[Therapeutic use of interferons and their toxicity. Focus on peripheral neuropathy]

When evaluating the tolerability profile of interferons, the authors focus their attention on peripheral neuropathy, by assessing the epidemiological, pathogenetic, clinical, and outcome aspects, in relation with the administration of these drugs and the concurrent increase of risk factors associated with underlying diseases (including chronic viral hepatitis, solid organ malignancies, hematological disorders, autoimmune diseases, HIV infection). Even though it is often impossible to exclude a direct or indirect interferon-associated pathogenetic pathways in the occurrence of peripheral neuropathies, predominatly through immune-mediated mechanisms, the episodes reported by the international literature are steadily on the rise, paralleling the enlargement of therapeutic indications, and the availability of novel interferon formulations for clinical use. The increased indications of interferons in a broadening spectrum of clinical disorders, and especially their use in chronic hepatitis, recommend a strict monitoring of all possible adverse events, in order to reach a better epidemiological, pathogenetic, and clinical awareness of clinical events which are still infrequent, but potentially severe, such as those involving the peripheral nervous system.

High-risk surgically resected pediatric melanoma and adjuvant interferon therapy

BACKGROUND

Pediatric patients with high-risk surgically resected melanoma are at risk for relapse, yet little is known about these young patients and how they tolerate high-dose interferon therapy.

PROCEDURE

We reviewed medical records of patients (< or =18 years) with high-risk melanoma referred to the University of Michigan Pediatric Hematology-Oncology service between January 1989 and July 2003.

RESULTS

Fourteen patients were identified with high-risk resected melanoma. The median age at diagnosis was 8.5 years. The median time to establish diagnosis was 9 months. Primary lesions were diagnosed as unequivocal melanoma, atypical epithelioid melanocytic proliferations, or atypical Spitz tumor with indeterminate malignant potential. Twelve patients had a positive sentinel lymph node (SLN) biopsy or a palpable regional lymph node and underwent regional lymph node dissection (LND). Two patients with unequivocal melanoma with Breslow depth >4 mm had negative SLN biopsies. Twelve patients received adjuvant high-dose interferon. The following toxicities were observed: constitutional symptoms, gastrointestinal symptoms, depression or neuropsychiatric symptoms, myelosuppression, elevated AST or ALT, hypothyroidism, and hypertension. Grade 3 or 4 toxicities were uncommon with exception of neutropenia, resulting in modification of therapy in one patient. All patients are alive and free of disease at follow-up (median 24.5 months).

CONCLUSIONS

Invasive melanoma can occur in very young children. Despite early signs of malignancy, there is often a delay in diagnosis. Histologically, diagnosis may be difficult because of overlap with Spitz nevi. Pediatric patients tolerated adjuvant high-dose interferon well and may be less likely than adults to require therapy modification secondary to toxicities.

[Wound-healing properties of solid immunobiological medicinal forms for local application]

The results of experiments on rats showed a high healing potential of three collagen-based coating materials containing a combination of biologically active substances including human leukocyte interferon, alfalfa extract, and eubiotic bactisporin. The application of new materials significantly accelerated the healing of model wounds.

Sustained suppression of hepatitis C virus by interferon and ribavirin in hemophilic patients not responding to interferon monotherapy

Thirty-nine hemophiliac patients, negative for human immunodeficiency virus, with chronic hepatitis C who failed to respond to interferon (IFN) at 3 million units (MU) given subcutaneously thrice weekly for at least 3 months were retreated with 5 MU IFN for 6 months followed by 3 MU IFN in combination with daily oral doses of 1 or 1.2 g ribavirin. Thirty-four patients (87%) completed the study. In 4 patients treatment was discontinued because of treatment-related symptoms; 1 patient dropped out. Dosage reduction was required in 10 patients (26%) because of ribavirin-related anemia or IFN-related side effects. By intention-to-treat analysis, 14 (37%) had a sustained virologic response with preference for those infected by genotypes other than type 1 (43% versus 12%) and with high transaminases levels (168 U/L versus 116 U/L). Thus, IFN and ribavirin combination therapy led to a sustained suppression of hepatitis in one third of hemophiliac patients resistant to conventional monotherapy.

