Emily Kimmel

Select Plant Tannins Induce IL-2Rα Up-Regulation and Augment Cell Division in γδ T Cells

γδ T cells are innate immune cells that participate in host responses against many pathogens and cancers. Recently, phosphoantigen-based drugs, capable of expanding γδ T cells in vivo, entered clinical trials with the goal of enhancing innate immune system functions. Potential shortcomings of these drugs include the induction of nonresponsiveness upon repeated use and the expansion of only the Vδ2 subset of human γδ T cells. Vδ1 T cells, the major tissue subset, are unaffected by phosphoantigen agonists. Using FACS-based assays, we screened primary bovine cells for novel γδ T cell agonists with activities not encompassed by the current treatments in an effort to realize the full therapeutic potential of γδ T cells. We identified γδ T cell agonists derived from the condensed tannin fractions of Uncaria tomentosa (Cat’s Claw) and Malus domestica (apple). Based on superior potency, the apple extract was selected for detailed analyses on human cells. The apple extract was a potent agonist for both human Vδ1 and Vδ2 T cells and NK cells. Additionally, the extract greatly enhanced phosphoantigen-induced γδ T cell expansion. Our analyses suggest that a tannin-based drug may complement the phosphoantigen-based drugs, thereby enhancing the therapeutic potential of γδ T cells.

Polysaccharides derived from Yamoa™ (Funtumia elastica) prime γδ T cells in vitro and enhance innate immune responses in vivo

Yamoa (ground bark of Funtumia elastica tree) is marketed and sold as a dietary supplement with anecdotal therapeutic effects in the treatment of asthma and hay fever. We determined that Yamoa and Yamoa-derived polysaccharides affected innate immunity, in part, by priming gammadelta T cells. Gene expression patterns in purified bovine gammadelta T cells and monocytes induced by Yamoa were similar to those induced by ultrapure lipopolysaccharide (uLPS). In the presence of accessory cells, Yamoa had priming effects that were similar to those of LPS on bovine and murine gammadelta T cells, but much more potent than LPS on human gammadelta T cells. The bioactive component of Yamoa was delineated to a complex polysaccharide fraction (Yam-I). Intraperitoneal injection of Yamoa and Yam-I in mice induced rapid increases in peritoneal neutrophils directed by changes in chemokine expression. In support of a unique agonist found in Yam-I, similar peritonitis responses were also observed in TLR4- and MyD88-deficient mice. Therapeutic treatment with Yam-I resulted in decreased bacterial counts in feces from mice with Salmonella enterica serotype typhimurium (ST)-induced enterocolitis. This characterization of the immune stimulatory properties of polysaccharides derived from Yamoa suggests mechanisms for the anecdotal positive effects of its ingestion and that these polysaccharides show potential for application in innate protection from disease.

Oligomeric procyanidins stimulate innate antiviral immunity in dengue virus infected human PBMCs

Oligomeric procyanidins (OPCs) have been shown to have antiviral and immunostimulatory effects. OPCs isolated from non-ripe apple peel were tested for capacity to reduce dengue virus (DENV) titers. Similar to published accounts, OPCs exhibited direct antiviral activity. The possibility of enhanced innate immune protection was also tested by measuring and characterizing gene and protein expression induced by OPCs during DENV infection. Treatment of DENV-infected human PBMCs with OPCs decreased viral titers and affected the expression of critical innate antiviral immune products. OPCs enhanced expression of MXI and IFNB transcripts in high MOI DENV infected PBMC cultures, and phosphorylation of STAT2 in response to recombinant type I IFN (IFN I). During low MOI infection, addition of OPCs increased expression of STAT1 transcripts, MHC I and TNFα protein production. Thus, OPCs exhibited innate immune stimulation of cells in DENV-infected cultures and uninfected cells treated with IFN I. While OPCs from a number of sources are known to exhibit antiviral effects, their mechanisms are not precisely defined. The capacity of OPCs to increase sensitivity to IFN I could be broadly applicable to many viral infections and two separate antiviral mechanisms suggest that OPCs may represent a novel, robust antiviral therapy.

