A parasite-derived 68-mer peptide ameliorates autoimmune disease in murine models of Type 1 diabetes and multiple sclerosis

Association of Antibodies to Helminth Defense Molecule 1 With Inflammation, Organomegaly, and Decreased Nutritional Status in Schistosomiasis Japonica

Immunomodulation enhances parasite fitness by reducing inflammation-induced morbidity in the mammalian host, as well as by attenuating parasite-targeting immune responses. Using a whole-proteome differential screening method, we identified Schistosoma japonicum helminth defense molecule 1 (SjHDM-1) as a target of antibodies expressed by S. japonicum-resistant but not S. japonicum-susceptible individuals. In a longitudinal cohort study (n = 644) conducted in a S. japonicum-endemic region of the Philippines, antibody levels to SjHDM-1 did not predict resistance to reinfection but were associated with increased measures of inflammation. Individuals with high levels of anti-SjHDM-1 immunoglobulin G had higher levels of C-reactive protein than those with low anti-SjHDM-1. High anti-SjHDM-1 immunoglobulin G responses were also associated with reduced biomarkers of nutritional status (albumin), as well as decreased anthropometric measures of nutritional status (weight-for-age and height-for-age z scores) and increased measures of hepatomegaly. Our results suggest that anti-SjHDM-1 responses inhibit the immunomodulatory function of SjHDM-1, resulting in increased morbidity rates.

Fasciola hepatica Excretory-Secretory Products (Fh-ES) Either Do Not Affect miRNA Expression Profile in THP-1 Macrophages or the Changes Are Undetectable by a Microarray Technique

Fasciola hepatica is a liver fluke that resides in the bile ducts of various mammals. The parasitosis leads to economic losses in animal production estimated at USD 3.2 billion annually. It is also considered a zoonosis of great significance and a problem for public health affecting 2.4 million people worldwide. Nevertheless, besides the negative aspects of infestation, the antigens released by the fluke, F. hepatica Excretory-Secretory Products (Fh-ES) contain several immunomodulatory molecules that may be beneficial during the course of type I diabetes, multiple sclerosis, ulcerative colitis, or septic shock. This phenomenon is based on the natural abilities of adult F. hepatica to suppress proinflammatory responses. To underline the molecular basis of these mechanisms and determine the role of microRNA (miRNA) in the process, lipopolysaccharide (LPS)-activated THP-1 macrophages were stimulated with Fh-ES, followed by miRNA microarray analyses. Surprisingly, no results indicating changes in the miRNA expression profile were noted (p < 0.05). We discuss potential reasons for these results, which may be due to insufficient sensitivity to detect slight changes in miRNA expression or the possibility that these changes are not regulated by miRNA. Despite the negative data, this work may contribute to the future planning of experiments by other researchers.

The Parasite-Derived Peptide, FhHDM-1, Selectively Modulates miRNA Expression in β-Cells to Prevent Apoptotic Pathways Induced by Proinflammatory Cytokines

We have previously identified a parasite-derived peptide, FhHDM-1, that prevented the progression of diabetes in nonobese diabetic (NOD) mice. Disease prevention was mediated by the activation of the PI3K/Akt pathway to promote β-cell survival and metabolism without inducing proliferation. To determine the molecular mechanisms driving the antidiabetogenic effects of FhHDM-1, miRNA:mRNA interactions and in silico predictions of the gene networks were characterised in β-cells, which were exposed to the proinflammatory cytokines that mediate β-cell destruction in Type 1 diabetes (T1D), in the presence and absence of FhHDM-1. The predicted gene targets of miRNAs differentially regulated by FhHDM-1 mapped to the biological pathways that regulate β-cell biology. Six miRNAs were identified as important nodes in the regulation of PI3K/Akt signaling. Additionally, IGF-2 was identified as a miRNA gene target that mediated the beneficial effects of FhHDM-1 on β-cells. The findings provide a putative mechanism by which FhHDM-1 positively impacts β-cells to permanently prevent diabetes. As β-cell death/dysfunction underlies diabetes development, FhHDM-1 opens new therapeutic avenues.

The helminth-derived peptide, FhHDM-1, reverses the trained phenotype of NOD bone-marrow-derived macrophages and regulates proinflammatory responses

We implicate a phenotype of trained immunity in bone-marrow-derived macrophages in the onset and progression of type 1 diabetes in nonobese diabetic mice. Treatment with FhHDM-1 reversed immune training, reducing histone methylation and glycolysis, and decreasing proinflammatory cytokine production to the same level as macrophages from nondiabetic immune-competent BALB/c mice.

The neurotropic schistosome vs experimental autoimmune encephalomyelitis: are there any winners?

The incidences of multiple sclerosis have risen worldwide, yet neither the trigger nor efficient treatment is known. Some research is dedicated to looking for treatment by parasites, mainly by helminths. However, little is known about the effect of helminths that infect the nervous system. Therefore, we chose the neurotropic avian schistosome Trichobilharzia regenti, which strongly promotes M2 polarization and tissue repair in the central nervous system, and we tested its effect on the course of experimental autoimmune encephalomyelitis (EAE) in mice. Surprisingly, the symptoms of EAE tended to worsen after the infection with T. regenti. The infection did not stimulate tissue repair, as indicated by the similar level of demyelination. Eosinophils heavily infiltrated the infected tissue, and the microglia number increased as well. Furthermore, splenocytes from T. regenti-infected EAE mice produced more interferon (IFN)-γ than splenocytes from EAE mice after stimulation with myelin oligodendrocyte glycoprotein. Our research indicates that the combination of increased eosinophil numbers and production of IFN-γ tends to worsen the EAE symptoms. Moreover, the data highlight the importance of considering the direct effect of the parasite on the tissue, as the migrating parasite may further tissue damage and make tissue repair even more difficult.

