Synergistic antiviral and antiproliferative activities of Escherichia coli-derived human alpha, beta, and gamma interferons

Combination effects of human recombinant interferon (alpha-2-arg, gamma) and cytotoxic agents on colony formation of human melanoma and hypernephroma cell lines

Malignant melanoma and hypernephroma show marginal response to chemotherapeutics and interferons when used as single agents. Using a modified soft agar clonogenic assay we investigated the antiproliferative effects of combinations of vinblastine, bleomycin, adriamycin, interferon alpha and gamma. On the hypernephroma cell line combinations of bleomycin and adriamycin with interferon gamma as well as combinations of both interferon types resulted in a synergistic antiproliferative effect. On the melanoma cell line combinations of bleomycin and adriamycin with interferon alpha and combinations of vinblastine with interferon gamma acted in a synergistic manner. All other combinations tested were only additive. Thus far, we could not find any antagonistic effect of interferons and chemotherapeutics.

Creation of phosphorylation sites in proteins: construction of a phosphorylatable human interferon alpha

A phosphorylation site was introduced into human interferon alpha A (IFN-alpha A) by site-specific mutation of the coding sequence. Three slightly different phosphorylation sites were created by using the predicted amino acid consensus sequences for phosphorylation by the cAMP-dependent protein kinase. The resultant modified interferons (IFN-alpha A-P) were expressed in Escherichia coli and purified. The purified proteins exhibit antiviral activity on bovine and human cells similar to that of the unmodified IFN-alpha A. The IFN-alpha A-P proteins can be phosphorylated by the catalytic subunit of cAMP-dependent protein kinase with [gamma-32P]ATP to high specific activity (2000-5000 Ci/mmol; 1 Ci = 37 GBq) with retention of biological activity. The 32P-labeled IFN-alpha A-P proteins bind to cells and can be covalently bound to the IFN-alpha/beta receptor with a bifunctional reagent as can human IFN-alpha A. The introduction of phosphorylation sites into proteins provides a procedure to prepare a large variety of radioactive proteins for research and clinical use.

A phase I-II trial of the combination of recombinant leukocyte A interferon and recombinant human interferon-gamma in patients with metastatic malignant melanoma

Twenty patients with advanced malignant melanoma received daily intramuscular recombinant leukocyte A interferon (rIFN-alpha A, Roferon-A, Hoffmann-Laroche, Nutley, NJ) concomitant with recombinant human interferon-gamma (rIFN-gamma Genentech, South San Francisco, CA). During the first week alpha dose was 2 X 10(6) U/m2 and the gamma dose was 0.01 mg/m2 with escalations, if clinically tolerable, during the second week to 5 X 10(6) U/m2 and 0.025 mg/m2, respectively. Twelve patients received the escalated doses; subsequent granulocytopenia and a flu-type illness were severe in four of the 12. We observed one partial response of MRI-documented and biopsy-confirmed osseous metastases for 7+ months. For all study participants, the median time to progression was 1 month with a median survival of 6 months. From the dose and schedule which we utilized, concurrent rIFN-alpha A and rIFN-gamma provided little impact on advanced malignant melanoma.

Mechanism of interferon action. Expression of reovirus S3 gene in transfected COS cells and subsequent inhibition at the level of protein synthesis by type I but not by type II interferon

The effect of interferon on the expression of the reovirus serotype 1 Lang strain S3 gene was examined in simian COS cells transfected with the expression vector pSVS3 containing the S3 gene under the control of the SV40 late promoter. When COS cells were treated with type I interferon-alpha 24 hr after transfection, the synthesis of the reovirus S3-encoded sigma NS polypeptide was inhibited about 10-fold as compared to that in untreated control cells. By contrast, under the same conditions, neither the plasmid DNA copy number nor the S3 gene mRNA levels were significantly affected by interferon treatment. Type II interferon-gamma, unlike the type I interferons-alpha, did not affect the rate of synthesis of polypeptide sigma NS in pSVS3-transfected cells.

Phase II trial of a combination of interferon-beta ser and interferon-gamma in patients with advanced malignant melanoma

Based upon the in vitro synergistic activity of interferon-beta (IFN-beta) and interferon-gamma (IFN-gamma) observed in melanoma cells, we initiated a Phase II trial using the combination to determine the clinical antitumor efficacy in patients with advanced disease. Fifteen patients with metastatic malignant melanoma were given 2,000 micrograms of recombinant IFN-gamma (rIFN-gamma) (Biogen) intravenously (i.v.) over 10 min, followed by a 10 min i.v. injection of 30 million units of recombinant IFN-beta (rIFN-beta ser) (Triton) 3 x/week. Six patients had skin, soft tissue, nodal, or subcutaneous metastases, 6 had visceral disease only, and 3 had both. Seven patients had received prior treatment, including chemotherapy (6), radiotherapy (3), and/or immunotherapy (3). Side effects included typical IFN constitutional symptoms such as anorexia, fatigue, nausea, and myalgias, but were not dose limiting. The mean drop in the white blood cell count (WBC) following 1 month of therapy, compared to baseline, was 3.3 x 10(3)/mm2 (p = 0.002); the mean increase in SGOT was 24.1 U/l (p less than 0.001). One patient had a dose reduction for Grade III anorexia and fatigue which did not resolve with repeated treatment. One patient with liver metastases had radiographical and clinical stabilization of his disease for 1 year. No responses were seen. The median time to progression was 6 weeks. Two patients' tumors were evaluable in the human tumor colony forming assay (HTCFA) and were markedly sensitive to the antiproliferative effects of IFN combinations. Both patients, however, failed to respond clinically.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of recombinant murine interferon-gamma and human interferon-alpha A/D(Bgl) administered in concert and their influence on natural killer cell function in mice

The pharmacokinetics of recombinant murine interferon-gamma (rMuIFN-gamma) administered alone and in combination with recombinant hybrid human interferon-alpha (rHuIFN-alpha A/D-[Bgl]) were studied following intravenous (i.v.) and intramuscular (i.m.) injections into mice. The concomitant influence of these IFNs on splenic natural killer (NK) cell function was also examined. The coinjection of both IFNs did not affect the pharmacokinetics of either after i.v. administration. However, simultaneous injection of both IFNs i.m. does result in statistically significant changes in the serum concentrations of rHuIFN-alpha A/D(Bgl). The clinical benefits of the increased bioavailability of rHuIFN-alpha A/D(Bgl) are not apparent since NK cell enhancement after both IFNs were injected together was the same as that obtained after injection of rHuIFN-alpha A/D(Bgl) alone. NK cell enhancement after both IFNs were injected together was the same as that obtained after injection of rHuIFN-alpha A/D(Bgl) alone. Correspondingly, the coinjection of both IFNs did not affect the pharmacokinetics of either.

