Yaíma L Lightfoot’s research while affiliated with University of Florida and other places

Most natural history models for type 1 diabetes (T1D) propose that overt hyperglycemia results following a progressive loss of insulin secreting β cell mass and/or function. To experimentally address this concept, we prospectively determined morning blood glucose measurements every other day in multiple cohorts (total n=660) of female NOD/ShiLtJ mice starting at 8 wk of age until diabetes onset or 26 weeks of age. Consistent with this notion, a majority of mice that developed diabetes (354/489; 72%) displayed a progressive increase in blood glucose with transient excursions above 200mg/dL, followed by acute and persistent hyperglycemia at diabetes onset. However, 135/489 (28%) of the diabetic animals demonstrated normal glucose values followed by acute (i.e., sudden) hyperglycemia. Interestingly, diabetes onset occurred earlier in mice with acute versus progressive disease onset (15.37±0.3207 vs. 17.44±0.2073 wk of age, P < 0.0001). Moreover, the pattern of onset (i.e., progressive vs. acute) dramatically influenced the ability to achieve reversal of T1D by immunotherapeutic intervention, with increased effectiveness observed in situations of a progressive deterioration in euglycemia. These studies highlight a novel natural history aspect in this animal model, one that may provide important guidance for the selection of subjects participating in human trials seeking disease reversal. © 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

Intestinal immune regulatory signals govern gut homeostasis. Breakdown of such regulatory mechanisms may result in inflammatory bowel disease (IBD). Lactobacillus acidophilus contains unique surface layer proteins (Slps), including SlpA, SlpB, SlpX, and lipoteichoic acid (LTA), which interact with pattern recognition receptors to mobilize immune responses. Here, to elucidate the role of SlpA in protective immune regulation, the NCK2187 strain, which solely expresses SlpA, was generated. NCK2187 and its purified SlpA bind to the C-type lectin SIGNR3 to exert regulatory signals that result in mitigation of colitis, maintenance of healthy gastrointestinal microbiota, and protected gut mucosal barrier function. However, such protection was not observed in Signr3(-/-) mice, suggesting that the SlpA/SIGNR3 interaction plays a key regulatory role in colitis. Our work presents critical insights into SlpA/SIGNR3-induced responses that are integral to the potential development of novel biological therapies for autoinflammatory diseases, including IBD. © 2015 The Authors.

Gastrointestinal (GI) anthrax results from the ingestion of Bacillus anthracis. Herein, we investigated the pathogenesis of GI anthrax in animals orally infected with toxigenic non-encapsulated B. anthracis Sterne strain (pXO1+ pXO2-) spores that resulted in rapid animal death. B. anthracis Sterne induced significant breakdown of intestinal barrier function and led to gut dysbiosis, resulting in systemic dissemination of not only B. anthracis, but also of commensals. Disease progression significantly correlated with the deterioration of innate and T cell functions. Our studies provide critical immunologic and physiologic insights into the pathogenesis of GI anthrax infection, whereupon cleavage of mitogen-activated protein kinases (MAPKs) in immune cells may play a central role in promoting dysfunctional immune responses against this deadly pathogen.

The intestinal epithelium is equipped with sensing receptor mechanisms that interact with luminal microorganisms and nutrients to regulate barrier function and gut immune responses, thereby maintaining intestinal homeostasis. Herein, we clarify the role of the extracellular calcium-sensing receptor (CaSR) using intestinal epithelium-specific Casr(-/-) mice. Epithelial CaSR deficiency diminished intestinal barrier function, altered microbiota composition, and skewed immune responses towards proinflammatory. Consequently, Casr(-/-) mice were significantly more prone to chemically induced intestinal inflammation resulting in colitis. Accordingly, CaSR represents a potential therapeutic target for autoinflammatory disorders, including inflammatory bowel diseases.

Ingestion of Bacillus anthracis spores causes gastrointestinal (GI) anthrax. Humoral immune responses, particularly immunoglobulin A (IgA)–secreting B-1 cells, play a critical role in the clearance of GI pathogens. Here, we investigated whether B. anthracis impacts the function of colonic B-1 cells to establish active infection. GI anthrax led to significant inhibition of immunoglobulins (eg, IgA) and increased expression of program death 1 on B-1 cells. Furthermore, infection also diminished type 2 innate lymphoid cells (ILC2) and their ability to enhance differentiation and immunoglobulin production by secreting interleukin 5 (IL-5). Such B-1–cell and ILC2 dysfunction is potentially due to cleavage of p38 and Erk1/2 mitogen-activated protein kinases in these cells. Conversely, mice that survived infection generated neutralizing antibodies via the formation of robust germinal center B cells in Peyer's patches and had restored B-1–cell and ILC2 function. These data may provide additional insight for designing efficacious vaccines and therapeutics against this deadly pathogen.

