Affinity-purified sHBsAg-based virus-like particles as a platform for foreign mRNA binding

Virus-like particles (VLPs) have long been utilized as immunogens to prevent infectious diseases. Particles derived from the small surface proteins of the hepatitis B virus (sHBsAg) can self-assemble into small, highly immunogenic structures and have been used in human vaccination since the 1980s. Various chimeric sHBsAg VLPs retain their self-assembly ability, even when significant sequence alterations, such as fusions or substitutions, are introduced. This makes them an attractive experimental model and vaccine platform for delivering and presenting foreign epitopes. In the present study, motifs from the hepatitis B virus (HBV) core protein (HBcAg) were introduced into the cytosolic loops of sHBsAg to explore whether these VLPs could acquire the ability to pack mRNA. With one exception, the introduced changes for mRNA binding did not affect ability for self-assemble. A Twin-Strep-tag was added to the N-terminus for more efficient and specific purification. With the exception of one modification, the changes made to allow for mRNA binding did not affect the self-assembly capability of sHBsAg. The recombinant proteins successfully bound mRNAs from various sources.