Scientists Report on Trial of Early-Generation Ebola, Marburg Vaccine Candidates

Results of an early-stage clinical trial of two experimental vaccines against Ebola and Marburg viruses -- the first to be completed in an African country -- showed that they were safe and induced immune responses in healthy Ugandan adult volunteers. Developed by researchers at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, the experimental vaccines (called DNA vaccines) were predecessors to a next-generation candidate vaccine, called the NIAID/GSK Ebola vaccine, which is currently in clinical development. The NIAID/GSK vaccine incorporates Ebola gene segments into a carrier derived from a chimpanzee adenovirus. It is being tested in several Phase 1 clinical trials around the world, with larger trials planned for early 2015.

Overall, the immune responses in the Ugandan volunteers were similar to those reported in a trial of these same DNA vaccines that enrolled participants in the United States in 2008. This is important, the researchers noted, because geographically disparate populations can sometimes have differing immune responses to the same vaccine. That North American and East African volunteers responded similarly to the experimental Ebola and Marburg vaccines is encouraging, they added, and information gained from this trial contributed to accelerated development of the current NIAID/GSK Ebola candidate vaccine.

The Ugandan trial began enrolling volunteers at Makerere University Walter Reed Project, Kampala, in 2009. A total of 108 people enrolled in the trial; 18 people received placebo injections and three groups (30 volunteers in each) received Ebola vaccine, Marburg vaccine or both. Participants received three injections spaced over eight weeks and all volunteers were followed for two years after enrollment. Antibody responses in all vaccine groups peaked at four weeks after the third inoculation. Antibodies against the Zaire stain of Ebola virus, the strain causing the current Ebola outbreak in West Africa, were seen in 17 volunteers who received the Ebola vaccine alone and in 14 of those who received both vaccines. Researchers also detected responses of the T-cell arm of the immune system in many of the volunteers. T-cells are believed to play an important role in protection against Ebola infection. Both vaccines were well-tolerated.

Reference: Kibuuka H, et al. Safety and immunogenicity of Ebola virus and Marburg virus glycoprotein DNA vaccines assessed separately and concomitantly healthy Ugandan adults: a phase 1B randomised, double-blind, placebo-controlled clinical trial. The Lancet DOI: 10.1016/S0140-6736(14)62385-0 (2014).

Source: National Institutes of Health (NIH)