Molecular characterization of a cathepsin F-like protease in Trichinella spiralis.

BACKGROUND: Trichinellosis is a re-emerging infectious disease, caused by Trichinella spp. Cathepsin F belongs to cysteine protease that is a major virulence factor for parasitic helminths, and it may be a potential anti-helminth drug target and vaccine candidate. The aim of this study was to clone, express and identify a cathepsin F-like protease in Trichinella spiralis and to investigate its biochemical characteristics. METHODS: The full-length cDNA encoding a putative cathepsin F-like protease in T. spiralis, TsCF1, was cloned and its biochemical characterization and expression profile were analyzed. Transcription of TsCF1 at different developmental stages of T. spiralis was observed by RT-PCR. The recombinant TsCF1 protein was expressed by prokaryotic expression system and recombinant TsCF1 (rTsCF1) was analyzed by western blotting. And expression of TsCF1 at muscle larvae stage was performed by immunofluorescent technique. Molecular modeling of TsCF1 and its binding mode with E-64 and K11777 were analyzed. Enzyme activity and inhibitory test with E-64 as inhibitor were investigated by using Z-Phe-Arg-AMC as specific substrate. RESULTS: Sequence analysis revealed that TsCF1 ORF encodes a protein of 366 aa with a theoretical molecular weight of 41.9 kDa and an isoelectric point of 7.46. The cysteine protease conserved active site of Cys173, His309 and Asn333 were identified and cathepsin F specific motif ERFNAQ like KLFNAQ sequence was revealed in the propeptide of TsCF1. Sequence alignment analysis revealed a higher than 40 % identity with other cathepsin F from parasitic helminth and phylogenetic analysis indicated TsCF1 located at the junction of nematode and trematode. RT-PCR revealed the gene was expressed in muscle larvae, newborn larvae and adult stages. SDS-PAGE revealed the recombinant protein was expressed with the molecular weight of 45 kDa. The purified rTsCF1 was used to immunize rabbit and the immune serum could recognize a band of about 46 kDa in soluble protein of adult, muscle larvae and ES product of muscle larvae. Immunolocalization analysis showed that TsCF1 located on the cuticle and stichosome of the muscle larvae. After renaturation rTsCF1 demonstrated substantial enzyme activity to Z-Phe-Arg-AMC substrate with the optimal pH 5.5 and this activity could be inhibited by cysteine protease inhibitor E-64. Further analysis showed the kinetic parameters of rTsCF1 to be Km = 0.5091 µM and Vmax = 6.12 RFU/s µM at pH 5.5, and the IC50 value of E64 was 135.50 ± 16.90 nM. CONCLUSION: TsCF1 was expressed in all stages of T. spiralis and localized in the cuticle and stichosome. TsCF1 might play a role in the life cycle of T. spiralis and could be used as a potential vaccine candidate and drug target against T. spiralis infection.

Preliminary Analysis of Taenia multiceps Metacestode Antigens by Two-Dimensional Electrophoresis.

BACKGROUND: Taenia multiceps is a cestode parasite with its larval stage (metacestode), Coenurus cerebralis, mainly encysts in the central nervous system of sheep and other livestock causing cerebralis coenurosis. Since, treatment of coenurosis with chemotherapy showed little effect and surgical removal of cysts is not advisable in field conditions, vaccination is useful to control coenurosis. Previous study indicated that immunization with T. multiceps metacestode antigens could induce protection in sheep against coenurosis, so the aim of this study was to identify T. multiceps metacestode antigens in order to find potential vaccine development candidates for further study. METHODS: The protein extracts from the larval T. multiceps were analyzed by two-dimensional electrophoresis (2-DE) and characterized by mass spectrometry. RESULTS: A total of 150 protein spots were detected with isoelectric point (pI) value from 4.97 to 9.65 and molecular weight from 14 to 98 kDa. Twenty-two protein identities were determined by mass spectrometry and 15 unique proteins were obtained. Functional annotation revealed that some of these proteins are involved in catalytic activity, binding, metabolic, cellular process and stress response. Among these molecules are antioxidant proteins (peroxiredoxin and glutathione-S-transferase), glycolytic enzymes (malate dehydrogenase and enolase), proteins with chaperone activity (heat shock protein 70 and small heat shock protein), and structural proteins (actin, actin modulator protein and paramyosin). CONCLUSION: The identification of T. multiceps metacestode protein will provide valuable information to elucidate their specific roles in the parasitism and screen new targets for vaccine development.

Molecular characterization of Taenia multiceps isolates from Gansu Province, China by sequencing of mitochondrial cytochrome C oxidase subunit 1.

A total of 16 Taenia multiceps isolates collected from naturally infected sheep or goats in Gansu Province, China were characterized by sequences of mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. The complete cox1 gene was amplified for individual T. multiceps isolates by PCR, ligated to pMD18T vector, and sequenced. Sequence analysis indicated that out of 16 T. multiceps isolates 10 unique cox1 gene sequences of 1,623 bp were obtained with sequence variation of 0.12-0.68%. The results showed that the cox1 gene sequences were highly conserved among the examined T. multiceps isolates. However, they were quite different from those of the other Taenia species. Phylogenetic analysis based on complete cox1 gene sequences revealed that T. multiceps isolates were composed of 3 genotypes and distinguished from the other Taenia species.

[Research progress on cathepsin F of parasitic helminths].

Cathepsin F is an important member of papain-like subfamily in cysteine protease family. Cathepsin F of helminth parasites can hydrolyze the specific substrate, degrade host protein such as hemoglobin for nutrition, and be involved in invasion into host tissue. Therefore, cathepsin F serves as a potential target for parasitic disease immunodiagnosis, vaccine design and anti-parasite drug screening. This article reviews the structural characteristics and mechanisms of cathepsin F, and research advances on cathepsin F of parasitic helminths.

[Cloning and sequence analysis of thioredoxin peroxidase gene from Taenia multiceps].

Protoscoleces of Taenia multiceps were collected from the naturally infected sheep and total RNA was extracted. Specific primers were designed according to TaHe2-D11 mRNA sequence and T. multiceps thioredoxin peroxidase gene (TmTPx) was amplified by RT-PCR. PCR products were ligated into pMD18-T vector and transformed to E. coli DH5alpha. The recombinant plasmids were identified by restriction digestion and sequencing. A 614 bp cDNA was amplified. The TmTPx open reading frame (591 bp) encoded a 196-amino acid protein with Mr 21,690, pI 7.61. Bioinformatics analysis indicated that TmTPx had a typical 2-Cys Prx conserved domain. Phylogenetic tree revealed that T. multiceps had the closest relationship to T. asiatica, followed by T. solium and T. crassiceps, E. granulosus and E. multilocularis.