Ebola DNA vaccine shows promise

Vical Incorporated has announced that an Ebola vaccine candidate administered using Vical's proprietary DNA delivery technology was safe and well tolerated, and produced both antibody and T-cell Ebola-specific responses in all healthy volunteers who received the full 3 doses of vaccine.

The Phase 1, randomized, placebo-controlled, dose-escalation study, the first human trial for any Ebola vaccine, was sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), and conducted at the NIH Clinical Center. The data were presented at the American Society for Microbiology (ASM) 2006 Biodefense Research Meeting in Washington, D.C., by Julie E. Martin, D.O., a trial investigator and research scientist at NIAID's Dale and Betty Bumpers Vaccine Research Center (VRC), which developed the vaccine. The DNA vaccine used in the Phase 1 trial incorporates genetic material encoding core and surface proteins from two strains of Ebola. Vical has secured a nonexclusive license from the NIH to proprietary gene sequences used in the vaccine.

"The high rates of immune responses at all dose levels in this initial human Ebola vaccine study support continued development of this vaccine and further evaluation of our technology for potential additional biodefense and emerging disease applications," said David C. Kaslow, M.D., Vical's Chief Scientific Officer, "particularly where antibody responses may be protective. Our processes allow rapid development and manufacturing of vaccines without handling potentially dangerous pathogens."

The vaccine used in the Phase 1 trial vaccine included three plasmids (closed loops of DNA), one each encoding the surface glycoprotein (GP) from the Zaire strain of Ebola, GP from the Sudan/Gulu strain, and the internal nucleoprotein (NP) from the Zaire strain. Subjects received three doses of vaccine or placebo at one-month intervals via intramuscular needleless injection. Three cohorts tested progressively higher doses of the vaccine at 2 mg (5 subjects), 4 mg (8 subjects), or 8 mg (8 subjects -- with 6 receiving the full three doses). Each cohort included two additional subjects who received placebo instead of active vaccine.

The vaccine was well tolerated, with no severe adverse reactions to the vaccine reported at any of the doses tested. Ebola-specific antibody responses against at least one of the encoded antigens were detected in all vaccine recipients. GP-specific antibody and T-cell responses were detected in all recipients who received the full three doses at all dose levels.