摘要：The Norovirus (NoV) P domain, with three surface loops for foreign antigen insertion, has been
demonstrated as an excellent platform for antigen presentation and novel vaccine development. The P
domain alone can self-assemble into a P dimer, 12-mer small particle or 24-mer P particle, and vaccines
based on those particles may elicit different levels of immunogenicity. Currently, P particles are generally
produced in soluble expression systems in Escherichia coli, mainly in the 24-mer form. However, the low
yield of the soluble protein has hindered further clinical applications of P particle-based protein vaccines.
In this study, we inserted the Alzheimer's disease (AD) immunogen A b 1-6 into the three loops of the P
particle to generate an AD protein vaccine. To increase the yield of this chimeric protein, we tested the
generation of proteins in a soluble expression system and an inclusion body expression system sepa-
rately in E. coli. The result showed that the inclusion body expression system could greatly enhance the
product yield of the chimeric protein compared with the soluble expression system. The refolded protein
from the inclusion bodies was mainly in the 12-mer form, while the protein generated from the soluble
supernatant was mainly in the 24-mer form. Moreover, the immunogenicity of soluble proteins was
significantly stronger than that of the refolded proteins. Thus, comparisons between the two expression
methods suggested that the soluble expression system generated chimeric P particles with better
immunogenicity, while inclusion body expression system yielded more P particle proteins.
