Effect of busulfan on oncornavirus-like activity in platelets and chromosomes in polycythemia vera and essential thrombocythemia.

The effect of busulfan therapy on the activity of oncornavirus-like particles and chromosome patterns in patients with polycythemia vera and essential thrombocythemia was studied. Three patients had pretreatment platelet counts greater than 1 million/microliter, abnormal bone marrow karyotypes, and electron microscopic and biochemical evidence of oncornavirus. The results demonstrated that in all 3 patients virus-like particles and reverse transcriptase-like activity could no longer be found in the platelets within 2-4 weeks after the initiation of busulfan treatment. The platelet count was still elevated at this point for each patient, although the count returned to normal levels within 2-3 weeks after virus-like activity was no longer detectable. The chromosome patterns, characterized by aneuploidy (30-50%) before treatment, improved after therapy.