Evaluation of Th1/Th2, regulatory cytokines and transcriptional factor FoxP3 in sheep immunized with a partially protective and non-protective vaccine and challenged with Fasciola hepatica

Gene expression for Th1/Th2 cytokines (IL-4 and IFN-ɣ), regulatory cytokines (TGF-β and IL-10) and the transcriptional factor FoxP3 was analyzed in the liver and hepatic lymph nodes (HLN) from sheep immunized with partially protective and non-protective vaccine candidates and challenged with Fasciola hepatica. FoxP3 T cells were also evaluated by immunohistochemistry (IHQ). The most remarkable difference between the partially protected vaccinated (V1) group and the non-protected vaccinated (V2) group was a more severe expansion of FoxP3 T cells recorded by IHQ in both the liver and HLN of the V2 group as compared to the V1 group, whereas no differences were found between the V2 group and the infected control (IC) group. Similar results were recorded for FoxP3 gene expression although significant differences among V1 and V2 groups were only significant in the HLN, while FoxP3 gene expression was very similar in the V2 and IC groups both in the liver and HLN. No significant differences for the remaining cytokines were recorded between the V1 and V2 groups, but in the liver the V2 group shows significant increases of IFN-ɣ and IL-10 as compared to the uninfected control (UC) group whereas the V1 group did not. The lower expansion of FoxP3 T cells and lower increase of IFN-ɣ and IL-10 in the partially protected vaccinated group may be related with lower hepatic lesions and fluke burdens recorded in this group as compared to the other two infected groups. The most relevant change in regulatory cytokine gene expression was the significant increase of TGF-β in the liver of IC, V1 and V2 groups as compared to the UC group, which could be related to hepatic lesions.

Serosurveillance of Trichinella sp. in wild boar and Iberian domestic suids in Mediterranean ecosystems of southwestern Spain

AIMS

A cross-sectional study was carried out to assess the seroprevalence and risk factors associated with Trichinella spp. exposure in wild boar and Iberian domestic pigs from Mediterranean ecosystems of southwestern Spain.

METHODS AND RESULTS

Serum samples from 1360 wild boar and 439 Iberian domestic pigs were obtained during 2015-2020, from regions where Iberian pigs are raised under extensive conditions, hence sharing habitat with wild boar. Seropositivity was found in 7.4% (100/1360; 95% CI: 6.1-8.9) of the wild boar analysed. In this species, the individual seroprevalence ranged from 3.6% (8/223) (hunting season 2016-2017) to 11.4% (37/326) (2018-2019). A significant higher seropositivity was observed during the hunting season 2018-2019 (p < 0.009: OR = 3.07; 95% CI = 1.32-7.18) and one statistically significant cluster was detected within the studied area, in south central Andalusia [Relative Risk (RR) = 2.9; p = 0.037]. Females showed a significantly higher seroprevalence than males (8.7% vs. 5.8%) (p < 0.001: OR = 1.58; 95% CI = 1.08-2.32). No seropositivity to Trichinella spp. was detected in Iberian domestic pigs (0.0%; 95% CI: 0.0-0.9).

CONCLUSIONS

Although wild boar play an important role as a reservoir of Trichinella sp. in the Mediterranean ecosystems of southwestern Spain, our results suggest that the wild boar production system does not seem to pose a risk of Trichinella exposure to domestic pigs, despite sharing habitats in these ecosystems.

Fasciolosis: pathogenesis, host-parasite interactions, and implication in vaccine development

Fasciola hepatica is distributed worldwide, causing substantial economic losses in the animal husbandry industry. Human fasciolosis is an emerging zoonosis in Andean America, Asia, and Africa. The control of the disease, both in humans and animals, is based on using anthelmintic drugs, which has resulted in increased resistance to the most effective anthelmintics, such as triclabendazole, in many countries. This, together with the concerns about drug residues in food and the environment, has increased the interest in preventive measures such as a vaccine to help control the disease in endemic areas. Despite important efforts over the past two decades and the work carried out with numerous vaccine candidates, none of them has demonstrated consistent and reproducible protection in target species. This is at least in part due to the high immunomodulation capacity of the parasite, making ineffective the host response in susceptible species such as ruminants. It is widely accepted that a deeper knowledge of the host-parasite interactions is needed for a more rational design of vaccine candidates. In recent years, the use of emerging technologies has notably increased the amount of data about these interactions. In the present study, current knowledge of host-parasite interactions and their implication in Fasciola hepatica vaccine development is reviewed.

Determination of atmospheric aerosol components in an urban area to evaluate the air quality and identify the sources of contamination

The need to generate objective evidence and reliable information for decision makers to improve environmental policies for a better air quality, led us to evaluate the atmospheric aerosol components in the urban area of Carabayllo, by monitoring PM2.5 and PM10 to determine mass concentration and analyzing PM10 using k 0-INAA and ICP-MS for metals quantification, ion chromatography for anions and the NIOSH method to determine organic and elemental carbon. The results obtained from mass concentration of PM2.5 and PM10 exceeded the permissible breathing annual average of WHO guidelines of 15 µgm-3 and 45 µgm-3, respectively, which evidence an unhealthy air quality. Likewise, using the model Positive Matrix Factorization five sources of pollutants were defined: metallurgical industry, sea salt, industrial activity, dust and non-exhaust emissions and vehicle emissions.

Fasciola hepatica primoinfections and reinfections in sheep drive distinct Th1/Th2/Treg immune responses in liver and hepatic lymph node at early and late stages

The expression of proinflammatory (IL-1β, IFN-γ, TNF-α) and regulatory (IL-10, TGF-β, IL-4) cytokines, as well as the transcription factor FoxP3, was quantified in the liver and hepatic lymph node (HLN) of sheep primoinfected and reinfected with Fasciola hepatica at early (4, 8 and 16 days post-infection [dpi]) and late (100 dpi) stages. The liver exerted a Th2 immune response at very early stages after the primoinfection with F. hepatica that induced the downregulation of IFN-γ, followed by a Th1/Th2/Treg response although the late stages were characterised by the expression of Th1/Th2 immune mediators. Contrarily, in reinfected sheep a robust mixed Th1/Th2/Treg immune response was found at very early stages meanwhile at late stages we observed a Th2/Treg immune response overcoming the expression of Th1 immune mediators. However, the HLN displayed a completely different Th1/Th2/Treg expression profile compared to the liver. Primoinfections with F. hepatica in HLN induced a mixed Th1/Th2/Treg environment from early stages, establishing a Th2 immune response at a late stage. However, the reinfected sheep exerted a Th2 immune response at early stages led by the IL-4 expression in opposition to the Th1/Th2/Treg found in the liver, meanwhile at late stages the HLN of reinfected sheep exerted a mixed Th1/Th2/Treg immune response. This is the first work publishing the expression of immune mediators in the liver and HLN from reinfected sheep with F. hepatica. The study of the immune responses exerted by the natural host in the target organs directly implied in the development of F. hepatica are crucial to better understand the immunopathogenesis of the fasciolosis being a key factor to develop effective vaccines.

