Normal human epidermis contains an interferon-like protein.

Interferons have been postulated to participate in growth regulation of normal body tissues and are known to inhibit growth of human epidermal keratinocytes in vitro. Polyclonal antibodies to recombinant human interferon-alpha, purified by passage over an affinity column (Sepharose coupled to the recombinant interferon), used in the indirect immunofluorescent method specifically stained the proliferative (basal) compartment of human epidermis in histological cross-sections of normal skin and in cultured keratinocyte colonies. Extracts prepared from healthy nonvirally infected keratinocyte cultures contained interferon activity as determined by viral plaque inhibition assay. Using the Western blotting technique column-purified antibodies and antisera to recombinant human interferon-alpha recognized a band of approximately 40 kD when reacted with both extracted keratinocyte proteins and recombinant human interferon-alpha standards, that gave in addition a band of approximately 20 kD. The above findings suggest that interferon or a closely related protein is present in the proliferative compartment of normal epidermis in the absence of viral infection and therefore may serve as a physiological modulator of epidermal growth.

Relationship between binding affinities to cellular retinoic acid-binding protein and in vivo and in vitro properties for 18 retinoids.

A new rapid assay has been developed for measurement of the binding of [3H]retinoic acid to cellular retinoic acid-binding protein. The assay, which uses activated charcoal for the separation of bound from unbound retinoic acid, was used to determine the concentration required to inhibit the binding of [3H]retinoic acid to cellular retinoic acid-binding protein by 50% for 18 retinoids with free carboxylic acid groups. Partially purified cellular retinoic acid-binding proteins isolated from rat testes and carcinogen-induced rat mammary tumors were used for these determinations. The following parameters were also determined for some or all of the retinoids: hypervitaminosis A doses; activity against carcinogen-induced mouse skin papillomas; inhibition of growth of a rat chondrosarcoma; inhibition of growth of 3T6 cells; and differentiation of the embryonal carcinoma cell line PCC4.azaIR. While all retinoids that are potent in these biological test systems bind tightly to cellular retinoic acid-binding protein, the converse is not true. The lack of a consistent quantitative correlation between 50% inhibitory concentration and biological activity is probably due to insufficient concentrations of the retinoid in the target tissue or celll, which is a consequence of factors such as absorbability, metabolism, tissue distribution, and pharmacokinetics.

Recombinant interferon alfa-2a in metastatic renal cell carcinoma: assessment of antitumor activity and anti-interferon antibody formation.

Twenty-one patients with advanced, measurable, renal cell carcinoma (RCC) were administered recombinant interferon alfa-2a (rIFN-alpha 2a) (Roferon-A; Roche Laboratories, Nutley, NJ) intramuscularly beginning at 3 x 10(6) units and escalating to 36 x 10(6) units, 5 d/wk for a total induction period of 14 weeks. rIFN-alpha 2a antibody production was measured using an enzyme immunoassay (EIA). Those sera found to be positive for presence of antibody by the EIA were tested for the presence of neutralizing antibodies (NA) by an antiviral neutralization bioassay (ANB). All patients were evaluable for toxicity, and 19 were evaluable for response and for incidence of antibody formation. Five patients (26%; 95% confidence interval, 6% to 46%) had complete responses (CR) or partial responses (PR) with a median duration of 283 days. An additional ten patients (53%) had minor tumor regressions with a median duration of 86 days. Fifty-one percent of evaluable patients are alive at 18.6 months. Antibodies to rIFN-alpha 2a as measured by the EIA, were detected in 12 (63%) patients. NA were measured in the serum of six (50%) of those EIA-positive patients. Overall, six of 19 patients (32%) developed NA. Median time to the development of antibody as measured by EIA or NA was 8 and 14 weeks, respectively. Median NA titer was 1,200 IFN neutralizing U/mL. NA-positive and -negative patients had a median duration of response of 13.7 v 9.9 months, and survival of greater than 21.3 v 18.3 months, respectively. Clinical toxicity was mild and not therapeutically limiting. Autoantibody production (ANA, rheumatoid factor [RF], Coombs' direct/indirect) occurred in both NA-positive and -negative patients. The clinical significance of the antibodies to rIFN-alpha 2a and the associated autoantibody formation remain unclear; however, presence of antibody was not associated with adverse clinical sequelae.