Fate of chronic myeloid leukemia patients treated with allogeneic bone marrow transplantation or chemotherapy and/or interferon at a single center: long-term results

From April 1981 to February 2000, 105 patients with chronic myeloid leukemia (CML) underwent BMT from HLA-identical related donors at a single center. Eighty-eight patients were in chronic phase (CP), 11 patients in accelerated phase and six patients in blast crisis. Ten of these patients received a second BMT (BMT2). Comparison of BMT in CP with chemotherapy and/or alpha-IFN (n=70) was also made. Patients were given cyclophosphamide (CY) and single-dose TBI (CYTBI, n=38) or busulfan (BU) and CY (BUCY, n=67). Overall 54 patients are alive and 52 of them are disease-free with a median follow-up of 11.3 (range 1.1-19.4) years. Ten-year disease-free survival (DFS) in CP patients was better after BUCY, 61% (95% CI, 47-68%) than after CYTBI, 41% (95% CI, 23-61%) (P=0.07). For 88 patients who received a transplant in CP, results were significantly improved when BMT was performed within 1 year after diagnosis (P=0.02) or at an age < or = 25 years old (P=0.01). Ten-year survival in patients who received BMT in CP was better than in patients treated with chemotherapy (56% vs 10%; P=0.0001) or alpha-IFN-based treatment (33%; P=0.09) with survival curves crossing at 4.2 years and at 4 years, respectively. The probability of DFS after BMT2 was 60% (95% CI, 26-87%). CP patients who received BMT after CYTBI had a higher probability of relapse and transplant-related mortality than patients receiving BUCY (53% and 58% vs 9% and 34%; P=0.002 and P=0.08, respectively). All but six patients are currently on no medication and have resumed all activities without any limitation. These long-term results confirm that allogeneic BMT is the only curative approach for CML patients and should be offered to all patients with a suitable donor as soon after diagnosis as possible.

Effective and safe interferon treatment for Japanese patients with chronic myelogenous leukemia relapse after bone marrow transplantation. The Nagoya Blood and Marrow Transplantation Group

The purpose of this study was to assess the efficacy and safety of interferon (IFN) treatment in patients with a relapse of chronic myelogenous leukemia (CML) after bone marrow transplantation in Japan. Accordingly, we retrospectively analyzed the results obtained from 8 patients treated with IFN by the Nagoya Blood and Marrow Transplantation Group. One of 3 patients with hematologic relapse and all 5 patients with cytogenetic relapse achieved complete cytogenetic response (CCR). The median time to achieve CCR was 8 months (range, 3-16 months). One patient relapsed 9 months after starting IFN and died of blast crisis. CCR was maintained for a median duration of 47 months (range, 9-79 months) in the remaining 5 patients. The median duration of survival of these 5 patients after starting IFN was 58 months (range, 12-89 months). At the time of this report, 2 patients who did not attain CCR have survived for 81 months and 142 months after starting IFN, respectively. During IFN treatment, 1 patient showed a transient deterioration of chronic graft-versus-host disease, and no treatment-related deaths were observed. These results suggest that treatment with IFN for CML patients who relapse after bone marrow transplantation is effective and safe. A prospective study to compare IFN with donor lymphocyte infusion is necessary to establish the optimal strategy for the treatment of CML patients who relapse after bone marrow transplantation.

Collection of Ph-negative progenitor cells from interferon responsive patients with chronic myeloid leukemia: effect of granulocyte-colony-stimulating factor mobilization

BACKGROUND AND OBJECTIVE

The observation that patients with chronic myeloid leukemia (CML) may relapse following stem cell transplantation because of Philadelphia positive cells contaminating the graft have led to a variety of strategies to reduce this contamination. This study investigate the feasibility of collective, Ph-re cells from patients with CML in chronic phase.

DESIGN AND METHODS

A total of 18 patients with chronic myeloid leukemia in chronic phase who had responded to varying degrees to treatment with interferon-a (IFN) were subjected to mobilization with granulocyte colony-stimulating factors and peripheral blood progenitor cell collection. Nine patients were in complete cytogenetic remission (CCR) and nine were partial responders. IFN was stopped 2 to 4 weeks before the procedure. G-CSF was given by subcutaneous injection once daily at a dose of 10 microg/kg.