A Partially Protective Vaccine for Fasciola hepatica Induced Degeneration of Adult Flukes Associated to a Severe Granulomatous Reaction in Sheep

Simple Summary

Fasciolosis is a parasitic disease of livestock causing important economic losses worldwide and it is also a zoonosis. Current therapy relies on the use of anthelmintic drugs, which is no longer sustainable due to the increase of anthelmintic resistance and the risk of drug residues in food. A deep understanding of the host-parasite interaction is required to develop protective vaccines for the control of fasciolosis. The aim of the present study is to evaluate the hepatic lesions in sheep vaccinated with a partly protective vaccine for F. hepatica, a non-protective vaccine and an infected control group. The protective vaccine showed less severe hepatic lesions than the infected control group. In addition, in the protective vaccine group dead flukes surrounded by a severe granulomatous inflammation were observed, which taken together with the lower fluke burden, suggests that the host response induced by the partially protective vaccine may have been involved in the death of adult flukes of F. hepatica. This is the first study reporting the presence of degenerated flukes associated to a severe granulomatous inflammation in bile ducts in a vaccine trial, a finding that would be useful for improving vaccine efficacy in future trials.

Abstract

Fasciolosis is an important economic disease of livestock. There is a global interest in the development of protective vaccines since current anthelmintic therapy is no longer sustainable. A better knowledge of the host-parasite interaction is needed for the design of effective vaccines. The present study evaluates the microscopical hepatic lesions in sheep immunized with a partially protective vaccine (VAC1), a non-protective vaccine (VAC2), and an infected control group (IC). The nature of granulomatous inflammation associated with degeneration of adult flukes found in the VAC1 group was characterized by immunohistochemistry. Hepatic lesions (fibrous perihepatitis, chronic tracts, bile duct hyperplasia, infiltration of eosinophils and lymphocytes and plasma cells) were significantly less severe in the VAC1 group than in the IC group. Dead adult flukes within bile ducts were observed only in the VAC1 group and were surrounded by a severe granulomatous inflammation composed by macrophages and multinucleate giant cells with a high expression of lysozyme, CD163 and S100 markers, and a low expression of CD68. Numerous CD3+ T lymphocytes and scarce infiltrate of FoxP3+ Treg and CD208+ dendritic cells were present. This is the first report describing degenerated flukes associated to a severe granulomatous inflammation in bile ducts in a F. hepatica vaccine trial.

Antigen-specific response of CD4+ T cells and hepatic lymph node cells to Fasciola hepatica-derived molecules at the early and late stage of the infection in sheep

The immunomodulatory capacity of F. hepatica antigens is probably one of the main reasons for the development of a driven non-protective Th2 immune response. In this study, we analysed the cellular response of hepatic lymph node cells and CD4⁺ T cells in terms of proliferative response, efficiency of antigen presentation and cytokine production, to F. hepatica-derived molecules, at early and late stages of the infection. Thirty-one sheep were allocated into five groups and were slaughtered at 16 dpi and 23 wpi. In order to analyse antigen-specific response, the following F. hepatica recombinant molecules were used: rFhCL1, rFhCL2, rFhCL3, rFhCB1, rFhCB2, rFhCB3, rFhStf-1, rFhStf-2, rFhStf-3 and rFhKT1. A cell proliferation assay using hepatic lymph node cells and an antigen presentation cell assay using CD4⁺ T cells were performed. At 16 dpi, all molecules but rFhStf-2 and rFhKT1 elicited a significant cell proliferative response on hepatic lymph node cells of infected animals. At both early and late stage of the infection, antigen presentation of rFhCB3 and rFhCL2 resulted in higher stimulation index of CD4⁺ T cells which was IL-2 mediated, although no statistically significant when compared to uninfected animals. Significant cytokine production (IL-4, IL-10 and IFN-γ) was conditioned by the antigen-specific cell stimulation. No CD4⁺ T cell exhaustion was detected in infected sheep at the chronic stage of the infection. This study addressed antigen-specific response to F. hepatica-derived molecules that are involved in key aspects of the parasite survival within the host.

Efficacy of a multivalent vaccine against Fasciola hepatica infection in sheep

In this work we report the protection found in a vaccination trial performed in sheep with two different vaccines composed each one by a cocktail of antigens (rCL1, rPrx, rHDM and rLAP) formulated in two different adjuvants (Montanide ISA 61 VG (G1) and Alhydrogel®(G2)). The parameters of protection tested were fluke burden, faecal egg count and evaluation of hepatic lesions. In vaccinated group 1 we found a significant decrease in fluke burden in comparison to both unimmunised and infected control group (37.2%; p = 0.002) and to vaccinated group 2 (Alhydrogel®) (27.08%; p = 0.016). The lower fluke burden found in G1 was accompanied by a decrease in egg output of 28.71% in comparison with the infected control group. Additionally, gross hepatic lesions found in vaccine 1 group showed a significant decrease (p = 0.03) in comparison with unimmunised-infected group. The serological study showed the highest level for both IgG1 and IgG2 in animals from group 1. All these data support the hypothesis of protection found in vaccine 1 group.

Identification of protective peptides of Fasciola hepatica-derived cathepsin L1 (FhCL1) in vaccinated sheep by a linear B-cell epitope mapping approach

Background

Fasciolosis is one of the most important parasitic diseases of livestock. The need for better control strategies gave rise to the identification of various vaccine candidates. The recombinant form of a member of the cysteine protease family, cathepsin L1 of Fasciola hepatica (FhCL1) has been a vaccine target for the past few decades since it has been shown to behave as an immunodominant antigen. However, when FhCL1 was used as vaccine, it has been observed to elicit significant protection in some trials, whereas no protection was provided in others.

