BQP35 is a novel member of the intrinsically unstructured protein (IUP) family which is a potential antigen for the sero-diagnosis of Babesia sp. BQ1 (Lintan) infection

Comparative genomics reveals unique features of two Babesia motasi subspecies: Babesia motasi lintanensis and Babesia motasi hebeiensis

Parasites of the Babesia genus are prevalent worldwide and infect a wide diversity of domestic animals and humans. Herein, using Oxford Nanopore Technology and Illumina sequencing technologies, we sequenced two Babesia sub-species, Babesia motasi lintanensis and Babesia motasi hebeiensis. We identified 3,815 one-to-one ortholog genes that are specific to ovine Babesia spp. Phylogenetic analysis reveals that the two B. motasi subspecies form a distinct clade from other Piroplasma spp. Consistent with their phylogenetic position, comparative genomic analysis reveals that these two ovine Babesia spp. share higher colinearity with Babesia bovis than with Babesia microti. Concerning the speciation date, B. m. lintanensis split from B. m. hebeiensis approximately 17 million years ago. Genes correlated to transcription, translation, protein modification and degradation, as well as differential/specialized gene family expansions in these two subspecies may favor adaptation to vertebrate and tick hosts. The close relationship between B. m. lintanensis and B. m. hebeiensis is underlined by a high degree of genomic synteny. Compositions of most invasion, virulence, development, and gene transcript regulation-related multigene families, including spherical body protein, variant erythrocyte surface antigen, glycosylphosphatidylinositol anchored proteins, and transcription factor Apetala 2 genes, is largely conserved, but in contrast to this conserved situation, we observe major differences in species-specific genes that may be involved in multiple functions in parasite biology. For the first time in Babesia spp., we find abundant fragments of long terminal repeat-retrotransposons in these two species. We provide fundamental information to characterize the genomes of B. m. lintanensis and B. m. hebeiensis, providing insights into the evolution of B. motasi group parasites.

Comparative genomic analysis of Babesia duncani responsible for human babesiosis

Background

Human babesiosis, caused by parasites of the genus Babesia, is an emerging and re-emerging tick-borne disease that is mainly transmitted by tick bites and infected blood transfusion. Babesia duncani has caused majority of human babesiosis in Canada; however, limited data are available to correlate its genomic information and biological features.

Results

We generated a B. duncani reference genome using Oxford Nanopore Technology (ONT) and Illumina sequencing technology and uncovered its biological features and phylogenetic relationship with other Apicomplexa parasites. Phylogenetic analyses revealed that B. duncani form a clade distinct from B. microti, Babesia spp. infective to bovine and ovine species, and Theileria spp. infective to bovines. We identified the largest species-specific gene family that could be applied as diagnostic markers for this pathogen. In addition, two gene families show signals of significant expansion and several genes that present signatures of positive selection in B. duncani, suggesting their possible roles in the capability of this parasite to infect humans or tick vectors.

Conclusions

Using ONT sequencing and Illumina sequencing technologies, we provide the first B. duncani reference genome and confirm that B. duncani forms a phylogenetically distinct clade from other Piroplasm parasites. Comparative genomic analyses show that two gene families are significantly expanded in B. duncani and may play important roles in host cell invasion and virulence of B. duncani. Our study provides basic information for further exploring B. duncani features, such as host-parasite and tick-parasite interactions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01361-9.

Systematic Comparison of the Performances of De Novo Genome Assemblers for Oxford Nanopore Technology Reads From Piroplasm

Background

Emerging long reads sequencing technology has greatly changed the landscape of whole-genome sequencing, enabling scientists to contribute to decoding the genetic information of non-model species. The sequences generated by PacBio or Oxford Nanopore Technology (ONT) be assembled de novo before further analyses. Some genome de novo assemblers have been developed to assemble long reads generated by ONT. The performance of these assemblers has not been completely investigated. However, genome assembly is still a challenging task.

Methods and Results

We systematically evaluated the performance of nine de novo assemblers for ONT on different coverage depth datasets. Several metrics were measured to determine the performance of these tools, including N50 length, sequence coverage, runtime, easy operation, accuracy of genome and genomic completeness in varying depths of coverage. Based on the results of our assessments, the performances of these tools are summarized as follows: 1) Coverage depth has a significant effect on genome quality; 2) The level of contiguity of the assembled genome varies dramatically among different de novo tools; 3) The correctness of an assembled genome is closely related to the completeness of the genome. More than 30× nanopore data can be assembled into a relatively complete genome, the quality of which is highly dependent on the polishing using next generation sequencing data.

