Clinical assessment of a recombinant simian adenovirus ChAd63: a potent new vaccine vector.

Journal article

BACKGROUND: Vaccine development in human Plasmodium falciparum malaria has been hampered by the exceptionally high levels of CD8(+) T cells required for efficacy. Use of potently immunogenic human adenoviruses as vaccine vectors could overcome this problem, but these are limited by preexisting immunity to human adenoviruses. METHODS: From 2007 to 2010, we undertook a phase I dose and route finding study of a new malaria vaccine, a replication-incompetent chimpanzee adenovirus 63 (ChAd63) encoding the preerythrocytic insert multiple epitope thrombospondin-related adhesion protein (ME-TRAP; n = 54 vaccinees) administered alone (n = 28) or with a modified vaccinia virus Ankara (MVA) ME-TRAP booster immunization 8 weeks later (n = 26). We observed an excellent safety profile. High levels of TRAP antigen-specific CD8(+) and CD4(+) T cells, as detected by interferon γ enzyme-linked immunospot assay and flow cytometry, were induced by intramuscular ChAd63 ME-TRAP immunization at doses of 5 × 10(10) viral particles and above. Subsequent administration of MVA ME-TRAP boosted responses to exceptionally high levels, and responses were maintained for up to 30 months postvaccination. CONCLUSIONS: The ChAd63 chimpanzee adenovirus vector appears safe and highly immunogenic, providing a viable alternative to human adenoviruses as vaccine vectors for human use. CLINICAL TRIALS REGISTRATION: NCT00890019.

Authors: O'Hara, G; Duncan, C; Ewer, K; Collins, K; Elias, S

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Journal of infectious diseases
• Volume: 205
• Issue: 5
• Pages: 772-781
• Publication date: 2012-03-01
• DOI: 10.1093/infdis/jir850
• EISSN: 1537-6613
• ISSN: 0022-1899
• Language: English
• Keywords: Tumor Necrosis Factor-alpha; CD8-Positive T-Lymphocytes; Epitopes; Animals; Malaria Vaccines; Vaccines, DNA; Flow Cytometry; Interferon-gamma; Protozoan Proteins; Humans; CD4-Positive T-Lymphocytes; Antibodies, Neutralizing; Adenoviruses, Simian; Malaria, Falciparum; Interleukin-2