Adjuvancy enhancement of muramyl dipeptide by modulating its release from a physicochemically modified matrix of ovalbumin microspheres I. In vitro characterization

The weak immunogenicity of subunit vaccines has necessitated research into the development of novel adjuvants and methods to enhance the adjuvancy ass ociated with vaccine delivery systems. The purpose of the present study was to modulate the release of muramyl dipeptide (MDP) from a physicochemicall y modified matrix of ovalbumin microspheres (OVA-MSs), A two-component MS v accine delivery system was fabricated, which utilized OVA as the antigen an d delivery matrix, and MDP as the adjuvant. The MSs were prepared from OVA using a water/oil emulsion method, followed by suspension cross-linking usi ng glutaraldehyde. The MS matrix was modified with respect to the degree of cross-linking by varying the concentration of glutaraldehyde and matrix de nsity, a function of disulfide-bond formation. The modifications in the MS matrix were characterized using SDS-PAGE, scanning electron microscopy, dif ferential scanning calorimetry, and thin layer wicking (TLW). The in vitro release of MDP and OVA from the various preparations of OVA-MSs exhibited t riphasic and biphasic profiles, respectively. The degree of cross-linking a nd the matrix density were found to be significant physicochemical paramete rs that affected the release profiles of MDP and OVA through two mechanisms : controlled surface erosion and bulk degradation of the MSs. (C) 2000 Else vier Science B.V. All rights reserved.