Conclusion

Considering the results of our investigation, the advantage and disadvantage of each tool are summarized and guidelines of selecting assembly tools are provided under specific conditions.

Mitochondrial genomes of two Babesia taxa from sheep in China as a foundation for population genetic and epidemiological investigations

Here, we sequenced, assembled and annotated the mitochondrial (mt) genomes of two operational taxonomic units of Babesia from sheep from China using a deep sequencing-coupled approach. Then, we defined and compared the gene order of these mt genomes (~5.8 to 6.2kb in size), assessed sequence differences in mt genes among Babesia taxa and evaluated genetic relationships among these taxa and related apicomplexans (Theileria) for which mt genomic data sets were available. We also identified mt genetic regions that might be useful as markers for future population genetic and molecular epidemiological studies of Babesia from small ruminants. We propose that the sequencing-bioinformatic approach used here should be applicable to a wide range of protists of veterinary importance.

Genomic resources for a unique, low-virulence Babesia taxon from China

BACKGROUND

Babesiosis is a socioeconomically important tick-borne disease of animals (including humans) caused by haemoprotozoan parasites. The severity of babesiosis relates to host and parasite factors, particularly virulence/pathogenicity. Although Babesia bovis is a particularly pathogenic species of cattle, there are species of Babesia of ruminants that have limited pathogenicity. For instance, the operational taxonomic unit Babesia sp. Xinjiang (abbreviated here as Bx) of sheep from China is substantially less virulent/pathogenic than B. bovis is in cattle. Although the reason for this distinctiveness is presently unknown, it is possible that Bx has a reduced ability to adhere to cells or evade/suppress immune responses, which might relate to particular proteins, such as the variant erythrocyte surface antigens (VESAs).

RESULTS

We sequenced and annotated the 8.4 Mb nuclear draft genome of Bx and compared it with those of B. bovis and B. bigemina by synteny analysis; we also investigated the genetic relationship of Bx with selected Babesia species and related apicomplexans for which genomic datasets are available, and explored the VESA complement in Bx.

CONCLUSIONS

The availability of the Bx genome now provides unique opportunities to elucidate aspects of the molecular biology, biochemistry and physiology of Bx, and to explore the reason(s) for its limited virulence and/or apparent ability to evade immune attack by the host animal. Moreover, the present genomic resource and an in vitro culture system for Bx raises the prospect of establishing a functional genomic platform to explore essential genes as new intervention targets against babesiosis.

Expression of sheep pathogen Babesia sp. Xinjiang rhoptry-associated protein 1 and evaluation of its diagnostic potential by enzyme-linked immunosorbent assay

Ovine babesiosis is one of the most important tick-borne haemoparasitic diseases of small ruminants. The ovine parasite Babesia sp. Xinjiang is widespread in China. In this study, recombinant full-length XJrRAP-1aα2 (rhoptry-associated protein 1aα2) and C-terminal XJrRAP-1aα2 CT of Babesia sp. Xinjiang were expressed and used to evaluate their diagnostic potential for Babesia sp. Xinjiang infections by indirect enzyme-linked immunosorbent assay (ELISA). Purified XJrRAP-1aα2 was tested for reactivity with sera from animals experimentally infected with Babesia sp. Xinjiang and other haemoparasites using Western blotting and ELISA. The results showed no cross-reactivities between XJrRAP-1aα2 CT and sera from animals infected by other pathogens. High level of antibodies against RAP-1a usually lasted 10 weeks post-infection (wpi). A total of 3690 serum samples from small ruminants in 23 provinces located in 59 different regions of China were tested by ELISA. The results indicated that the average positive rate was 30·43%, and the infections were found in all of the investigated provinces. This is the first report on the expression and potential use of a recombinant XJrRAP-1aα2 CT antigen for the development of serological assays for the diagnosis of ovine babesiosis, caused by Babesia sp. Xinjiang.

Expression analysis and biological characterization of Babesia sp. BQ1 (Lintan) (Babesia motasi-like) rhoptry-associated protein 1 and its potential use in serodiagnosis via ELISA

Background

In China, ovine babesiosis is one of the most important tick-borne haemoparasitic diseases of small ruminants. It has a significant economic impact, and several Babesia motasi-like isolates have been recently shown to be responsible for ovine babesiosis in this country.