In vivo immortalization of murine peritoneal macrophages: a new rapid and efficient method for obtaining macrophage cell lines.

Although several murine macrophage (m phi) cell lines from different sites have previously been obtained by in vitro infection with the J2 murine retrovirus, which carries the v-raf and v-myc oncogenes, it was not possible to immortalize thioglycolate-elicited peritoneal macrophages (Pm phi s) by this in vitro procedure. A technique utilizing in vivo injection of the J2 virus has been developed to overcome this problem. The J2 virus immortalized Pm phi s in a very efficient manner in vivo because no exogenous growth factors were required for the in vitro proliferation of these cells and numerous continuous cloned cell lines were readily established. In contrast, Pm phi s obtained from uninfected mice or Pm phi s infected in vitro with the J2 virus did not proliferate. The in vivo immortalized cells had many of the morphological and functional characteristics of m phi s. Analysis of two of the clones, PMJ2-PC and PMJ2-R, demonstrated intracellular expression of the product of the v-raf gene, presence of m phi-associated cell surface antigens, interleukin-6 secretion induced by lipopolysaccharide, and biological response modifier-induced cytotoxic activity against tumor cells. In addition, one of the clones, PMJ2-PC, constitutively expressed major histocompatibility complex (MHC) class II antigens, and in the other clone, PMJ2-R, MHC class II antigens expression was induced by recombinant murine interferon-gamma. This method of utilizing the J2 virus in vivo represents a novel technique for obtaining hematopoietic cell lines from cells that are difficult to immortalize in vitro.

A second-generation enzyme immunoassay for detection of antibodies to IFN-alpha.

We have developed a solid-phase enzyme-linked immunoassay (EIA) for detecting antibodies to interferon-alpha2 (IFN-alpha2) in serum or plasma. In this assay, based on the sandwich principle, the capture antigen, IFN-alpha2, is covalently bound to the wells in 96-well plates. This novel procedure offers considerable advantages over the antigen binding by passive adsorption used in most previous EIA. Specific antibodies present in clinical specimens bind to the anchored antigen and are detected by adding peroxidase-labeled IFN-alpha2 and a peroxidase substrate mixture. The resultant color is a function of the concentration of antibody in the sample. The assay has proved to be convenient, precise, and reproducible and can detect as little as 1-5 ng/ml of specific antibody IgG.

Interferon immunogenicity: preclinical evaluation of interferon-alpha 2a.

A preclinical evaluation of the immunogenicity of various preparations of interferon-alpha (IFN-alpha) was performed with in vitro and in vivo animal models. The distribution of genes for IFN-alpha 2a, IFN-alpha 2b, and IFN-alpha 2c in various cell populations and the response of human T cell clones to IFN-alpha peptides were investigated. The immunogenicity of IFN-alpha in IFN-alpha 2b transgenic mice and factors that influence the immunogenicity of IFN-alpha in normal mice were also studied. The genes for IFN-alpha 2a and IFN-alpha 2b were found in KG-1 cells, whereas IFN-alpha 2b and IFN-alpha 2c genes were present in Namalwa cells. No difference in proliferation of human T cells, T cell lines, or T cell clones could be obtained with IFN-alpha peptides. In transgenic mice bearing the human IFN-alpha 2b gene, no antibody response was obtained following immunization with either IFN-alpha 2a or IFN-alpha 2b. Normal mice immunized with either IFN-alpha 2a or IFN-alpha 2b produced equivalent titers of antibodies, which cross-reacted with both IFNs. Studies evaluating the relative immunogenicity of IFN-alpha in normal mice demonstrated that a number of treatment and host variables can modulate immunogenicity of IFN-alpha preparations.

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.

Antitumor activity of interleukin 12 in preclinical models.

Interleukin 12 (IL-12) is a heterodimeric cytokine with a number of biological effects that are consistent with its potential role as an antitumor agent. The antimetastatic and antitumor activities of IL-12 have been demonstrated in a number of murine tumor models. Both the inhibition of established experimental pulmonary or hepatic metastases and a reduction in spontaneous metastases have been achieved by treatment with murine IL-12. Systemic treatment of mice bearing subcutaneous tumors with IL-12 results in tumor growth inhibition, prolongation of survival, and, in some models, tumor regression. The antitumor effect of IL-12 in these models is dose-dependent and can be initiated against well-established tumors. Mice cured of their tumor by IL-12 treatment are specifically immune to rechallenge with the same tumor. A series of experiments have demonstrated that both T-cells and interferon-gamma (IFN-gamma) induction are necessary for the optimal antitumor effects of IL-12. However, the antitumor efficacy of IL-12 has not been observed after exogenous administration of murine IFN-gamma, suggesting that additional factors may be important for the antitumor effects of IL-12. In several tumor models, IL-12 is more active or has a larger therapeutic window than either IL-2 or IFN-alpha, two cytokines with demonstrated antitumor activity against human malignancies. Combining IL-12 with other cytokines or chemotherapeutic drugs can improve antitumor effects.

