VMP001-NP immunization elicits high avidity antibodies capable of agglutinating live sporozoites.

<p>(A) Avidity indices of anti-VMP001 IgG sera obtained from mice immunized as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031472#pone-0031472-g003" target="_blank">Fig. 3</a> with soluble VMP001+MPLA (red circles) or VMP001-NP+MPLA (blue circles) were characterized over 6 months following vaccination. *, <i>p</i><0.01 and **, <i>p</i><0.001, analyzed by two-way ANOVA, followed by a Bonferroni post-test. (B) Anti-VMP001 IgG antibodies elicited with soluble VMP001+MPLA (red circles) or VMP001-NP+MPLA (blue circles) were further examined for their affinities against key fragments of VMP001, including peptides representing the Type I repeat, AGDR motif, Region I, Region II, C-terminus, and scrambled negative peptide control. Sera from non-immunized mice were also included as controls (black squares). (C,D) Sera obtain from mice on day 63 post-immunizations with 2.5 µg VMP001 and 25 µg MPLA in either (C) soluble or (D) VMP001-NP formulations were incubated with live VK210 sporozoites, and immunoflurescence assay was performed to assess recognition of native CSP present on the surface of live sporozoites by anti-VMP001 IgG sera. Mice immunized with VMP001-NP vaccines raised sera that agglutinated live VK210 subtype of <i>P. vivax</i>.