Unconjugated
Epstein-Barr virus (EBV) can infect both susceptible B lymphocytes and non-susceptible epithelial cells (ECs). Viral tropism analyses have revealed two intriguing means of EBV infection, either by a receptor-mediated infection of B cells or by a cell-to-cell contact-mediated infection of non-susceptible ECs. Herein, we report a novel "in-cell infection" mechanism for EBV infection of non-susceptible ECs through the formation of cell-in-cell structures. Epithelial CNE-2 cells were invaded by EBV-infected Akata B cells to form cell-in-cell structures in vitro. Such unique cellular structures could be readily observed in the specimens of nasopharyngeal carcinoma. Importantly, the formation of cell-in-cell structures led to the autonomous activation of EBV within Akata cells and subsequent viral transmission to CNE-2 cells, as evidenced by the expression of viral genes and the presence of virion particles in CNE-2 cells. Significantly, EBV generated from in-cell infected ECs displayed altered tropism with higher infection efficacy to both B cells and ECs. In addition to CNE-2 tumor cells, cell-in-cell structure formation could also mediate EBV infection of NPEC1-Bmi1 cells, an immortalized nasopharyngeal epithelial cell line. Furthermore, efficient infection by this mechanism involved the activation of the PI3K/AKT signaling pathway. Thus, our study identified "in-cell infection" as a novel mechanism for EBV infection. Given the diversity of virus-infected cells and the prevalence of cell-in-cell structures during chronic infection, we speculate that "in-cell infection" is likely a general mechanism for EBV and other viruses to infect non-susceptible ECs.
We present the results of a multicenter clinical trial using Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) generated from EBV-seropositive blood donors to treat patients with EBV-positive posttransplantation lymphoproliferative disease (PTLD) on the basis of the best HLA match and specific in vitro cytotoxicity. Thirty-three PTLD patients who had failed on conventional therapy were enrolled. No adverse effects of CTL infusions were observed and the response rate (complete or partial) in 33 patients was 64% at 5 weeks and 52% at 6 months. Fourteen patients achieved a complete remission, 3 showed a partial response, and 16 had no response at 6 months (5 died before completing treatment). At 5 weeks, there was a significant trend toward better responses with higher numbers of CD4(+) cells in infused CTL lines (P = .001) that were maintained at 6 months (P = .001). Patients receiving CTLs with closer HLA matching responded better at 6 months (P = .048). Female patients responded better than male patients, but the differences were not statistically significant. Our results show that allogeneic CTLs are a safe and rapid therapy for PTLD, bypassing the need to grow CTLs for individual patients. The response rate in this poor prognosis patient group is encouraging.
