Production of neutralizing granulocyte-macrophage colony-stimulating factor (GM-CSF) antibodies in carcinoma patients following GM-CSF combination therapy

Construction of Recombinant Human GM-CSF and GM-CSF-ApoA-I Fusion Protein and Evaluation of Their Biological Activity

In this study, two strains of the yeast P. pastoris were constructed, one of which produced authentic recombinant human granulocyte-macrophage colony-stimulating factor (ryGM-CSF), and the other was a chimera consisting of ryGM-CSF genetically fused with mature human apolipoprotein A-I (ApoA-I) (ryGM-CSF-ApoA-I). Both forms of the cytokine were secreted into the culture medium. The proteins’ yield during cultivation in flasks was 100 and 60 mg/L for ryGM-CSF and ryGM-CSF-ApoA-I, respectively. Both forms of recombinant GM-CSF stimulated the proliferation of human TF-1 erythroleukemia cells; however, the amount of chimera required was 10-fold that of authentic GM-CSF to induce a similar proliferative effect. RyGM-CSF exhibited a 2-fold proliferative effect on BFU-E (burst-forming units—erythroid) at a concentration 1.7 fold less than non-glycosylated E. coli-derived GM-CSF. The chimera together with authentic ryGM-CSF increased the number of both erythroid precursors and BMC granulocytes after 48 h of incubation of human bone marrow cells (BMCs). In addition, the chimeric form of ryGM-CSF was more effective at increasing the viability of the total amount of BMCs, decreasing apoptosis compared to the authentic form. ryGM-CSF-ApoA-I normalized the proliferation, maturation, and segmentation of neutrophils within the physiological norm, preserving the pool of blast cells under conditions of impaired granulopoiesis. The chimera form of GM-CSF exhibited the properties of a multilinear growth factor, modulating the activity of GM-CSF and, perhaps, it may be more suitable for the normalization of granulopoiesis.

Inhaled GM-CSF for Pulmonary Alveolar Proteinosis

BACKGROUND

Pulmonary alveolar proteinosis is a disease characterized by abnormal accumulation of surfactant in the alveoli. Most cases are autoimmune and are associated with an autoantibody against granulocyte-macrophage colony-stimulating factor (GM-CSF) that prevents clearing of pulmonary surfactant by alveolar macrophages. An open-label, phase 2 study showed some therapeutic efficacy of inhaled recombinant human GM-CSF in patients with severe pulmonary alveolar proteinosis; however, the efficacy in patients with mild-to-moderate disease remains unclear.

METHODS

We conducted a double-blind, placebo-controlled trial of daily inhaled recombinant human GM-CSF (sargramostim), at a dose of 125 μg twice daily for 7 days, every other week for 24 weeks, or placebo in 64 patients with autoimmune pulmonary alveolar proteinosis who had a partial pressure of arterial oxygen (Pao₂) while breathing ambient air of less than 70 mm Hg (or <75 mm Hg in symptomatic patients). Patients with severe pulmonary alveolar proteinosis (Pao₂ <50 mm Hg) were excluded to avoid possible exacerbation of the disease in patients who were assigned to receive placebo. The primary end point was the change in the alveolar-arterial oxygen gradient between baseline and week 25.

RESULTS

The change in the mean (±SD) alveolar-arterial oxygen gradient was significantly better in the GM-CSF group (33 patients) than in the placebo group (30 patients) (mean change from baseline, -4.50±9.03 mm Hg vs. 0.17±10.50 mm Hg; P = 0.02). The change between baseline and week 25 in the density of the lung field on computed tomography was also better in the GM-CSF group (between-group difference, -36.08 Hounsfield units; 95% confidence interval, -61.58 to -6.99, calculated with the use of the Mann-Whitney U test and the Hodges-Lehmann estimate of confidence intervals for pseudo-medians). Serious adverse events developed in 6 patients in the GM-CSF group and in 3 patients in the placebo group.

CONCLUSIONS

In this randomized, controlled trial, inhaled recombinant human GM-CSF was associated with a modest salutary effect on the laboratory outcome of arterial oxygen tension, and no clinical benefits were noted. (Funded by the Japan Agency for Medical Research and Development and the Ministry of Health, Labor, and Welfare of Japan; PAGE ClinicalTrials.gov number, NCT02835742; Japan Medical Association Center for Clinical Trials number, JMA-IIA00205.).

Trial Watch: Immunostimulation with recombinant cytokines for cancer therapy

Cytokines regulate virtually aspects of innate and adaptive immunity, including the initiation, execution and extinction of tumor-targeting immune responses. Over the past three decades, the possibility of using recombinant cytokines as a means to elicit or boost clinically relevant anticancer immune responses has attracted considerable attention. However, only three cytokines have been approved so far by the US Food and Drug Administration and the European Medicines Agency for use in cancer patients, namely, recombinant interleukin (IL)-2 and two variants of recombinant interferon alpha 2 (IFN-α2a and IFN-α2b). Moreover, the use of these cytokines in the clinics is steadily decreasing, mostly as a consequence of: (1) the elevated pleiotropism of IL-2, IFN-α2a and IFN-α2b, resulting in multiple unwarranted effects; and (2) the development of highly effective immunostimulatory therapeutics, such as immune checkpoint blockers. Despite this and other obstacles, research in the field continues as alternative cytokines with restricted effects on specific cell populations are being evaluated. Here, we summarize research preclinical and clinical developments on the use of recombinant cytokines for immunostimulation in cancer patients.

Biological Effects of Anti-Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) Antibody Formation in Patients Treated With GM-CSF (Sargramostim) as Adjuvant Therapy of Melanoma

OBJECTIVES

We investigated the development of binding and neutralizing antibodies to granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients receiving prolonged therapy with GM-CSF as adjuvant therapy of melanoma and the impact of these antibodies on biological effects.

METHODS

Fifty-three patients with high-risk melanoma that had been surgically excised were treated with GM-CSF, 125 μg/m daily for 14 days every 28 days for 1 year after surgical resection of disease. Serum samples for antibodies to GM-CSF were measured before treatment and on study days 155 and 351. Blood draws for testing biological effects were keyed to GM-CSF administration: days 0 (before), 15 (after 14 d on GM-CSF), 29 (after 14 d off GM-CSF), 155, and 351 (after 14 d on GM-CSF in the sixth and 13th cycle of treatment).

