No spots were observed in control wells containing splenocytes but no coating antigen. The percentage of peripheral blood and splenic CD8+ T cells expressing IFNγ, TNFα and IL-2 in response to 5 h stimulation with 5 μg/ml peptides 90 and 91 was assessed by intracellular cytokine staining as previously described . selleck Surface staining was with anti-CD8α PerCP-Cy5.5 and anti-CD4 Pacific Blue while intracellular staining was with anti-IFNγ APC,
anti-TNFα FITC and anti-IL-2 PE (all supplied by eBioscience, UK). Cytokine production frequency in peptide-unstimulated control wells (which was typically <0.1%) was subtracted from the result in peptide-stimulated wells prior to further analysis. The gating strategy is illustrated in supplementary Figure 1. Total IgG and isotype ELISA were carried out as previously described using bacterially expressed GST-tagged PfMSP119 (Wellcome/FVO allele) as the coating antigen . Antibody avidity was assessed by sodium thiocyanate (NaSCN)-displacement ELISA . Using previously measured total IgG ELISA titers, sera were individually diluted to a level calculated to give a titer of 1:300 and plated at 50 μl/well in 16 wells of a 96 well plate. Following incubation and washing, an ascending concentration of the chaotropic agent NaSCN was added down the plate (0–7 M NaSCN). Plates were incubated for 15 min
at room temperature before washing and development as for total IgG. The intercept of the OD405 curve for each ABT-888 sample with the line of 50% reduction of the OD405 in the NaSCN-free well for each sample (i.e. the concentration of NaSCN required to reduce the OD405 to 50% of that without NaSCN) was used as a measure of avidity. Statistical analysis was carried out using Prism 5 software (GraphPad, La Jolla, CA, USA). All ELISA titers were log10 Carnitine dehydrogenase transformed prior to analysis. Graphs indicate sample arithmetic means; error bars where present indicate 95% confidence intervals for the population arithmetic
mean. One-way ANOVA was used for comparing normally distributed data with Bonferroni’s multiple comparison post-test for comparison of specific groups; Kruskal–Wallis tests were used for comparison of non-normally distributed data with Dunn’s multiple comparison post-test for comparison of specific groups. Two-way ANOVA was used for comparison of groups differing in two factors. Two-way repeat measures ANOVA was used for comparison of responses measured for different groups at different time points, after the exclusion of the small number of mice for which replicate data were not available at all time points. P < 0.05 was taken to be statistically significant throughout. The experimental design provided replicate groups receiving AdCh63–MVA (A–M) and AdCh63–protein (A–P) sequential regimes at 57 day and 97 day intervals. Antibody and IFNγ+ CD8+ T cell responses induced by these regimes are illustrated in Fig. 1.