Biology subjects

Hilligan, K. L.

Publications and source records attributed to Hilligan, K. L..

8 recordsLinked to original sources

bioRxiv2024

IFN-I signaling in type 2 conventional dendritic cells supports TH2 and T follicular helper differentiation after allergen immunization

Type 2 dendritic cells (DC2s) are essential for TH2 differentiation, but the signaling pathways involved in allergen sensing, DC activation and instruction of CD4+ T cell priming remain unclear. Previous transcriptomic analyses demonstrated a type-I interferon (IFN-I) signature in skin cDC2s following immunization with non-viable larvae of Nippostrongylus brasiliensis (Nb), house dust mite (HDM), and Schistosoma egg antigen (SEA). Blocking IFN-I signaling with anti-IFNAR1 (aIFNAR1) led to reduced TH2 cytokine responses to these antigens, however, the phenotype of cytokine-producing CD4+ T cells was not further defined. Here we show that conditional loss of IFNAR1 signaling in CD11c+ DCs significantly impaired effector TH2 and TFH CD4+ T cell responses to Nb. In vivo proliferation experiments demonstrated reduced numbers of highly divided CD4+ T cells in IFNAR1{Delta}CD11c mice compared to IFNAR1WT, with the highly divided population comprising both TH2 and TFH. Characterization of the cDC2 compartment by flow cytometry and bulk RNAseq demonstrated lower numbers of Nb+ cDC2s in the skin-draining LN and a reduced expression of Il15 and Il15Ra in IFNAR1{Delta}CD11c mice compared to IFNAR1WT, while expression of costimulatory molecules including CD80, CD86, Cd40 and Pdcd1lg2 (PD-L2) was not impaired. Therefore, IFN-I conditioning of skin cDC2s is necessary for their effective priming of CD4+ T cell responses to allergens, providing evidence for a role of tissue cytokines in driving cDC2 activation in a TH2 context.

immunology↗

bioRxiv2024

The inflammatory microenvironment of the lung at the time of infection governs innate control of SARS-CoV-2 replication

SARS-CoV-2 infection leads to vastly divergent clinical outcomes ranging from asymptomatic infection to fatal disease. Co-morbidities, sex, age, host genetics and vaccine status are known to affect disease severity. Yet, how the inflammatory milieu of the lung at the time of SARS-CoV-2 exposure impacts the control of viral replication remains poorly understood. We demonstrate here that immune events in the mouse lung closely preceding SARS-CoV-2 infection significantly impact viral control and we identify key innate immune pathways required to limit viral replication. A diverse set of pulmonary inflammatory stimuli, including resolved antecedent respiratory infections with S. aureus or influenza, ongoing pulmonary M. tuberculosis infection, ovalbumin/alum-induced asthma or airway administration of defined TLR ligands and recombinant cytokines, all establish an antiviral state in the lung that restricts SARS-CoV-2 replication upon infection. In addition to antiviral type I interferons, the broadly inducible inflammatory cytokines TNF and IL-1 precondition the lung for enhanced viral control. Collectively, our work shows that SARS-CoV-2 may benefit from an immunologically quiescent lung microenvironment and suggests that heterogeneity in pulmonary inflammation that precedes or accompanies SARS-CoV-2 exposure may be a significant factor contributing to the population-wide variability in COVID-19 disease outcomes.

immunology↗

bioRxiv2023

Pre-existing interferon gamma conditions the lung to mediate early control of SARS-CoV-2

