EphA7 Functions as Receptor on BJAB Cells for Cell-to-Cell Transmission of the Kaposi's Sarcoma-Associated Herpesvirus and for Cell-Free Infection by the Related Rhesus Monkey Rhadinovirus

Abstract

Kaposi’s sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi’s sarcoma and is associated with two B cell malignancies, primary effusion lymphoma (PEL) and the plasmablastic variant of multicentric Castleman’s disease. On several adherent cell types, EphA2 functions as a cellular receptor for the gH/gL glycoprotein complex of KSHV. KSHV gH/gL also has previously been found to interact weakly with other members of the Eph family of receptor tyrosine kinases (Ephs), and other A-type Ephs have been shown to be able to compensate for the absence of EphA2 using overexpression systems. However, whether these interactions are of functional consequence at endogenous protein levels has remained unclear so far. Here, we demonstrate for the first time that endogenously expressed EphA7 in BJAB B cells is critical for the cell-to-cell transmission of KSHV from producer iSLK cells to BJAB target cells. The BJAB lymphoblastoid cell line often serves as a model for B cell infection and expresses only low levels of all Eph family receptors other than EphA7. Endogenous EphA7 could be precipitated from the cellular lysate of BJAB cells using recombinant gH/gL, and knockout of EphA7 significantly reduced transmission of KSHV into BJAB target cells. Knockout of EphA5, the second most expressed A-type Eph in BJAB cells, had a similar, although less pronounced, effect on KSHV infection. Receptor function of EphA7 was conserved for cell-free infection by the related rhesus monkey rhadinovirus (RRV), which is relatively even more dependent on EphA7 for infection of BJAB cells.IMPORTANCEInfection of B cells is relevant for two KSHV-associated malignancies, the plasmablastic variant of multicentric Castleman’s disease and PEL. Therefore, elucidating the process of B cell infection is important for the understanding of KSHV pathogenesis. While the high-affinity receptor for the gH/gL glycoprotein complex, EphA2, has been shown to function as an entry receptor for various types of adherent cells, the gH/gL complex can also interact with other Eph receptor tyrosine kinases with lower avidity. We analyzed the Eph interactions required for infection of BJAB cells, a model for B cell infection by KSHV. We identified EphA7 as the principal Eph receptor for infection of BJAB cells by KSHV and the related rhesus monkey rhadinovirus. While two analyzed PEL cell lines exhibited high EphA2 and low EphA7 expression, a third PEL cell line, BCBL-1, showed high EphA7 and low EphA2 expression, indicating a possible relevance for KSHV pathology.

Analysis of KSHV B lymphocyte lineage tropism in human tonsil reveals efficient infection of CD138+ plasma cells

“…Thus, the mechanisms underlying KSHV targeting of plasma cells and other B lymphocyte lineages for infection remains to be established. Studies in lymphoma cell lines have identified ephrin receptors as critical factors in KSHV entry (Großkopf et al, 2019; Muniraju et al, 2019). Thus, our future studies in this area will concentrate on the role of other heparin sulfate proteoglycans and Ephrin family receptors in KSHV infection of tonsillar B lymphocyte lineages.…”

Analysis of KSHV B lymphocyte lineage tropism in human tonsil reveals efficient infection of CD138+ plasma cells

“…Thus, the mechanisms underlying KSHV targeting of plasma cells and other B lymphocyte lineages for infection remains to be established. Additional studies in lymphoma cell lines have identified Ephrin receptors as critical factors in KSHV entry [ 34 , 35 ]. Thus, our future studies in this area will examine Ephrin family receptors in KSHV infection of tonsillar B lymphocyte lineages.…”

Gammaherpesvirus entry and fusion: A tale how two human pathogenic viruses enter their host cells

“…More recent studies suggest that KSHV infection of epithelial cells is independent of αν-and β1-family integrin expression (TerBush et al, 2018), but requires HSPGs and either EphA2, EphA4, or EphA5 (Chakraborty et al, 2012a, Chandran, 2010, Chen et al, 2019, Damania and Cesarman, 2013, Hahn et al, 2012, TerBush et al, 2018. Interestingly, EphA7 has recently been found to be a receptor required for KSHV entry into B cells (Grosskopf et al, 2019). KSHV attachment to its host cells via HSPG and DC-SIGN is predominately mediated by gB and gpK8.1A (Fig.…”