Effect of Drying on Certain of the Virus Group. ∗

It has long been known that certain of the virus group such as vaccine and rabies virus will withstand drying but as a rule there is considerable loss in virulence during the process. Murphy 1 showed that the chicken tumor agent was less damaged if the material was kept frozen during desiccation. Harris and Shackell 2 demonstrated that rabies virus frozen and dried lost little of its virulence and, furthermore, the deterioration was less rapid than when the tissues were dried by the usual methods.

The present study deals with the resistance of vaccine virus, virus III and Herpes febrilis virus to freezing and desiccation.†

The various tissues containing the viruses were mixed finely and spread in a thin layer in a sterile dish. This was placed in a vacuum jar over concentrated sulphuric acid and the pressure reduced to 5.0 mm. of mercury. The jar was immediately put in a freezing room at a temperature of −5.0° C. and left for 2 days. The tissues, thoroughly desiccated by this time, were removed, rubbed to a powder in a mortar and sifted through a fine meshed sieve to remove the larger particles. For the infectivity test the powder was taken up in Locke's solution and injected in the usual manner for the individual virus.

Vaccine virus, after the above treatment, when tested dermally and intradermaliy in normal rabbits, showed that the activity of the virus was practically unimpaired. The lesions produced arose as promptly and were almost as extensive as those produced by the control injections of fresh vaccine virus.

Virus III after drying in the frozen state proved almost as potent as the fresh virus in the production of the typical testicular lesions in rabbits.

Herpes febrilis vaccine subjected to the freezing and drying produced the typical Herpes febrilis reaction in rabbits, killing the animals in 5 days. The brains showed very many typical eosin-staining nuclear inclusions.