Figure 4.

Detection of neutralizing antibodies against Classical swine fever virus by virus neutralization test (VNT) after sample treatment. A total of 33 serum samples were treated with phosphate buffered saline (PBS) 0.3% Tween₂₀ or PBS 0.5% Tween₂₀ and incubated at 56 °C for 30 min. Afterwards, these samples were analyzed in comparison to non-treated samples in the VNT. In addition to the titers of neutralizing antibodies, titer differences between the treated and non-treated samples are depicted. A negative value for the titer difference showed a reduction of the antibody titer compared to the non-treated samples. Results for samples ID 1–15 are summarized in (A) and those for the sample ID 16–33 in (B).