Glucocorticosteroids in nano-sterically stabilized liposomes are efficacious for elimination of the acute symptoms of experimental cerebral malaria

Cerebral malaria is the most severe complication of Plasmodium falciparum infection, and a leading cause of death in children under the age of five in malaria-endemic areas. We report high therapeutic efficacy of a novel formulation of liposome-encapsulated water-soluble glucocorticoid prodrugs, and in particular β-methasone hemisuccinate (BMS), for treatment of experimental cerebral malaria (ECM), using the murine P. berghei ANKA model. BMS is a novel derivative of the potent steroid β-methasone, and was specially synthesized to enable remote loading into nano-sterically stabilized liposomes (nSSL), to form nSSL-BMS. The novel nano-drug, composed of nSSL remote loaded with BMS, dramatically improves drug efficacy and abolishes the high toxicity seen upon administration of free BMS. nSSL-BMS reduces ECM rates in a dose-dependent manner and creates a survival time-window, enabling administration of an antiplasmodial drug, such as artemisone. Administration of artemisone after treatment with the nSSL-BMS results in complete cure. Treatment with BMS leads to lower levels of cerebral inflammation, demonstrated by changes in cytokines, chemokines, and cell markers, as well as diminished hemorrhage and edema, correlating with reduced clinical score. Administration of the liposomal formulation results in accumulation of BMS in the brains of sick mice but not of healthy mice. This steroidal nano-drug effectively eliminates the adverse effects of the cerebral syndrome even when the treatment is started at late stages of disease, in which disruption of the blood-brain barrier has occurred and mice show clear signs of neurological impairment. Overall, sequential treatment with nSSL-BMS and artemisone may be an efficacious and well-tolerated therapy for prevention of CM, elimination of parasites, and prevention of long-term cognitive damage.

Factors affecting DNA binding and stability of association to cationic liposomes

Lipoplexes are complexes formed between cationic liposomes (L(+)) and polyanionic nucleic acids (P(-)). They are commonly used in vitro and in vivo as a nucleic acid delivery system. Our study aims are to investigate how DOTAP-based cationic liposomes, which vary in their helper lipid (cholesterol or DOPE) and in media of different ionic strengths affect the degree, mode of association and degree of condensation of pDNA. This was determined by ultracentrifugation and gel electrophoresis, methods based on different physical principles. In addition, the degree of pDNA condensation was also determined using the ethidium bromide (EtBr) intercalation assay. The results suggest that for cationic lipid compositions (DOTAP/DOPE and DOTAP/cholesterol), 1.5 M NaCl, but not 0.15 M NaCl, both prevent lipoplex formation and/or induce partial dissociation between lipid and DNA of preformed lipoplexes. The higher the salt concentration the greater is the similarity of DNA condensation (monitored by EtBr intercalation) between lipoplex DNA and free DNA. As determined by ultracentrifugation and agarose gel electrophoresis, 30-90% of the DNA is uncondensed. SDS below its critical micellar concentration (CMC) induced "de-condensation" of DNA without its physical release (assessed by ultracentrifugation) for both DOTAP/DOPE and DOTAP/cholesterol lipoplexes. As was assessed by agarose gel electrophoresis SDS induced release of 50-60% of DNA from the DOTAP/cholesterol lipoplex but not from the DOTAP/DOPE lipoplex. This study shows that there are conditions under which DNA is still physically associated with the cationic lipids but undergoes unwinding to become less condensed. We also proved that the helper lipid affects level and strength of the L(+) and DNA(-) electrostatic association; these interactions are weaker for DOTAP/cholesterol than for DOTAP/DOPE, despite the fact that the positive charge and surface pH of DOTAP/cholesterol and DOTAP/DOPE are similar.

Amphipathic weak acid glucocorticoid prodrugs remote-loaded into sterically stabilized nanoliposomes evaluated in arthritic rats and in a Beagle dog: a novel approach to treating autoimmune arthritis

OBJECTIVE

The use of glucocorticoids (GCs) in rheumatoid arthritis is limited by side effects related to unfavorable pharmacokinetics and biodistribution. Liposomal GC formulations have been studied since the 1970s in an attempt to overcome this obstacle, but none has entered clinical use. We undertook this study to determine whether a novel approach could overcome the limitations that have thus far prevented the clinical use of these formulations: low drug:lipid ratio, low encapsulation efficiency, and lack of controlled release.

METHODS

We used approximately 80-nm sterically stabilized (pegylated) nanoliposomes (NSSLs), which were remote-loaded with an amphipathic weak acid GC (such as methyl prednisolone hemisuccinate) utilizing an intraliposome (aqueous compartment)-high/extraliposome (bulk medium)-low transmembrane calcium acetate gradient. This unique method actually "traps" the GC in the liposomal aqueous phase as a calcium-GC precipitate.

