Relationship between ELISA antibody titre and <i>in vitro</i> parasite growth inhibition.

<p>Association of antibody levels with <i>in vitro</i> antibody functionality for three of the four immunisation groups (Gps 2, 3 and 4) is shown for parasite strains whose AMA1 allelic antigens were available for antibody measurement. In order to obtain an optimal estimate of the association, growth inhibition data at all four antibody concentrations tested (6.0, 3.0, 1.5 and 0.75 mg/ml) for each sample were included. Plots are based on a four-parameter logistic function, and each symbol/colour represents individual rabbits in the same immunisation group.</p

Alignment of the protein sequences (aa25-545) of <i>Pf</i>AMA1 antigens used in this study.

<p>DiCo proteins were used to immunise rabbits and as capture antigens in ELISA. Natural allele AMA1 proteins were used to immunize rabbits, and as capture and competitor antigens in (competition) ELISAs. All proteins were produced in <i>Pichia pastoris</i> and are devoid of N-glycosylation sites. These have been replaced with amino acid residues (indicated in red) that occur in AMA1 sequences from other malarial species (N162Q, T288V, S373D, N422D, S423K, N499Q). Residue 162 is unique as it is also a polymorphic residue. Additionally, all sequences contain a point mutation at position 376 (K to R, indicated in orange). This was necessary to prevent protein cleavage by <i>P. pastoris</i> proteases.</p

Levels of anti-AMA1 antibody elicited with the four multi-allele vaccine formulations in rabbits.

<p>Gp 1 rabbits were immunised with seven AMA1 antigens (DiCo mix and AMA1 from FVO, HB3, 3D7 and CAMP parasite strains) in CoVaccine HT™, and the other groups were immunised with DiCo mix in CoVaccine HT™ (Gp 2), Montanide IMS (Gp 3) and Montanide ISA 51 (Gp 4) respectively. Antibody titres were determined by a standardized ELISA with DiCo 1, DiCo 2, DiCo 3, FVO, HB3, 3D7 and CAMP AMA1-coated plates. Data is presented on a Log2 scale as dotplots with a boxplot superpose indicating the lower and upper quartiles as well as the median per immunisation group. Within the same immunisation group, plotting symbols represent the antibody titre of individual rabbits on all coating/capture antigens.</p

Growth inhibition of <i>Plasmodium</i> parasites by antibodies elicited with the three DiCo mix vaccines.

<p>Antibodies from all immunisation groups were tested on each of six culture-adapted strains (7G8, CAMP, FCR3, HB3, L32 and NF54) of <i>P. falciparum</i>. Plots represent the mean % inhibition ± SEM for all antibody samples within an immunisation group. Blue filled circles (•) represent Gp 2 (DiCo mix in CoVaccine HT™, n = 8), green open diamonds (◊) represent Gp 3 (DiCo mix in Montanide IMS, n = 8) and red filled squares (▪) represent Gp 4 (DiCo mix in Montanide ISA 51, n = 5).</p

Mean % antibody depletion from DiCo 1, 2 and 3-coated plates.

<p>Antibody depletion after competition ELISA, values reported as mean % depletion (95%CI).</p><p>7Ag – vaccine containing DiCo mix + four AMA1 alleles from FVO, HB3, 3D7 and CAMP parasite strains.</p><p>3Ag – vaccine containing DiCo mix.</p><p>NM &DM – competitor antigen mixtures comprising natural AMA1 alleles (FVO, HB3, 3D7, CAMP) and DiCo mix, respectively.</p

Mean % antibody depletion from FVO and 3D7 AMA1-coated plates.

<p>Antibody depletion after competition ELISA, values reported as mean % depletion (95%CI).</p><p>7Ag – vaccine containingDiCo mix + four AMA1 alleles from FVO, HB3, 3D7 and CAMP parasite strains.</p><p>3Ag – vaccine containing DiCo mix.</p><p>NM &DM – competitor antigen mixtures comprising natural AMA1 alleles (FVO, HB3, 3D7, CAMP) and DiCo mix, respectively.</p

Seroprevalence curves for rainy season survey.

<p>Seroprevalence curves represent the rate at which individuals become seropositive to specific antigens. In each graph, points represent age seroprevalence (divided into deciles), unbroken lines represent maximum likelihood curves and broken lines represent 95% confidence intervals.</p

Annual seroconversion and seroreversion rate estimates by the superinfection model based on antigen-specific antibodies.

<p>Annual seroconversion and seroreversion rate estimates by the superinfection model based on antigen-specific antibodies.</p

Comparison of parasite prevalence between surveys.

<p>Comparison of parasite prevalence between surveys.</p

Map of the study area showing the dam and non-dam study communities.

<p>Credit: Mr. Richard Adade, GIS & Remote Sensing Unit, Department of Fisheries and Aquatic Sciences, Center for Coastal Management, University of Cape Coast, Cape Coast, Ghana.</p