Abstract
Epstein-Barr virus (EBV) infection is strongly associated with nasopharyngeal carcinoma, a common cancer in Southeast Asia and certain regions of Africa. However, the dynamics of EBV episome maintenance in infected nasopharyngeal epithelial (NPE) cells remain largely undefined. Here, we report the establishment of a highly efficient cell-free EBV infection method for NPE cells. By using this method, we have defined some of the dynamic events involved in the early stage of EBV infection in NPE cells. We report, for the first time, a rapid loss of EBV copies from infected NPE cells during the first 12-72 h post-infection. The rate of EBV loss slowed at later stages of infection. Live cell imaging revealed that the freshly infected NPE cells were delayed in entry into mitosis compared with uninfected cells. Freshly infected NPE cells transcribed significantly higher levels of lytic EBV genes BZLF1 and BMRF1 yet significantly lower levels of EBER1/2 than stably infected NPE cells. Notably, there were very low or undetectable levels of protein expressions of EBNA1, LMP1, Zta and Rta in freshly infected NPE cells, whereas EBNA1 and LMP1 proteins were readily detected in stable EBV-infected NPE cells. The kinetics of EBV loss and the differential EBV gene expression profiles between freshly and stably infected NPE cells are in line with the suggestion of epigenetic changes in the EBV genome that affect viral gene expression and the adaptation of host cells to EBV infection to maintain persistent EBV infection in NPE cells.
Highlights
Nasopharyngeal carcinoma (NPC) is prevalent in Southeast Asia and certain regions of Africa, with a high incidence in southern China including Hong Kong [1]
We examined the potential of different cytokines to enhance the efficiency of cell-free Epstein–Barr virus (EBV) infection of nasopharyngeal epithelial (NPE) cells
The development of a highly efficient cell-free EBV infection method in NPE cells allowed us to examine the early dynamic events involved in EBV infection of NPE cells without the contamination of B cells, for the first time
Summary
Nasopharyngeal carcinoma (NPC) is prevalent in Southeast Asia and certain regions of Africa, with a high incidence in southern China including Hong Kong [1]. Clonal EBV infection has been found in pre-invasive lesions of the nasopharynx, suggesting that the focal deregulated cellular growth may arise from clonal expansion of a single EBV-infected premalignant nasopharyngeal epithelial (NPE) cell, supporting a role for EBV infection in the early process of NPC development [2]. The early events involved in infection of premalignant NPE cells have been difficult to investigate and remain largely unknown. The EBV-producing Akata cells establish tight junctional conjugates with the co-culturing epithelial cells and are difficult to separate from epithelial cells after co-culture. The association of EBV-producing Akata cells with the infected epithelial cells prevents accurate investigation of early events of EBV infection in epithelial cells, such as profiles of EBV gene expression and dynamics of EBV copy number changes in freshly infected epithelial cells.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
