Fig. 2.

Strong correlation between FAVN and pseudotype neutralising antibody titres using Tanzanian dog sera. (A) Neutralising titres achieved with the pseudotype assay increase concordantly with those detected in the FAVN assay. The distribution, according to VNAb titres determined by the (B) pseudotype and (C) FAVN assays, of sera collected at the first visit from primary (dogs that had not received a previous rabies vaccination—black columns), booster (dogs that had received ≥1 rabies vaccination previously—grey columns) or dogs with no vaccination record (white columns) is shown. Similar analyses for samples collected at the second visit are shown in (D) and (E) for the pseudotype and FAVN assays, respectively. The dotted line marks the level of VNAb that was achieved by the OIE positive control serum. Percents of samples with an inadequate or adequate VNAb response are given left and right of the dotted line, respectively. Vaccination history was available for 169 dogs (first visit: primary n = 119, booster n = 50, no record n = 13; second visit: primary n = 84, booster n = 37, no record n = 1). (F) Results from the pseudotype neutralisation and FAVN assays reveal a high degree of concordance (Sn: sensitivity and Sp: specificity) and a strong correlation (r) between titres. Sn and Sp are relative to the 0.5 IU/ml threshold and r/p values were calculated using Pearson's product–moment correlation. Arrows indicate VNAb titres for which there were no serum samples containing that level of antibodies.