RESULTS

Five patients underwent one collection procedure only, 10 underwent two procedures and 3 patients had three collections. The median number of nucleated cells (NC) per patient collected was 10.2 x 10(8)/kg (4.4-19.7) and the median number of CD34(+) cells was 2.5 x 10(6)/kg (0.4-9.4). Analyzable cytogenetic data were available for 26/34 (76%) leukapheresis procedures. The median percentage of Ph- negative metaphases for patients in CCR was 100% (73-100). Patients not in CCR had a higher level of Ph-positive cells in their collections (median 23%, range 0-79%, p=0.01). Of the nine patients in CCR, 8 had at least one apheresis from which progenitor cells were 100% Ph-negative; conversely, patients not in CCR had detectable Ph-positive cells in every collection. Four patients have undergone autologous stem cell transplantation.

INTERPRETATION AND CONCLUSIONS

It was possible to collect sufficient Ph negative progenitor cells from patients in CCR but collections from other patients contained significant numbers of Ph-positive cells.

Endocrine and neurological adverse effects of the therapeutic interferons

There is experimental evidence that the nervous central and the neuroendocrine systems can influence the immune system, which can in turn influence the brain activity. Endogenous cytokines are known to play a critical role in the pathophysiology of many diseases. The recently acquired experience on the adverse effects of therapeutic cytokines, particularly neurological and endocrine adverse effects, are further illustrative of these interferences. Interferons-alpha have been used in thousands of patients, so that the information accumulated with this group of closely related products is essential to delineate the potential and severity for non-immunological, but largely immune-mediated adverse effects to develop in patients treated with immuno-activating agents.

[Therapeutic aspects in the management of hairy cell leukemia]

CHRONIC B CELL PROLIFERATION: An estimated 80 to 120 new cases of hairy cell leukemia are diagnosed annually in France. Median survival is 5 years for untreated patients who develop a series of infectious complications. For many years, interferon alpha was the standard therapy but the therapeutic strategy has changed with the arrival of purine analogs, deoxycoformicine and 2-CdA.

THERAPEUTIC OPTIONS

We searched Medline, Pascal, and Current Contents for literature on the treatment of hairy cell leukemia over the last 10 years and discuss here available data on response rate, mechanism of action and adverse effects of different therapeutic options. BY TREATMENT: Interferon generally induces partial response and most patients relapse after treatment withdrawal. The purine analogs, desoxycoformycine and 2-chlorodeoxyadenosine, are more active than interferon inducing response in approximately 90% of the cases, even after interferon failure, complete response is achieved in 50% to 70% of patients. Relapse rate at 5 years appears to be limited to 10% n 15%. Besides infections, the main adverse effect is the constant deep and persistent decline in CD4 counts but with no special risk of opportunistic infection. The increased rate of secondary cancers in long-term survivors and its possible relationship with treatments remains a controversial topic.

Interferon as maintenance therapy in refractory malignant lymphoma

Patients with refractory malignant lymphoma (RML) have a poor prognosis when treated with conventional chemotherapy, as less than 20% remain alive and free of disease after 5 years. The use of myeloablative chemotherapy followed by BMT has improved the complete remission (CR) rate. Nevertheless, relapse rates remain unchanged, and only a few patients remain alive and free of disease for more than 3 years. For this reason, we began a prospective randomized clinical trial to determine if IFN-alpha2B (5.0 MU three times a week for 1 year) can improve the prognosis in RML. Ninety-six patients with high or high-intermediate clinical risk RML and in CR after intensive chemotherapy were randomly assigned to receive or not to receive IFN as maintenance therapy. A median follow-up of 48.1 months, the time to treatment failure and survival were similar in both groups. Toxicity secondary to IFN administration was mild, and all patients received the planned doses of IFN. We conclude that IFN is not recommended at this dose and schedule as maintenance therapy in patients with RML who achieve CR. Different therapeutic approaches may be developed to improve outcomes for these patients.

Unanticipated human toxicology of recombinant proteins

Recombinant human proteins play already an important role in therapy, e.g. erythropoietin and colony stimulating factors, while several promising candidates such IL-6, IL-12, thrombopoietin and others are in clinical development. Since the recombinant proteins are copies of endogenous proteins, it was assumed that they would be well tolerated. While this assumption is correct for some, other proteins proved to be a highly toxic. Therefore, preclinical safety assessment of these proteins is necessary. Based on the experience with several proteins, some guidance for the safety assessment can be given. Furthermore, data are presented demonstrating that preclinical toxicity studies have a predictive value for man. Limitations of the classical approach of safety tests and new concepts are discussed.