Use of 125I-interferons in pharmacokinetic and tissue distribution studies.

The in vivo fate of radiolabeled recombinant human leukocyte A interferon (125I-rIFN-alpha A) and intramolecular hybrid A/D (125I-rIFN-alpha A/D Bgl) were studied, following iv injection into CD1 mice. Trichloroacetic acid (TCA) precipitable radioactivity, as well as antiviral activity, were measured in sera and several organ extracts. The results obtained by bioassay were very similar to those obtained by measuring the TCA precipitable radioactivity. The kidney and liver showed preferential uptake of these 125I-IFNs. These studies indicate the feasibility of using radioiodinated IFNs in tissue distribution and pharmacokinetic evaluations.

A sensitive radioimmunoassay for detection of antibodies to recombinant human interferon-alpha A.

A radioimmunoassay (RIA) for the detection of antibodies to recombinant human leukocyte interferon A (rHuIFN-alpha A) in human serum has been developed and validated against the standard antiviral neutralization bioassay (ANB). The assay measures the binding of 125I-labeled rHuIFN-alpha A to immunoglobulins in serum. Aliquots of patients' sera are incubated with 125I-rHuIFN-alpha A and the complexes formed between antibodies in the sera and the 125I-rHuIFN-alpha A are precipitated with goat anti-human IgG serum. The radioactivity in the immune precipitate is a measure of the quantity of antibody (if present) in the serum. The sensitivity of this RIA is 5 ng of IgG/ml of serum.

Nitric oxide synthase induction in lines of macrophages from different anatomical sites.

Induction of nitric oxide synthase (iNOS) and nitric oxide (NO) production have been demonstrated using three macrophage cell lines from different anatomical sites, which had been immortalized using a rapid and convenient procedure previously described. Lysis of tumor cells presumably was caused by NO accumulation in the supernatants of cultures of the three cell lines after induction with a mixture of recombinant murine interferon gamma (rMuIFNgamma) and lipopolysaccharide (LPS). Induction by these two biological response modifiers (BRM) caused lysis of tumor cells and was repressed by addition of 1 microM (final concentration) of methyl-L-arginine (MMA) to the mixture during induction of the enzyme. Research using readily generated macrophage cell lines may facilitate clarify basic aspects of iNOS induction in these cells.

Tumoricidal alveolar macrophage and tumor infiltrating macrophage cell lines.

Continuous alveolar macrophage (AM) and tumor-infiltrated (TIM) cell lines have been generated from C57B16J mice by in vitro infection with the J2 retrovirus carrying the v-raf and v-myc oncogens. Four cloned AM cell lines (AMJ2-C8, AMJ2-C10, AMJ2-C11, AMJ2-C20) and 3 cloned TIM cell lines (TIMJ2-C4, TIMJ2-C7 and TIMJ2-C15) were expanded for further characterization. Flow cytometry detected the product of the raf gene in the cytoplasm of all these cell lines. Studies on the tumoricidal properties of these AM and TIM cell lines demonstrated differences in their response to a panel of known macrophage activators. Four of these cell lines (AMJ2-C8, AMJ2-C10, TIMJ2-C7 and TIMJ2-C15) were activated following exposure to recombinant murine interferon gamma (rMuIFN-gamma) but not lipopolysaccharide (LPS) or muramyl dipeptide (MDP). AMJ2-C20 was only activated by incubation with rMuIFN-gamma plus LPS. AMJ2-C11 and TIMJ2-C4 are the cell lines that most closely resembled the response pattern of the parental AM and TIM, since they could be activated by either the combination of rMuIFN-gamma plus LPS or rMuIFN-gamma plus MDP. Constitutive expression of MHC-class-II antigens was low on AMJ2-C11 or TIMJ2-C4 but was increased following exposure to rMuIFN-gamma. Neither cell line secreted substantial amounts of IL-1 or TNF but both secreted large amounts of IL-6. Thus these cell lines could be powerful tools to study AM and TIM activation and cytotoxicity.

