Measles virus infection of B lymphocytes permits cellular activation but blocks progression through the cell cycle

Measles virus infection of unstimulated B lymphocytes suppresses both proliferation and differentiation into immunoglobulin-secreting cells. However, mitogenic stimulation of these infected cells results in cell volume enlargement, rapid RNA synthesis, and the expression of cell surface activation antigens 4F2, HLA-DS and transferrin receptor. The cellular genes c-myc and histone 2B are induced during early G₁ and S phase of the cell cycle, respetively, and viral RNA synthesis can be detected during this interval. However, total RNA synthesis is decreased at 48 h after stimulation, and the histone 2B RNA steady-state level at 48 h is fivefold less than that in uninfected cells. This sequence of events defines an arrest in the G₁ phase of the cell cycle in measles virus-infected B cells.