[Interferons in the therapy of solid tumors]

Belonging to the vast family of cytokines, interferons (IFN) have recently been widely investigated concerning their possible clinical applications, both in virology and oncology. In this field results have been quite mixed but definitely encouraging. The best achievements have been obtained in hematology, and particularly in the treatment of hairy cell leukemia and chronic myelogenous leukemia, but new perspectives have also opened in the therapy of solid tumors, especially in the local treatment of superficial bladder cancer and ovarian cancer, AIDS-related Kaposi's sarcoma and malignant melanoma. IFN have in certain cases showed an efficacy comparable to that of classic treatments but with lower toxicity, and in some tumors they have even improved the results obtained so far, especially in combined therapy. We have here gathered the most recent results concerning the use of IFN in the therapy of solid tumors in order to highlight the new therapeutic opportunities available to clinical oncology.

21-day intravenous toxicity study with feline interferon in rats

The toxicity of recombinant feline interferon, a prospective antiviral drug for cats, was examined in a subacute study. Groups of five male and five female Wistar rats were given iv feline interferon in 20 mM-NaCl at doses of 0, 5, 15 and 50 MU/kg body weight/day for 21 consecutive days. Criteria to assess toxicity included clinical observations, ophthalmoscopy, growth, food and water intake, haematology, clinical chemistry, urinalysis, organ weights, gross examination at autopsy and microscopic examination of the liver, kidneys, spleen, adrenals, heart, mesenteric lymph nodes and thymus. No treatment-related were observed even at the highest dose level. The no-observed-adverse-effect level for feline interferon in this study was therefore 50 MU/kg body weight/day.

Comparative susceptibility to mouse interferons of Rickettsia tsutsugamushi strains with different virulence in mice and of Rickettsia rickettsii

Three strains of Rickettsia tsutsugamushi (Karp, Gilliam, and TA716, representing three virulence types in mice) were examined for their sensitivity to the inhibitory effects of recombinant gamma interferon (IFN-gamma) and purified IFN-alpha/beta in two cultured mouse fibroblast cell lines. The susceptibilities of another species, Rickettsia rickettsii, and of encephalomyocarditis virus (EMCV) were also tested for comparative purposes. IFN-gamma inhibited rickettsial replication in only one of the six combinations of R. tsutsugamushi strains and mouse cells (strain Gilliam and the BALB/c mouse-derived cell line). In contrast, R. rickettsii and EMCV replication were markedly inhibited in both cell types, but to a greater extent in the BALB/c line than in the C3H cells. IFN-alpha/beta (300 to 450 U/ml) was uniformly ineffective in three of the combinations of R. tsutsugamushi strains and mouse cells (Gilliam in C3H cells and Karp in both C3H and BALB/c cells); in the remaining sets, IFN-alpha/beta-mediated inhibition of rickettsial replication was variable and in no case was it very pronounced. The tests with R. rickettsii in both cell types also indicated slight, variable sensitivity to IFN-alpha/beta. EMCV, on the other hand, was very susceptible to IFN-alpha/beta, confirming the potency of the preparation used; as with IFN-gamma, virus replication was inhibited to a greater degree in the BALB/c cell line than in the C3H cultures. These results are discussed in terms of their relationship to the virulence properties of the R. tsutsugamushi strains in BALB/c and C3H mice and to the known IFN-sensitivities of the more widely studied Rickettsia prowazekii.

Bacteria-infected fibroblasts have enhanced susceptibility to the cytotoxic action of tumor necrosis factor

