Synthesis of immunogenic hepatitis A virus particles by recombinant baculoviruses

Recombinant baculoviruses were constructed which contained the hepatitis A virus (HAV) open reading frame (ORF) under the control of the polyhedrin promoter. Northern blot analysis with an HAV-specific oligonucleotide probe demonstrated a single transcript large enough to include the HAV ORF in Spodoptera frugiperda cells infected with these recombinants. Immunoblots revealed a 220 kDa protein representing the HAV polyprotein. In addition, proteins which co-migrated with HAV capsid proteins, and several proteins of intermediate size were present, consistent with processing intermediates. HAV antigen was present in cells infected with the recombinant baculoviruses when assessed by solid-phase radioimmunoassay. This HAV antigen had a buoyant density in caesium chloride gradients similar to HAV empty capsids, and elicited HAV neutralizing antibodies in mice.