Effect of Cysteine on the Survival of Vaccine Virus

Abstract

It is well known that ultramicroscopic viruses rapidly lose their power to infect when kept at 37° C., and become wholly inactive in a few days. If the viruses, however, are placed under anaerobic conditions, they maintain activity for a longer period of time.

The following experiments were made with neurovaccine virus for the purpose of noting the effects of an active reducing agent, cysteine hydrochloride.

The virus was derived from infected rabbits' testicles and suspensions of the tissue were prepared in Ringer's solution, distilled water, and veal-infusion broth, the final dilutions being 1:50. Twenty tubes each containing 10 cc. of the respective suspensions were prepared and to each was added sufficient cysteine hydrochloride adjusted to pH = 7.5 to make a 1:2,000 dilution of the chemical. A similar series of tubes without cysteine completed the series. All tubes were sealed with petrolatum and kept at 37° C.

After 7, 14, 21, 32, 42, 54, and 83 days, the material was tested for activity by the inoculation of different dilutions into the shaved skin of rabbits. The effect of the cysteine on the survival of the virus is shown in the table:

It follows, therefore, that cysteine hydrochloride definitely favors the survival of vaccine virus at 37° C, and the broth vehicle prolongs the period of viability to a greater degree than either Ringer's solution or distilled water.