Institute for Multidisciplinary Research in Applied Biology, Universidad Pública de Navarra, 31006 Pamplona, Spain.
Hydrosciences Montpellier, Université de Montpellier, IMT Mines Ales, IRD, CNRS, 30319 Ales, France.
Viruses. 2022 Mar 26;14(4):687. doi: 10.3390/v14040687.
Helicoverpa armigera single nucleopolyhedrovirus (HearSNPV) is a virulent pathogen of lepidopterans in the genera and , whereas Helicoverpa armigera multiple nucleopolyhedrovirus (HearSNPV) is a different virus species with a broader host range. This study aimed to examine the consequences of coocclusion of HearSNPV and HearMNPV on the pathogenicity, stability and host range of mixed-virus occlusion bodies (OBs). HearSNPV OBs were approximately 6-fold more pathogenic than HearMNPV OBs, showed faster killing by approximately 13 h, and were approximately 45% more productive in terms of OB production per larva. For coocclusion, larvae were first inoculated with HearMNPV OBs and subsequently inoculated with HearSNPV OBs at intervals of 0-72 h after the initial inoculation. When the interval between inoculations was 12-24 h, OBs collected from virus-killed insects were found to comprise 41-57% of HearSNPV genomes, but the prevalence of HearSNPV genomes was greatly reduced (3-4%) at later time points. Quantitative PCR (qPCR) analysis revealed the presence of HearSNPV genomes in a small fraction of multinucleocapsid ODVs representing 0.47-0.88% of the genomes quantified in ODV samples, indicating that both viruses had replicated in coinfected host cells. End-point dilution assays on ODVs from cooccluded mixed-virus OBs confirmed the presence of both viruses in 41.9-55.6% of wells that were predicted to have been infected by a single ODV. A control experiment indicated that this result was unlikely to be due to the adhesion of HearSNPV ODVs to HearMNPV ODVs or accidental contamination during ODV band extraction. Therefore, the disparity between the qPCR and end-point dilution estimates of the prevalence of mixed-virus ODVs likely reflected virus-specific differences in replication efficiency in cell culture and the higher infectivity of pseudotyped ODVs that were produced in coinfected parental cells. Bioassays on , and larvae revealed that mixed-virus OBs were capable of infecting heterologous hosts, but relative potency values largely reflected the proportion of HearMNPV present in each mixed-virus preparation. The cooccluded mixtures were unstable in serial passage; HearSNPV rapidly dominated during passage in whereas HearMNPV rapidly dominated during passage in the heterologous hosts. We conclude that mixed-virus coocclusion technology may be useful for producing precise mixtures of viruses with host range properties suitable for the control of complexes of lepidopteran pests in particular crops, although this requires validation by field testing.
棉铃虫单粒包埋型核型多角体病毒（HearSNPV）是鳞翅目 和 属昆虫的一种剧毒病原体，而棉铃虫多粒包埋型核型多角体病毒（HearSNPV）是一种不同的病毒物种，宿主范围更广。本研究旨在研究 HearSNPV 和 HearMNPV 共同包埋对混合病毒包涵体（OB）的致病性、稳定性和宿主范围的影响。HearSNPV OB 比 HearMNPV OB 大约毒力强 6 倍，致死速度快约 13 小时，且每头幼虫产生的 OB 产量大约高 45%。对于共同包埋，首先用 HearMNPV OB 感染幼虫，然后在初次接种后 0-72 小时之间再次用 HearSNPV OB 感染。当接种间隔为 12-24 小时时，从病毒杀死的昆虫中收集的 OB 中发现 HearSNPV 基因组占 41-57%，但在稍后的时间点 HearSNPV 基因组的流行率大大降低（3-4%）。实时定量 PCR（qPCR）分析表明，在代表 ODV 样本中定量的基因组的 0.47-0.88%的一小部分多核衣壳 ODV 中存在 HearSNPV 基因组，表明两种病毒都在感染的宿主细胞中复制。对来自共同包埋的混合病毒 OB 的 ODV 进行终点稀释测定证实，在预测由单个 ODV 感染的 41.9-55.6%的孔中都存在两种病毒。对照实验表明，这种结果不太可能是由于 HearSNPV ODV 附着在 HearMNPV ODV 上或在 ODV 带提取过程中偶然污染造成的。因此，qPCR 和终点稀释法估计混合病毒 ODV 流行率之间的差异可能反映了细胞培养中病毒复制效率的特异性差异，以及在感染的亲代细胞中产生的假型 ODV 的更高感染力。对 、 和 幼虫的生物测定表明，混合病毒 OB 能够感染异源宿主，但相对效力值主要反映了每个混合病毒制剂中 HearMNPV 的比例。在连续传代中，混合病毒混合物不稳定；在 中传代时 HearSNPV 迅速占主导地位，而在异源宿主中传代时 HearMNPV 迅速占主导地位。我们得出的结论是，混合病毒共包埋技术可能有助于生产具有宿主范围特性的精确病毒混合物，用于控制特定作物中鳞翅目害虫的复杂种群，尽管这需要通过田间试验进行验证。
