Immunomodulation of Acellular Dermal Matrix Through Interleukin 4 Enhances Vascular Infiltration.

BACKGROUND: Acellular dermal matrix (ADM) supported implant-based reconstruction remains the most commonly performed mode of reconstruction after breast cancer. Acellular dermal matrix clinical usage has reported benefits but requires rapid and efficient vascular and cellular incorporation into the recipient to have the best outcomes. Orderly transition from M1 to M2 macrophage phenotypic profile, coordinated in part by interleukin 4 (IL-4), is an important component of vascular stabilization and remodeling. Using the ADM substrate as a delivery device for immunomodulation of macrophage phenotype holds the potential to improve integration. METHODS: Interleukin 4 was adsorbed onto ADM samples and drug elution curves were measured. Next, experimental groups of 8 C57BL/6 mice had 5-mm ADM discs surgically placed in a dorsal window chamber with a vascularized skin flap on one side and a plastic cover slip on the other in a model of implant-based breast reconstruction. Group 1 consisted of IL-4 (5 µg) adsorbed into the ADM preoperatively and group 2 consisted of an untreated ADM control. Serial gross examinations were performed with histology at day 21 for markers of vascularization, mesenchymal cell infiltration, and macrophage lineage. RESULTS: Drug elution curves showed sustained IL-4 release for 10 days after adsorption. Serial gross examination showed similar rates of superficial vascular investment of the ADM beginning at the periphery by day 14 and increasing through day 21. Interleukin-4 treatment led to significantly increased CD31 staining of vascular endothelial cells within the ADM over the control group (P < 0.05) at 21 days. Although vimentin staining did not indicate a significant increase in fibroblasts overall, IL-4 did result in a significant increase in expression of α-smooth muscle actin. The expression of macrophage phenotype markers Arginase1 and iNOS present within the ADM were not significantly affected by IL-4 treatment at the day 21 time point. CONCLUSIONS: Acellular dermal matrix has the potential to be used for immunomodulatory cytokine delivery during the timeframe of healing. Using implanted ADM as a delivery vehicle to drive IL-4 mediated angiogenesis and vascular remodeling significantly enhanced vascularity within the ADM substrate.

IL-4 induces the formation of multinucleated giant cells and expression of Beta5 integrin in central giant cell lesion

BACKGROUND: It is now well established that IL-4 has a central role in the development of monocytes to multinucleated giant cells (MGCs) by inducing the expression of integrins on the surface of monocytes. The aim of this study was to investigate the potential role of IL-4 in induction of β5 integrin expression in the peripheral blood samples of patients with giant cell granuloma. MATERIAL AND METHODS: Monocytes were isolated from peripheral blood samples of patients with central giant cell granuloma (CGCG) and healthy controls using human Monocyte Isolation Kit II. Isolated monocytes were then cultured in the absence or presence of IL-4 (10 and 20 ng/mL), and following RNA extraction and cDNA synthesis, Real-time PCR was performed to determine the level of β5 integrin expression. The formation of CGCGs and morphological analyses were done under light microscopy. For confirmation of CGCGs, immunocytochemistry technique was also carried out by anti-RANK (receptor-activator of NF-κB ligand) antibody. RESULTS: In both patient and control groups, β5 levels were significantly enhanced by increasing the IL-4 dose from 10 to 20 ng/mL. In addition, these differences were significant between patient and control groups without IL-4 treatment. On the other hand, the number of cells which expressed RANK and therefore the number of giant cells were significantly higher in the patient group in comparison to controls, as assessed by immunohistochemistry evaluations. CONCLUSIONS: In this study, we showed an elevation in the expression levels of β5 integrin when stimulated by IL-4. It is strongly indicated that this integrin acts as an important mediator during macrophage to macrophage fusion and development of giant cells

IL-4 Release from a Biomimetic Scaffold for the Temporally Controlled Modulation of Macrophage Response.

