Research: Cellular immune response against PCV2

29-12-2009 | |

Porcine circovirus type 2 (PCV2) is a dominant causative agent of postweaning multisystemic wasting syndrome (PMWS), a multifactorial disease complex with putative immunosuppressive characteristics.

Little is known about adaptive PCV2-specific immune responses in infected pigs. Therefore, the T and B cell responses following PCV2 infection in 3-week old SPF piglets infected with PCV2 or PCV2 plus porcine parvovirus (PPV) were studied.
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Results
All animals were asymptomatically infected. At 7 days post infection (dpi.), B lymphocyte and T lymphocyte numbers decreased in the dual infected, but not in the single infected piglets.
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At this time point a transient PCV2 viraemia was noted in the PCV2 infected groups. Antibodies against the infecting virus were detectable at day 24-28 post infection for anti-PCV2 antibodies and at day 10 p.i. for anti-PPV antibodies, with no apparent influence of PCV2 on the early PPV antibody development.
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In the animals infected with PPV alone, IFN-gamma secreting cells (SC) that were not specific for PCV2 were detected by ELISPOT assay at day 7 p.i. Interestingly, this response was absent in the PCV2/PPV dual infected animals.
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PCV2-specific IFN-gamma SC were observed in the PCV2/PPV infected group at 7 dpi and in the PCV2 single infected group at 21 dpi.
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A reduction in the numbers of IFN-gamma SC was observed following anti-CD4 and anti-CD8 antibody treatment, suggesting roles for both CD4+41 and CD8+42 T cells in the response against PCV2 infection.
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This was supported by an observed increase in the percentage of IFN-gamma positive CD8hi 43 cytotoxic T cells as well as IFN-gamma positive CD8-/low 44 helper T cells after PCV2 in vitro re-stimulation.
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Conclusions
Infection of weaned SPF piglets with PCV2 alone or combined with PPV does not induce disease and in both cases a relatively slow anti-PCV2 antibody response and weak lymphocyte responses were found.
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Knowledge on such immunologica characteristics is important for both PCV2 pathogenesis and vaccination.
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Esther Steiner, Carole Balmelli, Heidi Gerber, Artur Summerfield, and Kenneth McCullough: Cellular adaptive immune response against porcine circovirus type 2 in subclinically infected pigs. BMC Veterinary Research 2009, 5:45

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