Mitochondrial and metabolic dysfunction of peripheral immune cells in multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disorder characterized by the infiltration of inflammatory cells and demyelination of nerves. Mitochondrial dysfunction has been implicated in the pathogenesis of MS, as studies have shown abnormalities in mitochondrial activities, metabolism, mitochondrial DNA (mtDNA) levels, and mitochondrial morphology in immune cells of individuals with MS. The presence of mitochondrial dysfunctions in immune cells contributes to immunological dysregulation and neurodegeneration in MS. This review provided a comprehensive overview of mitochondrial dysfunction in immune cells associated with MS, focusing on the potential consequences of mitochondrial metabolic reprogramming on immune function. Current challenges and future directions in the field of immune-metabolic MS and its potential as a therapeutic target were also discussed.

Effect of macrophage polarization on parasitic protection against type 1 diabetes mellitus

Type 1 diabetes mellitus is a chronic disease caused by the destruction of pancreatic beta cells. Based on the hygiene hypothesis, a growing body of evidence suggests a negative association between parasitic infections and diabetes in humans and animal models. The mechanism of parasite-mediated prevention of type 1 diabetes mellitus may be related to the adaptive and innate immune systems. Macrophage polarization is a new paradigm for the treatment of type 1 diabetes mellitus, and different host macrophage subsets play various roles during parasite infection. Proinflammatory cytokines are released by M1 macrophages, which are important in the development of type 1 diabetes mellitus. Parasite-activated M2 macrophages prevent the development of type 1 diabetes mellitus and can influence the development of adaptive immune responses through several mechanisms, including Th2 cells and regulatory T cells. Here, we review the role and mechanism of macrophage polarization in parasitic protection against type 1 diabetes mellitus.

The immunomodulatory effects of the C-type lectin protein of Toxocara canis on experimental autoimmune encephalomyelitis

Toxocara canis is a global zoonosis infection that can cause chronic and long-term toxocariasis in their paratenic host. The excretory-secretory (ES) products of T. canis larvae are considered to be responsible for the Th2 polarization and regulatory immune responses in toxocariasis. The C-type lectin family is one of the most prominent components of ES products of T. canis infective larvae. This study aimed to investigate the ameliorative effect of a T. canis C-type lectin recombinant protein (rCTL), on experimental autoimmune encephalomyelitis (EAE) which is a T-cell-mediated autoimmune disease of the central nervous system. C57BL/6 mice were subcutaneously treated with 30 μg rCTL, three times at an interval of 1 week. EAE was induced by myelin oligodendrocyte glycoprotein 35-55 peptide (MOG35-55 peptide) immunization, and weight and clinical scores were evaluated. Real time polymerase chain reaction was performed to evaluate the expression levels of T-bet, Gata3, and Foxp3 in splenocytes. In addition, the levels of interleukin 4, interferon gamma, and tumour growth factor-β (TGF-β) were quantified by enzyme-linked immunosorbent assay in splenocyte culture supernatants. The results indicated that the rCTL decreased clinical disability scores and delayed the onset of EAE. Furthermore, the data showed that rCTL treatment modulated the immune response, which was associated with upregulation of the mRNA expression of the Foxp3 gene and higher production of TGF-β in rCTL-treated mice. This study demonstrated that rCTL might be a potential agent to ameliorate EAE symptoms by stimulating anti-inflammatory responses.

How do parasitic worms prevent diabetes? An exploration of their influence on macrophage and β-cell crosstalk

Diabetes is the fastest growing chronic disease globally, with prevalence increasing at a faster rate than heart disease and cancer. While the disease presents clinically as chronic hyperglycaemia, two distinct subtypes have been recognised. Type 1 diabetes (T1D) is characterised as an autoimmune disease in which the insulin-producing pancreatic β-cells are destroyed, and type 2 diabetes (T2D) arises due to metabolic insufficiency, in which inadequate amounts of insulin are produced, and/or the actions of insulin are diminished. It is now apparent that pro-inflammatory responses cause a loss of functional β-cell mass, and this is the common underlying mechanism of both T1D and T2D. Macrophages are the central immune cells in the pathogenesis of both diseases and play a major role in the initiation and perpetuation of the proinflammatory responses that compromise β-cell function. Furthermore, it is the crosstalk between macrophages and β-cells that orchestrates the inflammatory response and ensuing β-cell dysfunction/destruction. Conversely, this crosstalk can induce immune tolerance and preservation of β-cell mass and function. Thus, specifically targeting the intercellular communication between macrophages and β-cells offers a unique strategy to prevent/halt the islet inflammatory events underpinning T1D and T2D. Due to their potent ability to regulate mammalian immune responses, parasitic worms (helminths), and their excretory/secretory products, have been examined for their potential as therapeutic agents for both T1D and T2D. This research has yielded positive results in disease prevention, both clinically and in animal models. However, the focus of research has been on the modulation of immune cells and their effectors. This approach has ignored the direct effects of helminths and their products on β-cells, and the modulation of signal exchange between macrophages and β-cells. This review explores how the alterations to macrophages induced by helminths, and their products, influence the crosstalk with β-cells to promote their function and survival. In addition, the evidence that parasite-derived products interact directly with endocrine cells to influence their communication with macrophages to prevent β-cell death and enhance function is discussed. This new paradigm of two-way metabolic conversations between endocrine cells and macrophages opens new avenues for the treatment of immune-mediated metabolic disease.

