Biology subjects

Kreamalmeyer, D.

Publications and source records attributed to Kreamalmeyer, D..

6 recordsLinked to original sources

bioRxiv2023

Type I IFN signaling in the absence of IRGM1 promotes M. tuberculosis replication in immune cells by suppressing T cell responses

Polymorphisms in the IRGM gene are associated with susceptibility to tuberculosis in humans. A murine ortholog of Irgm, Irgm1, is also essential for controlling Mycobacterium tuberculosis (Mtb) infection in mice. Multiple processes have been associated with IRGM1 activity that could impact the host response to Mtb infection, including roles in autophagy-mediated pathogen clearance and expansion of activated T cells. However, what IRGM1-mediated pathway is necessary to control Mtb infection in vivo and the mechanistic basis for this control remains unknown. We dissected the contribution of IRGM1 to immune control of Mtb pathogenesis in vivo and found that Irgm1 deletion leads to higher levels of IRGM3-dependent type I interferon signaling. The increased type I interferon signaling precludes T cell expansion during Mtb infection. The absence of Mtb-specific T cell expansion in Irgm1-/- mice results in uncontrolled Mtb infection in neutrophils and alveolar macrophages, which directly contributes to susceptibility to infection. Together, our studies reveal that IRGM1 is required to promote T cell-mediated control of Mtb infection in neutrophils, which is essential for the survival of Mtb-infected mice. These studies also uncover new ways type I interferon signaling can impact TH1 immune responses.

immunology↗

bioRxiv2023

Autophagy functions in lung macrophages and dendritic cells to suppress TH17 responses and neutrophil accumulation during allergic airway inflammation

Asthma affects 260 million people worldwide, with severe asthma cases that are associated with TH17/TH1 responses and neutrophil dominated inflammation being the most difficult to treat due to corticosteroid insensitivity. Single nucleotide polymorphisms in the ATG5 gene, which encodes for a protein required for the cellular recycling process of autophagy, are associated with higher risk for developing severe asthma. However, the role for ATG5 during allergic inflammation remains mostly unknown. We have identified an autophagy-dependent role for ATG5 in lung macrophages and dendritic cells (DCs) for suppressing TH17 responses and neutrophil accumulation in house dust mite (HDM)-challenged mice, a TH17/TH1 dominated model for allergic airway inflammation due to contamination of the HDM with lipopolysaccharide. In contrast, autophagy was required to promote eosinophil accumulation in the TH2-dominated ovalbumin model of allergic airway inflammation, supporting a model where autophagy functions in lung macrophages and DCs to suppress TH17 responses and promote TH2 responses in an allergen-dependent manner. In addition, we discover that autophagy is also required in macrophages exposed to HDM to suppress the secretion of cytokines and chemokines that would otherwise recruit neutrophils to the lungs, independent of T cell responses. Together, our data identify multiple roles for autophagy in suppressing the neutrophil accumulation in lungs that is associated with severe asthma.

immunology↗

bioRxiv2023

ATG5 suppresses type I IFN-dependent neutrophil swarming and NETosis

Inflammation is critical for controlling infections, but when left unchecked can cause tissue damage and disease. For tuberculosis, the leading cause of death due to infection1, host inflammation is responsible for the clinical symptoms2, morbidity2, and mortality3,4. Specifically, neutrophil-dominated inflammation is associated with tuberculosis disease progression3,5,6. Therefore, understanding how neutrophil functions are regulated during infection is important for developing ways to prevent disease. Atg5 was the first gene shown to specifically function within neutrophils to promote control of Mycobacterium tuberculosis7, the causative agent of tuberculosis. ATG5 is best studied for its role in autophagy8-11, however, the protective activity of ATG5 in neutrophils was unexpectedly independent of other autophagy proteins and remained elusive7. We report here that ATG5, but not other autophagy proteins, is required in neutrophils to suppress neutrophil NETosis and swarming that occur due to elevated type I interferon levels during M. tuberculosis infection. The elevated level of NETosis that results from loss of ATG5 expression contributes to the early susceptibility of Atg5fl/fl-LysM-Cre mice during M. tuberculosis infection. NETosis is associated with poor disease outcomes in tuberculosis12,13 and COVID-19 patients14,15, as well as during other inflammatory diseases in humans16,17. Our studies identify an essential regulator of NETosis and elucidate previously unappreciated roles for ATG5 during infection, which may inform the design of host-directed therapeutics modulating these pathways.

immunology↗

bioRxiv2022

Type I IFN signaling mediates NET release to promote Mycobacterium tuberculosis replication and granuloma caseation

