Binding and capture of human interferon-alpha by reverse evaporation vesicles, multilamellar vesicles, and small unilamellar vesicles

PEGylated liposomes for topical vaginal therapy improve delivery of interferon alpha

Recent studies regarding mucosal drug delivery indicate that nanosystems with surface-available polyethylene glycol (PEG) are able to penetrate mucus barrier, assure closer contact with the epithelium, and improve drug delivery to vagina. In the present work, we developed the mucus-penetrating PEGylated liposomes containing interferon alpha-2b (IFN α-2b), destined to provide localized therapy for human papilloma virus (HPV) vaginal infections. The PEGylated liposomes were of a mean size of 181±8nm, bearing a negative zeta potential of - 13mV and an entrapment efficiency of 81±10%. In vitro release experiments on model membrane showed a nearly non-existent IFN α-2b release from both the control and liposomally-associated IFN α-2b. However, the ex vivo penetration studies performed on the vaginal tissue obtained from pregnant sheep, showed the clear elevated IFN α-2b penetration from PEGylated liposomes as compared to the control. Furthermore, mucin studies confirmed the absence of interaction between the PEG-modified liposomes and mucin, confirming their ability to penetrate mucus and reach the deeper epithelium. The system holds a promise in improving topical delivery of IFN α-2b through enhanced efficacy of local anti-viral therapy.

Particle-mediated delivery of cytokines for immunotherapy

The ability of cytokines to direct the immune response to vaccination, infection and tumors has motivated their use in therapy to augment or shape immunity. To avoid toxic side effects associated with systemic cytokine administration, several approaches have been developed using particle-encapsulated cytokines to deliver this cargo to specific cell types and tissues. Initial work used cytokine-loaded particles to deliver proinflammatory cytokines to phagocytes to enhance antimicrobial and antitumor responses. These particles have also been used to create a cytokine depot at a local site to supplement prophylactic or antitumor vaccines or injected directly into solid tumors to activate immune cells to eliminate established tumors. Finally, recent advances have revealed that paracrine delivery of cytokines directly to T cells has the potential to enhance T-cell mediated therapies. The studies reviewed here highlight the progress in the last 30 years that has established the potential of particle-mediated cytokine immunotherapy.

Pegylated protein encapsulated multivesicular liposomes: a novel approach for sustained release of interferon alpha

Hepatitis C viral chemotherapy suffers from a relatively short half-life of the interferon alpha-2a (IFN alpha). To address this issue, we investigated the effects of polyethylene glycol modification and their subsequent encapsulation in multivesicular liposomes (MVLs), on the release properties of IFN alpha. In the present study, interferon-alpha was conjugated with methoxy-polyethylene glycol (mPEG, MW 5000). Prepared IFN alpha-mPEG5000 conjugate (IFN alpha-mPEG5000) was purified with size exclusion chromatography. The relative in vitro anti-viral activity of pegylated interferon alpha-2a was found to 87.9% of the unmodified IFN alpha. Pegylated IFN alpha encapsulated multivesicular liposomes were prepared by double emulsification technique followed by evaporation of organic solvents from chloroform ether spherules suspended in water. Prepared MVLs were then characterized for shape, size, vesicle count, encapsulation efficiency, and in vitro release rate. In process stability studies of pegylated IFN alpha protein exhibited better stability when exposed to chloroform: diethyl ether (1:1 ratio) mixture as well as variable vortexing time as compared to native IFN alpha. Relatively high percentage of encapsulation of protein ( approximately 75%) was achieved. In vitro release profile of pegylated IFN alpha-mPEG5000 containing MVLs in the PBS showed lower initial burst release with sustained and incomplete release over a period of 1 week. In contrast, native IFN alpha entrapped MVLs were observed as higher initial burst release, i.e., nearly 35% followed by almost complete release. The results confirmed the possibility of multivesicular liposomes as a long-acting or sustained-release delivery system using a combination of pegylation and encapsulation technique for controlled delivery of interferon alpha.