Methods

In order to improve vaccine development strategy, we conducted a linear B-cell epitope mapping of FhCL1 in sheep vaccinated with FhCL1, FhHDM, FhLAP and FhPrx plus Montanide and with significant reduction of the fluke burden, sheep vaccinated with FhCL1, FhHDM, FhLAP and FhPrx plus aluminium hydroxide and with non-significant reduction of the fluke burden, and in unvaccinated-infected sheep.

Results

Our study showed that the pattern and dynamic of peptide recognition varied noticeably between both vaccinated groups, and that the regions 55–63 and 77–84, which are within the propeptide, and regions 102–114 and 265–273 of FhCL1 were specifically recognised only by vaccinated sheep with significant reduction of the fluke burden. In addition, these animals also showed significant production of specific IgG2, whereas none was observed in vaccinated-Aluminium hydroxide and in infected control animals.

Conclusions

We have identified 42 residues of FhCL1 that contributed to protective immunity against infection with F. hepatica in sheep. Our results provide indications in relation to key aspects of the immune response. Given the variable outcomes of vaccination trials conducted in ruminants to date, this study adds new insights to improve strategies of vaccine development.

Characterization of dendritic cells and follicular dendritic cells in the hepatic lymph nodes and liver of sheep experimentally infected with Fasciola hepatica

Fasciola hepatica has been shown to have a high capacity for immunomodulation of the host response, making the development of protective vaccines extremely difficult. One of these immunomodulation mechanisms is the impairment of dendritic cells (DC) maturation and, therefore, suppression of antigenic presentation. The aim of this study was to evaluate the pathological changes as well as the characterization of two antigen presenting cells, DC (CD1b, CD83 and MHC-II positive) and follicular dendritic cells (FDC) (CNA.42, S100 and CD83 positive) by immunohistochemistry in the hepatic lymph nodes (HLN) and livers of sheep during the early stages of infection with F. hepatica [9 and 18 days post-infection (dpi)], compared with an uninfected group (UC) as a control. The results revealed a marked hyperplasia of HLN germinal centres at 9 and, in particular, 18 dpi, with respect to the UC group, with coincidental increased expression of CNA.42 in FDC of lymphoid follicles and CD1b in the DC of paracortical areas at 18 dpi. However, the expression of MHC-II and CD83 decreased at 9 and, particularly, at 18 dpi in HLN compared with that in the UC group. Since both markers are related to active presentation of antigens by DC and FDC, the results of the present study suggest that, despite the marked hyperplasia of HLN and increase in DC and FDC numbers during early stages of infection, the DC and FDC antigenic presentation capacity, as suggested by the expression of the markers MHC-II and CD83, is suppressed by the parasite. This suppression was not observed in the liver, probably because of the low number of DC. This is the first study of the immunophenotype of DCs and FDC in sheep infected with F. hepatica.

Identification of reference genes for real-time PCR cytokine gene expression studies in sheep experimentally infected with Fasciola hepatica

The aim of this study was to validate reference genes for gene normalisation using qRT-PCR in hepatic lymph nodes (HLN) and livers from sheep infected with Fasciola hepatica during early and late stages of infection. To this end, a comprehensive statistical approach (RefFinder) encompassing four different methods of analysis (geNorm, BestKeeper, ΔCt method and NormFinder) was used to validate ten candidate reference genes. Stability analysis of gene expression followed by pairwise variation (Vn/Vn + 1) analysis revealed that PGK1, HSP90AA1 and GYPC were the most stable reference genes and suitable for qRT-PCR normalisation in both HLN and liver tissues. These three genes were validated against FoxP3, IL-10, TGF-β, TNF-α and IL-1β genes in the HLN tissue of sheep vaccinated with Cathepsin L1 from F. hepatica and unvaccinated infected and uninfected controls during early stages of infection. In the liver, the three reference genes were validated against TNF-α and IL-1β during chronic stages of infection with F. hepatica and in uninfected controls. Our study is the first to evaluate and validate sheep reference genes in order to provide tools for monitoring cytokines in Fasciola hepatica infected sheep target organs. Our results present an approach to elucidate the role of different cytokines in F. hepatica vaccinated and infected sheep.

Comparative dynamics of peritoneal cell immunophenotypes in sheep during the early and late stages of the infection with Fasciola hepatica by flow cytometric analysis

Background

The peritoneal cell populations (PCP) are thought to play a crucial role during the early immune response in Fasciola hepatica infection while newly excysted juveniles (NEJ) are migrating in the peritoneal cavity (PC) towards the liver. In this study, we aimed to determine the immunophenotypes of the PCP and to analyse the dynamics of the recruitment of the PCP during the early and late stage of the infection in sheep infected with F. hepatica.

Methods

Thirty-seven sheep were divided into three groups: Group 1 (n = 20) and 2 (n = 10) were challenged with F. hepatica, Group 3 (n = 7) was not infected and remained as uninfected control (UC). After the slaughtering, peritoneal lavages were carried out to isolate peritoneal cell populations at 1, 3, 9 and 18 days post-infection (dpi) for Group 1 and at 14 weeks post-infection (wpi) for Group 2 and 3. Flow cytometry was conducted to assess the dynamics of peritoneal cavity cell populations.

Results

TCD4 cells showed a significant decrease at 1 and 18 dpi when compared to UC; no statistical differences were detected for TCD8 and WC1⁺γδ during the early stage of the infection with respect to the UC. CD14 cells exhibited a decreasing trend, with a significant decrease at 9 and 18 dpi when compared to the UC. The dynamics of MHCII and CD83 cells showed a similar increasing pattern from 3 to 18 dpi. During the chronic stage, both TCD4 and TCD8 cells showed no significant differences when compared to the UC, although a slight but statistically significant higher level of WC1⁺γδ cells was observed. A lower percentage of antigen-presenting cells (APCs) was detected with respect to the UC.

Conclusions

The recruitment of the lymphocytes subsets did not show a significant increase during the course of the infection and only WC1⁺γδ cells displayed a significant increase at the chronic stage. For the CD14, a decreasing trend was observed during the early stage, which was statistically significant at the chronic stage of the infection. Peritoneal CD83 and MHCII cells developed an increasing trend during the early stage of infection, and showed a significant decrease at the late stage of the infection.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3250-5) contains supplementary material, which is available to authorized users.

Expression of free radicals by peritoneal cells of sheep during the early stages of Fasciola hepatica infection

BACKGROUND

The majority of vaccination studies against infection with F. hepatica in a natural host have been conducted at the late stage of the infection when the host's immune response is already immunomodulated by the parasite towards a Th2 non-protective response. This study was aimed at analysing the dynamic of the cell populations present in peritoneal liquid and the production of free radicals by the peritoneal leukocytes in infected and vaccinated sheep with recombinant cathepsin L1 of F. hepatica (rFhCL1) in early stages of the infection.

