Effect of Vaccinia Virus on Malignant Melanoma of Hamsters

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In 1960 one of us reported his observations on the ameliorative effects of vaccinia virus in the treatment of the cutaneous metastases of malignant melanoma.1 Since that time, the observations have been substantiated by the studies of Belisario and Milton.2 Because of the striking clinical improvement in some of the patients so treated, it seemed appropriate that elucidation of the mode of action and the effectiveness of vaccinia virus therapy be attempted experimentally. The results of the investigation are the basis of this report.

Materials and Methods

Eighty-eight Golden Syrian hamsters, each weighing more than 100 gm., were inoculated with the viable neoplastic cells from a spontaneous malignant melanoma of hamsters. The animals were separated into four groups: group 1—25 animals were inoculated with a suspension of neoplastic cells; group 2—25 were inoculated with a mixture of neoplastic cells and live vaccinia virus; group 3—28 were inoculated with a mixture of neoplastic cells and killed vaccinia virus; group 4—10 were vaccinated before inoculation with neoplastic cells.

The neoplastic inoculum was prepared by finely mincing fresh tumor removed from a donor animal, passing it through a cytosieve, and suspending the resultant minced tumor in Hanks’ balanced salt solution. Approximately 1 gm. of wet neoplastic tissue suspended in 4 ml. of Hanks’ balanced salt solution made a satisfactory inoculum. For those animals receiving either live or killed virus and neoplastic cells, neoplastic cells were immediately mixed with the fresh vaccinia virus from sealed capillary glass tubes; or with. . .



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