Ebola Vaccine Triggers Human T-Cell Responses Against Bundibugyo Strain
Scientists have found that a single dose of the approved VSV-EBOV vaccine triggers T-cell immune responses against the Bundibugyo ebolavirus, according to a study published in The Lancet Infectious Diseases and reported by lifePR. The current outbreak of the Bundibugyo virus in the Democratic Republic of Congo stands as the second-largest Ebola outbreak globally, logging more than 6,000 confirmed cases and a 48 percent mortality rate. No approved vaccine specifically targets the Bundibugyo strain at present. The highly effective vaccine against the Ebola virus is known as rVSVΔG-ZEBOV-GP, or Ervebo, and is manufactured by Merck Sharp & Dohme. Furthermore, the VSV-EBOV vaccine has shown partial cross-protection against BDBV in nonhuman primates, and it induces BDBV-reactive antibodies in vaccinated individuals.
Mapping Cross-Reactive T-Cell Immunity Across Diverse Strains
To determine how immune cells interact with different ebolaviruses, a research team from the German Center for Infection Research analyzed T-cell responses against the Zaire, Bundibugyo, and Sudan viruses in vaccinated individuals. As lifePR reported, the study was led by Dr. Leonie Mayer and Prof. Marylyn Addo from the University Hospital Hamburg-Eppendorf alongside Prof. Christof Geldmacher and Dr. Rolanda Londt from the LMU University Hospital Munich. Using multiple sequence alignments, the team identified highly conserved amino acid sequences across the glycoproteins of the three pathogens. EBOV and BDBV share a 66.3 percent amino acid identity, whereas EBOV and SUDV share 56.3 percent. The study was published in The Lancet Infectious Diseases under the title „The dynamic triad: Immunogenicity, cross-reactivity and protection”, with authors listed as Leonie Mayer, Rolanda Londt, Dirk Busch, Maike Eff, Rabea V. Schürmann, and others.
Evaluating Post-Vaccination Immune Responses in Trial Participants
Twenty vaccinated volunteers were examined 28 days after receiving the VSV-EBOV vaccine to measure cross-reactive T-cell activity. Among them, 16 participants developed glycoprotein-specific T-cell responses against the Zaire virus, while 13 showed reactivity to the Bundibugyo strain and seven reacted to the Sudan strain, according to findings cited by lifePR. Most individuals who developed Zaire-reactive T cells also carried Bundibugyo-reactive T cells. Dr. Leonie Mayer stated that the findings provide initial evidence that the vaccine induces BDBV-cross-reactive T-cell responses in humans, though the precise clinical significance and protection levels remain undetermined.
While preclinical studies in nonhuman primates indicate that T-cell responses are necessary for vaccine-mediated protection, the exact extent of protection in humans remains unclear. Prof. Christof Geldmacher noted that despite the small sample size of the study, the absence of a dedicated Bundibugyo vaccine supports evaluating the existing EBOV vaccine within clinical trials. Researchers plan to further analyze how these cross-reactive T-cell populations function during potential exposures to control viral replication and prevent severe disease.
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