Fig. 7. Neutralising antibodies in serum measured by Plaque reduction neutralisation test (PRNT₅₀).

Serum neutralisation titres as reciprocal highest dilution resulting in an infection reduction of >50% in samples (PRNT₅₀) pre-challenge and at 1–3, 4–6, 8–9, 11–12 and 14–19 days post-challenge in rhesus macaques (blue) and cynomolgus macaques (red). For rhesus macaques: n = 6 at 0, 1-3 and 4–6 dpc; n = 4 at 8-9 and 14-19 dpc; n = 3 at 11–12 dpc. For cynomolgus macaques: n = 6 at 4–6 dpc; n = 5 at 0 and 1–3 dpc; n = 4 at 8–9; 11–12 and 14–19 dpc. Bars indicating group mean±standard error with PRNT₅₀ determined for individual animals shown as circles and squares respectively. Neutralising antibodies were observed at 8–9 dpc at low levels, increasing from 11 dpc onwards, with higher values in cynomolgus macaques compared to rhesus.