BACKGROUNDTo study to immunogenicity of recombinant HEV ORF2 protein expressed in pichia pastoris.

METHODSBALB/c mice were immunized with the recombinant HEV ORF2 protein. The ability of antiserum to bind HEV was tested using affinity-capture reverse transcription polymerase chain reaction (RT-PCR). Moreover, the recombinant protein was used to immunize BALB/c mice by different routes with different adjuvants. Serum conversion rate of anti-HEV antibody and the ELISA titer were detected.

RESULTSThe antiserum could capture native HEV for RT-PCR. As to the immunization effect, the immune response by intramuscular route was better than that of the intraperitoneal route. The protein with alum and CpG adjuvant could elicits more significant immune responses than using the alum adjuvant alone. The best way was to immunize with the protein with alum and CpG adjuvant by intramuscular route with a boosted injection on the 4th week after the first immunization. The ED50 was 0.023 microgram. This is the first report that the antibody elicited by recombinant HEV ORF2 protein expressed in pichia pastoris recognizes native HEV. High immunogenicity of this kind of ORF2 was also demonstrated by inducing strong immune response in mice with good ED50 result.

CONCLUSIONSThe high immunogenicity of this kind of HEV ORF2 may make a foundation for the development of new type of hepatitis E vaccine.