A Mechanism-Based Targeted Screen To Identify Epstein-Barr Virus-Directed Antiviral Agents

Abstract

Epstein-Barr virus (EBV) is one of nine human herpesviruses that persist latently to establish permanent residence in their hosts. Periodic activation into the lytic/replicative phase allows such viruses to propagate and spread, but can also cause disease in the host. This lytic phase is also essential for EBV to cause infectious mononucleosis and cancers including B lymphocyte-derived Burkitt lymphoma and immunocompromise-associated lymphoproliferative diseases/lymphomas as well as epithelial cell-derived nasopharyngeal-cell carcinoma. In the absence of anti-EBV agents, however, therapeutic options for EBV-related diseases are limited. In earlier work, we discovered that, through the activities of the viral protein kinase that is conserved across herpesviruses and two cellular proteins ATM and KAP1, a lytic cycle amplification loop is established – and that disruption of this loop disables the EBV lytic cascade. We therefore devised a high throughput screening assay, screened a small molecule compound library, and identified seventeen candidates that impair the release of lytically-replicated EBV. The identified compounds will i) serve as lead compounds or may be modified to inhibit EBV and potentially other herpesviruses and ii) be developed into anti-cancer agents as functions of KAP1 and ATM are tightly linked to cancer. Importantly, our screening strategy may also be used to screen additional compound libraries for anti-herpesviral and anti-cancer drugs. IMPORTANCE Epstein-Barr virus, which is nearly ubiquitous in humans, is causal to infectious mononucleosis, chronic active EBV infection, and lymphoid and epithelial cancers. However, EBV-specific antiviral agents are not yet available. To aid in the identification of compounds that may be developed as antivirals, we pursued a mechanism-based approach. Since many of these diseases rely on EBV's lytic phase, we developed a high-throughput assay that is able to measure a key step that is essential for successful completion of EBV's lytic cascade. We used this assay to screen a library of small molecule compounds and identified inhibitors that may be pursued for their anti-EBV and possibly even anti-herpesviral potential as this key mechanism appears to be common to several human herpesviruses. Given the prominent role of this mechanism in both herpesvirus biology and cancer, our screening assay may be used as a platform to identify both anti-herpesviral and anti-cancer drugs.