Transcriptional profiles of Rel/NF-κB, inhibitor of NF-κB (IκB), and lipopolysaccharide-induced TNF-α factor (LITAF) in the lipopolysaccharide (LPS) and two Vibrio sp.-exposed intertidal copepod, Tigriopus japonicus

An LPS-induced TNF-α factor involved in immune response of oyster Crassostrea gigas by regulating haemocytes apoptosis

LPS induced TNF-α Factor (LITAF) is a transcription factor widely involving in activation of Tumor Necrosis Factor (TNF) and other cytokines in the inflammatory response. In the present study, a homologue of LITAF with a conserved LITAF domain was identified from the Pacific oyster Crassostrea gigas. The transcripts of CgLITAF were detected in all examined tissues with highest expression in hepatopancrease. The immunofluorescence assay and Western blot showed that LPS stimulation induced an obvious nucleus translocation of CgLITAF protein in haemocytes. While the mRNA level of CgLITAF changed slightly after LPS stimulation. When the siRNA of CgLITAF was injected to inhibit its expression, the apoptotic level of haemocytes decreased observably after LPS stimulation. Consistently, the transcripts of CgTNF3 and CgTNF4 (LOC105343080, LOC105341146), the apoptotic-related molecules including CgBax, CgCytochrome c, CgCaspase9 and CgCaspase3, were significantly suppressed in the CgLITAF-RNAi oysters. While the mRNA expression level of CgBcl was enhanced significantly in the CgLITAF-RNAi oysters. These results indicated that CgLITAF promoted haemocyte apoptosis by regulating the expression of apoptotic-related factors, suggesting its important role in the immune response of oysters.

RNA-seq transcriptome analysis and identification of the theromacin antimicrobial peptide of the copepod Apocyclops royi

Copepods, including Apocyclops royi, are small aquatic crustaceans and one of the important foods for fish and shellfish larvae. However, studies of the host-pathogen interactions and understanding of infectious disease in copepods are still very limited, yet they are likely to be a significant factor in the sustainable development of copepod aquaculture. In the present study, we performed de novo RNA sequence analysis of A. royi-TH (a Thai isolate of A. royi), which yielded 4.80 Gb bases of clean data and a total of 29,786 unigenes. Annotation was then performed by comparison against seven functional databases, yielding 17,617 (NR: 59.15%), 2,969 (NT: 9.97%), 15,023 (SwissProt: 50.44%), 14,543 (KOG: 48.82%), 15,077 (KEGG: 50.62%), 6,763(GO: 22.71%), and 15,841 (InterPro: 53.18%) unigenes. In comparison to the components of the shrimp Toll pathway, LGBP, Spätzle, Toll receptors, MyD88, Pelle, TRAF6, Dorsal, and Cactus homologs were successfully identified in A. royi-TH. Additionally, a novel antimicrobial peptide (Theromacin-like) was characterized in A. royi (ArTM-like). The ArTM-like ORF was 279 bp and predicted to encode for 92 amino acid residues, with a mature peptide of 75 amino acids and a molecular mass of 8.56 kDa. The genomic organization of the ArTM-like gene consisted of three exons and two introns. Expression analysis indicated that ArTM-like mRNA was abundantly expressed in copepodid and adult stages as an immune responsive gene after infection with the pathogenic Vibrio parahaemolyticus-(AHPND)-causing strain. Altogether, the knowledge obtained in this study will provide a basis for future functional studies of the molecular mechanisms in copepod immunity that may eventually be applied for disease prevention in copepod aquaculture.

Two NF-κB subunits are associated with antimicrobial immunity in Hyriopsis cumingii

The NF-κB pathway activated by bacteria and viruses produces a series of antimicrobial peptides that participate in the innate immune response. In this study, two NF-κB subunits were cloned and identified from Hyriopsis cumingii (named Hcp65 and Hcp105) using RT-PCR and RACE. The predicted Hcp65 protein possessed a N-terminal Rel homology domain (RHD) and an Ig-like/plexins/transcription factors domain (IPT); the Hcp105 contained an RHD, an IPT domain, 6 ankyrin (ANK) domain and a death domain. Quantitative reverse transcription PCR (qRT-PCR) showed that Hcp65 and Hcp105 were constitutively expressed in the detected tissues, and were significantly up-regulated in hemocytes, hepatopancreas and gill of mussels challenged with lipopolysaccharide (LPS), peptidoglycan (PGN) and polyinosinic-polycytidylic acid (poly I: C). The dsRNA-mediated silencing of Hcp65 and Hcp105 caused significant reduction of immune genes such as lysozyme (HcLyso), theromacin (Hcther), whey acid protein (HcWAP), LPS-binding protein/bactericidal permeability protein (HcLBP/BPI) 1 and 2. In addition, subcellular localization experiments showed that Hcp65 and Hcp105 proteins were expressed in both the nucleus and cytoplasm of HEK-293T cells, and Hcp50 proteins (mature peptide of Hcp105) were mainly localized in the nucleus. The recombinant Hcp65 and Hcp50 protein could form homodimer and heterodimer and bind κB site in vitro. These results provide useful information for understanding the role of NF-κB in mollusks.

