An overview on kinetoplastid paraflagellar rod

In silico designing of a novel polyvalent multi-subunit peptide vaccine leveraging cross-immunity against human visceral and cutaneous leishmaniasis: an immunoinformatics-based approach

CONTEXT

Leishmaniasis is a group of vector-borne infectious diseases caused by over 20 pathogenic Leishmania species that are endemic in many tropical and subtropical countries. The emergence of drug-resistant strains, the adverse side effects of anti-Leishmania drugs, and the absence of a preventative vaccination strategy threaten the sensitive population. Recently, many groups of researchers have exploited the field of reverse vaccinology to develop vaccines, focusing chiefly on inducing immunity against either visceral or cutaneous leishmaniasis.

METHODS

This present work involves retrieving twelve experimentally validated leishmanial antigenic protein sequences from the UniProt database, followed by their antigenicity profiling employing ANTIGENpro and Vaxijen 2.0 servers. MHC-binding epitopes for the same were predicted using both NetCTL 1.2 and SYFPEITHI servers, while epitopes for B cell were computed using ABCpred and BepiPred 2.0 servers. The screened epitopes with significantly higher scores were utilized for designing the vaccine construct with appropriate linkers and natural adjuvant. The secondary and tertiary structures of the synthetic peptide were determined by conditional random fields, shallow neural networks, and profile-profile threading alignment with iterative structure assembly simulations, respectively. The 3-D vaccine model was validated through CASP10-tested refinement and the MolProbity web server. Molecular docking and multi-scale normal mode analysis simulation were performed to analyze the best vaccine-TLR complex. Finally, computational immune simulation findings revealed promising cellular and humoral immune responses, suggesting that the engineered chimeric peptide is a potential broad-spectrum vaccine against visceral and cutaneous leishmaniasis.

Ultrastructural and Functional Analysis of a Novel Extra-Axonemal Structure in Parasitic Trichomonads

Trichomonas vaginalis and Tritrichomonas foetus are extracellular flagellated parasites that inhabit humans and other mammals, respectively. In addition to motility, flagella act in a variety of biological processes in different cell types, and extra-axonemal structures (EASs) have been described as fibrillar structures that provide mechanical support and act as metabolic, homeostatic, and sensory platforms in many organisms. It has been assumed that T. vaginalis and T. foetus do not have EASs. However, here, we used complementary electron microscopy techniques to reveal the ultrastructure of EASs in both parasites. Such EASs are thin filaments (3-5 nm diameter) running longitudinally along the axonemes and surrounded by the flagellar membrane, forming prominent flagellar swellings. We observed that the formation of EAS increases after parasite adhesion on the host cells, fibronectin, and precationized surfaces. A high number of rosettes, clusters of intramembrane particles that have been proposed as sensorial structures, and microvesicles protruding from the membrane were observed in the EASs. Our observations demonstrate that T. vaginalis and T. foetus can connect to themselves by EASs present in flagella. The protein VPS32, a member of the ESCRT-III complex crucial for diverse membrane remodeling events, the pinching off and release of microvesicles, was found in the surface as well as in microvesicles protruding from EASs. Moreover, we demonstrated that the formation of EAS also increases in parasites overexpressing VPS32 and that T. vaginalis-VPS32 parasites showed greater motility in semisolid agar. These results provide valuable data about the role of the flagellar EASs in the cell-to-cell communication and pathogenesis of these extracellular parasites.

The distinctive flagellar proteome of Euglena gracilis illuminates the complexities of protistan flagella adaptation

The eukaryotic flagellum/cilium is a prominent organelle with conserved structure and diverse functions. Euglena gracilis, a photosynthetic and highly adaptable protist, employs its flagella for both locomotion and environmental sensing. Using proteomics of isolated E. gracilis flagella we identify nearly 1700 protein groups, which challenges previous estimates of the protein complexity of motile eukaryotic flagella. We not only identified several unexpected similarities shared with mammalian flagella, including an entire glycolytic pathway and proteasome, but also document a vast array of flagella-based signal transduction components that coordinate gravitaxis and phototactic motility. By contrast, the pellicle was found to consist of > 900 protein groups, containing additional structural and signalling components. Our data identify significant adaptations within the E. gracilis flagellum, many of which are clearly linked to the highly flexible lifestyle.

