In a paper published in BMC Veterinary Research, Hwi Won Seo and colleagues at Seoul National University in the Republic of Korea explain that the objective of their study was to elucidate the humoral and cellular immune response mechanisms by which a reformulated inactivated chimeric PCV1-2 vaccine reduces the PCV2 viraemia.

Forty PCV2 sero-negative three-week-old pigs were randomly divided into the following four groups:

• vaccinated challenged (T01)
• vaccinated non-challenged (T02)
• non-vaccinated challenged (T03), and
• non-vaccinated non-challenged (T04) animals.

The pigs in groups T01 and T02 were immunised with a reformulated inactivated chimeric PCV1-2 vaccine (FosteraTM PCV; Pfizer Animal Health) administered as a 2.0-ml dose at 21 days of age. At 35 days of age (0 days post-challenge), the pigs in groups T01 and T03 were inoculated intranasally with 2ml each of PCV2b.

A reduction of PCV2 viraemia coincided with the appearance of both PCV2-specific neutralising antibodies (NA) and interferon-gamma-secreting cells (IFN-gamma-SCs) in the vaccinated animals. However, the presence of anti-PCV2 IgG antibodies did not correlate with the reduction of PCV2 viraemia.

Lymphocyte subset analysis indicated that the numbers of CD3+ and CD4+ cells increased in vaccinated animals but the numbers of CD4+ cells decreased transiently in non-vaccinated animals. The observation of a delayed type hypersensitivity response in only the vaccinated animals also supports a CD4+ cell-associated protective cellular immune response induced by the reformulated inactivated chimeric PCV1-2 vaccine.

The induction of PCV2-specific NA and IFN-gamma-SCs, and CD4+ cells by the reformulated inactivated chimeric PCV1-2 vaccine is the important protective immune response leading to reduction of the PCV2 viraemia and control of the PCV2 infection, concluded the researchers. To their knowledge, Seo and colleagues observed that this is the first demonstration of protective humoral and cellular immunity induced by the reformulated inactivated chimeric PCV1-2 vaccine and its effect on reduction of PCV2 viraemia by vaccination.

Reference

Seo H.W., Y. Oh, K. Han, C. Park and C. Chae. 2012. Reduction of porcine circovirus type 2 (PCV2) viremia by a reformulated inactivated chimeric PCV1-2 vaccine-induced humoral and cellular immunity after experimental PCV2 challenge. BMC Veterinary Research, 8:194. doi:10.1186/1746-6148-8-194

Further Reading You can view the full report (as a provisional PDF) by clicking here. Find out more information on PMWS / PCV by clicking here.

November 2012