Patent Evaluation: Novel Self-Assembling Proteins

Summary

Novelty: A novel gene construct has been generated which is designed for the co-expression, in a host cell, of a self-assembling protein moiety which will form a protein core and a membrane-bound protein. The nascent protein core will bud off from the cell, in the process acquiring a membrane envelope with which the membrane-bound protein component will be associated.

Biology: In one example, the HIV gag 1 coding sequence was excized from an existing plasmid vector as a BamH1 cassette and cloned into pAcRP23. This baculovirus expression vector consisted of the sequence encoding the polyhedrin gene of the Autographa californica nuclear polyhedrosis virus ligated into a high copy number bacterial plasmid and modified to generate a unique cloning site. On introduction of the recombinant plasmid into Spodoptera frugiperda, the p55^gag polypeptide was found to accumulate in the culture supernatant, indicating that the recombinant protein is released from the cell. Electron microscopy indicated that the p55^gag polypeptide was associated with particles which budded off the cell surface. Cells expressing the gag sequence were co-infected with a recombinant baculovirus expressing the haemagglutinin gene from influenza virus. On co-expression of the gag the haemagglutinin genes, extracellular particles were obtained which encapsulated the gag polypeptide while having haemagglutinin associated with the particle surface.