Expression of HSV-1 Receptors in EBV-Associated Lymphoproliferative Disease Determines Susceptibility to Oncolytic HSV

Epstein-Barr virus (EBV)-associated B cell lymphoproliferative disease (LPD) after hematopoietic stem cell or solid organ transplantation remains a life-threatening complication. Expression of the virus-encoded gene product, EBER, has been shown to prevent apoptosis via blockade of PKR activation. Because PKR is a major cellular defense against Herpes simplex virus, and oncolytic HSV-1 (oHSV) mutants have shown promising anti-tumor efficacy in preclinical models, we sought to determine whether EBV-LPD cells are susceptible to infection by oHSVs. We tested three primary EBV-infected lymphocyte cell cultures from neuroblastoma (NB) patients as models of naturally acquired EBV-LPD. NB12 was most susceptible, NB122R was intermediate, and NB88R2 was essentially resistant. Despite EBER expression, PKR was activated by oHSV infection. Susceptibility to oHSV correlated with the expression of the HSV receptor, nectin-1. The resistance of NB88R2 was reversed by exogenous nectin-1 expression, whereas down-regulation of nectin-1 on NB12 decreased viral entry. Xenografts derived from the EBV-LPDs exhibited only mild (NB12) or no (NB88R2) response to oHSV injection, compared with a neuroblastoma cell line that showed a significant response. We conclude that EBV-LPDs are relatively resistant to oHSV virotherapy, in some cases due to low virus receptor expression but also due to intact anti-viral PKR signaling.