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Differential Response of Friend Leukemia Virus and Lactate Dehydrogenase Virus to Chemotherapy and in Vitro Neutralization¹

Viral Leukemia & Lymphoma Branch, National Cancer Institute, National Institutes of Health, and Microbiological Associates, Inc., Bethesda, Maryland 20014

Preparations of pooled Friend virus used in this laboratory were found to contain lactate dehydrogenase (LDH) virus. Interrelationships between these viruses and the effects of drug treatment in vivo and virus neutralization in vitro were studied. Both 6-mercaptopurine and streptonigrin administered to Friend virus-infected mice delayed the onset of the 10- to 100-fold normal elevation of plasma LDH seen in untreated animals. The suppressed LDH levels in the treated mice were accompanied by a three to four log reduction in Friend virus titer. Drug treatment did not reduce the titer of Friend virus-associated LDH virus in mice nor was it effective against a preparation of Riley's LDH virus. A preparation of Friend virus neutralizing antibody was tested for its ability to modify the typical Friend virus LDH response in vivo. A neutralized Friend virus preparation produced LDH levels identical to those of mice inoculated with LDH virus alone, whereas mice receiving non-neutralized Friend virus showed a 90-fold normal elevation of plasma LDH after 14 days. The Friend virus neutralizing antibody preparation, though effective against Friend virus, did not significantly reduce the titer of the LDH virus. The results suggest that chemotherapy and virus neutralization procedures delay or prevent Friend virus replication, but are ineffective against LDH virus. Friend virus was unable to modify the infectivity of the LDH virus.

¹ This investigation was supported in part by NCI Public Health Service Contract PH-43-66-887 at Microbiological Associates, Inc., Bethesda, Maryland. Portions of this work have been presented (9).

Received 6/13/67. Accepted 10/21/67.