Unravelling the differences: comparative proteomic analysis of a clonal virulent and an attenuated Histomonas meleagridis strain

Identification and Characterization of α-Actinin 1 of Histomonas meleagridis and Its Potential Vaccine Candidates against Histomonosis

Histomonas meleagridis is a protozoan parasite that causes histomonosis in gallinaceous birds such as turkeys and chickens. Since the banning and restricted usage of effective drugs such as nitarsone, 80-100% morbidity and mortality occur in turkeys and 20-30% mortality in chickens. New ideas are needed to resolve the re-emergence of histomonosis in poultry. In this study, the α-actinin encoding gene from H. meleagridis was cloned. The 1839-bp gene encoding 612 amnio acids showed close phylogenetic relationships with Trichomonas vaginalis and Tritrichomonas foetus. It was then inserted into the prokaryotic expression vector pET28a(+) and induced with isopropyl-β-D-thiogalactopyranoside. A 73 kDa recombinant protein rHmα-actinin 1 was obtained and purified with a Ni-NTA chromatography column. rHmα-actinin 1 was recognized by mouse anti-rHmα-actinin 1 polyclonal antibody, mouse anti-rHmα-actinin 1 monoclonal antibody, and rehabilitation sera from H. meleagridis infected chickens. Native α-actinin 1 in the total proteins of H. meleagridis can also be detected with mouse anti-rHmα-actinin monoclonal antibody. Immunolocalization assays showed that Hmα-actinin 1 was mainly distributed in the cytoplasm of virulent histomonads JSYZ-D9 and in the peripheral regions (near the plasma membrane) of attenuated histomonads JSYZ-D195. Based on in vivo experiment, when chickens were subcutaneously immunized with rHmα-actinin 1 at 5 and 12 days old and then challenged with H. meleagridis at 19 days old, rHmα-actinin 1 reduced the lesion scores 12 days after infection (31 days old) and increased the body weight gain during the challenged period (19-31 days old). Furthermore, it also strengthened the cellular and humoral immune responses 7 days after the second immunization (19 days old). In conclusion, Hmα-actinin 1 could be used as a candidate antigen to develop vaccines against chicken histomonosis.

Tandem mass tag-based quantitative proteomics analyses of a chicken-original virulent and its attenuated Histomonas meleagridis strain in China

Introduction

Histomonas meleagridis can cause histomonosis in poultry. Due to the prohibition of effective drugs, the prevention and treatment of the disease requires new strategies. Questions about its pathogenic mechanisms and virulence factors remain puzzling.

Methods

To address these issues, a tandem mass tag (TMT) comparative proteomic analysis of a virulent strain and its attenuated strain of Chinese chicken-origin was performed.

Results

A total of 3,494 proteins were identified in the experiment, of which 745 proteins were differentially expressed (fold change ≥1.2 or ≤0.83 and p < 0.05), with 192 up-regulated proteins and 553 down-regulated proteins in the virulent strain relative to the attenuated strain.

Discussion

Surface protein BspA like, digestive cysteine proteinase, actin, and GH family 25 lysozyme were noted among the proteins up regulated in virulent strains, and these several proteins may be directly related to the pathogenic capacity of the histomonad. Ferredoxin, 60S ribosomal protein L6, 40S ribosomal protein S3, and NADP-dependent malic enzyme which associated with biosynthesis and metabolism were also noted, which have the potential to be new drug targets. The up-regulation of alpha-amylase, ras-like protein 1, ras-like protein 2, and involucrin in attenuated strains helps to understand how it is adapted to the long-term in vitro culture environment. The above results provide some candidate protein-coding genes for further functional verification, which will help to understand the molecular mechanism of pathogenicity and attenuation of H. meleagridis more comprehensively.

Comparative Surfaceome Analysis of Clonal Histomonas meleagridis Strains with Different Pathogenicity Reveals Strain-Dependent Profiles

Histomonas meleagridis, a poultry-specific intestinal protozoan parasite, is histomonosis’s etiological agent. Since treatment or prophylaxis options are no longer available in various countries, histomonosis can lead to significant production losses in chickens and mortality in turkeys. The surfaceome of microbial pathogens is a crucial component of host–pathogen interactions. Recent proteome and exoproteome studies on H. meleagridis produced molecular data associated with virulence and in vitro attenuation, yet the information on proteins exposed on the cell surface is currently unknown. Thus, in the present study, we identified 1485 proteins and quantified 22 and 45 upregulated proteins in the virulent and attenuated strains, respectively, by applying cell surface biotinylation in association with high-throughput proteomic analysis. The virulent strain displayed upregulated proteins that could be linked to putative virulence factors involved in the colonization and establishment of infection, with the upregulation of two candidates being confirmed by expression analysis. In the attenuated strain, structural, transport and energy production proteins were upregulated, supporting the protozoan’s adaptation to the in vitro environment. These results provide a better understanding of the surface molecules involved in the pathogenesis of histomonosis, while highlighting the pathogen’s in vitro adaptation processes.