RESULTS

Of 53 patients enrolled, 43 were evaluable for the development of anti-GM-CSF antibodies. Of these, 93% developed binding antibodies and 42% developed both binding and neutralizing antibodies. The increase in the white blood cell count, percent eosinophils, or neopterin levels engendered by GM-CSF administration was abrogated or markedly decreased in patients with neutralizing antibodies but not in patients who developed only binding antibodies.

CONCLUSIONS

Ninety-three percent of patients with melanoma treated with GM-CSF as adjuvant therapy develop antibodies to GM-CSF. In those with neutralizing antibodies, a diminution of the biological effects of GM-CSF was observed. The development of neutralizing antibodies might also abrogate the potential clinical benefit of this treatment and should be considered in the design of future clinical trials.

Development of a cell-based qualitative assay for detection of neutralizing anti-human interleukin-1 receptor antagonist (hIL-1Ra) antibodies in rats

To determine the incidence of the positive neutralizing anti-human interleukin receptor antagonist (anti-IL-1Ra), a novel assay based on the proliferation of human melanoma A375.S2 cells was developed and validated. In the presence of a growth-limiting concentration of IL-1β, A375.S2 cells were able to regain proliferation following the addition of IL-1Ra in a concentration-dependent manner. This dose-response effect enabled the validation of a standard curve for calculation of the concentration of IL-1Ra or, inversely, the concentration of neutralizing anti-IL-1Ra antibodies in cell culture medium or sera. The assay used CCK-8 as an indicator of proliferation. The dose-response relationship between rhIL-1Ra (dose range of 5-75 ng/ml rhIL-1Ra) and A375.S2 cell proliferation was sigmoidal and fitted a four-parameter logistic model. The percent coefficients of variation (%CVs) of quality control samples were 12.5 and 11.9% for intra-assay repeatability and 14.5 and 19.5% for inter-assay repeatability, while the total accuracy was in the range of 97.2-103.6%. For the neutralization assay, the optimal sample dilution factor was found to be 40-fold and the reasonable standard for positive and negative decision was calculated to be 59.4% neutralization rate. The %CVs of quality control samples were 12.7 and 24.0% for intra-assay repeatability and 11.6 and 30.0% for inter-assay repeatability. Analysis using the assay showed that rats could produce neutralizing anti-IL-1Ra antibodies after repeated intramuscular injection with rhIL-1Ra, and this response was not significantly dependent on the dose injected.

DNA-protein immunization using Leishmania peroxidoxin-1 induces a strong CD4+ T cell response and partially protects mice from cutaneous leishmaniasis: role of fusion murine granulocyte-macrophage colony-stimulating factor DNA adjuvant

BACKGROUND

To date, no universally effective and safe vaccine has been developed for general human use. Leishmania donovani Peroxidoxin-1 (LdPxn-1) is a member of the antioxidant family of proteins and is predominantly expressed in the amastigote stage of the parasite. The aim of this study was to evaluate the immunogenicity and protective efficacy of LdPxn-1 in BALB/c mice in heterologous DNA-Protein immunization regimen in the presence of fusion murine granulocyte-macrophage colony-stimulating factor (mGMCSF) DNA adjuvant.

METHODOLOGY AND PRINCIPAL FINDINGS

A fusion DNA of LdPxn1 and mGMCSF was cloned into a modified pcDNA vector. To confirm the expression in mammalian system, Chinese hamster ovary cells were transfected with the plasmid vector containing LdPxn1 gene. BALB/c mice were immunized twice with pcDNA-mGMCSF-LdPxn-1 or pcDNA-LdPxn1 DNA and boosted once with recombinant LdPxn-1 protein. Three weeks after the last immunization, mice were infected with Leishmania major promastigotes. The result showed that immunization with pcDNA-mGMCSF-LdPxn1 elicited a mixed Th-1/Th-2 immune response with significantly higher production of IFN-γ than controls. Intracellular cytokine staining of antigen-stimulated spleen cells showed that immunization with this antigen elicited significantly higher proportion of CD4+ T cells that express IFN-γ, TNF-α, or IL-2. The antigen also induced significantly higher proportion of multipotent CD4+ cells that simultaneously express the three Th-1 cytokines. Moreover, a significant reduction in the footpad swelling was seen in mice immunized with pcDNA-mGMCSF-LdPxn1 antigen. Expression study in CHO cells demonstrated that pcDNA-mGMCSF-LdPxn-1 was expressed in mammalian system.

CONCLUSION

The result demonstrates that immunization of BALB/c mice with a plasmid expressing LdPxn1 in the presence of mGMCSF adjuvant elicits a strong specific immune response with high level induction of multipotent CD4+ cells that mediate protection of the mice from Leishmania major infection. To our knowledge, this is the first study showing the vaccine potential of Leishmania peroxidoxin -1.

Comparison of two direct neutralizing assay formats using recombinant follicle-stimulating hormone as agonist

Characterizing anti-drug antibodies for neutralizing activity is commonly part of the immunogenicity testing package for most therapeutic proteins. Cell-based neutralization assays can generally be categorized as direct- or indirect assays depending on whether they are associated with therapeutics with agonistic- or antagonistic properties. This paper's aim is a comparison of the two direct neutralization assay formats; the variable- and fixed concentration assay format, using recombinant follicle-stimulating hormone as drug agonist. Essential validation- and performance parameters, such as sample through-put, cut-point, precision, sensitivity and drug tolerance, were compared. The fixed concentration assay format offers superior sample through-put (40 versus 6 samples), precision (coefficient of variation of ≤14% versus 34%) and almost 6 times better sensitivity and is generally recommended as the better option particularly for quasi-quantitative assessments of neutralizing antibodies.

Strategies and assays for the assessment of unwanted immunogenicity

The assessment of unwanted immunogenicity associated with biological products continues to be a major issue for the biotechnology industry. Monitoring of unwanted immunogenicity during the development of the product from pre-clinical stage through clinical trials is now a regulatory expectation with extended post-marketing commitments required for at least some of these products. Prospective planning of immunogenicity studies incorporating appropriately devised strategies is critical if valid conclusions concerning the immunogenicity profile of a product are to be derived. An important consideration of such studies is the selection of optimized, rigorously validated and standardized methodologies for detection and characterization of antibodies with emphasis on desired assay design, assay controls, and performance criteria. Binding assays with different formats and detection systems, radioimmuno-precipitation assays or surface plasmon resonance procedures are often used as the basis for a screening assay. For assessing the neutralizing capacity of the antibodies, however, a neutralization assay is an absolute requirement. Therefore, a panel of methods is usually necessary for a detailed understanding of the type(s) of antibodies induced against a therapeutic product. This manuscript considers briefly the benefits and limitations of the different techniques available for antibody detection and characterization. A strategy that can be adopted for the assessment of unwanted immunogenicity of therapeutic products is also suggested.