Recombinant interferon gamma in hairy cell leukemia, multiple myeloma, and Waldenstrom's macroglobulinemia

Fifteen patients with multiple myeloma, five with hairy cell leukemia, and five with Waldenstrom's macroglobulinemia were treated with recombinant interferon gamma (rINF-gamma) to determine the antitumor activity of this agent. The rIFN-gamma was administered by daily intramuscular injection at doses ranging from 0.125 to 0.5 mg/m2. No responses were observed in patients with multiple myeloma, although in one patient the disease has remained stable for over 16 months. Minimal improvement in some hematologic indexes were observed in three of five patients with hairy cell leukemia. One partial remission and one minor response were documented in two of the five patients with Waldenstrom's macroglobulinemia. In five patients, an increase in normal serum immunoglobulins was observed. These results suggest that there is only minimal activity of rIFN-gamma as a single agent in neoplasms of B-cell origin.

Effects of scheduling and ascites-associated macrophages on combined antiproliferative activity of alpha-2b interferon and gamma-interferon in a clonogenic assay

Effects of combination treatment with human recombinant alpha-2b interferon (IFN-alpha 2b) and gamma interferon (IFN-gamma) and sequencing of the combination on colony formation of human tumor cells were studied in a human tumor clonogenic assay (HTCA) with or without ascites-associated macrophages (AAM). Five different human tumor cell lines were studied. Three of the five cell lines (ovarian cancer cell line BG-1, cervical cancer cell line ME-180, and melanoma cell line SK-MEL 28) were sensitive to both IFNs. Cervical cancer cell line CaSki was sensitive to IFN-alpha 2b but resistant to IFN-gamma. Endometrial cancer cell line HEC-1A was resistant to both IFNs. Synergistic interaction was observed in BG-1 and SK-MEL 28 with a combination of the IFNs. ME-180 did not exhibit a positive interaction, in spite of its sensitivity to each IFN. CaSki and HEC-1A also did not exhibit a positive combined interaction at clinically achievable concentrations. One sequential combination method (method 1: IFN-alpha 2b----IFN gamma with a 24-h interval) resulted in a similar antitumor effect as the simultaneous combination. A reversed sequential method (method 2: IFN-gamma----IFN-alpha 2b with a 24-h interval) was less effective in three of the five cell lines. In BG-1, AAM enclosed in the lower layer markedly enhanced the antitumor effect of combined IFNs as well as each IFN alone. The antitumor effect with method 1 was significantly greater than that achieved with simultaneous combination or combination according to method 2 in the presence of AAM (P less than 0.01). These results suggest that (1) a synergistic antitumor effect of IFN-alpha 2b and IFN gamma is demonstrable in selected types of tumors, depending upon the sensitivity of each tumor cell line to both IFNs; (2) optimal scheduling for the direct antitumor effect of combined IFNs seems to be long-term exposure of cells to the IFN, the cells being treated with both IFNs either simultaneously or sequentially (IFN-alpha 2b preceding IFN-gamma); and (3) AAM potentiate the antitumor effect of IFNs either alone or in combination. Finally, IFN-alpha 2b may have some priming effects for the indirect effect of IFN gamma mediated through AAM in certain tumor cells.

Interferon gamma induces the myristoylation of a 48-kDa protein in macrophages

The lymphokine interferon gamma (IFN-gamma) induces the selective myristoylation of a macrophage protein with an apparent molecular mass of 48 kDa. The myristic acid-protein bond is resistant to treatment with hydroxylamine, suggesting that the fatty acid moiety is in an amide linkage. As little as 1 unit of IFN-gamma per ml induces the myristoylation of the 48-kDa protein, with half-maximal myristoylation being observed with 4 units/ml. The effect is observed within 1 hr after exposure to IFN-gamma and is maximal by 3-4 hr, after which it declines. IFN-alpha does not induce the myristoylation of the 48-kDa protein, and IFN-beta does so very poorly. Neither IFN-alpha nor IFN-beta has any effect on IFN-gamma-induced myristoylation of the 48-kDa protein. The 48-kDa protein is constitutively myristoylated in murine macrophages that have been activated in vivo by intraperitoneal injection of Corynebacterium parvum, suggesting that it may be an early intermediate in the activation of macrophages.

The interaction of interferon-alpha and -gamma: regulation of (2-5)A synthetase activity

The interaction of IFN-alpha and IFN-gamma on the induction of antiviral, growth inhibitory, and (2-5)A synthetase activities was investigated in T98G and A549 cells. Synergistic or inhibitory effects which were host-cell dependent were seen with both simultaneous and sequential IFN treatments. Interestingly, IFN-gamma 1 pretreatment affected the levels of IFN-alpha-induced (2-5)A synthetase activity differently in the two cell types. In T98G cells, sequential treatment resulted in an overall decrease in induction of enzyme activity that was not observed in A549 cells. Receptor binding assays and measurements of steady-state mRNA levels indicated that this effect of IFN-gamma pretreatment does not occur at the level of either receptor expression or induction of transcription of the low-molecular-weight form of (2-5)A synthetase.

Natural human interferon-gamma derived from lipopolysaccharide-stimulated human myelomonocytic HBL-38 cells

A human myelomonocytic cell line, HBL-38 cells, propagated in vivo, spontaneously produced interferon (IFN)-gamma and IFN-alpha. Whereas hemmagglutinating virus of Japan (HVJ) enhanced the production of IFN-alpha, bacterial lipopolysaccharide (LPS) markedly enhanced the production of IFN-gamma. LPS could be replaced with lipid A. Furthermore, the enhancement of production of IFN-gamma by LPS was completely abolished by polymixin B. IFN-gamma derived from LPS-stimulated HBL-38 cells was purified to homogeneity and characterized. The apparent molecular weight, subspecies composition, amino acid sequence and glycosylated sites were in agreement with those of the product of normal human peripheral blood lymphocytes (PBL). These results indicate that the myelomonocytic HBL-38 cells, not a T-cell line, can also produce IFN-gamma identical to the product of normal human PBL.

