Abstract
It is generally accepted that immunity to virus diseases can only be produced by an infection with a live, even though highly attenuated, virus. From time to time experimental evidence contrary to this view has been published, but the results have not been convincing. In this preliminary report references may be limited to experiments with vaccine virus. Gordon 2 used virus heated to 57°C. for 30 minutes, a period insufficient to kill this virus. Hunt and Falk 3 reported positive results with virus treated with a weak solution of formalin, but Olitsky and Long 6 showed that vesicular stomatitis virus thus treated still contained live virus. The most careful work has been carried out by Bland, 1 who tested his vaccine for live virus and used both heat and formalin killed virus. He reported positive results in guinea pigs and equivocal results in rabbits.
The results obtained by Bland, as well as our own observation 4 , 5 on the antigenic nature of purified phage and of typhus rickettsia in cultures, suggested that the failure to induce immunity with dead virus was due to the relatively small amount of antigen contained in tissue suspensions of viruses. In the phage work it was found that an amount of suspension containing not less than 20 million plaques was necessary to produce an antiserum with moderate neutralizing power. In the case of rickettsia it was estimated that an infected guinea pig brain weighing 3 gm. would have a maximum only of 12,000,000 organisms, and this seemed sufficient reason why infected lice or cultures made an efficient vaccine, whereas, a whole guinea pig brain produced at best only a slight degree of immunity.
The experiments reported below were undertaken in order to test the validity of this view in regard to vaccine virus.
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