Toll-like receptor-9 is involved in the development of B cell stimulating factor-induced systemic lupus erythematosus

The objective of the present study was to investigate the role of Toll-like receptor (TLR)-9 in B lymphocyte stimulating factor (BLyS)-induced systemic lupus erythematosus (SLE) in mice. The anti-double stranded (ds)DNA antibody titer, levels of complement proteins (C3 and C4), interleukin (IL)-10 and the disease activity [assessed by the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level] were measured. A total of 21 transgenic female mice (aged 8-10 weeks and weighing 30-40 g) expressing the Epstein-Barr virus membrane antigen, BLLF1, were studied. Mice were randomly divided into the control, the BLyS inhibition and the TLR-9 inhibition groups, with 7 mice in each group. Mice in the blank control group received intraperitoneal injections of normal saline, mice in the BLyS inhibition group received intraperitoneal injections of anti-BR3 monoclonal antibody (5,000 ng/day) and mice in the TLR-9 inhibition group received intraperitoneal injections of anti-human TLR-9 antibody (250 ng/day). The treatment regimens continued for 10 days, followed by the collection of peripheral venous blood. The relative levels of TLR-9 mRNA were measured by reverse transcription-quantitative polymerase chain reaction. Furthermore, the BLyS protein concentration and IL-10 levels were measured by ELISA. TLR-9 mRNA, BLyS, IL-10, anti-dsDNA antibody titer, C3, C4, ESR and CRP levels of the blank control group were significantly higher than those of the other two groups (P<0.05). The differences in comparison of these indexes between the BLyS inhibition and TLR-9 inhibition groups were not statistically significant (P>0.05), with the exception of TLR-9 mRNA and BLyS. In conclusion, the TLR-9 signaling pathway may be important for BLyS-induced SLE, and regulation of the inflammatory immune level.

Genome-wide identification and transcript profile of the whole cathepsin superfamily in the intertidal copepod Tigriopus japonicus

Modulation of expression of cathepsins in innate immune response has previously been reported in mollusks and large crustaceans including crabs, lobsters, and shrimps in response to immune challenges. However, similar responses in copepods and the related cathepsin members remain under-investigated. To understand molecular and innate immune responses in the intertidal copepod Tigriopus japonicus, we identified the full spectra of cathepsin members (2 aspartyl proteases, 18 cysteine proteases, and 4 serine proteases) and also analyzed transcriptional expression of cathepsin (Tj-cathepsin) genes in developmental stages, lipopolysaccharide (LPS)- and two Vibrio species-exposed T. japonicus. The transcriptional levels of most Tj-cathepsin genes were highly increased during the molting transition from the nauplius to the copepodid stages. LPS treatment induced innate immune response via significant transcriptional increase of serine cathepsin (e.g., cathepsin As) members with induction of several cysteine cathepsin genes. However, Tj-aspartyl cathepsin E-like and a novel cysteine cathepsin were slightly reduced in response to LPS exposure. Interestingly, Vibrio species showed very low transcriptional sensitivity in the expression of entire cathepsins, while LPS induced several cathepsin gene-involved primitive immune responses in T. japonicus. In this paper, we discuss how whole cathepsin expression profiling can be linked to host defense mechanism to better understand and uncover the underlying mechanism of copepods' innate immunity.

Identification and molecular characterization of dorsal and dorsal-like genes in the cyclopoid copepod Paracyclopina nana

To date, knowledge of the immune system in aquatic invertebrates has been reported in only a few model organisms, even though all metazoans have an innate immune system. In particular, information on the copepod's immunity and the potential role of key genes in the innate immune systems is still unclear. In this study, we identified dorsal and dorsal-like genes in the cyclopoid copepod Paracyclopina nana. In silico analyses for identifying conserved domains and phylogenetic relationships supported their gene annotations. The transcriptional levels of both genes were slightly increased from the nauplius to copepodid stages, suggesting that these genes are putatively involved in copepodid development of P. nana. To examine the involvement of both genes in the innate immune response and under stressful conditions, the copepods were exposed to lipopolysaccharide (LPS), different culture densities, salinities, and temperatures. LPS significantly upregulated mRNA expressions of dorsal and dorsal-like genes, suggesting that both genes are transcriptionally sensitive in response to immune modulators. Exposure to unfavorable culture conditions also increased mRNA levels of dorsal and dorsal-like genes. These findings suggest that transcriptional regulation of the dorsal and dorsal-like genes would be associated with environmental changes in P. nana.