Modulation of responsiveness of chronic myelogenous leukemia granulocyte-macrophage colony-forming cells to growth regulation following in vivo treatment with recombinant gamma-interferon

A patient with Philadelphia chromosome (Ph) chronic myelogenous leukemia (CML), in chronic phase, was treated with recombinant gamma-interferon (r gamma-IFN) in a phase I clinical trial. Prior to treatment, analysis of in vitro agar culture parameters indicated hyporesponsiveness of granulocyte-macrophage colony-forming cells (CFU-GM) to inhibition by prostaglandin E and acidic isoferritins and diminished expression of class II major histocompatibility complex (MHC) antigens (HLA-DR). Treatment was associated with no change in bone marrow cellularity or in the percentage of Ph cells. However, in vitro cultures of bone marrow cells showed a return to normal levels of both expression of CFU-GM class II antigen and of sensitivity to inhibition by prostaglandin E and acidic isoferritins which predicted and/or confirmed clinical response. Throughout the course of interferon therapy, white blood cell counts (WBC) and the percentage of bone marrow blast cells were maintained at normal levels. Onset of aggressive-phase disease was associated with increased WBC, an increase in bone marrow blast cells, a secondary chromosomal abnormality, loss of CFU-GM sensitivity to inhibition by putative negative growth regulators, and markedly diminished MHC class II antigen expression. Following a bone marrow transplant from a matched sibling, all hematologic parameters studied were found to be normal. These findings indicate that treatment with r gamma-IFN can modulate some of the abnormal growth characteristics of CFU-GM observed in CML.

Differential efficacies of recombinant murine interferon-gamma and recombinant human interleukin 2 against EL4-bearing mice

The effects of treating tumor-bearing mice with recombinant murine interferon-gamma (rMuIFN-gamma) and recombinant human interleukin-2 (rIL2) were compared using EL4 thymoma with the same mouse model. Successive administration of rMuIFN-gamma (10(4) units) starting 1 day after tumor inoculation was highly effective, while rIL2 (5 x 10(4) Jurkat units) starting 7 days later produced potent suppression of tumor growth leading to complete cure in about 50% of the mice treated with either of two agents. These results showed that the effectiveness of these lymphokines differed depending on the time of their administration. Furthermore, the therapeutic effect of rIL2 against tumor-bearing mouse was poorer in T-cell-deficient nude mice than in B6 mice and NK-cell-deficient beige mice, whereas the effect of rMuIFN-gamma was poorer in beige mice than in B6 and nude mice. These results suggest that the role of NK cells in the tumor regression caused by the treatment of rMuIFN-gamma is much more important than that of other activated lymphocytes, and that the antitumor activity of rIL2 may be due to the generation of T-cell-related lymphocytes. Our results reveal that combination therapy with rMuIFN-gamma and rIL2 can induce a synergistic effect on EL4-bearing mice.

Recombinant interferon-gamma inhibits the mitogenic effect of platelet-derived growth factor at a level distal to the growth factor receptor

Highly purified preparations of recombinant human interferons (rIFNs)-alpha A, -beta, and -gamma all inhibited platelet-derived growth factor (PDGF)-induced DNA synthesis in normal human dermal fibroblasts, as monitored by incorporation of [3H]-thymidine into trichloroacetic acid (TCA)-insoluble material. rIFN-gamma was the most potent, since it blocked the PDGF response by 50% at about 10 U/ml or 0.3 ng/ml, whereas with rIFN-alpha A and rIFN-beta 4000 U/ml and 600 U/ml, respectively (10 ng/ml in both cases), were required to achieve the same effect. There was a close parallelism between the ability of these rIFNs to inhibit PDGF mitogenic activity and their capacity to inhibit cell proliferation in serum-containing medium. None of the rIFNs inhibited specific binding of 125I-PDGF to fibroblasts, and none interfered with receptor internalization. The mechanism of action of rIFN-gamma was analyzed further. rIFN-gamma did not inhibit uptake of [3H]-thymidine into these cells. However, it shifted if the time point of initiation of DNA synthesis from about 14 h after stimulation with PDGF to about 18 to 21 h and decreased significantly the rate of the DNA synthesis. rIFN-gamma could be added up to 6 h following stimulation with PDGF with no loss of its inhibitory effect. rIFN-gamma also blocked the mitogenic activity of epidermal growth factor and basic fibroblast growth factor. Taken together these results implicate that rIFN-gamma exerts its antimitogenic effect by inhibiting a process that occurs late in the PDGF signaling pathway and onto which the activity pathways of other mitogens converge. In view of the important role PDGF may play in wound-healing and in the pathogenesis of the proliferative lesions of arteriosclerosis, these data point to a possible role IFN-gamma may play as a regulator of these processes in vivo.

Agonist and antagonist effects of interferon alpha and beta on activation of human macrophages. Two classes of interferon gamma receptors and blockade of the high-affinity sites by interferon alpha or beta

H2O2-releasing capacity and limited antitoxoplasma activity could be induced in human macrophages (derived from monocytes cultured greater than or equal to 5 d) but not in monocytes themselves (cells cultured less than or equal to 4 d) by a further 3-d incubation with pure natural or rIFN-alpha or -beta. More than 3 pM (10 U/ml) of these IFNs was required, with greatest effects at approximately 300 pM (10(3) U/ml). At 300 pM, H2O2-releasing capacity was enhanced 4.4 +/- 1.6-fold over medium control (mean +/- SD for natural INF-alpha, rIFN-alpha A, rIFN-alpha D, and rIFN-beta) compared to an 8.4 +/- 4.8-fold increase with rIFN-gamma (100 pM, 100 U/ml) in the same experiments. Unexpectedly, low concentrations of IFN-alpha or -beta (3 fM-300 pM) blocked induction of H2O2-releasing capacity by rIFN-gamma (10 pM), with a 50% inhibitory dose of approximately 80 fM. However, IFN-alpha or -beta (3 fM-300 pM) could not inhibit the effect of higher concentrations of rIFN-gamma (1 nM). In contrast to results with monocytes or young macrophages, Scatchard plots of binding of 125I-rIFN-gamma to mature macrophages (day 8 of culture) indicated two classes of binding sites: approximately 2,000 high-affinity sites (Kd approximately 0.43 nM) and approximately 23,000 low-affinity sites (Kd approximately 6.4 nM) per cell. Binding of 125I-rIFN-gamma to the high- but not the low-affinity sites was blocked by simultaneously added IFN-alpha or -beta, with a 50% inhibitory dose of approximately 2 U/0.25 ml (approximately 2 pM), or reversed by subsequently added IFN-alpha or -beta. Thus, differentiation of human mononuclear phagocytes in vitro is accompanied by the emergence of (a) an agonist response to submicromolar concentrations of IFN-alpha or -beta, (b) antagonism of the effect of picomolar IFN-gamma by femtomolar IFN-alpha or -beta, (c) two classes of IFN-gamma-Rs, and (d) nonstimulatory binding of IFN-alpha or -beta to the high- but not the low-affinity IFN-gamma-Rs, with higher affinity than rIFN-gamma itself. We speculate that traces of IFN-alpha or -beta derived from stromal cells, parenchymal cells, or resident macrophages may dampen the activation of mature tissue macrophages by the small amounts of IFN-gamma that diffuse from inflammatory sites into normal tissues. Such a mechanism could constrain the potentially destructive phenomenon of macrophage activation to areas where monocytes have recently immigrated and/or the concentration of IFNs is high.

