The experimental transformation of variola to vaccinia

Abstract

1. The more recent literature on the experimental methods employed in variola or alastrim-vaccinia variation is reviewed and briefly discussed.2. An account is given of attempts to produce a vaccinia variant from variola of the virulent type and a successful result, by employing the method of intratesticular passage, has been described.3. The reasons for accepting this as a genuine variation and not a vaccinial contamination are discussed.4. An attempt has been made to analyse some possible factors underlying the discrepancies in the literature, and a plea is made for more co-operation in future work on the subject.

Experimental studies on transformation of the variola virus into the vaccinia virus

“…This was the route used by Horgan (25) when he succeeded in the latest transformation of the variola virus into vaccinia virus. We therefore repeated Horgans experiments twice, with primary variola material (Bombay strain), with variola virus from the first monkey passage and with alastrim virus from egg passages.…”

Spontaneous mutation of cowpox-virus by means of eggpassage

“…The initial plan was to copy the method of Horgan(1938) in an attempt to obtain a mutation of variola and of cowpox to vaccinia-virus and so to inoculate the chorio-allantoic membrane of the developing chick embryo after every monkey or rabbit passage and search for the earliest appearance of lesions typical for vaccinia.…”

“…It has repeatedly been claimed that vaecinia may ~ be derived from variola after a number of monkey passages and several rabbit passages (Horgan, 1938). It has repeatedly been claimed that vaecinia may ~ be derived from variola after a number of monkey passages and several rabbit passages (Horgan, 1938).…”

8. Development of a stable smallpox vaccine Collier L. J Hyg 1955; 53: 76–101

“…Significant papers on poxviruses published by the journal include : what became standard methods for the titration of virus [1] and neutralizing antibody [2] ; analysis of the immune response to smallpox and vaccination [3] ; details of the simplest biological method for differentiating orthopoxvirus species, by determining their maximum temperature of growth [4] ; a series of four papers in 1969 (67 : 603-630) in which the results of laboratory investigations contributed to our understanding of the clinical features and epidemiology of smallpox ; proof that bankvoles and woodmice are the reservoir hosts of cowpox virus [5]. Rather less auspicious was publication of probably the last claim to have transformed variola virus into vaccinia virus [6].…”