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IRGM and its mouse orthologue Irgm1 are dynamin-like proteins that regulate vesicular remodeling, intracellular microbial killing, and pathogen immunity. IRGM dysfunction is linked to inflammatory bowel disease (IBD), and while it is thought that defective intracellular killing of microbes underscores IBD susceptibility, studies have yet to address how IRGM/Irgm1 regulates immunity to microbes relevant to intestinal inflammation. Here we find that loss of Irgm1 confers marked susceptibility to Citrobacter rodentium, a noninvasive intestinal pathogen that models inflammatory responses to intestinal bacteria. Irgm1-deficient mice fail to control C. rodentium outgrowth in the intestine, leading to systemic pathogen spread and host mortality. Surprisingly, susceptibility due to loss of Irgm1 function was not linked to defective intracellular killing of C. rodentium or exaggerated inflammation, but was instead linked to failure to remodel specific colon lamina propria (C-LP) myeloid cells that expand in response to C. rodentium infection and are essential for C. rodentium immunity. Defective immune remodeling was most striking in C-LP monocytes, which were successfully recruited to the infected C-LP, but subsequently underwent apoptosis. Apoptotic susceptibility was induced by C. rodentium infection and was specific to this setting of pathogen infection, and was not apparent in other settings of intestinal inflammation. These studies reveal a novel role for Irgm1 in host defense and suggest that deficiencies in survival and remodeling of C-LP myeloid cells that control inflammatory intestinal bacteria may underpin IBD pathogenesis linked to IRGM dysfunction.

We previously developed integrase-defective lentiviral vectors (IDLVs) as an antigen delivery system for inducing strong and prolonged immunity in animal models. Here, we examined the association between persistence of antigen expression and durability of immune response. Following a single intramuscular (i.m.) or subcutaneous (s.c.) injection of IDLV delivering GFP in mice, we evaluated antigen expression and inflammation at the site of injection and persistence of antigen-specific T cells at early and late time points. Durable antigen expression was detected up to 90 days only after i.m. immunization. Mononuclear inflammation was evident soon after IDLV injection in both i.m. and s.c. immunized mice, but remained detectable up to 30 days postinjection only in i.m. immunized mice. Similarly, GFP-specific T cells were more persistent in the i.m. immunized mice. Interestingly, GFP+ muscle fibers were co-expressing major histocompatibility complex (MHC) class I, suggesting that muscle cells are competent for presenting antigens to T cells in vivo. In in vitro experiments, we demonstrated that although both primary myoblasts and myocytes present the antigen to GFP-specific T cells through MHC class I, myoblasts are more resistant to Fas-dependent cytotoxic T lymphocyte (CTL) killing activity. Overall, these data indicate that muscle cells may serve as an antigen reservoir that contributes to the long-term immunity induced by IDLV vaccination.

Glomerular diseases (GDs) are a major cause of chronic kidney disease in children. The conventional approach to diagnosis of GDs includes clinical evaluation and, in most cases, kidney biopsy to make a definitive diagnosis. However, in many cases, clinical presentations of different GDs can overlap, leading to uncertainty in diagnosis and management even after renal biopsy. In this report, we identify a family with clinical diagnoses of postinfectious glomerulonephritis and IgA nephropathy in a parent and two children. Renal biopsies were initially inconclusive; however, genetic testing showed that the two individuals diagnosed at different points with IgA nephropathy carried novel segregating pathogenic variants in COL4A5 gene. We were only able to make the final diagnoses in each of the family members after genetic testing and reverse phenotyping. This case highlights the utility of genetic testing and reverse phenotyping in resolving clinical diagnosis in families with unusual constellations of different glomerulopathies. We propose that clustering of different glomerular disease phenotypes in a family should be an indication for genetic testing followed by reverse phenotyping.

Abstract Glomerular podocytes play a key role in proteinuric diseases. Accumulating evidence suggests that cGMP signaling has podocyte protective effects. The major source of cGMP generation in podocytes is natriuretic peptides. The natriuretic peptide clearance receptor (NPRC) binds and degrades natriuretic peptides. As a result, NPRC inhibits natriuretic peptide‐induced cGMP generation. To enhance cGMP generation in podocytes, we blocked natriuretic peptide clearance using the specific NPRC ligand ANP(4‐23). We then studied the effects of NPRC blockade in both cultured podocytes and in a mouse transgenic (TG) model of focal segmental glomerulosclerosis (FSGS) created in our laboratory. In this model, a single dose of the podocyte toxin puromycin aminonucleoside (PAN) causes robust albuminuria in TG mice, but only mild disease in non‐TG animals. We found that natriuretic peptides protected cultured podocytes from PAN‐induced apoptosis, and that ANP(4‐23) enhanced natriuretic peptide‐induced cGMP generation in vivo. PAN‐induced heavy proteinuria in vehicle‐treated TG mice, and this increase in albuminuria was reduced by treatment with ANP(4‐23). Treatment with ANP(4‐23) also reduced the number of mice with glomerular injury and enhanced urinary cGMP excretion, but these differences were not statistically significant. Systolic BP was similar in vehicle and ANP(4‐23)‐treated mice. These data suggest that: 1. Pharmacologic blockade of NPRC may be useful for treating glomerular diseases such as FSGS, and 2. Treatment outcomes might be improved by optimizing NPRC blockade to inhibit natriuretic peptide clearance more effectively.

ABSTRACT: Objective: To present a rare case of multiple pituitary adenomas with a functional follicle-stimulating hormone component leading to ovarian hyperstimulation syndrome.Methods: We present the clinical, laboratory, imaging, and pathologic findings along with a review of the literature.Results: A 28-year-old female presented with 5 months of amenorrhea and abdominal pain. Physical exam was unremarkable. Labs revealed elevated prolactin (94 ng/mL), elevated estradiol (608 pg/mL), inappropriately normal follicle-stimulating hormone (10.2 mIU/mL), and suppressed luteinizing hormone (0.36 mIU/mL). Transvaginal ultrasound showed numerous large ovarian cysts bilaterally. Brain magnetic resonance imaging showed a 1.2-cm sellar mass. Various medical therapies were not tolerated due to side effects and the patient underwent gross total resection of the sellar mass with marked improvement in her symptoms and blood hormone levels, resumption of menstruation, and shrinkage of the ovarian cysts. Histologic examination revealed 3 separate staining patterns consistent with multiple pituitary adenomas.Conclusion: Functioning gonadotroph adenomas are rare and often difficult to diagnose, though in premenopausal women they can lead to the distinct clinical presentation of spontaneous ovarian hyperstimulation syndrome. The favored treatment approach is surgical as it has the highest reported success rate. Recurrence is not uncommon and long-term surveillance is recommended. Given limited data on long-term follow-up, the role of available therapies is not well defined, and further research is needed. To our knowledge, this is the first reported case of multiple pituitary adenomas that included a functional gonadotroph component.Abbreviations: FSH = follicle-stimulating hormone; LH = luteinizing hormone; OHSS = ovarian hyperstimulation syndrome; PiT1 = inorganic phosphate transporter 1; SF1 = steroidogenic factor 1