DNA vaccination against hepatitis E virus infection in cynomolgus macaques

Background : The feasibility of DNA vaccination against hepatitis E in non‐human primates has not been evaluated. In the present study a full‐length hepatitis E virus (HEV) open reading frame (ORF)2 (Burmese strain) was assembled, cloned, and used for genetic immunization of cynomolgus macaques (cynos), which were subsequently challenged with a heterologous HEV strain (Mexico). Methods : Four cynos were vaccinated intramuscularly with the HEV ORF2 DNA cassette and one animal was vaccinated with a mock DNA construct. Results : Following vaccination anti‐HEV antibodies were detected in the four HEV‐DNA‐vaccinated cynos, but not in the control animal. When challenged, two of the four HEV‐DNA‐vaccinated cynos were protected against HEV infection and had no elevated alanine aminotransferase activity, viremia, or fecal shedding. The two other DNA‐vaccinated animals developed HEV infection and disease. Conclusion : These findings demonstrate the feasibility of DNA vaccination for the protection of HEV infection and warrant further studies to explore routes other than intramuscular for induction of a stronger and efficacious immune response. © 2002 Blackwell Publishing Asia Pty Ltd