208 The antiviral and immunomodulating properties from glycerides of lauric acid in PRRSV-infected PAM cells

Abstract

Abstract The objective of this study was to assess the ability of a commercially available blend of glycerides of C12 to inhibit porcine reproductive and respiratory syndrome virus (PRRSV) replication in porcine alveolar macrophages (PAM) and to investigate the immunomodulatory effect during PRRSV infection in vitro. PAM were collected by lung lavage from 4-wk-old piglets, free of PRRSV. PRRSV strain 13V091 was used in this study and a commercially available mixture of mono-, di- and tri-glycerides of lauric acid (GC12). The product concentrations tested were 0.022% (T1), 0.044% (T2) and 0.088% (T3). Three different infection assays were used: (1) Co-incubation; PRRSV was inoculated together with GC12 for 1 h, (2) Pre- and Post-infection; GC12 was added to PAM cells for 24 h before infection and after 1 h of incubation for another 24 h, and (3) Post-infection; GC12 was added only after PRRSV infection for 24 h. Titration of the progeny virus was performed on PAM from all three infection assays. Cytokine analysis was only performed for infection assay 2 and 3. Collected supernatants were subjected to multiplex ELISA to measure the level of TNF-α and IL-8. Two-tailed t test P value was used to determine statistically significant differences. P < 0.05 was considered to be statistically significant. Addition of GC12 in the Co-incubation assay did not reduce PRRSV infectivity at 24-h post infection (hpi; Table 1). In contrast, the Pre- and Post-infection assay showed significantly reduced PRRSV titer from 6 hpi onwards at concentration 0.044%. At concentration 0.088% a significant reduction was observed at 24 hpi. Addition of GC12 after PRRSV inoculation (post-infection) also showed significantly reduced PRRSV titer from 6 hpi onwards at concentration 0.044% and 0.088%. In the Pre- and Post-infection assay, all treatments with GC12 numerically increased the production of TNF-α at 24 hpi. A dose response effect was observed at 24 hpi with increasing concentrations of GC12 resulting in increasing levels of TNF-α. However, in the Post-infection assay only treatment with 0.088% GC12 numerically increased the production of TNF-α by 1.5-fold. Compared with the control (PAM+PRRSV), a significantly greater concentration of IL-8 was observed with 0.044% (P = 0.019) and 0.088% (P = 0.007) GC12 24 hpi in the Pre- and Post-infection assay (1,806 ± 376; 3,751 ± 636; 3,439 ± 420 pg/mL respectively). These two concentrations resulted in numeric increase of IL-8 24 hpi in the Post-infection assay and no effect was observed with 0.022% GC12 (Control 2,332 ± 998; T1 2,079 ± 964; T2 3,525 ± 344; T3 4,475 ± 295). From this study it can be concluded that GC12 exhibited antiviral activity against PRRSV strain 13V091 and influences the cytokine production of PAM during PRRSV infection, potentially neutralizing the suppression of the immune response by PRRSV.