Table_2_A Novel Densovirus Isolated From the Asian Tiger Mosquito Displays Varied Pathogenicity Depending on Its Host Species.XLS

Mosquito-borne viral diseases (MBVDs) continue to pose a significant global public health burden. Mosquito control remains a core intervention strategy in integrated mosquito management (IMM) programs to reduce the transmission of MBVDs. Mosquito densoviruses (MDVs) are mosquito-specific entomopathogenic viruses, and their attractive biological and pathogenic characteristics make MDVs potential biological control agents as alternatives to traditional chemical pesticides. However, different viral strains vary greatly in their pathogenicity against different mosquito species, which poses an obstacle for the wide application of MDVs in vector control. In this study, a novel MDV, Aedes albopictus densovirus-7 (AalDV-7), was isolated from field-collected Aedes albopictus in the dengue-endemic area of Guangzhou, China. The complete 4,048 nt genome of AalDV-7 was cloned and sequenced, and the transcription and translation of three open reading frames (ORFs) were characterized. Phylogenetic analysis indicated that AalDV-7 clustered with MDVs mostly isolated from indigenous mosquitoes. The pathogenicity of AalDV-7 to A. albopictus, Aedes aegypti, and Culex quinquefasciatus larvae was completely different, and the median lethal dose (LD50) of AalDV-7 in A. albopictus which was 109.48 genome equivalents per ml (geq/ml) was 12 and 46 times lower than those in A. aegypti (1010.56 geq/ml) and C. quinquefasciatus (1011.15 geq/ml). Furthermore, the median lethal time (LT50) value in A. albopictus (7.72 days) was 25% and 26% shorter than those in A. aegypti (10.24 days) and C. quinquefasciatus (10.42 days) at a titer of 1011 geq/ml. Furthermore, the mortality of AalDV-7-infected mosquitoes increased in a dose-dependent manner, and the highest mortality was found in A. albopictus larvae exposed to 1011 geq/ml AalDV-7 (82.00%). Sublethal effects analysis also showed that AalDV-7 infection significantly decreased pupation and emergence rates. The 1st–2nd instar larvae of all three mosquito species showed a near 100% infection rate, and the highest relative vial titer (305.97 ± 67.57 geq/ng) was observed in the 1st–2nd instar larvae of C. quinquefasciatus. These pathogenic characteristics make AalDV-7 a potential MBVDs control agent in China, whereas its negligible pathogenicity and high infection rate and viral dose in vivo make it a good candidate for gene delivery vectors in C. quinquefasciatus gene function analysis. In conclusion, the continuous discovery and isolation of new MDVs enrich the pool of mosquito entomopathogenic viruses and provide a variety of choices for optimal MDVs or combinations of MDVs to target certain mosquitoes.

虫媒病毒性疾病（Mosquito-borne viral diseases, MBVDs）仍在全球范围内造成沉重的公共卫生负担。在综合蚊虫管理（Integrated Mosquito Management, IMM）项目中，蚊虫防控仍是降低MBVDs传播的核心干预策略。蚊虫致密病毒（Mosquito densoviruses, MDVs）是专性侵染蚊虫的昆虫病原病毒，其优异的生物学与致病特性使其有望成为替代传统化学杀虫剂的潜在生物防控因子。然而，不同病毒毒株对不同蚊虫物种的致病力差异显著，这阻碍了MDVs在媒介生物防控中的大规模应用。本研究从中国广州登革热流行区野外采集的白纹伊蚊（Aedes albopictus）中分离得到一株新型MDV——白纹伊蚊致密病毒7号（Aedes albopictus densovirus-7, AalDV-7）。研究人员克隆并测定了AalDV-7的完整4048 nt基因组，并对其3个开放阅读框（open reading frames, ORFs）的转录与翻译特征进行了解析。系统发育分析显示，AalDV-7与多数从本土蚊虫中分离得到的MDVs聚为一支。AalDV-7对白纹伊蚊、埃及伊蚊（Aedes aegypti）以及致倦库蚊（Culex quinquefasciatus）幼虫的致病力差异显著：其对白纹伊蚊的半数致死剂量（median lethal dose, LD50）为10^9.48 基因组当量/毫升（geq/ml），分别比埃及伊蚊（10^10.56 geq/ml）和致倦库蚊（10^11.15 geq/ml）低12倍与46倍。此外，当病毒滴度为10^11 geq/ml时，白纹伊蚊的半数致死时间（median lethal time, LT50）为7.72天，较埃及伊蚊（10.24天）与致倦库蚊（10.42天）分别缩短25%与26%。此外，AalDV-7感染蚊虫的死亡率呈剂量依赖性升高，其中以暴露于10^11 geq/ml AalDV-7的白纹伊蚊幼虫死亡率最高，达82.00%。亚致死效应分析结果显示，AalDV-7感染可显著降低蚊虫的化蛹率与羽化率。三种蚊虫的1-2龄幼虫感染率均接近100%，其中致倦库蚊1-2龄幼虫的相对病毒滴度最高，为(305.97 ± 67.57) geq/ng。上述致病特性使得AalDV-7成为中国境内防控MBVDs的潜在候选因子；而其对致倦库蚊的致病力可忽略不计，且在该蚊体内感染率与病毒载量较高，使其成为致倦库蚊基因功能研究中基因递送载体的理想候选对象。综上，持续发现与分离新型MDVs可丰富蚊虫病原病毒库，为筛选针对特定蚊虫的最优MDV或MDV组合提供了多样化选择。