New publications about porcine circovirosis during 2009

Porcine circovirus type 2 (PCV2) is considered the essential infectious agent for postweaning multisystemic wasting syndrome (PMWS) development. Five papers published during 2009 describe the latest results obtained by the PCV group at CReSA. Moreover, two papers have also been published as a result of the collaboration with other research groups in Mexico and Germany.

Research on PCV2 at CReSA-UAB has been carried out since 1997. Some of the most remarkable achievements have been reached as a result of the CReSA-UAB’s participation in the 5FP and 6FP funded projects called "Pathogenesis, epidemiology, immunopathology and diagnosis of PMWS: an emerging disease of swine due to a new porcine circovirus (PCV). Development of recombinant vaccines" and “The Control of Porcine Circovirus Diseases (PCVDs): Towards Improved Food Quality and Safety”, respectively.

During 2009 the group has published five papers based on the results obtained in the last project. Below are summarized the main results of these papers:

1) The immunogenicity and efficacy generated by one dose of a PCV2 sub-unit vaccine (Porcilis PCVÒ) were evaluated in 3-week-old conventional piglets. Vaccination induced both humoral and cell-mediated responses against PCV2, which were increased after the challenge with a PCV2 genotype "b" isolate. The immunity induced by one dose of the product was partly protective against PCV2 infection, since viremia, shedding and viral load in tissues were significantly reduced in vaccinated pigs compared to controls.
In: One dose of a porcine circovirus 2 (PCV2) sub-unit vaccine administered to 3-week-old conventional piglets elicits cell-mediated immunity and significantly reduces PCV2 viremia in an experimental model. Fort M, Sibila M, Pérez-Martín E, Nofrarías M, Mateu E, Segalés J. Vaccine. 2009 May 3. [Epub ahead of print]

2) A longitudinal study was carried out to assess the evolution of two acute phase proteins (APPs), pig-major acute phase protein (pig-MAP) and haptoglobin (HPT), in serum from pigs that developed PMWS in comparison to healthy and wasted non-PMWS affected pigs. Results suggested that pig-MAP might be a better indicator of PMWS status than HPT. Moreover, the fact that APR occurred some weeks before the start of clinical signs suggests that APPs could provide valuable prognostic information for PMWS development.
In: Pig-major acute phase protein and haptoglobin serum concentrations correlate with PCV2 viremia and the clinical course of postweaning multisystemic wasting syndrome. Grau-Roma L, Heegaard PM, Hjulsager CK, Sibila M, Kristensen CS, Allepuz A, Piñeiro M, Larsen LE, Segalés J, Fraile L. Vet Microbiol. 2009 Mar 13. [Epub ahead of print]

3) Ultrastructural lesions in lymph nodes from PMWS affected pigs were evaluated and correlated with detection of viral-like particles (VLPs). Significant ultrastructural alterations were only noted in PMWS-affected pigs, mainly in histiocytes and rarely in other cell types. Lymphocyte depletion was a striking finding of lymph nodes from PMWS-affected pigs. The inclusion bodies containing VLPs referred in the present study should be classified as viral factories, suggesting that viral replication is probably a frequent event in macrophages, in which mitochondria might play a role.
In: Ultrastructural findings in lymph nodes from pigs suffering naturally ocurring postweaning multisystenic wasting syndrome. Rodriguez-Cariño C, Segales J. Vet Pathol. 2009 Mar 9. [Epub ahead of print]

4) Longitudinal case-control studies were performed in PMWS affected farms from Denmark and Spain using similar designs. Results showed that PCV2 load increased in parallel to waning maternal antibody levels, reaching the maximum viral load concurrent with development of clinical signs. Danish farms had a higher PCV2 prevalence in young piglets as well as an earlier PMWS presentation compared to Spanish farms. Positive and significant correlations were found among PCV2 viral loads present in sera, nasal swabs, rectal swabs and lymphoid tissues, which indicates that nasal and rectal swabs were suitable indicators of PCV2 excretion. It is also suggested that qPCR and/or serology tests are not apparently able to substitute histopathology plus detection of PCV2 in tissues for the individual PMWS diagnosis within PMWS affected farms. However, qPCR appears to be a potential reliable technique to diagnose PMWS on a population basis.
In: Infection, excretion and seroconversion dynamics of porcine circovirus type 2 (PCV2) in pigs from post-weaning multisystemic wasting syndrome (PMWS) affected farms in Spain and Denmark. Grau-Roma L, Hjulsager CK, Sibila M, Kristensen CS, López-Soria S, Enøe C, Casal J, Bøtner A, Nofrarías M, Bille-Hansen V, Fraile L, Baekbo P, Segalés J, Larsen LE. Vet Microbiol. 2009 Mar 30;135(3-4):272-82. Epub 2008 Oct 17.

