Fig. 1
Expression, purification, and screening of EspP1, rEspP2, and rApd. a Expression of rEspP1, rEspP2, and rApd in E. coli BL21 (DE3). MW, molecular weight. Lane 1, Transformants including vectors; Lane 2, Non-induced transformants including plasmids pET-espP1, pET-espP2, and pET-apd; Lane 3, Induced transformants including plasmids pET-espP1, pET-espP2, and pET-apd; Lane 4, Supernatants from the sonication of the induced transformants; Lane 5, Pellets from the sonication of the induced transformants. Asterisk indicates the target protein bands. b Purification of the rEspP1, rEspP2, and rApd. Lane 1, Non-binding effluent fraction when loading; Lane 2–8, Eluted fraction using elution buffer containing imidazole at 5, 20, 50, 100, 150, 200, and 300 mM. Asterisks indicate the target protein bands. c rEspP1, rEspP2, and rApd were used to coat ELISA plates at 1 μg/ml to detect 12 positive and 12 negative porcine sera of H. parasuis. The line represents the average OD630 value of the positive sera, and the dotted line represents that of the negative sera. For rEspP1 and rEspP2, the OD630 values of negative sera were comparable with those of positive sera (P > 0.05), whereas rApd clearly discriminated the positive from negative samples according to the OD630 value (P < 0.001)