A simple and efficient method for the production of human glycosylated glial cell line-derived neurotrophic factor using a Semliki Forest virus expression system

Human glial cell line-derived neurotrophic factor (hGDNF) is a very promising protein for the treatment of Parkinson's disease and other neurodegenerative disorders. The present work describes a quick and simple method to obtain a high amount of purified hGDNF using a mammalian cell-derived system. The method is based on the high expression level provided by a Semliki Forest virus vector and its ability to induce a strong shut-off of host-cell protein synthesis in mammalian cells. As a result, hGDNF is the only protein present in the supernatant and can be efficiently purified by a single chromatographic step. Using this system it was possible to eliminate other secreted proteins from the culture medium, like insulin-like growth factor-5, which are hard to remove using other hGDNF production methods. Purified hGDNF presents a complex glycosylation pattern typical of mammalian expression systems and is biologically active. This protocol could be extended to other secreted proteins and could be easily scaled up for industrial purposes.

Unwanted immunogenicity: lessons learned and future challenges

All biological therapeutics have the potential to induce an immune response in recipients of these products. Elicitation of an immune response can result in variable clinical impact, ranging from benign to severe adverse effects, a diminution in clinical efficacy or, in some cases, hypersensitivity or allergic reactions. Consequently, assessment of unwanted immunogenicity is an important element of the data required for regulatory submission for product approval. However, issues relating to immunogenicity occur throughout the life-cycle of a biotherapeutic and need to be considered appropriately when introducing any product change(s). Evaluation of immunogenicity of a product requires a well-considered strategy and a panel of appropriately validated (or ‘fit-for-purpose’) assays for antibody detection and characterization in clinical samples. An overview of the bioanalytical methods that are currently being used for assessment of immunogenicity of biotherapeutics and the guidance available along with some of the challenges facing the industry are discussed in this review.

High titer autoantibodies to GM-CSF in patients with AML, CML and MDS are associated with active disease

Antibodies to granulocyte-macrophage colony-stimulating factor (GM-CSF) can be induced when GM-CSF is used as an adjuvant to solid tumor vaccination. Neutralizing anti-GM-CSF IgG has been associated with pulmonary alveolar proteinosis (PAP), and secondary PAP has been linked to myeloid leukemia. We studied 69 patients with acute myeloid leukemia, chronic myeloid leukemia and myelodysplastic syndrome, including 19 patients who received GM-CSF with peptide antigen and incomplete Freund's adjuvant in a vaccine trial for the presence or induction of anti-GM-CSF antibodies. Anti-GM-CSF IgG were present in 36 (52%) patients with myeloid leukemia compared to only 1 of 33 (3%) healthy subjects (P=0.008) and in none of 6 patients with lymphoid leukemia (P=0.0001). Antibody titers were unaffected by vaccination. Anti-GM-CSF IgA and IgM were found in 33 and 20% of patients, respectively; IgA from two patients neutralized GM-CSF. Strikingly, while anti-GM-CSF IgG titers were higher in patients with active disease (n=52) versus those in complete remission (n=14, P=0.0009), GM-CSF expression was not increased in either group. These data are first to show that anti-GM-CSF antibodies of multiple isotypes are present in patients with active myeloid leukemia without PAP and may be useful markers of disease activity.

Multigene/Multisubtype HIV-1 Vaccine Induces Potent Cellular and Humoral Immune Responses by Needle-Free Intradermal Delivery

Gene vaccination encounters problems different from those of gene therapy since both a short half-life of the gene and a strong immune response to the gene product are desirable. We have evaluated a DNA vaccine consisting of seven plasmids encoding nine HIV-1 proteins. Using a needle-free delivery device, the Biojector, together with recombinant mouse GM-CSF, this vaccine induced strong gp160 Env- and p24 Gag-specific cellular and humoral immune responses in mice. The rGM-CSF was crucial for inducing both antibodies and antigen-specific CD8(+) T cell responses against both gp160 and p24. A GMP-produced lot of this vaccine, intended for human use, was delivered intradermally or intramuscularly into BALB/c mice at a GLP-accredited animal facility. This vaccine induced strong cellular responses independent of the route of immunization; moreover, no signs of toxicity were detected after histopathological examination of various tissues. Overall, the results indicate that the intradermal delivery of multigene/multisubtype HIV DNA in combination with recombinant GM-CSF is a safe and efficacious strategy for inducing high levels of specific CD8(+) T cells and unusually high titers of antibodies. This vaccine has been approved by the Swedish Medicinal Products Agency and is currently in a Phase I clinical trial.

Up-Regulation of IL-7, Stromal-Derived Factor-1α, Thymus-Expressed Chemokine, and Secondary Lymphoid Tissue Chemokine Gene Expression in the Stromal Cells in Response to Thymocyte Depletion: Implication for Thymus Reconstitution

Three in vivo adult mouse models were established to study which signals are required to restore the postnatal thymus. Single administration of dexamethasone, estradiol, or exposure to sublethal dose of gamma irradiation served as prototype thymus-ablating therapies. In all models, transient thymic atrophy was manifested due to the loss of the predominant portion of CD4- CD8- double negative and CD4+ CD8+ double positive thymocytes and was followed by a complete regeneration of the thymuses. Acute atrophy/regeneration was observed in the dexamethasone and irradiation models; in the estradiol-treated animals, slow kinetics of atrophy and regeneration was observed. Importantly, in both acute and chronic models, high levels of IL-7 mRNA were detected in the thymuses isolated from mice during maximum atrophy. In addition, chemokine gene array analysis of involuted thymuses revealed high levels of mRNA expression of stromal-derived factor-1alpha (SDF-1alpha), thymus-expressed chemokine (TECK), and secondary lymphoid tissue chemokine (SLC) but not of other chemokines. The levels of IL-7, SDF-1alpha, TECK, and SLC mRNA inversely correlated with the kinetics of regeneration. RT-PCR analysis of stromal cells purified from involuted thymuses confirmed increased IL-7, SDF-1alpha, and SLC gene expression in MHC class II+ CD45- epithelial cells and increased IL-7 and TECK gene expression in class II+ CD45+ CD11c+ dendritic cells. Thus, our data showed for the first time that expression of IL-7, SDF-1alpha, TECK, and SLC mRNA is induced in the thymic stroma during T cell depletion and may play an important role in the reconstitution of the adult thymus.

