Ebola hemorrhagic fever is a severe and often deadly illness leading to bleeding from body orifices and the skin. The disease can be passed to humans from infected nonhuman primates (NHP), close contact with infected human bodily fluids, or infected needles.
To combat this extremely deadly disease, investigators at NIAID have been evaluating vaccines against the Ebola virus. Earlier studies in NHP revealed that an experimental Ebola vaccine could trigger a potent immune response. This response included both the activation of virus-fighting immune cells known as T cells and the production of antibodies against the virus. However, it remained unclear which type of immune response was responsible for the protective immunity—the so-called cellular (T-cell) response or the antibody response.
To answer this question, the researchers vaccinated cynomolgus macaques, a commonly used NHP species, with a candidate Ebola vaccine. They then transferred antibodies that were produced by vaccinated macaques to unvaccinated monkeys. These antibodies failed to protect the monkeys following exposure to the Ebola virus, strongly suggesting that the cellular (T-cell) immune response conferred protection.
When the researchers experimentally eliminated T cells from the vaccinated macaques, two monkeys did succumb to Ebola disease, suggesting that T cells may play a role in protection. They determined that this protection was due to a type of T cell known as CD8 T cells, which are crucial for eliminating virally infected cells. With this knowledge in hand, the next generation of experimental Ebola vaccines should be designed to trigger strong CD8 T-cell responses, as this appears to be the main avenue of protection against disease.
Reference: Sullivan NJ, Hensley L, Asiedu C, Geisbert TW, Stanley D, Johnson J, Honko A, Olinger G, Bailey M, Geisbert JB, Reimann KA, Bao S, Rao S, Roederer M, Jahrling PB, Koup RA, Nabel GJ. CD8+ cellular immunity mediates rAd5 vaccine protection against Ebola virus infection of nonhuman primates. Nat Med. 2011 Aug 21;17(9):1128-31.
Last Updated January 07, 2013
Last Reviewed January 07, 2013