Properties of natural porcine interferons

Natural porcine interferons (PoIFNs) were obtained from: adherent peripheral blood leukocytes induced with Newcastle disease virus (NDV) (IFN-alpha), kidney fibroblasts induced with poly(I:C) (IFN-beta) and whole blood leukocytes induced with phytohemagglutinin (IFN-gamma). PoIFN-alpha was active in porcine, bovine, human, and murine cells. It was sensitive to anti-human IFN-alpha antiserum. Analyzed by SDS-polyacrylamide gel electrophoresis and by gel filtration, the molecular weight of the main fraction of PoIFN-alpha was between 25,200 and 28,700. PoIFN-beta and a small fraction of PoIFN-alpha were bound to concanavalin A which suggests that they are glycoproteins. PoIFN-beta and PoIFN-gamma were active only in porcine and bovine, and porcine cells, respectively. Physicochemical properties of porcine IFNs resembled those of human IFNs. PoIFN-alpha or PoIFN-beta and PoIFN-gamma acted synergistically in the antiviral assays. Thus, the porcine IFN system appears to be similar to the system in the human and in murine species, being serologically related to the former.

Decreased locomotor activity produced by repeated, but not single, administration of murine-recombinant interferon-gamma in mice

A single treatment with murine-recombinant interferon-gamma (murIFN-gamma; 30 micrograms/mouse), whether evaluated immediately after, or four hrs after, intraperitoneal injection, does not alter open field activity levels. On the other hand, repeated murIFN-gamma administration (30 micrograms/mouse/day for 5 days) results in decreased spontaneous locomotor activity and an increase in body weight.

Interferon therapy for metastatic renal cell carcinoma

We have used multiple interferon protocols to treat 274 patients who had metastatic renal cell carcinoma. Leukocyte (alpha) interferon in 50 patients produced 3 complete responses (CR) and 10 partial responses (PR), a 26% response rate that was nearly matched among the next 89 patients treated with recombinant alpha interferon (2 CR, 17 PR, 21%). Other types and combinations of interferon, even when coupled with cytotoxic chemotherapy or other biologic agents, did not produce better results. Interferon has definite activity against renal cell carcinoma, but clinical experience has not yet defined the optimal type, dose, and treatment schedule.

Comparative study of the antitumor effect of two types of murine recombinant interferons, (beta) and (gamma), against B16-F10 melanoma

A comparative study of the antitumor effect of murine recombinant interferon(beta) less than Mu-rIFN(beta) greater than and murine recombinant interferon(gamma) less than Mu-rIFN(gamma) greater on B16-F10 melanoma was conducted. Administration of Mu-rIFN(gamma) i.p. into C57BL/6 mice on days 1 to 7 produced a higher suppressive effect than Mu-rIFN(beta) both on the growth of s.c. implanted tumor and on the formation of artificial pulmonary metastasis. Pharmacokinetic study of Mu-rIFN(gamma) demonstrated that high plasma levels were retained for a long time. In clonogenic assay, Mu-rIFN(gamma) at 1000 units/ml showed about 80% inhibition of colonies of B16-F10 melanoma. However, Mu-rIFN(beta) hardly inhibited the colonies, even at 1000 units/ml. Augmentation of natural killer (NK) cytotoxicity was much greater with Mu-rIFN(beta) than Mu-rIFN(gamma), whereas Mu-rIFN(gamma) enhanced the cytotoxicity of peritoneal macrophages more strongly than Mu-rIFN(beta). Injection of Mu-rIFN(gamma) i.p. 1 day before tumor challenge also inhibited the formation of pulmonary metastasis of B16-F10 melanoma. However, pretreatment of mice with carrageenan significantly suppressed the inhibitory effect of Mu-rIFN(gamma). From these results, it is suggested that the inhibitory effect of Mu-rIFN(gamma) on the tumor growth and metastases of B16-F10 melanoma is mediated partly by direct antitumor effect and partly by the activation of macrophages, and that the augmentation of NK activity contributes mainly to the antitumor effect of Mu-rIFN(beta).

Alpha and gamma interferon in the treatment of advanced renal cell carcinoma

Thirty-two patients with proven progressive metastatic renal cell carcinoma were treated with the combination of 0.1 mg/m2 (2 X 10(6) IU/m2) r-interferon (r-IFN)-gamma and 6 micrograms/m2 (2 X 10(6) IU/m2) r-IFN-alpha. In case of progressive disease (PD) or stable disease (SD), after 8 weeks, the dose of r-IFN-alpha was escalated by 6 micrograms/m2 every 2 weeks until the maximum tolerable dose was reached, while r-IFN-gamma was maintained at the low dose. The rationale for this study is provided by the dose-related efficacy of IFN-alpha as a monotherapy, the potent immunostimulatory activity of IFN-gamma, and the alleged synergistic effect of the combination. Fourteen patients are evaluable for 8 weeks of low-dose combination treatment (7 X SD, 5 X PD, 2 X early progression), while so far 6 of 24 patients (25%) who started dose escalation of IFN-alpha have reached a partial response. These data indicate better efficacy with higher doses of IFN-alpha. Because of the infrequent administration and the relative low doses, compared to other trials, the treatment regimen was well tolerated. Although preliminary results are promising, definite efficacy remains to be proven.

Sensitivities of human glioma cell lines to interferons and double-stranded RNAs individually and in synergistic combinations

The antiproliferative effects of human interferons (IFNs) and double-stranded RNAs (dsRNAs) were studied in five human glioma cell lines. Dose response curves were generated over a 72 hour treatment period. The concentration of interferon or double-stranded RNA necessary to produce a 50% antiproliferative response (GI50) was calculated by linear regression analysis. Two cell lines were more sensitive to IFN-beta than to IFN-alpha, one cell line was more sensitive to IFN-alpha than to IFN-beta and two cell lines had approximately equal sensitivities to both interferons. All cell lines showed some sensitivity to either IFN-alpha or IFN-beta. IFN-gamma had no antiproliferative effect on any of the cell lines. In addition, only one of the cell lines displayed sensitivity to dsRNA, in which the response to poly(I).poly(C) was greater than that to a mismatched analogue of poly(I).poly(C), r(I)n.r(C12,U)n (Ampligen). There was no correlation between the sensitivities to type I IFNs (alpha and beta), type II IFN (gamma) or the dsRNAs. The antiproliferative effect of combinations of IFNs, or IFNs and Ampligen, was studied in one of the cell lines. A significant synergistic antitumor effect was seen with all of the IFN/Ampligen combinations (p less than 0.02), including IFN-gamma/Ampligen, even though these cells were resistant to IFN-gamma alone. Synergy was also seen in the IFN-alpha/IFN-gamma (p less than 0.02) and IFN-beta/IFN-gamma (p less than 0.05) combinations. The IFN-alpha/IFN-beta combination gave an additive antitumor effect. These results indicate that IFN-alpha and IFN-beta alone or combinations of type I IFNs, type II IFNs and Ampligen can be effective in inhibiting the growth of glioma cells.

