Shuanghu Cai

Complete genome sequence of Streptococcus agalactiae ZQ0910, a pathogen causing meningoencephalitis in the GIFT strain of Nile tilapia (Oreochromis niloticus).

Streptococcus agalactiae (group B streptococcus [GBS]) is a pathogen that causes meningoencephalitis in Nile tilapia (Oreochromis niloticus). Here, we reported the complete genome sequence of S. agalactiae strain ZQ0910, which was isolated from the GIFT strain of Nile tilapia in Guangdong, China.

Loop-mediated isothermal amplification method for rapid detection of Vibrio alginolyticus, the causative agent of vibriosis in mariculture fish

Aims:  The purpose of this study was to develop a loop‐mediated isothermal amplification (LAMP) method for the rapid, sensitive and simple detection of Vibrio alginolyticus in mariculture fish.

Cloning and expression of gene encoding the thermostable direct hemolysin from Vibrio alginolyticus strain HY9901, the causative agent of vibriosis of crimson snapper (Lutjanus erythopterus)

Aims:  The main aims of this study were to clone and express complete open reading frame (ORF) of thermostable direct haemolysin gene (tdh) from Vibrio alginolyticus strain HY9901 in Escherichia coli, and further evaluate the virulence of expressed TDH on mouse and crimson snapper.

Immune response in Lutjanus erythropterus induced by the major outer membrane protein (OmpU) of Vibrio alginolyticus

The outer membrane proteins (OMPs) of the marine aquatic animal pathogen Vibrio alginolyticus play an important role in the virulence of the bacterium and are potential candidates for vaccine development. In this study, the major 35.6 kDa OMP of V. alginolyticus was isolated by gel excision from the crude OMP fraction from V. alginolyticus. The sequence of the first 27 amino acid residues from the N-terminal end of the protein is ATV YKD GGT ELL VGG RVE FRG DFI GSD, which has high homology with OmpU proteins from other Vibrio spp. (92%). Lutjanus erythropterus were vaccinated with OmpU, and immunogenicity was confirmed by subsequent western blotting. Enzyme-linked immunosorbent assay (ELISA) analysis demonstrated that OmpU produced an observable antibody response in all sera of the vaccinated fish. L. erythropterus vaccinated with OmpU produced specific antibodies, and were highly resistant to infection with virulent V. alginolyticus. These results indicate that OmpU is an effective vaccine candidate against V. alginolyticus for L. erythropterus.

Immunoproteomic analysis and identification of novel immunogenic proteins from Vibrio harveyi.

Aims:  The main aim of this study was to screen novel immunogenic proteins of Vibrio harveyi, which could be vaccine candidates.

Protection against Vibrio alginolyticus in crimson snapper Lutjanus erythropterus immunized with a DNA vaccine containing the ompW gene.

The outer membrane proteins of Vibrio alginolyticus play an important role in the virulence of the bacterium and are potential candidates for vaccine development. In the present study, the ompW gene was cloned, expressed and purified. A DNA vaccine was constructed by inserting the ompW gene into a pcDNA plasmid. Crimson snapper Lutjanus erythropterus (Bloch) were injected intramuscularly with the recombinant plasmid pcDNA-ompW. The expression of the DNA vaccine was detected in gill, head kidney, heart, liver, spleen and injection site muscle of crimson snapper by RT-PCR 7 and 28 d post-vaccination. The ELISA results demonstrated that the DNA vaccine produced an observable antibody response in all sera of the vaccinated fish. In addition, crimson snapper immunized with the DNA vaccine showed a relative percentage survival (RPS) of 92.53%, indicating effective protection against V. alginolyticus infection.

Expression and immunogenicity analysis of accessory colonization factor A from Vibrio alginolyticus strain HY9901.