RESULTS

Our liposome formulation exhibited high encapsulation efficiency (94%) and a high drug:lipid mole ratio (0.41) and demonstrated controlled release of the encapsulated GC during systemic circulation and in inflamed paws in rats with adjuvant-induced arthritis. In addition, both in arthritic rats and in a Beagle dog, we showed the pharmacokinetic advantage of using liposomes as GC carriers. Finally, we demonstrated the superior therapeutic efficacy of our liposome formulation over that of free GCs in arthritic rats, both in early and in peak disease stages.

CONCLUSION

Amphipathic weak acid GCs remote-loaded into approximately 80-nm NSSLs overcome past limitations of liposomal GC formulations. The unique loading method, which also leads to controlled release, improves the therapeutic effect both systemically and locally. Such a development has great potential for improving GC therapy.

Immunogenicity and safety of a novel IL-2-supplemented liposomal influenza vaccine (INFLUSOME-VAC) in nursing-home residents

Influenza and its complications account for substantial morbidity and mortality, especially among the elderly. In young adults, immunization provides 70-90% protection, while among the elderly the vaccine may be only </=50% effective; hence, the need for new, more immunogenic vaccines. We compared the safety and immunogenicity of a novel, interleukin-2 (IL-2) -supplemented trivalent liposomal influenza vaccine (designated INFLUSOME-VAC) with that of a commercial trivalent split virion vaccine in community-residing elderly volunteers (mean age 81 years) in winter of 2000/2001. Eighty-one individuals were randomly assigned to be vaccinated intramuscularly, either with the standard vaccine (n=33) or with INFLUSOME-VAC (n=48) prepared from the former. The two vaccines contained equal amounts of hemagglutinin (HA) ( approximately 15 microgram of each viral strain); INFLUSOME-VAC consisted of liposomal antigens admixed with liposomal human IL-2 (Lip IL-2) (33 microgram = 6x10(5) IU/dose). At 1 month post-vaccination, seroconversion rates (tested by hemagglutination inhibition) for the A/New Caledonia (H1N1) and A/Moscow (H3N2) strains were significantly higher (P=0.04) in the INFLUSOME-VAC group (65 versus 45%, 44 versus 24%, respectively). Moreover, INFLUSOME-VAC induced a greater anti-neuraminidase (NA-N2) response (P<0.05). Anti-IL-2 antibodies were undetected, and no increase in anti-phospholipid IgG antibodies was found in the INFLUSOME-VAC group. Adverse reactions were similar in both groups. Thus, INFLUSOME-VAC appears to be both safe and more immunogenic than the currently used vaccine in the elderly.

Immunogenicity and safety of a novel liposomal influenza subunit vaccine (INFLUSOME-VAC) in young adults

Influenza and its complications account for substantial morbidity and mortality among young adults and especially among the elderly. In young adults, immunization provides 70-90% protection, while among the elderly the vaccine may be only 30-40% effective; hence the need for new, more immunogenic vaccines. We compared the safety and immunogenicity of a novel IL-2-supplemented liposomal influenza vaccine (designated INFLUSOME-VAC) with that of a commercial subunit vaccine and a commercial split virion vaccine in young adults (mean age 28 years) in the winter of 1999-2000. Seventy-three healthy young adults were randomly assigned to be vaccinated intramuscularly with the following: a commercial subunit vaccine (n = 17, group A), INFLUSOME-VAC (n = 36, group B), and a commercial split virion vaccine (n = 20, group C). The three vaccines contained equal amounts of hemagglutinin (approximately 15 microg each) from the strains A/Sydney (H3N2), A/Beijing (H1N1), and B/Yamanashi. INFLUSOME-VAC induced higher geometric mean HI titers and higher-fold increases in HI titers against all three strains, compared with the two commercial vaccines. In addition, seroconversion rates for the A/Sydney and B/Yamanashi strains were significantly higher (P < 0.05) compared with the split virion vaccine, and significantly higher for the three strains compared with the subunit vaccine (69-97% vs 35-65%, P < or = 0.02). Moreover, the anti-neuraminidase response was significantly greater (P = 0.05) in group B vs group A. INFLUSOME-VAC caused mild local pain at the injection site in a significantly higher proportion of the vaccinees (83%). Thus, INFLUSOME-VAC is an immunogenic and safe vaccine in young adults.

