QRT-PCR analysis revealed that at early stage of infection (day 1 p.i.), mRNA levels of cell cycle genes such as CDC2 (Fig 2A), CDC25A (Fig 2B), Cyclin E (Fig 2C), CDK5 (Fig 2D), CDK8 (Fig 2E) and Cyclin G1 (Fig 2F) were significantly (P<0.05) upregulated in A. phagocytophilum-infected cells in comparison to uninfected controls. Here, CDK5 is linked to infection.