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

Nicola Palmieri,Ivana Bilic,Michael Hess,Marcelo De Jesus Ramires

doi:10.1186/s12864-021-08059-2

Nicola Palmieri, Ivana Bilic + Show 2 more

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https://doi.org/10.1186/s12864-021-08059-2

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Abstract

BackgroundHistomonas 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.ResultsWhole 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.ConclusionsTaken 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.

Highlights

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
In order to achieve megabase-sized contigs with high base-level accuracy, the genomes of both strains were assembled using a combination of Oxford Nanopore Technology (ONT) long reads and Illumina short reads
As leucine-rich repeat (LRR) proteins of the BspA family are involved in virulence in trichomonads [22], we looked at the presence of BspA motifs in this protein with the online tool MOTIF and identified a single BspA motif at positions 38 ➔ 88 (Fig. 3c)

Summary

Introduction

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. Histomonas meleagridis is a flagellated extracellular poultry parasite of the order Tritrichomonadida [1]. The disease can be very devastating in turkeys, in which the parasite causes serious ceacal lesions and liver necrosis that can lead up to 100% mortality [3]. Histomonosis and the parasite are known for more than 100 years, which in the second half of the twentieth century led to the introduction of effective prophylactic and chemotherapeutic drugs with the almost disappearance of the disease [5].

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