DOTAP cationic liposomes prefer relaxed over supercoiled plasmids

Cationic liposomes and DNA interact electrostatically to form complexes called lipoplexes. The amounts of unbound (free) DNA in a mixture of cationic liposomes and DNA at different cationic lipid:DNA molar ratios can be used to describe DNA binding isotherms; these provide a measure of the binding efficiency of DNA to different cationic lipid formulations at various medium conditions. In order to quantify the ratio between the various forms of naked DNA and supercoiled, relaxed and single-stranded DNA, and the ratio between cationic lipid bound and unbound DNA of various forms we developed a simple, sensitive quantitative assay using agarose gel electrophoresis, followed by staining with the fluorescent cyanine DNA dyes SYBR Green I or SYBR Gold. This assay was compared with that based on the use of ethidium bromide (the most commonly used nucleic acid stain). Unlike ethidium bromide, SYBR Green I DNA sensitivity and concentration-dependent fluorescence intensity were identical for supercoiled and nicked-relaxed forms. DNA detection by SYBR Green I in solution is approximately 40-fold more sensitive than by ethidium bromide for double-stranded DNA and approximately 10-fold for single-stranded DNA, and in agarose gel it is 16-fold more sensitive for double-stranded DNA compared with ethidium bromide. SYBR Gold performs similarly to SYBR Green I. This study shows that: (a) there is no significant difference in DNA binding isotherms to the monocationic DOTAP (DOTAP/DOPE) liposomes and to the polycationic DOSPA (DOSPA/DOPE) liposomes, even when four DOSPA positive charges are involved in the electrostatic interaction with DNA; (b) the helper lipids affect DNA binding, as DOTAP/DOPE liposomes bind more DNA than DOTAP/cholesterol; (c) in the process of lipoplex formation, when the DNA is a mixture of two forms, supercoiled and nicked-relaxed (open circular), there is a preference for the binding to the cationic liposomes of plasmid DNA in the nicked-relaxed over the supercoiled form. This preference is much more pronounced when the cationic liposome formulation is based on the monocationic lipid DOTAP than on the polycationic lipid DOSPA. The preference of DOTAP formulations to bind to the relaxed DNA plasmid suggests that the binding of supercoiled DNA is weaker and easier to dissociate from the complex.

Delivery of cytokines by liposomes: hematopoietic and immunomodulatory activity of interleukin-2 encapsulated in conventional liposomes and in long-circulating liposomes

Although liposomal delivery of interleukin-2 (IL-2) and other cytokines improves their pharmacokinetics and biologic activity in vivo, there are no comparative functional studies of various liposomal formulations as cytokine carriers. In the present investigation, recombinant human IL-2 was encapsulated in two formulations of large (mean diameter 0.75-1.5 microns) multilamellar vesicles (MLV, referred to as conventional liposomes) or in small (mean diameter, 60 nm), unilamellar, long-circulating liposomes (referred to as sterically stabilized liposomes, SSL). The biologic activity of the liposomal formulations and of free IL-2 was tested in parallel in vitro and in mice. The main observations were as follows: (a) All the liposomal IL-2 (Lip-IL-2) formulations were more efficient than soluble IL-2 in stimulating spleen cell proliferation and lymphokine-activated killer (LAK) cell activation in vitro, particularly at low cytokine doses (1-100 CU/mL). (b) After i.v. injection, the circulation time of MLV-IL-2 and SSL-IL-2 was 7 and 17 times greater, respectively, than that of soluble IL-2. (c) In comparison with IL-2, all Lip-IL-2 formulations caused a marked increase in the leukocyte levels in blood, spleen, and peritoneal exudate, especially in those of myeloid origin (neutrophils, eosinophils, immature granulocytes, and macrophages). (d) Although SSL-IL-2 exhibited the longest circulation time, MLV-IL-2 was more potent in elevating leukocyte levels and in triggering LAK cell activity in vivo. (e) The route of Lip-IL-2 administration greatly affected the immunomodulatory activity in the various compartments. (f) MLV-IL-2 proved to be a much more efficient immunoadjuvant than free IL-2 for influenza subunit vaccines as well as for tumor cell vaccines. These findings lend support to our previous studies in which we demonstrated the superior immunomodulatory activity of liposomal IL-2, and suggest that cytokine pharmacokinetics, biodistribution, and pharmacodynamics are markedly influence both by liposomal formulation and route of administration.

Enhancement of antitumor activity of polyethylene glycol-coated liposomal doxorubicin with soluble and liposomal interleukin 2

Polyethylene glycol-coated liposomal doxorubicin (Doxil) has a sustained release profile and a mild myelosuppressive effect that may enable a beneficial interaction with lymphocyte-activating cytokines, such as interleukin 2 (IL-2). Previous studies have shown that liposome entrapment of IL-2 potentiates its immunomodulatory effects and reduces the need for frequent dosing. We assessed the therapeutic effect of Doxil (8 mg/kg) followed by free or liposomal IL-2 (50,000 Cetus Units x 3) in mice bearing M109 lung adenocarcinoma transplanted i.v. or i.p. Doxil was always administered i.v., whereas IL-2 was given i.v. in the i.v. M109 model and i.p. in the i.p. M109 model. The optimal combined treatment was significantly more effective than liposomal chemotherapy alone, producing tumor-free, long-term survivors in 100% (i.v. M109) and 94% (i.p. M109) of the mice, compared with 50% and 56%, respectively, for Doxil alone. The efficacy boost of IL-2 appeared to be formulation dependent, with free IL-2 and IL-2 in small unilamellar vesicles most active in the i.v. tumor model, and IL-2 in multilamellar vesicles most active in the i.p. tumor model. The combination of Doxil with free or liposomal IL-2 was devoid of any conspicuous toxicity. Cytokine treatment without chemotherapy was completely ineffective. Liposome-based chemoimmunotherapy is a synergistic and highly efficacious approach to eradicate metastatic and regionally spread tumors.