Methods

Full-length and C-terminal-truncated forms of the rap-1a61-1 gene of Babesia sp. BQ1 (Lintan) were cloned into the pET-30a plasmid and subsequently expressed as His-fusion proteins. The resulting recombinant RAP-1a proteins (rRAP-1a61-1 and rRAP-1a61-1/CT) were purified and evaluated as diagnostic antigens using Western blot analysis and ELISA. The native Babesia sp. BQ1 (Lintan) RAP-1 protein was recognized using Western blots and IFAT by antibodies that were raised in rabbits against rRAP-1a61-1/CT. The specificity, sensitivity and positive threshold values for rRAP-1a61-1/CT in ELISA were evaluated.

Results

Cross-reactivity was observed between rRAP-1a61-1/CT and positive sera for Babesia sp. BQ1 (Lintan), Babesia sp. BQ1 (Ningxian) and Babesia sp. Tianzhu isolates obtained from infected sheep. At one week post-inoculation, a significant increase was observed in the amount of antibodies produced against RAP-1a, and high levels of antibodies against RAP-1a were observed for 3 months (at 84 days p.i.). A total of 3198 serum samples were collected from small ruminants in 54 different regions in 23 provinces of China. These samples were tested using ELISA based on the rRAP-1a61-1/CT protein. The results indicated that the average positive rate was 36.02 %.

Conclusions

The present study suggests that rRAP-1a61-1/CT might be a potential diagnostic antigen for detecting several isolates of B. motasi-like parasites infection.

A member of the HSP90 family from ovine Babesia in China: molecular characterization, phylogenetic analysis and antigenicity

Heat shock protein 90 (HSP90) is a key component of the molecular chaperone complex essential for activating many signalling proteins involved in the development and progression of pathogenic cellular transformation. A Hsp90 gene (BQHsp90) was cloned and characterized from Babesia sp. BQ1 (Lintan), an ovine Babesia isolate belonging to Babesia motasi-like group, by screening a cDNA expression library and performing rapid amplification of cDNA ends. The full-length cDNA of BQHsp90 is 2399 bp with an open reading frame of 2154 bp encoding a predicted 83 kDa polypeptide with 717 amino acid residues. It shows significant homology and similar structural characteristics to Hsp90 of other apicomplex organisms. Phylogenetic analysis, based on the HSP90 amino acid sequences, showed that the Babesia genus is clearly separated from other apicomplexa genera. Five Chinese ovine Babesia isolates were divided into 2 phylogenetic clusters, namely Babesia sp. Xinjiang (previously designated a new species) cluster and B. motasi-like cluster which could be further divided into 2 subclusters (Babesia sp. BQ1 (Lintan)/Babesia sp. Tianzhu and Babesia sp. BQ1 (Ningxian)/Babesia sp. Hebei). Finally, the antigenicity of rBQHSP90 protein from prokaryotic expression was also evaluated using western blot and enzyme-linked immunosorbent assay (ELISA).

Cytochrome c oxidase subunit III (COX3) gene, an informative marker for phylogenetic analysis and differentiation of Babesia species in China

In this study a 552-bp region of the cytochrome c oxidase subunit III (COX3) was amplified by polymerase chain reaction (PCR) and sequenced from individual Babesia species. Sequence variation between Babesia species from China ranged between 0 and 32.4%. We analyzed the phylogenetic performance of the partial sequence of the COX3 gene to resolve Babesia relationships as compared to the nuclear 18S rRNA and the mitochondrial cytochrome b (COB) gene, These data indicate that the COX3 gene seems to be superior to the COB gene and the 18S rRNA in recognizing close lineages among some Babesia species. Our work indicates that the COX3 gene does complement and corroborate the phylogenetic inferences observed with the nuclear 18S rRNA and the COB gene previously reported. The combined phylogenetic analysis based on the nuclear 18S rRNA and the COX3 gene significantly improved (bootstrap) intraspecies support of the phylogenetic relationship. The presence of additional variable sites in the COX3 gene allowed an improved interspecies differentiation of Babesia species in this study. The data could be applicable for the survey of parasite dynamics, epidemiological studies as well as prevention and control of the disease.