PPIB and hepatitis A virus infection: HBeAg is not required for virion production, but it is involved in developing immune tolerance and chronic infection.24 For the anti-hepatitis B antibody-binding fragment (Fab) e6, two different X-ray structures are available in the Protein Data Bank (PDB),25 crystallized in complex with the antigen (3V6Z) and without the antigen (3V6F).