Tsuji Naotoshi, Battsetseg Badgar, Boldbaatar Damdinsuren, Miyoshi Takeharu, Xuan Xuenan, Oliver James H, Fujisaki Kozo
Laboratory of Emerging Infectious Diseases, School of Frontier Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
Infect Immun. 2007 Jul;75(7):3633-40. doi: 10.1128/IAI.00256-07. Epub 2007 May 7.
Antimicrobial peptides are major components of host innate immunity, a well-conserved, evolutionarily ancient defensive mechanism. Infectious disease-bearing vector ticks are thought to possess specific defense molecules against the transmitted pathogens that have been acquired during their evolution. We found in the tick Haemaphysalis longicornis a novel parasiticidal peptide named longicin that may have evolved from a common ancestral peptide resembling spider and scorpion toxins. H. longicornis is the primary vector for Babesia sp. parasites in Japan. Longicin also displayed bactericidal and fungicidal properties that resemble those of defensin homologues from invertebrates and vertebrates. Longicin showed a remarkable ability to inhibit the proliferation of merozoites, an erythrocyte blood stage of equine Babesia equi, by killing the parasites. Longicin was localized at the surface of the Babesia sp. parasites, as demonstrated by confocal microscopic analysis. In an in vivo experiment, longicin induced significant reduction of parasitemia in animals infected with the zoonotic and murine B. microti. Moreover, RNA interference data demonstrated that endogenous longicin is able to directly kill the canine B. gibsoni, thus indicating that it may play a role in regulating the vectorial capacity in the vector tick H. longicornis. Theoretically, longicin may serve as a model for the development of chemotherapeutic compounds against tick-borne disease organisms.
抗菌肽是宿主固有免疫的主要组成部分，是一种高度保守、进化上古老的防御机制。携带传染病的媒介蜱被认为拥有针对其在进化过程中获得的传播病原体的特定防御分子。我们在长角血蜱中发现了一种名为longicin的新型杀寄生虫肽，它可能是从一种类似于蜘蛛和蝎子毒素的共同祖先肽进化而来的。长角血蜱是日本巴贝斯虫属寄生虫的主要传播媒介。Longicin还表现出与无脊椎动物和脊椎动物防御素同源物相似的杀菌和杀真菌特性。Longicin通过杀死寄生虫，显示出显著抑制马巴贝斯虫红细胞内期裂殖子增殖的能力。共聚焦显微镜分析表明，Longicin定位于巴贝斯虫属寄生虫的表面。在一项体内实验中，longicin显著降低了感染人畜共患的微小巴贝斯虫和鼠微小巴贝斯虫的动物的寄生虫血症。此外，RNA干扰数据表明，内源性longicin能够直接杀死犬吉氏巴贝斯虫，因此表明它可能在调节长角血蜱的传播能力中发挥作用。从理论上讲，longicin可作为开发抗蜱传疾病病原体化学治疗化合物的模型。