Effects of helminths and anthelmintic treatment on cardiometabolic diseases and risk factors: A systematic review

BACKGROUND

Globally, helminth infections and cardiometabolic diseases often overlap in populations and individuals. Neither the causal relationship between helminth infections and cardiometabolic diseases nor the effect of helminth eradication on cardiometabolic risk have been reviewed systematically in a large number of human and animal studies.

METHODS

We conducted a systematic review assessing the reported effects of helminth infections and anthelmintic treatment on the development and/or severity of cardiometabolic diseases and risk factors. The search was limited to the most prevalent human helminths worldwide. This study followed PRISMA guidelines and was registered prospectively in PROSPERO (CRD42021228610). Searches were performed on December 10, 2020 and rerun on March 2, 2022 using Ovid MEDLINE ALL (1946 to March 2, 2022), Web of Science, Cochrane Library, Global Index Medicus, and Ovid Embase (1974 to March 2, 2022). Randomized clinical trials, cohort, cross-sectional, case-control, and animal studies were included. Two reviewers performed screening independently.

RESULTS

Eighty-four animal and human studies were included in the final analysis. Most studies reported on lipids (45), metabolic syndrome (38), and diabetes (30), with fewer on blood pressure (18), atherosclerotic cardiovascular disease (11), high-sensitivity C-reactive protein (hsCRP, 5), and non-atherosclerotic cardiovascular disease (4). Fifteen different helminth infections were represented. On average, helminth-infected participants had less dyslipidemia, metabolic syndrome, diabetes, and atherosclerotic cardiovascular disease. Eleven studies examined anthelmintic treatment, of which 9 (82%) reported post-treatment increases in dyslipidemia, metabolic syndrome, and diabetes or glucose levels. Results from animal and human studies were generally consistent. No consistent effects of helminth infections on blood pressure, hsCRP, or cardiac function were reported except some trends towards association of schistosome infection with lower blood pressure. The vast majority of evidence linking helminth infections to lower cardiometabolic diseases was reported in those with schistosome infections.

CONCLUSIONS

Helminth infections may offer protection against dyslipidemia, metabolic syndrome, diabetes, and atherosclerotic cardiovascular disease. This protection may lessen after anthelmintic treatment. Our findings highlight the need for mechanistic trials to determine the pathways linking helminth infections with cardiometabolic diseases. Such studies could have implications for helminth eradication campaigns and could generate new strategies to address the global challenge of cardiometabolic diseases.

The helminth derived peptide FhHDM-1 redirects macrophage metabolism towards glutaminolysis to regulate the pro-inflammatory response

We have previously identified an immune modulating peptide, termed FhHDM-1, within the secretions of the liver fluke, Fasciola hepatica, which is sufficiently potent to prevent the progression of type 1 diabetes and multiple sclerosis in murine models of disease. Here, we have determined that the FhHDM-1 peptide regulates inflammation by reprogramming macrophage metabolism. Specifically, FhHDM-1 switched macrophage metabolism to a dependence on oxidative phosphorylation fuelled by fatty acids and supported by the induction of glutaminolysis. The catabolism of glutamine also resulted in an accumulation of alpha ketoglutarate (α-KG). These changes in metabolic activity were associated with a concomitant reduction in glycolytic flux, and the subsequent decrease in TNF and IL-6 production at the protein level. Interestingly, FhHDM-1 treated macrophages did not express the characteristic genes of an M2 phenotype, thereby indicating the specific regulation of inflammation, as opposed to the induction of an anti-inflammatory phenotype per se. Use of an inactive derivative of FhHDM-1, which did not modulate macrophage responses, revealed that the regulation of immune responses was dependent on the ability of FhHDM-1 to modulate lysosomal pH. These results identify a novel functional association between the lysosome and mitochondrial metabolism in macrophages, and further highlight the significant therapeutic potential of FhHDM-1 to prevent inflammation.

Toxocara canis infection worsens the course of experimental autoimmune encephalomyelitis in mice

Toxocara canis, a gastrointestinal parasite of canids, is also highly prevalent in many paratenic hosts, such as mice and humans. As with many other helminths, the infection is associated with immunomodulatory effects, which could affect other inflammatory conditions including autoimmune and allergic diseases. Here, we investigated the effect of T. canis infection on the course of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Mice infected with 2 doses of 100 T. canis L3 larvae 5 weeks prior to EAE induction (the Tc+EAE group) showed higher EAE clinical scores and greater weight loss compared to the non-infected group with induced EAE (the EAE group). Elevated concentrations of all measured serum cytokines (IL-1α, IL-2, IL-4, IL-6, IL-10, IL-17A, IFN-γ and TNF-α) were observed in the Tc+EAE group compared to the EAE group. In the CNS, the similar number of regulatory T cells (Tregs; CD4+FoxP3+Helios+) but their decreased proportion from total CD4+ cells was found in the Tc+EAE group compared to the EAE group. This could indicate that the group Tc+EAE harboured significantly more CD4+ T cells of non-Treg phenotype within the affected CNS. Altogether, our results demonstrate that infection of mice with T. canis worsens the course of subsequently induced EAE. Further studies are, therefore, urgently needed to reveal the underlying pathological mechanisms and to investigate possible risks for the human population, in which exposure to T. canis is frequent.

