Comparison of poly(acryl starch) and poly(lactide-co-glycolide) microspheres as drug delivery system for a rotavirus vaccine.

Drug delivery systems allowing controlled release of antigen are of particular interest in the development of vaccines. We have compared poly(acrylic starch) microspheres (PAS) and poly(lactide-co-glycolide) microspheres (PLG) as drug delivery systems for a rotavirus vaccine. The polymers are both biodegradable but have different degradation mechanisms and antigen release profiles. PAS are enzymatically degraded and have a continuous fast antigen release rate compared to the hydrolytically degraded PLG which release the incorporated antigen in a pulsatile manner. In this study mice were immunised intramuscularly and orally on three occasions with formalin-inactivated rotavirus (FRRV) incorporated in PAS and PLG and with FFRV alone. Serum and faeces samples were collected and analysed by ELISA for rotavirus specific IgG and IgA antibodies. A neutralising assay was also conducted on both serum and faeces antibodies. The two different polymer drug delivery systems induced different immune responses depending on administration route. PAS elicited significant antibody levels and neutralising effect after oral administration while PLG showed high antibody levels after intramuscular administration. The immune response appears to be dependent on the differences in antigen release and degradation mechanism for the two polymer systems.     

Interferon-γ in Starch Microparticles: Nitric Oxide-Generating Activity in Vitro and Antileishmanial Effect in Mice

Recombinant mouse interferon- (mu IFN-) was covalently coupled to polyacryl starch microparticles, a lysosomotropic drug carrier. The microparticle-bound mu IFN- was found to activate cultured macrophages for nitrite production and had an anti-leishmanial effect in mice. Low doses of mu IFN-, which had no effect in the free form, when bound to microparticles significantly reduced the load of Leishmania donovani in infected mice. Further, inducement of nitrite production in cultured macrophages by microparticle-bound mu IFN- required intact cell membrane receptors.     

Extracellular antigens from Salmonella enteritidis induce effective immune response in mice after oral vaccination

We have studied polyacryl starch microparticles as an adjuvant in oral vaccination in mice. Secreted antigens from Salmonella enterica serovar Enteritidis were administered covalently conjugated to microparticles, or as free antigens, orally or intramuscularly and evaluated for their immunogenicity and ability to elicit protective immune response against an oral challenge with live serovar Enteritidis. The highest immunoglobulin M (IgM)-plus-IgG titers were obtained in the groups immunized with antigen-conjugated microparticles. The subclass profile switched to a stronger Th1 influence in the oral groups after booster, while the intramuscular group showed a constant Th1/Th2 profile. A strong specific IgA response was seen in feces in the oral groups, which was further confirmed in an enzyme-linked immunospot assay. The delayed-type hypersensitivity test, as a measure of the cellular response, showed a significant increase in ear thickness in all the immunized groups, except for the group that received free antigen orally, compared to the nonimmunized group. The cytokines released from in vitro-stimulated spleens showed a strong gamma interferon response in all immunized groups. A significant reduction in CFU in liver and spleen was seen in the orally immunized groups compared to the nonimmunized group after oral challenge with serovar Enteritidis. Western blotting analysis with both sera and feces revealed that antibodies against three bands, 53, 56, and 60 kDa, dominated the oral groups, and an electrospray-mass spectroscopy analysis of these bands showed amino acid sequences coinciding with those of phase-1 flagellin and hook-associated protein 2.     

Biodegradable microspheres. XIII: Immune response to the DNP hapten conjugated to polyacryl starch microparticles

Polyacryl starch microparticles are being investigated for use as drug carriers, especially in the treatment of intracellular parasitic diseases. The purpose of this work was to investigate the possible immune response to drugs coupled to the microparticles, using the dinitrophenyl group (DNP) as a model. The humoral immunogenicity of DNP hapten-conjugated polyacryl starch microparticles has been examined in mice. Microparticle:hapten complexes with different biodegradability were tested, as well as different dosages and routes of administration. Two DNP derivatives, Lys(DNP) and Leu-Ala-Lys(DNP), were coupled to microparticles. It was shown that Lys(DNP) was released from the particles by lysosomal enzymes only from the conjugate with the tripeptide DNP derivative. The DNP conjugated to the particles via the biodegradable Leu-Ala-Lys arm induced only a weak immune response without memory. No response was detected after injection of the Lys(DNP) microparticles. Thus, there should be no major immunological obstacles in using drug:microparticle complexes in the treatment of, for example, parasitic diseases.