Differentiation of porcine circovirus 1 and 2 in formalin-fixed, paraffin-wax-embedded tissues from pigs with postweaning multisystemic wasting syndrome by in-situ hybridisation

Abstract

Non-radioactive digoxigenin (DIG)-labelled probes that can differentiate porcine circovirus (PCV) 1 from PCV 2 in formalin-fixed, paraffin-wax-embedded tissues by in-situ hybridisation were developed. A 349 base pair (bp) DNA fragment from open reading frame (ORF) 1 of PCV 1 and a 481 bp DNA fragment from ORF 2 of PCV 2 generated by polymerase chain reaction (PCR) were used as PCV 1 and PCV 2 probes, respectively. A specific DIG -labelled PCV 1 DNA probe did not hybridise withPCV 2-infected PK-15 cells and vice versa. From the 40 field cases with postweaning multisystemic wasting syndrome tested by in-situ hybridisation, 30 (75 per cent) cases were PCV 2-positive only and 10 (25 per cent) cases were positive for both PCV 1 and PCV 2. PCV 1 and PCV 2 DNA s were detected mainly in the macrophages of lymph nodes and spleens. Positive cells typically exhibited a dark brown to black reaction product mainly in the cytoplasm but also occasionally in the nucleus. In-situ hybridisation together with the differential probes developed in the present study represent an additional tool capable of differentiating of both types of PCV in formalin-fixed, paraffin-wax-embedded tissues.