Histomonosis in Poultry: A Comprehensive Review

Histomonas meleagridis, the etiological agent of histomonosis, is a poultry parasite primarily detrimental to turkeys. Characteristic lesions occur in the liver and ceca, with mortalities in turkey flocks often reaching 80-100%. Chickens and other gallinaceous birds can be susceptible but the disease was primarily considered sub-clinical until recent years. Treating and preventing H. meleagridis infection have become more difficult since 2015, when nitarsone was voluntarily removed from the market, leaving the poultry industry with no approved prophylactics, therapeutics, or vaccines to combat histomonosis. Phytogenic compounds evaluated for chemoprophylaxis of histomonosis have varied results with in vitro and in vivo experiments. Some recent research successes are encouraging for the pursuit of antihistomonal compounds derived from plants. Turkeys and chickens exhibit a level of resistance to re-infection when recovered from H. meleagridis infection, but no commercial vaccines are yet available, despite experimental successes. Safety and stability of live-attenuated isolates have been demonstrated; furthermore, highly efficacious protection has been conferred in experimental settings with administration of these isolates without harming performance. Taken together, these research advancements are encouraging for vaccine development, but further investigation is necessary to evaluate proper administration age, dose, and route. A summary of the published research is provided in this review.

Complete genomes of the eukaryotic poultry parasite Histomonas meleagridis: linking sequence analysis with virulence / attenuation

Background

Histomonas meleagridis is a protozoan parasite and the causative agent of histomonosis, an important poultry disease whose significance is underlined by the absence of any treatment and prophylaxis. The recent successful in vitro attenuation of the parasite urges questions about the underlying mechanisms.

Results

Whole genome sequence data from a virulent and an attenuated strain originating from the same parental lineage of H. meleagridis were recruited using Oxford Nanopore Technology (ONT) and Illumina platforms, which were combined to generate megabase-sized contigs with high base-level accuracy. Inspecting the genomes for differences identified two substantial deletions within a coding sequence of the attenuated strain. Additionally, one single nucleotide polymorphism (SNP) and indel targeting coding sequences caused the formation of premature stop codons, which resulted in the truncation of two genes in the attenuated strain. Furthermore, the genome of H. meleagridis was used for characterizing protein classes of clinical relevance for parasitic protists. The comparative analysis with the genomes of Trichomonas vaginalis, Tritrichomonas foetus and Entamoeba histolytica identified ~ 2700 lineage-specific gene losses and 9 gene family expansions in the H. meleagridis lineage.

Conclusions

Taken as a whole, the obtained data provide the first hints to understand the molecular basis of attenuation in H. meleagridis and constitute a genomics platform for future research on this important poultry pathogen.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08059-2.

Interplay between Histomonas meleagridis and Bacteria: Mutualistic or Predator-Prey?

Histomonas meleagridis is an extracellular protozoan parasite and the aetiological agent of histomonosis, an important poultry disease whose impact is greatly accentuated by inaccessibility of any treatment. A special feature of the parasite is its intricate interplay with bacteria in vitro and in vivo, the focus of this article.

Molecular characterization of Histomonas meleagridis exoproteome with emphasis on protease secretion and parasite-bacteria interaction

The exoproteome of parasitic protists constitutes extracellular proteins that play a fundamental role in host-parasite interactions. Lytic factors, especially secreted proteases, are capable of modulating tissue invasion, thereby aggravating host susceptibility. Despite the important role of exoproteins during infection, the exoproteomic data on Histomonas meleagridis are non-existent. The present study employed traditional 1D-in-gel-zymography (1D-IGZ) and micro-LC-ESI-MS/MS (shotgun proteomics), to investigate H. meleagridis exoproteomes, obtained from a clonal virulent and an attenuated strain. Both strains were maintained as mono-eukaryotic monoxenic cultures with Escherichia coli. We demonstrated active in vitro secretion kinetics of proteases by both parasite strains, with a widespread proteolytic activity ranging from 17 kDa to 120 kDa. Based on protease inhibitor susceptibility assay, the majority of proteases present in both exoproteomes belonged to the family of cysteine proteases and showed stronger activity in the exoproteome of a virulent H. meleagridis. Shotgun proteomics, aided by customized database search, identified 176 proteins including actin, potential moonlighting glycolytic enzymes, lytic molecules such as pore-forming proteins (PFPs) and proteases like cathepsin-L like cysteine protease. To quantify the exoproteomic differences between the virulent and the attenuated H. meleagridis cultures, a sequential window acquisition of all theoretical spectra mass spectrometric (SWATH-MS) approach was applied. Surprisingly, results showed most of the exoproteomic differences to be of bacterial origin, especially targeting metabolism and locomotion. By deciphering such molecular signatures, novel insights into a complex in vitro protozoan- bacteria relationship were elucidated.