The interaction of immune cells with biomaterials has been identified as a possible predictor of either the success or the failure of the implant. Among immune cells, macrophages have been found to contribute to both of these possible scenarios, based on their polarization profile. This proof-of-concept study aimed to investigate if it was possible to affect the response of macrophages to biomaterials, by the release of anti-inflammatory mediators. Towards this end, a collagen scaffold, integrated with poly(lactic-co-glycolic acid)-multistage silicon particles (MSV) composite microspheres (PLGA-MSV) releasing IL-4 was developed (PLGA-MSV/IL-4). Macrophages' response to the scaffold was evaluated, both in vitro with rat bone-marrow derived macrophages, and in vivo in a rat subcutaneous pouch model. In vitro experiments revealed an overexpression of anti-inflammatory associated genes (Il-10, Mrc1, Arg1) at as soon as 48 h. The analysis of the cells that infiltrated the scaffold, revealed a prevalence of CD206(+) macrophages at 24 h. Our strategy demonstrated that it is possible to tune the in vivo early response to biomaterials by the release of an anti-inflammatory cytokine, and that could contribute to accelerate the resolution of the inflammatory phase, benefiting a vast range of tissue engineering applications.

T-cell proliferation by surface molecules expression on polymorphonuclear neutrophils stimulated with IL-4 in superantigen presence

Background: Polymorphonuclear neutrophils (PMNs) were originally described as short lived and terminally differentiated phagocytes that contribute only to the innate immune response. Some studies of PMNs cytokine production and expression of numerous cell surface proteins has suggested that PMNs are likely to influence adaptive responses and may satisfy the criteria of antigen presenting cells.Aim of the study This work aimed to study the effect of IL-4 in the function of PMNs as antigen presenting cells. Methods: Flow cytometry was used in the present study for the detection of cell surface human leukocyte antigen (HLA) class II, CD80 and CD86 required for antigen presentation and subsequent T-cell activation in the presence of Staphylococcus aureus enterotoxin (A). Human peripheral blood neutrophils were used for this purpose. Results: This study has shown that IL-4 stimulated PMNs for 24h expressed HLA class II, CD80 and CD86 that involved in antigen presentation. It also indicated that co-cultivation of IL-4 stimulated PMNs with autologous T-cells and in the presence of S. aureus enterotoxin (A) induced T-cell proliferation. Conclusions: In vitro stimulation of PMNs with IL-4 showed expression of surface molecules involved in antigen presentation. In addition, the co-culture of T-Cells and stimulated PMNs showed high T-Cells proliferation in the presence of superantigens(AU)

Pitrakinra for asthma.

IMPORTANCE OF THE FIELD: In asthma IL-4 and IL-13 have been demonstrated to play major pathogenic roles and therefore their blockade would potentially represent a plausible therapeutic approach. AREAS COVERED IN THIS REVIEW: Pitrakinra is a dual IL-4/IL-13 inhibitor currently under development for asthma and the existing preclinical and clinical data are discussed. WHAT THE READER WILL GAIN: Inhaled pitrakinra demonstrated a good anti-inflammatory potential and a good safety profile on a short-term basis but its place in asthma therapy is still to be found. TAKE HOME MESSAGE: Specific anticytokine therapies might in the near future reshape asthma therapy.

Inhaled vs subcutaneous effects of a dual IL-4/IL-13 antagonist in a monkey model of asthma.

BACKGROUND: Pitrakinra is a recombinant protein derived from human interleukin-4 (IL-4) that binds to IL-4Ralpha and acts as a competitive antagonist of IL-4 and IL-13. The studies reported here compare the dose-ranging effects of pitrakinra on allergen-induced airway hyperresponsiveness (AHR) and airway eosinophilia when administered subcutaneously (s.c.) or by inhalation to the Ascaris suum-sensitive cynomolgus monkey for the purpose of elucidating the primary site of pitrakinra's anti-asthmatic action. METHODS: Airway responsiveness to inhaled methacholine and bronchoalveolar lavage cell composition was determined before and after three allergen exposures with a 1-week course of twice-daily (b.i.d.) s.c. or inhaled pitrakinra or placebo treatment. RESULTS: Treatment with s.c. pitrakinra significantly reduced allergen-induced AHR, with a maximum effect of a 2.8- to 3.8-fold increase in methacholine PC(100) relative to control (P < 0.05) observed at b.i.d. s.c. doses of 0.05-0.5 mg/kg. Inhaled pitrakinra also significantly reduced AHR with a similar maximum effect of a 2.8- to 3.2-fold increase in methacholine PC(100) relative to control (P < 0.05) at nominal b.i.d. doses of 3-100 mg. The maximal effect on AHR following inhalation was observed at a plasma concentration which exhibited no efficacy via the subcutaneous route. The effect of pitrakinra on lung eosinophilia was not statistically significant following either route of administration, although lung eosinophil count was reduced in all studies relative to control. CONCLUSION: Local administration of pitrakinra to the lung is sufficient to inhibit AHR, one of the cardinal features of asthma, indicating the therapeutic potential of inhaled pitrakinra in the treatment of atopic asthma.