Targeting the PI3K/Akt signaling pathway in pancreatic β-cells to enhance their survival and function: An emerging therapeutic strategy for type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease caused by the destruction of the insulin-producing β-cells within the pancreas. Islet transplantation represents one cure; however, during islet preparation and post transplantation significant amounts of β-cell death occur. Therefore, prevention and cure of T1D is dependent upon the preservation of β-cell function and the prevention of β-cell death. Phosphoinositide 3-kinase (PI3K)/Akt signaling represents a promising therapeutic target for T1D due to its pronounced effects on cellular survival, proliferation, and metabolism. A growing amount of evidence indicates that PI3K/Akt signaling is a critical determinant of β-cell mass and function. Modulation of the PI3K/Akt pathway, directly (via the use of highly specific protein and peptide-based biologics, excretory/secretory products of parasitic worms, and complex constituents of plant extracts) or indirectly (through microRNA interactions) can regulate the β-cell processes to ultimately determine the fate of β-cell mass. An important consideration is the identification of the specific PI3K/Akt pathway modulators that enhance β-cell function and prevent β-cell death without inducing excessive β-cell proliferation, which may carry carcinogenic side effects. Among potential PI3K/Akt pathway agonists, we have identified a novel parasite-derived protein, termed FhHDM-1 (Fasciola hepatica helminth defense molecule 1), which efficiently stimulates the PI3K/Akt pathway in β-cells to enhance function and prevent death without concomitantly inducing proliferation unlike several other identified stimulators of PI3K/Akt signaling . As such, FhHDM-1 will inform the design of biologics aimed at targeting the PI3K/Akt pathway to prevent/ameliorate not only T1D but also T2D, which is now widely recognized as an inflammatory disease characterized by β-cell dysfunction and death. This review will explore the modulation of the PI3K/Akt signaling pathway as a novel strategy to enhance β-cell function and survival.

The parasite-derived peptide FhHDM-1 activates the PI3K/Akt pathway to prevent cytokine-induced apoptosis of β-cells

Type 1 diabetes (T1D) is an autoimmune disease characterised by the destruction of the insulin-producing beta (β)-cells within the pancreatic islets. We have previously identified a novel parasite-derived molecule, termed Fasciola hepatica helminth defence molecule 1 (FhHDM-1), that prevents T1D development in non-obese diabetic (NOD) mice. In this study, proteomic analyses of pancreas tissue from NOD mice suggested that FhHDM-1 activated the PI3K/Akt signalling pathway, which is associated with β-cell metabolism, survival and proliferation. Consistent with this finding, FhHDM-1 preserved β-cell mass in NOD mice. Examination of the biodistribution of FhHDM-1 after intraperitoneal administration in NOD mice revealed that the parasite peptide localised to the pancreas, suggesting that it exerted a direct effect on the survival/function of β-cells. This was confirmed in vitro, as the interaction of FhHDM-1 with the NOD-derived β-cell line, NIT-1, resulted in increased levels of phosphorylated Akt, increased NADH and NADPH and reduced activity of the NAD-dependent DNA nick sensor, poly(ADP-ribose) polymerase (PARP-1). As a consequence, β-cell survival was enhanced and apoptosis was prevented in the presence of the pro-inflammatory cytokines that destroy β-cells during T1D pathogenesis. Similarly, FhHDM-1 protected primary human islets from cytokine-induced apoptosis. Importantly, while FhHDM-1 promoted β-cell survival, it did not induce proliferation. Collectively, these data indicate that FhHDM-1 has significant therapeutic applications to promote β-cell survival, which is required for T1D and T2D prevention and islet transplantation. KEY MESSAGES: FhHDM-1 preserves β-cell mass in NOD mice and prevents the development of T1D. FhHDM-1 enhances phosphorylation of Akt in mouse β-cell lines. FhHDM-1 increases levels of NADH/NADPH in mouse β-cell lines in vitro. FhHDM-1 prevents cytokine-induced cell death of mouse β-cell lines and primary human β-cells in vitro via activation of the PI3K/Akt pathway.

Infection with Hymenolepis diminuta Blocks Colitis and Hastens Recovery While Colitis Has Minimal Impact on Expulsion of the Cestode from the Mouse Host

Two experimental paradigms were adopted to explore host-helminth interactions involved in the regulation of colitis and to understand if colitis affects the outcome of helminth infection. First, male BALB/c mice infected with H. diminuta were challenged 4 days later with dinitrobenzene sulphonic acid (DNBS) and necropsied 3 days later. Second, mice were infected with H. diminuta 3 days after DNBS treatment and necropsied 11 or 14 days post-DNBS. Mice were assessed for colitic disease severity and infectivity with H. diminuta upon necropsy. Supporting the concept of helminth therapy, mice are protected from DNBS-colitis when infected with H. diminuta only 4 days previously, along with parallel increases in splenic production of Th2 cytokines. In the treatment regimen, H. diminuta infection produced a subtle, statistically significant, enhanced recovery from DNBS. Mice regained body weight quicker, had normalized colon lengths, and showed no overt signs of disease, in comparison to the DNBS-only mice, some of which displayed signs of mild disease at 14 days post-DNBS. Unexpectedly, colitis did not affect the hosts' anti-worm response. The impact of inflammatory disease on helminth infection is deserving of study in a variety of models as auto-inflammatory diseases emerge in world regions where parasitic helminths are endemic.

The fatty acid-binding protein (FABP) decreases the clinical signs and modulates immune responses in a mouse model of experimental autoimmune encephalomyelitis (EAE)

BACKGROUND

An increasing body of studies has shown that Fasciola hepatica can affect immune responses. This study explored whether the fatty acid-binding protein (FABP) of F. hepatica can modulate the immune system in a mouse model of experimental autoimmune encephalomyelitis (EAE).

METHODS

EAE-induced C57BL/6 mice were treated with vehicle, F. hepatica total extract (TE) or FABP. The clinical signs, body weights, and the expression of IFN-γ, T-bet, IL-4, GATA3, IL-17, RORγ, TGF-β, FOXP3, IL-10, TNF-α genes and proteins were determined in the isolated CD4⁺ splenocytes. Besides, the percentage of Treg cells and degree of demyelination were evaluated.

