Summary
The flocculation of vaccinial virus-skin suspensions by homologous antiserum noted by Gordon (5) and utilized by Burgess et al. (4) in the diagnosis of variola has been readily confirmed. The same antigens were also flocculated by immune sera against vaccinial brain and testicle tissues but not by sera from rabbits immunized against normal skin, normal brain, normal testicle, or streptococcal skin tissue. The sera from rabbits recovered from extensive vaccinial skin infections did not flocculate the virus-skin suspensions. Control antigens of normal skin and streptococcal skin suspensions were not flocculated by sera which caused marked flocculation of the virus-skin suspensions. Calf lymph and crusts from skin lesions of a small pox case were flocculated readily by antisera against the rabbit viruses. Brain and testicle virus suspensions, although they produced potent flocculating sera, were found to be unsuitable antigens for demonstrating the specific flocculation.
There is a well marked correlation between the flocculating and neutralizing titers of the various antisera, although occasionally the neutralizing titer may be quite high in the absence of any flocculating power.
The flocculating antibodies are specifically absorbed by the virus-skin suspensions and it is indicated, but by no means proved, that they are also absorbed by the non-flocculable virus brain and virus testicle antigens.