Interaction between Viruses and Platelets: Requirement of Haemolytic Activity for Platelet Aggregation Induced by Paramyxoviruses

Summary Newcastle disease virus (NDV) or Sendai virus added to washed suspensions of rabbit or human platelets induced a brisk platelet aggregation (P.A.) response concomitant with release of biologically active components from storage granules (platelet release reaction, P.R.). NDV which had been rendered non-infectious by u.v. irradiation for 5 min retained its capacity to induce P.A. and P.R. and to agglutinate or lyse erythrocytes. Treatments of paramyxoviruses (heating at 56 °C; disruption by Tween 80/ether) which resulted in loss of haemolytic activity also eliminated P.A. and P.R. reactions but had little or no effect on virus haemagglutinating properties. A non-haemolytic virus, influenza A2, had no detectable effect on platelets when used at a concentration having a haemagglutination titre equivalent to that of platelet-aggregating doses of NDV or Sendai virus. It was concluded that the properties of paramyxoviruses responsible for causing lysis of erythrocytes were required for induction of P.A. and P.R. reactions. In this respect, the virus-induced platelet responses may be similar to other cellular reactions to paramyxoviruses such as fusion of cell membranes and development of cytotoxic or cytopathic changes.