falciparum blood stage antigens induced unexpectedly robust functional antibody responses, similar to or surpassing those obtained with protein in adjuvant [10] and [43]. The 99% inhibition of P. falciparum parasite growth using 2.5 mg/ml IgG from the rabbits immunized with the cell surface associated glycosylated form of AMA1 provides the strongest inhibition of ZD1839 research buy parasite growth yet observed with only two doses of an experimental vaccine. One possible explanation is that the Plasmodium antigen

is produced in a mammalian host, which may facilitate proper folding and presentation of the antigen to the immune system. Additionally, the adenovector itself is an adjuvant, capable of potent activation of the innate immune response [44], [45], [46], [47] and [48]. In fact, Ad5 hexon protein has been shown to be a potent adjuvant for induction of antigen-specific responses [49]. Our data also showed that the functional antibody activity induced by the AdAMA1 vectors was more robust than that induced by the AdMSP142 vectors. This is in agreement with OTX015 mw other

studies of rabbit and human antibodies to AMA1 and MSP1, where it has been established that antibodies to AMA1 are more efficacious in GIA reactions than antibodies to MSP1 [41]. This may relate to the location of these antigens on the merozoite, since more antibodies may be required to block invasion to an antigen such as MSP1 which is broadly located over the merozoite surface as compared to an antigen such as AMA1 which is localized at the merozoite apex. Development of an adenovector-based vaccine that expresses both AMA1 and MSP142 may improve the inhibition of parasite growth observed with the single antigen expressing vectors described here as found well as offer other advantages such as increased breadth of both cellular and humoral

immunity, attributes that may increase vaccine efficacy. We identified optimized forms of P. falciparum AMA1 and MSP142 for inclusion in an adenovector vaccine. We focused on antigen localization and glycosylation as these are primary variables that could affect induction of immune responses. Overall, our results indicate that expression of these antigens at the cell surface is associated with improved magnitude and functionality of antibody responses relative to intracellular expression. This finding is in agreement with other published data for DNA vaccines [28] and poxvirus vaccines [50]. We observed similar T cell responses with adenovectors that expressed the various forms of both antigens indicating that T cell responses were not greatly affected by cellular location or glycosylation status. This was expected as T cell responses are generated by linear epitopes that bind intracellularly to MHC class I and class II molecules and there is no requirement for secretion or proper tertiary folding.