Trichinella spiralis: modulation of experimental autoimmune encephalomyelitis in DA rats

Mechanisms of modulation of experimental autoimmune encephalomyelitis by chronic Trichinella spiralis infection in Dark Agouti rats

Trichinella spiralis is a helminth that provokes Th2 and anti-inflammatory type responses in an infected host. Our previous studies using Dark Agouti (DA) rats indicated that T. spiralis infection reduced experimental autoimmune encephalomyelitis (EAE) severity in rats. The aim of this study was to analyse the mechanisms underlying EAE suppression driven by T. spiralis infection. Reduced clinical and histological manifestations of the disease were accompanied by increased IL-4 and IL-10 production and decreased IFN-gamma and IL-17 production in draining lymph node cells. This indicates that T. spiralis infection successfully maintains a Th2 cytokine bias regardless of EAE induction. High IL-10 signifies parasite-induced anti-inflammatory and/or regulatory cell responses. Transfer of splenic T cell-enriched population of cells from T. spiralis-infected rats into EAE immunized rats caused amelioration of EAE and in some cases protection from disease development. This population of cells contained higher proportion of CD4(+) CD25(+) Foxp3(+) regulatory cells and produced high level of IL-10 when compared with uninfected rats.

Infection of non-encapsulated species of Trichinella ameliorates experimental autoimmune encephalomyelitis involving suppression of Th17 and Th1 response

Epidemiological and experimental studies have indicated that helminth infections can ameliorate autoimmune diseases. The present study investigated the amelioration effect of the Trichinella pseudospiralis infection on experimental autoimmune encephalomyelitis (EAE), a T-cell-mediated autoimmune disease of central nervous system (CNS), and expression kinetics of Th17 and Th1 cytokine which play a crucial role in the pathogenesis of EAE. The results indicated that the infection of helminth T. pseudospiralis obviously ameliorated clinical severity and greatly delayed the onset of EAE induced by myelin oligodendrocyte glycoprotein (MOG) immunization. Infection caused much lesser inflammatory infiltration and demyilination in the CNS of infected EAE mice than uninfected EAE mice. The reduced infiltration was also suggested by the expressions of the inflammation cytokines, IL-17, IL-6, IL-1β, IFN-γ, and TNF-α, which were high in the spinal cords of the uninfected EAE mice, but was nearly normal or low in the infected EAE mice. The increased production of MOG-induced IL-17 and IFN-γ and the expression of IL-6, IL-1β, TGF-β in splenocytes after restimulation with MOG was inhibited in the infected EAE mice. On the other hand, the greatly induced Th2 response was observed in the splenocytes of the infected EAE mice. The present study showed that T. pseudospiralis infection can suppresses EAE by reducing the inflammatory infiltration in CNS, likely associated with the suppression of Th17 and Th1 responses by the infection.

Worms to the rescue: can worm glycans protect from autoimmune diseases?

Autoimmune and autoinflammatory diseases represent a significant health burden, especially in Western societies. For the majority of these diseases, no cure exists. Recently, research on parasitic worms (helminths) has demonstrated great potential for whole worms, their eggs or their excretory/secretory proteins in down-regulating inflammatory responses both in vitro and in vivo, in various disease models and, in some cases, even in clinical trials. The worms are thought to induce Th2 and regulatory T cells, interfere with Toll-like receptor (TLR) signaling and to down-regulate Th17 and Th1 responses. The molecular mechanisms underlying the worms' ability to modulate the host immune response are not well understood, and many hypotheses have been proposed to explain the observed immune modulation. Increasing evidence suggests that carbohydrate structures (glycans), for example, phosphorylcholine-modified glycans or Galbeta1-4(Fucalpha1-3)GlcNAc- (Lewis X, Le(X)) containing glycans, expressed by the worms contribute to these modulating properties by their interaction with antigen presenting cells. Helminths express a broad variety of protein- and lipid-linked glycans on their surface and on secretory products. These glycans differ in amount and composition and several of these structures are species specific. However, worms also express glycan antigens that are found in a wide variety of different species. Some of these "common" worm glycans are particularly interesting with regard to regulating host responses, because they have the potential to interact with C-type lectins on dendritic cells and thereby may interfere with T-cell polarization. Helminths and helminth-derived molecules form a novel and promising group of therapeutics for autoinflammatory diseases. However, much has to be learned about the molecular mechanisms behind the helminth-mediated antiinflammatory properties. This review will describe some of the emerging evidence in selected disease areas as well as discuss the putative role of glycans in helminth-mediated immunosuppression.

