Johns R, Sonenshine D E, Hynes W L
Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA.
J Med Entomol. 1998 Jul;35(4):458-64. doi: 10.1093/jmedent/35.4.458.
The ability of hard ticks to prevent infection by bacteria was investigated. During a 72-h period, virtually all Dermacentor variabilis females survived inoculation with Bacillus subtilis, Escherichia coli, and Staphyloccocus aureus but few survived infection with Pseudomonas aeruginosa. The hemocyte population increased to peak abundance at 48 h to approximately 6 times that of the uninfected controls. In contrast, the soluble hemolymph protein content decreased inversely as the hemocytes increased. D. variabilis hemolymph was found to be constitutively antimicrobial (i.e., hemolymph from bacteria-naive individuals inhibited bacterial growth). Infection with various bacterial species enhanced this innate capability. When hemolymph fractions separated by high-pressure liquid chromatography were tested for their ability to inhibit microbial growth, activity against the gram-positive bacterium, B. subtilis, was found in 2 polar fractions. Antimicrobial activity was lost when the fractions were incubated with protease. The least polar fraction contained 1 major protein, M(r) 14.5 kDa, that comigrated with human lysozyme. This protein, tentatively identified as tick lysozyme, was abundant in bacteria-naive ticks but increased greatly (43%) following challenge with B. subtilis. The identity of the other, more polar protein is unknown. Studies to characterize these antimicrobial proteins are planned.
研究了硬蜱预防细菌感染的能力。在72小时内，几乎所有变异革蜱雌蜱在接种枯草芽孢杆菌、大肠杆菌和金黄色葡萄球菌后存活，但感染铜绿假单胞菌后很少存活。血细胞数量在48小时时增加到峰值丰度，约为未感染对照组的6倍。相反，可溶性血淋巴蛋白含量随着血细胞数量的增加而呈反比下降。发现变异革蜱血淋巴具有组成型抗菌能力（即从未接触过细菌的个体的血淋巴可抑制细菌生长）。感染各种细菌可增强这种先天能力。当对通过高压液相色谱分离的血淋巴组分进行抑制微生物生长能力测试时，在2个极性组分中发现了对革兰氏阳性菌枯草芽孢杆菌的活性。当这些组分与蛋白酶一起孵育时，抗菌活性丧失。极性最小的组分含有1种主要蛋白质，分子量为14.5 kDa，与人溶菌酶迁移率相同。这种蛋白质初步鉴定为蜱溶菌酶，在未接触过细菌的蜱中含量丰富，但在受到枯草芽孢杆菌攻击后大幅增加（43%）。另一种极性更强的蛋白质的身份未知。计划开展研究以表征这些抗菌蛋白。
