Kim Tae K, Radulovic Zeljko, Mulenga Albert
Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX, USA.
Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX, USA.
Ticks Tick Borne Dis. 2016 Apr;7(3):405-14. doi: 10.1016/j.ttbdis.2015.12.017. Epub 2015 Dec 29.
Amblyomma americanum tick serine protease inhibitor (serpin, AAS) 19, is a highly conserved protein that is characterized by its functional domain being 100% conserved across tick species. We also reported that AAS19 was an immunogenic tick saliva protein with anti-haemostatic functions and an inhibitor of trypsin-like proteases including five of the eight serine protease factors in the blood clotting cascade. In this study the goal was to validate the importance of AAS19 in A. americanum tick physiology, assess immunogenicity and investigate tick vaccine efficacy of yeast-expressed recombinant (r) AAS19. We confirm that AAS19 is important to A. americanum fitness and blood meal feeding. AAS19 mRNA disruption by RNAi silencing caused ticks to obtain blood meals that were 50% smaller than controls, and treated ticks being morphologically deformed with 100% of the deformed ticks dying in incubation. We show that rAAS19 is highly immunogenic in that two 500 μg inoculations mixed with TiterMax Gold adjuvant provoked antibody titers of more than 1:320,000 that specifically reacted with native AAS19 in unfed and partially fed tick tissue. Since AAS19 is injected into animals during tick feeding, we challenge infested immunized rabbits twice to test if tick infestations of immunized rabbits could act as booster. While in the first infestation significantly smaller tick blood meals were observed on one of the two immunized rabbits, smaller blood meals were observed on both rabbits, but 60% of ticks that engorged on immunized rabbits in the second infestation failed to lay eggs. It is notable that ticks fed faster on immunized animals despite obtaining smaller blood meals. We conclude that rAAS19 is a potential component of cocktail tick vaccine.
美洲钝眼蜱丝氨酸蛋白酶抑制剂（丝氨酸蛋白酶抑制剂，AAS）19是一种高度保守的蛋白质，其功能结构域在蜱类物种中100%保守。我们还报道过，AAS19是一种具有抗止血功能的免疫原性蜱唾液蛋白，是胰蛋白酶样蛋白酶的抑制剂，包括凝血级联反应中八个丝氨酸蛋白酶因子中的五个。在本研究中，目标是验证AAS19在美洲钝眼蜱生理学中的重要性，评估其免疫原性，并研究酵母表达的重组（r）AAS19的蜱疫苗效力。我们证实AAS19对美洲钝眼蜱的健康和血餐摄取很重要。通过RNA干扰沉默使AAS19 mRNA破坏，导致蜱获取的血餐比对照组小50%，且处理过的蜱在形态上变形，100%的变形蜱在孵化过程中死亡。我们表明，rAAS19具有高度免疫原性，两次500μg接种并与TiterMax Gold佐剂混合，可引发超过1:320,000的抗体滴度，该抗体与未进食和部分进食的蜱组织中的天然AAS19特异性反应。由于在蜱进食期间AAS19会注入动物体内，我们对受感染的免疫兔子进行了两次攻击，以测试免疫兔子的蜱感染是否可起到加强作用。虽然在第一次感染时，在两只免疫兔子中的一只上观察到明显较小的蜱血餐，但在两只兔子上都观察到了较小的血餐，不过在第二次感染中，在免疫兔子身上饱血的蜱中有60%未能产卵。值得注意的是，尽管蜱获取的血餐较小，但在免疫动物身上进食更快。我们得出结论，rAAS19是蜱鸡尾酒疫苗的潜在成分。