Recombinant interferons alpha and gamma: comparative antiviral activity and synergistic interaction in encephalomyocarditis virus infection of mice

The antiviral properties of 2 recombinant DNA-produced interferons, a human hybrid interferon alpha that is active in mice and a murine interferon gamma, were examined in the treatment of mice infected with encephalomyocarditis virus. A single dose of interferon alpha induced a protective state in mice more rapidly than did interferon gamma, but the activity of the latter was more long lasting. When interferon and virus were administered 6 h apart, either intraperitoneally or intravenously, interferons alpha and gamma were equally effective. However, this was not the case when the routes of treatment and infection were different. Interferon alpha showed somewhat reduced activity when the route of administration (intravenous) was different from the route of virus challenge (intraperitoneal) while interferon gamma showed very little activity when tested in this manner. When interferons alpha and gamma were administered in combination to mice, a marked synergistic antiviral effect was observed.

Regulation of cell growth by interferon

Interferons can regulate growth and differentiation in a wide range of cell types. These mechanisms are currently being examined. Interferons inhibit the growth of tumour cells and are thus potential anti-cancer agents. They can also inhibit normal cell growth in vitro, and stimulate tumour cell growth in vitro. They may also be involved in some autoimmune diseases. This review examines the effect of interferons on cell proliferation, function, and growth, focusing primarily on in vitro cell systems.

Interleukin-2 activated human killer lymphocytes: lack of involvement of interferon in the development of IL-2-activated killer lymphocytes

When cultured with native or recombinant interleukin-2 (IL-2) human small agranular lymphocytes acquire the ability to kill various tumor targets. The development of these IL-2 activated killer (IAK) cells, also known as LAK, is observed in the absence of antigen or mitogen. Interferons are known to augment the lytic effects of natural killer cells and cytolytic T lymphocytes. Our study was undertaken to examine the effect of human alpha, beta, and gamma interferons on the induction and the effector phase of IAK function. When cultured with small lymphoid cells IFN alone did not induce anti-tumor cytolytic activity in those lymphocytes. Despite their known anti-proliferative effects, none of the 3 IFN species at any concentrations tested inhibited the development of IAK activity when present during the entire culture period. IFN neither inhibited nor augmented the development of IAK cells under suboptimal conditions. Furthermore, activation of IAK cells was not affected by the presence of neutralizing antibodies to either alpha or gamma IFN. Post-activation exposure of IAK cells to IFN also failed to either augment or inhibit their lytic activity. Thus, neither endogenously generated nor exogenously added IFN had any effect on the IAK system, in contrast to their augmenting effects on NK cells and CTL.

Potentiation of antiproliferative activity by mixtures of human recombinant IFN-alpha 2 and -gamma on growth of human cancer nodules maintained in continuous organotypic culture

Alveolar II pulmonary tumor cells (A549 cells) maintained in continuous tridimensional organotypic culture were used to evaluate the eventual potentiation effect of mixtures of recombinant human interferon-alpha 2 and -gamma on growth inhibition of the tumor nodules. A continuous 45 day treatment (interferon renewed three times a week) with 10, 10(2) or 10(3) U/ml of IFN-alpha 2 or -gamma combined with a fixed high dose (10(3) U/ml) of either IFN-alpha 2 or -gamma resulted in an additive or synergistic growth inhibition according to the doses used. There was a close dose-effect relation, the percentage of inhibition increasing proportionally to the variable IFN doses added to the fixed high dose; moreover, the growth inhibition effect occurred earlier with the mixtures than with IFNs used separately. Furthermore, the growth inhibition observed with 2000 U/ml of the mixture (1000 U/ml of each IFN) was greater than that induced by 2000 U/ml of IFN-alpha 2 or -gamma used alone. A 35-day treatment with IFN-alpha 2 1000 U/ml plus IFN-gamma 1000 U/ml led to a complete growth inhibition and necrosis of the nodules. These data demonstrate that IFN-alpha 2 and -gamma cooperate to potentiate the IFN antiproliferative activity.

Protection against herpes simplex virus infection in mice by recombinant murine interferon-beta in combination with antibody

A recombinant murine interferon -beta (rMuIFN-beta) was used to suppress the development of skin lesions and death of mice after challenge with herpes simplex virus (HSV) type 1 (HSV-1). Depilated female BALB/c mice were inoculated intradermally with HSV-1, Hayashida strain, and were administered various concentrations of interferon (IFN) intraperitoneally 3 h later. The treatment with IFN was given once a day for 10 successive days. Under the conditions in which almost all control mice died after development of severe zosteriform skin lesions, the mortality of mice treated with IFN (8 X 10(5) or 8 X 10(4) U/mouse) was less than 50% (9/20 and 4/10, respectively), though all mice treated with a lower dose of IFN (8 X 10(3) U/mouse) died. Titration revealed that there was no significant suppression of virus growth by IFN in the skin or dorsal root ganglia, but it was significantly suppressed in the brain. The protective effect of IFN was enhanced when it was used in combination with human anti-HSV antibody having a neutralizing titer (NT) of 1:16. All mice treated with IFN (8 X 10(5) U/mouse) and antibody (NT, 1:16) survived, and only 40% of them developed slight zosteriform skin lesions. The effect of the combination was observed even when both IFN and antibody were diluted 1:10. The protective effect of IFN was also observed when athymic nude mice were used as the host. In this system, though the IFN-treated nude mice survived significantly longer than the controls, they finally died. In antibody- or acyclovir (ACV)-treated nude mice, there was also a prolongation of survival time as compared with control mice. The effect of antibody was enhanced by the addition of IFN, but IFN did not potentiate the effect of ACV.

