APOE Protects Against Severe Infection with by Restraining Production of Neutrophil Extracellular Traps.

While neutrophils are the predominant cell type in the lungs of humans with active tuberculosis (TB), they are relatively scarce in the lungs of most strains of mice that are used to study the disease. However, similar to humans, neutrophils account for approximately 45% of CD45+ cells in the lungs of mice on a high-cholesterol (HC) diet following infection with (Mtb). We hypothesized that the susceptibility of HC mice might arise from an unrestrained feed-forward loop in which production of neutrophil extracellular traps (NETs) stimulates production of type I interferons by pDCs which in turn leads to the recruitment and activation of more neutrophils, and demonstrated that depleting neutrophils, depleting plasmacytoid dendritic cells (pDCs), or blocking type I interferon signaling, improved the outcome of infection.

Host and pathogen genetic diversity shape vaccine-mediated protection to .

To investigate how host and pathogen diversity govern immunity against (Mtb), we performed a large-scale screen of vaccine-mediated protection against aerosol Mtb infection using three inbred mouse strains [C57BL/6 (B6), C3HeB/FeJ (C3H), Balb/c x 129/SvJ (C129F1)] and three Mtb strains (H37Rv, CDC1551, SA161) representing two lineages and distinct virulence properties. We compared three protective modalities, all of which involve inoculation with live mycobacteria: Bacillus Calmette-Guérin (BCG), the only approved TB vaccine, delivered either subcutaneously or intravenously, and concomitant Mtb infection (CoMtb), a model of pre-existing immunity in which a low-level Mtb infection is established in the cervical lymph node following intradermal inoculation. We examined lung bacterial burdens at early (Day 28) and late (Day 98) time points after aerosol Mtb challenge and histopathology at Day 98.

Reappraising the Role of T Cell-Derived IFN-γ in Restriction of Mycobacterium tuberculosis in the Murine Lung.

T cells producing IFN-γ have long been considered a stalwart for immune protection against Mycobacterium tuberculosis (Mtb), but their relative importance to pulmonary immunity has been challenged by murine studies that achieved protection by adoptively transferred Mtb-specific IFN-γ-/- T cells. Using IFN-γ-/- T cell chimeric mice and adoptive transfer of IFN-γ-/- T cells into TCRβ-/-δ-/- mice, we demonstrate that control of lung Mtb burden is in fact dependent on T cell-derived IFN-γ, and, furthermore, mice selectively deficient in T cell-derived IFN-γ develop exacerbated disease compared with T cell-deficient control animals, despite equivalent lung bacterial burdens. Deficiency in T cell-derived IFN-γ skews infected and bystander monocyte-derived macrophages to an alternative M2 phenotype and promotes neutrophil and eosinophil influx.

CD4-mediated immunity shapes neutrophil-driven tuberculous pathology.

Pulmonary (Mtb) infection results in highly heterogeneous lesions ranging from granulomas with central necrosis to those primarily comprised of alveolitis. While alveolitis has been associated with prior immunity in human post-mortem studies, the drivers of these distinct pathologic outcomes are poorly understood. Here, we show that these divergent lesion structures can be modeled in C3HeB/FeJ mice and are regulated by prior immunity.

Re-appraising the role of T-cell derived interferon gamma in restriction of in the murine lung: T-cell derived IFNγ is required to restrict pulmonary Mtb.

T cells producing interferon gamma (IFNγ) have long been considered a stalwart for immune protection against (), but their relative importance to pulmonary immunity has been challenged by murine studies which achieved protection by adoptively transferred -specific IFNγ T cells. Using IFNγ T cell chimeric mice and adoptive transfer of IFNγ T cells into TCRβδ mice, we demonstrate that control of lung burden is in fact dependent on T cell-derived IFNγ, and furthermore, mice selectively deficient in T cell-derived IFNγ develop exacerbated disease compared to T cell-deficient controls despite equivalent lung bacterial burdens. Deficiency in T cell-derived IFNγ skews infected and bystander monocyte-derived macrophages (MDMs) to an alternative M2 phenotype, and promotes neutrophil and eosinophil influx.

TOLLIP inhibits lipid accumulation and the integrated stress response in alveolar macrophages to control Mycobacterium tuberculosis infection.

A polymorphism causing deficiencies in Toll-interacting protein (TOLLIP), an inhibitory adaptor protein affecting endosomal trafficking, is associated with increased tuberculosis (TB) risk. It is, however, unclear how TOLLIP affects TB pathogenesis. Here we show that TB severity is increased in Tollip mice, characterized by macrophage- and T cell-driven inflammation, foam cell formation and lipid accumulation.

The Tuberculous Granuloma and Preexisting Immunity.

