Search

Th1 and Th2 cytokines determine the outcome of Leishmania major infection and immune protection depends mainly on memory T cells induced during vaccination. This largely hinges on the nature and type of memory T cells produced. In this study, transgenic Leishmania major strains expressing membrane-associated ovalbumin (mOVA) and soluble ovalbumin (sOVA) were used as a model to study whether fully differentiated Th1/Th2 and Th17 cells can recall immune memory and tolerate pathogen manipulation. Naïve OT-II T cells were polarised in vitro into Th1/Th2 cells, and these cells were transferred adoptively into recipient mice. Following the transferral of the memory cells, the recipient mice were challenged with OVA transgenic Leishmania major and a wild-type parasite was used a control. The in vitro-polarised T helper cells continued to produce the same cytokine signatures after being challenged by both forms of OVA-expressing Leishmania major parasites in vivo. This suggests that antigen-experienced cells remain the same or unaltered in the face of OVA-transgenic Leishmania major. Such ability of these antigen-experienced cells to remain resilient to manipulation by the parasite signifies that vaccines might be able to produce immune memory responses and defend against parasitic immune manipulation in order to protect the host from infection.

Schistosoma mansoni uses different mechanisms to escape its host's immunity. Understanding the ability of memory T cells to withstand this pathogen's manipulation is important for the development of effective vaccines against this immunomodulatory pathogen. In this study, ovalbumin (OVA) transgenic S. mansoni is used as a tool to investigate whether fully differentiated Th1, Th2 and Th17 cells are able to withstand pathogen manipulation. Naïve T cells from OT-II T cell receptor transgenic mice with a specificity for OVA were differentiated into Th1, Th2, and Th17 polarised memory cells in vitro. These cells were adoptively transferred into recipient mice to investigate whether these polarised immune memory T cells are resilient in the face of pathogen-mediated manipulation. After transferring memory cells, mice were challenged with OVA-transduced S. mansoni eggs as well as wild-type controls. The in vitro differentiated Th1, Th2 and Th17 memory cells continued to produce the same cytokines when challenged by OVA-expressing S. mansoni eggs as to these they produced when transferred in vivo, suggesting that the Th phenotypes of the memory T cells remains unaltered in the face of stimulation by S. mansoni . The ability of memory T cells to remain resilient to manipulation by the parasite suggests that vaccines might be able to produce immune memory responses able to withstand S. mansoni immune manipulation and hence protect the host from infection.