Expression of interferon-inducible genes in RD-114 cells

RD-114 is a cell line which is partially responsive to interferon (IFN). Although both IFN-alpha and IFN gamma inhibit production of the resident retrovirus, they do not inhibit replication of other viruses, such as vesicular stomatitis virus and encephalomyocarditis virus, in these cells. In the studies reported here, we studied the characteristics of induction of seven IFN-inducible mRNAs in RD-114 cells. We observed that mRNAs 561, 6-16, 1-8, 2A, and 6-26 have similar induction characteristics in RD-114 cells and in HeLa cells, a fully responsive line. mRNA 2'-5'-oligo-adenylate synthetase (2-5(A) synthetase), however, was induced more efficiently by IFN-alpha in HeLa cells than in RD-114 cells. The same was true for the induction of metallothionein II mRNA by IFN-gamma. However, the latter mRNA was induced equally strongly in both lines when ZnCl2 was used as the inducer, suggesting that the gene is not defective in RD-114 cells. Although IFN-alpha induced 2-5(A) synthetase mRNA poorly and IFN-gamma did not induce it at all in these cells, a mixture of IFN-alpha and IFN-gamma induced this mRNA quite effectively, to a level of induction comparable to that in HeLa cells. Only 1 U of IFN-gamma per ml was sufficient to elicit this synergism, and the data suggested that an IFN-gamma-inducible protein was needed for this process. Induction of mRNA 561 by IFN-alpha in RD-114 cells, unlike that in HeLa cells, did not need ongoing protein synthesis. Once induced, this mRNA turned over rapidly in both cell lines, and this turnover could be slowed down by inhibiting protein synthesis in either cell line. IFN-induced mRNAs, such as 561 and 1-8, were polysome associated in IFN-treated RD-114 cells, suggesting that they were actively translated. Therefore, it is unlikely that the products of these IFN-inducible genes, by themselves, mediate the inhibition of replication of those viruses which are insensitive to IFN action in RD-114 cells.

Experimental studies on the combined effects of alpha and gamma interferons against human tumor xenografts transplanted into nude mice

The antitumor activities, resulting from the combined treatment of leukocyte interferon (IFN-alpha), with recombinant human immune interferon (IFN-gamma), against human tumor xenografts in nude mice, were studied. Nine human tumor xenografts, (7 from gastric carcinoma, 1 from gallbladder carcinoma and 1 from breast carcinoma), were serially transplanted into nude mice for the purpose of this experiment. Each human tumor xenograft was inoculated subcutaneously into BALB/c nu/nu nude mice and treatment was started after the estimated tumor had reached 100-300 mg. IFN was administered intramuscularly at a schedule of qd X 14. Treatment with either IFN-alpha or IFN-gamma alone, did not produce any antitumor effect against the various human tumor xenografts, however the combination of IFN-alpha with IFN-gamma resulted in achieving significant antitumor effects against the various human tumors. Inhibition of tumor growth was observed in 7 of the 9 tumors (77.8 per cent), and regression of the tumor was noted in 5 of the 9 tumors (55.6 per cent).

Neuropeptides modulating macrophage function

The immune system and the neuroendocrine system affect each other via molecules and receptors shared by both systems. Neuroendocrine hormones may act either positively or negatively in regulating the activities of a key cell of the immune system, the macrophage. For example, adenocorticotropic hormone (ACTH), somatostatin, and substance P are all capable of increasing the cytotoxicity of macrophages against tumor cells. However, ACTH and somatostatin, but not substance P, can also block the tumoricidal activity of macrophages induced by recombinant gamma interferon (IFN-gamma), a non-neuroendocrine immunomodulating hormone. In contrast, substance P increased tumoricidal activity, both independent of IFN-gamma and in addition to IFN-gamma. Neurotensin, alpha-endorphin, beta-endorphin, met-enkephalin, vasopressin, and substance K did not affect tumoricidal function, either alone or in combination with IFN-gamma. Substance P, but not the other neuropeptides, increased substantially the proportion of macrophages able to secrete superoxide ions, suggesting a possible influence on macrophage capacity to deal with microbial infection. Such positive and negative modulation of macrophage effector functions could contribute to the influence of cognitive stimuli in infection and neoplasia.

Transcriptional analyses of interferon-inducible mRNAs

Using nuclear runoff transcription assays we demonstrated that alpha interferon-mediated induction of transcription of four mRNAs in HeLa monolayer cells needed ongoing protein synthesis and that such a need could be obviated by pretreating the cells with gamma interferon which, by itself, did not induce transcription of these mRNAs. In another human cell line, RD-114, synthesis of alpha interferon-inducible mRNA 561 did not need ongoing protein synthesis. In this line, however, in which interferon inhibits replication of some viruses but not of others, transcription of two of the six interferon-inducible mRNAs that we examined was not appreciably enhanced by interferon.

Clinical and laboratory changes induced by alpha interferon in chronic lymphocytic leukemia--a pilot study

Ten chronic lymphocytic leukemia patients were treated with partially pure alpha interferon (IFN-alpha) at doses ranging from 3-9 X 10(6) units administered intramuscularly daily. Of these patients, three patients with disease stages 0, 1, and 3 (and prolymphocytic leukemia), respectively, responded with partial remissions lasting from 10 to 24+ months; four additional patients had minor responses. Among those responding, modulation of B cell chronic lymphocytic leukemia, surface immunoglobulins, and surface antigens were observed in four patients. These changes included a decline in the proportion of B cells bearing surface immunoglobulin without change in the number of the B cells. Likewise, a decline in the proportion of B cells bearing T-1 antigen was observed in three patients. Increase in the percentage of T cells, primarily the T helper cells, was seen in two of the responding patients. Specific binding of alpha interferon was demonstrated prior to therapy in CLL cells of all patients. This binding declined rapidly following treatment with IFN-alpha. Induction of the enzyme 2'5' oligoisoadenylate synthetase was examined in CLL patients prior to and during therapy with IFN-alpha. Variable levels of the enzyme were induced in all patients on therapy; however, only minimal induction was observed in two of three patients failing therapy.

Interferon treatment of renal cell carcinoma. Current status and future prospects

Studies with various interferon alpha preparations, including interferons induced in human leukocytes, interferon alfa-N1, interferon alfa-2a, and interferon alfa-2b, have all provided evidence for modest but reproducible antitumor activity in advanced renal cell carcinoma. Review of the data suggests that maximal response rates are achieved when interferon alpha is administered within a fairly restricted range of moderate to high doses, whereas extremely low or extremely high dosage regimens appear less likely to induce therapeutic response. Preliminary evidence suggests that interferons beta and gamma may also induce regression of metastatic renal cell carcinoma. Recent in vitro and animal studies have shown that combinations of interferon gamma with interferon alpha or interferon beta, produce synergistic biologic activities, suggesting that the various interferons may have different pathways of action related to agent-specific cellular receptors. Possible interactions of different interferon species given concurrently to patients with renal cell carcinoma are under investigation, as are combinations of interferon alpha with chemotherapeutic agents. Despite in vitro data suggesting enhanced antiproliferative activity for the combination of interferon alpha and vinblastine, most clinical studies of this combination have proved to be no more effective than interferon alpha alone, but they have provided evidence of increased toxicity. The recent identification and purification of other biologically active cytokines, such as tumor necrosis factor and interleukin-2, and of monoclonal antibodies that recognize unique cell surface antigens on renal carcinoma cells, provide exciting possibilities for combination regimens with various interferon species.