Kinetics of development and characteristics of antibodies induced in cancer patients against yeast expressed rDNA derived granulocyte macrophage colony stimulating factor (GM-CSF)

We have determined the presence and kinetics of granulocyte macrophage colony stimulating factor (GM-CSF) antibodies induced after repeated administration of a yeast expressed GM-CSF product in prostate cancer patients with minimal recurrent disease using a panel of assays for detection and characterization of antibodies. Results showed that all 15 prostate cancer patients treated with GM-CSF developed GM-CSF reactive antibodies during the course of therapy. Most patients (87%) developed GM-CSF reactive antibodies within 3 months while in other patients (13%), these antibodies were induced after additional cycles of GM-CSF treatment. For most patients, the timing of occurrence of these antibodies was the same regardless of whether the ELISA or surface plasmon resonance (SPR) assays were used for detection. However, in two patients, the recognition of GM-CSF reactive antibodies by SPR assays preceded their detection by ELISA. A significant number of patients (n=9, 60%) developed GM-CSF antibodies which neutralized the biological activity of GM-CSF in vitro in a cell-line based bioassay. These antibodies also recognized GM-CSF protein from different expression systems including the non-glycosylated protein from E. coli indicating that the antibody response is directed towards the amino acid backbone of the protein. A significant effect of GM-CSF antibodies on PSA modulation was not observed in this small cohort of patients despite an alteration in PSA levels in some treated patients. The study design used here did not allow conclusions regarding the relationship between neutralizing antibodies and the PSA levels which were used as a marker for clinical outcome. Implementation of a clinical strategy which permits monitoring for antibody development and for levels of a relevant pre-determined clinical marker at appropriate time-points is necessary for assessing the impact of antibody development on the therapeutic efficacy of the protein.

The detection of anti-erythropoietin antibodies in human serum and plasma

Neutralizing antibodies to erythropoietin (EPO) can cause a loss of response to recombinant human EPO (rHuEPO) and lead to rare cases of sudden, unexplained, severe anemia in chronic renal failure patients treated with rHuEPO. An assay for neutralizing anti-EPO antibodies has been validated that is based on the inhibition of proliferation of human UT-7/EPO cells, an immortalized cell line, by neutralizing antibodies in serum test samples using 3H-thymidine as a marker for proliferation. The dependence of the human cell line on EPO for growth and proliferation in a concentration-dependent manner enabled the validation of a rHuEPO standard curve for cell proliferation that can be used to determine the presence of neutralizing anti-EPO antibodies in serum samples. Proliferation of the cells increases with increasing concentrations of EPO, forming an S-shaped standard curve, which is fit with a 4-parameter logistic model, between 2.5 and 50 mU/mL rHuEPO, with a percent coefficient of variation (% CV) from 8.7% to 22.1% and a % accuracy of 103.5% to 109.5%. Anti-EPO antibodies and serum with anti-EPO antibodies neutralize UT-7/EPO proliferation by 10 mU/mL rHuEPO in a concentration- or dilution-dependent manner with < or = 25% CV. Percent neutralization is calculated by determining the amount of EPO recovered from the original 10 mU/mL added using the formula [((10-concentration recovered)/10)x100%]. Stem cell factor (SCF) stimulated cell proliferation, but not as effectively as rHuEPO. Antibodies to SCF were not able to inhibit the proliferative response induced by EPO and vice versa, confirming the specificity of the assay for antibodies to EPO. High EPO levels can impact both the radioimmunoprecipitation and neutralization assays to produce a false negative result. However, the impact can be mitigated by the large dilutions used in the neutralization assay.

Anti-GM-CSF antibodies in paediatric pulmonary alveolar proteinosis

BACKGROUND

Auto-antibodies against granulocyte-macrophage colony stimulating factor (GM-CSF) may be central to the pathogenesis of adult sporadic pulmonary alveolar proteinosis (PAP). The role of anti-GM-CSF auto-antibodies in paediatric forms of PAP is as yet unclear.

METHODS

Anti-GM-CSF auto-antibodies were determined with the help of an antigen capture assay using serum and/or bronchoalveolar lavage (BAL) fluid from 27 patients with PAP (nine adults, 15 children, three neonates) and from 185 children with different diseases as disease controls (various pulmonary conditions and patients with malignancies).

RESULTS

Anti-GM-CSF auto-antibodies were detected in the serum of five of seven adult PAP patients. They were not found in the serum of any of the children or neonates with PAP nor in any of the disease control patients. Raised anti-GM-CSF titres were found in BAL fluid from three of four adult patients with PAP. Anti-GM-CSF auto-antibodies were detected in BAL fluid of only one of the 15 children (age at diagnosis 11 years, age at BAL 24 years) and in none of the neonates with PAP, nor in any of the disease control patients.

CONCLUSIONS

The presence of anti-GM-CSF auto-antibodies seems to define an autoimmune disease underlying most of the adult sporadic type of PAP, but age at diagnosis may cause an overlap with children in some rare instances. In most of the children and all of the neonates the anti-GM-CSF titres were not significantly increased, indicating that alternative explanations are needed for the pathogenesis of the disease in these patients.