Antifibrogenic effects of liposome-encapsulated IFN-alpha2b cream on skin wounds in a fibrotic rabbit ear model

This study was conducted to assess the ability of a dermal cream containing liposome-encapsulated interferon- alpha2b (IFN-alpha2b) (LIPO+IFN) to improve hypertrophic scarring in open and reepithelialized dermal wounds in a rabbit fibrotic ear model. Full-thickness skin wounds were made in New Zealand white rabbits, and were either left untreated, treated on day 16 postsurgery (open wound), or treated on day 23 postsurgery (reepithelialized wound) with either LIPO+IFN or liposome alone (LIPO). The conditions of the wounds were monitored until day 35 postsurgery, when hypertrophic scar formation reached its peak. Dry wound weight, scar thickness, hypertrophic index (HI), and tissue cellularity of treated and untreated wounded tissue samples were evaluated as an index for scar formation. The results of this study showed that reepithelialized wounds treated with LIPO+IFN and to a lesser extent with LIPO alone were reduced in thickness, HI, and cellularity compared with untreated control wounds or LIPO+IFN-treated open wounds. Dry wound weight was also reduced but not significantly. The findings of this study suggest that LIPO+IFN is more effective than using LIPO alone in reducing the scar formation in a rabbit fibrotic ear model. Further investigation is required to confirm these results.

Liposome associated interferon-alpha-2b functions as an anti-fibrogenic factor in dermal wounds in the guinea pig

We have previously reported that interferon-alpha-2b (IFN-alpha-2b) can be encapsulated in liposomes without compromising its anti-fibrogenic effects on dermal fibroblasts in vitro. This study was conducted to determine whether this preparation applied topically to guinea pig wounds can affect their healing. The rationale for this approach is that systemic administration of IFN-alpha-2b by injection for treatment of dermal fibrosis is uncomfortable, requires a large quantity of the cytokine and cannot be easily used in children. Liposomes are potentially useful vehicles for the topical delivery of drugs. Empty sonicated liposome vesicles were mixed with various concentrations of IFN-alpha-2b and then dried and rehydrated. An enzyme-linked immunosorbent assay (ELISA) was used to determine the efficiency of encapsulation and the stability of the preparation under experimental conditions. A total of 36 full thickness skin wounds (6/animal, 3 on each side) were made with an 8 mm disposable punch. Each wound on the right side received cream (100 mg/wound) containing 3000 units of liposome-encapsulated IFN-alpha-2b, while wounds on the left side received cream containing empty liposomes. There was a significant reduction in rate of contraction of wounds treated with IFN-alpha-2b as early as 5 days after wounding. This reduction remained significant up to 10 days. Northern analysis, used to evaluate the expression of mRNAs for type I and type III collagens in response to IFN-alpha-2b showed a marked reduction in abundance of the transcripts for the pro-alpha1(I) chain of type 1 collagen on days 11 and 14 after wounding. Similarly, the level of mRNA for type III procollagen was markedly reduced as early as day 7 and remained depressed up to day 14. These findings were consistent with results obtained for the total collagen content in tissue samples. Cellularity of the IFN-alpha-2b-treated wounds, assessed by vimentin content, was also markedly reduced at day 7 and remained depressed up to day 14. Liposome associated IFN-alpha-2b applied 5 days after completion of epithelialization reduced mRNA for the pro-alpha1(I) chain of type 1 collagen, confirming its transepidermal penetration and effectiveness. The activity of liposome-associated IFN-alpha-2b in vivo supports the concept of the topical use of this anti-fibrogenic agent for treatment of fibroproliferative disorders.

The antifibrogenic effects of liposome-encapsulated IFN-alpha2b cream on skin wounds

Interferons (IFN), including IFN-alpha2b, have been used as antifibrogenic factors to modulate the excessive production of extracellular matrix (ECM) associated with dermal fibroproliferative disorders. This study was conducted to examine the ability of a dermal cream containing liposome-encapsulated IFN-alpha2b (LIPO+IFN) to affect the synthesis of ECM in open and reepithelialized wounds. Full-thickness skin wounds in 32 female Hartley guinea pigs (6 wounds per animal, 3 on each side) were made with an 8-mm biopsy punch. Each wound on the right side received 3,000 U LIPO+IFN, whereas wounds on the left side received cream containing empty liposomes. Histologic examination revealed a significant reduction in scar formation in LIPO+IFN-treated but not in vehicle-treated wounds. Northern analysis showed reductions in type I procollagen mRNA in healed wounds treated with LIPO+IFN (day 4 groups: 1596.9 +/- 207 vs. 3710.2 +/- 493 densitometry units, p < 0.01, n = 8). This was consistent with a reduction in the concentration of collagen in the tissue, assayed as 4-hydroxyproline (day 4 group: 38.5 +/- 3.8 vs. 54.5 +/- 3.9 microg per tissue, p < 0.01, n = 8). Even when applied to reepithelialized wounds, LIPO+IFN caused a marked reduction in type I collagen mRNA (1938.5 +/- 579 vs. 4085.7 +/- 1271 densitometry units, p < 0.01, n = 8). These findings support the concept of the early topical use of this antifibrogenic agent for treatment of dermal fibroproliferative disorders, such as hypertrophic scars.

