Development of in situ hybridization assay that differentiates between two genotypes of Porcine circovirus-2 in formalin-fixed, paraffin-embedded tissues.

The aim of the current study was to develop a nonradioactive in situ hybridization assay that can differentiate between genotypes 2a and 2b of Porcine circovirus-2 (PCV-2) in formalin-fixed, paraffin-embedded lymph node tissues from pigs with postweaning multisystemic wasting syndrome. Two different digoxigenin-labeled oligonucleotide probes were designed from the PCV-2 open reading frame 2 sequences. The PCV-2a-specific probe did not hybridize with formalin-fixed, paraffin-embedded lymph nodes from naturally PCV-2b-infected pigs and vice versa. Both PCV-2a-specific and PCV-2b-specific probes gave consistent negative signals in lymph nodes from naturally PCV-1-infected pigs. The in situ hybridization assay described in the present study represents a diagnostic tool that can differentiate between the 2 genotypes of PCV-2.