INCREASED BINDING-ACTIVITY OF MEASLES-VIRUS TO MONKEY RED-BLOOD-CELLSAFTER LONG-TERM PASSAGE IN VERO CELL-CULTURES

Recent field isolates of measles virus (MV) obtained by using B95-8 ce lls have been reported not to agglutinate African green monkey red blo od cells (AGM-RBC). Vero cell-adapted, plaque-forming strains derived from three field isolates at the third passage in Vero cell cultures ( T8Ve-3, T11Ve-3 and N13Ve-3) also exhibited markedly decreased binding activity, as determined by infectivity-absorption and haemadsorption tests. On the other hand, binding activity of the respective strains a t the twentieth passage (T8Ve-20, T11Ve-20 and N13Ve-20) increased to practically the same level as that of the Edmonston strain, a standard strain of MV passaged long-term. A membrane immunofluorescence test r evealed that the decreased binding activity to AGM-RBC of T8Ve-3, T11V e-3 and N13Ve-3 was not due to decreased expression of the haemaggluti nin (H) protein on the cell surface. The deduced amino acid sequence o f the H protein synthesized in T11Ve-3-infected cells was identical to that in T11Ve-20-infected cells, although a single amino acid alterat ion was observed when T8Ve-3 was compared with T8Ve-20. Similarly, app roximately half of the N13Ve-20-infected cells synthesized an H protei n identical to that produced in N13Ve-3-infected cells, and neverthele ss, exhibited markedly increased haemadsorption. The present results s uggest that a viral protein(s) other than the H protein contributed to the binding activity of MV to AGM-RBC.