INHIBITION OF THE LESIONS OF PRIMARY VACCINIA AND OF DELAYED HYPERSENSITIVITY THROUGH IMMUNOLOGICAL TOLERANCE IN RABBITS

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Abstract
Further experimental observations are described which support the hypothesis that the vesicular skin lesion of primary vaccinia virus infection is due to allergy. The method of tolerance was used to abolish the immunological responses of neonatal rabbits by injecting each with 0.5 mg of purified inactive virus. These animals and nontolerant controls were inoculated into a skin site with vaccinia virus three days later. Most of the controls developed typical vaccinial lesions in 2-3 days and subsequently developed delayed hypersensitivity to inactive virus by the 7th postinfection day. The 19 tolerant animals failed to develop typical vaccinial lesions over the period of observation. They also failed to develop hypersensitivity to the inactive virus. Approximately 2/3 of the tolerant rabbits died between the 4th and 10th postvaccination day with generalized vaccinia infection. The data strongly suggest that a state of immunological tolerance was successfully produced with the virus of vaccinia. The rapid spread of virus from the local site of inoculation to internal organs indicates a failure of immunity also. The observations are consistent with the concept that the tolerant animals died as a result of the toxic effects of the virus.