Recombinant murine interleukin 4 protein therapy for psoriasis in a transgenic VEGF mouse model.

BACKGROUND: Psoriasis is a typical autoimmune disease caused by a deregulation of the Th1/Th2 balance, and immunotherapy for psoriasis has been shown to be clinically efficacious. Vascular endothelial growth factor (VEGF) is a potent mediator of angiogenesis. Evidence suggests that the chronic delivery of VEGF to the skin can result in a profound inflammatory condition with many of the cellular and molecular hallmarks of human psoriasis. In this study, we investigated whether the transgenic VEGF mouse is a suitable model for antipsoriatic studies. AIM: To determine the effect of a recombinant murine interleukin 4 (rmIL-4) in the transgenic VEGF mouse model. METHODS: Fifteen homozygous K14-VEGF transgenic mice were injected subcutaneously with rmIL-4 protein for 30 consecutive days with a prospective dose escalation of 0.5, 2 or 5 microg/kg. Hematoxylin-eosin staining, immunohistochemistry and real-time polymerase chain reaction analyses were performed with ear samples. RESULTS: The rmIL-4 protein therapy was well tolerated. Tissue sections from treated skin showed improvements upon morphological and histological examinations: diminution of erythematous appearance and regression of epidermal thickness were observed, and T lymphocyte infiltration decreased significantly. The expressions of adhesion molecules, such as vascular cell adhesion molecule 1 and intracellular adhesion molecule 1, were found reduced. The level of IL-4 mRNA also increased while the level of gamma-interferon mRNA decreased, resulting in a 10-fold increase in the ratio of Th1/Th2. CONCLUSIONS: Our results reveal that rmIL-4 has clinical efficacy for the treatment of K14-VEGF transgenic mice. Angiogenesis and inflammation were ameliorated by therapy with rmIL-4.

Convection-enhanced and local delivery of targeted cytotoxins in the treatment of malignant gliomas.

Despite advances in our knowledge about the genesis, molecular biology, and natural history of malignant gliomas and the use of a multi-disciplinary approach to their treatment, patients harboring this diagnosis continue to face a grim prognosis. At the time of diagnosis, patients typically undergo surgery for the establishment of a histologic diagnosis, the reduction of tumor burden, and the relief of mass effect, with the maintenance of the patient's neurological function in mind. This is followed by the administration of adjuvant therapeutics, including radiation therapy and chemotherapy. Many investigational agents with laboratory evidence of efficacy against malignant gliomas have not met their promise in the clinical setting, largely due to the barriers that they must overcome to reach the tumor at a therapeutically meaningful concentration for a durable period of time. The relevant aspects of the blood-brain barrier, blood-tumor barrier, and blood-cerebrospinal fluid barrier, as they pertain to the delivery of agents to the tumor, will be discussed along with the strategies devised to circumvent them. This discussion will be followed by a description of agents currently in preclinical and clinical development, many of which are the result of intense ongoing research into the molecular biology of gliomas.

Factors regulating the effect of IL-4 on intestinal epithelial barrier function.

BACKGROUND: Inflammatory bowel disease is associated with an imbalance in cytokine production and defective intestinal barrier function. Previous studies indicate that IL-4, a cytokine increased in food allergy and in early Crohn's disease, enhances epithelial permeability. Here, we characterized the mechanism of action of IL-4 on cultured epithelial cells and examined if the anti-inflammatory cytokines, TGF-beta or IL-10, can modulate the effects of IL-4. METHODS: Confluent monolayers of human T84 epithelial cells were cultured with IL-4 alone or in combination with IL-10 or TGF-beta or with inhibitors of protein synthesis and blockers of IL-4 receptor signalling pathways. Permeability was evaluated by measuring transepithelial resistance (TER), flux of (3)H-fMLP (a small bacterial tripeptide) and horseradish peroxidase (HRP) (a macromolecule). RESULTS: T84 cells cultured with IL-4 showed a significant drop in TER as well as an increased flux of (3)H-fMLP and HRP. Co-treatment with IL-10 did not improve TER, whereas TGF-beta attenuated the resistance drop. However, neither TGF-beta nor IL-10 were able to correct the increased (3)H-fMLP flux. In contrast, the increased HRP flux caused by IL-4 was inhibited by both IL-10 and TGF-beta. TGF-beta and IL-10 significantly reduced IL-4-enhanced values for endosomal area and paracellular spaces containing HRP. Inhibitor studies indicated the requirement for protein synthesis and the involvement of phosphatidylinositol 3-kinase. CONCLUSIONS: These results provide new insights into the regulation of intestinal barrier function and may suggest a novel approach in the treatment of intestinal inflammation.

