Transcriptome of Sphaerospora molnari (Cnidaria, Myxosporea) blood stages provides proteolytic arsenal as potential therapeutic targets against sphaerosporosis in common carp

Abstract

Background: Parasites employ proteases to evade host immune systems, feed and replicate and are often the target of anti-parasite strategies to disrupt these interactions. Myxozoans are obligate cnidarian parasites, alternating between invertebrate and fish hosts. Their genes are highly divergent from other metazoans, and available genomic and transcriptomic datasets are limited. Some myxozoans are important aquaculture pathogens such as Sphaerospora molnari replicating in the blood of farmed carp before reaching the gills for sporogenesis and transmission. Proliferative stages cause a massive systemic lymphocyte response and the disruption of the gill epithelia by spore-forming stages leads to respiratory problems and mortalities. In the absence of a S. molnari genome, we utilized a de novo approach to assemble the first transcriptome of proliferative myxozoan stages to identify S. molnari proteases that are upregulated during the first stages of infection when the parasite multiplies massively, rather than in late spore-forming plasmodia. Furthermore, a subset of orthologs was used to characterize 3D structures and putative druggable targets. Results: An assembled and host filtered transcriptome containing 9436 proteins, mapping to 29,560 contigs was mined for protease virulence factors and revealed that cysteine proteases were most common (38%), at a higher percentage than other myxozoans or cnidarians (25-30%). Two cathepsin Ls that were found upregulated in spore-forming stages with a presenilin like aspartic protease and a dipeptidyl peptidase. We also identified downregulated proteases in the spore-forming development when compared with proliferative stages including an astacin metallopeptidase and lipases (qPCR). In total, 235 transcripts were identified as putative proteases using a MEROPS database. In silico analysis of highly transcribed cathepsins revealed potential drug targets within this data set that should be prioritised for development.

Transcriptome-Wide Comparisons and Virulence Gene Polymorphisms of Host-Associated Genotypes of the Cnidarian Parasite Ceratonova shasta in Salmonids

“…2005 ), and this appears similar in myxozoans: ∼2.5% (422 proteins) in the Thelohanellus kitauei proteome ( Yang et al. 2014 ) and 2.6% of expressed genes in Sphaerospora molnari ( Hartigan et al 2020 ). Our relative frequency analyses showed that these genes are generally less conserved/more variable in C. shasta than cell migration genes.…”

Genetic Diversity of Serine Protease Inhibitors in Myxozoan (Cnidaria, Myxozoa) Fish Parasites

“…PRJNA241036) [ 32 ]; Sphaerospora molnari (BioProject No. PRJNA522909) [ 33 ]; Thelohanellus kitauei (BioProject No. PRJNA193083) [ 27 ]; Enteromyxum leei (BioProject No.…”

Transcriptome Analysis Elucidates the Key Responses of Bryozoan Fredericella sultana during the Development of Tetracapsuloides bryosalmonae (Myxozoa)

“…The upregulation of protease inhibitors may reflect a finely adapted innate immune defense system in bryozoans that is capable of monitoring self- and parasite-derived proteases and that may inactivate and eliminate the proteases involved in parasite invasion [ 29 , 30 ]. Proteases of myxozoans have been described as major virulence factors and are assumed to support the invasion of parasites into their hosts [ 31 , 32 , 33 , 34 ]. Similarly, proteases have been identified in T. bryosalmonae using RNA-seq analysis (authors own unpublished data).…”