Projects

Parasitized parasites: Investigating the distribution, occurrence and biological role(s) of parasitic protozoan viruses in endemic and emerging parasitic infections in Switzerland-Carmen Faso and Alexander Oberli

Giardiosis and Trichomoniosis are endemic parasitic infections in Switzerland, as opposed to Leishmaniosis which is an emerging parasitosis in Europe. Although these species are very different in terms of their host dynamics, pathogenicity and associated symptoms, they share the common feature of being protist hosts to dedicated viruses. The occurrence, distribution and possible biological role for viral infection in the pathogenicity of these three species, remain largely unexplored. In this project, we aim to address the following questions:

1. What is the epidemiology of parasite viruses for Giardiasis, Leishmaniasis and Trichomoniasis and is more than one circulating viral strain present?
2. What are the consequences of infection with parasitized parasites in vitro and in vivo?

To do this, we plan to employ an omics-based approach whereby all Giardiasis, Trichomoniasis and Leishmaniasis -positive samples supplied across a Swiss network of specialized diagnostic centers over the coming three years shall be screened for viral sequences derived from parasitic protozoan viruses. In a second step and depending on our findings, we would perform in vitro (cell culture) and in vivo (animal models) to investigate the biological role (if any) for these viruses in modulating parasite virulence.

Novel parasite diagnostic tools

1). Giardia lamblia - Carmen Faso and Alexander Oberli

Giardia lamblia (syn. intestinalis, duodenalis) is a ubiquitous intestinal protist parasite, responsible for over 300 Mio diagnosed cases of waterborne diarrheal disease called Giardiasis. Similar to other parasitic species, G. lamblia differentiates to cysts to progress in its life cycle. The cyst is the transmission agent of Giardiosis and consists of the parasite surrounded by a self-secreted impermeable fibrillar mesh. Routine detection and diagnostic tools for Giardia cysts in patient samples and drinking water are limited to time-consuming microscopic analyses or protein detection using a single proprietary monoclonal antibody in an ELISA set-up. New detection and diagnostic tools are needed.

Adapted from, Faso, C., Bischof, S., & Hehl, A. B. (2013). The proteome landscape of Giardia lamblia encystation. PloS one, 8(12), e83207. https://doi.org/10.1371/journal.pone.0083207; hpie: hours post induction of encystation; CWP1: cyst-wall protein 1; DIC: differential interference contrast. Scale bar: 1µm.

Funding sources: Novartis Foundation for Medical-Biological Research

Collaborators: Adrian Hehl, Institute of Parasitology-University of Zurich

2). Strongyloides - Alexander Oberli and Bruno Gottstein

Strongyloides stercoralis is among the most clinically important nematodes of the 21^st century and the most prominent feature of infection is the extremely long patency through its very unique auto-infection cycle. Complications of infection like hyperinfection syndrome and disseminated strongyloidiosis are strongly associated with immunosuppression and organ transplantation.

Serological tests for strongyloidiasis have a higher sensitivity than stool testing but serological test performances vary and might overestimate prevalence as a result of false-positive tests due to cross-reactions with other parasites and long-term persistence of antibodies. There is a need for research for the rapid diagnosis and early treatment of solid-organ donors and recipients before transplantation. The number of false-positive results may be reduced by subsequent performance of a reliable confirmatory Western blot.

3). Cell-free DNA PCR - Alexander Oberli and Bruno Gottstein

Human alveolar Echinoccocosis (AE) is a zoonotic parasitic infection caused by Echinococcus multilocularis which is mostly fatal without adequate treatment such as surgery or antiparasitic therapy. The incidence for AE is constantly rising in Europe and Asia with immunocompromised individuals being at highest risk. At present, diagnosis of AE is primarily based on imaging techniques combined with serological tests. However, serology results may be negative, especially in AE patients who are immunocompromised.

The detection of circulating cell-free DNA (ccfDNA) is currently being used as an analytical tool for the diagnosis, prognosis and therapy monitoring in oncology. Recent reports demonstrate that ccfDNA is detectable in many kinds of parasitic diseases such as Plasmodium spp., Trypanosoma spp. Schistosoma spp. and Echinococcus spp. and have the potential to support the existing diagnostic tools. We aim to develop and optimize an Echinococcus multilocularis ccfDNA real-time PCR. Patient sera will be used to assess the potential of this ccfDNA PCR for the monitoring of treatment efficacy after surgery.

Immuno-parasitology of Alveolar Echinococcosis - Bruno Gottstein, Junhua Wang, Alexander Oberli and Britta Lundström-Stadelmann

Alveolar echinococcosis (AE) is one of the clinically most severe zoonotic helminthic diseases in humans. It is characterized by a chronic progressive hepatic damage caused by the continuous proliferation of the larval stage (metacestode) of Echinococcus multilocularis. By increasing evidence, AE appears today as an opportunistic infection, based on an increased number of AE patients having received immunosuppressive therapy that renders them more susceptible to develop AE. Mechanistically, AE patients exhibit a periparasitic down-regulated immune response that is triggered by the parasite and orients local immunity towards anergy.

Since Treg cells play a crucial role in disease (AE) progression, there is an inherent interest in co-inhibitory receptors that could be exploited for inhibiting Treg effector functions such as PD1/PDL1. In this immunological context, anti-PD-L1 administration yielded in a decreased parasite development in an experimental murine AE model. Conclusively, new immunotherapeutical tools may be developed, with the aim to reverse the periparasitic anergic situation and thus to allow immunity to curatively control AE also in human patients.

Immunomodulatory processes are experimentally studied in appropriate murine models in close collaboration with Anne-Pauline Bellanger (CHU Besançon) and Peter Deplazes (University of Zürich), an in clinical studies (human AE-patients) with Guido Beldi (Inselspital Bern), Solange Bresson-Hadni (HU Geneva. Laurence Millon (CHU Besançon) and Beate Grüner (University Hospital Ulm).

One putative option to prevent AE is to immunize intermediate hosts with appropriate vaccines. Two vaccine candidates have been developed (recEm14-3-3 and recEm95) in Bern, which are presently being experimentally used in primate populations that exhibit high risk of infection and disease. One group consists of a population of Macaca fascicularis at the Zoo of Basel. The same vaccination strategy is experimentally investigated at the German Primate Center in Göttingen with a group of Macaca mulatta. Furthermore, primates at the Vietnamese 'Endangered Primate Rescue Center (EPRC)' exhibit health problems due to infection with Echinococcus ortleppi, a parasite closely related to E. multilocularis. A specific vaccine (Eo95) was synthesized in Bern, and is now being experimentally assessed to protect endangered Langur primates against this parasitic disease. Vaccination studies are carried out in collaboration with Prof. Britta Lundström-Stadelmann from the Institute of Parasitology at the University of Bern.