Solute Carrier 11A1 Is Expressed by Innate Lymphocytes and Augments Their Activation

Solute carrier 11A1 (SLC11A1) is a divalent ion transporter formerly known as the natural resistance–associated macrophage protein (NRAMP1) and the Bcg/Lsh/Ity locus. SLC11A1 was thought to be exclusively expressed in monocyte/macrophages and to have roles in phagosome maturation and cell activation. We characterized the expression of SLC11A1 in the majority of human and bovine γδ T cells and NK cells and in human CD3+CD45RO+ T cells. Consistent with a role for iron-dependent inhibition of protein tyrosine phosphatases, SLC11A1+ lymphocytes were more prone to activation and retained tyrosine phosphorylation. Transfection of SLC11A1 into a human γδ T cell–like line rendered the cells more prone to activation. Nonadherent splenocytes from wild-type mice expressed significantly greater IFN-γ compared with cells from Sv/129 (SLC11A1−/−) mice. Our data suggest that SLC11A1 has a heretofore unknown role in activation of a large subset of innate lymphocytes that are critical sources of IFN-γ. SLC11A1+ animals have enhanced innate IFN-γ expression in response to Salmonella infection compared with SLC11A1− mice, which include commonly used inbred laboratory mice. Expression of SLC11A1 in innate lymphocytes and its role in augmenting their activation may account for inconsistencies in studies of innate lymphocytes in different animal models.

Amphotericin B stimulates γδ T and NK cells, and enhances protection from Salmonella infection:

Amphotericin B (AmB) is a commonly used antifungal drug, with well-documented effects on cellular immune responses. We determined that AmB-stimulated γδ T-cell activation and proliferation in vitro at very low concentrations. AmB also enhanced IFN-γ production by NK cells in combination with IL-18. AmB had a greater effect on IFN-γ production in cells isolated from very young animals. Although innate immunostimulatory aspects of AmB have been defined, AmB has not been extensively applied in non-fungal infection settings. Given that γδ T cells are increased and activated in Salmonella infection in cattle, we assessed the effects of AmB in protection from Salmonella enterocolitis in calves. One injection of AmB, at approximately one-tenth of the concentration used in human patients to counter fungal infection, or saline control, was delivered intravenously to calves prior to infection with Salmonella. This single injection caused no adverse effects, reduced disease symptoms from Salmonella enterocolitis and significantly reduced Salmonella bacteria shed in feces of infected animals. Our findings suggest that AmB may be an inexpensive and readily available prophylactic approach for the prevention of bacterial infection in calves.

Type I Interferon Counters or Promotes Coxiella burnetii Replication Dependent on Tissue

ABSTRACT Coxiella burnetii is an intracellular pathogen and the cause of Q fever. Gamma interferon (IFN-γ) is critical for host protection from infection, but a role for type I IFN in C. burnetii infection has not been determined. Type I IFN supports host protection from a related pathogen, Legionella pneumophila, and we hypothesized that it would be similarly protective in C. burnetii infection. In contrast to our prediction, IFN-α receptor-deficient (IFNAR−/−) mice were protected from C. burnetii-induced infection. Therefore, the role of type I IFN in C. burnetii infection was distinct from that in L. pneumophila. Mice treated with a double-stranded-RNA mimetic were protected from C. burnetii-induced weight loss through an IFNAR-independent pathway. We next treated mice with recombinant IFN-α (rIFN-α). When rIFN-α was injected by the intraperitoneal route during infection, disease-induced weight loss was exacerbated. Mice that received rIFN-α by this route had dampened interleukin 1β (IL-1β) expression in bronchoalveolar lavage fluids. However, when rIFN-α was delivered to the lung, bacterial replication was decreased in all tissues. Thus, the presence of type I IFN in the lung protected from infection, but when delivered to the periphery, type I IFN enhanced disease, potentially by dampening inflammatory cytokines. To better characterize the capacity for type I IFN induction by C. burnetii, we assessed expression of IFN-β transcripts by human macrophages following stimulation with lipopolysaccharide (LPS) from C. burnetii. Understanding innate responses in C. burnetii infection will support the discovery of novel therapies that may be alternative or complementary to the current antibiotic treatment.

Oral delivery of oligomeric procyanidins in Apple Poly® enhances type I IFN responses in vivo

Type I IFN signaling is a central pathway that provides critical innate protection from viral and bacterial infection and can have regulatory outcomes in inflammatory settings. We determined previously that OPCs contained in the dietary supplement APP enhanced responses to type I IFN in vitro. Here, we confirm that OPCs from two different sources significantly increased pSTAT1, whereas a monomeric form of procyanidin did not. We hypothesized that similar responses could be induced in vivo following ingestion of APP. Ingestion of APP before injection of polyI:C enhanced in vivo responses to type I IFNs in mice. When human subjects ingested APP, enhanced responses to type I IFN and enhanced pSTAT1 ex vivo were detected, whereas ingestion of RES, a monomeric polyphenol, induced minimal such changes. Polyphenols are best known for induction of anti‐inflammatory and antioxidant responses; however, our findings suggest a unique, nonantioxidant aspect of OPCs that is broadly applicable to many disease settings. The capacity of oral OPCs to enhance type I IFN signaling in vivo can augment innate protection and may, in part, contribute to the noted anti‐inflammatory outcome of ingestion of OPCs from many sources.