METHODS

Forty-five sheep were divided into three groups: Group 1 remained as negative control (n = 5), Group 2 (n = 20) was challenged with F. hepatica and Group 3 (n = 20) was vaccinated with rFhCL1 and challenged with F. hepatica. After the slaughtering, peritoneal lavages were carried out at 1, 3, 9 and 18 days post-infection (dpi) to isolate peritoneal cell populations. Flow cytometry was conducted to assess levels of hydrogen peroxide (H₂O₂) and nitric oxide (NO).

RESULTS

There was a significant increase in the total number of leukocytes at 9 and 18 dpi in infected and vaccinated groups. Production of H₂O₂ was significantly increased in peritoneal granulocytes in both infected and vaccinated groups. Production of nitric oxide showed a significant rise in the granulocytes and monocytes/macrophages in infected and vaccinated sheep. The NO production by granulocytes at 3 and 9 dpi was significantly higher in the vaccinated than in the infected animals.

CONCLUSIONS

Experimental infection induced an increase in the total number of leukocytes within the abdominal cavity at 9 and 18 dpi, being more noticeable in vaccinated animals. Production of H₂O₂ occurred mainly in granulocytes of vaccinated and infected animals. Production of NO was incremented in vaccinated and non-vaccinated animals in all peritoneal cells. Vaccinated animals produced significant higher level of H₂O₂ and NO than infected animals.

Fasciola hepatica induces Foxp3 T cell, proinflammatory and regulatory cytokine overexpression in liver from infected sheep during early stages of infection

The expression of T regulatory cells (Foxp3), regulatory (interleukin [IL]-10 and transforming growth factor beta [TGF-β]) and proinflammatory (tumor necrosis factor alpha [TNF-α] and interleukin [IL]-1β) cytokines was quantified using real time polymerase chain reaction (qRT-PCR) in the liver of sheep during early stages of infection with Fasciola hepatica (1, 3, 9, and 18 days post-infection [dpi]). Portal fibrosis was also evaluated by Masson's trichrome stain as well as the number of Foxp3+ cells by immunohistochemistry. Animals were divided into three groups: (a) group 1 was immunized with recombinant cathepsin L1 from F. hepatica (FhCL1) in Montanide adjuvant and infected; (b) group 2 was uniquely infected with F. hepatica; and (c) group 3 was the control group, unimmunized and uninfected. An overexpression of regulatory cytokines of groups 1 and 2 was found in all time points tested in comparison with group 3, particularly at 18 dpi. A significant increase of the number of Foxp3+ lymphocytes in groups 1 and 2 was found at 9 and 18 dpi relative to group 3. A progressive increase in portal fibrosis was found in groups 1 and 2 in comparison with group 3. In this regard, group 1 showed smaller areas of fibrosis than group 2. There was a significant positive correlation between Foxp3 and IL-10 expression (by immunohistochemistry and qRT-PCR) just as between portal fibrosis and TGF-β gene expression. The expression of proinflammatory cytokines increased gradually during the experience. These findings suggest the induction of a regulatory phenotype by the parasite that would allow its survival at early stages of the disease when it is more vulnerable.

Study of peritoneal macrophage immunophenotype in sheep experimentally infected with Fasciola hepatica

During Fasciola hepatica infection, the parasite has the capability to modulate the host immune response towards a non-protector Th2 type instead of Th1. This type of immune response is closely related to the alternative activation of macrophages (M2 profile) as has been shown in vivo in murine models. In this study, an experiment was carried out in order to evaluate the expression of CD68, CD14, CD206 and iNOS in cells present in the peritoneal fluid of sheep during early stages of infection with F. hepatica (1, 3, 9 and 18 days post-infection, dpi) by immunocytochemistry. To the authors' knowledge, this is the first report that studies the in vivo immunophenotype of macrophages from the peritoneal fluid of sheep infected with F. hepatica. Throughout the experiments the absolute number of leucocytes progressively increased, reaching its highest value at 18 dpi, mainly due to the increase of eosinophils. This immunocytochemical study had two purposes: 1) CD68 expression was assessed with Hansel counterstaining, to optimally identify peritoneal macrophages, eosinophils and lymphocytes; 2) expression of CD14, CD206 and iNOS was evaluated to identify alternative or classical pathways of macrophage activation. The results showed a significant increase in CD14 from day 3 dpi compared with the non-infected group. CD206 expression at all time-points showed a significant and dramatic increase in comparison with the uninfected group. On the other hand, iNOS expression showed little variation, and was significantly decreased at 18 dpi in comparison with the uninfected group. These results suggest that F. hepatica induces an alternative activation of peritoneal macrophages of sheep from the first day post-infection, which may facilitate parasite survival. This is the first report describing M2 activation of peritoneal macrophages in ruminants infected with F. hepatica.

Th1/Th2 balance in the liver and hepatic lymph nodes of vaccinated and unvaccinated sheep during acute stages of infection with Fasciola hepatica

The expression of IFNγ and IL4 was quantified using q-PCR in the liver and hepatic lymph nodes (HLN) of sheep during early stages of infection with Fasciola hepatica (1, 3, 9 and 18days post-infection, dpi). A group of animals (Group 1) were vaccinated with Fasciola hepatica recombinant cathepsin L1 (FhCL1) in montanide 70 VG prior to infection, a second group (group 2) was used as infected control and a third (group 3) was used as uninfected control. To study vaccine efficacy three additional groups were sacrificed 19 weeks post-infection (group 4 immunized with CL1, group 5 with the adjuvant and group 6 was used as infected control). The vaccinated group did not show significant fluke reduction compared to the adjuvant group and infected control group. IL4 expression was observed to increase at 9 dpi and was further elevated at 18 dpi in the liver and HLN of vaccinated and infected control groups compared to the uninfected group. IFNγ expression exhibited different dynamics in the liver and HLN compared to IL4; thus, in the liver this cytokine increased at 9 dpi in the vaccinated and at 18 dpi in vaccinated and infected control groups, while in the HLN it decreased gradually and significantly from 1 dpi onwards. These results suggest that a marked Th2 polarization is present from 9 dpi in HLN and from 18 dpi in the liver. The increase of IFNγ in the liver may correspond with tissue damage response with granuloma formation. The FhCL1 vaccine did not alter the Th1/Th2 balance when compared to unvaccinated and infected sheep. The study of IFNγ and IL4 in the various tissue compartments in sheep could facilitate selection of new adjuvants inducing a strong Th1 response for a more rationale vaccine formulation.

