Fig. 4

Virus load and PRRSV-special antibody levels of the infected piglets during the challenge experiment. (A) The dynamics of virus titers in sera were determined by the IFA-microtitration infectivity assay. Serum samples were collected at 0, 4, 7, 11, and 14 dpi and virus titers are expressed as 50% of the tissue culture infective dose per mL (TCID50/mL) of the sample. (D) PRRSV-specific N protein antibody levels in sera after challenge. Serum samples were collected at 0, 4, 7, 11, and 14 dpi and the threshold for seroconversion was set at a sample-to-positive (s/p) ratio of 0.4. sterisk indicates significant differences between the FJLIUY-2017-inoculated group and PRRSV2/CN/G8/2018-inoculated group (*p < 0.05)