Neutralising antibodies (NA) inherently present in pooled plasma collected at commercial abattoirs may provide some protection against potential PCV2 infectivity of plasma, according to Javier Polo of APC Europe S.A. and co-authors from the US and Spain. Moreover, they explain, these NA may also contribute to the biosafety of spray-dried porcine plasma (SDPP).

The objective of their study, described in Journal of Animal Science, was to characterise and quantify the PCV2 antibody neutralising capacity in pooled liquid porcine plasma and SDPP samples collected from industrial spray-drying facilities located in the Southeast and Midwest regions of the United States and the Northeast region of Spain.

In the US, PCV2 NA was determined in one sample of pooled liquid plasma from commercial spray-drying plants in the Southeast and one from the Midwest region. Results were compared with those of a plasma sample from a PCV2-vaccinated sow and one from a PCV2 antibody-negative sow.

In Spain, 15 pooled liquid porcine plasma samples and 10 SDPP samples were collected at a commercial spray-drying plant total and NA against PCV2 were determined.

Results with pooled liquid porcine plasma from commercial spray-drying facilities in the United States indicated that NA titres against PCV2 in these samples (log₂ 8.33 ± 0.41 and 9.0 ± 0.0) were similar or greater than the plasma from the PCV2-vaccinated sow (log₂ 6.33 ± 0.41).

The analysis of US samples indicated that liquid plasma diluted to 1:256 (10–2.41) was able of neutralising between 100 to 200 PCV2 virus particles or about 4 logs₁₀ median tissue culture infective dose (TCID₅₀) per millilitre.

Similarly, samples from the Spanish pooled liquid plasma and the SDPP samples indicated an increased amount of NA activity against PCV2. Specifically, a dilution of 10–2.47 ± 0.33 of plasma was able to inactivate 100 PCV2 virus particles; therefore, the inactivation capacity of commercial liquid plasma was greater than 10⁴ TCID₅₀ per mL. The calculated 90 per cent reduction in infected cells because of NA in pooled plasma samples (log₂ 8.2 ± 0.38) was less (P<0.05) than in its concentrate form of SDPP (mean, log₂ 10.2 ± 0.85).

Polo and co-authors concluded that PCV2 NA contained in liquid pooled plasma from market pigs was detected at greater concentrations than that from a vaccinated sow and that after spray-drying, biological neutralising activity was conserved, which implies that the inherent NA in liquid plasma may have an important role in the biosafety of commercially produced SDPP.

Reference

^{Polo J., T. Opriessnig, K.C. O'Neill, C. Rodríguez, L.E. Russell, J.M. Campbell, J. Crenshaw, J. Segalés and J. Pujols. 2013. Neutralizing antibodies against porcine circovirus type 2 in liquid pooled plasma contribute to the biosafety of commercially manufactured spray-dried porcine plasma. J. Anim. Sci. 91(5):2192-2198. doi: 10.2527/jas.2012-5705}

August 2013