RESULTS

We found that TE and FABP treatments decreased the clinical scores, lymphocyte infiltration rate, and demyelinated plaques in EAE mice. The expressions of IL-4 and GATA3 were increased, whereas IL-17 and TNF-α were down-regulated. FABP did not affect the expression of IFN-γ, RORγ, IL-10, and TGF-β genes or proteins but reduced the expression of T-bet. TE administration did not affect the expression of IL-10 and the Tbet genes, and increased the expression levels of IFN-γ and FOXP3 in CD4⁺ lymphocytes. Both FABP and TE treatment did not affect the Treg cell percentage.

CONCLUSION

This study indicates that F. hepatica FABP and TE can suppress the inflammatory responses in EAE-induced mice and shift the immune system toward Th2 responses. However, FABP exerts stronger anti-inflammatory effects and seems to be more effective than TE for EAE treatment.

The Nerves to Conduct a Multiple Sclerosis Crime Investigation

Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative autoimmune disease characterized by the aberrant infiltration of immune cells into the central nervous system (CNS) and by the loss of myelin. Sclerotic lesions and various inhibitory factors hamper the remyelination processes within the CNS. MS patients typically experience gradual cognitive and physical disabilities as the disease progresses. The etiology of MS is still unclear and emerging evidence suggests that microbiome composition could play a much more significant role in disease pathogenesis than was initially thought. Initially believed to be isolated to the gut microenvironment, we now know that the microbiome plays a much broader role in various tissues and is essential in the development of the immune system. Here, we present some of the unexpected roles that the microbiome plays in MS and discuss approaches for the development of next-generation treatment strategies.

Trichinella spiralis Calreticulin S-Domain Binds to Human Complement C1q to Interfere With C1q-Mediated Immune Functions

Helminths develop strategies to escape host immune responses that facilitate their survival in the hostile host immune environment. Trichinella spiralis, a tissue-dwelling nematode, has developed a sophisticated strategy to escape complement attack. Our previous study demonstrated that T. spiralis secretes calreticulin (TsCRT) to inhibit host classical complement activation through binding to C1q; however, the C1q binding site in TsCRT and the specific mechanism involved with complement-related immune evasion remains unknown. Using molecular docking modeling and fragment expression, we determined that TsCRT-S, a 153-aa domain of TsCRT, is responsible for C1q binding. Recombinant TsCRT-S protein expressed in Escherichia coli had the same capacity to bind and inhibit human C1q-induced complement and neutrophil activation, as full-length TsCRT. TsCRT-S inhibited neutrophil reactive oxygen species and elastase release by binding to C1q and reduced neutrophil killing of newborn T. spiralis larvae. Binding of TsCRT-S to C1q also inhibited formation of neutrophil extracellular traps (NETs), which are involved in autoimmune pathologies and have yet to be therapeutically targeted. These findings provide evidence that the TsCRT-S fragment, rather than the full-length TsCRT, is a potential target for vaccine or therapeutic development for trichinellosis, as well as for complement-related autoimmune disease therapies.

Fasciola hepatica-derived molecules as potential immunomodulators

Through the years, helminths have co-existed with many species. This process has allowed parasites to live within them for long periods and, in some cases, to generate offspring. In particular, this ability has allowed Fasciola hepatica to survive the diverse immunological responses faced within its wide range of hosts. The vast repertoire of molecules that are constantly secreted in large quantities by the parasite, acts directly on several cells of the immune system affecting their antiparasitic capacities. Interestingly, these molecules can direct the host immune response to an anti-inflammatory and regulatory phenotype that assures the survival of the parasite with less harm to the host. Based on these observations, some of the products of F. hepatica, as well as those of other helminths, have been studied, either as a total extract, extracellular vesicles or as purified molecules, to establish and characterize their anti-inflammatory mechanisms. Until now, the results obtained encourage further research directed to discover new helminth-derived alternatives to replace current therapies, which can be useful for people suffering from inflammatory diseases like autoimmunity or allergy processes that affect their life quality. In this review, some of the most studied molecules derived from F. hepatica and their modulating capacities are discussed.

Fasciola hepatica-Derived Molecules as Regulators of the Host Immune Response

Helminths (worms) are one of the most successful organisms in nature given their ability to infect millions of humans and animals worldwide. Their success can be attributed to their ability to modulate the host immune response for their own benefit by releasing excretory-secretory (ES) products. Accordingly, ES products have been lauded as a potential source of immunomodulators/biotherapeutics for an array of inflammatory diseases. However, there is a significant lack of knowledge regarding the specific interactions between these products and cells of the immune response. Many different compounds have been identified within the helminth "secretome," including antioxidants, proteases, mucin-like peptides, as well as helminth defense molecules (HDMs), each with unique influences on the host inflammatory response. HDMs are a conserved group of proteins initially discovered in the secretome of the liver fluke, Fasciola hepatica. HDMs interact with cell membranes without cytotoxic effects and do not exert antimicrobial activity, suggesting that these peptides evolved specifically for immunomodulatory purposes. A peptide generated from the HDM sequence, termed FhHDM-1, has shown extensive anti-inflammatory abilities in clinically relevant models of diseases such as diabetes, multiple sclerosis, asthma, and acute lung injury, offering hope for the development of a new class of therapeutics. In this review, the current knowledge of host immunomodulation by a range of F. hepatica ES products, particularly FhHDM-1, will be discussed. Immune regulators, including HDMs, have been identified from other helminths and will also be outlined to broaden our understanding of the variety of effects these potent molecules exert on immune cells.