Liposome-associated interferon-alpha-2b functions as an anti-fibrogenic factor for human dermal fibroblasts

This study was conducted to determine whether interferon-alpha-2b (IFN-alpha-2b) can be encapsulated in liposomes without compromising its anti-fibrogenic effects on human dermal fibroblasts. The rationale for this approach is that systemic administration of IFN-alpha-2b by injection for treatment of dermal fibrosis is uncomfortable, requires a large quantity of the cytokine, and cannot be easily used in children. Liposomes are potentially useful as vehicles for the topical delivery of drugs if they can be encapsulated without loss of biologic activity. Empty sonicated vesicles composed of dioleoyl-phosphatidylcholine:dioleoyl-phosphatidylglycerol at a molar ratio of 7:3 were mixed with various concentrations of IFN-alpha-2b and then dried and rehydrated. An enzyme-linked immunosorbent assay (ELISA) was used to determine the efficiency of encapsulation and the stability of the preparation under experimental conditions. Greater than 80% of added IFN-alpha-2b became associated with the liposomes and remained encapsulated for up to 5 d at 4 degrees C. The rate of release increased markedly at 37 degrees C. Liposome-encapsulated IFN-alpha-2b (2000 units per ml) significantly reduced the proliferation of dermal fibroblasts (60 +/- 8.8 vs. 100 +/- 8, mean +/- SEM, p < 0.05, n = 8) and the levels of mRNA for type I (41.5 +/- 8.7% vs 100 +/- 18, p < 0.05, n = 4) and type III (68 +/- 8.4% vs 100 +/- 4.9%, p < 0.05, n = 3) procollagen, as analyzed on northern blots. This was consistent with the reduction found in collagen in conditioned medium from treated fibroblasts. In contrast, treatment increased levels of mRNA for collagenase (241 +/- 42% vs 100 +/- 3.4, p < 0.05, n = 3) and collagenase activity (289 +/- 5.8% vs 100 +/- 10.9%, p < 0.05, n = 9) in conditioned medium. This last effect was probably not due to a reduction in TIMP-1 (tissue inhibitor of metalloproteinase-1) because levels of mRNA for this inhibitor were not lower in treated cells. The efficacy of liposome-associated IFN-alpha-2b in vitro supports the concept of the topical use of this anti-fibrogenic agent for treatment of fibroproliferative disorders.

Optimization and characterization of freeze-dried multilamellar liposomes incorporating different standardized allergen extracts

Desensitization therapy for type I allergy is now current practice. Liposomes have been proposed as a support for allergens to improve safety and effectiveness. The aim of this work was to optimize liposomal formulations of three different standardized allergen extracts and to test their allergenicity in vitro and in a preclinical trial. Allergen extracts (Dactylis glomerata, Dermatophagoides pteronyssinus, and cat hair and dander) were associated with multilamellar liposomes of varying compositions at different pH. Liposome-bound allergens were quantified by RAST inhibition after ultracentrifugation, and analyzed qualitatively by SDS-PAGE followed by immunoblotting. Their allergenicity was assessed by basophil degranulation in vitro, as compared with the allergenicity of an aqueous extract, and by skin tests in allergic subjects. The best association, about 50% of the added allergen, was obtained with negatively charged liposomes, when the pH of the allergen solution was adjusted so as to impart a net positive charge to the proteins. One-third of the liposome-associated allergens was located on the surface of the liposomes and was free to interact with antibody, as shown by RAST inhibition assays and the basophil degranulation test; the remaining two-thirds was encapsulated within the liposomes. All the major immunoreactive proteins in the extract were included. These liposomes could be readily freeze-dried and reconstituted without changing their properties. This study reveals the allergenic characteristics of liposomes and suggests their potential use in the treatment of allergic patients.

Liposomes as carriers of cancer chemotherapy. Current status and future prospects

Chemotherapy is a modality of cancer therapy that needs much improvement. Development of a new chemical entity is very costly and time consuming, but improvements in delivery of existing agents may yield more rapid clinical results. Liposomes and other lipid-based drug delivery systems have the advantage, in this context, of utilising no new chemical entities. In terms of mechanism of action, tumour targeting has been the focus of much work in liposomal drug delivery. The recent development of liposomes with longer circulation times has led to improved tumour targeting in animal studies. Other mechanisms of action, such as release from drug depot formulations, heat-triggered local drug release, and transfection of genetic materials, may prove to be useful in humans. Liposomal formulations of more than a dozen antineoplastic agents have shown promise in vitro and in animal models. Somewhat mundane, but nevertheless crucial, issues of medical rationale and formulation engineering, and commercial considerations, have slowed testing in patients with cancer. However, 3 antineoplastic agents, doxorubicin, daunorubicin and cytarabine, are in advanced stages of clinical testing in humans. One or more of these should prove to be a medically useful and commercially viable product within the next few years.

