Modulation of anti-viral activity and viral-induced lymphoid depletion by conjugated linoleic acid

Bassaganya-Riera, J., R. Hontecillas, P.G. Halbur, K.J. Yoon, M.J. Wannemuehler, and R.M. Progranichniy (2003) Modulation of anti-viral activity and viral-induced lymphoid depletion by conjugated linoleic acid. The FASEB Journal 17(4): A2 (Abstract #27.2).

We had previously shown that conjugated linoleic acid (CLA) enhanced antigen-specific proliferation of CD8+ T cells to viral antigens. In the present study, live and inactivated type-2 porcine circovirus (PCV2) were used to examine the modulatory properties of CLA on T cell responses and viral disease. PCV2 is a small, single-stranded-DNA virus, which induces lymphoid depletion in pigs. Following dietary supplementation with either soybean oil or CLA, pigs were exposed to viral antigens (i.e., live or inactivated PCV2). Viral-induced lymphoid depletion was histopathologically evaluated and the depleted lymphocyte subsets were phenotypically characterized. PCV2-specific lymphocyte proliferation was assessed following immunization or challenge. The live PCV2 challenge caused B cell depletion, weight loss, and interstitial pneumonia, all of which was attenuated in CLA-fed pigs. Even though no differences in proliferation were detected between dietary treatments at optimal antigenic stimulation levels (i.e., live PCV2 challenge), when the antigenic stimuli were weaker (i.e., inactivated PCV2), CLA enhanced PCV2-specific proliferation. The results of the blastogenesis assays indicate that the potentiation of PCV2-specific T cell proliferation by CLA may be limited during optimal immune responses and enhanced at sub-optimal stimulation levels. Hence, the positive effects of CLA on viral disease may not be associated with the enhancement of PCV2-specific T cell responses.