Leishmania phosphatase PP5 is a regulator of HSP83 phosphorylation and essential for parasite pathogenicity

Next-Generation Leishmanization: Revisiting Molecular Targets for Selecting Genetically Engineered Live-Attenuated Leishmania

Despite decades of research devoted to finding a vaccine against leishmaniasis, we are still lacking a safe and effective vaccine for humans. Given this scenario, the search for a new prophylaxis alternative for controlling leishmaniasis should be a global priority. Inspired by leishmanization-a first generation vaccine strategy where live L. major parasites are inoculated in the skin to protect against reinfection-live-attenuated Leishmania vaccine candidates are promising alternatives due to their robust elicited protective immune response. In addition, they do not cause disease and could provide long-term protection upon challenge with a virulent strain. The discovery of a precise and easy way to perform CRISPR/Cas-based gene editing allowed the selection of safer null mutant live-attenuated Leishmania parasites obtained by gene disruption. Here, we revisited molecular targets associated with the selection of live-attenuated vaccinal strains, discussing their function, their limiting factors and the ideal candidate for the next generation of genetically engineered live-attenuated Leishmania vaccines to control leishmaniasis.

Comparison of endogenous development, invasion ability and apoptotic features between diclazuril resistant and sensitive strains of Eimeria tenella

Diclazuril (DIC) is widely used in the poultry industry to control coccidiosis. However, drug resistance makes it less effective, and the underlying mechanism remains unclear. One DIC-resistant E. tenella (RE) isolate and one sensitive E. tenella (SE) isolate were used to compare the differences in their endogenous development, pathogenicity, invasion-related gene expression and apoptotic characteristics. Chickens were allocated into four groups to receive RE or SE strain and their corresponding DIC treatment or not. Caeca tissues were sampled at 96 h, 120 h and 144 h post-infection (PI) for pathological analysis. Meanwhile, second-generation merozoites (Mz2) were separated at 120 h PI to detect alterations in mitochondrial membrane potential (MMP), apoptotic rate and caspase-3 activity and mRNA expression of protein phosphatase 5 (PP5), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), actin depolymerizing factor (ADF) and microneme proteins (MICs). Haematoxylin and eosin staining revealed that DIC treatment strictly blocked the development of the SE strain but slightly affected the RE strain. Meanwhile, the number of SE Mz2 and their MMP decreased at the same time the apoptotic rate increased after DIC treatment. Real-time quantitative PCR and caspase-3 activity studies demonstrated that Mz2 from the RE strain had higher mRNA expression of ADF and MICs along with no significant changes in GAPDH and caspase-3 activity under DIC pressure compared to its control; in contrast, the mRNA expression of ADF, MICs and PP5 was markedly suppressed in Mz2 from SE with upregulated caspase-3 activity and GAPDH transcription. In addition, the mRNA expression of GAPDH and PP5 in Mz2 from RE was remarkably higher than that of SE. Taken together, the higher mRNA expression of invasion-related genes and almost unaffected endogenous development provide a better understanding of coccidian resistance to DIC.

Protein Phosphatase PP2C Identification in Entamoeba spp

Entamoeba histolytica is the causative agent of amoebiasis, and Entamoeba dispar is its noninvasive morphological twin. Entamoeba invadens is a reptilian parasite. In the present study, Western blot, phosphatase activity, immunofluorescence, and bioinformatic analyses were used to identify PP2C phosphatases of E. histolytica, E. dispar, and E. invadens. PP2C was identified in trophozoites of all Entamoeba species and cysts of E. invadens. Immunoblotting using a Leishmania mexicana anti-PP2C antibody recognized a 45.2 kDa PP2C in all species. In E. histolytica and E. invadens, a high molecular weight element PP2C at 75 kDa was recognized, mainly in cysts of E. invadens. Immunofluorescence demonstrated the presence of PP2C in membrane and vesicular structures in the cytosol of all species analyzed. The ~75 kDa PP2C of Entamoeba spp. shows the conserved domain characteristic of phosphatase enzymes (according to in silico analysis). Possible PP2C participation in the encystation process was discussed.

