The implantation of Taenia solium metacestodes in mice induces down-modulation of T-cell proliferation and cytokine production

Regulatory T Cells as an Escape Mechanism to the Immune Response in Taenia crassiceps Infection

Murine cysticercosis by Taenia crassiceps is a model for human neurocysticercosis. Genetic and/or immune differences may underlie the higher susceptibility to infection in BALB/cAnN with respect to C57BL/6 mice. T regulatory cells (Tregs) could mediate the escape of T. crassiceps from the host immunity. This study is aimed to investigate the role of Tregs in T. crassiceps establishment in susceptible and non-susceptible mouse strains. Treg and effector cells were quantified in lymphoid organs before infection and 5, 30, 90, and 130 days post-infection. The proliferative response post-infection was characterized in vitro. The expression of regulatory and inflammatory molecules was assessed on days 5 and 30 post-infection. Depletion assays were performed to assess Treg functionality. Significantly higher Treg percentages were observed in BALB/cAnN mice, while increased percentages of activated CD127+ cells were found in C57BL/6 mice. The proliferative response was suppressed in susceptible mice, and Treg proliferation occurred only in susceptible mice. Treg-mediated suppression mechanisms may include IL-10 and TGFβ secretion, granzyme- and perforin-mediated cytolysis, metabolic disruption, and cell-to-cell contact. Tregs are functional in BALB/cAnN mice. Therefore Tregs could be allowing parasite establishment and survival in susceptible mice but could play a homeostatic role in non-susceptible strains.

Apoptosis of mouse hippocampal cells induced by Taenia crassiceps metacestode factor

Seizures, headache, depression and neurological deficits are the signs and symptoms most frequently reported in human neurocysticercosis. However, the cause of the associated learning and memory deficits is unknown. Here, we used Taenia crassiceps infection in mice as a model of human cysticercosis. The effects of T. crassiceps metacestode infection or T. crassiceps metacestode factor (MF) treatment on mouse hippocampal cells were studied; control mice were included. At 45 days after infection or treatment of the mice with MF, all mice were anaesthetized and perfused transcardially with saline followed by phosphate-buffered 10% formalin. Then the brains were carefully removed. Coronal sections stained using several techniques were analysed. Extensive and significant apoptosis was found in the experimental animals, mainly in the dentate gyrus, CA1, CA2, CA3 and neighbouring regions, in comparison with the apparently intact cells from control mice (P < 0.01). These results suggest that neurological deficits, especially the learning and memory deficits, may be generated by extensive apoptosis of hippocampal cells.

TP-58, a novel thienopyridine derivative, protects mice from concanavalinA-induced hepatitis by suppressing inflammation

Hepatitis represents a ubiquitous human health problem but effective therapies with limited side effects are still lacking. In this study, we investigated the effect and mechanism of TP-58, a novel thienopyridine derivative, on a murine fulminant hepatitis model induced by concanavalin A (ConA). We found TP-58 markedly alleviated ConA-caused liver injury and increased survival ratio of mice injected with a lethal dose of ConA. Oral administration of TP-58 significantly alleviated ConA-caused liver injury in mice by the reduction of serum aminotransferases and liver necrosis.The analysis of proinflammatory cytokines showed that TP-58 decreased both hepatic mRNA expressions and serum protein levels of TNF-α and IL-6. And the result from LPS-stimulated RAW 264.7 cells showed TP-58 suppressed the production of TNF-α, IL-6, and Nitro Oxide (NO) in the supernatant of LPS-stimulated RAW 264.7 cells. The study of activation of nuclear factor-κB (NF-κB) by electrophoretic mobility shift assay (EMSA) showed that TP-58 inhibited the activation of NF-κB both in vivo and in vitro. The inhibitory effect was also accompanied by a parallel reduction of IκB phosphorylation. These results indicate that TP-58 protects against liver injury by inhibition of the NF-κB-mediated inflammation and suggest a potential role of TP-58 against acute liver injury and other inflammatory diseases.