Parasitic helminths: new weapons against immunological disorders

The prevalence of allergic and autoimmune diseases is increasing in developed countries, possibly due to reduced exposure to microorganisms in childhood (hygiene hypothesis). Epidemiological and experimental evidence in support of this hypothesis is accumulating. In this context, parasitic helminths are now important candidates for antiallergic/anti-inflammatory agents. Here we summarize antiallergic/anti-inflammatory effects of helminths together along with our own study of the effects of Schistosoma mansoni on Th17-dependent experimental arthritis. We also discuss possible mechanisms of helminth-induced suppression according to the recent advances of immunology.

Can infections protect against autoimmunity?

PURPOSE OF REVIEW

It has often been suggested that autoimmune diseases are initiated by certain infectious agents that mimic self-antigens or polyclonally activated autoreactive lymphocytes. An alternative, and not necessarily mutually exclusive, hypothesis that some infections might inhibit the onset of some autoimmune conditions has more recently been explored. In this review, the evidence suggesting that the current rise in the incidence of some autoimmune diseases is attributable to a decrease in the incidence of exposure to certain infections will be discussed.

RECENT FINDINGS

Studies using animal models have shown that some infectious agents or products derived from them have the potential to inhibit the onset of autoimmunity. These studies have led to the suggestion that human autoimmune or allergic diseases might be alleviated by the use of microbial products. There are some data that would support such an observation.

SUMMARY

The incidence of some autoimmune diseases has increased dramatically in recent years in the developed world. Many autoimmune diseases are governed by both genetic and environmental factors. Our immune system has coevolved with infectious agents. There have been marked changes in the exposure to certain infectious agents over the last 70 years. It has been proposed that certain infections of historical importance might inhibit the development of autoimmune disorder. This review highlights studies addressing the ways in which infectious agents might inhibit onset of autoimmunity, and how this might lead to the development of novel therapeutic approaches.

Early life exposure to lipopolysaccharide suppresses experimental autoimmune encephalomyelitis by promoting tolerogenic dendritic cells and regulatory T cells

The rising incidence of autoimmune diseases such as multiple sclerosis (MS) in developed countries might be due to a more hygienic environment, particularly during early life. To investigate this concept, we developed a model of neonatal exposure to a common pathogen-associated molecular pattern, LPS, and determined its impact on experimental autoimmune encephalomyelitis (EAE). Mice exposed to LPS at 2 wk of age showed a delayed onset and diminished severity of myelin oligodendrocyte glycoprotein (MOG)-induced EAE, induced at 12 wk, compared with vehicle-exposed animals. Spinal cord transcript levels of CD3epsilon and F4/80 were lower in LPS- compared with PBS-exposed EAE animals with increased IL-10 levels in the LPS-exposed group. Splenic CD11c(+) cells from LPS-exposed animals exhibited reduced MHC class II and CD83 expression but increased levels of CD80 and CD86 both before and during EAE. MOG-treated APC from LPS-exposed animals stimulated less T lymphocyte proliferation but increased expansion of CD4(+)FoxP3(+) T cells compared with APC from PBS-exposed animals. Neuropathological studies disclosed reduced myelin and axonal loss in spinal cords from LPS-exposed compared with PBS-exposed animals with EAE, and this neuroprotective effect was associated with an increased number of CD3(+)FoxP3(+) immunoreactive cells. Analyses of human brain tissue revealed that FoxP3 expression was detected in lymphocytes, albeit reduced in MS compared with non-MS patients' brains. These findings support the concept of early-life microbial exposure influencing the generation of neuroprotective regulatory T cells and may provide insights into new immunotherapeutic strategies for MS.

Helminths and our immune system: friend or foe?

Helminths are able to modulate and suppress the hosts' immune response in order to promote their own survival. This ability to alter immune responses could be of potential detriment to the host if it interferes with the development of protective immune responses against other infections. However, helminth infections have also been suggested to be beneficial in the control of excessive inflammatory reactions. In this review I will highlight some of the data suggesting both positive and negative effects of helminth infections in humans and in experimental models.