Impact of BC-loop mutations on neutralization by sera from controllers and non-controllers. Neutralizing titres in controller (n = 6, filled symbols) and non-controller (n = 6, open symbols) sera at 12 months post-KTx were measured against PSV carrying wild type VP1 and different VP1 variants. Experiments were performed in 293TT cells. For each serum, the log10 neutralizing titre against the wild-type virus was subtracted from the log10 neutralizing titre against the VP1 variant measured at the same PSV dose, and the result is plotted for each PSV variant. (A) genotype Ib2 variants; (B) genotype IVc2 variants. Red symbols and adjacent patient codes indicate the cognate non-controller serum for each VP1 variant. Input PSV doses were 500 pEGFP copies/cell for Ib2-V72Q73Q82 and Ib2-V68V72A73, 200 pEGFP copies/cell for Ib2-N69Q82 and 100 pEGFP copies/cell for genotype IV variants. (C) Neutralization curves for wild-type Ib2-E73E82, Ib2-N69Q82 and Ib2-N60N69V72Q82 PSV in serum from patient 3.4 at 12 months post-KTx. (D) Neutralization curves for wild-type IVc2, IVc2-S61 and IVc2-S61K69A73N77 PSV in serum from patient 3.3 at 12 months post-KTx.