Presentation of human immunodeficiency virus epitopes by chimeric core particles hepatitis B virus

Abstract

We have constructed a synthetic open reading frame based on amino acid sequences from two conserved regions of the HIV-1 p120 env protein, and from a predicted antigenic region of the p17 gag protein. We have synthesized these genes by using the preferred codon usage for the polyhedrin gene of the baculovirus AcNPV. This synthetic gene was fused either at the 5'- or at the 3'-terminus of the human hepatitis B core antigen (HBcAg) gene, and the fused genes were expressed in Spodoptera frugiperda cells using recombinant baculovirus. Both fused genes were capable of directing the synthesis of chimeric 27-nm spherical particles. Electron microscopic analyses revealed morphologies distinct from that of HBcAg particles. Antisera directed against either chimeric particles could immunoprecipitate the non-glycosylated form of HIV-1 gp120. In contrast, antisera against only the N-terminal fusion, but not the C-terminal fusion particles, recognized HIV-1 p17. Furthermore, antisera raised against non-glycosylated gp120 immunoprecipitated both types of chimeric particles. Our results demonstrate that the HIV-1 epitopes on the chimeric HBcAg-HIV particles are properly recognized as authentic HIV antigen.