Facilitated Peptide Transport via the Mucosal Epithelium

A hallmark of autoimmunity is the breakdown of tolerance and generation of effector responses against self-antigens. Re-establishment of tolerance in autoimmune disorders was always the most desired treatment option; however, despite many efforts, clinical trials have been largely unsuccessful. This also applies to the generation of oral tolerance, which seems to be a default response type of the mucosa-associated lymphoid tissues to harmless antigens. In this study, we report improved efficacy of oral tolerance induction by coupling antigen with the newly identified mucosal carrier peptide 13C. Antigen coupled to 13C is efficiently taken up in the gastrointestinal tract and could be visualized in cells of the lamina propria. Oral, rectal, or nasal treatment effectively induced the proliferation of antigen-specific T cells with some increase in the frequency of regulatory T cells. In a model of delayed-type hypersensitivity, especially intrarectal tolerization treatment resulted in reduced footpad swelling, demonstrating a moderate tolerogenic effect of mucosal treatment with 13C coupled antigen. Coupling of antigens to a transmucosal carrier, therefore, is a promising tool to improve the efficacy of vaccination via mucosal surfaces

The gastrointestinal nematode Trichostrongylus colubriformis down-regulates immune gene expression in migratory cells in afferent lymph

Background: Gastrointestinal nematode (GIN) infections are the predominant cause of economic losses in sheep. Infections are controlled almost exclusively by the use of anthelmintics which has lead to the selection of drug resistant nematode strains. An alternative control approach would be the induction of protective immunity to these parasites. This study exploits an ovine microarray biased towards immune genes, an artificially induced immunity model and the use of pseudo-afferent lymphatic cannulation to sample immune cells draining from the intestine, to investigate possible mechanisms involved in the development of immunity.\ud \ud Results: During the development of immunity to, and a subsequent challenge infection with Trichostrongylus colubriformis, the transcript levels of 2603 genes of cells trafficking in afferent intestinal lymph were significantly modulated (P < 0.05). Of these, 188 genes were modulated more than 1.3-fold and involved in immune function. Overall, there was a clear trend for down-regulation of many genes involved in immune functions including antigen presentation, caveolar-mediated endocytosis and protein ubiquitination. The transcript levels of TNF receptor associated factor 5 (TRAF5), hemopexin (HPX), cysteine dioxygenase (CDO1), the major histocompatability complex Class II protein (HLA-DMA), interleukin-18 binding protein (IL-18BP), ephrin A1 (EFNA1) and selenoprotein S (SELS) were modulated to the greatest degree.\ud \ud Conclusions: This report describes gene expression profiles of afferent lymph cells in sheep developing immunity to nematode infection. Results presented show a global down-regulation of the expression of immune genes which may be reflective of the natural temporal response to nematode infections in livestock

Increased Expression of Interleukin-5 (IL-5), IL-13, and Tumor Necrosis Factor Alpha Genes in Intestinal Lymph Cells of Sheep Selected for Enhanced Resistance to Nematodes during Infection with Trichostrongylus colubriformis

Cytokine gene expression in cells migrating in afferent and efferent intestinal lymph was monitored for extended time periods in individual sheep experimentally infected with the nematode Trichostrongylus colubriformis. Animals from stable selection lines with increased levels of either genetic resistance (R) or susceptibility (S) to nematode infection were used. Genes for interleukin-5 (IL-5), IL-13, and tumor necrosis factor alpha (TNF-α), but not for IL-4, IL-10, or gamma interferon (IFN-γ), were consistently expressed at higher levels in both afferent and efferent lymph cells of R sheep than in S sheep. However, only minor differences were observed in the surface phenotypes and antigenic and mitogenic responsiveness of cells in intestinal lymph between animals from the two selection lines. The IL-4 and IL-10 genes were expressed at higher levels in afferent lymph cells than in efferent lymph cells throughout the course of the nematode infection in animals of both genotypes, while the proinflammatory TNF-α gene was relatively highly expressed in both lymph types. These relationships notwithstanding, expression of the IL-10 and TNF-α genes declined significantly in afferent lymph cells but not in efferent lymph cells during infection. Collectively, the results showed that R-line sheep developed a strong polarization toward a Th2-type cytokine profile in immune cells migrating in lymph from sites where the immune response to nematodes was initiated, although the IFN-γ gene was also expressed at moderate levels. Genes or alleles that predispose an animal to develop this type of response appear to have segregated with the R selection line and may contribute to the increased resistance of these animals

Identification of Peptide Mimics of a Glycan Epitope on the Surface of Parasitic Nematode Larvae.

Phage display was used to identify peptide mimics of an immunologically protective nematode glycan (CarLA) by screening a constrained C7C peptide library for ligands that bound to an anti-CarLA mAb (PAB1). Characterisation of these peptide mimotopes revealed functional similarities with an epitope that is defined by PAB1. Mimotope vaccinations of mice with three selected individual phage clones facilitated the induction of antibody responses that recognised the purified, native CarLA molecule which was obtained from Trichostrongylus colubriformis. Furthermore, these mimotopes are specifically recognised by antibodies in the saliva of animals that were immune to natural polygeneric nematode challenge. This shows that antibodies to the PAB1 epitope form part of the mucosal polyclonal anti-CarLA antibody response of nematode immune host animals. This demonstrates that the selected peptide mimotopes are of biological relevance. These peptides are the first to mimic the PAB1 epitope of CarLA, a defined larval glycan epitope which is conserved between many nematode species

Biopanning results in the identification of phage clones that bind to mAb PAB1.

<p>Immobilised mAb PAB1 recognised a selection of purified phage clones diluted 1:20, negative control: VCSM13.</p

Recognition of peptides by salivary IgA.

<p>Plates were coated 2 μg/ml of individual peptides or with purified CarLA (2 μg/ml). A CarLA-negative saliva pool was used to test for non-specific binding. Peptides PAB1.C7C-3, -4, 5-, 16-, 18 and 37 were recognised by salivary IgA from an anti-CarLA positive pool. Serial dilutions of saliva pools were used in assays and results from 1:10 dilutions presented. Data are representative of at least 3 independent repeat assays.</p

Vaccination against a mimotope induces an antibody response that recognises the native larval nematode glycan CarLA.

<p>Groups of mice (n = 3) were vaccinated twice at weeks 0 and 2 with individual phage clones PAB1.C7C-3, -4 or -16. Serum samples from weeks 0, 2 and 4 were analysed by ELISA for the presence of antibodies that bound to immobilised native CarLA, which revealed a significant increases (P < 0.05) in antibody levels following vaccination. Data are presented as means + SE of OD (n = 3).</p

Pre-absorption of saliva with peptides resulted in selective depletion of peptide specific IgA.

<p>Saliva was pre-absorbed with peptides immobilised on ELISA plates. Non-bound peptide specific IgA was then detected on plates coated with 5 μg/ml of individual peptides. This pre-absorption of saliva samples resulted in a reduction of PAB1.C7C-4 and -16 specific binding by approximately 50%. Pre-absorption with PAB1.C7C-3 did not reduce IgA reactivity. CarLA pre-absorption at 2 μg/ml was included as a positive control.</p