Humoral response to recombinant interferon-alpha 2b in patients receiving recombinant interferon-alpha 2b therapy

Twenty-seven patients in the chronic phase of a Philadelphia chromosome-positive chronic myelogenic leukemia (CML) underwent a monotherapy with recombinant interferon-alpha 2b (rIFN-alpha 2b), receiving a mean dose of 3 x 5 Mio. IU per week. Eight of the 27 patients developed both rIFN-alpha 2b-binding and -neutralizing antibodies during therapy. Sera of these patients abrogated both antiviral and antiproliferative activities of rIFN-alpha 2b, but not of nIFN-beta or rIFN gamma. Only one serum neutralized nIFN-alpha. The IFN binding and neutralizing titers rose during therapy, while a decrease occurred over months after cessation of therapy. The IgG fraction obtained by DEAE chromatography contained more than 90% of the IFN-neutralizing capacity of the purified sera. This result strongly suggested that IgG antibodies are responsible for the IFN-alpha-neutralizing activity.