The multiplication of influenza virus: II. Multiplicity reactivation of ultraviolet irradiated virus

Abstract

The inactivation of influenza virus by ultraviolet light is a one-hit process. Multiple infection of cells with irradiated preparations leads to the production of virus. These preparations do not contain sufficient residual active virus to account for this yield. The amount and the quality (as indicated by ID 50:HA ratio) of the virus produced depends on the degree of irradiation and the number of irradiated particles per cell. Response curves of the cooperative type are obtained indicating that multiplicity reactivation is occurring. Multiplicity reactivation of influenza virus appears to be a very efficient process, and no strain differences were detected. The predictions of the recombinational theory of multiplicity reactivation, proposed by Luria and Dulbecco (1949) for a unit number of six agree well with the observed data, except that maximum yields for the experimental system are never obtained under conditions of reactivation. Incomplete virus formation occurs under conditions of multiplicity reactivation. There is no evidence of an incomplete virus gradient under these conditions. As the irradiation dose increases, the quality of progeny produced on reactivation progressively deteriorates, until an irradiation dose is reached at which only noninfectious hemagglutin is produced, and beyond which reactivation ceases.