In vitro model for lytic replication, latency, and transformation of an oncogenic alphaherpesvirus

Significance Marek’s disease virus (MDV) serves as a versatile small-animal model for herpesvirus-induced oncogenesis. Infection of target cells in vitro was impossible due to the short-lived nature of B and T cells, and analysis of infected cells ex vivo was hampered by their low frequencies. To overcome these limitations, we established an in vitro system that allows infection of target cells with MDV using stimuli that prolong the survival of B and T cells. Our system recapitulates the situation in vivo, including transformation of T cells in vitro. In the future, our system will facilitate the analysis of viral and cellular factors that promote lytic replication, establishment of latency and transformation, processes ultimately resulting in deadly lymphomas in the natural host. Marek’s disease virus (MDV) is an alphaherpesvirus that causes deadly T-cell lymphomas in chickens and serves as a natural small animal model for virus-induced tumor formation. In vivo, MDV lytically replicates in B cells that transfer the virus to T cells in which the virus establishes latency. MDV also malignantly transforms CD4+ T cells with a T ᵣₑg signature, ultimately resulting in deadly lymphomas. No in vitro infection system for primary target cells of MDV has been available due to the short-lived nature of these cells in culture. Recently, we characterized cytokines and monoclonal antibodies that promote survival of cultured chicken B and T cells. We used these survival stimuli to establish a culture system that allows efficient infection of B and T cells with MDV. We were able to productively infect with MDV B cells isolated from spleen, bursa or blood cultured in the presence of soluble CD40L. Virus was readily transferred from infected B to T cells stimulated with an anti-TCRα Vβ ₁ antibody, thus recapitulating the in vivo situation in the culture dish. Infected T cells could then be maintained in culture for at least 90 d in the absence of TCR stimulation, which allowed the establishment of MDV-transformed lymphoblastoid cell lines (LCL). The immortalized cells had a signature comparable to MDV-transformed CD4+ α/β T cells present in tumors. In summary, we have developed a novel in vitro system that precisely reflects the life cycle of an oncogenic herpesivrus in vivo and will allow us to investigate the interaction between virus and target cells in an easily accessible system.