Recently, we found that several lymphotropic wild-type isolates of measles virus (MV) did not lead to the downregulation of CD46 following infection. We hypothesized that either the site of virus isolation, e.g., throat swab versus peripheral blood mononuclear cells, or the cell type used for the isolation may exert selective pressure on a mixed population of viruses, resulting in isolates with the differential properties observed. This hypothesis has been tested by simultaneously isolating MV from a throat swab and peripheral blood mononuclear cells from a single patient by cultivation on B95 and Vero cells. We report that neither the source of MV nor the cell type used for isolation directly influenced the capacity for CD46 modulation of these MV isolates.