Synthesis of PE liposome for the application as vaccine adjuvants and construction of mathematical model for PCV2 infection and vaccination with adjuvants

Abstract

In this study, a method that produces PE liposomes with controlled size was developed by adopting microfluidic hydrodynamic flow focusing device. Average diameter of produced PE liposome was controlled by adjusting the flow rate ratio (FRR). Produced PE liposomes were used as vaccine adjuvants to amplify the vaccine efficacy for porcine circovirus type 2 (PCV2), which caused postweaning multisystemic wasting syndrome (PMWS) in pigs. Experimental data were used to construct a mathematical model to explain immune responses to PCV2 infection and vaccination.Firstly, process for the production of PE liposomes with controlled size was developed by adopting microfluidic hydrodynamic flow focusing device. Microfluidic device was fabricated using conventional photolithography and soft lithography based on polydimethylsiloxane (PDMS) molding technique. Soft lithography was adopted for simple and cost-effective fabrication of devices. In order to achieve flow stability in device, various designs were investigated, and 30°-angled or curved intersecting devices satisfied the flow stability with FRR up to 50. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE), dihexadecyl phosphate (DCP), and cholesterol (Chol) were used to produce liposome. Effect of each component on the quality of produced liposome was investigated by bulk experiment, and the mixture of DMPE, DCP, and Chol with molar ratio of 5:1:4 was selected for microfluidic liposome production. Lipid stream, lipid solution in isopropyl alcohol (IPA), was focused by adjacent aqueous sheath flow. Lipid molecules were mixed with surrounding water molecules. Formation of liposome occurred due to the self-assembly of lipid molecules in insoluble solvent. Size distribution and morphologies of produced PE liposomes were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The average size of produced PE liposomes could be controlled by adjusting FRR. Width of focused ...