Identification and characterization of hirudin-HN, a new thrombin inhibitor, from the salivary glands of Hirudo nipponia.

Transcriptome sequencing data (6.5 Gb) of the salivary glands of the haematophagous leech Hirudo nipponia was obtained by using the BGIseq-500 platform. After identification and analysis, one transcript (Unigene5370) was annotated to hirudin HV3 from Hirudo medicinalis with an e-value of 1e-29 and was named hirudin-HN. This transcript was a new thrombin inhibitor gene belonging to the proteinase inhibitor I14 (hirudin) family. Hirudin-HN, with a 270-bp cDNA, encodes an 89-aa protein containing a 20-aa signal peptide. The mature hirudin-HN protein contains the typical structural characteristics of hirudin, e.g., three conserved disulfide bonds and the PKP and DFxxIP motifs. Proteins (Hir and M-Hir) were obtained via prokaryotic expression, and the mature hirudin-HN protein was shown to have anticoagulant activity and thrombin affinity by using the chromogenic substrate S2238 and surface plasmon resonance (SPR) interaction analysis, respectively. The N-terminal structure of the mature hirudin-HN protein was shown to be important for anticoagulant activity by comparing the activity and thrombin affinity of Hir and M-Hir. The abundances of Hirudin-HN mRNA and protein were higher in the salivary glands of starving animals than in those of feeding or fed leeches. These results provided a foundation for further study on the structure-function relationship of hirudin-HN with thrombin.

Gene cloning and expression of a partial sequence of Hirudomacin, an antimicrobial protein that is increased in leech (Hirudo nipponica Whitman) after a blood meal.

The novel antimicrobial gene Hirudomacin (Hmc), with a 249-bp cDNA, encodes a mature protein of 61 amino acids and a 22-amino acid signal peptide. Hmc exhibits the highest similarity, at 90.1%, with macin family members found in the salivary gland of the leech Hirudo nipponica Whitman. A mature Hmc protein concentration of 219 µg/mL was detected using the Bradford method. The mature Hmc protein is 6862.82 Da and contains 8 cysteine residues. Antimicrobial assays showed a minimum bactericidal concentration and 50% lethal dose of 1.56 µg/mL and 0.78 µg/mL, respectively, for Staphylococcus aureus and 0.39 µg/mL and 0.195 µg/mL, respectively, for Bacillus subtilis. Transmission electron microscopy revealed membrane integrity disruption in S. aureus and B. subtilis, which resulted in bacterial lysis. The level of Hmc mRNA in the salivary gland during three blood meal stages indicated a remarkable trend of increase (P < .05), and western blotting demonstrated that among the three blood meal stages, expression of the mature Hmc protein was highest in both the salivary gland and intestine at the fed stage (P < .05). Immunofluorescence further showed the mature Hmc protein to be localized outside the cell nucleus, with the signal intensity in the salivary gland peaking at the fed stage (P < .05). In conclusion, the mature Hmc protein exhibits broad-spectrum antimicrobial effects against gram-positive and gram-negative bacteria, and a blood meal upregulates Hmc gene and protein expression in H. nipponica.

[Preliminary study on pathogen of Whitmania pigra disease in high temperature environment].

In this paper, on the contrast of healthy leech, the bacterial diversities were analyzed by 16S rDNA sequence analysis of the bacteria of muscle and intestinal tract of Whitmania pigra, the environment water and sediment of cultivating the diseased Wh. pigra in high temperature by high-throughput sequencing to determine the possible pathogenic bacteria of bacterial diseases of Leech in high temperature. The results showed that the original sequence reached over 83 000, and the effective sequences accounted for more than 87%. The GC contents ranged from 52% to 54% and the bacterial diversities were abundant. Bacterial relative abundance analysis showed that the bacterial content of Proteobacteria, Bacteroidetes, and Firmicutes was the most abundant in all treatments. Compared with healthy leech muscles and intestines, the muscle and intestinal tract of pathogenic leech relative abundance of Bacteroides, Pseudomonas, and Desulfovibrio was significantly increased, and it was abundant in water and sediment of diseased leeches, Lead to the possibility that the pathogenic bacteria of this bacterial disease may be Bacteroides, Pseudomonas, Desulfovibrio.