IL12RB1 is essential for human resistance to multiple intracellular pathogens, including Mycobacterium tuberculosis. In its absence, the proinflammatory effects of the extracellular cytokines IL-12 and IL-23 fail to occur, and intracellular bacterial growth goes unchecked. Given the recent observation that mouse leukocytes express more than one isoform from il12rb1, we examined whether primary human leukocytes similarly express more than one isoform from IL12RB1. We observed that human leukocytes express as many as 13 distinct isoforms, the relative levels of each being driven by inflammatory stimuli both in vitro and in vivo. Surprisingly, the most abundant isoform present before stimulation is a heretofore uncharacterized intracellular form of the IL-12R (termed “isoform 2”) that presumably has limited contact with extracellular cytokine. After stimulation, primary PBMCs, including the CD4+, CD8+, and CD56+ lineages contained therein, alter the splicing of IL12RB1 RNA to increase the relative abundance of isoform 1, which confers IL-12/IL-23 responsiveness. These data demonstrate both a posttranscriptional mechanism by which cells regulate their IL-12/IL-23 responsiveness, and that leukocytes primarily express IL12RB1 in an intracellular form located away from extracellular cytokine.

Tuberculosis (TB) is a significant human disease caused by inhalation of Mycobacterium tuberculosis (Mtb). Left untreated, TB mortality is associated with a failure to resolve pulmonary immunopathology. There is currently widespread interest in using Vitamin D3 (VitD3) as an adjunct therapy for TB, as numerous in vitro studies have shown that VitD3 has direct and indirect mycobactericidal activities. However, to date there have been no in vivo studies addressing whether VitD3 affects experimental TB outcome. Here we use C3HeB/FeJ mice to determine if dietary VitD3 influences the outcome of experimental TB. We observed that although Mtb burdens did not differ between mice on a VitD3-replete diet (VitDHI mice) and mice on a VitD3-deficient diet (VitDLO mice), the inflammatory response in VitDHI mice was significantly attenuated relative to VitDLO controls. Specifically, the expression of multiple inflammatory pathways was reduced in the lungs at later disease stages, as were splenocyte IL12/23p40- and IFNγ-levels following ex vivo restimulation. Dietary VitD3 also suppressed the accumulation of T cells in the mediastinal lymph nodes and lung granulomatous regions, while concomitantly accelerating the accumulation of F4/80+ and Ly6C/Ly6G+ lineages. The altered inflammatory profile of VitDHI mice also associated with reductions in pulmonary immunopathology. VitD receptor deficient (vdr−/−) radiation bone marrow chimeras demonstrate that reductions in pulmonary TB-immunopathology are dependent on hematopoietic VitD-responsiveness. Collectively, our data support a model wherein the in vivo role of VitD3 during TB is not to promote Mtb killing, but rather to function through hematopoietic cells to reduce Mtb-elicited immunopathology.

Summary IL12B is required for resistance to Mycobacterium tuberculosis (Mtb) infection, promoting the initiation and maintenance of Mtb-specific effector responses. While this makes the IL12-pathway an attractive target for experimental tuberculosis (TB) therapies, data regarding what lineages express IL12B after infection is established are limited. This is not obvious in the lung, an organ in which both hematopoietic and non-hematopoietic lineages produce IL12p40 upon pathogen encounter. Here, we use radiation bone marrow chimeras and Yet40 reporter mice to determine what lineages produce IL12p40 during experimental TB. We observed that hematopoietic IL12p40-production was sufficient to control Mtb, with no contribution by non-hematopoietic lineages. Furthermore, rather than being produced by a single subset, IL12p40 was produced by cells that were heterogenous in their size, granularity, autofluorescence and expression of CD11c, CD11b and CD8α. While depending on the timepoint and tissue examined, the surface phenotype of IL12p40-producers most closely resembled macrophages based on previous surveys of lung myeloid lineages. Importantly, depletion of CDllchi cells during infection had no affect on lung IL12p40-concentrations. Collectively, our data demonstrate that IL12p40 production is sustained by a heterogenous population of myeloid lineages during experimental TB, and that redundant mechanisms of IL12p40-production exist when CD11chi lineages are absent.

Objective:Describe the epidemiological and molecular characteristics of an outbreak of Klebsiella pneumoniae carbapenemase (KPC)–producing organisms and the novel use of a cohorting unit for its control.Design:Observational study.Setting:A 566-room academic teaching facility in Milwaukee, Wisconsin.Patients:Solid-organ transplant recipients.Methods:Infection control bundles were used throughout the time of observation. All KPC cases were intermittently housed in a cohorting unit with dedicated nurses and nursing aids. The rooms used in the cohorting unit had anterooms where clean supplies and linens were placed. Spread of KPC-producing organisms was determined using rectal surveillance cultures on admission and weekly thereafter among all consecutive patients admitted to the involved units. KPC-positive strains underwent pulsed-field gel electrophoresis and whole-genome sequencing.Results:A total of 8 KPC cases (5 identified by surveillance) were identified from April 2016 to April 2017. After the index patient, 3 patients acquired KPC-producing organisms despite implementation of an infection control bundle. This prompted the use of a cohorting unit, which immediately halted transmission, and the single remaining KPC case was transferred out of the cohorting unit. However, additional KPC cases were identified within 2 months. Once the cohorting unit was reopened, no additional KPC cases occurred. The KPC-positive species identified during this outbreak included Klebsiella pneumoniae, Enterobacter cloacae complex, and Escherichia coli. blaKPC was identified on at least 2 plasmid backbones.Conclusions:A complex KPC outbreak involving both clonal and plasmid-mediated dissemination was controlled using weekly surveillances and a cohorting unit.