A Stroll Through the History of Monoxenous Trypanosomatids Infection in Vertebrate Hosts

Differential expression of peptidases in Strigomonas culicis wild-type and aposymbiotic strains: from proteomic data to proteolytic activity

BACKGROUND

Strigomonas culicis is a monoxenic trypanosomatid parasite of insects that naturally contains an endosymbiotic bacterium. The aposymbiotic strain can be obtained, making this strain a model for evolutive research about organelle origins. In addition, S. culicis contains homologues of virulence factors of pathogenic trypanosomatids, which functions are waiting for further analysis. In this sense, the publication of S. culicis proteome makes feasible additional investigations regarding the differential expression of peptidases from the wild-type (WT) and the aposymbiotic (APO) strains.

OBJECTIVES

Here, we analysed two proteomic data from S. culicis WT and APO strains screening for peptidases differentially expressed and assessed the differential expression of cysteine and metallopeptidases.

METHODS

A comparative proteomic screening between WT and APO identified 43 modulated peptidases.

FINDINGS

Cysteine and metallopeptidases, such as calpains and GP63, were the major classes, highlighting their significance. GP63 exhibited an increased proteolysis in a specific metallopeptidase substrate, an up-modulation gene expression in RT-PCR, and a higher protein identification by flow cytometry in the aposymbiotic strain. Notwithstanding, the wild-type strain showed enhanced cysteine peptidase activity.

MAIN CONCLUSION

Our study highlighted the endosymbiont influence in S. culicis peptidase expression, with GP63 expression and activity raised in the aposymbiotic strain, whereas cysteine peptidase levels were reduced.

Spotlight on Leishmaniasis Research: Insights from the Special Issue "Emerging Topics in Leishmaniasis Research"

Leishmaniases, caused by dixenous trypanosomatids from the Leishmaniinae subfamily (over 20 Leishmania species), manifest in three primary clinical forms: visceral (VL), cutaneous (CL), and mucocutaneous (MCL) [...].

Molecular evidence of pathogens and endosymbionts in the black horse fly Osca lata (Diptera: Tabanidae) in Southern Chile

Little is known about the role of horse flies in potential pathogen transmission in Chile. This study provides evidence of the molecular detection of microorganisms in southern Chile. In the present study, adult Osca lata horse flies were trapped from Punucapa (39°45'06"S/73°16'08"W, Región de Los Ríos) and Puyehue (40°39'10"S/72°10'57"W, Región de Los Lagos), Chile. Among the 95 samples analyzed by PCR using specific primers, microorganisms were detected in 23.2% (n = 22) of the samples. Rickettsia spp. DNA was detected in 15.8% (n = 15) of the samples, Trypanosomatidae DNA in 5.3% (n = 5) of the samples, and filarial DNA in 2.1% (n = 2) of the samples. This study found that horse flies in the region are capable of carrying a variety of both parasites and endosymbionts. Further research is needed to understand the specific impact of horse flies as mechanical or biological vectors and develop effective control measures to prevent the spread of any microorganisms associated with disease.

Cultivation of monoxenous trypanosomatids: A minireview

Trypanosomatids are obligatory parasites, some of which are responsible for important human and animal diseases, but the vast majority of trypanosomatids are restricted to invertebrate hosts. Isolation and in vitro cultivation of trypanosomatids from insect hosts enable their description, characterization, and subsequently genetic and genomic studies. However, exact nutritional requirements are still unknown for most trypanosomatids and thus very few defined media are available. This mini review provides information about the role of different ingredients, recommendations and advice on essential supplements and important physicochemical parameters of culture media with the aim of facilitating first attempts to cultivate insect-infesting trypanosomatids, with a focus on monoxenous trypanosomatids.

Parasite Detection in Visceral Leishmaniasis Samples by Dye-Based qPCR Using New Gene Targets of Leishmania infantum and Crithidia

Visceral leishmaniasis (VL) is a neglected disease considered a serious public health problem, especially in endemic countries. Several studies have discovered monoxenous trypanosomatids (Leptomonas and Crithidia) in patients with VL. In different situations of leishmaniasis, investigations have examined cases of co-infection between Leishmania spp. and Crithidia spp. These coinfections have been observed in a wide range of vertebrate hosts, indicating that they are not rare. Diagnostic techniques require improvements and more robust tools to accurately detect the causative agent of VL. This study aimed to develop a real-time quantitative dye-based PCR (qPCR) assay capable of distinguishing Leishmania infantum from Crithidia-related species and to estimate the parasite load in samples of VL from humans and animals. The primer LinJ31_2420 targets an exclusive phosphatase of L. infantum; the primer Catalase_LVH60-12060_1F targets the catalase gene of Crithidia. Therefore, primers were designed to detect L. infantum and Crithidia sp. LVH60A (a novel trypanosomatid isolated from VL patients in Brazil), in samples related to VL. These primers were considered species-specific, based on sequence analysis using genome data retrieved from the TriTryp database and the genome assembling of Crithidia sp. LVH60A strain, in addition to experimental and clinical data presented herein. This novel qPCR assay was highly accurate in identifying and quantifying L. infantum and Crithidia sp. LVH60A in samples obtained experimentally (in vitro and in vivo) or collected from hosts (humans, dogs, cats, and vectors). Importantly, the screening of 62 cultured isolates from VL patients using these primers surprisingly revealed that 51 parasite cultures were PCR+ for Crithidia sp. In addition, qPCR assays identified the co-infection of L. infantum with Crithidia sp. LVH60A in two new VL cases in Brazil, confirming the suspicion of co-infection in a previously reported case of fatal VL. We believe that the species-specific genes targeted in this study can be helpful for the molecular diagnosis of VL, as well as for elucidating suspected co-infections with monoxenous-like trypanosomatids, which is a neglected fact of a neglected disease.