5) Early innate and adaptive immune responses were examined in 1-week-old, caesarean-derived, colostrum-deprived piglets using a subclinical infection model of PCV2 in combination with lipopolysaccharide (LPS) as a potential immunostimulation factor. The use of LPS did not show any significant effect on the course of PCV2 infection, nor did in the evolution of the immunological parameters evaluated. In vitro cytokine determination showed that, regardless of the treatment administrated to the pigs, an interleukin (IL)-10 release was observed when peripheral blood mononuclear cells (PBMC) cultures were stimulated with PCV2. Results from the present work suggest that viral clearance might be mediated by the development of PCV2-specific IFN-gamma-secreting cells in contribution to the PCV2-specific neutralizing antibodies (NA).
In: Development of cell-mediated immunity to porcine circovirus type 2 (PCV2) in caesarean-derived, colostrum-deprived piglets. Fort M, Fernandes LT, Nofrarias M, Díaz I, Sibila M, Pujols J, Mateu E, Segalés J. Vet Immunol Immunopathol. 2009 May 15;129(1-2):101-7. Epub 2008 Dec 25.

Likewise, two papers have been published in 2009 fruit of the collaboration with other groups of research in Mexico and Germany, respectively:

1) A PCV-2 retrospective serological survey was carried out with 659 serum samples collected from pigs in Mexico between 1972 and 2000. Serological analyses were performed with an immunoperoxidase monolayer assay (IPMA). This study shows evidence of enzootic PCV-2 infection in Mexico for many years before the first description of PMWS in the country (in 2001), further supporting results obtained in other parts of the world. To date, this study provides the earliest evidence of PCV-2 infection in the North and South American continents.
In: Retrospective serological survey of Porcine circovirus-2 infection in Mexico. Ramírez-Mendoza H, Castillo-Juárez H, Hernández J, Correa P, Segalés J. Can J Vet Res. 2009 Jan;73(1):21-4.

2) Archived material of pigs originating from Northern Germany and submitted for necropsy between 1961 and 1998 were investigated by using in situ hybridisation and polymerase chain reaction. In summary, findings showed that PCV2 has been present in the pig population in Northern Germany since 1962. This represents worldwide the earliest report about the detection of the PCV2 genome in pigs. Associated lesions such as PMWS and porcine dermatitis and nephropathy syndrome (PDNS) were not observed before 1985, indicating that virus infection alone does not seem to be sufficient enough to trigger the development of associated entities.
In: Retrospective study on the occurrence of porcine circovirus 2 infection and associated entities in Northern Germany.

Jacobsen B, Krueger L, Seeliger F, Bruegmann M, Segalés J, Baumgaertner W. Vet Microbiol. 2009 Jul 2;138(1-2):27-33. Epub 2009 Feb 13.

Lymph node, PMWS-affected pigs. 3a: Apoptotic lymphocyte showing nuclear convolution, margination of chromatin and electron-lucent zones. Mitochondrial swelling (arrow) is observed in the cytoplasm. (Bar = 500 nm). 3b: Phagocytosis of  a lymphocyte by a histiocyte (arrow-head), with an adjacent intracytoplasmic inclusion containing VLPs (close-up insert) (Bar = 1 μm).

To contact the principal investigator:

Joaquim Segalés i Coma
Researcher
Viral Diseases Unit (CReSA)
E-mail: joaquim.segales@cresa.uab.cat
Telephone no.: +34 93 581 45 63
Fax: +34 93 581 44 90
Edifici CReSA. Campus UAB
08193 Bellaterra (Barcelona) Spain

To know more about the PCVDs project:

http://www.pcvd.org/index.php?lang=es


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