<i>In vivo</i> expression of vaccine-candidate genes.

<p>Naïve adult female BALB/c mice (n = 4) were infected intranasally with <i>B. pertussis</i> strain B1917 or B1920. After 7 days, bacteria were collected through broncho-alveolar lavage and used for <i>in vivo</i> transcriptional analysis using antigen-specific primers as described in the text. The transcription data is expressed as 40-ΔCt value, which is a measure of expression relative to the <i>recA</i> household gene (ΔCt = Ct <i>target</i> – Ct <i>recA</i>). The number 40 represents the number of PCR cycles. A 40-ΔCt value of 40 indicates that the gene is expressed at equal levels as <i>recA</i>, while higher values correspond to higher expression.