Leishmania 360°: Guidelines for Exosomal Research

Leishmania parasites are a group of kinetoplastid pathogens that cause a variety of clinical disorders while maintaining cell communication by secreting extracellular vesicles. Emerging technologies have been adapted for the study of Leishmania-host cell interactions, to enable the broad-scale analysis of the extracellular vesicles of this parasite. Leishmania extracellular vesicles (LEVs) are spheroidal nanoparticles of polydispersed suspensions surrounded by a layer of lipid membrane. Although LEVs have attracted increasing attention from researchers, many aspects of their biology remain unclear, including their bioavailability and function in the complex molecular mechanisms of pathogenesis. Given the importance of LEVs in the parasite-host interaction, and in the parasite-parasite relationships that have emerged during the evolutionary history of these organisms, the present review provides an overview of the available data on Leishmania, and formulates guidelines for LEV research. We conclude by reporting direct methods for the isolation of specific LEVs from the culture supernatant of the promastigotes and amastigotes that are suitable for a range of different downstream applications, which increases the compatibility and reproducibility of the approach for the establishment of optimal and comparable isolation conditions and the complete characterization of the LEV, as well as the critical immunomodulatory events triggered by this important group of parasites.

De Novo Transcriptome Meta-Assembly of the Mixotrophic Freshwater Microalga Euglena gracilis

Euglena gracilis is a well-known photosynthetic microeukaryote considered as the product of a secondary endosymbiosis between a green alga and a phagotrophic unicellular belonging to the same eukaryotic phylum as the parasitic trypanosomatids. As its nuclear genome has proven difficult to sequence, reliable transcriptomes are important for functional studies. In this work, we assembled a new consensus transcriptome by combining sequencing reads from five independent studies. Based on a detailed comparison with two previously released transcriptomes, our consensus transcriptome appears to be the most complete so far. Remapping the reads on it allowed us to compare the expression of the transcripts across multiple culture conditions at once and to infer a functionally annotated network of co-expressed genes. Although the emergence of meaningful gene clusters indicates that some biological signal lies in gene expression levels, our analyses confirm that gene regulation in euglenozoans is not primarily controlled at the transcriptional level. Regarding the origin of E. gracilis, we observe a heavily mixed gene ancestry, as previously reported, and rule out sequence contamination as a possible explanation for these observations. Instead, they indicate that this complex alga has evolved through a convoluted process involving much more than two partners.

An immunoproteomics approach to identify Leishmania infantum proteins to be applied for the diagnosis of visceral leishmaniasis and human immunodeficiency virus co-infection

The co-infection between visceral leishmaniasis (VL) and human immunodeficiency virus (HIV) has increased in several countries in the world. The current serological tests are not suitable since they present low sensitivity to detect the most of VL/HIV cases, and a more precise diagnosis should be performed. In this context, in the present study, an immunoproteomics approach was performed using Leishmania infantum antigenic extracts and VL, HIV and VL/HIV patients sera, besides healthy subjects samples; aiming to identify antigenic markers for these clinical conditions. Results showed that 43 spots were recognized by antibodies in VL and VL/HIV sera, and 26 proteins were identified by mass spectrometry. Between them, β-tubulin was expressed, purified and tested in ELISA experiments as a proof of concept for validation of our immunoproteomics findings and results showed high sensitivity and specificity values to detect VL and VL/HIV patients. In conclusion, the identified proteins in the present work could be considered as candidates for future studies aiming to improvement of the diagnosis of VL and VL/HIV co-infection.