A comparative evaluation of nasal and parenteral vaccine adjuvants to elicit systemic and mucosal HIV-1 peptide-specific humoral immune responses in cynomolgus macaques

Cynomolgus macaques were immunized by either the intramuscular (i.m.) or intranasal (i.n.) route with a HIV-1 peptide-based immunogen (C4-V3 89.6P) alone, or formulated with novel adjuvants to evaluate the ability of the adjuvants to augment peptide-specific systemic and mucosal immune responses. A mutant cholera toxin, CT-E29H, or the combination of recombinant human IL-1alpha (rhIL-1alpha) protein and recombinant human GM-CSF (rhGM-CSF) protein were tested as adjuvants for i.n. immunization, while a stable emulsion of a synthetic monophosphoryl lipid A (MPL) analogue (RC529-SE) plus rhGM-CSF protein was tested as an adjuvant for i.m. immunization. Macaques immunized i.n. with peptide alone failed to elicit an anti-C4-V3 89.6P antibody response in serum. In contrast, all the tested peptide/adjuvant formulations elicited peptide-specific immune responses. RC529-SE/rhGM-CSF elicited the highest peak anti-peptide IgG geometric mean titer in serum (1:32,768 at week 25) followed by rhIL-1alpha/rhGM-CSF (1:1217 at week 10) and CT-E29H (1:256 at week 25). Measurable SHIV neutralizing antibody responses were detectable in only one macaque immunized i.m. with peptide formulated with RC529-SE/rhGM-CSF. Macaques immunized by the i.n. route with peptide in combination with CT-E29H failed to elicit measurable antibody responses at nasal or genital mucosal surfaces. In contrast, antibody responses at the nasal and genital mucosa were detected in macaques immunized by the i.n. route with peptide in combination with rhIL-1alpha/rhGM-CSF. However, antibody responses at the nasal and genital mucosa were highest in macaques immunized parenterally with peptide in combination with the adjuvants RC529-SE/rhGM-CSF. These results suggest that parenteral vaccine administration in combination with the appropriate adjuvant formulation can elicit vaccine-specific humoral immune responses in both systemic and mucosal compartments.

Induction of neutralising antibodies restricts the use of human granulocyte/macrophage colony stimulating factor for vaccine studies in rhesus macaques

Granulocyte/macrophage-colony stimulating factor (GM-CSF) is a valuable adjuvant to enhance induction of cellular immune responses in rodents. Less information is available regarding its use as an adjuvant in primates or humans. We explored recombinant human GM-CSF for potential vaccine studies in rhesus macaques and focused on its effect on peripheral monocytes as progenitors of dendritic cells and its potential immunogenicity. Application of human GM-CSF to nine animals led to an average 32-fold increase in monocyte numbers. This was not observed upon re-treatment, which coincided with GM-CSF-specific neutralising antibodies. These also neutralised the activity of rhesus macaque GM-CSF. The data underscore the need to use species-specific GM-CSF for immunomodulation in primates.

Impact of temperature reduction and expression of yeast pyruvate carboxylase on hGM-CSF-producing CHO cells

Recently, we demonstrated that a recombinant yeast pyruvate carboxylase expressed in the cytoplasm of BHK-21 cells was shown to partially reconstitute the missing link between glycolysis and TCA, increasing the flux of glucose into the TCA and achieving higher yields of recombinant erythropoietin. In the present study, a CHO cell line producing recombinant human granulocyte macrophage colony stimulating factor was used to evaluate the impact of PYC2 expression and reduced culture temperature. Temperature reduction from 37 to 33 degrees C revealed a reduced growth rate, a prolonged stationary phase and a 2.1-fold increase of the cell specific rhGM-CSF production rate for CHO-K1-hGM-CSF cells. The PYC2-expressing cell clones showed a decreased cell growth and a lower maximum cell concentration compared to the control expressing rhGM-CSF but no PYC2. However, only 65% lactate were produced in PYC2-expressing cells and the product yield was 200% higher compared to the control. The results obtained for CHO cells compared to BHK cells reported previously, indicated that the PYC2 expression dominantly reduced the lactate formation and increased the yield of the recombinant protein to be produced. Finally, the growth and productivity of PYC2-expressing CHO-K1-hGM-CSF cells under both temperature conditions were investigated. The average cell specific rhGM-CSF production increased by 3.2-fold under reduced temperature conditions. The results revealed that the expression of PYC2 and a reduced culture temperature have an additive effect on the cell specific productivity of CHO-K1-hGM-CSF cells.

N- and O-linked carbohydrates and glycosylation site occupancy in recombinant human granulocyte-macrophage colony-stimulating factor secreted by a Chinese hamster ovary cell line

GM-CSF is one of several naturally occurring glycoproteins that regulate leukocyte production, migration and function. It has been produced in different cell types, with different properties that depend on the production process used. The purpose of this work was to characterize the recombinant human GM-CSF from an engineered Chinese hamster ovary cell line grown in suspension and as adherent culture for the identification of the glycosylation sites and the definition of the glycosidic moiety, including the degree of site occupancy. Both preparations exhibited size heterogeneity in SDS/PAGE with multiple bands containing glycoprotein forms with either two or one N-glycosylation sites occupied. Minor low molecular mass forms completely lacked N-linked oligosaccharides but contained 1-3 O-linked glycans. Twelve differently charged isoforms were detected in isoelectric focusing gels. At least 16 glycoforms, differing in the number of Hex-HexNAc units (Deltam 365 Da), were detected in MALDI-TOF MS spectra of the desialylated GM-CSFs. MALDI-TOF MS and HPAEC-PAD analysis indicated the presence of predominantly tri- and tetraantennary N-linked oligosaccharide chains with and without N-acetyllactosamine repeat units and some 10% of biantennary oligosaccharides, all containing more than 90% proximal alpha1-6-linked fucose. The oligosaccharide patterns of both GM-CSF preparations were found to be very similar. More than 90% of terminal galactose residues of the N-glycans were found alpha2-3 sialylated with NeuNAc (93%) or NeuNGc (7%). Site specific glycosylation was analysed by electrospray ionization MS and it was found that in the mono glycosylated GM-CSF form more than 90% of the Asn37 were occupied by N-glycans. O-glycosylation at the N-terminus of the polypeptide was detected at Ser7 and Ser9 or Thr10, in the predominantly doubly O-glycosylated glycoprotein form. In the triply modified GM-CSF molecules, Ser5 was additionally O-glycosylated. The major difference between both preparations was found in the MALDI spectra of the desialylated glycoproteins, revealing a higher proportion of forms with a single N-glycosylation site occupied in the preparation derived from suspension culture. ESI-MS and MALDI-MS analysis of endoproteolytically cleaved peptides as well as MALDI-TOF MS of the intact glycoprotein demonstrated the N- and C-termini integrity of the GM-CSF preparations.

