Studies on the Antigenic Properties of the Ultraviruses

Abstract

Summary and Conclusions Specific neutralizing antibodies were easily demonstrable in the sera of rabbits immunized with active bacteriophage suspensions. The concentration of antiphagic antibodies at a given time and under otherwise similar conditions seemed to be somewhat influenced by the race of bacteriophage employed and by the species of bacteria at the expense of which a particular race of bacteriophage was regenerated. The concentration of the antibodies in the antiphagic serum may also be determined to some extent by the varying responsiveness of individual animals, but the degree to which this is actually true remains to be determined. The neutralizing antibodies formed against the bacteriophages are highly specific in their action. Against some races the specificity of the antiserum may be so marked that it will neutralize only the strictly homologous lysates, leaving the same bacteriophage when propagated at the expense of another species of bacteria entirely untouched.11 Heat-, trypsin-, and methylene blue-inactivated bacteriophage suspensions failed to stimulate the production of neutralizing antibodies. On the other hand, formalin-inactivated bacteriophages continued to exhibit antigenic properties. So far as we were able to determine by serial passages, the formalin-inactivated suspensions no longer contained any residue of active corpuscles to account for the antigenic action here, though it is by no means clear that formalin actually kills or effaces the identity of the virus. The neutralizing properties of the antiphagic sera were gradually lost on exposure to higher temperatures, the rate depending upon the degree of temperature and length of exposure. While a slight diminution in the neutralizing action was noted after an exposure at 56°C. for one-half hour, an exposure at 80°C. for one hour was found necessary to render the antisera completely inactive. Well defined neutralizing action was still noted after an exposure to 75°C. for one-half hour. Neutralization of the bacteriophage by specific antiserum was found to take place slowly, more time being required with the higher than with the lower serum dilutions. In the higher dilutions complete neutralization was not realized until about the eighth day in tests carried out at 32°C. The rate of neutralization was appreciably influenced by the temperature at which the mixtures of serum and bacteriophage were exposed, being much more rapid at higher than at lower temperatures. The addition of fresh guinea pig complement to the various serum dilutions failed to enhance the neutralizing capacity of given antisera. No evidence could be elicited to show that the bacteriophage per se is capable of stimulating the production of specific complement fixing or precipitating antibodies. The above results, especially when considered with the general trend of the observations of earlier investigators, seem to indicate quite emphatically that the antigen-antibody reaction here in its fundamental behavior closely parallels that which takes place in toxin-antitoxin mixtures. This does not, however, as some are inclined to believe, indicate necessarily that the reactions in the two instances are identical, nor that because of this general resemblance, the bacteriophage must necessarily be a toxin or a ferment.