A phase I and pharmacokinetic study of subcutaneously-administered recombinant human interleukin-4 (rhuIL-4) in patients with advanced cancer.

PURPOSE: To investigate the pharmacokinetics and tolerability of recombinant human interleukin-4 (rhuIL-4), administered by daily subcutaneous injection, in patients with advanced cancer. PATIENTS AND METHODS: Fourteen patients with advanced cancer treated with rhuIL-4 at escalating dose levels of 0.25, 1.0 and 5.0 microg/kg/day, on days 1, 8-17, and 28-57. The primary endpoints of the study were toxicity of rhuIL-4 and the determination of the pharmacokinetics of rhuIL-4 when given by subcutaneous injection. Secondary endpoints included effects on blood counts, hematopoietic cell precursors, and various immunologic parameters. RESULTS: rhuIL-4 was well tolerated at all three dose levels. Detectable serum levels of IL-4 were found in patients at the 1.0 and 5.0 microg/kg/day dose levels. Peak serum IL-4 levels were achieved about 2 h after injection and IL-4 was still detectable 8 h after injection. No grade 4 toxicities were observed and grade 3 toxicities were confined to fever, headache and raised hepatic alkaline phosphatase. No consistent hematological or immunologic effects were observed. Although therapeutic efficacy was not an endpoint, one complete response (Hodgkin's disease) was observed. One patient with chronic lymphocytic leukemia progressed on therapy. CONCLUSION: rhuIL-4 up to 5.0 microg/kg/day is well tolerated when given by subcutaneous injection. Biologically relevant serum IL-4 levels can be achieved and sustained for at least 8 h after a single injection.

Dendritic cell-derived nitric oxide is involved in IL-4-induced suppression of experimental allergic encephalomyelitis (EAE) in Lewis rats.

Cytokines play a crucial role in initiating and perpetuating EAE, an animal model of multiple sclerosis (MS). A low dose of IL-4, administered by the nasal route over 5 days (100 ng/rat per day) prior to immunization, improved clinical scores of EAE induced in Lewis rats with myelin basic protein (MBP) peptide 68-86 (MBP 68-86). We examined whether dendritic cells (DC) may have contributed to the amelioration of the disease process. These professional antigen-presenting cells (APC) not only activate T cells, but also tolerize T cells to antigens, thereby minimizing autoimmune reactions. We found that IL-4 administration enhanced proliferation of DC. In comparison with DC of PBS-treated rats, DC from IL-4-treated rats secreted high levels of interferon-gamma (IFN-gamma) and IL-10. Nitric oxide (NO) production by DC was also strongly augmented in IL-4-treated rats. In vitro studies showed that IL-4 stimulated DC expansion and that IFN-gamma enhanced NO production by DC. DC-derived NO promoted apoptosis of autoreactive T cells. These results indicate that nasal administration of IL-4 promotes activation of DC and induces production of IFN-gamma and IL-10 by DC. IL-10 suppresses antigen presentation by DC, while IFN-gamma induces NO production by DC which leads to apoptosis in autoreactive T cells. Such a DC-derived negative feedback loop might contribute to the clinical improvement observed in EAE.

Preclinical development of a recombinant toxin containing circularly permuted interleukin 4 and truncated Pseudomonas exotoxin for therapy of malignant astrocytoma.