Strategies for detection, measurement and characterization of unwanted antibodies induced by therapeutic biologicals

An important aspect of evaluating the safety of therapeutic biologicals is the assessment of the unwanted immunogenicity of such biologicals in recipients. Properly planned immunogenicity studies with appropriately devised strategies are critical if valid conclusions concerning the unwanted immunogenicity are to be derived. Such studies need to be conducted using carefully selected and validated procedures. Several techniques are available for detection and measurement of immunogenicity including immunoassays, radioimmunoprecipitation assays (RIPAs), surface plasmon resonance (SPR) and bioassays. A combination of methods for characterization of the induced antibodies is usually necessary for a detailed understanding of the type(s) of antibodies generated against a therapeutic product. This review considers the benefits and limitations of the various techniques available for antibody detection and outlines a strategy for the assessment of unwanted immunogenicity of therapeutic products.

Anti-cytokine autoantibodies in autoimmunity: preponderance of neutralizing autoantibodies against interferon-alpha, interferon-omega and interleukin-12 in patients with thymoma and/or myasthenia gravis

We have screened for spontaneous anticytokine autoantibodies in patients with infections, neoplasms and autoimmune diseases, because of their increasingly reported co-occurrence. We tested for both binding and neutralizing autoantibodies to a range of human cytokines, including interleukin-1alpha (IL-1alpha), IL-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-18, interferon-alpha2 (IFN-alpha2), IFN-omega, IFN-beta, IFN-gamma, tumour necrosis factor alpha (TNF-alpha), transforming growth factor beta-1 (TGF-beta1) and granulocyte-macrophage colony stimulating factor (GM-CSF), in plasmas or sera. With two notable exceptions described below, we found only occasional, mostly low-titre, non-neutralizing antibodies, mainly to GM-CSF; also to IL-10 in pemphigoid. Strikingly, however, high-titre, mainly IgG, autoantibodies to IFN-alpha2, IFN-omega and IL-12 were common at diagnosis in patients with late-onset myasthenia gravis (LOMG+), thymoma (T) but no MG (TMG-) and especially with both thymoma and MG together (TMG+). The antibodies recognized other closely related type I IFN-alpha subtypes, but rarely the distantly related type I IFN-beta, and never (detectably) the unrelated type II IFN-gamma. Antibodies to IL-12 showed a similar distribution to those against IFN-alpha2, although prevalences were slightly lower; correlations between individual titres against each were so modest that they appear to be entirely different specificities. Neither showed any obvious correlations with clinical parameters including thymoma histology and HLA type, but they did increase sharply if the tumours recurred. These antibodies neutralized their respective cytokine in bioassays in vitro; although they persisted for years severe infections were surprisingly uncommon, despite the immunosuppressive therapy also used in most cases. These findings must hold valuable clues to autoimmunizing mechanisms in paraneoplastic autoimmunity.

Pulmonary alveolar proteinosis: progress in the first 44 years

Pulmonary alveolar proteinosis is a rare clinical syndrome that was first described in 1958. Subsequently, over 240 case reports and small series have described at least 410 cases in the literature. Characterized by the alveolar accumulation of surfactant components with minimal interstitial inflammation or fibrosis, pulmonary alveolar proteinosis has a variable clinical course ranging from spontaneous resolution to death with pneumonia or respiratory failure. The most effective proven treatment--whole lung lavage--was described soon after the first recognition of this disease. In the last 8 years, there has been rapid progress toward elucidation of the molecular mechanisms underlying both the congenital and acquired forms of pulmonary alveolar proteinosis, following serendipitous discoveries in gene-targeted mice lacking granulocyte-macrophage colony-stimulating factor (GM-CSF). Impairment of surfactant clearance by alveolar macrophages as a result of inhibition of the action of GM-CSF by blocking autoantibodies may underlie many acquired cases, whereas congenital disease is most commonly attributable to mutations in surfactant protein genes but may also be caused by GM-CSF receptor defects. Therapy with GM-CSF has shown promise in approximately half of those acquired cases treated, but it is unsuccessful in congenital forms of the disease, consistent with the known differences in disease pathogenesis.

Incidence of GM-CSF antibodies in cancer patients receiving GM-CSF for immunostimulation

We have assessed the immunogenicity profile of GM-CSF in patients with either colorectal carcinoma (CRC) at different stages of disease or with multiple myeloma who were given recombinant human GM-CSF (Escherichia coli-derived) combination therapy. Metastatic CRC patients received a colon carcinoma-reactive antibody and high doses of GM-CSF (425--500 microg/day for 10 days), while other CRC patients and those with myeloma received low doses of GM-CSF (75--80 microg/day for 4 days) as an adjuvant along with appropriate tumor antigens. We found that 55% of the patients (11/20) given high doses of GM-CSF developed GM-CSF-reactive antibodies in comparison with an incidence of only 16% (4/25) in patients given low doses of GM-CSF. None of the patients developed neutralizing antibodies and so the biological effects of GM-CSF were not compromised. A majority of patients (80%) (36/45) also developed antibodies to E. coli proteins that were present as trace contaminants in the GM-CSF product. Treatment with recombinant GM-CSF products, therefore, may induce antibodies against this cytokine depending on the regimen and the amounts used. In this study, multiple immunizations with low doses of GM-CSF was associated with a low incidence of GM-CSF antibodies, which did not neutralize the effect of the cytokine. This therapeutic strategy was effective in inducing adjuvant-type effects and needs to be explored in further clinical trials with this cytokine.

Human immune response to recombinant human proteins

Delivery of pharmacological doses of proteins to people has raised concerns of inducing immune responses, especially when the protein is provided in multiple doses over an extended period of time. Immune responses could impact the therapeutic exposure and efficacy of the protein itself. In addition, there have been fears of anaphylaxis or autoimmunity. This review summarizes the available literature regarding the measurement and evaluation of immune responses observed during clinical assessment of recombinant human proteins. Immune responses have ranged from none at all to inactivation and/or accelerated clearance. Presence of antibodies does not necessarily impact therapeutic viability. While responses are related to frequency and route of delivery, there is no clear relationship that enables one to predict the clinical experience.