Pulmonary granulomas are widely considered the epicenters of the immune response to (Mtb), the causative agent of tuberculosis (TB). Recent animal studies have revealed factors that either promote or restrict TB immunity within granulomas. These models, however, typically ignore the impact of preexisting immunity on cellular organization and function, an important consideration because most TB probably occurs through reinfection of previously exposed individuals.

TGFβ restricts expansion, survival, and function of T cells within the tuberculous granuloma.

CD4 T cell effector function is required for optimal containment of Mycobacterium tuberculosis (Mtb) infection. IFNɣ produced by CD4 T cells is a key cytokine that contributes to protection. However, lung-infiltrating CD4 T cells have a limited ability to produce IFNɣ, and IFNɣ plays a lesser protective role within the lung than at sites of Mtb dissemination.

Ultra-low Dose Aerosol Infection of Mice with Mycobacterium tuberculosis More Closely Models Human Tuberculosis.

Tuberculosis (TB) is a heterogeneous disease manifesting in a subset of individuals infected with aerosolized Mycobacterium tuberculosis (Mtb). Unlike human TB, murine infection results in uniformly high lung bacterial burdens and poorly organized granulomas. To develop a TB model that more closely resembles human disease, we infected mice with an ultra-low dose (ULD) of between 1-3 founding bacteria, reflecting a physiologic inoculum.

CytoMAP: A Spatial Analysis Toolbox Reveals Features of Myeloid Cell Organization in Lymphoid Tissues.

Recently developed approaches for highly multiplexed imaging have revealed complex patterns of cellular positioning and cell-cell interactions with important roles in both cellular- and tissue-level physiology. However, tools to quantitatively study cellular patterning and tissue architecture are currently lacking. Here, we develop a spatial analysis toolbox, the histo-cytometric multidimensional analysis pipeline (CytoMAP), which incorporates data clustering, positional correlation, dimensionality reduction, and 2D/3D region reconstruction to identify localized cellular networks and reveal features of tissue organization.

Cutting Edge: Bacillus Calmette-Guérin-Induced T Cells Shape Infection before Reducing the Bacterial Burden.

Growing evidence suggests the outcome of infection is established rapidly after exposure, but how the current tuberculosis vaccine, bacillus Calmette-Guérin (BCG), impacts early immunity is poorly understood. In this study, we found that murine BCG immunization promotes a dramatic shift in infected cell types. Although alveolar macrophages are the major infected cell for the first 2 weeks in unimmunized animals, BCG promotes the accelerated recruitment and infection of lung-infiltrating phagocytes.

Alveolar Macrophages Provide an Early Mycobacterium tuberculosis Niche and Initiate Dissemination.

Mycobacterium tuberculosis (Mtb) infection is initiated in the distal airways, but the bacteria ultimately disseminate to the lung interstitium. Although various cell types, including alveolar macrophages (AM), neutrophils, and permissive monocytes, are known to be infected with Mtb, the initially infected cells as well as those that mediate dissemination from the alveoli to the lung interstitium are unknown. In this study, using a murine infection model, we reveal that early, productive Mtb infection occurs almost exclusively within airway-resident AM.

Continued in vitro cefazolin susceptibility in methicillin-susceptible Staphylococcus aureus.

Objectives: In vitro trends of cefazolin and ceftriaxone susceptibilities from pediatric clinical isolates of methicillin-susceptible Staphylococcus aureus (MSSA) between 2011 and 2016 were analyzed for surveillance.

Methods: Our laboratory continues to use agar disk diffusion for staphylococcal susceptibilities applying Clinical Laboratory Standard Institute's 2012 breakpoints.

Results: A total of 3992 MSSA clinical isolates in the last 6 years were analyzed for their in vitro cefazolin and ceftriaxone susceptibilities.

Limited model antigen expression by transgenic fungi induces disparate fates during differentiation of adoptively transferred T cell receptor transgenic CD4+ T cells: robust activation and proliferation with weak effector function during recall.

CD4(+) T cells are the key players of vaccine resistance to fungi. The generation of effective T cell-based vaccines requires an understanding of how to induce and maintain CD4(+) T cells and memory. The kinetics of fungal antigen (Ag)-specific CD4(+) T cell memory development has not been studied due to the lack of any known protective epitopes and clonally restricted T cell subsets with complementary T cell receptors (TCRs).

Vaccine-induced protection against 3 systemic mycoses endemic to North America requires Th17 cells in mice.

Worldwide rates of systemic fungal infections, including three of the major pathogens responsible for such infections in North America (Coccidioides posadasii, Histoplasma capsulatum, and Blastomyces dermatitidis), have soared recently, spurring interest in developing vaccines. The development of Th1 cells is believed to be crucial for protective immunity against pathogenic fungi, whereas the role of Th17 cells is vigorously debated. In models of primary fungal infection, some studies have shown that Th17 cells mediate resistance, while others have shown that they promote disease pathology.