Discovery of nuclear cavities in Epstein-Barr virus-infected cells.

Approximately 90 % of humans are infected with the Epstein-Barr virus (EBV); however, most do not develop neoplastic lesions. Despite various investigations, the underlying reasons remain largely unknown. Therefore, we aimed to address this question through morphological observations to identify the ultrastructural alterations occurring in EBV-infected cells. EBV-positive cells from legacy lymph node specimens obtained from patients with HIV and modern fresh specimens of aberrantly proliferating human EBV-positive lymphocytes in a patient-derived xenograft (PDX) of immunodeficient mouse were examined. By utilizing a special technique that allowed us to observe exactly the same specimen using both optical and electron microscopy, we were able to detect a peculiar phenomenon in EBV-infected cells. EBV-infected lymphocytes occasionally exhibited nuclear cavities, a finding that was confirmed in multiple specimens from both patients with HIV and the PDX model. It was suggested that EBV-infected cells may activate cell death pathways, based on the protein expression patterns of p53 and FAS. Taken together, these results indicated that nuclear cavity formation appeared to be a characteristic morphological alteration associated with EBV infection. Further research could clarify the potential relationship between nuclear cavities and cellular biology in EBV-infected cells, possibly shedding light on the mechanisms that prevent EBV-infected cells from progressing to tumor formation.