Interferons (IFNs) are critical for anti-viral host defence. Type-1 and type-3 IFNs are typically associated with early control of viral replication and promotion of inflammatory immune responses; however, less is known about the role of IFN{gamma} in anti-viral immunity, particularly in the context of SARS-CoV-2. We have previously observed that lung infection with attenuated bacteria Mycobacterium bovis BCG achieved though intravenous (iv) administration provides strong protection against SARS-CoV-2 (SCV2) infection and disease in two mouse models. Assessment of the pulmonary cytokine milieu revealed that iv BCG induces a robust IFN{gamma} response and low levels of IFN{beta}. Here we examined the role of ongoing IFN{gamma} responses due to pre-established bacterial infection on SCV2 disease outcomes in two murine models. We report that IFN{gamma} is required for iv BCG induced reduction in pulmonary viral loads and that this outcome is dependent on IFN{gamma} receptor expression by non-hematopoietic cells. Further analysis revealed that BCG infection promotes the upregulation of interferon-stimulated genes (ISGs) with reported anti-viral activity by pneumocytes and bronchial epithelial cells in an IFN{gamma}-dependent manner, suggesting a possible mechanism for the observed protection. Finally, we confirmed the importance of IFN{gamma} in these anti-viral effects by demonstrating that the recombinant cytokine itself provides strong protection against SCV2 challenge when administered intranasally. Together, our data show that a pre-established IFN{gamma} response within the lung is protective against SCV2 infection, suggesting that concurrent or recent infections that drive IFN{gamma} may limit the pathogenesis of SCV2 and supporting possible prophylactic uses of IFN{gamma} in COVID-19 management.

immunology↗

bioRxiv2022

Helminth exposure protects against murine SARS-CoV-2 infection through macrophage dependent T cell activation

Helminth endemic regions report lower COVID-19 morbidity and mortality. Here, we show that lung remodeling from a prior infection with a lung migrating helminth, Nippostrongylus brasiliensis, enhances viral clearance and survival of human-ACE2 transgenic mice challenged with SARS-CoV-2 (SCV2). This protection is associated with a lymphocytic infiltrate including an increased accumulation of pulmonary SCV2-specific CD8+ T cells and anti-CD8 antibody depletion abrogated the N. brasiliensis-mediated reduction in viral loads. Pulmonary macrophages with a type-2 transcriptional signature persist in the lungs of N. brasiliensis exposed mice after clearance of the parasite and establish a primed environment for increased antigen presentation. Accordingly, depletion of macrophages ablated the augmented viral clearance and accumulation of CD8+ T cells driven by prior N. brasiliensis infection. Together, these findings support the concept that lung migrating helminths can limit disease severity during SCV2 infection through macrophage-dependent enhancement of anti-viral CD8+ T cell responses. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/515832v1_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@1c17a22org.highwire.dtl.DTLVardef@13967b3org.highwire.dtl.DTLVardef@1c723a7org.highwire.dtl.DTLVardef@f5e038_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2022

Evaluation of endogenous and therapeutic 25-hydroxycholesterols in murine models of pulmonary SARS-CoV-2 infection

Oxysterols (i.e., oxidized cholesterol species) have complex roles in biology. 25-hydroxycholesterol (25HC), a product of activity of cholesterol-25-hydroxylase (CH25H) upon cholesterol, has recently been shown to be broadly antiviral, suggesting therapeutic potential against SARS-CoV-2. However, 25HC can also amplify inflammation and tissue injury and be converted by CYP7B1 to 7,25HC, a lipid with chemoattractant activity via the G protein-coupled receptor, EBI2/GPR183. Here, using in vitro studies and two different murine models of SARS-CoV-2 infection, we investigate the effects of these two oxysterols on SARS-CoV-2 pneumonia. We show that while 25HC and enantiomeric-25HC are antiviral in vitro against human endemic coronavirus-229E, they did not inhibit SARS-CoV-2; nor did supplemental 25HC reduce pulmonary SARS-CoV-2 titers in the K18-human ACE2 mouse model in vivo. 25HC treatment also did not alter immune cell influx into the airway, airspace cytokines, lung pathology, weight loss, symptoms, or survival but was associated with increased airspace albumin, an indicator of microvascular injury, and increased plasma pro-inflammatory cytokines. Conversely, mice treated with the EBI2/GPR183 inhibitor NIBR189 displayed a modest increase in lung viral load only at late time points, but no change in weight loss. Consistent with these findings, although Ch25h was upregulated in the lungs of SARS-CoV-2-infected WT mice, lung viral titers and weight loss in Ch25h-/- and Gpr183-/- mice infected with the beta variant were similar to control animals. Taken together, endogenous 25-hydroxycholesterols do not significantly regulate early SARS-CoV-2 replication or pathogenesis and supplemental 25HC may have pro-injury rather than therapeutic effects in SARS-CoV-2 pneumonia.

