Abstract
Berry, 1 Hoffstadt, 2 and Hurst 3 have reported the transformation of fibroma virus into myxoma virus employing crude tissue suspensions of myxoma virus. Meck 4 and Hyde 5 were unable to confirm these observations. Recently Gardner and Hyde 6 have accomplished the transformation with 3 of 7 elementary body suspensions of myxoma virus. Hurst 3 has obtained positive results in 5 of 7 rabbits and Hoffstadt 2 in 7 of 20. The purpose of the experiments here reported was to amplify these observations and to study factors which might account for the inconsistent results.
A 10% suspension of a dermal tumor of virulent myxoma virus was heated for 35 min at 60°C in a water-bath, then kept in sealed ampoules at 4°C until used. This tissue suspension of heat-inactivated myxoma virus was submitted to the following procedures:
1. Serial testicular passage.
2. Mixture with (a) active fibroma virus, (b) attenuated fibroma virus, (c) agents producing reduction, inflammation, increase in virulence; and subsequent testicular injection or serial passage of these mixtures.
Serial testicular passage was performed by removing the inoculated testicle 7 days after injection. This testicular tissue was triturated; portions of a 10% suspension were mixed with heat-inactivated myxoma virus and injected into the testicle of another rabbit.
Two sets of experiments were performed at separate times with freshly prepared heatinactivated myxoma virus. New Zealand rabbits weighing approximately 4 1/2 lb were used throughout the experiments, and they were kept in isolated cages to prevent possible cross-infection. Temperature readings and observations were made daily.
Experiment I
Group 1. 1cc of heat-inactivated myxoma virus passed serially through 3 rabbits.
Group 2. 1cc of heat-inactivated myxoma virus plus 0.5 cc of active fibroma virus passed serially through 3 rabbits.
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