Department of Pathology, University of Cambridgegrid.5335.0, Cambridge, United Kingdom.
Department of Information Engineering, University of Padova, Padua, Italy.
J Virol. 2022 Mar 9;96(5):e0118121. doi: 10.1128/JVI.01181-21. Epub 2022 Jan 12.
Papillomaviruses exclusively infect stratified epithelial tissues and cause chronic infections. To achieve this, infected cells must remain in the epithelial basal layer alongside their uninfected neighbors for years or even decades. To examine how papillomaviruses achieve this, we used the MmuPV1 (Mus musculus papillomavirus 1) model of lesion formation and persistence. During early lesion formation, an increased cell density in the basal layer, as well as a delay in the infected cells' commitment to differentiation, was apparent in cells expressing MmuPV1 E6/E7 RNA. Using cell culture models, keratinocytes exogenously expressing MmuPV1 E6, but not E7, recapitulated this delay in differentiation postconfluence and also grew to a significantly higher density. Cell competition assays further showed that MmuPV1 E6 expression led to a preferential persistence of the cell in the first layer, with control cells accumulating almost exclusively in the second layer. Interestingly, the disruption of MmuPV1 E6 binding to MAML1 protein abrogated these phenotypes. This suggests that the interaction between MAML1 and E6 is necessary for the lower (basal)-layer persistence of MmuPV1 E6-expressing cells. Our results indicate a role for E6 in lesion establishment by facilitating the persistence of infected cells in the epithelial basal layer, a mechanism that is most likely shared by other papillomavirus types. Interruption of this interaction is predicted to impede persistent papillomavirus infection and consequently provides a novel treatment target. Persistent infection with high-risk HPV types can lead to development of HPV-associated cancers, and persistent low-risk HPV infection causes problematic diseases, such as recurrent respiratory papillomatosis. The management and treatment of these conditions pose a considerable economic burden. Maintaining a reservoir of infected cells in the basal layer of the epithelium is critical for the persistence of infection in the host, and our studies using the mouse papillomavirus model suggest that E6 gene expression leads to the preferential persistence of epithelial cells in the lower layers during stratification. The E6 interaction with MAML1, a component of the Notch pathway, is required for this phenotype and is linked to E6 effects on cell density and differentiation. These observations are likely to reflect a common E6 role that is preserved among papillomaviruses and provide us with a novel therapeutic target for the treatment of recalcitrant lesions.
乳头瘤病毒专门感染分层上皮组织并引起慢性感染。为了实现这一目标，感染细胞必须与未感染的相邻细胞一起留在上皮基底层数年甚至数十年。为了研究乳头瘤病毒如何实现这一目标，我们使用了 MmuPV1（小鼠乳头瘤病毒 1）病变形成和持续存在的模型。在早期病变形成过程中，在表达 MmuPV1 E6/E7 RNA 的细胞中，基底层中的细胞密度增加，以及感染细胞向分化的分化延迟，这一点很明显。使用细胞培养模型，外源性表达 MmuPV1 E6 的角质形成细胞在细胞融合后复制了这种分化延迟，并且细胞密度也显著增加。细胞竞争测定进一步表明，MmuPV1 E6 表达导致细胞在第一层中优先持续存在，而对照细胞几乎仅在第二层中积累。有趣的是，破坏 MmuPV1 E6 与 MAML1 蛋白的结合消除了这些表型。这表明，MAML1 和 E6 之间的相互作用对于 MmuPV1 E6 表达细胞在基底层中的较低（基底）层的持续存在是必要的。我们的研究结果表明，E6 在病变建立中起作用，通过促进感染细胞在上皮基底层中的持续存在，这一机制很可能被其他乳头瘤病毒类型共享。阻断这种相互作用预计会阻碍持续性乳头瘤病毒感染，并因此提供了一个新的治疗靶点。高危 HPV 类型的持续性感染可导致 HPV 相关癌症的发展，而持续性低危 HPV 感染会导致复发性呼吸道乳头状瘤病等有问题的疾病。这些疾病的管理和治疗带来了相当大的经济负担。在上皮基底层中维持感染细胞的储库对于宿主感染的持续存在至关重要，我们使用小鼠乳头瘤病毒模型进行的研究表明，E6 基因表达导致在分层过程中上皮细胞在较低层中优先持续存在。E6 与 Notch 途径的组成部分 MAML1 的相互作用是这种表型所必需的，并且与 E6 对细胞密度和分化的影响有关。这些观察结果可能反映了乳头瘤病毒之间普遍存在的 E6 作用，并为我们提供了治疗顽固性病变的新的治疗靶点。
