BACKGROUND: The merozoite surface protein (MSP)-1 of Plasmodium falciparum, the 
causative agent of malaria tropica, is considered to be a promising vaccine 
candidate. Although its stable cloning and expression has been difficult in the 
past, adenoviral vectors expressing the complex protein are described in the 
present study.
METHODS: Codon-optimized msp-1 was used to construct a set of first generation 
(ΔE1Ad) and high-capacity adenovirus (HC-Ad) vectors, and cellular and humoral 
immune responses induced by the vectors were characterized in detail in mice.
RESULTS: Generation of stable ΔE1Ad and HC-Ad vectors expressing full-length 
MSP-1 and their production to high vector titers was found to be feasible. 
Epitope identification and analysis of frequencies of specific CD8 T-cells 
revealed that MSP-1 expressing HC-Ad vectors induced higher frequencies of 
interferon-γ + CD8 T-cells than ΔE1 vectors. Irrespective of the vector format, 
higher titers of MSP-1 specific antibodies were generated by Ad vectors 
expressing MSP-1 from a chicken β-actin (CAG) promoter comprising the 
cytomegalovirus early enhancer element and the chicken β-actin promoter.
CONCLUSIONS: The findings of the present study suggest that Ad vectors 
expressing full-length codon-optimized MSP-1 are promising candidate vaccines 
against P. falciparum infections. Use of the HC-Ad vector type for delivery, as 
well as the CAG promoter to control MSP-1 expression, may further increase the 
efficacy of this vaccine candidate.