Experimental infection of colostrum-deprived (CD) pigs with a combined inoculum of porcine circovirus 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) potentiated the replication and distribution of PCV2 virus, when compared with pigs inoculated with PCV2 alone. The replication and distribution of PRRSV in dually infected pigs was not enhanced, when compared to pigs inoculated with PRRSV alone. The mechanisms involved in the potentiation of PCV2 replication in PCV2/PRRSV and PCV2/porcine parvovirus (PPV) dually infected pigs may relate to the fact that monocyte/macrophage cell types are common targets of these 3 viruses.

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Abstract. We report the development of a competitive enzyme-linked immunosorbent assay (c-ELISA) for the detection of antibodies to porcine circovirus type 2 (PCV2), the agent associated with the recently described postweaning multisystemic wasting syndrome in pigs. At present, no method has been published describing a c-ELISA for the detection of antibodies to PCV2, and currently employed tests are impractical for use in some laboratories. The assay described here uses a cell culture isolate of porcine circovirus type 2 as antigen and a PCV2-specific monoclonal antibody as the competing reagent. Evaluation of the ELISA was performed by comparison with results obtained using an indirect immunofluorescent test on 484 sera from pig herds in the United Kingdom, Canada, France, and the USA and serial bleeds from pigs experimentally infected with porcine circoviruses. The sensitivity and specificity of the ELISA were determined as 99.58% and 97.14%, respectively, at 2 standard deviations (SD) from the mean or 95.81% and 100% at 3 SD from the mean. Using this ELISA, a serologic survey of 461 sera collected from commercial pig herds in Northern Ireland between 1973 and 1999 was undertaken. Analysis of the results of this survey demonstrated that the number of ELISA-positive sera detected in an individual year during this period ranged from 55% to 100%. This c-ELISA has applications for large-scale rapid diagnosis of PCV2 infection in pig populations worldwide and for immunoscreening of sera from other species for antibodies to PCV2.Porcine circovirus (PCV) was first identified in 1974 as a noncytopathic contaminant of a continuous pig kidney (PK-15) cell line. 34 The virus was later shown to possess a single-stranded circular DNA genome of 1.76 kb 8,25,31 and is now classified in a new virus family, the Circoviridae. 23 Serum antibodies to the PCV contaminant of PK-15 cell cultures have been demonstrated in pig populations worldwide, 1,11,12,18,20,32 However, experimental infection of pigs with this virus has failed to produce clinical disease. 4,32 Postweaning multisystemic wasting syndrome (PMWS) in pigs, first identified in western Canada in 1991, 9 is characterized by progressive weight loss, respiratory signs, and jaundice. 9,17 Similar syndromes have also been described in pigs in the USA, 10 France, 22 Northern Ireland, 21 Spain, 27 the Republic of Ireland, 29 Denmark, 6 and Germany. 19 The demonstration of PCV antigen and nucleic acid in lesions sug- Received for publication September 3, 1999. gested that a new, more virulent PCV may have emerged in pig populations in these countries. 5,13,22 All PCV isolates characterized from cases of PMWS form a closely related group at the nucleotide sequence level, exhibiting Ͼ96% intragroup nucleotide sequence identity, 26 but are quite distinct from the PCV isolated from the PK-15 cell line, exhibiting less than 80% nucleotide sequence identity. 16,24,26 It has been proposed that the PCV associated with PMWS should be referred to as PCV type 2 (PCV2) and the PCV conta...

The production, preliminary characterisation and applications of monoclonal antibodies (mabs) against six porcine circovirus 2 isolates are described. A total of 14 stable hybridomas were produced, of which 7 were characterised. All of the mabs characterised were of IgG isotype. All the mabs tested reacted by IIF with acetone-fixed cell cultures infected with PCV2 isolates from Canada, France, Spain, Denmark, USA and UK. No cross-reactivity with a porcine circovirus 1 field isolate was demonstrated using the panel of mabs tested. In addition, one of the seven mabs tested demonstrated neutralising activity against PCV2 isolates from Canada and France. The use of selected PCV2-specific mabs for the development of virus detection methodologies is described.

We report the isolation and characterisation of porcine circovirus 2 (PCV2) from cases of sow abortion and porcine dermatitis and nephropathy syndrome. The results suggest that the clinical scope of PCV2 infections requires continuous re-evaluation.