Three consecutive phase II studies of recombinant interferon alfa-2a in advanced malignant melanoma. Updated analyses

In three consecutive Phase II trials of recombinant interferon alfa-2a (rIFN alfa-2a; Roferon-A Hoffmann-La Roche, Nutley, NJ) involving 96 patients with advanced malignant melanoma, an overall response rate of 22% was observed. For all study participants, the median time to disease progression was 1.7 months, and the median survival was six months. Most regressions occurred within one month of commencing therapy, were usually limited to soft tissue metastases, and were transient. However, responses in three patients were long term, lasting 32+, 36+, and 41+ months. A thrice weekly intramuscular dose of 50 x 10(6) U/m2 produced an intolerable flulike illness concomitant with a median weight loss of 5.6 kg. The addition of cimetidine to the same dose in 35 patients was of no therapeutic value. A dose of 12 x 10(6) U/m2 produced clinically acceptable toxicities, and a median weight loss of 2.1 kg. There was no apparent dose response relationship, nor were there any obvious sequelae from antibody formation to interferon alfa-2a. As single agent therapy in malignant melanoma, interferon alfa-2a was only marginally useful in most patients. Nevertheless, combination regimens of this agent with cytotoxic agents, alternative molecular species of interferon, and lymphokines, notably tumor necrosis factor, offer a conceptually intriguing dimension in the design of future clinical trials.

Future developments in interferon therapy

The antitumour effects of interferons in animals and humans are well known. Despite the fact, however, that the 3 types of human interferon, leukocyte alpha-interferon, fibroblast beta-interferon and immune gamma-interferon are available in large amounts through recombinant DNA technology, the practical applicability of interferon therapy in cancer is still not clear. An initial approach to this problem is to determine the mechanism of action of interferons and to find out why, in certain circumstances, they are inactive. There are various ways in which interferon may control tumours--i.e. antiviral action, inhibition of cell growth, stimulation of cell differentiation, changes in cells modulating the susceptibility to immune rejection, or effects on the host immune systems (natural killer system and cytotoxic proteins). The implications of these data in the use of interferon in cancer therapy need to be evaluated. Both alpha- and beta-interferons may have beneficial effects on growth inhibition and differentiation, but gamma-interferon is probably more effective in boosting the immune recognition and rejection of tumour cells. A combination of alpha- and gamma-interferon may give the best results in vivo, since they often act synergistically in vitro. The sensitivity of individual tumour cells to the various types of interferon needs to be evaluated by measurement of oncogenes mRNA inhibition, G0/G1 arrest and increase in various H-La antigens. Finally, the aim of any treatment (antiviral action, tumour regression, prevention of metastasis, decreased tumour growth and increased cell differentiation) should be an important consideration in whether interferon therapy is chosen. A major problem remains in understanding why only a small proportion of patients usually show an objective response to interferon.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcriptional analyses of interferon-inducible mRNAs

Using nuclear runoff transcription assays we demonstrated that alpha interferon-mediated induction of transcription of four mRNAs in HeLa monolayer cells needed ongoing protein synthesis and that such a need could be obviated by pretreating the cells with gamma interferon which, by itself, did not induce transcription of these mRNAs. In another human cell line, RD-114, synthesis of alpha interferon-inducible mRNA 561 did not need ongoing protein synthesis. In this line, however, in which interferon inhibits replication of some viruses but not of others, transcription of two of the six interferon-inducible mRNAs that we examined was not appreciably enhanced by interferon.

The potency of interferon-alpha 2 and interferon-gamma in a combination therapy of dendritic keratitis. A controlled clinical study

Forty-five patients with virologically confirmed dendritic keratitis were treated in a randomized, double-blind controlled study with a basic therapy of trifluorothymidine (TFT) eye drops. In addition they received different human recombinant interferon (rHu IFN) eye drops. The following results were obtained for average healing times: TFT plus one drop daily of rHu IFN-alpha 2 arg (30 million iu/ml): 3.3 days, TFT plus rHu IFN-gamma (30 million iu/ml): 3.9 days, TFT plus a mixture of alpha plus gamma (0.3 million iu/ml each): 6.1 days, TFT plus a mixture of alpha plus gamma (1.5 million iu/ml each): 3.3 days. High-titer gamma interferon did not significantly differ from high-titer alpha interferon in the combination therapy of dendritic keratitis. A mixture of alpha plus gamma at a moderate titer (1.5 million iu/ml each) was as effective as a high-titer mono-preparation. Adding a low-titer interferon mixture gave no better therapeutic results than antiviral monotherapy. Thus it seems possible to save about 90% of interferon commonly used in the combination therapy of dendritic keratitis by applying a mixture of different suitable interferons instead of interferon monospecies.

Regulation of synthesis and turnover of an interferon-inducible mRNA

Regulation of synthesis and turnover of an interferon (IFN)-inducible mRNA, mRNA 561, in HeLa monolayer cells was studied. Cytoplasmic levels of this mRNA were estimated by hybridization analyses with a cDNA clone that we have isolated as a probe. IFN-alpha A induced a high level of this mRNA in a transient fashion, whereas no induction was observed in response to IFN-gamma. Surprisingly little mRNA 561 was induced in cells treated simultaneously with IFN-alpha A and an inhibitor of protein synthesis, suggesting that in addition to IFN-alpha A, an interferon-inducible protein was needed for induction of this mRNA. Apparently this putative protein could be induced by IFN-gamma as well. Thus, although little mRNA 561 was synthesized in cells treated either with IFN-gamma alone or with IFN-alpha A and cycloheximide, a large quantity of this mRNA was induced in cells which had been pretreated with IFN-gamma and then treated with IFN-alpha A and cycloheximide. Once mRNA 561 was induced by IFN-alpha A, it turned over rapidly. This rapid turnover could be blocked by actinomycin D or cycloheximide indicating that another IFN-inducible protein may mediate this process.