Apoptosis of peritoneal leucocytes during early stages of Fasciola hepatica infections in sheep

Several immunomodulatory properties have been described in Fasciola hepatica infections. Apoptosis has been shown to be an effective mechanism to avoid the immune response in helminth infections. The aim of the present work was to study apoptosis in peritoneal leucocytes of sheep experimentally infected with F. hepatica during the early stages of infection. Five groups (n=5) of sheep were used. Groups 2-5 were orally infected with 200 metacercariae (mc) and sacrificed at 1, 3, 9 and 18days post-infection (dpi), respectively. Group 1 was used as the uninfected control (UC). Apoptosis was detected using three different methods 1) immunocytochemistry (ICC) with a polyclonal antibody anti-active caspase-3; 2) an annexin V flow cytometry assay using the Annexin V-FITC/propidium iodide (PI); and 3) transmission electron microscopy (TEM). The differential leucocyte count revealed that the majority of peritoneal granulocytes were eosinophils, which increased significantly at 9 and 18 dpi with respect to the uninfected controls. The ICC study revealed that the percentage of caspase-3⁺ apoptotic peritoneal leucocytes increased significantly from 3 dpi onwards with respect to the uninfected controls. The flow cytometry annexin V assay detected a very significant (P<0.001) increase of apoptotic peritoneal macrophages, lymphocytes and granulocytes, which remained higher than in the UC until 18 dpi. Transmission electron microscopy studies also confirmed the presence of apoptosis in peritoneal eosinophils at 18 dpi. This is the first report of apoptosis induced by F. hepatica in the peritoneal leucocytes of sheep in vivo. The results of this work suggest the importance of apoptosis induction for the survival of the juvenile parasites in the peritoneal migratory stages of infection.

Distribution of Foxp3+ T cells in the liver and hepatic lymph nodes of goats and sheep experimentally infected with Fasciola hepatica

Foxp3 regulatory T cells (Tregs) are now considered to play a key role in modulation of immune responses during parasitic helminth infections. Immunomodulation is a key factor in Fasciola hepatica infection; however, the distribution and role of Foxp3⁺ Tregs cells have not been investigated in F. hepatica infected ruminants. The aim of this study was to evaluate the presence of Foxp3⁺ Tregs in the liver and hepatic lymph nodes from experimentally infected sheep and goats during acute and chronic stages of infection. Three groups of goats (n=6) and three groups of sheep (n=6) were used in this study. Goats in groups 1-2 and sheep in groups 4-5 were orally infected with metacercarie of ovine origin. Groups 1 and 4 were killed during the acute stage of the infection, at nine days post infection (dpi); groups 2 and 5 were killed during the chronic stage, at 15 and19 weeks post infection respectively (wpi). Groups 3 (goats) and 6 (sheep) were left as uninfected controls. Fluke burdens and liver damage were assessed and the avidin-biotin-complex method was used for the immunohistochemical study. At nine dpi in acute hepatic lesions, the number of both Foxp3⁺ and CD3⁺ T lymphocytes increased significantly in goats and sheep. In the chronic stages of infection (15-19wpi), the number of Foxp3⁺ and CD3⁺ T lymphocytes were also significantly increased with respect to control livers, particularly in portal spaces with severely enlarged bile ducts (response to adult flukes) while the increase was lower in granulomas, chronic tracts and smaller portal spaces (response to tissue damage). Foxp3⁺ Tregs were increased in the cortex of hepatic lymph nodes of sheep (chronic infection) and goats (acute and chronic infection). The estimated proportion of T cells which were Foxp3+ was significantly increased in the large bile ducts and hepatic lymph node cortex of chronically infected goats but not sheep. This first report of the expansion of Foxp3⁺ Tregs in acute and chronic hepatic lesions in ruminants suggests that these cells may be involved in both parasite survival and modulation of hepatic damage. Future studies should be focused on the investigation of parasite molecules and cytokines involved in this process.

An Unusual Case of Generalized Soft-Tissue Mineralization in a Suckling Foal

An atypical case of severe soft-tissue mineralization in a 3-week-old foal from a herd of Andalusian horses is described. The herd clinical history and the laboratory findings were compatible with a diagnosis of secondary hyperparathyroidism due to a mineral imbalance in the diet (low calcium and high phosphorus intake). Mares showed a marked increase in serum parathyroid hormone (PTH) approximately 10 times normal levels. Serum PTH was marginally elevated in foals. Clinical signs (unthriftiness, painful joints, lameness in one or more limbs, and stiff gait) were more pronounced in foals than in mares. Two foals died and necropsy of one of them revealed extensive soft-tissue mineralization of arterial walls and pulmonary parenchyma. Clinical signs in mares and foals resolved by 4 weeks after diet adjustment.

Eosinophilic Enteritis in Horses with Motor Neuron Disease

BACKGROUND

Equine motor neuron disease (EMND) is a neuromuscular disorder that affects adult horses. Although EMND has been linked to vitamin E deficiency, its etiopathogenesis is poorly understood.

OBJECTIVES

To describe clinical features, laboratory results, and postmortem findings in a series of young horses with motor neuron disease (MND).

ANIMALS

A herd of 15 young Andalusian horses with weakness, weight loss, muscle atrophy, and muscle fasciculations related to restricted intake of green forage.

METHODS

A case series is presented in which horses were subjected to a clinical examination and plasma vitamin E measurement. Five severely affected horses were euthanized for detailed postmortem examination. Muscle specimens were taken from the M. sacrocaudalis dorsalis medialis and the M. gluteus medius for histopathologic and morphometric evaluation.

RESULTS

MND was diagnosed in 5 horses based on clinical signs, low serum levels of vitamin E (0.11 ± 0.05 mg/dL; normal range,: 0.3-1.5 mg/dL), changes in muscle histopathology (neurogenic atrophy), and spinal cord lesions (neuronal chromatolysis in ventral horns). An unexpected postmortem finding was the presence of intestinal inflammation (catarrhal enteritis, edema, and eosinophilic infiltrate) associated with the presence of giant ciliated protozoa in all of the horses.

CONCLUSIONS

Although a mechanistic link could not be established, it is hypothesized that intestinal inflammation may have been involved in the decreased absorption of vitamin E, thus favoring the development of MND.