Serological diagnosis of idiopathic pulmonary alveolar proteinosis

Previously, we reported the specific occurrence of neutralizing autoantibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF) in the bronchoalveolar lavage fluid from 11 Japanese patients with idiopathic pulmonary alveolar proteinosis (I-PAP). The autoantibody was also detected in sera from all 5 I-PAP patients examined. To determine that the existence of the autoantibody is not limited to the Japanese patients, we examined sera from 24 I-PAP patients in five countries and showed that the autoantibody was consistently and specifically present in such patients. Thus, detection of the autoantibody in sera can be used for diagnosis of I-PAP. To establish a simple and convenient method for diagnosis of I-PAP, we developed a novel latex agglutination test using latex beads coupled with recombinant human GM-CSF. GM-CSF binding proteins isolated from the sera using the latex beads were identified as the autoantibodies of IgG(1) and IgG(2). The titer of the autoantibody determined by this test correlated with that determined by ELISA. Agglutination was positive in 300-fold diluted sera from all 24 I-PAP patients, but negative in sera from four secondary PAP patients, two congenital PAP patients, 40 patients with other lung diseases, and 38 of 40 normal subjects. These results establish that the latex agglutination test is a reliable method for serological diagnosis of I-PAP with high sensitivity (100%) and specificity (98%).

Neutralizing antibodies to granulocyte-macrophage colony-stimulating factor, interleukin-1alpha and interferon-alpha but not other cytokines in human immunoglobulin preparations

Human immunoglobulin preparations are used therapeutically for various disorders. Such therapy is generally safe but adverse effects occasionally occur in recipients. It has been suggested that antibodies to cytokines present in clinical immunoglobulin products may contribute to undesirable effects in recipients. Therefore, we investigated intravenous and intramuscular immunoglobulin products for the presence of cytokine-specific neutralizing antibodies. Using validated bioassays, we detected neutralizing activity against human granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-alpha2a (IFN-alpha2a) and interleukin-1alpha (IL-1alpha) in immunoglobulin products. We found no neutralization of granulocyte colony-stimulating factor, macrophage colony-stimulating factor, stem cell factor, IL-1beta, IL-2, IL-3, IL-4, IL-6, IL-9, IL-10, IL-12, tumour necrosis factor-alpha, oncostatin M (OSM) and IFN-gamma. Most batches which neutralized IFN-alpha2a activity also neutralized other IFN-alpha subtypes, IFN-omega and IFN-beta. Most products (94%) neutralized the biological activity of GM-CSF. No correlation between batches and their ability to neutralize bioactivities of GM-CSF, IFN-alpha2a and IL-1alpha was found. This neutralizing activity could be traced to plasma pools used for manufacture of immunoglobulins. The neutralization was mediated by specific cytokine antibodies contained within immunoglobulin products as it was present in specific immunoglobulin G (IgG) fractions eluted from cytokine affinity chromatography columns. Specific binding of such IgG fractions to cytokines in immunoblots and in enzyme-linked immunosorbent assays (ELISAs) was observed. This contrasts with the broad non-specific recognition of cytokine proteins observed using unfractionated immunoglobulins in ELISAs. This is the first comprehensive study showing the presence of neutralizing antibodies against GM-CSF, IL-1alpha, or IFN-alpha2a in immunoglobulin products.

Spontaneously occurring neutralizing antibodies against granulocyte-macrophage colony-stimulating factor in patients with autoimmune disease

There is increasing evidence that spontaneous anticytokine autoantibodies are associated with chronic infections and autoimmune diseases. We report the sporadic occurrence in autoimmune diseases of such autoantibodies to granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine involved in inflammation and the regulation of proliferation, differentiation and function of granulocytic and monocytic cell lineages. In 41 of 425 patients tested, we found low to moderate levels of autoantibodies binding to GM-CSF in serum or plasma. These were most prevalent in patients with myasthenia gravis (MG). However, neutralizing autoantibodies against GM-CSF were very rare, being found in only three patients. Two had autoimmune MG, one with thymoma (Patient A) and the other (Patient B) with 'seronegative' MG, i.e. without the antiacetylcholine receptor autoantibodies characteristic of most MG patients, and a third (Patient D) had multiple sclerosis. Only very limited amounts of Patient A and Patient D serum/plasma were available for analysis and therefore further studies were carried out on the more plentiful samples from Patient B. The anti-GM-CSF autoantibodies of Patient B were predominantly polyclonal immunoglobulin G and strongly neutralized recombinant human (rh) GM-CSF derived from different expression systems. They had similar immunological and immunochemical characteristics to anti-GM-CSF antibodies that developed in immunocompetent colorectal carcinoma patients following (rh)GM-CSF therapy. In serial samples from Patient B, the anti-GM-CSF autoantibodies were undetectable from diagnosis at age 8 years until at least age 13, but then developed spontaneously during (temporary) withdrawal of immunosuppressive treatment. Their neutralizing activity has persisted since their first detection at age 15 years 1 month, and was at its highest level recently at age 17 years 7 months. There was no obvious association with other autoimmune phenomena, nor were any haematological deficiencies overtly manifested, suggesting that any loss of GM-CSF function may have been compensated for by other cytokines.

Augmentation of the immune response with granulocyte-macrophage colony-stimulating factor and other hematopoietic growth factors

Granulocyte-macrophage colony-stimulating factor is by far the most widely used hematopoietic growth factor to augment immune responses. At present, the best secured effect is as an adjuvant cytokine for vaccination. Granulocyte-macrophage colony-stimulating factor can be delivered as gene-transduced tumor cells, as plasmid DNA, or as the soluble free granulocyte-macrophage colony-stimulating factor protein. Granulocyte-macrophage colony-stimulating factor must be present at the same site as the vaccine component. Granulocyte-macrophage colony-stimulating factor may also augment the effect of therapeutic monoclonal antibodies by enhancing various effector functions such as antibody-dependent cellular cytotoxicity and amplifying an idiotypic network response (i.e., antitumor immunity). It may also be advantageous to combine granulocyte colony-stimulating factor with monoclonal antibodies (neutrophil and monocyte antibody-dependent cellular cytotoxicity) for tumor therapy. However, these growth factors might also induce immune suppression, which may hamper the contemplated effect of the growth factor. It is urgently warranted to better understand these dual effects on the immune system so that we can find optimal uses for the growth factors in various clinical settings.