Neutrophils are the most abundant cell type in airways of tuberculosis patients. Recent investigations reported induction of neutrophil extracellular traps (NETs) during Mycobacterium tuberculosis (Mtb) infection, however, the molecular regulation and impact of NETosis on Mtb pathogenesis is unknown. We find that in response to Mtb infection in neutrophils, PAD4 citrullinates histones to decondense chromatin that gets packaged into vesicles for release as NETs in a manner that can maintain neutrophil viability and promote Mtb replication. Type I interferon, which has been associated with NETosis in numerous contexts but without a known mechanism, promotes formation of chromatin-containing vesicles and NET release. Analysis of nonhuman primate granulomas supports a model where neutrophils are exposed to type I interferon from macrophages as they migrate into the granuloma, where they release NETs that contribute to necrosis and caseation. Our data reveals NETosis as a promising target to inhibit Mtb replication and granuloma caseation.

microbiology↗

bioRxiv2022

Autophagy protects against high-dose Mycobacterium tuberculosis infection

Host autophagy had been associated with the control of Mycobacterium tuberculosis (Mtb) infection due to its ability to sequesters microorganisms through a process termed "xenophagy"1-4. Xenophagy purportedly limits Mtb replication within infected macrophages1-4. However, studies in mice using a standard low-dose infection model demonstrated that xenophagy in infected phagocytes is not required to control Mtb pathogenesis5,6. Instead, an autophagy-independent function of ATG5 in myeloid cells controls low-dose Mtb infection through limiting neutrophilic inflammation5. Hitherto, an in vivo role for autophagy during Mtb infection remained to be elucidated. We report herein that autophagy in myeloid cells mediates protection against high-dose Mtb infection, providing the first evidence for a role for autophagy in myeloid cells during Mtb infection in vivo. With the exception of ATG5, the autophagy proteins required to control high-dose Mtb infection are dispensable for host defense against a standard low-dose Mtb infection. Specifically, autophagy is required in CD11c+ cells, but is dispensable in neutrophils, to control a high-dose Mtb infection in the lung. The role for autophagy is not to directly degrade Mtb in macrophages through xenophagy, but mainly to limit myeloid-derived suppressor cell accumulation and to promote sustained protective T cell responses. Together, our data highlight a novel role for autophagy in controlling Mtb infection, distinct from that of Atg5 during low-dose Mtb infection, or any previously reported roles for autophagy. In addition, our finding that the result of a pathogen-plus-susceptibility gene interaction is dependent on pathogen burden has important implications on our understanding of how Mtb infection in humans can lead to a spectrum of outcomes, the variables that contribute to autophagy gene function during infection and inflammation, and the potential use of autophagy modulators in clinical medicine.

microbiology↗

bioRxiv2022

Autophagy is required in macrophages and dendritic cells to prevent early recruitment of neutrophils during Mycobacterium tuberculosis infection

The immune response to Mycobacterium tuberculosis infection determines tuberculosis disease outcomes, yet we have an incomplete understanding of what immune factors contribute to a protective immune response. Neutrophilic inflammation has been associated with poor disease prognosis in humans and in animal models during M. tuberculosis infection and, therefore, must be tightly regulated. ATG5 is an essential autophagy protein that is required in innate immune cells to control neutrophil-dominated inflammation and promote survival during M. tuberculosis infection, however, the mechanistic basis for how ATG5 regulates neutrophil recruitment is unknown. To interrogate what innate immune cells require ATG5 to control neutrophil recruitment during M. tuberculosis infection, we used different mouse strains that conditionally delete Atg5 in specific cell types. We found that ATG5 is required in CD11c+ cells (lung macrophages and dendritic cells) to control the production of proinflammatory cytokines and chemokines during M. tuberculosis infection, which would otherwise promote neutrophil recruitment. This role for ATG5 is autophagy-dependent, but independent of mitophagy, LC3-associated phagocytosis, and inflammasome activation, which are the most well-characterized ways that autophagy proteins regulate inflammation. In addition to the increase in proinflammatory cytokine production during M. tuberculosis infection, loss of ATG5 in innate immune cells also results in an early induction of TH17 responses. Despite prior published in vitro cell culture experiments supporting a role for autophagy in controlling M. tuberculosis replication in macrophages, loss of autophagy does not affect M. tuberculosis burden in macrophages in vivo and, therefore, the effects of autophagy on inflammatory responses occur without changes in pathogen numbers. These findings reveal new roles for autophagy proteins in lung resident macrophages and dendritic cells that are required to suppress inflammatory responses that are associated with poor control of M. tuberculosis infection.

immunology↗