Fasciola hepatica induces eosinophil apoptosis in the migratory and biliary stages of infection in sheep

The aim of the present work was to evaluate the number of apoptotic eosinophils in the livers of sheep experimentally infected with Fasciola hepatica during the migratory and biliary stages of infection. Four groups (n=5) of sheep were used; groups 1-3 were orally infected with 200 metacercariae (mc) and sacrificed at 8 and 28 days post-infection (dpi), and 17 weeks post-infection (wpi), respectively. Group 4 was used as an uninfected control. Apoptosis was detected using immunohistochemistry with a polyclonal antibody against anti-active caspase-3, and transmission electron microscopy (TEM). Eosinophils were identified using the Hansel stain in serial sections for caspase-3, and by ultrastructural features using TEM. At 8 and 28 dpi, numerous caspase-3(+) eosinophils were mainly found at the periphery of acute hepatic necrotic foci. The percentage of caspase -3(+) apoptotic eosinophils in the periphery of necrotic foci was high (46.1-53.9) at 8 and 28 dpi, respectively, and decreased in granulomas found at 28 dpi (6%). Transmission electron microscopy confirmed the presence of apoptotic eosinophils in hepatic lesions at 8 and 28 dpi. At 17 wpi, apoptotic eosinophils were detected in the infiltrate surrounding some enlarged bile ducts containing adult flukes. This is the first report of apoptosis induced by F. hepatica in sheep and the first study reporting apoptosis in eosinophils in hepatic inflammatory infiltrates in vivo. The high number of apoptotic eosinophils in acute necrotic tracts during the migratory and biliary stages of infection suggests that eosinophil apoptosis may play a role in F. hepatica survival during different stages of infection.

Alopecia areata universalis in a dog

BACKGROUND

Alopecia areata is a T-cell mediated autoimmune disease that occurs in humans and various other mammalian species. When the disease progresses to total alopecia it is defined as alopecia areata universalis (AAU), although this outcome has only been described in humans.

HYPOTHESIS/OBJECTIVES

To describe a case of canine alopecia areata universalis and its clinical outcome after 22 months of follow-up.

ANIMAL

A 9-year-old intact male cross-breed hunting dog was presented with generalized and complete noninflammatory alopecia of 12-14 months duration.

METHODS

Clinical examination; histopathological and immunohistochemical examination of skin biopsies.

RESULTS

There was loss of all body hair including eyelashes and vibrissae. The histopathological and immunohistochemical findings supported a diagnosis of long-standing alopecia areata. Treatment with oral ciclosporin was associated with hair regrowth but muzzle hair, most eyelashes and whiskers were still lacking after 17 months of therapy.

CONCLUSIONS AND CLINICAL IMPORTANCE

To the best of the author's knowledge this is the first documented case of canine AAU. The clinical and histopathological features were consistent with a diagnosis of AAU as defined in humans. Treatment with oral ciclosporin resulted in near complete resolution of the alopecia, but after 5 months without treatment the alopecia did not relapse and spontaneous resolution cannot be ruled out.

Immunohistochemical characterisation of parasitic pneumonias of dolphins stranded in the Canary Islands

This is the first work that applies immunohistochemistry in the characterisation of the inflammatory infiltrate of verminous bronchopneumonia associated with lungworm parasites in stranded dolphins. Samples from three different species (Stenella coerulealba, Stenella frontalis and Delphinus delphis) stranded in the Canary Islands were used. The most common findings found in these animals varied from bronchitis to verminous bronchopneumonia with different degree of severity. The immunohistochemical study showed variable expressions of Lysozyme, MHC-II, iNOS and IgG. The main population presenting in the inflammatory infiltrates were CD3(+) lymphocytes. However, moderate number of Foxp3(+) lymphocytes was found in lymph nodes even though no Foxp3(+) cells were found in lung lesions in any of the samples analysed. This study revealed that lung lesions showed a chronic inflammatory infiltrate mainly composed by lymphocytes CD3(+). Deeper studies are needed in order to provide a more complete scope about the infiltrates involved in these types of lesions.

Mucoperiosteal Exostoses in the Tympanic Bulla of African Lions (Panthera leo)

Mucoperiosteal exostoses (MpEs) of the tympanic bulla (TB), also referred as middle-ear otoliths, have been occasionally described in dogs and cats in association with clinical signs of otitis media or as an incidental finding, but they have not been recorded in other species. In this report, we describe the radiographic, gross, and histopathologic features of MpEs in 8 African lions ( Panthera leo). All animals (5 males and 3 females) were adults that had been kept in captivity and had their skeletons conserved as part of an anatomic academic collection. A radiographic study revealed mineralized structures in the TB consistent with MpEs in 7 of the 16 examined TB; a computed tomography study identified MpEs in 12 of the 16 TB. Six TB from 4 lions were sectioned, and several MpEs were demineralized for histopathologic analysis. Grossly, MpEs appeared variable in number and shape. Some were globular structures that were loosely attached to the mucosal surface of the TB; others were isolated to coalescent bone spicules extending from the mucoperiosteum. Position was also variable, but MpEs frequently developed in the hypotympanum, especially on the ventromedial aspect of the TB wall. Microscopically, MpEs were composed of osteonal bone growing from the periosteum and not by dystrophic calcification of necrotic tissue debris, as is hypothesized in dogs.

Biliary cirrhosis caused by Campula spp. in a dolphin and four porpoises

Biliary cirrhosis produced by Campula spp. is described in 1 striped dolphin Stenella coeruleoalba and 4 harbour porpoises Phocoena phocoena. The hepatic lesions consisted of severe proliferation of fibrous connective tissue with loss of the lobular pattern, nodular regeneration of the hepatic tissue, bile duct hyperplasia and severe inflammatory infiltrate composed of eosinophils, macrophages, lymphocytes and plasma cells. These lesions were associated with severe infestation by Campula spp. Although inflammatory and degenerative hepatic lesions are frequently found in stranded dolphins, biliary cirrhosis has not been previously reported in cetaceans. Massive infestation by these parasites should be included as a cause of hepatic failure resulting in stranding of marine mammals.

