Nanoparticle orientationally displayed antigen epitopes improve neutralizing antibody level in a model of porcine circovirus type 2

Ding, Peiyang; Zhang, Teng; Li, Yafei; Teng, Man; Sun, Yaning; Liu, Xiao; Chai, Shujun; Zhou, Enmin; Jin, Qianyue; Zhang, Gaiping

The titers of PCV2 neutralizing antibody (NA) in sera were determined by the immunoperoxidase monolayer assay (IPMA) as previously described with minor modifications. 34 Briefly, sera samples were heat-inactivated at 56°C for 30 min and serially diluted at 2-fold, then mixed with an equal volume of 200 TCID 50 of PCV2 on 96-well culture plates with DMEM containing 2% FBS, and incubated for 1 h at 37°C. After incubation, the mixtures were added to 96-well plates containing 20% confluent PK15 cells. After incubation for 72 h, the cells were fixed for 30 min with cold ethanol at -20°C. After blocking with 5% skimmed milk for 1 h at 37°C, the cells were incubated with guinea pig anti-PCV2 polyclonal antibody, followed by HRP-conjugated goat anti-guinea pig IgG. The color cells were developed with 3-amino-9-ethylcarbazole and hydrogen peroxide in 0.05 M acetate buffer (pH 5.0). The neutralization titer was calculated as the reciprocal of the highest serum dilution that was able to completely block PCV2 infection in PK15 cells.