The Dual Role of Antimicrobial Peptides in Autoimmunity

Autoimmune diseases (AiDs) are characterized by the destruction of host tissues by the host immune system. The etiology of AiDs is complex, with the implication of multiple genetic defects and various environmental factors (pathogens, antibiotic use, pollutants, stress, and diet). The interaction between these two compartments results in the rupture of tolerance against self-antigens and the unwanted activation of the immune system. Thanks to animal models, the immunopathology of many AiDs is well described, with the implication of both the innate and adaptive immune systems. This progress toward the understanding of AiDs led to several therapies tested in patients. However, the results from these clinical trials have not been satisfactory, from reversing the course of AiDs to preventing them. The need for a cure has prompted many investigators to explore alternative aspects in the immunopathology of these diseases. Among these new aspects, the role of antimicrobial host defense peptides (AMPs) is growing. Indeed, beyond their antimicrobial activity, AMPs are potent immunomodulatory molecules and consequently are implicated in the development of numerous AiDs. Importantly, according to the disease considered, AMPs appear to play a dual role in autoimmunity with either anti- or pro-inflammatory abilities. Here, we aimed to summarize the current knowledge about the role of AMPs in the development of AiDs and attempt to provide some hypotheses explaining their dual role. Definitely, a complete understanding of this aspect is mandatory before the design of AMP-based therapies against AiDs.

Effectiveness of Helminth Therapy in the Prevention of Allograft Rejection: A Systematic Review of Allogeneic Transplantation

Background: The unique immunomodulatory capacity of helminth parasites has been investigated as a novel strategy in the prevention of allograft rejection after transplantation. This review was conducted to fully evaluate the specific effects of helminth therapy on allograft survival reported in published studies of animal models of allogeneic transplantation.

Method: Following PRISMA protocol guidelines, a literature search was conducted using PubMed, MEDLINE via OvidSP, along with additional manual searches of selected reference lists. Publications describing helminth intervention within allograft transplantation models were screened for relevance to eligibility criteria. Primary and secondary outcomes were extracted using standardized data collection tables. The SYRCLE risk of bias assessment tool was used for quality assessment. Due to heterogeneity of study designs, meta-analysis could not be performed; rather outcomes are presented as a narrative synthesis with concept mapping. This review was registered in PROSPERO with ID: CRD42018097175.

Results: The literature search generated 1,443 publications, which after screening for relevance to the eligibility criteria yielded 15 publications for qualitative analysis. All 15 publications reported improvement to allograft survival as a result of helminth therapy. This prolonged allograft survival was not significantly different when helminth-derived products were used compared to live infection. However, the extent of positive impact on allograft survival was noted to be dependent on study design factors, such as the chronicity of the live helminth infection, allograft type and the species/genus of helminth selected.

Conclusion: Both live and product-based helminth therapy have potential applications as novel immune regulators or adjuncts for the prevention of allograft rejection. However, there were differences in efficacy between different worms and preparations of worm-derived products. Therefore, further studies are required to determine the most appropriate worm for a specific allograft, to elucidate the optimal dose and route of administration, and to better understand the modulation of immune responses that can mediate tolerance.

Schistosoma mansoni immunomodulatory molecule Sm16/SPO-1/SmSLP is a member of the trematode-specific helminth defence molecules (HDMs)

BACKGROUND

Sm16, also known as SPO-1 and SmSLP, is a low molecular weight protein (~16kDa) secreted by the digenean trematode parasite Schistosoma mansoni, one of the main causative agents of human schistosomiasis. The molecule is secreted from the acetabular gland of the cercariae during skin invasion and is believed to perform an immune-suppressive function to protect the invading parasite from innate immune cell attack.

METHODOLOGY/PRINCIPAL FINDINGS

We show that Sm16 homologues of the Schistosomatoidea family are phylogenetically related to the helminth defence molecule (HDM) family of immunomodulatory peptides first described in Fasciola hepatica. Interrogation of 69 helminths genomes demonstrates that HDMs are exclusive to trematode species. Structural analyses of Sm16 shows that it consists predominantly of an amphipathic alpha-helix, much like other HDMs. In S. mansoni, Sm16 is highly expressed in the cercariae and eggs but not in adult worms, suggesting that the molecule is of importance not only during skin invasion but also in the pro-inflammatory response to eggs in the liver tissues. Recombinant Sm16 and a synthetic form, Sm16 (34-117), bind to macrophages and are internalised into the endosomal/lysosomal system. Sm16 (34-117) elicited a weak pro-inflammatory response in macrophages in vitro but also suppressed the production of bacterial lipopolysaccharide (LPS)-induced inflammatory cytokines. Evaluation of the transcriptome of human macrophages treated with a synthetic Sm16 (34-117) demonstrates that the peptide exerts significant immunomodulatory effects alone, as well as in the presence of LPS. Pathways most significantly influenced by Sm16 (34-117) were those involving transcription factors peroxisome proliferator-activated receptor (PPAR) and liver X receptors/retinoid X receptor (LXR/RXR) which are intricately involved in regulating the cellular metabolism of macrophages (fatty acid, cholesterol and glucose homeostasis) and are central to inflammatory responses.

CONCLUSIONS/SIGNIFICANCE

These results offer new insights into the structure and function of a well-known immunomodulatory molecule, Sm16, and places it within a wider family of trematode-specific small molecule HDM immune-modulators with immuno-biotherapeutic possibilities.

