Paola Margutti

Echinococcus granulosus Antigen B Impairs Human Dendritic Cell Differentiation and Polarizes Immature Dendritic Cell Maturation towards a Th2 Cell Response

ABSTRACT Despite inducing a strong host cellular and humoral immune response, the helminth Echinococcus granulosus is a highly successful parasite that develops, progresses, and ultimately causes chronic disease. Although surgery remains the preferred therapeutic option, pharmacological research now envisages antihelminthic strategies. To understand the mechanisms that E. granulosus uses to escape host immunosurveillance and promote chronic infection, we investigated how two hydatid cyst components, purified antigen B (AgB) and sheep hydatid fluid (SHF), act on host dendritic cell (DC) differentiation from monocyte precursors and how they influence maturation of DC that have already differentiated. We evaluated the immunomodulatory potential of these antigens by performing immunochemical and cytofluorimetric analyses of monocyte-derived DCs from healthy human donors. During monocyte differentiation, AgB and SHF downmodulated CD1a expression and upregulated CD86 expression. Compared with immature DCs differentiated in medium alone (iDCs), AgB- and SHF-differentiated cells stimulated with lipopolysaccharide included a significantly lower percentage of CD83+ cells (P < 10−4) and had weaker costimulatory molecule expression. When stimulated with AgB and SHF, iDCs matured and primed lymphocytes towards the Th2 response typical of E. granulosus infection. SHF and particularly AgB reduced the production of interleukin-12p70 (IL-12p70) and tumor necrosis factor alpha in lipopolysaccharide-stimulated iDCs. Anti-IL-10 antibodies increased the levels of IL-12p70 secretion in AgB- and SHF-matured DCs. AgB and SHF induced interleukin-1 receptor-associated kinase phosphorylation and activated nuclear factor-κB, suggesting that Toll-like receptors could participate in E. granulosus-stimulated DC maturation. These results suggest that E. granulosus escapes host immunosurveillance in two ways: by interfering with monocyte differentiation and by modulating DC maturation.

Redox state, cell death and autoimmune diseases: a gender perspective.

Autoimmune disorders, redox balance and gender differences are closely connected. In fact, activation, proliferation and death of cells of different histotype, including blood and vascular cells, are under control of oxidative balance and are key players in autoimmune disease pathogenesis and progression. However, cells from male and female appear characterized by a huge series of differences in terms of reactive oxygen species production and oxidative stress susceptibility. In this review, we briefly summarize the possible implications of the redox state in the onset and progression of autoimmune diseases in a gender perspective.

An update on immunodiagnosis of cystic echinococcosis.

Immunological parameters are increasingly investigated as possible markers for the development of cystic echinococcosis. Among the newer immunologic tests for assessing the host-parasite relationship, assay of immunoglobulin isotypes with the use of distinct parasite antigens and detection of Th1/Th2 cytokine expression are an interesting new approach. The findings upon which we have constructed our immunological hypothesis of the host-parasite relationship are: (1) immunoglobulin isotype profiles differ in patients with distinct clinical outcomes of the disease; in particular, antigen B is the antigen of choice to detect specific IgG4, which is the immunoglobulin isotype most clearly associated with the progression of the disease; (2) the isolation and characterisation of recombinant parasite proteins that behave as molecular markers of allergic reactions associated with cystic echinococcosis; (3) Th1/Th2 cell activation is involved in the clinical outcome of Echinococcus granulosus infection and, in particular Th2 response, is associated with susceptibility to the disease, whereas a Th1 response is associated with protective immunity.

Echinococcus granulosus‐specific T‐cell lines derived from patients at various clinical stages of cystic echinococcosis

To investigate the role of T lymphocytes in the immune response to Echinococcus granulosus, using sheep hydatid fluid (SHF) and antigen B (AgB), we generated T‐cell lines from patients with active, transitional and inactive hydatid cysts. We established 16 T‐cell lines, eight specific to SHF and eight specific to AgB. At surface phenotyping 88–98% of cells displayed the helper/inducer CD4 antigen. In all patients, at all clinical stages of hydatid cyst disease, T‐cell stimulation with SHF and AgB invariably amplified a large number of almost identical Vβ subfamily fragments. Irrespective of antigen‐specificity, the two cell lines from the patient with an inactive cyst had a Th1 profile, because they exclusively expressed and produced IFN‐γ. Conversely, the T‐cell lines derived from the seven patients with active and transitional hydatid cysts had mixed Th1/Th2 and Th0 clones. The functional characteristics of the 16 T‐cell lines differed markedly in the various clinical stages of cystic echinococcosis, thus providing new in vitro evidence that Th1 lymphocytes contribute decisively to the inactive stage of hydatid disease, Th2 lymphocytes in the active and transitional stages. The parasite‐specific T‐cell lines, especially the two Th1 lines from the patient with an inactive cyst, may help identify Th1 protective epitopes on SHF and AgB.

Autoantibodies involved in neuropsychiatric manifestations associated with Systemic Lupus Erythematosus

In the course of Systemic Lupus Erythematosus (SLE), a variety of neuropsychiatric disturbances is reported with a prevalence ranging from 17% to 75%. The diagnosis of these syndromes is difficult and requires a careful psychiatric evaluation. Distinct autoantibodies detectable in serum or cerebrospinal fluid of patients with SLE are associated with the presence of neuropsychiatric disorders. These autoantibodies may have a pathogenic relevance in neuropsychiatric SLE or they may be merely an epiphenomenon. This review describes the various autoantibodies reported to be associated with neuropsychiatric manifestations in SLE and discusses their possible role.

