Phenotypes of porcine blood CD8β T cells and their capacity for IFN gamma production in the context of PRV vaccination

CD8 T cells play a key role in elimination of intracellular pathogens. Here, we have carried out a detailed phenotypic and functional analysis of swine blood CD8β T cells, after vaccination with a live attenuated PRV vaccine. Based on the expression of six surface molecules (CD11a, CD27, CD45RA, CD95, CCR7 and SLA-DR), up to eight subsets can be identified within the circulating compartment of CD8β T cells of adult pigs; six of which correlate phenotypically with naïve, stem cell memory, central memory, transitional memory, effector memory, and terminal effector subsets described in humans. The remaining two subsets appear to correspond to intermediate stages between naïve and central memory cells, and between transitional memory and effector memory or terminal effector cells, respectively. Although CD45RA has been proposed as a marker to distinguish between porcine naïve and central memory CD8β T cells, we found that a substantial proportion of naïve T cells, which varies among animals, lack this marker and that the combination of CD95 and CD11a allows a more accurate discrimination of these subsets among CD27^hi CCR7⁺ cells. The majority of virus-specific IFN-γ-producing CD8β T cells in the blood of PRV-vaccinated pigs, collected at 10-16-days postvaccination, showed a CD27⁺ CD11a^hi CD45RA^- phenotype, consistent with that of central, and/or transitional memory T cells.