Identification and Expression Profiling of Toll-Like Receptors of Brown Trout (Salmo trutta) during Proliferative Kidney Disease

Abstract

Proliferative kidney disease is an emerging disease among salmonids in Europe and North America caused by the myxozoan parasite Tetracapsuloides bryosalmonae. The decline of endemic brown trout (Salmo trutta) in the Alpine streams of Europe is fostered by T. bryosalmonae infection. Toll-like receptors (TLRs) are a family of pattern recognition receptors that acts as sentinels of the immune system against the invading pathogens. However, little is known about the TLRs’ response in salmonids against the myxozoan infection. In the present study, we identified and evaluated TLR1, TLR19, and TLR13-like genes of brown trout using data-mining and phylogenetic analysis. The expression pattern of TLRs was examined in the posterior kidney of brown trout infected with T. bryosalmonae at various time points. Typical Toll/interleukin-1 receptor protein domain was found in all tested TLRs. However, TLR13-like chr2 had a short amino acid sequence with no LRR domain. Phylogenetic analysis illustrated that TLR orthologs are conserved across vertebrates. Similarly, a conserved synteny gene block arrangement was observed in the case of TLR1 and TLR19 across fish species. Interestingly, all tested TLRs showed their maximal relative expression from 6 to 10 weeks post-exposure to the parasite. Our results suggest that these TLRs may play an important role in the innate defense mechanism of brown trout against the invading T. bryosalmonae.

Dietary Chitosan Nanoparticles: Potential Role in Modulation of Rainbow Trout (Oncorhynchus mykiss) Antibacterial Defense and Intestinal Immunity against Enteric Redmouth Disease

“…RNeasy Mini Kit (Qiagen, Hilden, Germany) was used for the total RNA extraction with including an on-column DNase I digestion step (Qiagen, Hilden, Germany). The extracted RNA was qualified and quantified on a NanoDrop 2000 spectrophotometer (Thermo Fisher Scientific, Vienna, Austria), and the cDNA was synthesized from 1 µg mRNA input according to the user’s manual by using of iScript cDNA synthesis kit (Bio-Rad, Hercules, Munich, Germany) [ 85 ]. Duplicate template and transcriptase controls were included to assess the performance of the qRT-PCR assay for each gene.…”

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

“…Lysosome, peroxisome, and oxidative phosphorylation pathways genes like cathepsin B, lysosomal alpha-mannosidase, peroxiredoxin-5, superoxide dismutases (Fe and Cu-Zn), cytochrome c oxidase subunit V, and NADH dehydrogenase (ubiquinone) iron-sulfur proteins (2, 3, and 7) were upregulated in the infected zooids. Similarly, the upregulation of TLR13-like, cathepsin B, peroxiredoxin, and cytochrome c oxidase subunit 5B was observed in the kidney of brown trout in response to T. bryosalmonae [ 22 , 23 ]. The upregulation of phagosome and antioxidative pathways was also demonstrated in oligochaete worms in response to the myxozoan parasite B. sowerbyi [ 18 ].…”

“…In support of this, we found upregulation of Toll signaling pathway genes such as TLR3 (2.59 fold), TLR4 (2.53 fold), and TLR13 (2.55 fold) in the infected zooids. Additionally, upregulation of TLRs such as TLR1 (4.1 fold), TLR13-like Chr1 (16.3 fold), and TLR19 (5.5 fold) has been reported in the kidney of brown trout during active T. bryosalmonae sporogenesis [ 23 ]. We presume that proteases are involved in numerous important processes in bryozoans and thereby play a role in the innate immune system in bryozoans during parasite infection.…”

Development of Fish Parasite Vaccines in the OMICs Era: Progress and Opportunities

“…TLRs are type-I transmembrane receptors that recognize pathogen-associated molecular patterns to initiate an immune response [ 51 ]. Several TLRs play important roles in the defense of different fish hosts, against various parasites e.g., T. bryosalmonae [ 52 ], I. multifiliis [ 53 ], C. irritans [ 54 ], and C. rogercresseyi [ 55 ]. TLR1, TLR2, TLR9, TLR19, TLR21, and TLR25 reportedly play an important role in immunity in fish against I. multifiliis [ 53 ].…”

“…However, the concerned parasite epitopes that they recognize are unexplored currently for the majority of TLRs. For example, TLR1, TLR13, and TLR19 are significantly upregulated in the kidney of brown trout during PKD [ 52 ], but the moiety of T. bryosalmonae , which might be responsible for their activation is unknown. TLR2 on human NK cells are activated by lipophosphoglycan component in the hemoflagellate parasite Leishmania major , a phosphoglycan belonging to a family of unique Leishmania glycoconjugates [ 56 ].…”