Humoral
antibodies and a certain degree of resistance to
infection with
vaccinia, probably not enduring, are produced in rabbits by the repeated
injections of inactive formolized (0.3 per cent) elementary bodies of
vaccinia and virus-free filtrates of dermal
vaccine virus. Single
injections of large amounts of elementary bodies are not as effective as similar amounts administered in small repeated doses. Drastic treatment (10 per cent
formaldehyde or boiling for 2 hours) almost completely alters or destroys the antigenicity of elementary bodies. It appears that the production of
precipitins and
agglutinins does not parallel that of
neutralizing antibodies and that the mere presence of such
antibodies in the serum of a rabbit as the result of
injections of inactive elementary bodies does not necessarily indicate that the animal possesses a great degree of resistance to
infection with a potent
vaccine virus. The fact that some
neutralizing antibodies appeared in the sera of rabbits that had received
injections of inactive elementary bodies can be interpreted as indicating that at least not all
neutralizing antibodies for
vaccine virus are the result of a reaction to an
antigen produced by the host in consequence of a vaccinal
infection. No evidence was obtained to show that elementary bodies inactivated by our methods (0.3 per cent
formaldehyde) would serve as a suitable
vaccine for the protection of human beings against
smallpox.