The susceptibility of bacteria-infected fibroblasts to the cytotoxic action of tumor necrosis factor was investigated. L cells infected with Shigella flexneri, Salmonella typhimurium, or Listeria monocytogenes, had an enhanced susceptibility to the cytotoxic activity of TNF-alpha. This enhanced susceptibility was dependent upon the challenge dose of bacteria, the concentration of TNF, and upon the exposure time of bacteria-infected cells to TNF. L cells infected with S. flexneri were susceptible to the cytotoxic action of TNF at 2 to 6 h after bacterial infection. In contrast, L cells infected with S. typhimurium or L. monocytogenes did not show enhanced susceptibility to TNF until 14 h postbacterial infection and exposure to TNF. Enhanced susceptibility to TNF was dependent on bacterial invasion because fibroblasts pretreated with a noninvasive isogenic variant of S. flexneri, UV-treated invasive bacteria, bacterial cultural supernatant, or bacteria LPS were no more susceptible to TNF than untreated cells. Enhanced susceptibility to TNF by bacteria-infected cells was not unique to L cells. Mouse embryo fibroblasts and HeLa cells also showed similar reactivities after bacteria infection. Bacteria-infected cells were greatly suppressed in host cell protein synthesis that may play an important role in their enhanced susceptibility to TNF. These results suggest that an important role of TNF in host defense against bacterial infections is its cytotoxic activity against bacteria-infected cells.

Synergistic cytotoxic effects of recombinant human tumor necrosis factor, interferons, and heat-stress

A synergistic increase in the cytotoxic effects of recombinant human tumor necrosis factor (TNF-alpha), interferons (IFN-alpha, IFN-beta, and IFN-gamma) and heat-stress was demonstrated in vitro. The toxicity of these agents was assessed in the human cervical carcinoma HeLa cell line: the toxic effect was greatly increased when cells pretreated with IFNs or TNF were submitted to a 1-h heat-shock at 45 degrees C. Moreover if the heat-stress followed simultaneous treatment with both cytokines, a synergistic effect between these treatments could be observed. The same observations were made for two other transformed cell lines: the oral epidermoid carcinoma KB cells and the hepatocarcinoma PLC/PRF/5 cells. In contrast, the survival of normal cells (normal foetal lung MRC5 cells and foreskin F 7000 fibroblasts) was only slightly decreased by such treatments. These results suggest that combining a heat-stress with cytokines treatment might be one way of enhancing the sensitivity of cancer cells to the growth inhibitory effects of the individual cytokines.

Current view on the perspectives of interferon therapy

In recent years, impressive progress has been made towards the understanding of the molecular biology of interferon. Unfortunately, this progress was not accompanied by a parallel elucidation of the role of interferon in the animal organism. The feeling prevails that what we know about interferon today is only the peak of an iceberg showing interferon types and subtypes as a part of an insufficiently delineated system of cell-regulatory polypeptides (lymphokines, hormones) acting in a concerted way with other regulatory cells (such as NK-cells, macrophages) and their products (such as IL-2 etc.). An imbalance of this system may probably itself lead to disease (autoimmune diseases) and its disturbed functioning may hinder the therapeutic exploitation of its components in substitutive therapy (cancer).

Virus-related pathology: is the continued presence of the virus necessary?

This chapter examines the effect of viruses in inducing modifications in chromosomes, immune system interactions, and cell metabolism to support such a hypothesis that virus may no longer be present when the pathology appears. When vaccines were available to protect the population against the major epidemics, then chronic, recurrent, or persistent infections came into focus. Viruses are everywhere and all organisms are permanently exposed to them. The result of this contact depends on the particular moment a t which a given cell is exposed to the virus. Rubella, for example, provokes a very benign disease in adults, but can induce abnormalities in the differentiating fetus. Although interferon is active against virus aggression, excess interferon has a toxic effect and can block differentiation. The capacity of several viruses to act as cellular mutagens by modifying chromosomes is well established, whatever the molecular mechanism may be. Mutations at the cellular level were carefully analyzed for their tumorigenic potential.

Effects of interferon and encephalomyocarditis virus on in vitro development of preimplantation mouse embryos with and without the zona pellucida

Development of preimplantation mouse embryos, with or without the zona pellucida, in the presence of interferon (IFN) and mouse encephalomyocarditis (EMC) virus was studied using the in vitro culture method. The embryos (2- to 8-cell stages) were obtained from superovulated mice and cultured in modified Witten's medium under paraffin oil in 5% CO2 in air at 37 degrees C. Removal of the zona pellucida does not affect the subsequent development of the embryos: 90% of embryos with and 87% of embryos without the zona pellucida reached the morula-early blastocyst stages. Mouse IFN (10(4) units/ml) had no inhibitory effect on the developmental ability of the preimplantation embryos with or without the zona pellucida: 88 and 89% of the embryos in each group, respectively, reached the morula-early blastocyst stages. The preimplantation mouse embryos were sensitive to the embryotoxic effect of EMC virus: at a multiplicity of 20 infection particles per embryo the development of 43% of embryos was inhibited. The zona pellucida had no significant protective effect: Its removal changed only slightly the susceptibility of the preimplantation embryos to this virus. Pretreatment of embryos with IFN did not protect them from the embryotoxic effect of EMC virus. This work indicates that preimplantation mouse embryos appear to be resistant for both the antiviral and antiproliferative activities of IFN.