Cell Cycle-Dependent Flagellar Disassembly in a Firebug Trypanosomatid Leptomonas pyrrhocoris

Current understanding of flagellum/cilium length regulation focuses on a few model organisms with flagella of uniform length. Leptomonas pyrrhocoris is a monoxenous trypanosomatid parasite of firebugs. When cultivated in vitro, L. pyrrhocoris duplicates every 4.2 ± 0.2 h, representing the shortest doubling time reported for trypanosomatids so far. Each L. pyrrhocoris cell starts its cell cycle with a single flagellum. A new flagellum is assembled de novo, while the old flagellum persists throughout the cell cycle. The flagella in an asynchronous L. pyrrhocoris population exhibited a vast length variation of ∼3 to 24 μm, casting doubt on the presence of a length regulation mechanism based on a single balance point between the assembly and disassembly rate in these cells. Through imaging of live L. pyrrhocoris cells, a rapid, partial disassembly of the existing, old flagellum is observed upon, if not prior to, the initial assembly of a new flagellum. Mathematical modeling demonstrated an inverse correlation between the flagellar growth rate and flagellar length and inferred the presence of distinct, cell cycle-dependent disassembly mechanisms with different rates. On the basis of these observations, we proposed a min-max model that could account for the vast flagellar length range observed for asynchronous L. pyrrhocoris. This model may also apply to other flagellated organisms with flagellar length variation.IMPORTANCE Current understanding of flagellum biogenesis during the cell cycle in trypanosomatids is limited to a few pathogenic species, including Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp. The most notable characteristics of trypanosomatid flagella studied so far are the extreme stability and lack of ciliary disassembly/absorption during the cell cycle. This is different from cilia in Chlamydomonas and mammalian cells, which undergo complete absorption prior to cell cycle initiation. In this study, we examined flagellum duplication during the cell cycle of Leptomonas pyrrhocoris With the shortest duplication time documented for all Trypanosomatidae and its amenability to culture on agarose gel with limited mobility, we were able to image these cells through the cell cycle. Rapid, cell cycle-specific flagellum disassembly different from turnover was observed for the first time in trypanosomatids. Given the observed length-dependent growth rate and the presence of different disassembly mechanisms, we proposed a min-max model that can account for the flagellar length variation observed in L. pyrrhocoris.

Pentaplex PCR assay for rapid differential detection of Babesia bigemina, Theileria annulata, Anaplasma marginale and Trypanosoma evansi in cattle

A multiplex PCR (mPCR) assay for simultaneous detection and differentiation of four major haemoparasites in crossbred cattle was established using parasite specific genomic DNA and four sets of primer pairs targeting AMA-1, Tams1, MSP5 and VSG genes of Babesia bigemina, Theileria annulata, Anaplasma marginale and Trypanosoma evansi generating precise amplicons of 448, 156, 382 and 110 bp, respectively. An internal amplification control, 202 bp bovine β-casein gene fragment, was simultaneously amplified with four target genes to avoid false-negative results. The sensitivity of mPCR was 3.44 × 10², 5.9 × 10³, 2.88 × 10² and 3.3 × 10³ copies for B. bigemina, T. annulata, A. marginale and T. evansi, respectively. mPCR of cattle clinical samples (n = 516), suspected for haemoparasites, revealed single haemoparasitic infection in 279 (54.06%) cases, whereas mixed infection was recorded in 54 (10.46%) samples. In clinical samples, coinfection with T. annulata and A. marginale was the most common. The findings of mPCR were consistent with uniplex PCR under field conditions except for subtle variations in A. marginale infection. Overall, the mPCR assay represents an economical, reproducible and robust diagnostic tool for concurrent detection of cattle haemoparasites and large scale epidemiological studies.

Insight into trypanosomosis (Surra) of Indian livestock: Recent updates

Surra, caused by Trypanosoma evansi, is an economically important disease of a wide range of domestic and wild animals, and is most widely distributed. It is a potentially fatal disease causing huge economic losses to the livestock owners in terms of morbidity, mortality, abortion, infertility, reduced milk yield and also by interfering with vaccination programme in India. Due to sub clinical nature of the disease, it has been underestimated in cattle and buffaloes. Emergence of atypical cases of human trypanosomiasis has created an alarming situation and indicates a possible zoonotic threat in future. Accurate diagnosis of surra is extremely essential to identify animals for treatment, to assess the prevalence of the disease and to avoid indiscriminate usage of trypanocidal drugs. Diagnosis of surra still suffers from low sensitivity and specificity. There is an urgent need for sensitive cost effective penside diagnostic that can be applicable and affordable to smallholder farmers in endemic regions. The present review addresses various aspects of surra with special emphasis on disease epidemiology, emerging issues, current diagnostic trends, chemotherapeutics and preventive measures to limits its prevalence in livestock.

