A novel method for recombinant mammalian‐expressed S‐<scp>HBsAg virus‐like particle</scp> production for assembly status analysis and improved anti‐<scp>HBs</scp> serology

The Hepatitis B surface antigen (HBsAg) as the only lipid-associated envelope protein of the Hepatitis B virus (HBV) acts as cellular attachment and entry mediator of HBV making it the main target of neutralizing antibodies to provide HBV immunity after infection or vaccination. Despite its central role in inducing protective immunity, there is however a surprising lack of comparative studies examining different HBsAgs and their ability to detect anti-HBs antibodies. On the contrary, various time-consuming complex HBsAg production protocols have been established, which result in structurally and functionally insufficiently characterized HBsAg. Here, we present an easy-to-perform, streamlined and robust method for recombinant S-HBsAg virus-like particle (VLP) production by transient expression in mammalian cells and purification from the cell lysate with the aim of displaying uniform antigenic epitopes on the surface to improve serological detection of anti-HBs antibodies. We not only compare assembly status and particle composition by transmission electron microscopy and mass photometry of our S-HBsAg and of commonly used HBsAg reference samples, but also assess their antigenic quality and functional suitability for anti-HBs antibody detection to identify the best performing sample for serological screenings. While we found that serum-isolated and recombinant HBsAg VLPs are assembled differently, our S-HBsAg VLPs detected anti-HBs antibodies with the highest sensitivity and specificity in multiplex serology when compared to yeast or serum HBsAg making it the most suitable antigen for analysis of HBV immunity through anti-HBs serostatus.