An overview of safety and regulatory aspects of the new biotechnology

New technology is producing new drugs and biologic products that present novel safety issues for the regulatory agencies. These products are produced using recombinant DNA or hybridoma techniques. Examples are growth hormone, antihemophilic factor, and interferon, produced by recombinant DNA. Very special proteins, namely, monoclonal antibodies, can be made by hybridoma technology that are extremely pure and potent. At present over two dozen in vitro monoclonal antibody products are approved by FDA and many more are expected. Regulating these products posed some new questions for the FDA, regarding the kinds of safety tests that should be done to establish reasonable levels of safety before clinical trials or marketing of these agents. The production methods are novel and thus require careful consideration to ensure that risks inherent in those methods do not cause disease when these products are administered to human subjects. A general overview of the regulatory safety issues of these new products is given.

Antiviral activities directed against wild-type and interferon-sensitive mengovirus

Two distinct antiviral activities can be detected in L cells treated with low levels of interferon and infected with a one-step interferon-sensitive mutant of mengovirus (is-1). The first antiviral activity (AVA-1) primarily delayed virus RNA and protein synthesis and thereby lengthened the virus replication cycle. It did not prevent cell death. The second antiviral activity (AVA-2) allowed the virus-induced inhibition of host macromolecular synthesis but inhibited all other virus functions. By 9 to 12 h post-infection host synthesis resumed and most cells survived. The data suggest that some step in the virus replication cycle activates AVA-2 leading to the destruction of the virus genome 6 to 12 h after infection. In unprotected cells the yields of parental virus (is+) and is-1 were similar. No qualitative or quantitative differences in virus products were observed by several techniques. The is-1 virus seems to have lost a wild-type function which normally blocks the action of AVA-2.

Interferon: pharmacokinetics and toxicity

Interferons disappear rapidly from the serum of animals and man, and the kidney may be the major site of interferon destruction. The relevance of serum levels of interferons to their therapeutic activity has not been clearly established, particularly as the stimulation of host defence mechanisms by interferons may be important. Relatively low serum levels of antiviral activity are seen after intramuscular injections of fibroblast interferon compared with those after the same dose of leucocyte interferon. Injections of very pure leucocyte and lymphoblastoid interferons from several sources cause fever, headaches, malaise and myalgia associated with a corticosteroid response and probably with inflammatory prostaglandin synthesis. These reactions become less with repeated dosing but very large doses of lymphoblastoid interferon have been shown to cause liver damage and serious metabolic disturbances. Treatment with moderate doses of exogenous interferons may occasionally be associated with the development of neutralizing antibodies.

Toxicity of interferon

The effects of partially purified human leucocyte interferon (PIF) and of a preparation purified by passage twice through a monoclonal antibody affinity chromatography column (NK21F) were compared with those of a control solution in healhty volunteers. After intramuscular injections both interferon preparations caused rises in pulse rate and body temperature, changes in circulating white cell counts, and various unpleasant symptoms, the most common of which were headache, malaise, and fever. Slightly lower doses of NK21F were given, and this was reflected in lower peak serum concentrations. Mean symptom scores, however, were not lower after NK21F than after PIF. Local inflammatory reactions eight hours after intradermal inoculations of these interferons were similar. Purification of interferon using a monoclonal antibody does not reduce the facets of its activity considered in this study. They are therefore inherent in the leucocyte interferon type selected by the antibody.

Electrophoretically pure mouse interferon inhibits growth, induces liver and kidney lesions, and kills suckling mice

Suckling Swiss mice were injected daily for 8 days with either electrophoretically pure (EP) mouse interferon (s.a. 4.7 x 10(8) units/mg protein), major impurities obtained in the course of purification, or partially purified mouse interferon (s.a. 1.3 x 10(7) units/mg protein). Only EP or partially purified interferon inhibited growth, induced liver and kidney lesions, and killed mice. The authors conclude that interferon itself is responsible for these effects.

