Cloning and sequence analysis ofHemonchus ContortusHC58cDNA

DNA vaccine encoding Haemonchus contortus actin induces partial protection in goats

Actin is a globular multi-functional protein that forms microfilaments, and participates in many important cellular processes. Previous study found that Haemonchus contortus actin could be recognized by the serum of goats infected with the homology parasite. This indicated that H. contortus actin could be a potential candidate for vaccine. In this study, DNA vaccine encoding H. contortus actin was tested for protection against experimental H. contortus infections in goats. Fifteen goats were allocated into three trial groups. The animals of Actin group were vaccinated with the DNA vaccine on day 0 and 14, and challenged with 5000 infective H. contortus third stage larval (L3) on day 28. An unvaccinated positive control group was challenged with L3 at the same time. An unvaccinated negative control group was not challenged with L3. The results showed that DNA vaccine were transcribed at local injection sites and expressed in vivo post immunizations respectively. For goats in Actin vaccinated group, higher levels of serum IgG, serum IgA and mucosal IgA were produced, the percentages of CD4(+) T lymphocytes, CD8(+) T lymphocytes and B lymphocytes and the concentrations of TGF-β were increased significantly (P<0.05). Following L3 challenge, the mean eggs per gram feces (EPG) and worm burdens of Actin group were reduced by 34.4% and 33.1%, respectively. This study suggest that recombinant H. contortus Actin DNA vaccine induced partial immune response and has protective potential against goat haemonchosis.

Vaccination of goats with DNA vaccine encoding Dim-1 induced partial protection against Haemonchus contortus: a preliminary experimental study

Disorganized muscle family member (Dim-1) belongs to immunoglobulin superfamily, and is a structural protein localized to the region of the muscle cell membrane around and between the dense bodies. Strong immunogenicity to host's immune system was induced by Dim-1 from Ascaris suum, which indicated that Dim-1 could be a potential candidate for vaccine. The homologues of Dim-1 were also detected in nematodes Brugia malayi and Trichostrongylus colubriformis. However, information on the complete coding sequence and protection potential of this molecule in Haemonchus contortus is lacking. In this study, full length of Dim-1 cDNA was cloned using a rapid amplification of cDNA ends (RACE) strategy and the DNA vaccine encoding Dim-1 open reading frame (ORF) was tested for protection against experimental H. contortus infections in goats. Fifteen goats were allocated into three trial groups. The animals of Dim-1 group were vaccinated with the DNA vaccine encoding Dim-1 on day 0 and 14, and challenged with 5000 infective H. contortus third larval stage (L3) on day 28. An unvaccinated positive control group was challenged with L3 at the same time. An unvaccinated negative control group was not challenged with L3. The results indicated Dim-1 DNA vaccines were transcribed at local injection sites and expressed in vivo post immunizations respectively. Following L3 challenge, the mean eggs per gram feces (EPG) and worm burdens of Dim-1 group were reduced by 45.7% and 51.1%, respectively. Significantly high levels of serum IgG, serum IgA, mucosal IgA, CD4(+) T lymphocytes and B lymphocytes of Dim-1 group were produced. While compared with the negative control group, increased numbers of blood eosinophils and lymphocytes and declined haemoglobin level were observed in the Dim-1 group after L3 challenge. The preliminary study suggest that recombinant H. contortus Dim-1 DNA vaccine induced partial immune response and has protective potential against goat haemonchosis.

Cloning and characterization of a selenium-independent glutathione peroxidase (HC29) from adult Haemonchus contortus

The complete coding sequence of Haemonchus (H.) contortus HC29 cDNA was generated by rapid amplification of cDNA ends in combination with PCR using primers targeting the 5'- and 3'-ends of the partial mRNA sequence. The cloned HC29 cDNA was shown to be 1,113 bp in size with an open reading frame of 507 bp, encoding a protein of 168 amino acid with a calculated molecular mass of 18.9 kDa. Amino acid sequence analysis revealed that the cloned HC29 cDNA contained the conserved catalytic triad and dimer interface of selenium-independent glutathione peroxidase (GPX). Alignment of the predicted amino acid sequences demonstrated that the protein shared 44.7~80.4% similarity with GPX homologues in the thioredoxin-like family. Phylogenetic analysis revealed close evolutionary proximity of the GPX sequence to the counterpart sequences. These results suggest that HC29 cDNA is a GPX, a member of the thioredoxin-like family. Alignment of the nucleic acid and amino acid sequences of HC29 with those of the reported selenium-independent GPX of H. contortus showed that HC29 contained different types of spliced leader sequences as well as dimer interface sites, although the active sites of both were identical. Enzymatic analysis of recombinant prokaryotic HC29 protein showed activity for the hydrolysis of H₂O₂. These findings indicate that HC29 is a selenium-independent GPX of H. contortus.

Haemonchus contortus: cloning and characterization of serpin

The serpin gene of Haemonchus contortus (hc-serpin) was cloned and characterized in this study. Specific primers for rapid amplification cDNA ends (RACE) were designed based on the expression sequence tag (EST, BM173953) to amplify the 3'- and 5'-ends of hc-serpin. The full length of the cDNA of this gene was obtained by overlapping the sequences of 3'- and 5'-extremities and amplification by reverse transcription-PCR. The biochemical activities of the recombinant protein (rHc-Serpin), which was expressed in prokaryotic cells and purified by affinity chromatography and size-exclusion chromatography, were analyzed by assays of trypsin inhibition, anti-coagulation activity, and stability to temperature and pH. The results showed that the cloned full-length cDNA comprised 1317bp and encoded a peptide with 367 amino acid residues which showed sequence similarity to several known serpins. The rHc-Serpin inhibited trypsin activity effectively and prolonged the coagulation time of rabbit blood in vitro. The rHc-Serpin was stable from pH 2.0-10.0 and kept activity at high temperature until 75 degrees C. Optimal pH of rHc-Serpin protein to inhibit trypsin activity was at pH 7.6. The natural serpin of H. contortus detected by immunoblot assay was about 63kDa, and the rHc-Serpin was recognized strongly by serum from naturally infected goats. By immunohistochemistry, the serpin was localised exclusively in the epithelial cells of gastrointestinal tract in adult H. contortus. The results indicated that the cloned gene was serpin and that the protein may play important roles in the biological functions of H. contortus.