LOSS OF IMMUNOGENIC PROPERTIES OF VACCINIA VIRUS INACTIVATED BY FORMALDEHYDE

Abstract

In the experiments here reported, vaccinia virus in the form of partly purified elementary body suspensions was exposed to 0.006 M formaldehyde in the presence of 0.02 M glycine at 20–24 °C. Samples were taken at intervals to determine the rate of inactivation. Assays were carried out by intracutaneous inoculation of rabbits and by the plaque count method in monkey kidney cell monolayers. In addition, the virus suspensions so treated were injected into rabbits and the resulting immune response was studied by serum–virus neutralization tests performed on the rabbit skin and in tissue cultures.It was found that the rate of inactivation by HCHO decreased with time in accordance with the usual dynamics of disinfection. Similarly, the immunogenic properties decreased in proportion to the fall in infectivity. Minimal quantities of virus could still be detected after 150–250 hours; and samples removed at these times were capable of producing a feeble immune response. Later samples were neither infective nor immunogenic. These experiments lend no support to the belief that HCHO-inactivated vaccinia virus could be employed as a substitute for living virus in immunization against smallpox.