Toxoplasma

Current research projects

Establishment and validation of a guinea pig model for human congenital toxoplasmosis

Toxoplasmosis is one of the most widespread zoonoses worldwide. It is caused by the unicellular parasite Toxoplasma gondii. Among other things, this parasite has a pronounced tropism for neuronal cells. The main host of the parasite is the cat, through whose faeces or raw consumption of infected intermediate hosts humans can become infected. If the mother is infected for the first time during pregnancy in humans and animals, the foetuses are infected vertically, which often results in extensive neural malformations or abortion.

To date, no data exist on the exact cell tropism of T. gondii during brain development.

The aim of this project is to establish the guinea pig as a model animal for congenital toxoplasmosis, in particular for human congenital toxoplasmosis, and to validate it on the basis of pathogen transmission, pathomorphological and immunohistological findings. The project provides the basis for the use of the guinea pig as an animal model for the investigation of scientific questions of high topicality and clinical significance, including the pathogenesis, diagnostics, therapy and prognosis of congenital toxoplasmosis.

(Grochow)

Parasite-host interactions during acute and chronic brain infection of Toxoplasma gondii in murine model

The most important intermediate hosts of T. gondii are rodents. T. gondii can alter the behaviour of infected rodents during chronic infection. Through still not well-known mechanism, infected rats or mice lose their evolutionary fear to felines. They seem to develop attraction to the smell of feline urine. Such attraction increases the chances of infected animals to be near a feline. This allows T. gondi to reach its final host (Felines) more efficiently. A classic example of The Behavioural Manipulation Hypothesis, this trait in chronic toxoplasmosis in rodents should be understood in detail.

This project aims to bring some insights into such specific parasitic manipulation of a host’s behaviour. After assessment of behavioural modifications, we will perform gene expression analysis of acute and chronically infected mice. Additionally, expression of particular genes will be analysed using in vitro infection models. The results of this project could not only help to understand more about Toxoplasma infection, but also to understand which genes are involved in the behaviour of fear.

(Dr. Renteria-Solis)

Parasite-host interactions during co-infection of Toxoplasma gondii and Eimeria spp. in the chicken

Abstract:

The widespread apicomplexan parasites Toxoplasma gondii (T. gondii) and Eimeria tenella (E. tenella) are important pathogens with high prevalence in poultry. The aim of our study was the investigation of mutual influences in co-infected chickens, focusing on immune response and course of infection. Two separate trials were performed using in total 96 1-day-old chickens, divided into four study groups: group NC (negative control, uninfected), group PC-T (oral or intramuscular infection with T. gondii oocysts (trial 1) or tachyzoites (trial 2), respectively), group PC-E (oral infection with E. tenella (trial 1) or E. tenella and Eimeria acervulina (trial 2)), and group TE (co-infection). T. gondii and Eimeria infections were validated by different parameters, and cytokine expression in the gut and spleen was investigated. T. gondii-specific antibodies were detected earliest 4 days post infection (p.i.) by immunoblot and direct DNA detection was possible in 22.1% of all tissue samples from infected chickens. Eimeria spp. merogony seemed to be enhanced by co-infection with T. gondii, interestingly without marked differences in oocyst excretion between co-infected and Eimeria spp. monoinfected chickens. An increase of messenger RNA (mRNA) expression of Th1- (IFN-γ, IL-12, TNF-α) and Th2-related cytokines (IL-10) mainly in groups PC-E and TE was observed, however, without statistically significant differences between co-infection and single infection with Eimeria. In conclusion, most of the measurable immune response could be attributed to Eimeria infection. To the best of our knowledge, this is the first report on co-infection experiments of T. gondii with Eimeria spp. in chickens.

(Hiob)

Parasite-host interactions in Toxoplasma gondii- infected mixed chicken blood cell culture

Abstract:

Toxoplasma gondii has the ability to infect various nucleated cell types in different hosts. The aim of the present study was to investigate which chicken blood cells were targeted by T. gondii in a mixed blood cell culture similar to in vivo conditions and to evaluate parasite–host cell interactions. The study consisted of two subsequent experiments. In experiment 1, we applied T. gondii tachyzoites (ME49) at a multiplicity of infection of 1 tachyzoite per blood cell and examined parasite replication, cytokine, and inducible nitric oxide synthase (iNOS) mRNA expression between 1 h and 48 h post-infection (p.i.) by quantitative PCR. By using T. gondii RH-GFP tachyzoites expressing the green fluorescent protein (GFP) in experiment 2, we aimed for visualizing infected cells by confocal laser scanning microscopy (CLSM) and flow cytometric analysis at 24 h p.i. The parasite replication curve showed a massive decrease of parasite stages until 24 h p.i. followed by an approximately plateau phase. We observed mainly significantly increased iNOS mRNA expression levels in T. gondii-infected culture compared to uninfected cells. Flow cytometry and CLSM data confirmed monocytes/macrophages as main target cells for T. gondii. Moreover, different lymphocytes like B cells and cytotoxic T cells seem to be targeted to a low extent. Our findings indicate that monocytes/macrophages play a key role during T. gondii infection in chicken as host cells and triggering of immune response. To the best of our knowledge, this is the first report of a mixed chicken blood cell culture experimentally infected with T. gondii.

(Hiob)

Toxoplasma gondii-host interactions in placenta

Placental barrier plays a pivotal role in congenital toxoplasmosis. We aim to elucidate which challenges T. gondii faces during placental infection. Additionally we want to investigate gene regulation during immune response. We will analyse samples from in vivo infection in murine model; as well as in vitro confrontations in ovine trophoblasts. For this, we will use traditional histological techniques as well as gene expression analysis of host cytokines and parasite stress. The results of this project will bring insights into Toxoplasma-host interactions during placental infection. It can help to elucidate the role placental barrier plays in congenital toxoplasmosis.

(Dr. Renteria-Solis)