Alicia V. Palleroni

Incidence and clinical significance of neutralizing antibodies in patients receiving recombinant interferon alfa‐2a by intramuscular injection

More than 1600 patients with neoplastic disorders have received recombinant human interferon alfa‐2a (Roferon®‐A, Hoffmann‐La Roche, Nutley, NJ) as part of ongoing or completed clinical trials. In this report, the efficacy of interferon alfa‐2a therapy was compared with the incidence of antibodies to this interferon in 617 patients who received the drug by intramuscular administration. Antibody measurements were performed using a highly sensitive enzyme immunoassay, and an interferon antiviral neutralization bioassay. Partial or complete remission occurred in 28% (43 of 152) of the antibody‐positive patients, and in 24% (112 of 465) of the antibody‐negative patients (P = 0.33). The highest incidence of antibody formation occurred among patients with renal cell carcinoma and acquired immune deficiency syndrome (AIDS)‐related Kaposis sarcoma (44% and 34%, respectively). Both the duration of treatment and length of survival were significantly longer for antibody‐positive than for antibody‐negative patients. No significant intergroup differences emerged for response rates or for time to onset or duration of therapeutic response. When results from the above assays were compared to those used for the detection of antibodies to recombinant interferon alfa‐2b (Intron A®, Schering‐Plough Inc., Kenilworth, NJ), the immunoradiometric assay method was determined to be seriously deficient for determination of antibody incidence. This decreased assay sensitivity may account for the reportedly lower incidence of antibodies to recombinant alfa‐2b interferon.

ANTIBODIES TO HUMAN LEUCOCYTE INTERFERONS IN CANCER PATIENTS

During the course of clinical investigation of partly purified human leucocyte interferon (IFN) prepared at the Finnish Red Cross (PIF), neutralising IgG antibodies to human leucocyte IFN were detected in the sera of 3 patients with cancer. In 2 of these patients, the antibodies were detected in serum before treatment with PIF. In the third patient antibodies developed during the course of treatment. Antibody titres against six recombinant human leucocyte IFN sub-types and one recombinant hybrid human leucocyte IFN were different in the 3 patients.

Normal Human Keratinocytes Contain an Interferon-like Protein That May Modulate Their Growth and Differentiation

Epidermal growth and differentiation is a complex process which depends upon a balance between positive and negative growth signals, and in normal skin the majority of the cells in the germinative basal layer do not proliferate unless stimulated. Using the indirect immunofluorescent method, it can be demonstrated that purified polyclonal epidermis in cross sections of normal skin and to the basal layer of cultured keratinocyte colonies. Furthermore, extracts of keratinocyte cultures contain interferon bioactivity. With Western blot analysis, antibodies to interferon recognize a band of approximately 40 kD both in keratinocyte lanes and in recombinant interferon lanes that give in addition a band of approximately 20 kD. Addition of interferon to rapidly growing keratinocytes inhibits their growth by as much as 90% and promotes their terminal differentiation. The growth inhibitory effect of interferon is completely reversible. These data demonstrate that interferon or a closely related protein is present in human epidermis and suggest that this protein may act as a physiologic modulator of keratinocyte growth and differentiation.

A rapid and efficient method for establishing peritoneal macrophage cell lines

Inoculation of the murine J2 retrovirus into the peritoneal cavity of mice which have been previously injected with Brewers thioglycolate medium, results in the immortalization of peritoneal macrophage (PMφ) cells maintaining intact many of their morphological and functional properties. J2 virus immortalizes PMφ in vivo in a very efficient manner, and since no extra manipulation of the cells, exogenous growth factors, or feeder layers are required for the in vitro proliferation of the immortalized cells, numerous continuous cell lines can be readily established. This method of utilizing the J2 virus in vivo represents a novel technique for obtaining hematopoietic cell lines that are difficult to immortalize in vitro.