Porcine lymphotropic herpesviruses BILF1 a major driver of PTLD in mini pigs

Epstein-Barr virus (EBV) is widespread herpesvirus infecting approximately 95% of the adult population worldwide. Under immunosuppression, EBV infection can cause post-transplant lymphoproliferative disease (PTLD), a possibly fatal complication. At present, no relevant animal model to study ?1-herpesvirus-associated PTLD exists due to strict host tropism of the virus. Pigs experimentally develop PTLD, with the ?1-herpesvirus porcine lymphotropic herpesvirus 1 (PLHV1) as a driving factor. Here, we studied properties from BILF1 receptors encoded by three PLHVs (PLHV1-3) in comparison with EBV-BILF1, which has been described as a druggable receptor. BILF1 is a G protein coupled receptor (GPCR) encoded by ?1-herpesviruses. In EBV and Rhesus CeHV15 ?-1herpesvirus, BILF1 downregulates major histocompatibility complex I (MHC-I) molecules, signals constitutively through Gai, and induces cell transformation. We describe the localization, internalization, signalling and immunevasive properties of these receptors and confirmed that PLHV1-3 BILFs share similar localization, constitutive internalization and immune-evasive properties with EBV-BILF1. The downregulation of MHC-I molecules observed for EBV-BILF1 is conserved in PLHV1-3 BILFs expressed in human HEK-293 cells. Further, we show that these vGPCRs are able to elicit constitutive, Gai mediated signalling at the cell surface. However, activation of two downstream transcription factors, NFAT and NF-?B, differs among PLHV1-3 BILFs and indicates potentially different roles for these vGPCRs. To underline the importance of PLHV1 and BILF1 in the PTLD disease onset, we confirm their enhanced expression in samples from experimentally diseased miniature pigs.