Mechanisms regulating monocyte CXCL8 secretion in neurocysticercosis and the effect of antiparasitic therapy

Neurocysticercosis (NCC) due to infection with Taenia solium is a major cause of epilepsy worldwide. Larval degeneration, which may follow antiparasitic treatment, results in clinical symptoms due to inflammatory cell influx. Mechanisms regulating this are not well understood, but chemokines have a key role. Stimulation of human monocytes by cyst Ags from NCC-infected pigs showed that scolex and membrane Ags drive CXCL8 and CCL2 secretion. Antiparasitic treatment of pigs increased CXCL8 in response to brain, but not muscle, cyst Ags. Cyst-fluid Ags did not elicit monocyte chemokine secretion, inhibited LPS-induced CXCL8 by up to 89%, but did not alter CCL2 secretion. This effect was inhibited by anti-IL-10 Abs. Plasma CXCL8, TNF-α, IL-10, eotaxin, IL-1, IL-1ra, soluble IL-1R-II, and soluble TNFR-I and -II levels were evaluated in 167 NCC patients. Patients had lower plasma CXCL8 and TNF-α concentrations than control subjects. In summary, larval Ags from brain and muscle cysts differentially regulate chemokine secretion. Cyst-fluid inhibits CXCL8, and this is blocked by anti-IL-10 Abs. CXCL8 concentrations are decreased in patient plasma. Following anti-parasitic therapy, scolex and membrane Ags are exposed, and cyst fluid is decreased, leading to inflammatory cell influx. Taken together, the cellular, porcine, and human data may explain, in part, why NCC is usually asymptomatic but may cause proinflammatory symptoms, particularly following treatment.

Mesocestoides corti intracranial infection as a murine model for neurocysticercosis

Neurocysticercosis (NCC) is the most common parasitic disease of the central nervous system (CNS) caused by the larval form of the tapeworm Taenia solium. NCC has a long asymptomatic period with little or no inflammation, and the sequential progression to symptomatic NCC depends upon the intense inflammation associated with degeneration of larvae. The mechanisms involved in these progressive events are difficult to study in human patients. Thus it was necessary to develop an experimental model that replicated NCC. In this review, we describe studies of a murine model of NCC in terms of the release/secretion of parasite antigens, immune responses elicited within the CNS environment and subsequent pathogenesis. In particular, the kinetics of leukocyte subsets infiltrating into the brain are discussed in the context of disruption of the CNS barriers at distinct anatomical sites and the mechanisms contributing to these processes. In addition, production of various inflammatory mediators and the mechanisms involved in their induction by the Toll-like receptor signaling pathway are described. Overall, the knowledge gained from the mouse model of NCC has provided new insights for understanding the kinetics of events contributing to different stages of NCC and should aid in the formulation of more effective therapeutic approaches.

Role of the programmed Death-1 pathway in the suppressive activity of alternatively activated macrophages in experimental cysticercosis

We characterised a population of macrophages potentially involved in the immunoregulation induced by experimental cysticercosis. Following Taenia crassiceps infection, macrophages recruited in the peritoneal cavity were isolated and co-cultured at different ratios with T cells from naïve mice previously stimulated with anti-CD3/CD28 antibodies; these macrophages inhibited naïve T cell proliferation. This suppressive effect was Interleukin (IL)-10, Interferon-gamma (IFN-gamma), and nitric oxide (NO) independent. In contrast, macrophage-T cell contact was necessary to maintain anergy of T cells. Reverse transcriptase-PCR analysis of these macrophages showed higher transcripts of IL-10, chitinases Fizz1 and Ym1, and arginase-1 compared with naïve macrophages; by contrast, IL-12p40, and inducible nitric oxide synthase (iNOS) transcripts were undetected, whereas C-C chemokine ligand 5 (CCL5) was unchanged. Analysis of the membrane molecules expressed on Taenia-induced macrophages showed an up-regulation of several markers, mainly programmed death ligand 1 (PD-L1) and PD-L2. Blockade of PD-L1, PD-L2 or their receptor PD-1, but not of another marker, eliminated their ability to inhibit T-cell proliferation. Parallel experiments using ovalbumin (OVA)-peptide as a model antigen displayed similar results. Additionally, the same mechanism appears to be functional in splenocytes of T. crassiceps-infected mice given that blockade of PD-1, PD-L1 or PD-L2 re-established their ability to proliferate in response to parasite antigens. Moreover, Taenia-induced macrophages were able to suppress a mixed lymphocyte reaction in a PD-1-dependent manner. Thus, cestode infections induce macrophages alternatively activated with strong suppressive activity involving the PD-1/PD-L's pathway.