Release kinetics and immunogenicity of parvovirus microencapsulated in PLA/PLGA microspheres

The aim of this work was to examine the immunogenicity of microencapsulated inactivated duck parvovirus in Muscovy duck (Cairina moschata) and goose. Inactivated duck parvovirus suspension was microencapsulated into 14-17 kDa poly(lactide) (PLA) and poly(lactide-co-glycolide) (PLGA50:50H) by coacerv ation. The in vitro antigen release from individual and mixed PLA and PLGA5 0:50H microspheres (MS) was biphasic with an initial lag-phase of approx. 1 0 days followed by a relatively constant release over additional 12 days. B y varying the composition of PLA + PLGA50:50H MS mixtures from 3 + 1 to 1 3. the release kinetics could be altered and controlled efficiently. The a ntigen-loaded MS were injected subcutaneously into ducks. The immune respon se, expressed as virus neutralisation (VN) titres, after single administrat ion of MS was modest, i.e. below 200 over the 6 weeks tested, unless the an imals were pre-immunised 3 weeks before injecting the MS. The weak immune r esponse was attributed to the low dose injected and inappropriate antigen r elease kinetics. With pre-immunised animals, however, the results were enco uraging and showed that the encapsulated parvovirus was immunogenic. (C) 20 01 Elsevier Science B.V. All rights reserved.