Poster Presentation 9th Australasian Virology Society Meeting 2017

Characterisation of E2-DHBVS Virus-like Particles as a Hepatitis C Virus Vaccine Candidate (#169)

Joey McGregor 1 2 , Rob J Center 1 2 , Patricia Vietheer 1 3 , Josh Hardy 3 , Michael Piontek 4 , Fasseli Coulibaly 3 , Pantelis Poumborious 1 3 , Heidi E Drummer 1 2 3
  1. Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia
  2. Department of Microbiology and Immunology at the Peter Doherty Institute, The University of Melbourne, Melbourne, Australia
  3. Department of Microbiology, Monash University, Clayton, Australia
  4. ARTES Biotechnology GmBH, Langenfeld, Germany

Background: Hepatitis C virus infects more than 70 million people world-wide and causes ~500,000 deaths annually. Currently, there is no HCV vaccine available. Research highlights that a prophylactic vaccine for HCV should induce broadly neutralizing antibodies active against all 7 antigenically diverse genotypes. However, the major challenge to developing a successful vaccine is the virus’ ability to rapidly mutate and immune evasion strategies that suppress the production of cross protective antibodies. It has been shown that a soluble recombinant E2 immunogen that lacks three variable regions (D123) is able to elicit a higher titre of broadly neutralizing antibodies in comparison to the parental wild-type form (E2RBD). This study investigates whether E2 could be presented within a virus-like-particle to produce a low cost, highly immunogenic platform for delivery of the E2 antigens.

Methods: E2RBD, E2D123 and two modified forms of E2 in which 7 cysteine residues were converted to alanine (E2RBDAla7 and D123Ala7) were genetically fused to the Duck Hepatitis B Virus S (DHBV-S) antigen. VLPs were produced by co-transfecting HEK293F cells with E2-DHBV-S constructs together with DHBV-S. VLPs were isolated by ultracentrifugation and density gradient separation. Immunoblotting determined the expression of E2 and S within VLPs and Electron microscopy was used to confirm particle formation. ELISA confirmed surface presentation of E2 and characterised the antigenicity of VLPs towards neutralising and non-neutralising E2-specific antibodies in comparison to the soluble antigens.

Results: The form of E2 antigen was found to significantly influence VLP formation. Electron microscopy determined the formation of intact VLPs. Antigenicity studies revealed that VLPs were recognised by human neutralizing monoclonal antibodies to four different antigenic sites suggesting that the conformation of the E2 receptor binding domain was intact.

Conclusion: VLPs presenting E2 represent a promising new low cost HCV vaccine candidate and will now be assessed in immunogenicity trials.