LB5
The Epstein Barr Virus (EBV)-encoded latent membrane protein 2A (LMP2A) and LMP2B attenuate aspects of innate immunity
Khilan Shah, Stephen Murphy
Cancer Research UK Cancer Centre, University of Birmingham, UK
The Epstein Barr Virus (EBV)-encoded latent membrane protein 2A (LMP2A) and LMP2B are frequently expressed in EBV-positive carcinomas (NPC and gastric adenocarcinoma), suggesting that they play an essential role in epithelial cell growth transformation or in the maintenance of the virus-transformed state. Our recent novel findings reveal that these viral proteins modulate aspects of innate immunity in epithelial cells a function attributed to the ability to modulate endosomal/lysosomal activity.
QPCR, Immunofluorescence staining and flow cytometry established that Toll-like Receptor (TLR) expression, namely those involved in viral immune responses (TLR 3, 4 ,7 and 9), is reduced in LMP2A but not in LMP2B-expressing cells. LMP2A-expressing cells were refractory to TLR ) promoterb (IFNbagonist stimulation as assessed by interferon- luciferase reporter activity and EMSA. Although LMP2B failed to attenuate promoter activity, both viral proteins modulated thebTLR-mediated IFN induction of cytokines and IFN-stimulated genes (ISGs) in response to agonist stimulation.
Further, LMP2A and LMP2B-expressing cells showed ) asg and IFNadecreased responsiveness to interferon (IFN assessed by STAT1 phosphorylation and ISRE/GAS luciferase reporter activity and EMSA. Microarray profiling showed that this effect was global, with both viral proteins attenuating the induction of a many ISGs.
Although cell surface interferon receptor (IFNR) levels were unaffected, the rate of IFNR endocytosis and degradation were significantly increased in the presence of LMP2A and LMP2B. A role for endosome acidification has been uncovered with chloroquine, an endosomal acidification inhibitor, blocking the effects on IFNR degradation. Further; the kinetics of endosome acidification, measured by LysosensorTM, are increased in LMP2A and LMP2B expressing cells suggesting that these viral proteins function as proton (H+) pumps or modulate vacuolar ATPase activity.
These findings show that LMP2A and LMP2B target multiple effector pathways involved in innate immune recognition, and that situations may exist during epithelial cell infection where EBV is required to target these pathways to achieve a stable persistent infection.