Liposomes and biotherapeutics

Application of liposomes as delivery system for biotherapeutic peptides and proteins may offer important therapeutic advantages over existing delivery methods. Several approaches towards achieving improved delivery of biotherapeutics with liposomes are outlined. Although the literature on this topic is sporadic and frequently incomplete, enough of a research foundation exists to justify the conclusion that liposomes can play an important role in the formulation and delivery of biotherapeutics. However, it will be necessary to understand more fully the mechanisms of action before optimum liposomal dosage forms can be designed.

Antiviral and antiproliferative properties of liposome-associated human interferon-gamma

Recombinant human interferon-gamma (rHuIFN-gamma) was associated with liposomes in an attempt to improve its therapeutic efficiency. It was associated with liposomes composed of phosphatidylserine (PS) and phosphatidylcholine (PC) at a ratio of 3:7, and of PS:PC and cholesterol (CHOL) at a ratio of 1:4:5 with efficiencies of 13% and 21%, respectively. The lipid composition influenced the antiviral activity of the liposome-complexed IFN-gamma tested against vesicular stomatitis virus. IFN associated with PS:PC liposomes was fully bioavailable and degraded by trypsin treatment. In contrast, PS:PC:CHOL-IFN was resistant to trypsin, and appeared latent as its full biological activity was seen only after disruption of the liposomes with detergent. Four human tumor cell lines were exposed to free and liposome-associated IFN-gamma. The growth of three solid tumor lines (colon, bladder, and lung) was inhibited by similar concentrations of free IFN and PS:PC-IFN. In contrast, less PS:PC-IFN than free IFN was needed to inhibit histiocytic lymphoma cells. Higher concentrations of PS:PC:CHOL-IFN than of free IFN were needed to inhibit growth of all four cell lines. The specificity of these effects of liposome-associated IFN-gamma were shown by their partial or complete neutralization by antibody to IFN-gamma. When liposome-IFN complexes of either type were stored at 4 degrees C, 30% of the IFN activity remained after 7 days; thereafter, decay was minimal over the next 3 weeks. These data show the formation of stable HuIFN-gamma-liposomes and indicate that the lipid components of these complexes influence their antiviral and antiproliferative activity for several different cell types.

Topical delivery of liposomally encapsulated interferon evaluated in a cutaneous herpes guinea pig model

The topical delivery of liposomally encapsulated interferon was evaluated in the cutaneous herpes simplex virus guinea pig model. Application of liposomally entrapped interferon caused a reduction of lesion scores, whereas application of interferon formulated as a solution or as an emulsion was ineffective. The method of liposomal preparation rather than the lipid composition of the bilayers appeared to be the most important factor for reducing lesion scores. Only liposomes prepared by the dehydration-rehydration method were effective. This finding implied that the dehydration and subsequent rehydration of the liposomes facilitate partitioning of the interferon into liposomal bilayers, where the drug is positioned for transfer into the lipid compartment of the stratum corneum. Liposomes do not appear to function as permeation enhancers but seem to provide the needed physicochemical environment for transfer of interferon into the skin.

Preparation and use of liposomes in the treatment of microbial infections

The potential application of liposomes to drug delivery has been apparent since 1965, when these phospholipid vesicles were first described by Bangham. Since then, experiments on animals have shown that liposome encapsulation can dramatically alter the distribution of drugs in the body and their rate of clearance. These pharmacokinetic differences, as well as other less well-understood effects, can result in reduced toxicity and enhanced efficacy of the encapsulated drug. The vast majority of studies on the therapeutic use of liposomes have involved the delivery of drugs used in cancer chemotherapy and metabolic storage diseases, but there is now more literature on the use of liposomes for the delivery of antimicrobial drugs and immunomodulating agents. This review briefly discusses the general properties of liposomes and the rationale for their use in antimicrobial drug delivery and immunomodulation, as well as the encapsulation of specific agents and the effect of encapsulation on the treatment of infectious diseases.

