| Hematophagous arthropods have developed effective mechanisms to get a blood meal and overcome their host’s immune responses. Such arthropods produce a wide array of antihemostatic and immune suppressant compounds in their salivary glands. Numerous antihemostatic compoundshave been identified from blood-sucking arthropods,such as platelet aggregation inhibitors, vasodilators, anticoagulants, immunomodulation molecules and peptides, antimicrobial peptides and other pharmacopia of interacting molecules.Those compounds have great significance for us to undstanding the process between parasite and host co-evolution and Also provides us for the new ideas of medicine design.Hybomitra atriperoides is an insect belonging to Insecta, Tabanidae, Hybomitra Enderlein, mainly distributed in Gansu province.We purified a immunosuppressive peptid named Immunoregulin HA from the salivary gland extrat of Hybomitra atriperoides. Edman degradation method was used for the determination of its amino acid sequence, its complete amino acid sequence was GGVTGVTEFEPVDVSGEDYDSDEMDEDGRA, composed of30amino acid residues.We constructed cDNA library of Hybomitra atriperoides, producing a library of about2.3×105independent colonies from witch we cloned the full lenth cDNA sequence of the Immunoregulin HA. Immunoregulin HA was found to show similarity to immunosuppressant peptide, tabimmunregulins from T. yao and other immunosuppressant peptides in genebank。Immunoregulin HA could inhibit the secretion of interferon-y(IFN-y) and monocyte chemoattractant protein (MCP-1) and increase the secretion of interleukin-10(IL-10) induced by lipopolysaccharide (LPS) in rat splenocytes. IL-10is a suppressor cytokine of T-cell proliferative and cytokine responses.IL-10can inhibit the elaboration of pro-inflammatory cytokines. Immunoregulin HA possibly unregulated the IL-10production to inhibit IFN-y and MCP-1secretion in the current experiments. This immunosuppression may facilitate the blood feeding of this horsefly. The current works will facilitate to understand the molecular mechanisms of the ectoparasite-host relationship.Due to the development of the biotechnology and the computer technology, whole genome sequencing is possible.The significance of genome sequencing is that we can discover new genes at the first time, analysis and forecast their functions,Analysis of the evolutionary of each gene and target gene modification, understanding genome structure and gene function, molecular and mechanisms of genetic disorder, such as the development of personalized medicine.As the whole genome sequencing of panda(Ailuropoda melanoleuca) finished,we find a cathelicidin-like peptide we called PC.We blast and analyse this sequence and taking the study on the functions of it.Cathelicidins are a family of antimicrobial peptides acting as multifunctional effector molecules of innate immunity, which are firstly found in mammalians. Cathelicidins consist of an N-terminal putative signal peptide, a conserved cathelin-like domain and a C-terminal antimicrobial domain that varies remarkably in size(ranging from12to100amino acids).They possess broad spectrum antimicrobial activity, not only against Gram-positive bacteria, Gram-negtive bacteria, fungi and viruses, but also many antibiotic-resisted clinical bacteria. In addition, they possess many other biological activities, such as immune cell chemotaxis, mast cell degranulation and histamine release, transcriptional regulation of macrophage, wound repair, angiogenesis, cytolytic activity, etc.We analyzed the structure of PC, a-helical structure and p-sheet is the predicted secondary structure, this structures is necessary for it’s antibacterial activity. The possible biological activities of PC were studied. PC has a diverse range of antimicrobial activity. It is microbicidal against Gram-positive bacteria, Gram-negtive bacteria and fungi, including many antibiotic-resisted clinical bacteria.PC also obviously exhibits lectin activity, antitumor activity Pro-platelet aggregationactivity while it shows no antioxidant activity, hemolytic activity, serine protease and serine protease inhibitor activity and anti-trichomonas vaginalis activity and low cytotoxicity. However, it can’t stimulate rat mast cell degranulation. These results suggest that PC may play an important role in panda innate immune response to invasion of external pathogenic microorganisms. The tumor model in nude mice shows that the PC have no obviously side effects, while low doses inhibited the tumors. As PC’s broad-spectrum antimicrobial activity and tumor cell toxicity and low hemolytic properties, making it an excellent drug candidate molecule, from an evolutionary point of view can be seen, PC has played an irreplaceable role in the panda’s long-term evolution of microbial resistance to the infection. |
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