FIG. 5.

Quantitative analysis of cytokine gene expression in circulating lymphoid cells in woodchucks during different phases of WHV POI and the animals' subsequent challenge with either a low (liver-nonpathogenic) or high (liver-pathogenic) dose of WHV. The expression of IFN-α, TNF-α, IL-12, IL-2, IFN-γ, IL-4, and IL-10 was analyzed in freshly isolated PBMC collected from animals with POI (n = 6) and after challenge with either a low (low-dose challenge; n = 3) or high (high-dose challenge; n = 3) dose of the virus. After each primary or subsequent exposure to WHV, the time line of infection was divided into four phases (phases A, B, C, and D) according to the distinct profiles of WHV-specific and mitogen-induced T-cell responses as described in Results. The number (n) under each bar shows the number of PBMC samples examined. The level of expression of each cytokine was normalized against the level of β-actin and then compared to the level observed prior to primary infection (phase A) to calculate the increase or decrease in expression. The P values above each bar represented by asterisks were obtained by comparing the mean expression level of a given gene during phase B, C, or D with the mean level of expression determined for the gene in phase A, while the P values shown at the top of each panel were obtained by comparing with each other the mean expression level of a given gene determined for phases B, C, and D. Values marked with one asterisk were significantly different at a P value of ≤0.05, values with two asterisks were significantly different at a P value of ≤0.005, and values with three asterisks were significantly different at a P value of ≤0.0001. n.s., not significantly different.