The primary flavonoid, pinocembrin, is thought to have a variety of medical uses which relate to its reported anti-oxidant, anti-inflammatory, anti-microbial and anti-cancer properties. Some studies have reported that this flavonoid has anti-fibrotic activities. In this study, we investigated whether pinocembrin would impede fibrosis, dampen inflammation and improve lung function in a large animal model of pulmonary fibrosis. Fibrosis was induced in two localized lung segments in each of the 10 sheep participating in the study. This was achieved via two infusions of bleomycin delivered bronchoscopically at a two-week interval. Another lung segment in the same sheep was left untreated, and was used as a healthy control. The animals were kept for a little over 5 weeks after the final infusion of bleomycin. Pinocembrin, isolated from Eucalyptus leaves, was administered to one of the two bleomycin damaged lung segments at a dose of 7 mg. This dose was given once-weekly over 4-weeks, starting one week after the final bleomycin infusion. Lung compliance (as a measure of stiffness) was significantly improved after four weekly administrations of pinocembrin to bleomycin-damaged lung segments. There were significantly lower numbers of neutrophils and inflammatory cells in the bronchoalveolar lavage of bleomycin-infused lung segments that were treated with pinocembrin. Compared to bleomycin damaged lung segments without drug treatment, pinocembrin administration was associated with significantly lower numbers of immuno-positive CD8+ and CD4+ T cells in the lung parenchyma. Histopathology scoring data showed that pinocembrin treatment was associated with significant improvement in inflammation and overall pathology scores. Hydroxy proline analysis showed that the administration of pinocembrin did not reduce the increased collagen content that was induced by bleomycin in this model. Analyses of Masson's Trichrome stained sections showed that pinocembrin treatment significantly reduced the connective tissue content in lung segments exposed to bleomycin when compared to bleomycin-infused lungs that did not receive pinocembrin. The striking anti-inflammatory and modest anti-fibrotic remodelling effects of pinocembrin administration were likely linked to the compound's ability to improve lung pathology and functional compliance in this animal model of pulmonary fibrosis., Competing Interests: We have read the journal’s policy and the authors of this manuscript have the following competing interests: AC is the CEO of Gretals Australia Pty Ltd. Gretals Australia Pty Ltd has an interest in the development of pinocembrin for lung diseases. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Schistosoma mansoni eggs can influence immune responses directed at them, and the mechanisms by which this is achieved are being unravelled. Going towards, developing effective tools for the study of how S. mansoni influences naïve T cells, we have developed S. mansoni eggs expressing chicken ovalbumin (OVA), using a lentiviral transduction system. Indeed, such a parasite could be used in conjunction with cells from OT-II transgenic mice as a source of naïve, antigen-specific T cells. The expression of the transgenic protein was confirmed by real-time RT-PCR of OVA-specific mRNA and western blotting using polyclonal antibodies specific for OVA. T cells from OT-II transgenic mice expressing a T cell receptor specific for the OVA 323-339 peptide recognised the OVA-transduced S. mansoni eggs. Using flow cytometry on CFSE-labelled OT-II splenocytes, we demonstrated that OVA-transduced eggs elicit higher OT-II proliferative responses than untransduced eggs. The OT-II T cells also produced TNF-α and IFN-γ following exposure to OVA-transduced eggs. In addition, moderate amounts of IL-6 and IL-17A were also detected. In contrast, no IL-10, IL-4 and IL-2 were detected in cultures, whether the cells were stimulated with transduced or untransduced eggs. Thus, the cytokine signatures showed the transfected eggs induced predominantly a Th1 response, with a small amount of IL-6 and IL-17., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Parasites comprise diverse and complex organisms, which substantially impact human and animal health. Most parasites have complex life-cycles, and by virtue of co-evolution have developed multifaceted, often life-cycle stage-specific relationships with the immune system of their hosts. The complexity in the biology of many parasites often limits our knowledge of parasite-specific immune responses, to in vitro studies only. The relatively recent development of methods to stably manipulate the genetic make-up of many parasites has allowed a better understanding of host-parasite interactions, particularly in vivo. In this regard, the use of transgenic parasites can facilitate the study of immunomodulatory mechanisms under in vivo conditions. Therefore, in this review, we specifically highlighted the current developments in the use of transgenic parasites to unravel the host's immune response to different life-cycle stages of some key parasite species such as Leishmania, Schistosoma, Toxoplasma, Plasmodium and Trypanosome and to some degree, the use of transgenic nematode parasites is also briefly discussed.

M cells play a pivotal role in the induction of immune responses within the mucosa-associated lymphoid tissues. M cells exist principally in the follicle-associated epithelium (FAE) of the isolated solitary lymphoid follicles as well as in the lymphoid follicles of nasopharynx-associated lymphoid tissue and gut associated lymphoid tissue (GALT). Through lymphatic cannulation it is possible to investigate local immune responses induced following nasal Ag delivery in sheep. Hence, identifying sheep M cell markers would allow the targeting of M cells to offset the problem of trans-epithelial Ag delivery associated with inducing mucosal immunity. Sheep cDNA from the tonsils of the oropharynx and nasopharynx was PCR amplified using Glycoprotein-2 (GP 2 )-specific primers and expressed as a poly-His-tagged recombinant sheep GP 2 (56 kDa) in HEK293 cells. The recombinant GP 2 protein was purified using Ni-NTA affinity chromatography and polyclonal serum against the protein was raised in rats. The antiserum recognized the recombinant sheep GP 2 and purified rat IgG against GP 2 stained M cells in sections of sheep tonsils from nasopharynx and oropharynx. M cells were found to be present in epithelium of the palatine tonsils (oropharynx), pharyngeal tonsils as well as tubal tonsils (nasopharynx). They were also present in the FAE of the scattered lymphoid follicles over the base of the nasopharynx. Thus, GP 2 has been identified to be an important M cell marker of nasopharynx and oropharynx-associated lymphoid tissues in sheep., (Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.)

Mucosal-associated invariant T (MAIT) cells produce inflammatory cytokines and cytotoxic granzymes in response to by-products of microbial riboflavin synthesis. Although MAIT cells are protective against some pathogens, we reasoned that they might contribute to pathology in chronic bacterial infection. We observed MAIT cells in proximity to Helicobacter pylori bacteria in human gastric tissue, and so, using MR1-tetramers, we examined whether MAIT cells contribute to chronic gastritis in a mouse H. pylori SS1 infection model. Following infection, MAIT cells accumulated to high numbers in the gastric mucosa of wild-type C57BL/6 mice, and this was even more pronounced in MAIT TCR transgenic mice or in C57BL/6 mice where MAIT cells were preprimed by Ag exposure or prior infection. Gastric MAIT cells possessed an effector memory Tc1/Tc17 phenotype, and were associated with accelerated gastritis characterized by augmented recruitment of neutrophils, macrophages, dendritic cells, eosinophils, and non-MAIT T cells and by marked gastric atrophy. Similarly treated MR1 -/- mice, which lack MAIT cells, showed significantly less gastric pathology. Thus, we demonstrate the pathogenic potential of MAIT cells in Helicobacter -associated immunopathology, with implications for other chronic bacterial infections., (Copyright © 2018 by The American Association of Immunologists, Inc.)