Molecular Cloning, Expression and Characterization of Para Flagellar Rod Protein 1 of Trypanosoma evansi

BACKGROUND

Antigenic variation allows the trypanosomes to evade the potentially destructive host immune response and is an important reason for failure to develop a protective vaccine. Among the non-variant structural proteins, paraflagellar rod protein (PFR) is a prospective vaccine target owing to its role in the active movement of the parasite.

METHODS

The PFR1 gene was cloned in pET-32a expression vector and after confirmation by restriction digestion, expressed as a Histidine-tagged fusion protein, in BL21 DE3 strain of E. coli. The expressed protein was affinity purified and then renatured. The immunoreactivity of the expressed recombinant protein was shown by western blot analysis using the specific serum. The experiment was carried out during 2013-14 at Division of Parasitology, Indian Veterinary Research Institute, Izatnagar, U.P., India.

RESULTS

The results of sequencing, restriction digestion analysis, and PCR reaction revealed that cloning of PFR1 gene in pET-32a expression vector and the results of SDS PAGE and Western blot further confirmed its homogeneity and purity. The in silico Te-PFR1 (T. evansi PFR1) nucleotides sequence analysis revealed its close homology with the other members of the order Kinetoplastida.

CONCLUSION

We report here the molecular cloning, heterologous expression, and characterization of PFR1, a constituent protein of PFR. Due to its conserved nature, the PFR1 protein could be a prospective vaccine target against multiple Trypanosoma species.

Prevalence and risk assessment of gastrointestinal helminthoses in dairy animals of Bikaner, Rajasthan

A total of 715 faecal sampleswere collected fromdairy animals ofeight tehsils ofBikaner district, Rajasthan during March 2015 to January 2016. An overall prevalence rate of 54.12 % was recorded for gastrointestinal helminthoses with highly statistical difference among dairy animals (p < 0.01). Quantitative analysis revealed mild to high severity of strongyle and Strongyloides sp. infections in cattle population, respectively whereas, mild severities of same infections were reported from the buffalo population of the region. Seasonal analysis revealed a non-significant difference with highest prevalence in rainy season (59.18 %). The tehsil wise analysis revealed a significant difference (p < 0.05) among tehsils with highest prevalence in Chhatargarh (69.70 %). Multivariate binary regression model revealed rainy season as the most favorable season and Chattargarh as the tehsil with maximum risk for GI helminth infections.On coproculture of positive samples, the nematode infections in decreasing order of prevalence were Haemonchus sp. (36.33 %); Oesophagostomum sp. (26.33 %); Strongyloides sp. (13.67 %); Trichostrongylus sp. (11.67 %); Bunostomum sp. (7.33 %) and Cooperia sp. (4.67 %). Thebaseline data on the prevalence of various GI Helminths of dairy animals generated in the current study would be of immense help in formulating control strategies against infections inBikaner district.

Important hemoprotozoan diseases of livestock: Challenges in current diagnostics and therapeutics: An update

Hemoprotozoan parasites pose a serious threat to the livestock population in terms of mortality, reduced milk yield and lowered draft power. Diagnosis of these diseases often poses a challenging task. Needless to say that impact of disease in health and productivity is huge though a fair economic assessment on the quantum of economic loss associated is yet to be worked out from India. The diagnosis of hemoprotozoan infections largely depends on various laboratory-based diagnostic methods as the clinical manifestations are often inconspicuous and non-specific. Traditional diagnostic methods rely on microscopical demonstration of infective stages in blood or tissue fluids. However, it is laborious, lesser sensitive, and cannot differentiate between morphologically similar organisms. Recent development in the technologies has opened new avenues for improvement in the accurate diagnosis of parasitic infections. Serological tests are simple, fast but lack specificity. With advent of molecular techniques, as DNA hybridization assays, polymerase chain reaction and its modifications ensure the detection of infection in the latent phase of the disease. Nucleic acid-based assays are highly sensitive, free from immunocompetence and can differentiate between morphologically similar parasites. With the advent of newer diagnostics complemented with traditional ones will be of huge help for targeted selective treatment with better chemotherapeutic agents.