Fig 3.

A. phagocytophilum-host cell interactions and transmission feeding of infected ticks upregulate asp14 expression. (A to C) A. phagocytophilum DC organisms were incubated with HL-60 (A), RF/6A (B), and PSGL-1 CHO (C) cells for 4 h, a period that is required for bacterial adherence and for ≥90% of bound bacteria to invade host cells. A. phagocytophilum cannot invade PSGL-1 CHO cells. Total RNAs were isolated from the DC inoculum and from host cells after 1, 2, 3, and 4 h of bacterial addition. (D) A. phagocytophilum-infected I. scapularis nymphs were allowed to feed on mice for 72 h. Total RNAs were isolated from the salivary glands of uninfected and transmission-fed ticks that had been removed at 24, 48, and 72 h postattachment. Total RNA was isolated from combined salivary glands and midguts from unfed ticks. (A to D) RT-qPCR was performed using gene-specific primers. Relative transcript levels for asp14 were normalized to A. phagocytophilum 16S rRNA gene transcript levels. The normalized values in panels A to C are presented relative to asp14 transcript levels of the DC inoculum. Data are the means and standard deviations of results for triplicate samples and are representative of two independent experiments that yielded similar results. Statistically significant (***, P < 0.001) values are indicated.