Circoviridae

About: Circoviridae is a research topic. Over the lifetime, 207 publications have been published within this topic receiving 16692 citations.

Porcine circoviruses: a review.

Abstract: Porcine circoviruses (PCV) are small nonenveloped DNA viruses containing a unique single-stranded circular genome. Previously, no recognized link was found between PCV infection of pigs and disease, and PCV was considered a nonpathogenic agent. Over the last 5 years, a "novel" PCV, designated PCV2, has been associated with various disease syndromes in pigs, primarily postweaning multisystemic wasting syndrome (PMWS). Pigs with PMWS have a variety of clinical signs, including debility, dyspnea, palpable lymphadenopathy, diarrhea, and pallor or icterus. Lesions associated with the presence of PCV2 in a variety of cell types include lymphohistiocytic to granulomatous interstitial pneumonia, hepatitis, nephritis, myocarditis, enteritis, and pancreatitis. The lesions of PMWS have been reproduced experimentally after inoculation of piglets with PCV2 cell culture isolates, although the full expression of the disease syndrome may require the presence of other agents such as porcine parvovirus or porcine reproductive and respiratory syndrome (PRRS) virus. Recent reports have linked PCV2 to other disorders in pigs, ranging from abortion and reproductive failure to "atypical" PRRS. Available data indicate high seroprevalence of antibodies to PCV2 worldwide. The diagnosis of PCV2-associated disease is based on the direct demonstration of PCV2 antigens or nucleic acid in affected tissues. PCV2 is now regarded as an important emerging pathogen. Although vertical transmission has been documented, the epidemiology of PCV2 infections is poorly understood, as is the role of the immune response in controlling or augmenting disease.

A very small porcine virus with circular single-stranded DNA

Abstract: It was reported previously that cultures of the porcine PK-15 cell line (ATCC-CCL31) were chronically infected with a small virus, supposedly containing RNA1. No gross cytopathic effect was seen in these cultures. During the search for an in vitro model of persistent virus infections the agent was studied in more detail. These studies showed the virus to have a diameter of 17 nm, and to contain a covalently closed circular single-stranded DNA with a molecular weight of 0.58 × 106 and a main capsid polypeptide with a molecular weight of 36,000. Of the animals tested, only pigs were found to have antibodies. On the basis of these properties the virus appears to be a member of a family of animal viruses so far not encountered. We have named the virus porcine circovirus (PCV).

Isolation of Porcine Circovirus-like Viruses from Pigs with a Wasting Disease in the USA and Europe:

Abstract: Samples of lung, liver, kidney, pancreas, spleen, and lymph node from pigs with postweaning multisystemic wasting syndrome from California (USA) and samples of mesenteric lymph nodes from similarly diseased pigs from Brittany (France) were examined by light microscopy, in situ hybridization (ISH), and/or virus isolation. Whole genomic probes for porcine circovirus (PCV) and chicken anemia virus (CAV) were used for ISH. Tissue homogenate supernatants were inoculated onto PK/15 cells for virus isolation, and the presence of viral antigen and viral particles was verified by indirect immunofluorescence, ISH, and electron microscopy. Histologic examination of lung from pigs from California revealed interstitial pneumonia, alveolar epithelial hyperplasia, and basophilic nuclear and cytoplasmic inclusions in mononuclear cell infiltrates and various pulmonary epithelial cells. Granulomatous lymphadenitis with syncytial cells typified the lesions seen in the pigs from France. PCV-like nucleic acid was detected by ISH in lung, pancreas, lymph node, kidney, and liver in pigs from California. Positive signal was also obtained in lymph node sections from pigs from France. Probes for CAV were consistently negative. PK/15 cell cultures inoculated with lung preparations from diseased California pigs and mesenteric lymph node preparations from pigs from France had positive fluores- cence by indirect staining for PCV using pooled polyclonal pig sera and hyperimmune rabbit serum and had variable staining with a panel of 7 monoclonal antibodies specific for cell culture contaminant PCV. PCV-like nucleic acid was also detected by ISH in cell cultures. Cytopathic effect was not observed. Electron microscopic examination of inoculated cell cultures revealed 17-nm viral particles morphologically consistent with PCV. No other virus particles were observed. Although genomic analysis for the definitive identification of these viral isolates remains to be done, the evidence provided strongly suggests that these tissue isolates are closely related to, although antigenically distinct from, the original PCV cell culture contaminant. Porcine circovirus (PCV) was first detected as a contaminant of a continuous pig kidney cell line (PK/ 15). 17 Since this initial identification, this virus has been shown to contain a single-stranded circular DNA genome of 1.76 kb 13,15 and is now classified in a new virus family, the Circoviridae. 11 Serum antibody to PCV has been demonstrated in pigs from Germany, 15,16 Canada, 7 New Zealand, 10 Great Britain, 8 and Northern Ireland. 4 Experimental infections of pigs with PCV in- ocula, derived from contaminated PK/15 cell cultures, have failed to produce clinical disease. 3,16 Although several PCV isolates have been recovered from still- born piglets in Northern Ireland, 3 the potential of these

Isolation of circovirus from lesions of pigs with postweaning multisystemic wasting syndrome.

Abstract: Postweaning multisystemic wasting syndrome (PMWS), an apparently new disease, has been recognized in swine herds in western Canada. Young pigs with this disease have progressive weight loss, tachypnea, dyspnea, and jaundice, accompanied by interstitial pneumonia, lymphadenopathy, hepatitis, and nephritis. We examined more than 400 pigs from more than 70 herds in Alberta, Saskatchewan, and Manitoba with cases of PMWS. A small virus was isolated from a range of tissues from 8 of 8 affected pigs examined. The agent was identified as a circovirus-like virus using electron microscopy, immunohistochemical staining with porcine and rabbit immune serum, and in situ hybridization. Immunohistochemical examination of tissues from more than 100 affected pigs has revealed widespread viral antigen, often contained in circovirus-like inclusion bodies, in lesions from numerous organs. Although Koch's postulates remain to be fulfilled, these results demonstrate a high degree of association between the presence of the circovirus-like virus and PMWS in affected swine.

Characterization of novel circovirus DNAs associated with wasting syndromes in pigs.

Abstract: Porcine circovirus (PCV) was initially recognized as a contaminant of continuous pig kidney cell lines and was not thought to be pathogenic. Antibodies reactive to the cell culture isolate of PCV (PCV PK-15) are prevalent in the swine population worldwide. Recently, PCV PK-15-like antigen and nucleic acid were demonstrated in lesions associated with wasting syndromes in pigs in North America and Europe. Monoclonal antibodies raised to circoviruses isolated from pigs with wasting syndromes highlighted differences between these circoviruses and the PCV PK-15 cell culture isolate. This has led to speculation that a new pathogenic PCV may have emerged in the swine populations of several countries. We report the cloning and characterization of novel circovirus DNAs purified from virus isolates made from tissues of North American and European pigs with wasting syndromes. These North American and European circoviruses form a closely related group at the nucleotide sequence level (> 96% intra-group nucleotide sequence identity) but exhibit < 80% nucleotide sequence identity with the PCV PK-15 cell culture isolate. This report provides evidence for a new type of possibly pathogenic PCV. We propose that these new circoviruses should be referred to as PCV2 as opposed to the original PK-15 cell culture isolate, which should be referred to as PCV1.