FIG 6.

Proinflammatory cytokine levels remain unaltered over time in rabbits infected with the ΔespZ REPEC strain. Intestinal mucosal scrapings were used for quantitation of multiple cytokines on day 3 (A) or day 7 (B) postinfection in rabbits gavaged with PBS or the WT or isogenic ΔespZ strain. RNA was isolated from the samples as described in Materials and Methods and subjected to reverse transcription and quantitative PCR to determine IL-1β, IL-6, and IFN-γ levels. The relative gene expression level was obtained by normalizing the specific cytokine gene expression level to that of the control hypoxanthine-guanine phosphoribosyltransferase gene.