An Alliance of Gel-Based and Gel-Free Proteomic Techniques Displays Substantial Insight Into the Proteome of a Virulent and an Attenuated Histomonas meleagridis Strain

The unicellular protozoan Histomonas meleagridis is notorious for being the causative agent of histomonosis, which can cause high mortality in turkeys and substantial production losses in chickens. The complete absence of commercially available curative strategies against the disease renders the devising of novel approaches a necessity. A fundamental step toward this objective is to understand the flagellate's virulence and attenuation mechanisms. For this purpose we have previously conducted a comparative proteomic analysis of an in vitro cultivated virulent and attenuated histomonad parasite using two-dimensional electrophoresis and MALDI-TOF/TOF. The current work aimed to substantially extend the knowledge of the flagellate's proteome by applying 2D-DIGE and sequential window acquisition of all theoretical mass spectra (SWATH) MS as tools on the two well-defined strains. In the gel-based experiments, 49 identified protein spots were found to be differentially expressed, of which 37 belonged to the in vitro cultivated virulent strain and 12 to the attenuated one. The most frequently identified proteins in the virulent strain take part in cytoskeleton formation, carbohydrate metabolism and adaptation to stress. However, post-translationally modified or truncated ubiquitous cellular proteins such as actin and GAPDH were identified as upregulated in multiple gel positions. This indicated their contribution to processes not related to cytoskeleton and carbohydrate metabolism, such as fibronectin or plasminogen binding. Proteins involved in cell division and cytoskeleton organization were frequently observed in the attenuated strain. The findings of the gel-based studies were supplemented by the gel-free SWATH MS analysis, which identified and quantified 42 significantly differentially regulated proteins. In this case proteins with peptidase activity, metabolic proteins and actin-regulating proteins were the most frequent findings in the virulent strain, while proteins involved in hydrogenosomal carbohydrate metabolism dominated the results in the attenuated one.

Unravelling the Immunity of Poultry Against the Extracellular Protozoan Parasite Histomonas meleagridis Is a Cornerstone for Vaccine Development: A Review

The protozoan parasite Histomonas meleagridis is the causative agent of histomonosis in gallinaceous birds, predominantly in turkeys and chickens. Depending on the host species the outcome of the disease can be very severe with high mortality as observed in turkeys, whereas in chickens the mortality rates are generally lower. The disease is known for more than 100 years when in vitro and in vivo investigations started to understand histomonosis and the causative pathogen. For decades histomonosis could be well-controlled by effective drugs for prevention and therapy until the withdrawal of such chemicals for reasons of consumer protection in Europe, the USA and additional countries worldwide. Consequently, research efforts also focused to find new strategies against the disease, resulting in the development of an efficacious live-attenuated vaccine. In addition to efficacy and safety several studies were performed to obtain a deeper understanding of the immune response of the host against H. meleagridis. It could be demonstrated that antibodies accumulate in different parts of the intestine of chickens following infection with H. meleagridis which was much pronounced in the ceca. Furthermore, expression profiles of various cytokines revealed that chickens mounted an effective cecal innate immune response during histomonosis compared to turkeys. Studying the cellular immune response following infection and/or vaccination of host birds showed a limitation of pronounced changes of B cells and T-cell subsets in vaccinated birds in comparison to non-protected birds. Additionally, numbers of lymphocytes including cytotoxic T cells increased in the ceca of diseased turkeys compared to infected chickens suggesting an immunopathological impact on disease pathogenesis. The identification of type 1 and type 2 T-helper (Th) cells in infected and lymphoid organs by in situ hybridization did not show a clear separation of Th cells during infection but revealed a coherence of an increase of interferon (IFN)-γ mRNA positive cells in ceca and protection. The present review not only summarizes the research performed on the immune response of host birds in the course of histomonosis but also highlights the specific features of H. meleagridis as a model organism to study immunological principles of an extracellular organism in birds.