Extracellular Vesicles Derived From Trichinella spiralis Muscle Larvae Ameliorate TNBS-Induced Colitis in Mice

Helminths are masters at modulating the host immune response through a wide variety of versatile mechanisms. These complex strategies facilitate parasite survival in the host and can also be exploited to prevent chronic immune disorders by minimizing excessive inflammation. Extracellular vesicles (EVs) are small membrane-bound structures secreted by helminths which mediate immune evasion during parasite infection. The goal of this study was to investigate the immunoregulatory properties of Trichinella spiralis EVs (Ts-EVs) in a murine model of colitis. We found that Ts-EVs significantly ameliorated 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice. Ts-EVs alleviated intestinal epithelium barrier damage, markedly reduced pro-inflammatory cytokine secretion and neutrophil infiltration, and upregulated immunoregulatory cytokine expression in colon tissue. Ts-EVs also modulated the adaptive immune response by influencing T-cell composition. The numbers of Th1 and Th17 cells in MLNs, as well as the expression levels of Th1/Th17-associated cytokines and transcription factors in colon were reduced. In contrast, Th2 and Treg cells were increased after Ts-EVs treatment. Furthermore, sequencing of EV-derived microRNAs (miRNAs) indicated that an array of miRNAs was involved in the regulation of the host immune response, including inflammation. These findings expand our knowledge of host-parasite interactions, and may help design novel and effective strategies to prevent parasite infections or to treat inflammatory diseases like IBD. Further studies are needed to identify the specific cargo molecules carried by Ts-EVs and to clarify their roles during T. spiralis infection.

Anti-inflammatory and immune-regulatory cytokines in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by a failure of spontaneous resolution of inflammation. Although the pro-inflammatory cytokines and mediators that trigger RA have been the focus of intense investigations, the regulatory and anti-inflammatory cytokines responsible for the suppression and resolution of disease in a context-dependent manner have been less well characterized. However, knowledge of the pathways that control the suppression and resolution of inflammation in RA is clinically relevant and conceptually important for understanding the pathophysiology of the disease and for the development of treatments that enable long-term remission. Cytokine-mediated processes such as the activation of T helper 2 cells by IL-4 and IL-13, the resolution of inflammation by IL-9, IL-5-induced eosinophil expansion, IL-33-mediated macrophage polarization, the production of IL-10 by regulatory B cells and IL-27-mediated suppression of lymphoid follicle formation are all involved in governing the regulation and resolution of inflammation in RA. By better understanding these immune-regulatory signalling pathways, new therapeutic strategies for RA can be envisioned that aim to balance and resolve, rather than suppress, inflammation.

A critical analysis of helminth immunotherapy in multiple sclerosis

Helminthic worms are ancestral members of the intestinal ecosystem that have been largely eradicated from the general population in industrialized countries. Immunomodulatory mechanisms induced by some helminths mediate a “truce” between the mammalian host and the colonizing worm, thus allowing for long-term persistence in the absence of immune-mediated collateral tissue damage. This concept and the geographic discrepancy between global burdens of chronic inflammatory diseases and helminth infection have sparked interest in the potential of using helminthic worms as a therapeutic intervention to limit the progression of autoimmune diseases such as multiple sclerosis (MS). Here, we present and evaluate the evidence for this hypothesis in the pre-clinical animal model of MS, experimental autoimmune encephalitis, in helminth-infected MS patients and in clinical trials of administered helminth immunotherapy (HIT).

Therapeutic applicability of helminths in autoimmune diseases - literature overview

This paper presents an overview of published studies conducted on helminths – parasites of the human gastrointestinal tract. Making use of their ability for immunomodulation may lead to the introduction of effective therapies for autoimmune diseases. This paper presents chronologically attempts to treat autoimmune diseases not only of the gastrointestinal tract, but also of the nervous and endocrine systems, which have been undertaken for decades. The overview of analysed reports demonstrates that as medical knowledge on the cells and mediators participating actively in inflammatory processes accumulates, clinical trials focus on ever more specific areas concerning the pathomechanisms of autoimmune diseases. The outcomes of clinical trials conducted both on animals and humans give reasons to assume that the modification of the human intestinal microflora may be the key to fighting against these diseases.

Gut Microbiota-Stimulated Innate Lymphoid Cells Support β-Defensin 14 Expression in Pancreatic Endocrine Cells, Preventing Autoimmune Diabetes

The gut microbiota is essential for the normal function of the gut immune system, and microbiota alterations are associated with autoimmune disorders. However, how the gut microbiota prevents autoimmunity in distant organs remains poorly defined. Here we reveal that gut microbiota conditioned innate lymphoid cells (ILCs) induce the expression of mouse β-defensin 14 (mBD14) by pancreatic endocrine cells, preventing autoimmune diabetes in the non-obese diabetic (NOD) mice. MBD14 stimulates, via Toll-like receptor 2, interleukin-4 (IL-4)-secreting B cells that induce regulatory macrophages, which in turn induce protective regulatory T cells. The gut microbiota-derived molecules, aryl hydrocarbon receptor (AHR) ligands and butyrate, promote IL-22 secretion by pancreatic ILCs, which induce expression of mBD14 by endocrine cells. Dysbiotic microbiota and low-affinity AHR allele explain the defective pancreatic expression of mBD14 observed in NOD mice. Our study reveals a yet unidentified crosstalk between ILCs and endocrine cells in the pancreas that is essential for the prevention of autoimmune diabetes development.

Antigen-Specific Tolerization and Targeted Delivery as Therapeutic Strategies for Autoimmune Diseases

The prevalence of autoimmune disorders is increasing steadily and there is no permanent cure available. Immunomodulation through repeated exposure of antigens, known as antigen-specific immune tolerance or antigen-specific immunotherapy (ASI), is a promising approach to treat or prevent autoimmune disorders. Different optimization protocols (immunization routes, delivery systems, and approaches) are being developed to implement ASI against self-proteins. Including appropriate adjuvants, altered peptide ligand, and using multipeptides are approaches that can be used to specifically target autoimmunity. This review explores various ASI application methods, including different routes of antigen-specific sensitization, delivery systems, immunomodulators containing specific antigens, and other targeted approaches that have been successfully demonstrated to have therapeutic effects on autoimmune diseases.

