Comparison of the biologic effects of two recombinant human interferons alpha (rA and rD) in humans

IFN-alpha (rD) was investigated to determine the relationship between antiviral activity in vitro and the modulation of biologic effects in vivo. Eight patients with malignancy were given 15 and 45 micrograms weekly injections of IFN-alpha (rA) and IFN-alpha (rD). The frequency of side effects was much lower with IFN-alpha (rD) injections. This was objectively documented both in incidence of side effects (20 versus 45, p less than 0.01) and mean maximum temperature (1 degree C lower with IFN-alpha (rD), p less than 0.002). A bovine cell line, MDBK, was used to measure interferon concentrations in the serum. Geometric mean peak titers and time-to-peak titers were similar with the two recombinant interferon preparations. Although IFN-alpha (rD) has relatively less antiviral activity on human cells, its effect on the total granulocyte count, natural killer (NK) cell cytotoxicity, and 2'5'-A activity was comparable to IFN-alpha (rA). Mean NK cell percent specific 51Cr release was enhanced by both interferons (after 15 micrograms doses, mean percent NK cell cytotoxicity IFN-alpha (rD) preinjection, 10.5% +/- 2.3%; post-injection, 27.2% +/- 4.5%; IFN-alpha (rA), preinjection, 14.4% +/- 3.2%, postinjection, 25.1% +/- 5%). Species-specific antiviral activity of an interferon does not necessarily predict other biologic properties following in vivo administration.