Paranosema locustae is an entomopathogenic microsporidia with promising potential for controlling agricultural pests, including Locusta migratoria manilensis. However, it has the disadvantage of having a slow insecticidal rate, and how P. locustae infection impacts the host immune response is currently unknown. The present study investigated the effect of P. locustae on the natural immune response of L. migratoria and the activities of enzymes that protect against oxidative stress. Infection with P. locustae increased the hemocytes and nodulation number of L. migratoria at the initial stage of infection. The hemocyte-mediated modulation of immune response was also affected by a decrease in the number of hemocytes 12 days postinfection. Superoxide dismutase activity in locusts increased in the early stages of infection but decreased in the later stages, whereas the activities of peroxidase (POD) and catalase (CAT) showed opposite trends may be due to their different mechanisms of action. Furthermore, the transcription levels of mRNA of antimicrobial peptide-related genes and phenoloxidase activity in hemolymph in L. migratoria were suppressed within 15 days of P. locustae infection. Overall, our data suggest that P. locustae create a conducive environment for its own proliferation in the host by disrupting the immune defense against it. These findings provide useful information for the potential application of P. locustae as a biocontrol agent.

中文翻译：

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马尼拉飞蝗感染蝗虫不同时期的免疫反应

Paranosema locustae是一种昆虫病原性微孢子虫，在控制农业害虫（包括东亚飞蝗）方面具有广阔的潜力。但其缺点是杀虫速度慢，且蝗虫感染如何影响宿主免疫反应目前尚不清楚。本研究调查了蝗虫对飞蝗自然免疫反应的影响以及防止氧化应激的酶活性。蝗虫感染使飞蝗感染初期的血细胞和结瘤数量增加。血细胞介导的免疫反应调节也受到感染后 12 天血细胞数量减少的影响。蝗虫感染初期超氧化物歧化酶活性升高，后期降低，而过氧化物酶（POD）和过氧化氢酶（CAT）活性则表现出相反的趋势，可能是由于其作用机制不同。此外，飞蝗感染后15天内抗菌肽相关基因的mRNA转录水平和血淋巴中酚氧化酶活性均受到抑制。总体而言，我们的数据表明，蝗虫通过破坏宿主的免疫防御，为其在宿主体内的增殖创造了有利的环境。这些发现为蝗虫作为生物防治剂的潜在应用提供了有用的信息。