Immunomodulatory mechanisms during Echinococcus granulosus infection

The pathologic events that ensue after humans ingest the eggs of Echinococcus granulosus and continue while cystic echinococcosis develops, provide an excellent example illustrating the evasive strategies helminth parasites use to develop, progress and cause chronic disease. The hydatid cyst secretes and exposes numerous immunomodulatory molecules to the hosts immune system. By characterizing these molecules we can understand the mechanisms that E. granulosus uses for increasing the efficiency and persistency of infection in the host. These molecules modulate both the innate and adaptive arms of the immune response and appear to target cellular and humoral responses. In this review, we discuss recent advances in the immunobiology of host-E. granulosus interactions that provide intriguing insights into the complex interplay between host and parasite that ultimately facilitates parasite survival.

Mutations in dihydropteroate synthase gene of Pneumocystis carinii in HIV patients with Pneumocystis carinii pneumonia

The purpose of this study was to determine whether dihydropteroate synthase gene (DHPS) mutations were associated with the failure of sulpha/sulphone drugs used as prophylaxis agents in HIV infected patients. Results suggested that DHPS mutations were significantly associated with failure of anti-Pneumocystis carinii sulphone prophylaxis (P=0.031). An increasing number of mutant P. carinii strains have been isolated from patients no longer having prophylaxis. There was no statistically significant difference in severity or outcome of the pneumonia caused by wild-type or mutant DHPS. Moreover, two of the three patients with mutant P. carinii pneumonia (PCP) were successfully treated with sulpha drugs. We think that P. carinii drug-resistance could be an emerging problem for immunocompromised patients including those with HIV infection.

Identification and Relevance of the CD95-binding Domain in the N-terminal Region of Ezrin

The CD95 (Fas/APO-1) linkage to the actin cytoskeleton through ezrin is an essential requirement for susceptibility to the CD95-mediated apoptosis in CD4+ T cells. We have previously shown that moesin was not involved in the binding to CD95. Here we further support the specificity of the ezrin/CD95 binding, showing that radixin did not bind CD95. The ezrin region specifically and directly involved in the binding to CD95 was located in the middle lobe of the ezrin FERM domain, between amino acids 149 and 168. In this region, ezrin, radixin, and moesin show 60–65% identity, as compared with the 86% identity in the whole FERM domain. Transfection of two different human cell lines with a green fluorescent protein-tagged ezrin mutated in the CD95-binding epitope, induced a marked inhibition of CD95-mediated apoptosis. In these cells, the mutated ezrin did not co-localize or co-immunoprecipitate with CD95. Further analysis showed that the mutated ezrin, while unable to bind CD95, was fully able to bind actin, thus preventing the actin linkage to CD95. Altogether, our results support the specificity of ezrin in the association to CD95 and the importance of the ezrin-to-CD95 linkage in CD95-mediated apoptosis. Moreover, this study suggests that a major role of ezrin is to connect CD95 to actin, thus allowing the CD95 polarization on the cells and the occurrence of the following multiple cascades of the CD95 pathway.

Molecular cross-talk in host-parasite relationships: the intriguing immunomodulatory role of Echinococcus antigen B in cystic echinococcosis.

Cystic echinococcosis (CE), a zoonosis caused by the development of Echinococcus granulosus tapeworm larvae in the internal organs of ungulates and humans, continues to pose a major public health burden in underdeveloped and industrialised areas worldwide. Research designed to improve parasitic disease control and find out more about parasite biology has already identified a number of E. granulosus antigenic molecules. The major E. granulosus immunomodulant antigen isolated from hydatid fluid is antigen B, a 120 kDa polymeric lipoprotein consisting of various 8 kDa subunits. By inhibiting elastase activity and neutrophil chemotaxis and eliciting a non-protective Th2 cell response, antigen B helps the parasite evade the human response. In this review, we briefly discuss current information on the molecular characteristics and immunomodulatory properties of E. granulosus antigen B. Besides focusing on findings that provide intriguing insights into the complex interplay between host and parasite, we suggest how this information could extend the current therapeutic options in inflammatory diseases.

Molecular and immunological characterization of the C-terminal region of a new Echinococcus granulosus Heat Shock Protein 70

By screening an expression library of Echinococcus granulosus with IgE from sera of patients with cystic echinococcosis (CE) and allergic reactions, we isolated the C‐terminal region of a new heat shock protein (HSP)70 of E. granulosus. The protein, named Eg2HSP70, has close homology with the C‐terminal region of Dermatophagoides farinae and human HSP70. We investigated the humoral and cell‐mediated immune responses to this antigen in patients with CE grouped according to the presence of allergic reactions. Immunoblotting detected total IgG, IgG4 and IgE specific to Eg2HSP70 (83% of sera contained IgG, 31% IgG4 and 57% IgE). No significant difference was found in immunoglobulin percentages according to the presence of allergic reactions. Immunoblotting inhibition showed that no IgG or IgE specific to Eg2HSP70 cross‐reacted with D. farinae or human HSP70. Eg2HSP70‐stimulated PBMC from 26 patients produced significantly greater amounts of TNF‐α, IFN‐γ, and IL‐10 than unstimulated cultures in all patients, irrespective of the presence of allergic reactions (P < 0·05). They also produced significantly greater amounts of IL‐4 than unstimulated cultures exclusively in patients with allergic reactions (P < 0·05). These findings show that Eg2HSP70 is a new antigenic molecule inducing both B and T cell responses.