Mechanisms in in vivo release of lymphokines. III. Separation of gamma-interferon (IFN gamma) from cytotoxicity in inbred strains of mice

Inbred strains of mice sensitized with BCG and challenged with old tuberculin (OT) vary in their capacity to release IFN gamma and MIF into circulation. Experiments were performed to correlate the presence of IFN gamma with that of the cytotoxic effect in an attempt to learn whether these two activities in the sera may be separated. Sera from eight inbred strains were obtained at times after challenge and assayed for IFN and for cytotoxic activity. A correlation did not exist between the titers of IFN gamma and the levels of cytotoxicity, i.e. sera from RF/J mice without detectable titers of IFN gamma had cytotoxic activity, while sera from C57BL/KsJ mice that had titers of IFN gamma were not cytotoxic. Regulation of IFN gamma titers could be achieved by administration of complete Freund's adjuvant to BCG sensitized mice. However, similar differences were not detected in cytotoxic activity. Therefore, IFN gamma may be released, or the activity of IFN gamma may be expressed in the circulation, in the absence of cytotoxicity.

[Method of increasing the activity of a preparation of human cadaver leukocyte interferon]

A simple method for increasing the activity of human leukocyte interferon is described. It is based on the removal from the native preparation of a presumed inhibitor of antiviral effect followed by condensation of the resulting fractions by thin-canal cells TCF-10 of an Amicon apparatus. With this method of concentration there was no loss of the general initial antiviral activity. Depending on the titer of the initial interferon and the condensation degree, the native interferon was concentrated 32--350-fold. The resulting concentrated interferon preparation is nontoxic, areactogenic, safe in animal trials and may be recommended for trials as a therapeutic-prophylactic means in various viral diseases.

Human fibroblast interferon in human neoplasia: clinical and laboratory study

Human fibroblast interferon (HFIF) produced on a large scale from normal diploid cell strains was highly purified and then evaluated as to its safety clinical investigation. The selective antiproliferative activity of HFIF was observed in vitro against certain human malignant cell lines and in vivo against human bladder tumors grown in nude mice. Direct injections of HFIF into metastatic melanoma lesions of two patients resulted in either the disappearance of malignant cells or the significant reduction in tumor volume.

Influence of interferon preparations on the proliferative capacity of human and mouse bone marrow cells in vitro

The toxicity of interferon to bone marrow was studied by the use of in vitro colony forming assays for hemopoietic cells. In the same study the relative inhibitory effects of two clinically common interferon preparations, leukocyte and fibroblast interferons, were compared with regard to their effect on both myeloid [colony-forming unit, culture (CFUc)] and erythroid [colony-forming unit, erythroid (CFUe)] progenitor cells. CFUe formation in human bone marrow cells in vitro appeared to be fairly resistant to both interferons. Only high doses of both interferons gave a marked inhibition of CFUe. However, the toxicity of leukocyte and fibroblast interferon was divergent for CFUe in human bone marrow. Leukocyte interferon appeared to be considerably more inhibitory for CFUe than was fibroblast interferon. The effects of mouse interferon, induced in L929 cells, on the growth of CFUc and CFUe in murine bone marrow cells were comparable with those of fibroblast interferon on human cells. The toxicity of human and murine interferon was species specific. Except for the toxicity of leukocyte interferon to CFUc in human bone marrow, the toxicity of interferon was marked only with concentrations on interferon far exceeding the amount necessary to produce an antiviral state in vitro.

Toxicity studies with human leukocyte interferon in newborn rabbits

Daily subcutaneous injections of 5 to 10 million units of partially purified human leukocyte interferon were given to newborn rabbits for 2 weeks or 1 month. The control groups received mock interferon, saline or nothing. The interferon treatment had no overt effect on the development of the animals during the period of treatment. The rabbits treated with interferon had leukocytosis, splenomegaly and prolonged postnatal extramedullary hematopoiesis in the liver and spleen. Certain immune responses were also demonstrated in the rabbits treated with interferon and mock interferon preparations. Platelet counts and the serum-ASAT, -ALAT, -LD and alkaline phosphatase values were normal.