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PCV2 Link to Follicular Dendritic Cells

by 5m Editor
6 July 2010, at 8:35am

DENMARK - One or more tissues of 60 per cent of the pigs were positive for porcine circovirus type 2 (PCV2) antigen, and almost 78 per cent of pigs had some lymphoid lesions although these were not associated with PCV2.

M.S. Hansen of the The National Veterinary Institute at the Technical University of Denmark and co-authors havepublished a paper on the occurrence and tissue distribution of PCV2 identified by immunohistochemistry in Danish finishing pigs at slaughter in Journal of Comparative Pathology earlier this year.

Infection with PCV2 may be subclinical or lead to the development of porcine circovirus disease (PCVD), which includes the entities of post-weaning multisystemic wasting syndrome (PMWS) and the porcine respiratory disease complex (PRDC), they explain. PCV2 infection and PMWS occur in the early post-weaning period and are also recognised in finishing pigs of 12 to 19 weeks of age.

The aim of their study was to assess the role of PCV2 infection in disease of finishing pigs. Accordingly, the occurrence and tissue distribution of PCV2 was examined in Danish finishing pigs at the time of slaughter. Multiple lymph nodes and the spleen, lungs and kidneys from 136 pigs with PRDC (case group) and 36 pigs without lung lesions (control group) were examined by immunolabelling for the presence of PCV2. Additionally, follicular dendritic cells (FDC) were identified immunohistochemically.

One or more tissues of 61 per cent of the pigs were positive for PCV2 antigen. Up to 78 per cent of the pigs had mild lymphoid depletion, indistinct lymphoid follicles and/or histiocytic infiltration of the lymph nodes, but these lesions were not associated with PCV2.

Hansen and co-authors report that they found no association between the presence of lung or kidney lesions and detection of PCV2. Three distinct patterns of cellular PCV2 antigen labelling were recognised:

  1. labelling of cells with stellate morphology and reticular distribution,
  2. labelling of isolated non-epithelial, cells, and
  3. epithelial labelling.

The reticular pattern was most common and localized to the centres of lymphoid follicles, corresponding to the morphology and distribution of FDCs.

Hansen and co-authors conclude that this observation may be interpreted to suggest that PCV2 may interact with FDCs to cause depletion of B-lymphocytes. Alternatively, the FDCs may be a reservoir of infective PCV2 in subclinically infected animals or represent a simple storage site for PCV2 antigen in pigs that have recovered from infection.

Reference

Hansen M.S., S.E. Pors, V. Bille-Hansen, S.K.J. Kjerulff and O.L. Nielsen. 2010. Occurrence and tissue distribution of porcine circovirus type 2 identified by immunohistochemistry in Danish finishing pigs at slaughter. Journal of Comparative Pathology, 42 (2-3): 109-121. doi: 10.1016/j.jcpa.2009.07.059.

Further Reading

- You can view the full report (fee payable) by clicking here.
- Find out more information on Post-Weaning Multisystemic Wasting Syndrome (PMWS) by clicking here.

5m Editor