The Stem Cell Revolution Revealing Protozoan Parasites' Secrets and Paving the Way towards Vaccine Development

Novel systems to study vector-pathogen interactions in malaria

Some parasitic diseases, such as malaria, require two hosts to complete their lifecycle: a human and an insect vector. Although most malaria research has focused on parasite development in the human host, the life cycle within the vector is critical for the propagation of the disease. The mosquito stage of the Plasmodium lifecycle represents a major demographic bottleneck, crucial for transmission blocking strategies. Furthermore, it is in the vector, where sexual recombination occurs generating "de novo" genetic diversity, which can favor the spread of drug resistance and hinder effective vaccine development. However, understanding of vector-parasite interactions is hampered by the lack of experimental systems that mimic the natural environment while allowing to control and standardize the complexity of the interactions. The breakthrough in stem cell technologies has provided new insights into human-pathogen interactions, but these advances have not been translated into insect models. Here, we review in vivo and in vitro systems that have been used so far to study malaria in the mosquito. We also highlight the relevance of single-cell technologies to progress understanding of these interactions with higher resolution and depth. Finally, we emphasize the necessity to develop robust and accessible ex vivo systems (tissues and organs) to enable investigation of the molecular mechanisms of parasite-vector interactions providing new targets for malaria control.

Transcriptomic analysis of the adaptation to prolonged starvation of the insect-dwelling Trypanosoma cruzi epimastigotes

Trypanosoma cruzi is a digenetic unicellular parasite that alternates between a blood-sucking insect and a mammalian, host causing Chagas disease or American trypanosomiasis. In the insect gut, the parasite differentiates from the non-replicative trypomastigote forms that arrive upon blood ingestion to the non-infective replicative epimastigote forms. Epimastigotes develop into infective non-replicative metacyclic trypomastigotes in the rectum and are delivered via the feces. In addition to these parasite stages, transitional forms have been reported. The insect-feeding behavior, characterized by few meals of large blood amounts followed by long periods of starvation, impacts the parasite population density and differentiation, increasing the transitional forms while diminishing both epimastigotes and metacyclic trypomastigotes. To understand the molecular changes caused by nutritional restrictions in the insect host, mid-exponentially growing axenic epimastigotes were cultured for more than 30 days without nutrient supplementation (prolonged starvation). We found that the parasite population in the stationary phase maintains a long period characterized by a total RNA content three times smaller than that of exponentially growing epimastigotes and a distinctive transcriptomic profile. Among the transcriptomic changes induced by nutrient restriction, we found differentially expressed genes related to managing protein quality or content, the reported switch from glucose to amino acid consumption, redox challenge, and surface proteins. The contractile vacuole and reservosomes appeared as cellular components enriched when ontology term overrepresentation analysis was carried out, highlighting the roles of these organelles in starving conditions possibly related to their functions in regulating cell volume and osmoregulation as well as metabolic homeostasis. Consistent with the quiescent status derived from nutrient restriction, genes related to DNA metabolism are regulated during the stationary phase. In addition, we observed differentially expressed genes related to the unique parasite mitochondria. Finally, our study identifies gene expression changes that characterize transitional parasite forms enriched by nutrient restriction. The analysis of the here-disclosed regulated genes and metabolic pathways aims to contribute to the understanding of the molecular changes that this unicellular parasite undergoes in the insect vector.

Perception and Acceptance of COVID-19 Vaccine Among Nurses in Jordan

Introduction

Vaccination against coronavirus disease (COVID-19) is a key factor in protecting vulnerable populations, reducing healthcare burdens, and mitigating the economic and social impacts of the pandemic.

Objective

This study aims to investigate Jordanian nurses' perceptions, acceptance, and factors affecting their decisions toward the COVID-19 vaccines.

Methods

In this study, we conducted a cross-sectional design. Data have been investigated between July 1, 2021 and August 30, 2021. Nurses at three private hospitals in Jordan were surveyed online. The online survey, created using Google Forms, was distributed to nurses via email and social media sites (e.g., WhatsApp and Facebook). Participants were eligible if they were a RN nurse and/or nursing assistance, and had access to the internet via computer and/or smartphone.

Results

Out of 189 responses, 50.6% agreed to receive the COVID-19 vaccine, while 25.5% disagreed, and 23.9% were undecide to receive the vaccine. A large proportion (84.66%) of the respondents had a negative perception toward the vaccine, while only a small minority (15.34%) had a positive perception of it. The older nurses, those with more experience, and those with a higher level of education were more likely to accept the vaccine, with acceptance rates of 56.1%, 54.8%, and 63.9%, respectively.

Conclusion

Of the nurses surveyed, 84.66% had a negative perception of the COVID-19 vaccine, and only 50.6% reported that they would be willing to get vaccinated. It is crucial to address the concerns and reduce apprehension among nurses about the vaccine. Efforts to increase awareness about the importance of vaccination in controlling the disease through workshops and online meetings are needed.

In Vitro Assessment of Anticoccidials: Methods and Molecules

Simple Summary

Coccidiosis is a major problem in poultry production, leading to significant economic losses. Due to the outbreak of resistance to the available treatments, research is focusing on finding new molecules that work against the pathogen. Botanical compounds represent promising alternatives, but reliable in vitro tests are needed for their screening and to understand their mechanism of action. Research in vitro involves studies on the environmental phase of the parasite and studies on the endogenous development, which occurs inside the host cells and that requires cell cultures or in ovo models to be studied. This review aims to summarize the protocols that have been successfully applied so far, as well as to suggest potential cues to improve research on this field. Moreover, as the surge of botanicals as anticoccidial molecules is on the rise, the intent is to provide an overview of the methods to assess their effectiveness in vitro in comparison with conventional drugs.

Abstract

Avian coccidiosis is a disease causing considerable economic losses in the poultry industry. It is caused by Eimeria spp., protozoan parasites characterized by an exogenous–endogenous lifecycle. In vitro research on these pathogens is very complicated and lacks standardization. This review provides a description of the main in vitro protocols so far assessed focusing on the exogenous phase, with oocyst viability and sporulation assays, and on the endogenous phase, with invasion and developmental assays in cell cultures and in ovo. An overview of these in vitro applications to screen both old and new remedies and to understand the relative mode of action is also discussed.