aged (~2y) mice. We discovered that despite similar transcriptome in the proliferating cells, AMs from aged mice had reduced proliferation and self-renew ability than those from the young mice. AMs from aged mice also displayed elevated senescence markers such as p16, p21 and p53. Consistently, AMs from aged mice had reduced DNA repair ability, which could contribute to their impaired capacity to pass through the cell cycle checkpoints. Interestingly, AMs from aged mice also possessed reduced pro-apoptotic gene profile. Thus, we hypothesize that the reduced proliferation- and apoptosis-associated gene profiles in aged AMs may lead to the enhanced senescence-like phenotype in those cells. Further validation of the senescence-like phenotype of aged AMs and investigation of how they contribute to lung “inflammaging” are warranted.

Abstract Tissue-resident memory CD8+ T cells (TRM) share characteristics and core residency gene programs with tumor-infiltrating lymphocytes (TILs). However, the transcriptional, metabolic and epigenetic regulation of TRM and TIL differentiation, maintenance and function are largely undefined. Furthermore, it is unknown whether metabolic and epigenetic manipulations can be employed to promote TRM/TIL functional programs for cancer immunotherapy. Here we report a critical mechanism programming the mitochondrial and epigenetic regulation of TRM/TIL functionality in situ. We find that mouse and human TRM/TIL express the transcription factor BHLHE40 and the BHLHE40-associated gene signature. Bhlhe40 is specifically required for TRM and TIL development and poly-functionality. Local PD-1 signaling inhibits TIL Bhlhe40 expression, and Bhlhe40 is critical for TIL reinvigoration following anti-PD therapy. Mechanistically, Bhlhe40 sustains TRM/TIL mitochondrial fitness for the promotion of a functional epigenetic state. Building on these findings, we also identify an epigenetic and metabolic regimen that promotes TRM/TIL gene signatures associated with tissue residency and poly-functionality through in vitro T cell screening. Strikingly, this regimen empowers the anti-tumor activity of CD8+ T cells and possesses therapeutic potential even at an advanced tumor stage in mouse models. Our results provide mechanistic insights on the local regulation of TRM and TIL function, and offer a viable strategy for developing novel immunotherapeutic means for cancer.