Biology subjects

Meade, R. K.

Publications and source records attributed to Meade, R. K..

7 recordsLinked to original sources

bioRxiv2025

CCR6 is essential for effective immunity against Mycobacterium tuberculosis infection in mice

Tuberculosis (TB) is a global epidemic that has threatened human health throughout recorded history. TB disease, caused by infection with Mycobacterium tuberculosis (M.tb), is heterogeneous between individuals, and clinical TB outcomes are impacted by genetic and environmental risk factors. Infected individuals must maintain a careful balance of cytokines and chemokines following M.tb infection to eliminate or contain the bacteria without causing excessive inflammation and lung damage. The CC chemokine receptor 6 (CCR6) is expressed by several immune cell populations that are classically involved in the pathogenesis of M.tb infection. However, the precise functions of CCR6 in the context of TB disease remain underexplored. Here, we show that mice lacking the CCR6 receptor (CCR6 KO) fail to restrict bacterial burden in the lungs, leading to increased disseminated infection at 4-weeks post-infection compared to wild-type C57BL/6J (B6) mice, with a more pronounced effect in females. CCR6 KO mice also developed necrotic pulmonary lesions, phenotypically distinct from B6 mice, and produced elevated levels of pro-inflammatory cytokines and chemokines at the onset of adaptive immunity, particularly IL-17. Long-term infection experiments revealed that the absence of CCR6 enhances risk for mortality following M.tb infection, particularly in females. This study provides insights into the role of CCR6 during TB pathogenesis and establishes its importance in maintaining protective immunity against M.tb within the context of a genetically tractable mouse model that forms necrotic pulmonary granulomas.

microbiology↗

bioRxiv2025

The mouse pangenome reveals the structural complexity of the murine protein coding landscape

We present the first mouse pangenome consisting of 17 high-quality inbred mouse strain genomes with complete annotation. This collection includes 12 widely used classical laboratory strains and 5 wild-derived strains. We have fully resolved previously incomplete genomic regions, including the major histocompatibility complex (MHC), the defensin cluster, T-cell receptor, and Ly49 complexes. Hundreds of non-reference genes identified in previous publications not found in GRCm39, like Defa1, Raet1a, and Klra20 (Ly49T), were localised in the new reference genomes. We conducted the first genome-wide scan of variable number tandem repeats (VNTRs) within the coding regions of mice, identifying over 400 genes with VNTR polymorphisms up to more than 600 repeat copies and repeat units reaching 990 nucleotides. Our strain-specific annotations enhance RNA-Seq analyses, as demonstrated in PWK/PhJ, where we observed a 5.1% improvement in read mapping and expression level differences in 2.1% of coding genes compared to using GRCm39.

genomics↗

bioRxiv2025

Cathepsin Z is a conserved susceptibility factor underlying tuberculosis severity

Tuberculosis (TB) outcomes vary widely, from asymptomatic infection to mortality, yet most animal models do not recapitulate human phenotypic and genotypic variation. The genetically diverse Collaborative Cross mouse panel models distinct facets of TB disease that occur in humans and allows identification of genomic loci underlying clinical outcomes. We previously mapped a TB susceptibility locus on mouse chromosome 2. Here, we identify cathepsin Z (Ctsz) as a lead candidate underlying this TB susceptibility and show that Ctsz ablation leads to increased bacterial burden, CXCL1 overproduction, and decreased survival in mice. Ctsz disturbance within murine macrophages enhances production of CXCL1, a known biomarker of TB severity. From a Ugandan household contact study, we identify significant associations between CTSZ variants and TB disease severity. Finally, we examine patient-derived TB granulomas and report CTSZ localization within granuloma-associated macrophages, placing human CTSZ at the host-pathogen interface. These findings implicate a conserved CTSZ-CXCL1 axis in humans and genetically diverse mice that mediates TB disease severity.

genetics↗

bioRxiv2023

Genome-wide screen identifies host loci that modulate M. tuberculosis fitness in immunodivergent mice

Genetic differences among mammalian hosts and Mycobacterium tuberculosis (Mtb) strains determine diverse tuberculosis (TB) patient outcomes. The advent of recombinant inbred mouse panels and next-generation transposon mutagenesis and sequencing approaches has enabled dissection of complex host- pathogen interactions. To identify host and pathogen genetic determinants of Mtb pathogenesis, we infected members of the BXD family of mouse strains with a comprehensive library of Mtb transposon mutants (TnSeq). Members of the BXD family segregate for Mtb-resistant C57BL/6J (B6 or B) and Mtb-susceptible DBA/2J (D2 or D) haplotypes. The survival of each bacterial mutant was quantified within each BXD host, and we identified those bacterial genes that were differentially required for Mtb fitness across BXD genotypes. Mutants that varied in survival among the host family of strains were leveraged as reporters for "endophenotypes", each bacterial fitness profile directly probing specific components of the infection microenvironment. We conducted QTL mapping of these bacterial fitness endophenotypes and identified 140 host-pathogen quantitative trait loci (hpQTL). We identified a QTL hotspot on chromosome 6 (75.97-88.58 Mb) associated with the genetic requirement of multiple Mtb genes; Rv0127 (mak), Rv0359 (rip2), Rv0955 (perM), and Rv3849 (espR). Together, this screen reinforces the utility of bacterial mutant libraries as precise reporters of the host immunological microenvironment during infection and highlights specific host-pathogen genetic interactions for further investigation. To enable downstream follow-up for both bacterial and mammalian genetic research communities, all bacterial fitness profiles have been deposited into GeneNetwork.org and added into the comprehensive collection of TnSeq libraries in MtbTnDB.

