Opsonising activity of an anti-O Manisa serum can occur against a neutralized FMDV strain as well as a non-neutralized FMDV serotype-A strain. IFN-α responses of enriched pDC (CD14-depletion/CD172a-enrichment) stimulated with O UKG 2001 (A, B) or A Brazil 10/93 (C, D) pre-incubated with anti-O Manisa serum (A, C) or naïve serum (B, D). FMDV was used at an MOI of 1 TCID50/cell. Serum was heat-treated, then diluted at the indicated concentrations and pre-incubated for 30 min at 39°C with the virus. IFN-α in supernatants was measured by ELISA. Values are shown as box plots representing of 3-5 independent experiments with each condition performed in triplicate cultures. The black line represents the median value and the red line the mean value. The error bars represent the standard deviation and the dots are outlier values (5th/95th percentile). Statistical significance (Rank Sum test, P < 0.005) was calculated between immune and naïve sera employed at the same dilutions and is indicated by an asterisk. The NT against the two viruses employed is indicated in log10 of serum dilution.