FIG. 2.

Inhibition of serum neutralization (SN) to assay the authentic antigenic characteristics of secE2. (a) Diagram showing the principle of the assay, where BVDV neutralizing antibodies preincubated with medium containing secE2 are blocked, allowing the virus to destroy the cell monolayer. (b) The quantitative assay performed in a 96-multiwell plate where 4 sera (1, 2, 3, and 4) containing neutralizing antibody against BVDV were tested at different dilutions (log₂ of the serum dilution) in the presence of secE2 (+Sera +secE2) and in the absence of secE2 (+Sera −secE2). Control virus was established in the absence of sera and presence of secE2 (−Sera +secE2) and in the absence of sera and secE2 (−Sera −secE2). Crystal violet staining allows macroscopic evaluation of the integrity (blue wells) or the destruction (clear violet wells) of the cell monolayer. (c) Bar graph showing the quantification of serum neutralization made on the basis of three different experiments (P < 0.0009). Results are expressed as the reciprocal of the highest dilution of the serum that inhibited the development of virus-induced cytopathic effect in cell culture.