Immunization With Recombinant Human Granulocyte-Macrophage Colony-Stimulating Factor as a Vaccine Adjuvant Elicits Both a Cellular and Humoral Response to Recombinant Human Granulocyte-Macrophage Colony-Stimulating Factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is an important cytokine for the generation and propagation of antigen-presenting cells and for priming a cellular immune response. We report here that use of recombinant human GM-CSF (rhGM-CSF), administered as an adjuvant in a peptide-based vaccine trial given monthly by intradermal injection, led to the development of a T-cell and antibody response to rhGM-CSF. An antibody response occurred in the majority of patients (72%). This antibody response was not found to be neutralizing. In addition, by 48-hour delayed type hypersensitivity (DTH) skin testing, 17% of patients were shown to have a cellular immune response to the adjuvant rhGM-CSF alone. Thymidine incorporation assays also showed a peripheral blood T-cell response to rhGM-CSF in at least 17% of the patients. The generation of rhGM-CSF–specific T-cell immune responses, elicited in this fashion, is an important observation because rhGM-CSF is being used as a vaccine adjuvant in various vaccine strategies. rhGM-CSF–specific immune responses may be incorrectly interpreted as antigen-specific immunity, particularly when local DTH responses to vaccination are the primary means of immunologic evaluation. We found no evidence of hematologic or infectious complications as a result of the development of rhGM-CSF–specific immune responses.

Immunization With Recombinant Human Granulocyte-Macrophage Colony-Stimulating Factor as a Vaccine Adjuvant Elicits Both a Cellular and Humoral Response to Recombinant Human Granulocyte-Macrophage Colony-Stimulating Factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is an important cytokine for the generation and propagation of antigen-presenting cells and for priming a cellular immune response. We report here that use of recombinant human GM-CSF (rhGM-CSF), administered as an adjuvant in a peptide-based vaccine trial given monthly by intradermal injection, led to the development of a T-cell and antibody response to rhGM-CSF. An antibody response occurred in the majority of patients (72%). This antibody response was not found to be neutralizing. In addition, by 48-hour delayed type hypersensitivity (DTH) skin testing, 17% of patients were shown to have a cellular immune response to the adjuvant rhGM-CSF alone. Thymidine incorporation assays also showed a peripheral blood T-cell response to rhGM-CSF in at least 17% of the patients. The generation of rhGM-CSF–specific T-cell immune responses, elicited in this fashion, is an important observation because rhGM-CSF is being used as a vaccine adjuvant in various vaccine strategies. rhGM-CSF–specific immune responses may be incorrectly interpreted as antigen-specific immunity, particularly when local DTH responses to vaccination are the primary means of immunologic evaluation. We found no evidence of hematologic or infectious complications as a result of the development of rhGM-CSF–specific immune responses.

Antibody to Granulocyte-Macrophage Colony-Stimulating Factor Is a Dominant Anti-Cytokine Activity in Human IgG Preparations

Pharmaceutical preparations of normal human immunoglobulin (IgG) are known to contain high-avidity and neutralizing antibodies (Ab) to the cytokines interleukin (IL)-1α, IL-6, and interferon (IFN)α. To test for other cytokine Ab, 23 batches of IgG were tested for saturable binding to eight 125I-labeled recombinant cytokines. All batches bound granulocyte-macrophage colony-stimulating factor (GM-CSF) with high avidity (Kav ≈ 10 pmol/L) and capacities of up to 5 μmol GM-CSF/mol IgG. Only 1 of 15 batches bound IL-5, also with high avidity, whereas 13 of 15 batches bound to IL-10 but with lower capacities and avidities. None of the IgG preparations bound IL-1 receptor antagonist (IL-1ra), IL-2, IL-3, IL-4, or G-CSF. Cross-binding and absorption analyses revealed identical or slightly stronger binding of recombinant GM-CSF, IL-5, and IL-10 than their native counterparts. GM-CSF–IgG complexes did not bind to cellular GM-CSF receptors, but Fc-dependent binding occurred to blood polymorphonuclear cells. Increased binding of GM-CSF to patient sera correlated positively with the binding capacities of infused IgG preparations. Patient and normal sera did not interfere with the binding of Ab to GM-CSF. From these and previous experiments, we conclude that pools of normal human IgG contain variable amounts of specific and high-avidity Ab to some cytokines, and that Ab to GM-CSF constitute a dominant anti-cytokine activity in these preparations. These Ab are available for reactionin vivo following IgG therapy.

Antibody to Granulocyte-Macrophage Colony-Stimulating Factor Is a Dominant Anti-Cytokine Activity in Human IgG Preparations

Pharmaceutical preparations of normal human immunoglobulin (IgG) are known to contain high-avidity and neutralizing antibodies (Ab) to the cytokines interleukin (IL)-1α, IL-6, and interferon (IFN)α. To test for other cytokine Ab, 23 batches of IgG were tested for saturable binding to eight 125I-labeled recombinant cytokines. All batches bound granulocyte-macrophage colony-stimulating factor (GM-CSF) with high avidity (Kav ≈ 10 pmol/L) and capacities of up to 5 μmol GM-CSF/mol IgG. Only 1 of 15 batches bound IL-5, also with high avidity, whereas 13 of 15 batches bound to IL-10 but with lower capacities and avidities. None of the IgG preparations bound IL-1 receptor antagonist (IL-1ra), IL-2, IL-3, IL-4, or G-CSF. Cross-binding and absorption analyses revealed identical or slightly stronger binding of recombinant GM-CSF, IL-5, and IL-10 than their native counterparts. GM-CSF–IgG complexes did not bind to cellular GM-CSF receptors, but Fc-dependent binding occurred to blood polymorphonuclear cells. Increased binding of GM-CSF to patient sera correlated positively with the binding capacities of infused IgG preparations. Patient and normal sera did not interfere with the binding of Ab to GM-CSF. From these and previous experiments, we conclude that pools of normal human IgG contain variable amounts of specific and high-avidity Ab to some cytokines, and that Ab to GM-CSF constitute a dominant anti-cytokine activity in these preparations. These Ab are available for reactionin vivo following IgG therapy.

Neutralising antibodies to granulocyte-macrophage colony stimulating factor (GM-CSF) in carcinoma patients following GM-CSF combination therapy

There is a high risk of developing neutralizing and non-neutralizing antibodies when GM-CSF is used as an immunomodulatory agent in non-immune compromised patients and not in combination with chemotherapy. The presence of neutralizing antibodies may seriously hamper the clinical response of the patients this must be taken into account when designing protocols if the biological activity of the exogenously administered GM-CSF is not to be impaired and the endogenous production of GM-CSF is not to be inactivated. Assessment of production of neutralising antibodies during cytokine therapy is important for predicting the clinical response to progressive therapy.