Fig. 1.

Neutralization phenotype of PRRSV-01. (A) Susceptibility of PRRSV-01 to cross-neutralization by heterologous antisera. The neutralizing activity of the indicated antiserum was separately measured against PRRSV-01 or against the homologous virus (i.e., the virus used for immunization to prepare each of the reference antisera). (B) Homologous neutralizing antibody (NAb) responses of pigs infected with PRRSV-01. Three recently weaned pigs (pigs 2533, 6180, and 7368) were inoculated with PRRSV-01 as described in Materials and Methods. Homologous neutralization titers of serum samples at the indicated time (in days) postinfection (PI) are shown. Neutralization titers were expressed as the reciprocal of the highest dilution that showed 90% or greater reduction in the number of fluorescent foci presenting in the control wells.