Antiproliferative effects of interferons on human melanoma cells in the human tumor colony-forming assay

The human tumor colony-forming assay (HTCFA) is an in vitro test that has been used to predict the activity of anticancer drugs against a patient's tumor. We utilized the assay to analyze the antiproliferative effects of seven interferons (IFNs) against 40 human melanomas to determine which IFN had the greatest antiproliferative activity in this drug-resistant tumor. IFNs studied included recombinant IFN-alpha 2; human lymphoblastoid IFN; IFN-alpha Cantell; native beta RPMI; two recombinant IFNs-beta; and recombinant IFN-gamma. Growth was sufficient [greater than 30 tumor colony-forming units (TCFU)/well] for assessing the antiproliferative effects of at least one IFN in 25 tumors (63%). A dose-response relationship was demonstrated by all IFNs in tumors in which some activity was observed (p less than or equal to 0.01). Individual melanomas differed in their sensitivities to the various IFNs. Overall, however, none of the IFNs was markedly more effective in antiproliferative effects than any other, although there was a trend toward IFN-beta ser having more potent antiproliferative properties when compared to IFN-alpha 2 (p = 0.055). Twelve of 13 tumors exposed to combinations of IFN-beta ser and IFN-gamma demonstrated a synergistic antiproliferative effect. In all but two of these, low concentrations of each IFN (less than or equal to 50 U/ml), when combined, resulted in 85-95% inhibition. As prolonged exposure to high concentrations of IFN are often not clinically tolerable, these data suggest that IFN combinations may be one way of achieving more clinically meaningful IFN doses, schedules, and regimens, provided antiproliferative effects are of importance in vivo.

Interferons and tumor necrosis factors have similar catabolic effects on 3T3 L1 cells

The effect of a variety of cytokines on lipid metabolism in 3T3 L1 mouse fibroblasts and adipocytes was studied. Uptake of [3H]acetate by adipocytes and heparin-releasable lipoprotein lipase activity was inhibited after treatments of the cells with picomolar concentrations of recombinant human tumor necrosis factor alpha (rHuTNF-alpha), human tumor necrosis factor beta (rHuTNF-beta, also called lymphotoxin), murine interferon-gamma (rMuIFN-gamma), and a human hybrid interferon-alpha [rHuIFN-alpha 2/alpha 1 (Bgl II)]. Recombinant human interferon-gamma (rHuIFN-gamma), natural human colony-stimulating factor (HuCSF), and human interleukin 2 (HuIL-2) had no effect. Similar though less-marked suppression of [3H]acetate uptake by cytokines was seen in 3T3 L1 fibroblasts. Cytokines inhibited the incorporation of [3H]acetate into both membrane and storage lipids in the adipocytes. In addition to blocking lipid uptake and synthesis, rHuTNF-alpha and -beta, and rMuIFN-gamma stimulated the release of free fatty acid into the medium from adipocytes. Binding studies suggest that rHuTNF-alpha and rHuTNF-beta compete for the same cell-surface receptor on 3T3 L1 adipocytes, while rMuIFN-gamma binds to a separate receptor. The binding of rTNF-alpha to both adipocytes and fibroblasts can be significantly enhanced by preexposure of the cells to rMuIFN-gamma. There appear to be both high- and low-affinity receptors for rHuTNF-alpha on adipocytes, whereas fibroblasts exhibit a single class of high-affinity receptors. These results suggest that a variety of structurally distinct cytokines possess lipid mobilization activity, which may be of critical importance to the host in defense against infection or malignancy.

Enhanced production of gamma-interferon by therapy with parenteral OK-432 and alpha-interferon in patients with head and neck cancer

Although the drug OK-432 can induce the release of gamma-interferon (IFN-gamma), the serum concentrations of IFN-gamma produced are very low. We studied the effects of combining OK-432 with alpha-interferon (IFN-alpha) on the endogenous production of IFN and the postoperative courses of patients with oral cavity cancers. Forty patients operated on for head and neck cancers were studied. Each patient was given an injection of OK-432 1 week after surgery. Between 10 and 14 days later, a combination of OK-432 and IFN-alpha was given to assess the effects of the concomitant use of IFN-alpha on IFN production. In 18 of the 30 patients given a large dose of IFN-alpha (3 or 5 X 10(6) IU/mg protein), IFN production induced by OK-432 was enhanced. A small dose of IFN-alpha (7 X 10(3) IU) did not enhance the action of OK-432. OK-432 also induced the release of both endogenous IFN-gamma and IFN-alpha, and the production of both types of IFN was enhanced by the concomitant administration of parenteral IFN-alpha. Next, 50 patients operated on for oral cavity cancers were given OK-432 or a combination of OK-432 and IFN-alpha for 4 months, and their postoperative courses were followed for 2-5 years. The clinical courses were better in the combined therapy group than in the group given OK-432 alone.

Quantitation of in vivo potentiation resulting from combined interferon therapy: antitumor effect against B-16 melanoma in mice

In this study, murine interferons (IFNs) were employed separately and in combination at subeffective and effective antitumor concentrations in a mouse B-16 melanoma system. Murine IFN-gamma (MuIFN-gamma) was demonstrated to be approximately 20 times more potent than MuIFN-alpha and MuIFN-beta in this system. Potentiation was observed with combinations of both subeffective and effective concentrations of MuIFN-gamma with MuIFN-alpha or MuIFN-beta. The level of potentiation was observed to increase from undetectable to two-fold to fourfold with three increasing IFN concentrations. Thirty percent of the mice treated for 14 days with 332 U/day MuIFN-gamma plus 7,500 U/day MuIFN-alpha survived apparently tumor-free for 100 days. Forty percent of the mice treated for 14 days with 332 U/day MuIFN-gamma plus 7,500 U/day MuIFN-beta survived apparently tumor-free for 100 days. All control mice died by day 41. The results are consistent with the suggestion that combination IFN therapy may have some use in the control of at least some tumors in humans.

Effect of interferon on replication of herpes simplex virus types 1 and 2 in human macrophages

Macrophages derived from human peripheral blood and cultured for 1 week were permissive for the replication of herpes simplex virus (HSV) types 1 and 2. Low titers of interferon (IFN) were produced after virus infection. The yield of infectious virions was reduced by pretreatment of cells with natural and recombinant IFN-alpha and natural IFN-beta. Recombinant and natural IFN-gamma exhibited very low antiviral activity. Treatment of cells with IFN-gamma mixed with IFN-alpha or with IFN-beta did not result in a synergistic inhibition of virus yield. We studied the synthesis of HSV type 1- and HSV type 2-coded proteins in macrophages treated with IFN-beta. Induction of the HSV beta-protein DNA polymerase was strongly inhibited in IFN-treated cells in a dose-dependent manner. As shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, other beta- and gamma-proteins of HSV were inhibited as well. Immunofluorescence studies revealed a strong inhibition of the expression of immediate early alpha-protein ICP4. The results indicate that IFN acts early during the viral replication cycle to inhibit the synthesis of HSV alpha- and beta-proteins.