tretinoin and Salmonella-Infections--Animal

Developing efficacious vaccines against enteric diseases is a global challenge that requires a better understanding of cellular recruitment dynamics at the mucosal surfaces. The current paradigm of T cell homing to the gastrointestinal (GI) tract involves the induction of α4β7 and CCR9 by Peyer's patch and mesenteric lymph node (MLN) dendritic cells (DCs) in a retinoic acid-dependent manner. This paradigm, however, cannot be reconciled with reports of GI T cell responses after intranasal (i.n.) delivery of antigens that do not directly target the GI lymphoid tissue. To explore alternative pathways of cellular migration, we have investigated the ability of DCs from mucosal and nonmucosal tissues to recruit lymphocytes to the GI tract. Unexpectedly, we found that lung DCs, like CD103(+) MLN DCs, up-regulate the gut-homing integrin α4β7 in vitro and in vivo, and induce T cell migration to the GI tract in vivo. Consistent with a role for this pathway in generating mucosal immune responses, lung DC targeting by i.n. immunization induced protective immunity against enteric challenge with a highly pathogenic strain of Salmonella. The present report demonstrates novel functional evidence of mucosal cross talk mediated by DCs, which has the potential to inform the design of novel vaccines against mucosal pathogens.

Topics: Administration, Intranasal; Adoptive Transfer; Animals; Antigens, CD; Antigens, Surface; Basic-Leucine Zipper Transcription Factors; Cell Movement; Dendritic Cells; Fingolimod Hydrochloride; Gastrointestinal Tract; Immunity, Mucosal; Immunization; Integrins; Intestinal Mucosa; Lectins, C-Type; Lung; Mannose-Binding Lectins; Mice; Mice, Inbred C57BL; Propylene Glycols; Receptors, CCR; Salmonella; Salmonella Infections, Animal; Signal Transduction; Sphingosine; T-Lymphocytes; Transforming Growth Factor beta; Tretinoin

Cathelicidins are a family of antimicrobial peptides prominent in the host defense mechanisms of several mammalian species. In addition to their antimicrobial activities, these peptides have been implicated in wound healing, angiogenesis, and other innate immune mechanisms. To investigate the regulatory mechanisms of cathelicidin gene expression, we conducted in vitro experiments evaluating the bone marrow cell expression of two porcine cathelicidins, PR-39 and protegrin, and cloned and evaluated the promoter sequence of PR-39. In addition, we evaluated in vivo kinetics of cathelicidin gene expression in pigs during an infection with Salmonella enterica serovar Typhimurium. Lipopolysaccharide (LPS) increased PR-39 and protegrin mRNA expression, which was ameliorated by polymyxin B. Concentrations of PR-39 in supernatants from bone marrow cell cultures were increased 10-fold after LPS stimulation. Similarly, interleukin-6 (IL-6) and all-trans retinoic acid (RA) markedly induced cathelicidin gene expression. To verify the transcriptional activation of the PR-39 gene by these agents, we made a PR-39 promoter-luciferase construct containing the full-length PR-39 promoter driving luciferase gene expression and transiently transfected PK-15 epithelial cells. RA and IL-6 increased luciferase activity in PK-15 cells transfected with the PR-39 promoter-luciferase reporter. Similarly, Salmonella-challenged pigs showed increased expression of PR-39 and protegrin mRNA in bone marrow cells at 6 and 24 h postchallenge. Taken together, these findings show that bacterial products (LPS), IL-6, RA, and Salmonella infection enhance the expression of the cathelicidins, PR-39 and protegrin, in bone marrow progenitor cells, and we suggest that extrinsic modulation of this innate host defense mechanism may be possible.

Topics: Amino Acid Sequence; Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Base Sequence; Cathelicidins; Cells, Cultured; Gene Expression Regulation; Interleukin-6; Lipopolysaccharides; Molecular Sequence Data; Promoter Regions, Genetic; Salmonella Infections, Animal; Salmonella typhimurium; Swine; Tretinoin