Characterization and administration of cyclosporine liposomes as a small-particle aerosol.

Systemically administered CsA has not consistently suppressed the pulmonary immunoreactivity that leads to rejection in lung transplant patients. Pulmonary T cells from patients given CsA systemically still retain their immunoreactivity, which can be suppressed with added CsA. Direct application of CsA by aerosol to the respiratory epithelium should achieve high lung concentrations with minimum systemic effects. In the present study, CsA was most efficiently incorporated into liposomes composed of egg yolk phosphatidylcholine at a molar ratio of CsA to egg yolk phosphatidylcholine of 1:20. These CsA liposomes retained their biological activity and were as effective as free CsA in the suppression of anti-CD3-stimulated [3H]thymidine incorporation by mouse spleen cells. The generation of a small-particle aerosol of CsA liposomes had no effect on this biological activity. CsA liposome aerosol particles have a mass median aerodynamic diameter of 2 microns, which allows for distribution of drug throughout the respiratory tract. Quantitation of CsA in the lungs and blood of mice exposed to CsA liposome aerosols for 4 days showed that as little as 15 min daily (0.11 mg/kg/day) was sufficient to achieve an estimated concentration of CsA in respiratory secretions of 6 micrograms/ml without detectable blood levels. Thus, CsA liposomes can be produced and aerosolized that achieve pulmonary concentrations with sufficient immunosuppressive activity to be effective in the treatment of lung diseases.

Universal vaccine carrier. Liposomes that provide T-dependent help to weak antigens.

The design of a thymus-dependent synthetic vaccine that will provide a universal T cell epitope for B cell epitopes is described in this study. Simultaneous incorporation into liposomes of both a peptide recognized by Th lymphocytes and a lipophilic hapten and the IgG antibody responses to this hapten were assessed in outbred mice. DNP-aminocaproyl phosphatidylethanolamine (DNP-CapPE) is a well characterized T-independent hapten Ag. HA2 peptide derived from the hemagglutinin protein of influenza virus contains amino acid sequences recognized by Th and T cytotoxic lymphocytes. In addition, HA2 contains a sequence of hydrophobic amino acids near the carboxyl terminus, allowing its incorporation into liposomes. Results of immunization show that (i), when DNP-CapPE is carried by liposomes without the HA2 peptide, an IgM antibody response is induced, (ii) liposomes carrying both HA2 and DNP-CapPE elicit an IgG antibody response to DNP in a dose-dependent fashion for both HA2 and DNP, (iii) the liposomes must be processed intracellularly in order to elicit a response, (iv) the system leads to a memory response for DNP, and (v) all of the IgG subclasses are elicited. These data suggest that liposomes containing the HA2 peptide exhibit a T-dependent carrier effect for a T-independent Ag. The significance of these findings is discussed in conjunction with the characteristics of the liposome model used.

Serum IgG subclass antibody responses in children vaccinated with influenza virus antigens by live attenuated or inactivated vaccines.

To ascertain whether live attenuated or inactivated vaccines can be considered equivalent, we examined the primary antibody response of children following vaccination with influenza virus antigens in three different formulations. Nine children received cold recombinant vaccine (CRV) containing A/Korea/82 (H3N2) and A/Dunedin/83 (H1N1) variants. Eight of these children responded to HA of the H3N2 subtype and the major portion of the elicited antibody was in the IgG1 subclass. Antibody of low titer in the IgG2 and IgG3 subclasses was detected in two and six serum specimens, respectively. Six of the nine children administered with CRV responded to the H1 antigen and only IgG1 antibody was detected. Serum specimens from eight children less than one year of age (5 less than 6 months of age) who had developed an antibody response to trivalent inactivated vaccine (TIV) vaccination were examined. High levels of IgG1 antibody to purified H3 were detected in all eight children. Low titers of antibody in IgG2 and IgG3 subclasses were detected in two and five children, respectively. Antibody responses to purified H1 showed a similar subclass distribution. In order to examine secondary response, eight children primed by immunization with TIV vaccine were subsequently given a single booster dose of purified hemagglutinin (HA) conjugated to diphtheria toxoid (HA-D). In 6/8 specimens antibody rises were detected to purified H3 and H1 antigens. Prior to the HA-D immunization, low levels of HA specific IgG1 antibody were detected in all serum specimens and vaccine induced responses were primarily of the IgG1 subclass.(ABSTRACT TRUNCATED AT 250 WORDS)

Liposomes of enviroxime and phosphatidylcholine: definition of the drug-phospholipid interactions.

Interaction of the antiviral compound, enviroxime (E), with natural and synthetic phosphatidylcholines in organic and aqueous media was studied. Although insoluble in chloroform, E dissolved in chloroform solutions containing phosphatidylcholines. Solvation was directly related to the length of the fatty acid chains of the phospholipid. Proton spin resonance studies suggested an interaction of the fatty acid chains with the aromatic rings of E. Suspension of E-phosphatidylcholine mixtures of molar ratios up to 0.7:1.0 in aqueous media resulted in the formation of multilamellar liposomes. Liposomes containing E were more stable permeability barriers than those prepared with phospholipid alone, a property previously observed with cholesterol. Competition experiments suggested that E bound to the same sites in lipid bilayers as does cholesterol. These data indicate that E is incorporated into lipid bilayers of liposomes and that it alters the physical properties of the liposomes in a manner similar to that of cholesterol.