Parasite protein phosphatases: biological function, virulence, and host immune evasion

Protein phosphatases are enzymes that dephosphorylate tyrosine and serine/threonine amino acid residues. Although their role in cellular processes has been best characterized in higher eukaryotes, they have also been identified and studied in different pathogenic microorganisms (e.g., parasites) in the last two decades. Whereas some parasite protein phosphatases carry out functions similar to those of their homologs in yeast and mammalian cells, others have unique structural and/or functional characteristics. Thus, the latter unique phosphatases may be instrumental as targets for drug therapy or as markers for diagnosis. It is important to better understand the involvement of protein phosphatases in parasites in relation to their cell cycle, metabolism, virulence, and evasion of the host immune response. The up-to-date information about parasite phosphatases of medical and veterinarian relevance is herein reviewed.

Involvement of Leishmania Phosphatases in Parasite Biology and Pathogeny

In the Leishmania lifecycle, the motile promastigote form is transmitted from the sand fly vector to a mammalian host during a blood meal. Inside vertebrate host macrophages, the parasites can differentiate into the amastigote form and multiply, causing leishmaniasis, one of the most significant neglected tropical diseases. Leishmania parasites face different conditions throughout their development inside sand flies. Once in the mammalian host, the parasites have to overcome the microbicide repertoire of the cells of the immune system to successfully establish the infection. In this context, the expression of protein phosphatases is of particular interest. Several members of the serine/threonine-specific protein phosphatase (STP), protein tyrosine phosphatase (PTP), and histidine acid phosphatase (HAcP) families have been described in different Leishmania species. Although their physiological roles have not been fully elucidated, many studies suggest they have an involvement with parasite biology and pathogeny. Phosphatases play a role in adaptation to nutrient starvation during parasite passage through the sand fly midgut. They are also important to parasite virulence, mainly due to the modulation of host cytokine production and impairment of the microbiocidal potential of macrophages. Furthermore, recent whole-genome expression analyses have shown that different phosphatases are upregulated in metacyclic promastigotes, the infective form of the mammalian host. Leishmania phosphatases are also upregulated in drug-resistant strains, probably due to the increase in drug efflux related to the activation of ABC transporters. Throughout this review, we will describe the physiological roles that have been attributed to Leishmania endogenous phosphatases, including their involvement in the adaptation, survival, and proliferation of the parasites inside their hosts.

Heat Shock Proteins as the Druggable Targets in Leishmaniasis: Promises and Perils

Leishmania, the causative agent of leishmaniasis, is an intracellular pathogen that thrives in the insect gut and mammalian macrophages to complete its life cycle. Apart from temperature difference (26 to 37°C), it encounters several harsh conditions, including oxidative stress, inflammatory reactions, and low pH. Heat shock proteins (HSPs) play essential roles in cell survival by strategically reprogramming cellular processes and signaling pathways. HSPs assist cells in multiple functions, including differentiation, adaptation, virulence, and persistence in the host cell. Due to cyclical epidemiological patterns, limited chemotherapeutic options, drug resistance, and the absence of a vaccine, control of leishmaniasis remains a far-fetched dream. The essential roles of HSPs in parasitic differentiation and virulence and increased expression in drug-resistant strains highlight their importance in combating the disease. In this review, we highlighted the diverse physiological importance of HSPs present in Leishmania, emphasizing their significance in disease pathogenesis. Subsequently, we assessed the potential of HSPs as a chemotherapeutic target and underlined the challenges associated with it. Furthermore, we have summarized a few ongoing drug discovery initiatives that need to be explored further to develop clinically successful chemotherapeutic agents in the future.

Relevance and proteomics challenge of functional posttranslational modifications in Kinetoplastid parasites

Protozoan parasitic infections are health, social and economic issues impacting both humans and animals, with significant morbidity and mortality worldwide. Protozoan parasites have complicated life cycles with both intracellular and extracellular forms. As a consequence, protozoan adapt to changing environments in part through a dynamic enzyme-catalyzed process leading to reversible posttranslational modifications (PTMs). The characterization by proteomics approaches reveals the critical role of the PTMs of the proteins involved in host-pathogen interaction. The complexity of PTMs characterization is increased by the high diversity, stoichiometry, dynamic and also co-existence of several PTMs in the same moieties which crosstalk between them. Here, we review how to understand the complexity and the essential role of PTMs crosstalk in order to provide a new hallmark for vaccines developments, immunotherapies and personalized medicine. In addition, the importance of these motifs in the biology and biological cycle of kinetoplastid parasites is highlighted with key examples showing the potential to act as targets against protozoan diseases.