4c). Under these conditions significant differences between AdNull and both AdAMA1-GM2 and AdAMA1
were observed (p = 0.0002); the latter two are indistinguishable in this assay. Similar results were found when the AMA1 ELISA results were analyzed ( Fig. 4d). The C-terminal Icotinib 42 kDa proteolytic fragment of MSP1 (MSP142) is a preferred form of antigen for vaccine development [12], but does not have a signal sequence and would be expected to be located intracellularly following vaccine delivery. Studies with DNA-MSP1 vectors suggest that it may be possible to enhance the surface expression and secretion of PfMSP1 fragments by utilizing the signal sequence from the human decay-accelerating factor (DAF) protein [42]. To determine if modifications in MSP142 enhance its immunogenicity following adenovector-mediated delivery, we constructed four adenovectors expressing different versions of MSP142 ( Fig. 5a). The construct expressing the native MSP142 antigen without a signal sequence is termed MSP142-IC. Each of the other three forms contain the signal peptide from
DAF fused to Smoothened antagonist the N-terminus MSP142. MSP142-DS contains only the DAF secretion signal. MSP142-DSA contains the DAF secretion signal and substitutes the DAF GPI anchor for the native MSP1 GPI anchor. MSP142-DS-GM contains the DAF secretion signal and a single amino acid substitution N to Q at position 321 which disrupts the putative N-linked glycosylation site in MSP142. All forms of MSP142 were engineered for expression from E1/E3/E4-deleted Ad5 vectors with the expression cassette driven by the human cytomegalovirus (hCMV) immediate early gene promoter inserted at the site of the E1 deletion ( Fig. 5b). To determine the glycosylation status of the different forms of MSP142 following adenovector delivery, we transduced A549 cells with the MSP142 adenovectors and treated the cell lysates with PNGase F prior to gel electrophoresis and immunoblotting. We observed a mobility shift in the MSP142-DS and MSP142-DSA antigens following digestion with PNGase F indicating that these antigens are N-glycosylated when delivered via an adenovector.
The DS-GM and IC forms of MSP142 were not glycosylated following adenovector delivery as the mobility of these antigens was not affected by PNGase F treatment (Fig. 5c). We determined the cell surface Resminostat localization of the various MSP142 antigens by immunofluorescence, using anti-MSP142-specific polyclonal antibody R94256. Comparison of the MSP142 staining in the presence or in the absence of saponin indicated that all versions of MSP142 are primarily located intracellularly following adenovector delivery. Some cell surface staining was noted following transduction with the DS, DSA and DS-GM, MSP142 expression vectors, but not the IC vector (Fig. 6). We also analyzed cell surface localization MSP142 antigens by flow cytometry (Table 1).
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