Immunopathological study of parasitic cholangitis in cetaceans

This paper describes the immunophenotype of cellular inflammatory infiltrates in chronic cholangitis in six common dolphins (Delphinus delphis), four striped dolphins (Stenella coeruleoalba), three Atlantic spotted dolphins (Stenella frontalis) and one pygmy sperm whale (Kogia Breviceps) found stranded along the coasts of the Canary Islands (Spain). A panel of 5 antibodies previously tested in dolphins (anti-CD3, -IgG, -MHC class II, -S100 protein and -lysozyme) were used. The present work also reports cross reactivity with dolphin antigens of two antibodies not used to date in dolphins (anti-mouse iNOS and anti-mouse Foxp3). The most common type of cholangitis found was chronic granulomatous cholangitis, associated with the presence of the parasite Campula spp., or its eggs in bile ducts. The cellular composition of the hepatic inflammatory infiltrate associated to chronic parasitic cholangitis was closely similar to that found in the cortex of control lymph nodes, including the presence of S100(+) and MHC class II(+) dendritic-like cells in lymphoid follicles and interfollicular areas. Only occasional macrophages expressed iNOS, whereas Foxp3(+) lymphocytes were not found in any of the lesions described in the different types of cholangitis.

Peripheral blood lymphocyte subsets in Fasciola hepatica infected and immunised goats

The proportions of CD4(+), CD8(+) and WC1+ T lymphocytes from peripheral blood using flow cytometry were investigated in goats infected with Fasciola hepatica and previously immunised with recombinant Cathepsin-L1 (rCL1) and Glutathione-S-transferase sigma class (GST). The immunisation trial did not induce protective responses, and no significant differences were recorded between immunised and non-immunised groups. However, there was a significant decrease in the proportion of CD4(+) T lymphocytes in the infected groups both at 5 weeks post-infection (wpi), coinciding with the migratory stage of the infection, and at 12 wpi in the biliary stage of the infection. The proportional decrease in this circulating population may be related to the recruitment of CD4(+) T cells in liver and hepatic lymph nodes and also to the immunomodulatory effect of the parasite through the interaction of F. hepatica excretory-secretory products (FhESP) with this cell population. To date, this is the first report about the effect of F. hepatica infection in peripheral lymphocyte subsets in goats.

Early hepatic and peritoneal changes and immune response in goats vaccinated with a recombinant glutathione transferase sigma class and challenged with Fasciola hepatica

Changes and local immune response were evaluated in the peritoneal cell populations, duodenal lamina propria and liver from goats immunized with recombinant glutathione transferase sigma class (rFhGST-S1) during early stages of infection with Fasciola hepatica. Group 1 (n=7) was unimmunized and uninfected; group 2 (n=10) was immunized with adjuvant Quil A and infected; group 3 (n=10) was immunised with rFhGST-S1 and infected. Three goats from each group were killed at 7-9 days post-infection (dpi) to evaluate early changes and immune response. The remaining goats were killed at 15 weeks post-infection (wpi). rFhGST-S1 vaccination induced variable response: three goats showed low fluke burden at 15 wpi and two goats showed low hepatic damage at early infection stages. This response was associated to a severe infiltrate of eosinophils in peritoneal fluid and hepatic necrotic foci, high iNOS expression in peritoneal cells and abundant infiltrate of eosinophils surrounding hepatic migrating flukes. T lymphocyte subsets were found in the vicinity of necrotic areas but they were absent in the vicinity of migrating larvae. No significant variation for T cell subsets, except for CD4 and γδ T lymphocytes, that were higher in the Quil A group compared to the rFhGST-S1 group. Expression of IL4 and IFN-γ in the hepatic inflammatory infiltrates was very occasional.

Early and late peritoneal and hepatic changes in goats immunized with recombinant cathepsin L1 and infected with Fasciola hepatica

The aim of the present study was to study peritoneal and hepatic changes during early [7-9 days postinfection (dpi)] and late [15 weeks postinfection (wpi)] infection of goats immunized with recombinant F. hepatica pro cathepsin L1 (rCL1) in Quil A and challenged with Fasciola hepatica. Despite finding no significant reduction in fluke burdens between the control and immunized group, at 15 dpi the rCL1-vaccinated group showed significantly higher weight gain and reduced severity of hepatic lesions compared with the control group that received only Quil A. In the rCL1-vaccinated group, two of three goats sacrificed at 7-9 dpi had little hepatic damage and had a higher percentage of peritoneal eosinophils and elevated induced nitric oxide synthase (iNOS) expression in peritoneal cells than the goats from the control group. Moreover, while these two goats showed a heavy infiltration of eosinophils surrounding migrating flukes, the remaining animals examined at 7-9 dpi had no inflammatory infiltration surrounding migrating flukes. Two out of seven goats in the rCL1-vaccinated group had low fluke burdens and little hepatic damage at 15 wpi, suggesting an effective protective response in some of the vaccinated goats. This protective response did not correlate with peripheral eosinophilia or with serum titres of anti-rCL1 immunoglobulin (Ig) G. The results of the present work suggest that an eosinophil-mediated immune response plays a crucial role in the early effective host response against F. hepatica in goats. Adjuvants designed to increase cell-mediated immunity should be tested in future vaccine trials against F. hepatica.

The Sigma class glutathione transferase from the liver fluke Fasciola hepatica

Background

Liver fluke infection of livestock causes economic losses of over US$ 3 billion worldwide per annum. The disease is increasing in livestock worldwide and is a re-emerging human disease. There are currently no commercial vaccines, and only one drug with significant efficacy against adult worms and juveniles. A liver fluke vaccine is deemed essential as short-lived chemotherapy, which is prone to resistance, is an unsustainable option in both developed and developing countries. Protein superfamilies have provided a number of leading liver fluke vaccine candidates. A new form of glutathione transferase (GST) family, Sigma class GST, closely related to a leading Schistosome vaccine candidate (Sm28), has previously been revealed by proteomics in the liver fluke but not functionally characterised.

Methodology/Principal Findings

In this manuscript we show that a purified recombinant form of the F. hepatica Sigma class GST possesses prostaglandin synthase activity and influences activity of host immune cells. Immunocytochemistry and western blotting have shown the protein is present near the surface of the fluke and expressed in eggs and newly excysted juveniles, and present in the excretory/secretory fraction of adults. We have assessed the potential to use F. hepatica Sigma class GST as a vaccine in a goat-based vaccine trial. No significant reduction of worm burden was found but we show significant reduction in the pathology normally associated with liver fluke infection.

Conclusions/Significance

We have shown that F. hepatica Sigma class GST has likely multi-functional roles in the host-parasite interaction from general detoxification and bile acid sequestration to PGD synthase activity.