Effective treatment is lacking for malignant glioblastoma/astrocytoma. We have identified interleukin-4 receptors (IL-4R) on human malignant astrocytoma. We demonstrate that 16 of 21 surgical samples of high-grade astrocytoma and glioblastoma but not normal brain tissues expressed IL-4R as assessed by reverse transcriptase PCR. We further demonstrate that human malignant astrocytoma cell lines express high-affinity IL-4R. Using a chimeric protein composed of circularly permuted IL-4 and a truncated form of Pseudomonas exotoxin A, we observed that this toxin IL4(38-37)-PE38KDEL) is highly cytotoxic to IL-4R-bearing glioblastoma cells. Compared with a previously reported IL4-PE chimeric protein (IL-PE4E), IL4(38-37)-PE38KDEL bound with higher affinity and was 3-30-fold more cytotoxic to glioblastoma cell lines. Upon intrathecal administration in monkeys, high cerebrospinal fluid IL4(38-37)-PE38KDEL levels were achieved using 2- and 6-microg/kg doses without any central nervous system or other abnormalities. IL4(38-37)-PE38KDEL levels were not detectable in the serum of any monkey studied. When IL4(38-37)-PE38KDEL was injected into the right frontal cortex of rats, localized necrosis was observed at 1000-ng/ml doses but not at < or = 100-ng/ml doses. We conclude that by localized administration, nontoxic levels of IL4(38-37)-PE38KDEL can be achieved, which may have significant cytotoxic activity against malignant astrocytoma.

Increased antitumor activity of a circularly permuted interleukin 4-toxin in mice with interleukin 4 receptor-bearing human carcinoma.

We reported previously that circularly permuted interleukin-4 (IL4), composed of amino acids 38-129 of IL4 connected by a linker peptide GGNGG to amino acids 1-37, is preferable to native IL4 for fusing to the amino terminus of truncated Pseudomonas exotoxin (PE) to make a recombinant toxin, because the new ligand-toxin junction results in improved IL4 receptor (IL4R)-binding (R. J. Kreitman et al., Proc. Natl. Acad. Sci. USA, 91: 6889-6893, 1994). We now report that the improved binding of circularly permuted IL4-toxin is associated with improved antitumor activity in tumor-bearing mice. For in vivo testing, we made an improved circularly permuted IL4-toxin, termed IL4(38-37)-PE38KDEL. It contains an N38D mutation at the amino terminus, allowing improved expression and large-scale production in Escherichia coli. It also contains the truncated toxin PE38KDEL, which is composed of amino acids 253-364 and 381-608 of PE, followed by KDEL. To evaluate antitumor activity, nude mice carrying s.c. tumors composed of IL4R-bearing human A431 epidermoid carcinoma cells were injected with recombinant toxins i.v. every other day for three doses. IL4(38-37)-PE38KDEL induced complete remissions in 80% of mice receiving 50 micrograms/kg x 3 and 100% of mice receiving 100 micrograms/kg x 3, while only 70% of mice receiving 200 micrograms/kg x 3 of the native IL4-toxin IL4-PE38KDEL obtained complete remission. Disease-free survival after obtaining complete remissions was higher in mice treated with IL4(38-37)-PE38KDEL 50 micrograms/Kg QOD x 3 than with IL4-PE38KDEL 200 micrograms/Kg QOD x 3 (P < 0.03). IL4(38-37)-PE38KDEL and IL4-PE38KDEL exhibited similar toxicity and pharmacokinetics in the mice, indicating that the improved antitumor activity of the circularly permuted IL4-toxin was due to its improved binding to the IL4R on the target cells.

Kinetics of the pleiotropic effect of interleukin 4 on the surface properties of human B-lymphoma cells.

Striking antigenic changes were elicited by interleukin 4 (IL-4) in the Farage human B-cell lymphoma line. After 2 days of incubation with IL-4 the expression of CD23, CD54 (ICAM-1), CD58 (LFA-3) was increased while the levels of CD21, CD22, CD38 were diminished. Prolonged incubation of Farage cells with IL-4 for 6-8 days led to increased expression of CD11a (LFA-1) CD39, CD40, and to disappearance of CD21 and CD38. The modulation of antigenic properties of Farage cells was associated with enhancement of their homotypic adhesiveness and the formation of giant clumps of cells. The recovery of Farage cells which had been exposed to IL-4 for six days was not complete and eleven days after withdrawal of the cytokine, these cells still displayed a lower level of CD21 and of CD38 than control cells. Cycling and non-cycling cells did not appear to differ in their antigenic properties, indicating that modification of the antigenic profile did not result from cell selection or cell arrest. These results showed that the pleiotropic effect of IL-4 on various cell surface structures on malignant human B cells proceeds at different rates suggesting that distinct metabolic pathways may regulate their expression.