Co-infection of Leishmania infantum and a Crithidia-related species in a case of refractory relapsed visceral leishmaniasis with non-ulcerated cutaneous manifestation in Brazil

We report a refractory and relapsed visceral leishmaniasis case in a male child patient followed from 2016 to 2020, whose clinical isolates from multiple relapses were analyzed at the genome level. To the best of our knowledge, it is the first report that both visceral leishmaniasis and non-ulcerated cutaneous leishmaniasis have concomitantly manifested in the same patient. Importantly, sequence analysis revealed that the patient was co-infected with Leishmania infantum and a Crithidia-related parasite, which was previously found in a fatal case of visceral leishmaniasis from the same endemic region.

First Evidence of Co-Circulation of Emerging Leishmania martiniquensis, Leishmania orientalis, and Crithidia sp. in Culicoides Biting Midges (Diptera: Ceratopogonidae), the Putative Vectors for Autochthonous Transmission in Southern Thailand

Since 1996, autochthonous cases of emerging leishmaniasis caused by Leishmania (Mundinia) martiniquensis and Leishmania (Mundinia) orientalis have been more frequently reported, especially in the northern and southern parts of Thailand. However, the accurate identification of their natural vectors and reservoirs remains unconfirmed. Previous studies have suggested that these emerging parasites might be transmitted by other non-phlebotomine vectors. Herein, we speculated that Culicoides biting midges might act as the competent vectors responsible for autochthonous leishmaniasis in southern Thailand. In this research, 187 non-engorged, parous and gravid Culicoides females and 47 blood-engorged ones were trapped from the residences of two recently diagnosed visceral leishmaniasis patients in Sadao District and the unaffected site in Rattaphum District, Songkhla Province, southern Thailand. Species diversity and abundance of biting midges varied among the trapping sites. Using ITS1-PCR and BLASTn analysis, L. martiniquensis was predominantly detected in several Culicoides species, including C. peregrinus, C. oxystoma, C. mahasarakhamense, and C. huffi from the vicinity of patients’ houses; and in C. fordae and C. fulvus from the unaffected site. L. orientalis was also co-circulated in C. peregrinus and C. oxystoma caught near the second patient’s house. Additionally, Crithidia sp. were also detected using SSU rRNA-PCR across Culicoides spp. Host blood meal analysis of eight different Culicoides species from the unaffected site also revealed that all trapped Culicoides had fed on cows and goats, indicating the possible role of these mammalian species as reservoir hosts. Essentially, this study is the first entomological investigation, revealing the co-circulation of emerging trypanosomatids among several species of Culicoides biting midges and strongly supporting the potential role of this insect group as the main vectors responsible for the epidemiology of autochthonous leishmaniasis in southern Thailand.

Molecular Identification of Host Blood Meals and Detection of Blood Parasites in Culicoides Latreille (Diptera: Ceratopogonidae) Collected from Phatthalung Province, Southern Thailand

Five hundred and fifty-nine female biting midges were collected, and seventeen species in six subgenera (Avaritia, Haemophoructus, Hoffmania, Meijerehelea, Remmia, and Trithecoides) and two groups (Clavipalpis and Shortti) were identified. The dominant Culicoides species was C. peregrinus (30.94%), followed by C. subgenus Trithecoides. From blood meal analysis of engorged biting midges, they were found to feed on cows, dogs, pigs, and avians. The majority of blood preferences of biting midges (68%; 49/72) displayed a mixed pattern of host blood DNA (cow and avian). The overall non-engorged biting midge field infectivity rate was 1.44 % (7/487). We detected Leucocytozoon sp. in three Culicoides specimens, one from each species: C. fulvus, C. oxystoma, and C. subgenus Trithecoides. Crithidia sp. was found in two C. peregrinus specimens, and Trypanosoma sp. and P. juxtanucleare were separately found in two C. guttifer. More consideration should be paid to the capacity of biting midges to transmit pathogens such as avian haemosporidian and trypanosomatid parasites. To demonstrate that these biting midges are natural vectors of trypanosomatid parasites, additional research must be conducted with a greater number of biting midges in other endemic regions.

Differences in Charge Distribution in Leishmania tarentolae Leishmanolysin Result in a Reduced Enzymatic Activity

Leishmania tarentolae is a non-pathogenic trypanosomatid isolated from lizards widely used for heterologous protein expression and extensively studied to understand the pathogenic mechanisms of leishmaniasis. The repertoire of leishmanolysin genes was reported to be expanded in L. tarentolae genome, but no proteolytic activity was detected. Here, we analyzed L. tarentolae leishmanolysin proteins from the genome to the structural levels and evaluated the enzymatic activity of the wild-type and overexpressing mutants of leishmanolysin. A total of 61 leishmanolysin sequences were retrieved from the L. tarentolae genome. Five of them were selected for phylogenetic analysis, and for three of them, we built 3D models based on the crystallographic structure of L. major ortholog. Molecular dynamics simulations of these models disclosed a less negative electrostatic potential compared to the template. Subsequently, L. major LmjF.10.0460 and L. tarentolae LtaP10.0650 leishmanolysins were cloned in a pLEXSY expression system into L. tarentolae. Proteins from the wild-type and the overexpressing parasites were submitted to enzymatic analysis. Our results revealed that L. tarentolae leishmanolysins harbor a weak enzymatic activity about three times less abundant than L. major leishmanolysin. Our findings strongly suggest that the less negative electrostatic potential of L. tarentolae leishmanolysin can be the reason for the reduced proteolytic activity detected in this parasite.