Simultaneous expression of recombinant baculovirus-encoded chicken anaemia virus (CAV) proteins VP1 and VP2 is required for formation of the CAV-specific neutralizing epitope.

Chicken anaemia virus (CAV) expresses three proteins, VP1, VP2 and VP3, but its capsid contains only the VP1 protein. In this paper, we report that for production of the neutralizing epitope, co-synthesis of (recombinant) VP1 and VP2 has to take place. We show via immunofluorescence that recombinant-baculovirus-infected Sf9 cells synthesizing VP1 (or VP2) alone react very poorly with CAV-specific neutralizing antibodies. In contrast, Sf9 cells co-infected with VP1- and VP2-recombinant baculoviruses, or infected with a single recombinant baculovirus co-expressing both VP1 and VP2, react strongly with the neutralizing antibodies. Furthermore, immunoprecipitation assays show that VP1 and VP2 interact directly with each other, which indicates that the non-structural protein VP2 might act as a scaffold protein in virion assembly. Recombinant baculovirus expressing VP1 and VP2 is, therefore, a potential production system for a subunit vaccine against CAV infection.