Anti-cytokine antibodies as carrier proteins. Prolongation of in vivo effects of exogenous cytokines by injection of cytokine-anti-cytokine antibody complexes.

Anti-cytokine antibodies that block interactions between cytokines and cytokine receptors have been used to inhibit endogenous cytokine function. However, injection of mice with mixtures of IL-4 and either of two neutralizing anti-IL-4 mAb, at a cytokine/anti-cytokine mAb molar ratio of approximately 2:1, enhances and prolongs in vivo IL-4 activity, as measured by induction of increased spleen cell Ia expression. Although splenocyte Ia expression returns to baseline two days after mice are injected with free IL-4, soluble IL-4-anti-IL-4 mAb complexes still induce several-fold increases in Ia expression 3 days after injection. Complexes that contain as little as 400 ng of IL-4 have considerable in vivo stimulatory activity, and a maximal effect on splenocyte Ia expression is induced by injection of 2 micrograms of complexed IL-4. The stimulatory effect of IL-4-containing complexes on splenocyte Ia expression can be blocked by increasing the ratio of anti-IL-4 mAb to IL-4, by injection of anti-IL-4R mAb, and by in vivo aggregation of the complexes. Complexes of IL-4 with a non-neutralizing anti-IL-4 mAb do not have increased IL-4 agonist activity in vivo. These observations are most consistent with the possibility that neutralizing anti-IL-4 mAb act as carrier proteins that increase the in vivo half-life of IL-4 by preventing its excretion, and possibly, by preventing modification of its active site. The enhanced agonist effect of IL-4-anti-IL-4 mAb complexes is not unique; complexes of IL-3 with a neutralizing anti-IL-3 mAb have a greatly increased ability, compared with free IL-3, to stimulate mucosal mastocytosis, and complexes of IL-7 with a neutralizing anti-IL-7 mAb have a greatly increased ability, compared with free IL-7 or IL-7 complexed with a non-neutralizing anti-IL-7 mAb, to stimulate an increase in pre-B cell number. These observations suggest that complexes of cytokines and neutralizing anti-cytokine mAb may provide a generally useful way to increase the magnitude and duration of cytokine effects in vivo.

A phase I study of recombinant human interleukin-4 administered by the intravenous and subcutaneous route in patients with advanced cancer: immunological studies.

The effects of recombinant human interleukin-4 (rhu IL-4) on immunological parameters in patients receiving increasing doses of IL-4 in a Phase I trial were investigated. Peripheral blood mononuclear cells were phenotyped for a variety of lymphocyte markers, but no consistent effects were observed. However, increases in HLA Class II expression on monocytes were detected in four patients. NK and LAK activity were neither induced nor augmented by IL-4 treatment. Slight increases in proliferative responses to mitogens and cytokines were observed in some patients. The latter observations and other clinical studies suggest that a combination of IL-4 with IL-2 may be more effective in Phase II clinical trials.

Recombinant human interleukin-4 (rhu IL-4) administered by the intravenous and subcutaneous routes in patients with advanced cancer--a phase I toxicity study and pharmacokinetic analysis.

19 patients with advanced cancer were entered into a phase I study of recombinant human interleukin-4 (rhu IL-4). The predominant clinical side-effects included flu-like symptoms, gastrointestinal upset, lethargy and transient hypotension. In addition, there were several cases of capillary leak syndrome. 2 cases of gastrointestinal haemorrhage occurred; this was life threatening in 1 patient. The maximum tolerated dose (MTD) was 400 micrograms/m2/day. Biochemical toxicity was limited to asymptomatic elevation of liver enzymes suggesting IL-4 induced liver damage. Pharmacokinetic analysis following the intravenous bolus injection has shown that IL-4 is rapidly cleared (mean T1/2 = 19 +/- 8.7 min) from a small compartment (mean Vd = 4.9 +/- 3.68 l) probably indicating that IL-4 is retained in the systemic circulation or at most the extracellular fluid volume. 2 patients with non-Hodgkin lymphomas (NHL) showed a transient response to IL-4 whilst a third patient with NHL showed transient disease progression.