Conference Agenda

Bovine tritrichomonosis is a venereal disease that causes economic losses around the world. Over the last 100 years, the life cycle of the protozoan T. foetus in bovines has only considered venereal transmission, almost exclusively through natural mating from an infected animal to a healthy animal. We provide the first direct evidence that T. foetus can survive the passage through the gastrointestinal tract in bovines and that the parasite can be discharged by feces and contaminate the cow’s reproductive tract. Moreover, we demonstrated that T. foetus under stress conditions can increase its DNA content per parasite without concluding the cytokinesis process (endoreplication), which represents an efficient strategy for subsequent fast multiplication by multiple fissions when the context becomes favorable. Finally, we revealed the existence of novel dormant forms of resistance cyst-like structures (multinucleated or mononucleated polyploid parasites), different than the previously described pseudocysts, that are formed under stress conditions.

Considering that the parasite could be discharged by feces into the environment and their capacity to form resistance structures, we propose a novel possible dissemination form of T. foetus, mainly in extensive livestock production systems of bovines, which should be analyzed in detail in the future.

Trichomonas vaginalis (Tvag) is an extracellular protozoan parasite and the causative agent of trichomoniasis, the most common non-viral sexually transmitted infection worldwide. The parasite lacks pathways for de novo purine biosynthesis and therefore must uptake nucleotides/nucleosides from outside the cell. Here, our study aimed to investigate the involvement of purinergic signaling and extracellular vesicles (EVs) in the pathogenesis of Tvag when grown under starvation (i.e. serum deprivation or glucose restriction) with the goal of identifying new therapeutic targets. Both starvation conditions increased the enzymatic activity of NTPDase and E-5’-N in all Tvag isolates tested and this effect was reversed by adenosine. ATP-induced cytotoxic of Tvag was reversed by adenosine but not by glucose. Starvation altered the expression levels of nucleoside transporters (ENTs): Serum deprivation and glucose restriction caused downregulation and upregulation of ENT expression in Tvag, respectively. Finally, we showed that starvation modulates the release of EVs from trophozoites, suggesting a potential role for nutrient sensing in mediating cellular responses. Whether EVs released from parasites under starvation have a differential impact on host-parasite interactions is currently under investigation. Our research helps to understand a critical route for the survival of Tvag, suggesting nucleoside transporters as potential targets for therapeutic interventions.

Entamoeba histolytica, the causative agent of amoebiasis, performs a process of “cell nibbling”, called trogocytosis, that kills human cells and contributes to tissue damage. We found that E. histolytica displays human membrane proteins on its own surface after performing trogocytosis. We hypothesize that the display of human proteins following trogocytosis directly inhibits host complement activation. We allowed amoebae to perform trogocytosis on human cells and then exposed them to mouse serum. Following trogocytosis of human cells, amoebae were protected from lysis by mouse serum. We exogenously expressed negative regulators of human complement activation, CD46 and CD55, in amoebae. The resulting protection from both human and mouse serum lysis indicated that protein display was sufficient for protection, and that mouse and human complement regulators are functionally interchangeable. We are now allowing amoebae to trogocytose insect Sf9 cells to determine if trogocytosis of these cells still confers protection from lysis by human serum. We anticipate that exogenous expression of human CD46 and/or CD55 in Sf9 cells will restore protection. Since other pathogens are capable of trogocytosis, these studies should improve understanding of virulence mechanisms, and may also shed light on protein trafficking during eukaryotic trogocytosis in general.

Molecular methods are a mainstream method for the detection of protozoan infections in pathology laboratories. Recently, these assays have been applied to screen for novel animal hosts. Due to the difference in microbial flora, there is the potential for cross-reactivity to occur which was previously unexpected. Concerningly, not all studies confirm positive RT-PCR results with sequencing or microscopy. Dientamoeba fragilis is one species for which multiple new hosts have recently been identified. There are large differences in reported positivity rates of D. fragilis between pathology specimens in developed countries with similar healthcare capacities. We assessed the use of two RT-PCR diagnostics previously used to identify novel hosts of Dientamoeba fragilis and clinically. Specimens were collected from cattle, cats and dogs to screen for cross-reactivity. Additionally, the positivity rate between these two assays for 254 unknown human clinical species was compared. Positive results were assessed using melt-curve analysis, cloning and sequencing of an additional locus, and Illumina MiSeq of the RT-PCR product to assess specificity of amplification. Cross-reactivity was identified in both assays when applied to the animal specimens. When these assays are applied to the unknown clinical samples, one assay had 2.5 times more positive results than the other.

Introduction: Giardiasis is one of the most common enteric infections imported from tropical regions to Europe. The number of diagnosed giardiasis cases in the Czech Republic has decreased from over 1,000 annually in the 1990s to fewer than 100 in the early 2020s. However, the number of imported cases has remained stable, except during the COVID-19 pandemic years of 2020-21.

Methods: We conducted a retrospective analysis of the epidemiological and clinical characteristics of patients with laboratory-confirmed giardiasis diagnosed at Bulovka University Hospital (Prague), from 2004 to 2023.

Results: The infection was diagnosed in 357 patients (female:male ratio 0.69). The majority of infections were imported from the Indian Subcontinent (221 cases; 61.0%), followed by Sub-Saharan Africa (44 cases; 12.3%) and Southeast Asia (31 cases; 8.7%). The most common symptoms were diarrhea and bloating. Diagnostics were performed using parasitological stool examination and PCR. Treatment response data were available for 228 patients treated with metronidazole. Of these, 85 (37.3%) were treated successfully, 80 (35.5%) experienced treatment failure, and in 83 (36.4%) no parasitological follow-up was performed. Second-line treatments included combinations of tinidazole with albendazole or paromomycin.

Conclusion: Our study revealed low effectiveness of metronidazole, particularly in patients returning from South Asia.