Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A1S6, Canada.
Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A1S6, Canada.
J Insect Physiol. 2021 Nov-Dec;135:104322. doi: 10.1016/j.jinsphys.2021.104322. Epub 2021 Oct 10.
Unlike almost all hematophagous insects, common bed bugs, Cimex lectularius, are not known to transmit pathogens to humans. To help unravel the reasons for their lack of vector competence, we studied the time- and tissue-dependent expression of innate immune factors after blood feeding or immune activation through the intrathoracic injection of bacteria. We used minimum inhibitory concentration (MIC) bioassays and the Kirby-Bauer protocol to evaluate antimicrobial peptide (AMP) activity in tissue extracts from the midguts or 'rest of body' (RoB) tissues (containing hemolymph and fat body AMPs) against Gram-positive and Gram-negative bacteria. We compared AMP activity between blood-fed female bed bugs and yellow fever mosquitoes, Aedes aegypti and determined how female and male bed bugs respond to immune challenges, and how long AMP gene expression remains elevated in bed bugs following a blood meal. Blood meal-induced AMP activity is 4-fold stronger in female bed bugs than in female mosquitoes. Male bed bugs have elevated AMP activity within 8 h of a blood meal or an intrathoracic injection with bacteria, with the strongest activity expressed in RoB tissue 24 h after the immune challenge. Female bed bugs have a stronger immune response than males within 24 h of a blood meal. The effects of blood meal-induced elevated AMP activity lasts longer against the Gram-positive bacterium, Bacillus subtilis, than against the Gram-negative bacterium Escherichia coli. Unravelling the specific immune pathways that are activated in the bed bugs' immune responses and identifying the bed bug-unique AMPs might help determine why these insects are not vectors of human parasites.
与几乎所有吸血昆虫不同，常见的臭虫（Cimex lectularius）不会将病原体传播给人类。为了帮助揭示它们缺乏媒介能力的原因，我们研究了在吸血或通过胸部注射细菌激活免疫后，先天免疫因子在时间和组织上的依赖性表达。我们使用最低抑菌浓度（MIC）生物测定法和 Kirby-Bauer 方案，评估了中肠或“体其余部分”（RoB）组织（含有血淋巴和脂肪体 AMP）组织提取物中抗革兰氏阳性和革兰氏阴性细菌的抗菌肽（AMP）活性。我们比较了吸血雌性臭虫和黄热病蚊子（埃及伊蚊）之间 AMP 活性的差异，并确定了雌性和雄性臭虫对免疫挑战的反应方式，以及 AMP 基因表达在吸血后多长时间内保持高水平。与雌性蚊子相比，吸血后的雌性臭虫 AMP 活性增强了 4 倍。雄性臭虫在吸血或胸部注射细菌后 8 小时内 AMP 活性升高，在免疫挑战 24 小时后，RoB 组织中的活性最强。与雄性相比，雌性臭虫在吸血后 24 小时内的免疫反应更强。针对革兰氏阳性菌枯草芽孢杆菌（Bacillus subtilis），血餐诱导的 AMP 活性增强的效果比针对革兰氏阴性菌大肠杆菌（Escherichia coli）的效果持续时间更长。阐明在臭虫免疫反应中激活的特定免疫途径，并确定臭虫特有的 AMP，可能有助于确定为什么这些昆虫不是人类寄生虫的媒介。
