A Phase 1 clinical trial of Hantaan virus and Puumala virus M-segment DNA vaccines for haemorrhagic fever with renal syndrome delivered by intramuscular electroporation.

Haemorrhagic fever with renal syndrome (HFRS) is endemic in Asia, Europe and Scandinavia, and is caused by infection with the hantaviruses Hantaan (HTNV), Seoul (SEOV), Puumala (PUUV), or Dobrava (DOBV) viruses. We developed candidate DNA vaccines for HFRS expressing the Gn and Gc genes of HTNV or PUUV and evaluated them in an open-label, single-centre Phase 1 study. Three groups of nine participants each were vaccinated on days 0, 28 and 56 with the DNA vaccines for HTNV, PUUV, or a mixture of both vaccines using the Ichor Medical Systems TriGrid Intramuscular Delivery System. All vaccinations consisted of a total dose of 2.0 mg DNA in an injected volume of 1 mL saline. For the combined vaccine, the mixture contained equal amounts (1.0 mg) of each DNA vaccine. There were no study-related serious adverse events. Neutralizing antibody responses were measured by a plaque reduction neutralization test. Neutralizing antibody responses were detected in five of nine and seven of nine individuals who completed all three vaccinations with the HTNV or PUUV DNA vaccines, respectively. In the combined vaccine group, seven of the nine volunteers receiving all three vaccinations developed neutralizing antibodies to PUUV. The three strongest responders to the PUUV vaccine also had strong neutralizing antibody responses to HTNV. These results demonstrate that the HTNV and PUUV DNA vaccines delivered by electroporation separately or as a mixture are safe. In addition, both vaccines were immunogenic, although when mixed together, more participants responded to the PUUV than to the HTNV DNA vaccine.