The present invention relates to methods and means for the production of alginate/chitosan acid-resistant macrobeads comprising alginate/chitosan nanoparticles, wherein the nanoparticles comprise a bioactive agent, wherein the bioactive agent is associated via physicochemical interaction with a polymer. The invention further relates to nanoparticles and/or macrobeads obtained by methods of the invention and such nanoparticles and/or macrobeads for use in eliciting an immune response in an animal. Also encompassed by the invention is the use of a porcine epidemic diarrhea virus (PEDV) antigen as defined herein for producing a nanoparticle or acid-resistant macrobeads and a vaccine comprising such an antigen.本發明涉及用於產生包含藻酸鹽/殼聚醣奈米顆粒的藻酸鹽/殼聚醣耐酸大珠粒之方法及手段，其中該奈米顆粒包含生物活性劑，其中該生物活性劑經由物理化學交互作用而與聚合物結合。本發明進一步涉及透過本發明之方法獲得之奈米顆粒及/或大珠粒，以及這樣的奈米顆粒及/或大珠粒用於在動物中引發免疫反應。本發明還包括如本文所定義之豬流行性下痢病毒(porcine epidemic diarrhea virus，PEDV)抗原用於產生奈米顆粒或耐酸大珠粒以及一種包含此抗原的疫苗之用途。
