Significant Differences in Therapeutic Responses to a Human Interferon-αB/D Hybrid in Rauscher or Friend Murine Leukemia Virus Infections

Treatment of mice infected with Rauscher (RMLV) or Friend (FMLV) murine leukemia viruses at an early stage of disease (beginning at day 0 and continuing every other day for 21 days) with 5 × 10⁷ units/kg body weight of a cross-species-active recombinant human interferon-αB/D hybrid (rHuIFN-αB/D) was more effective in FMLV than in RMLV infections. In contrast, treatment with 5 × 10⁷ units/kg body weight of IFN beginning as late as 15 days postinfection and continuing every other day for 21 days was more elective in RMLV than in FMLV infections. These differences were consistent with observed changes in circulating white blood cells, spleen weight, and reverse transcriptase levels. Additionally, biweekly long-term administration (beginning at day 0) of 5 × 10⁶ units/kg of rHuIFN-αB/D (an ineffective treatment in short-term therapy) significantly prolonged the mean survival time of RMLV-infected mice, but only weakly prolonged that of FMLV-infected mice.