Biological activity of liposome-encapsulated murine interferon gamma is mediated by a cell membrane receptor

Recombinant murine gamma interferon (rMuIFN-gamma) was found to bind reversibly to a specific high-affinity surface receptor on L929 cells; neither murine alpha or beta nor human gamma IFN competed for receptor binding. Encapsulation of the rMuIFN-gamma in either negatively or positively charged liposomes reduced its immediate ability to bind to this surface receptor. Disruption of liposome integrity with detergent resulted in full ability of the rMuIFN-gamma to bind to the membrane receptor. Incubation of the liposomal IFN in serum-containing medium resulted in significant leakage so that the IFN was able to bind to its surface receptor. Assessment of the biological activity of the rMuIFN-gamma preparations revealed that full antiviral activity was observed in vitro with the liposomal IFN preparations without their prior disruption by detergent. The antiviral activity observed with either free or liposomal IFN was neutralized completely by antibodies against rMuIFN-gamma. Both free and liposomal rMuIFN-gamma, in conjunction with bacterial lipopolysaccharide, were also able to activate murine peritoneal macrophages to the tumoricidal state. Again, this activity of both free and liposomal IFN could be neutralized completely by antibody. These results indicate that although rMuIFN-gamma can be effectively incorporated into liposomes, it must ultimately leak out of the liposome in order to mediate its biological effects; these effects are triggered after the IFN binds to its cell surface receptors.

Microinjected interferon does not promote an antiviral response in Hela cells

Human fibroblast interferon (Hu IFN beta) was directly introduced with glass micropipets into the cytoplasm of Hela cells. Such an injection of more than 10(4) molecules per cell failed to induce any antiviral state when challenged with vesicular stomatitis virus (VSV). These findings are discussed in relation to the possible role of internalization in the mechanism of antiviral action of interferon.

Partial dissociation of antiviral and antimitogenic activities of murine interferon after its incorporation into liposomes

Murine fibroblast interferon (MuIFN, 90% beta, 10% alpha) was associated with both positively and negatively charged liposomes formed by reverse-phase evaporation. This interferon-liposome association occurred predominantly in a manner that resulted in protection of a significant portion of the IFN's antiviral activity from trypsin digestion, yet also permitted biological expression of this activity without prior liposome disruption. A differential dissociation of antiviral and antimitogenic activities was observed with MuIFN associated with positively vs negatively charged liposomes, as reflected by differential sensitivities to trypsin inactivation. This may reflect either (1) differential associations of various molecular species of MuIFN with liposomes, or (2) that different portions of the IFN molecule are responsible for the antiviral and the antimitogenic activities.

Altered pharmacological properties of liposome-associated human interferon-alpha

Human interferon-alpha was associated in different ways with positively (stearylamine) and negatively (phosphatidylserine) charged phosphatidylcholine multilamellar vesicles, depending on the presence or absence of a cholesterol component. Inclusion of cholesterol resulted in interferon that was significantly (P = 0.0001) more deeply internalized within the liposomes, such that detergent disruption was necessary before most of the interferon activity was expressed. Interferon was stably associated with stearylamine-containing liposomes, both with and without a cholesterol component. However, inclusion of cholesterol in the phosphatidylserine-containing liposomes was necessary for stable association of the interferon for more than 2 days at 4 degrees C or for more than 24 h at 37 degrees C. After intramuscular injection into mice, liposome-associated interferon in reverse-phase evaporation vesicles was retained at the local site of injection significantly longer than free interferon. Even 3 days after intramuscular injection, stearylamine-containing liposomes with or without cholesterol resulted in local interferon levels that were comparable to the peak levels obtained 2 to 4 h after free interferon was injected. In contrast, free interferon was not detectable in the local muscles 24 h after injection of 10(4.6) U. Liposomes containing phosphatidylserine and cholesterol resulted in intermediate levels of local interferon retention; without a cholesterol component, phosphatidylserine-containing liposomes resulted in no increased local interferon retention compared with the results when free interferon was injected.

Altered pharmacologic properties of liposome-associated human interferon-alpha. II

Association of human interferon-alpha with multilamellar vesicles and reverse-phase evaporation vesicles resulted in altered retention and distribution of the interferon after injection into mice. Intramuscular injection of liposomal-interferon, after extrusion through 0.2 mu filters, resulted in significantly increased localized retention of interferon. Liposomal-interferon was retained locally from one to three days, depending on liposome composition, whereas an equivalent injection of free interferon was undetectable after 24 hrs. Intravenous injection of the liposomal-interferon preparations resulted in increased interferon levels in lung, spleen, and liver as compared to injection of free interferon. Preparation of small unilamellar vesicles in the presence of interferon revealed differences in modes of association of different species with the liposomes, based on differential titers on human vs. bovine cells.