Combating neglected parasitic diseases is of paramount importance to improve the health of human populations and/or their domestic animals. Uncovering key roles in host-parasite interactions may support the vaccine potential portfolio of a parasite protein. Fasciola hepatica causes global disease in humans and their livestock but no commercial vaccines are available. Members of the Sigma class glutathione transferase (GST) family have long been highlighted as vaccine candidates towards parasitic flatworms. To this end, a Sigma class GST is currently undergoing phase II clinical trials to protect against infection from the schistosomes. In this study we characterise the protein from F. hepatica following four work pathways that 1) confirm its designation as a Sigma class GST using substrate profiling, 2) assess prostaglandin synthase activity and its effect on host immune cells, 3) localise the Sigma GST within adult fluke and between ontogenic stages and 4) measure its potential as a vaccine candidate. The work presented here shows F. hepatica Sigma class GST to have key host-parasite roles and we suggest, warrants further investigation for inclusion into vaccine formulations.

Humoral immune response in goats immunised with cathepsin L1, peroxiredoxin and Sm14 antigen and experimentally challenged with Fasciola hepatica

The humoral immune response was analysed in goats immunised with FhCL1, FhPrx, Sm14, and experimentally challenged with Fasciola hepatica. All immunised animals developed significant levels of anti-fluke specific antibodies and those immunised with FhCL1 showed the highest antibody titre. After experimental infection, an increase in the antibody level was detected only in goats immunised with FhCL1. In the adjuvant-control animals, the experimental challenge induced significant production of specific antibodies against FhCL1, FhPrx and Sm14. While liver fluke specific humoral responses were seen in all groups, no significant protection in any of the vaccinated groups was found.

Concurrent pulmonary adenocarcinoma and silicate pneumoconiosis in a red-legged partridge (Alectoris rufa)

An adult red-legged partridge (Alectoris rufa) presented with concurrent pulmonary carcinoma and severe silicosis. The animal was submitted to the Veterinary Teaching Hospital of the University of Córdoba (Spain) because of respiratory signs, and it died during clinical examination. At postmortem examination, numerous firm, whitish to yellowish nodules involving the lungs, mainly the right lobe, were found. The histopathologic study revealed numerous peribronchiolar large granulomatous lesions composed of macrophages, which showed abundant cytoplasm containing numerous birefringent crystals identified as silicates by transmission electron microscopy. An epithelial neoplasm showing papillary, acinar, and solid patterns occupied large areas of the pulmonary parenchyma. The histopathologic and immunohistochemical features were consistent with a pulmonary carcinoma. Small tumor nests were often located close to the granulomatous lesions. This is the first report of concurrent pneumoconiosis and pulmonary carcinoma in a nonhuman species.

Evaluation of local immune response to Fasciola hepatica experimental infection in the liver and hepatic lymph nodes of goats immunized with Sm14 vaccine antigen

Protection against Fasciola hepatica in goats immunized with a synthetic recombinant antigen from Schistosoma mansoni fatty acid-binding protein 14 (rSm14) was investigated by assessing worm burdens, serum levels of hepatic enzymes, faecal egg count and hepatic damage, which was evaluated using gross and microscopic morphometric observation. The nature of the local immune response was assessed by examining the distribution of CD2+, CD4+, CD8+ and γ´+ T lymphocytes along with IgG+, IL-4+ and IFN-γ+ cells in the liver and hepatic lymph nodes (HLN). The goats used consisted of group 1 (unimmunized and uninfected), group 2 [infected control - immunized with Quillaia A (Quil A)] and group 3 (immunized with rSm14 in Quil A and infected), each containing seven animals. Immunization with rSm14 in Quil A adjuvant induced a reduction in gross hepatic lesions of 56.6% (p < 0.001) and reduced hepatic and HLN infiltration of CD2+, CD4+, CD8+ and γ´+ T lymphocytes as well as IL-4+ and IFN-γ+ cells (p < 0.05). This is the first report of caprine immunization against F. hepatica using a complete rSm14 molecule derived from S. mansoni. Immunization reduced hepatic damage and local inflammatory infiltration into the liver and HLN. However, considering that Quil A is not the preferential/first choice adjuvant for Sm14 immunization, further studies will be undertaken using the monophosphoryl lipid A-based family of adjuvants during clinical trials to facilitate anti-Fasciolavaccine development.

Upregulation of parathyroid VDR expression by extracellular calcium is mediated by ERK1/2-MAPK signaling pathway

We have previously demonstrated that the activation of rat parathyroid calcium-sensing receptor (CaSR) upregulates VDR expression in vivo (Garfia B, Cañadillas S, Luque F, Siendones E, Quesada M, Almadén Y, Aguilera-Tejero E, Rodríguez M. J Am Soc Nephrol 13: 2945–2952, 2002; Rodriguez ME, Almaden Y, Cañadillas S, Canalejo A, Siendones E, Lopez I, Aguilera-Tejero E, Martin D, Rodriguez M. Am J Physiol Renal Physiol 292: F1390–F1395, 2007). The present study was designed to characterize the signaling system that mediates the stimulation of parathyroid VDR gene expression by extracellular calcium. Experiments were performed in vitro by the incubation of rat parathyroid glands and in vivo with normal and uremic (Nx) rats receiving injections of CaCl2or EDTA to obtain hypercalcemic or hypocalcemic clamps. A high calcium concentration increased VDR expression. The addition of arachidonic acid (AA) to the low-calcium medium produced an increase in VDR mRNA of the same magnitude as that observed with high calcium. The addition of ionophore to the low-calcium medium also increased VDR mRNA expression. High calcium or the addition of AA to the low-calcium medium induced the activation (phosphorylation) of ERK1/2-MAPK. The specific inhibition of the ERK1/2-MAPK activity prevented the stimulation of VDR expression by high calcium or AA. These results suggest that AA regulates parathyroid VDR gene expression through the activation of the ERK1/2-MAPK. CaSR activation induced the activation of transcription factor Sp1, but not of NF-κB p50 or p65 or activator protein-1. The addition of AA to the low-calcium medium increased specific DNA-binding activity of Sp1 to almost the same level as high calcium, which was prevented by the inhibition of ERK1/2. Furthermore, mithramycin A (a Sp1 inhibitor) prevented the upregulation of VDR mRNA by high calcium. Finally, both sham and Nx hypercalcemic rats showed similar increased levels of VDR mRNA compared with sham and Nx hypocalcemic rats. Our results demonstrate that extracellular calcium stimulates VDR expression in parathyroid glands through the elevation of the cytosolic calcium level and the stimulation of the PLA2-AA-dependent ERK1/2-pathway. Furthermore, the transcription factor Sp1 mediates this effect.