immunology↗

bioRxiv2022

Rapid GPR183-mediated recruitment of eosinophils to the lung after Mycobacterium tuberculosis infection

Influx of eosinophils into the lungs is typically associated with type-II responses during allergy, fungal and parasitic infections. However, we previously reported that eosinophils accumulate in lung lesions during type-I inflammatory responses to Mycobacterium tuberculosis (Mtb) in humans, macaques, and mice where they contribute to host resistance. Here we show eosinophils migrate into the lungs of macaques and mice as early as one week after Mtb-exposure. In mice this influx was CCR3 independent and instead required cell-intrinsic expression of the oxysterol-receptor GPR183, which is highly expressed on human and macaque eosinophils. Murine eosinophils interacted directly with bacilli-laden alveolar macrophages, which upregulated the oxysterol-synthesizing enzyme Ch25h, and eosinophil recruitment was impaired in Ch25h deficient mice. Our findings show that eosinophils are among the first cells from circulation to sense and respond to Mtb infection of alveolar macrophages and reveal a novel role for GPR183 in the migration of eosinophils into lung tissue. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/480919v1_ufig1.gif" ALT="Figure 1"> View larger version (105K): org.highwire.dtl.DTLVardef@e8cd29org.highwire.dtl.DTLVardef@1f5769borg.highwire.dtl.DTLVardef@3dce9borg.highwire.dtl.DTLVardef@1c75587_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSIn mice and macaques eosinophils accumulate early in Mtb-infected lungs preceding neutrophils Eosinophils interact with Mtb-infected cells in the alveoli in mice Early pulmonary eosinophil migration occurs independently of CCR3 in mice Early lung migration in mice requires Ch25h and eosinophil-intrinsic GPR183 expression

immunology↗

bioRxiv2021

Intravenous administration of BCG protects mice against lethal SARS-CoV-2 challenge

Early events in the host response to SARS-CoV-2 are thought to play a major role in determining disease severity. During pulmonary infection, the virus encounters both myeloid and epithelioid lineage cells that can either support or restrict pathogen replication as well as respond with host protective versus detrimental mediators. In addition to providing partial protection against pediatric tuberculosis, vaccination with bacille Calmette-Guerin (BCG) has been reported to confer non-specific resistance to unrelated pulmonary pathogens, a phenomenon attributed to the induction of long-lasting alterations within the myeloid cell compartment. Here we demonstrate that prior intravenous, but not subcutaneous, administration of BCG protects human-ACE2 transgenic mice against lethal challenge with SARS-CoV-2 and results in reduced viral loads in non-transgenic animals infected with an alpha variant. The observed increase in host resistance was associated with reductions in SARS-CoV-2-induced tissue pathology, inflammatory cell recruitment and cytokine production that multivariate analysis revealed to be only partially related to diminished viral load. We propose that this protection stems from BCG-induced alterations in the composition and function of the pulmonary cellular compartment that impact the innate response to the virus and the ensuing immunopathology.

immunology↗

bioRxiv2021

The skin environment controls local dendritic cell differentiation and function through innate IL-13

The signals driving the adaptation of type-2 dendritic cells (DC2s) to diverse peripheral environments are not well understood. We show that the development of CD11blow migratory DC2s, a DC2 population unique to the dermis, requires STAT6- and KLF4-dependent IL-13 signaling, whereas DC2s in lung and small intestine are STAT6-independent. Dermal IL-13 is mostly derived from innate lymphoid cells expressing a resting ICOS+ KLRG1-ST2-phenotype. Analysis of public datasets indicates that human skin DC2s also express an IL-4/IL-13 gene signature compared to blood or spleen, suggesting a similar developmental pathway in mice and humans. In the absence of IL-13 signaling, dermal DC2s are stable in number but remain CD11bhi and show defective activation in response to allergen with diminished ability to support IL-4+ GATA3+ Th development, whereas anti-fungal IL-17+ ROR{gamma}t+ responses are increased. Thus, steady-state IL-13 fosters a non-inflammatory and pro-allergic environment in healthy skin via conditioning of local DC2s.

immunology↗