Opisthorchis viverrini Proteome and Host-Parasite Interactions

The omics technologies have improved our understanding of the molecular events that underpin host-parasite interactions and the pathogenesis of parasitic diseases. In the last decade, proteomics and genomics in particular have been used to characterize the surface and secreted products of the carcinogenic liver fluke Opisthorchis viverrini and revealed important roles for proteins at the host-parasite interface to ensure that the flukes can migrate, feed and reproduce in a hostile environment. This review summarizes the advances made in this area, primarily focusing on discoveries enabled by the publication of the fluke secreted proteomes over the last decade. Protein families that will be covered include proteases, antioxidants, oncogenic proteins and the secretion of exosome-like extracellular vesicles. Roles of these proteins in host-parasite interactions and pathogenesis of fluke-induced hepatobiliary diseases, including cholangiocarcinogenesis, are discussed. Future directions for the application of this knowledge to control infection and disease will also be discussed.

Parasite-Derived Proteins for the Treatment of Allergies and Autoimmune Diseases

The morbidity associated with atopic diseases and immune dysregulation disorders such as asthma, food allergies, multiple sclerosis, atopic dermatitis, type 1 diabetes mellitus, and inflammatory bowel disease has been increasing all around the world over the past few decades. Although the roles of non-biological environmental factors and genetic factors in the etiopathology have been particularly emphasized, they do not fully explain the increase; for example, genetic factors in a population change very gradually. Epidemiological investigation has revealed that the increase also parallels a decrease in infectious diseases, especially parasitic infections. Thus, the reduced prevalence of parasitic infections may be another important reason for immune dysregulation. Parasites have co-evolved with the human immune system for a long time. Some parasite-derived immune-evasion molecules have been verified to reduce the incidence and harmfulness of atopic diseases in humans by modulating the immune response. More importantly, some parasite-derived products have been shown to inhibit the progression of inflammatory diseases and consequently alleviate their symptoms. Thus, parasites, and especially their products, may have potential applications in the treatment of autoimmune diseases. In this review, the potential of parasite-derived products and their analogs for use in the treatment of atopic diseases and immune dysregulation is summarized.

Novel Therapeutics for Multiple Sclerosis Designed by Parasitic Worms

The evolutionary response to endemic infections with parasitic worms (helminth) was the development of a distinct regulatory immune profile arising from the need to encapsulate the helminths while simultaneously repairing tissue damage. According to the old friend's hypothesis, the diminished exposure to these parasites in the developed world has resulted in a dysregulated immune response that contributes to the increased incidence of immune mediated diseases such as Multiple Sclerosis (MS). Indeed, the global distribution of MS shows an inverse correlation to the prevalence of helminth infection. On this basis, the possibility of treating MS with helminth infection has been explored in animal models and phase 1 and 2 human clinical trials. However, the possibility also exists that the individual immune modulatory molecules secreted by helminth parasites may offer a more defined therapeutic strategy.

Triggering immunological memory against the tapeworm Hymenolepis diminuta to protect against colitis

Infection with parasitic helminths can ameliorate the severity of concomitant inflammatory disease. To use the tapeworm, Hymenolepis diminuta, and to extend this concept by assessing whether triggering a memory response against the worm inhibits dinitrobenzene sulphonic acid (DNBS)-induced colitis in Balb/c mice. Initial studies revealed that oral infection with 1, 3 or 5 H. diminuta cysticercoids 8 days before intrarectal administration of DNBS (3 mg) resulted in less severe inflammation and that infected mice displayed an increased propensity for T helper-2 immunity. A 1 mg dose of a PBS-soluble extract of the worm (HdAg) delivered intraperitoneally concomitant with DNBS was anticolitic as determined by macroscopic and histological disease scores 72 hour post-DNBS. Mice infected 28 days previously had a memory response as determined by HdAg-evoked increases in interleukin (IL)-4 and IL-10 from in vitro stimulated splenocytes and serum anti-H. diminuta IgG. Moreover, mice infected with 5 H. diminuta 28 days previously were protected from DNBS-induced colitis by secondary infection or 100 μg HdAg (ip.) at the time of DNBS treatment. An additional approach to managing inflammatory disease could be infection with H. diminuta followed by eliciting antiworm recall responses.

Helminth Products Potently Modulate Experimental Autoimmune Encephalomyelitis by Downregulating Neuroinflammation and Promoting a Suppressive Microenvironment

A negative correlation between the geographical distribution of autoimmune diseases and helminth infections has been largely associated in the last few years with a possible role for such type of parasites in the regulation of inflammatory diseases, suggesting new pathways for drug development. However, few helminth-derived immunomodulators have been tested in experimental autoimmune encephalomyelitis (EAE), an animal model of the human disease multiple sclerosis (MS). The immunomodulatory activities of Taenia crassiceps excreted/secreted products (TcES) that may suppress EAE development were sought for. Interestingly, it was discovered that TcES was able to suppress EAE development with more potency than dexamethasone; moreover, TcES treatment was still effective even when inoculated at later stages after the onset of EAE. Importantly, the TcES treatment was able to induce a range of Th2-type cytokines, while suppressing Th1 and Th17 responses. Both the polyclonal and the antigen-specific proliferative responses of lymphocytes were also inhibited in EAE-ill mice receiving TcES in association with a potent recruitment of suppressor cell populations. Peritoneal inoculation of TcES was able to direct the normal inflammatory cell traffic to the site of injection, thus modulating CNS infiltration, which may work along with Th2 immune polarization and lymphocyte activation impairment to downregulate EAE development.