Abstract
BackgroundPorcine circovirus type 1 (PCV1) has been described as a non-cytopathic contaminant of the PK-15 cell line. Several experimental infections with PCV1 failed to reproduce disease in pigs. Therefore, PCV1 is generally accepted as non-pathogenic to pigs. To our knowledge, nothing is known about the outcome of PCV1 infections in porcine foetuses. This was examined in the present study.ResultsNine foetuses from three sows were inoculated at 55 days of gestation: three with 104.3 TCID50 of the PCV1 cell culture strain ATCC-CCL33, three with 104.3 TCID50 of the PCV1 field strain 3384 and three with cell culture medium (mock-inoculated). At 21 days post-inoculation, all 6 PCV1-inoculated and all 3 mock-inoculated foetuses had a normal external appearance. Microscopic lesions characterized by severe haemorrhages were observed in the lungs of two foetuses inoculated with CCL33. High PCV1 titres (up to 104.7 TCID50/g tissue) were found in the lungs of the CCL33-inoculated foetuses. All other organs of the CCL33-inoculated foetuses and all the organs of the 3384-inoculated foetuses were negative (< 101.7 TCID50/g tissue) by virus titration. PCV1-positive cells (up to 121 cells/10 mm2 in CCL33-inoculated foetuses and up to 13 cells/10 mm2 in 3384-inoculated foetuses) were found in the heart, lungs, spleen, liver, thymus and tonsils. PCR and DNA sequencing of Rep recovered CCL33 or 3384 sequences from CCL33- or 3384-inoculated foetuses, respectively.ConclusionsFrom this study, it can be concluded that cell culture PCV1 can replicate efficiently and produce pathology in the lungs of porcine foetuses inoculated at 55 days of foetal life.
Highlights
Porcine circovirus type 1 (PCV1) has been described as a non-cytopathic contaminant of the PK-15 cell line
Haemorrhages in the lungs can be explained by the fact that due to the high PCV1 replication in the epithelial cells, there might be the release of inflammatory mediators, which may lead to the increased permeability of the blood vessels followed by leakage of blood or haemorrhage
Our study showed that the lung tissue was the main target organ of replication of CCL33 strain, as this PCV1 strain could only be isolated with high titres from the lungs
Summary
Porcine circovirus type 1 (PCV1) has been described as a non-cytopathic contaminant of the PK-15 cell line. PCV1 is generally accepted as non-pathogenic to pigs. To our knowledge, nothing is known about the outcome of PCV1 infections in porcine foetuses. This was examined in the present study. High PCV1 titres (up to 104.7 TCID50/g tissue) were found in the lungs of the CCL33-inoculated foetuses. PCV1-positive cells (up to 121 cells/10 mm in CCL33-inoculated foetuses and up to 13 cells/10 mm in 3384-inoculated foetuses) were found in the heart, lungs, spleen, liver, thymus and tonsils. Porcine circovirus type 1 (PCV1) is a small, non-enveloped circular single-stranded DNA virus of the family Circoviridae. The distribution of PCV1 in different pig tissues after experimental infections has been demonstrated [9]. PCV1 has been detected in cases of congenital tremors in newborn pigs
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