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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.

Original publication

DOI

10.1093/infdis/jir850

Type

Journal article

Journal

J Infect Dis

Publication Date

01/03/2012

Volume

205

Pages

772 - 781

Keywords

Adenoviruses, Simian, Animals, Antibodies, Neutralizing, CD4-Positive T-Lymphocytes, CD8-Positive T-Lymphocytes, Epitopes, Flow Cytometry, Humans, Interferon-gamma, Interleukin-2, Malaria Vaccines, Malaria, Falciparum, Protozoan Proteins, Tumor Necrosis Factor-alpha, Vaccines, DNA