Tumoricidal activity and cytokine secretion by tumor-infiltrating macrophages.

Murine macrophages from different anatomical sites were compared for their ability to become tumoricidal and to secrete interleukin-1 (IL-1) and tumor necrosis factor (TNF) following stimulation in vitro by several biological response modifiers (BRM). Peritoneal macrophages (PM), alveolar macrophages (AM), and tumor-infiltrating-macrophages (TIM), isolated from B16F10 melanoma colonies in the lung, were incubated overnight with BRM [recombinant murine interferon gamma (rMulFN-gamma), lipopolysaccharide (LPS), muramyl dipeptide (MDP)], either alone or in combination. PM exhibited an increased cytotoxic response following incubation with LPS or rMuIFN-gamma but not with MDP. Both AM and TIM were induced to become tumoricidal following incubation with rMuIFN-gamma plus LPS or rMuIFN-gamma plus MDP but not after stimulation with any BRM alone; the level of cytotoxicity obtained with TIM incubated with rMuIFN-gamma plus LPS was slightly lower than that observed with PM or AM, while with rMuIFN-gamma plus MDP both AM and TIM had lower cytotoxicity than PM. Secretion of IL-I and TNF was observed in PM stimulated with LPS or MDP but not with rMuIFN-gamma. Likewise, secretion of IL-I by AM or TIM was also induced with LPS, although less than that obtained with PM. AM stimulated with LPS secreted larger amounts of TNF than PM while TIM secreted very low amounts of TNF. However, this result may be a consequence of the enzymatic isolation procedure used to obtain TIM since TNF secretion was also impaired in LPS-stimulated normal lung macrophages isolated by a similar enzymatic procedure, or enzyme-treated PM. Our results suggest that TIM obtained from lung metastases share certain functional characteristics with normal AM and respond to BRM in like manner with respect to induction of tumoricidal activity and cytokine secretion.

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 Kaposi's 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.

The detection of antibodies to recombinant interferon alfa-2a in human serum.

Three different procedures have been used for detecting antibodies to Roferon-A (recombinant human interferon alfa-2a, rHuIFN alpha-2a) in the serum of patients who received this interferon as part of ongoing clinical trials: an antiviral neutralization bioassay (ANB), the standard method recommended by the World Health Organization (WHO), and the more recently developed radioimmunoassay (RIA) and enzymeimmunoassay (EIA). Although the three tests are based on different principles, the correlation among them was excellent. The assays show differences in sensitivities with the ANB being the least sensitive of the three. The EIA equals the RIA in sensitivity, reproducibility, accuracy and labor and provides the advantage of safety and convenience in the use of non-radioactive materials. Therefore, the EIA has been selected as the most suitable assay for initial screening of the sera of patients receiving Roferon-A for the presence of antibodies to this interferon. EIA positive sera are then tested in the ANB to determine whether or not neutralizing activities are present.

Incidence and clinical significance of neutralizing antibodies in patients receiving recombinant interferon-alpha 2a.

In clinical trials with a range of doses of recombinant interferon-alpha 2a, we observed a 25% overall incidence of neutralizing antibody development. Careful data analysis did not reveal a relationship between antibody development and therapeutic response. Of 752 patients evaluable for antibody development and clinical response, 31% of the antibody-positive patients and 28% of the antibody-negative patients had therapeutic responses. Although the formation of anti-IFN antibodies seems to be associated with most IFN preparations, incidence and clinical significance have been difficult to determine for a number of reasons. Different assays with differing sensitivities for the detection of IFN antibodies have been utilized in different studies. Additionally, important clinical variables that affect antibody development have often not been carefully controlled or analyzed. The relationship between antibody development and multiple related factors, such as route of administration, dose regimen, cumulative dose, duration of treatment, and the underlying disease, requires clarification. Initial analyses suggest that the median time to antibody development may vary with the dose regime and cumulative dose, as well as the route of administration. Carefully designed prospective studies controlling for influential clinical variables and utilizing standardized assay techniques are required for a meaningful analysis of the antigenic potential of all therapeutic protein products.