genetics↗

bioRxiv2022

Differential requirement for IRGM proteins during tuberculosis infection in mice

Mycobacterium tuberculosis (Mtb) is a bacterium that exclusively resides in human hosts and remains a dominant cause of morbidity and mortality among infectious diseases worldwide. Host protection against Mtb infection is dependent on the function of immunity-related GTPase clade M (IRGM) proteins. Polymorphisms in human IRGM associate with altered susceptibility to mycobacterial disease, and human IRGM promotes the delivery of Mtb into degradative autolysosomes. Among the three murine IRGM orthologs, Irgm1 has been singled out as essential for host protection during Mtb infections in cultured macrophages and in vivo. However, whether the paralogous murine Irgm genes, Irgm2 and Irgm3, play roles in host defense against Mtb or exhibit functional relationships with Irgm1 during Mtb infection remains undetermined. Here, we report that Irgm1-/- mice are indeed acutely susceptible to aerosol infection with Mtb, yet the additional deletion of the paralogous Irgm3 gene restores protective immunity to Mtb infections in Irgm1-deficient animals. Mice lacking all three Irgm genes (panIrgm-/-) are characterized by shifted lung cytokine profiles at 4 and 24 weeks post infection, but control disease until the very late stages of the infection, when panIrgm-/- mice display increased mortality compared to wild type mice. Collectively, our data demonstrate that disruptions in the balance between Irgm isoforms is more detrimental to the Mtb-infected host than total loss of Irgm-mediated host defense, a concept that also needs to be considered in the context of human Mtb susceptibility linked to IRGM polymorphisms.

microbiology↗

bioRxiv2020

Host-pathogen genetic interactions underlie tuberculosis susceptibility in genetically diverse mice

The outcome of an encounter with Mycobacterium tuberculosis depends on the pathogens ability to adapt to the variable immune pressures exerted by the host. Understanding this interplay has proven difficult, largely because experimentally tractable animal models do not recapitulate the heterogeneity of tuberculosis disease. We leveraged the genetically diverse Collaborative Cross (CC) mouse panel in conjunction with a library of Mtb mutants to associate bacterial genetic requirements with host genetics and immunity. We report that CC strains vary dramatically in their susceptibility to infection and produce qualitatively distinct immune states. Global analysis of Mtb mutant fitness across the CC panel revealed that many virulence pathways are only in specific host microenvironments, identifying the large fraction of the pathogens genome that has been maintained to ensure fitness in a diverse population. Both immunological and bacterial traits were associated with genetic variants distributed across the mouse genome, identifying the specific host-pathogen genetic interactions that influence pathogenesis.

genetics↗

bioRxiv2019

A loss-of-function mutation in Itgal contributes to the high susceptibility of Collaborative Cross strain CC042 to Salmonella infections

Salmonella are intracellular bacteria that are found in the gastrointestinal tract of mammalian, avian, and reptilian hosts. They are one of the leading causes of foodborne infections and a major threat for human populations worldwide. Mouse models have been extensively used to model distinct aspects of the human Salmonella infections in vivo and have led to the identification of several host susceptibility genes. We have investigated the susceptibility of Collaborative Cross strains to intravenous infection with Salmonella Typhimurium as a model of human systemic invasive infection. In this model, strain CC042 displayed extreme susceptibility with very high bacterial loads and mortality. CC042 mice showed lower spleen weight and decreased splenocyte numbers before and after infection, affecting mostly CD8+ T cells, B cells, and all myeloid populations. Uninfected mice also had lower thymus weight with reduced total number of thymocytes and double negative and (CD4+, CD8+) double positive thymocytes. Analysis of bone marrow resident hematopoietic progenitors showed a strong bias against lymphoid primed multipotent progenitors, which are the precursors of T, B and NK cells. An F2 cross between CC042 and C57BL/6N identified two significant QTLs on chromosome 7 (Stsl6 and Stsl7) with WSB-derived susceptible alleles. A private variant in the integrin alpha L (Itgal) gene is carried by CC042 in the Stsl7 QTL region. A quantitative complementation test confirmed the impact of Itgal loss of function in a (C57BL/6JxCC042)F1 background, but not in a C57BL/6J inbred background. These results further emphasize the utility of the Collaborative Cross to identify new host genetic variants controlling susceptibility to infections and improve our understanding of the function of the Itgal gene.\n\nAuthor summarySalmonella are one of the leading causes of foodborne infections and a major threat for human populations worldwide. Not all humans are equally susceptible to Salmonella infection. Some individuals will develop minor symptoms and recover while others develop severe illness and might die. Mouse models are used to study distinct aspects of human Salmonella infection in vivo. We used a new genetically diverse mouse population to investigate host susceptibility differences to Salmonella infection. We identified one mouse strain with an extreme susceptibility to infection characterized by very high bacterial loads and mortality. Mice of this strain had small thymus and spleen, two organs which are very important for producing a fully mature immune system. We showed that the strains immune response is impaired and that its extreme susceptibility to Salmonella infection is due to multiple genes defects. We identified a loss-of-function mutation in the Itgal gene (Integrin Subunit Alpha L) that plays a central role in the immune response to infection. This gene explains part of the susceptibility and other gene(s) involved remain to be identified. Our results emphasize how new genetically diverse animal models can lead to the identification of new host genetic variants controlling susceptibility to pathogens and improve our understanding of human infections.

immunology↗