A mucin-like peptide from Fasciola hepatica induces parasite-specific Th1-type cell immunity

A Vaccine Based on Kunitz-Type Molecule Confers Protection Against Fasciola hepatica Challenge by Inducing IFN-γ and Antibody Immune Responses Through IL-17A Production

Fasciola hepatica is helminth parasite found around the world that causes fasciolosis, a chronic disease affecting mainly cattle, sheep, and occasionally humans. Triclabendazole is the drug of choice to treat this parasite. However, the continuous use of this drug has led to the development of parasite resistance and, consequently, the limitation of its effectiveness. Hence, vaccination appears as an attractive option to develop. In this work, we evaluated the potential of F. hepatica Kunitz-type molecule (FhKTM) as an antigen formulated with a liquid crystal nanostructure formed by self-assembly of 6-O-ascorbyl palmitate ester (Coa-ASC16) and the synthetic oligodeoxynucleotide containing unmethylated cytosine-guanine motifs (CpG-ODN) during an experimental model of fasciolosis in mice, and we further dissected the immune response associated with host protection. Our results showed that immunization of mice with FhKTM/CpG-ODN/Coa-ASC16 induces protection against F. hepatica challenge by preventing liver damage and improving survival after F. hepatica infection. FhKTM/CpG-ODN/Coa-ASC16-immunized mice elicited potent IFN-γ and IL-17A with high levels of antigen-specific IgG1, IgG2a, and IgA serum antibodies. Strikingly, IL-17A blockade during infection decreased IgG2a and IgA antibody levels as well as IFN-γ production, leading to an increase in mortality of vaccinated mice. The present study highlights the potential of a new vaccine formulation to improve control and help the eradication of F. hepatica infection, with potential applications for natural hosts such as cattle and sheep.

Serodiagnostic methods for diagnosing larval toxocariasis

Toxocariasis is a human infection primarily caused by larvae of Toxocara canis from dogs, and also by T. cati from cats. Children have a more significant risk of acquiring the infection due to their closer contact with pets, and greater chances of ingesting soil. Diagnosis of toxocariasis is based on clinical, epidemiological, and serological data. Indirect IgG ELISA is a widely used serodiagnostic method for toxocariasis, with native T. canis TES most commonly used as the antigen. Western blots, using the same antigen, can be used to confirm positive ELISA findings to reduce false-positive results. Improvements in Toxocara serodiagnosis include the use of recombinant TES antigens, simpler and more rapid assay formats, and IgG4 subclass detection. Also, incorporation of recombinant T. cati TES protein increases the diagnostic sensitivity. Development of antigen detection tests using polyclonal and monoclonal antibodies, nanobodies, or aptamers can complement the antibody detection assays, and enhance the effectiveness of the serodiagnosis.

Mucins and Pathogenic Mucin-Like Molecules Are Immunomodulators During Infection and Targets for Diagnostics and Vaccines

Mucins and mucin-like molecules are highly O-glycosylated proteins present on the cell surface of mammals and other organisms. These glycoproteins are highly diverse in the apoprotein and glycan cores and play a central role in many biological processes and diseases. Mucins are the most abundant macromolecules in mucus and are responsible for its biochemical and biophysical properties. Mucin-like molecules cover various protozoan parasites, fungi and viruses. In humans, modifications in mucin glycosylation are associated with tumors in epithelial tissue. These modifications allow the distinction between normal and abnormal cell conditions and represent important targets for vaccine development against some cancers. Mucins and mucin-like molecules derived from pathogens are potential diagnostic markers and targets for therapeutic agents. In this review, we summarize the distribution, structure, role as immunomodulators, and the correlation of human mucins with diseases and perform a comparative analysis of mucins with mucin-like molecules present in human pathogens. Furthermore, we review the methods to produce pathogenic and human mucins using chemical synthesis and expression systems. Finally, we present applications of mucin-like molecules in diagnosis and prevention of relevant human diseases.

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.

Modulation of Host Immunity by Helminths: The Expanding Repertoire of Parasite Effector Molecules

Helminths are extraordinarily successful parasites due to their ability to modulate the host immune response. They have evolved a spectrum of immunomodulatory molecules that are now beginning to be defined, heralding a molecular revolution in parasite immunology. These discoveries have the potential both to transform our understanding of parasite adaptation to the host and to develop possible therapies for immune-mediated disease. In this review we will summarize the current state of the art in parasite immunomodulation and discuss perspectives on future areas for research and discovery.

Fasciola and fasciolosis in ruminants in Europe: Identifying research needs

Fasciola hepatica is a trematode parasite with a global distribution, which is responsible for considerable disease and production losses in a range of food producing species. It is also identified by WHO as a re-emerging neglected tropical disease associated with endemic and epidemic outbreaks of disease in human populations. In Europe, F. hepatica is mostly associated with disease in sheep, cattle and goats. This study reviews the most recent advances in our understanding of the transmission, diagnosis, epidemiology and the economic impact of fasciolosis. We also focus on the impact of the spread of resistance to anthelmintics used to control F. hepatica and consider how vaccines might be developed and applied in the context of the immune-modulation driven by the parasite. Several major research gaps are identified which, when addressed, will contribute to providing focussed and where possible, bespoke, advice for farmers on how to integrate stock management and diagnosis with vaccination and/or targeted treatment to more effectively control the parasite in the face of increasing the prevalence of infection and spread of anthelmintic resistance that are likely to be exacerbated by climate change.

Worm Control in Livestock: Bringing Science to the Field

Parasitic roundworm infections are ubiquitous in grazing livestock. Chemical control through the frequent 'blanket' administration of anthelmintics (wormers) has been, and remains, the cornerstone in controlling these infections, but this practice is unsustainable. Alternative strategies are available but, even with the plethora of best practice advice available, have yet to be integrated into routine farming practice. This is probably due to a range of factors, including contradictory advice from different sources, changes to advice following increased scientific understanding, and top-down knowledge exchange patterns. In this article, we discuss the worm control options available, the translation of new best practice advice from science bench to field, and ideas for future work and directions.

A mucin-like peptide from Fasciola hepatica instructs dendritic cells with parasite specific Th1-polarizing activity

Fasciolosis is a trematode zoonosis of interest in public health and cattle production. We report here the immunostimulatory effect of a 66 mer mucin-like peptide from Fasciola hepatica (Fhmuc), which synergizes with lipopolysaccharide (LPS) to promote dendritic cell (DC) maturation, endowing these cells with Th1-polarizing capacity. Exposure of DCs to Fhmuc in presence of LPS induced enhanced secretion of pro-inflammatory cytokines and expression of co-stimulatory molecules by DCs, promoting their T cell stimulatory capacity and selectively augmenting IFN-γ secretion by allogeneic T cells. Furthermore, exposure of DCs to Fhmuc augmented LPS-induced Toll-like receptor (TLR) 4 expression on the cell surface. Finally, Fhmuc-conditioned DCs induced parasite specific-adaptive immunity with increased levels of IFN-γ secreted by splenocytes from vaccinated animals, and higher parasite-specific IgG antibodies. However, Fhmuc-treated DC conferred modest protection against F. hepatica infection highlighting the potent immuno-regulatory capacity of the parasite. In summary, this work highlights the capacity of a mucin-derived peptide from F. hepatica to enhance LPS-maturation of DCs and induce parasite-specific immune responses with potential implications in vaccination and therapeutic strategies.