Production of long-lived, high affinity humoral immunity is an essential characteristic of successful vaccination and requires cognate interactions between T and B cells in germinal centers. Within germinal centers, specialized T follicular helper cells assist B cells and regulate the antibody response by mediating the differentiation of B cells into memory or plasma cells after exposure to T cell-dependent antigens. It is now appreciated that local immune responses are also essential for protection against infectious diseases that gain entry to the host by the mucosal route; therefore, targeting the mucosal compartments is the optimum strategy to induce protective immunity. However, because the gastrointestinal mucosae are exposed to large amounts of environmental and dietary antigens on a daily basis, immune regulatory mechanisms exist to favor tolerance and discourage autoimmunity at these sites. Thus, mucosal vaccination strategies must ensure that the immunogen is efficiently taken up by the antigen presenting cells, and that the vaccine is capable of activating humoral and cellular immunity, while avoiding the induction of tolerance. Despite significant progress in mucosal vaccination, this potent platform for immunotherapy and disease prevention must be further explored and refined. Here we discuss recent progress in the understanding of the role of different phenotypes of B cells in the development of an efficacious mucosal vaccine against infectious disease.

Mechanisms of colorectal cancer (CRC) development can be generally divided into three categories: genetic, epigenetic, and aberrant immunologic signaling pathways, all of which may be triggered by an imbalanced intestinal microbiota. Aberrant gut microbial composition, termed 'dysbiosis', has been reported in inflammatory bowel disease patients who are at increased risk for CRC development. Recent studies indicate that it is feasible to rescue experimental models of colonic cancer by oral treatment with genetically engineered beneficial bacteria and/or their immune-regulating gene products. Here, we review the mechanisms of epigenetic modulation implicated in the development and progression of CRC, which may be the result of dysbiosis, and therefore may be amenable to therapeutic intervention.

As highlighted by the development of intestinal autoinflammatory disorders when tolerance is lost, homeostatic interactions between gut microbiota, resident immune cells, and the gut epithelium are key in the maintenance of gastrointestinal health. Gut immune responses, whether stimulatory or regulatory, are dictated by the activated dendritic cells (DCs) that first interact with microorganisms and their gene products to then elicit T and B cell responses. Previously, we have demonstrated that treatment with genetically modified Lactobacillus acidophilus is sufficient to tilt the immune balance from proinflammatory to regulatory in experimental models of colitis and colon cancer. Given the significant role of DCs in efficiently orchestrating intestinal immune responses, characterization of the signals induced within these cells by the surface layer molecules, such as lipoteichoic acid (LTA), and proteins of L. acidophilus is critical for future treatment and prevention of gastrointestinal diseases. Here, we discuss the potential regulatory pathways involved in the downregulation of pathogenic inflammation in the gut, and explore questions regarding the immune responses to LTA-deficient L. acidophilus that require future studies.

L. gasseri expressing PA-DCpep induce regulatory T cells in MLN. (A & B) C57BL/6 mice were orally gavaged with increasing doses of L. gasseri expressing PA-DCpep (107, 109 and 1012 CFU) or PBS, and MLNs were harvested after days 1, 3, 7 and 14, stained with antibodies against CD4, CD8, FoxP3, TGFβ and IL-10, and analyzed by flow cytometry. Data are representative of two independent experiments. Error bars represent ±SEM. *P<0.05 and **P<0.01 compared with PBS. (TIF)

L. gasseri expressing PA-DCpep induces systemic immunity. (A & B) C57BL/6 mice were orally gavaged with increasing doses of L. gasseri expressing PA-DCpep (107, 109 and 1012 CFU) or PBS; MLNs were harvested after days 1, 3, 7 and 14, stained with antibodies against CD11c, CD11b, F4/80, IL-10, IL-12 and TNFα, and analyzed by flow cytometry. Data are representative of two independent experiments. Error bars represent ±SEM. *P<0.05 and **P<0.01 compared with PBS. (TIF)