Identification of new antiviral agents against Kaposi’s sarcoma-associated herpesvirus (KSHV) by high-throughput drug screening reveals the role of histamine-related signaling in promoting viral lytic reactivation

Kaposi’s sarcoma-associated herpesvirus (KSHV) causes several human cancers, such as Kaposi’s sarcoma (KS) and primary effusion lymphoma (PEL). Current treatment options for KSHV infection and virus associated diseases are sometimes ineffective, therefore, more effectively antiviral agents are urgently needed. As a herpesvirus, lytic replication is critical for KSHV pathogenesis and oncogenesis. In this study, we have established a high-throughput screening assay by using an inducible KSHV+ cell-line, iSLK.219. After screening a compound library that consisted of 1280 Food and Drug Administration (FDA)-approved drugs, 15 hit compounds that effectively inhibited KSHV virion production were identified, most of which have never been reported with anti-KSHV activities. Interestingly, 3 of these drugs target histamine receptors or signaling. Our data further confirmed that antagonists targeting different histamine receptors (HxRs) displayed excellent inhibitory effects on KSHV lytic replication from induced iSLK.219 or BCBL-1 cells. In contrast, histamine and specific agonists of HxRs promoted viral lytic replication from induced iSLK.219 or KSHV-infected primary cells. Mechanistic studies indicated that downstream MAPK and PI3K/Akt signaling pathways were required for histamine/receptors mediated promotion of KSHV lytic replication. Direct knockdown of HxRs in iSLK.219 cells effectively blocked viral lytic gene expression during induction. Using samples from a cohort of HIV+ patients, we found that the KSHV+ group has much higher levels of histamine in their plasma and saliva than the KSHV- group. Taken together, our data have identified new anti-KSHV agents and provided novel insights into the molecular bases of host factors that contribute to lytic replication and reactivation of this oncogenic herpesvirus.

卡波西肉瘤相关疱疹病毒（Kaposi’s sarcoma-associated herpesvirus, KSHV）可引发多种人类恶性肿瘤，例如卡波西肉瘤（Kaposi’s sarcoma, KS）与原发性渗出性淋巴瘤（primary effusion lymphoma, PEL）。当前针对KSHV感染及其相关疾病的治疗手段有时疗效欠佳，因此亟需开发更为高效的抗病毒制剂。作为疱疹病毒家族成员，裂解复制对于KSHV的致病过程与肿瘤发生至关重要。本研究通过使用诱导型KSHV阳性细胞系iSLK.219，建立了高通量筛选模型。随后对包含1280种美国食品药品监督管理局（Food and Drug Administration, FDA）获批药物的化合物库开展筛选，最终鉴定出15种可有效抑制KSHV病毒粒子产生的命中化合物，其中绝大多数此前从未见抗KSHV活性的相关报道。值得注意的是，其中3种药物的靶点为组胺受体或相关信号通路。
本研究数据进一步证实，针对不同组胺受体（histamine receptors, HxRs）的拮抗剂，在诱导后的iSLK.219细胞与BCBL-1细胞中均展现出优异的KSHV裂解复制抑制效果。与之相反，组胺与HxRs的特异性激动剂则可促进诱导后的iSLK.219细胞以及KSHV感染原代细胞的病毒裂解复制。机制研究表明，MAPK与PI3K/Akt下游信号通路是组胺/受体介导的KSHV裂解复制促进过程所必需的。在iSLK.219细胞中直接敲低HxRs，可有效阻断诱导过程中的病毒裂解基因表达。
通过对一组HIV阳性患者的队列样本进行分析，本研究发现KSHV阳性组的血浆与唾液中组胺水平显著高于KSHV阴性组。综上，本研究不仅鉴定出新型抗KSHV制剂，还为阐释宿主因子调控该致瘤疱疹病毒裂解复制与激活的分子机制提供了全新视角。