The accessory colonization factor A (ACFA) of Vibrio alginolyticus plays an important role in the efficient colonization of the bacterium and is potential candidates for vaccine development. In present study, the acfA gene was cloned, expressed and purified. Western blot analysis revealed protein recognition with the native ACFA in different V. alginolyticus strains. To analyze the immunogenicity of the recombinant ACFA, Lutjanus erythropterus Bloch were immunized by intraperitoneal injection, and the results demonstrated that the recombinant ACFA produced an observable antibody response in all sera of the vaccinated fish. The differential expressions of RAG1 gene in various tissues of L. erythropterus were analyzed by fluorescent quantitative real-time PCR, and the results showed the RAG1 mRNA expression was significantly up-regulated in thymus, head kidney and spleen tissue. Furthermore, the protective property of recombinant ACFA was evaluated through challenge with six heterogeneous virulent V. alginolyticus strains, and the immunohistochemical analysis in different tissues after challenge with V. alginolyticus. The results showed L. erythropterus vaccinated with recombinant ACFA were more tolerant of the infection by virulent V. alginolyticus strains. The data indicate that the recombinant ACFA could provide heterologous protection for the different virulent V. alginolyticus strains.

Development of Loop-mediated isothermal amplification method for rapid detection of Streptococcus iniae, the causative agent of streptococcicosis in fish

Streptococcus iniae is a major pathogen that causes sever economic losses in tilapia aquaculture. A set of four specific primers was designed by targeting lctO gene. With Bst DNA polymerase, the target DNA can be clearly amplified for 60 min at 64 °C in a simple water bath. The sensitivity of the LAMP assay for the detection of S. iniae is about 12.4 cells per reaction in both of pure cultures and added fish tissues cultures. LAMP products could be judged with agar gel or naked eye after addition of SYBR Green I. There were no cross‐reactions with other bacterial strains indicating high specificity of the LAMP. The LAMP method was also applied to detect S. iniae ‐infected tilapia tissues effectively. The LAMP assay reported here indicates the potential usefulness of the technique as a valuable simple, rapid alternative procedure for the detection of S. iniae during streptococcicosis monitoring of cultured fish. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Draft Genome Sequence of the Fish Pathogen Vibrio harveyi Strain ZJ0603

Vibrio harveyi is an important pathogen that causes vibriosis in various aquatic organisms. Here, we announce the draft genome sequence of V. harveyi strain ZJ0603, which was isolated from diseased Orange-spotted grouper (Epinephelus coioides) in Guangdong, China.

Characterization and function analysis of interleukin-1 receptor-associated kinase-1 (IRAK-1) from Fenneropenaeus penicillatus

Abstract The interleukin‐1 receptor‐associated kinase‐1 (IRAK‐1) is an important adapter protein which links downstream of MyD88, and involved in the complex composed of MyD88 and TRAF6 to activate TLRs signaling pathway. In this study, an IRAK‐1 homolog (FpIRAK‐1) was cloned from the red tail shrimp Fenneropenaeus penicillatus. The ORF of FpIRAK‐1 consisted of 2874 bp encoding a protein of 957 amino acids which contains a death domain (DD) and a catalytic domain of serine/threonine kinases (STKc). Homology analysis revealed that the predicted amino acid sequence of FpIRAK‐1 shared 71% similarities with IRAK‐1 of Litopenaeus vannamei. Real‐time RT‐PCR indicated that FpIRAK‐1 was constitutively expressed in various tissues of F. penicillatus. The expression level of FpIRAK‐1 mRNA was significantly up‐regulated and then decreased gradually after white spot syndrome virus (WSSV) and Vibrio alginolyticus challenge. Gene knockdown of FpIRAK‐1 enhanced the sensitivity of shrimps to WSSV and V. alginolyticus challenge, suggesting FpIRAK‐1 could play a positive role against bacterial and viral pathogens. In conclusion, the results of this study provide some insights into the function of FpIRAK‐1 in activating Toll signaling pathway and the host defense against invading pathogens. HighlightsAn IRAK‐1 homolog (FpIRAK‐1) was cloned from the red tail shrimp F. penicillatus.FpIRAK‐1 was constitutively expressed in various tissues of F. penicillatus.The expression levels of FpIRAK‐1 mRNA in the different tissues are responsive to WSSV and V. alginolyticus challenge.Gene knockdown of FpIRAK‐1 enhanced the sensitivity of shrimps to WSSV and V. alginolyticus challenge.