The inflammatory cascade is a multifactorial process regulated by interwoven cytokine and growth factor networks. This review summarizes the emerging evidence that implicate activin A and follistatin in inflammatory processes. Our recent studies have determined that activin A is released early in the cascade of circulatory cytokines during systemic inflammatory episodes, roughly coincident with tumour necrosis factor (TNF)-alpha and before interleukin (IL)-6 and follistatin. The source(s) of this activin A are not yet established, but prime candidates are monocytes/macrophages, other immune cell types or vascular endothelial cells. Clinical data are limited, but activin beta(A) subunit mRNA or activin A protein is elevated in inflammatory bowel diseases and inflammatory arthropathies, and circulating concentrations of follistatin are elevated in patients with sepsis. In more mechanistic approaches, in vitro studies show that activin A can have both pro- and anti-inflammatory actions on key inflammatory mediators such as TNFalpha, IL-1beta and IL-6. Furthermore, there is emerging understanding of how the intracellular signaling pathway for activin A, incorporating Smads, may interact with and be modulated by other key regulatory cytokines and growth factors.

The relatively low efficacy of DNA vaccines in inducing immune responses, especially in large animal species and humans, has impaired their practical use. Despite considerable effort expended on improving DNA vaccine delivery, only minute amounts of Ag are available for immune induction following DNA vaccination. Two complementary strategies have been used to improve and modulate the immune response induced by DNA vaccines: (i) supplementing DNA vaccines with plasmids encoding cytokines and (ii) targeting the Ag encoded by DNA vaccine through genetically fusing the Ag to molecules binding cell surface receptors. This paper reviews recent progress in these two areas and possible mechanisms responsible for the observed effects.

Lymphocyte recruitment from blood into the lymph node is thought to be initiated by the presence of antigen. In this study, we have used lymphatic cannulation in sheep to demonstrate that the adjuvant ISCOMATRIX can induce dramatic lymph node activation in the absence of antigen. Consistent patterns of node shutdown (decreased output) and cell recruitment (increased output) with minimal blast cell responses were observed indicating that an antigen-specific immune response is not required. Production of IL-6, IL-8 and IFN-gamma, and the transient presence of red blood cells and neutrophils in the efferent lymph were associated with changes in efferent lymph cell trafficking. These early events may facilitate the screening of low frequency antigen-specific cells for binding to antigen and the subsequent amplification of the immune response.

The c-rel protooncogene encodes a subunit of the NF-kappa B-like family of transcription factors. Mice lacking Rel are defective in mitogenic activation of B and T lymphocytes and display impaired humoral immunity. In an attempt to identify changes in gene expression that accompany the T-cell stimulation defects associated with the loss of Rel, we have examined the expression of cell surface activation markers and cytokine production in mitogen-stimulated Rel-/- T cells. The expression of cell surface markers including the interleukin 2 receptor alpha (IL-2R alpha) chain (CD25), CD69 and L-selectin (CD62) is normal in mitogen-activated Rel-/- T cells, but cytokine production is impaired. In Rel-/- splenic T cell cultures stimulated with phorbol 12-myristate 13-acetate and ionomycin, the levels of IL-3, IL-5, granulocyte- macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor alpha (TNF-alpha), and gamma interferon (IFN-gamma) were only 2- to 3-fold lower compared with normal T cells. In contrast, anti-CD3 and anti-CD28 stimulated Rel-/- T cells, which fail to proliferate, make little or no detectable cytokines. Exogenous IL-2, which restitutes the proliferative response of the anti-CD3- and anti-CD28-treated Rel-/- T cells, restores production of IL-5, TNF-alpha, and IFN-gamma, but not IL-3 and GM-CSF expression to approximately normal levels. In contrast to mitogen-activated Rel-/- T cells, lipopolysaccharide-stimulated Rel-/- macrophages produce higher than normal levels of GM-CSF. These findings establish that Rel can function as an activator or repressor of gene expression and is required by T lymphocytes for production of IL-3 and GM-CSF.