Propagation dynamics of Anaplasma marginale in a Brazilian tick cell line (RBME-6) derived from Rhipicephalus microplus

Anaplasma marginale is an obligate intraerythrocytic alpha-proteobacterium that causes bovine anaplasmosis, which is responsible for economic losses in the livestock industry worldwide. Although the mechanism of A. marginale infection in tick cell lines has been extensively studied, replication dynamics have not been investigated so far. This study presents the replication kinetics of A. marginale in the RBME-6 tick cell line derived from Rhipicephalus microplus over time. Cell cultures were infected with corpuscles of A. marginale isolated from bovine blood. The replication curve was generated by the number of copies of the msp1β gene obtained by reverse-transcription quantitative PCR (RT-qPCR) using complementary DNA (cDNA) synthesized from RNA. An initial lag phase and an exponential replication phase were recorded. A subsequent death phase was observed, with rapidly decreasing numbers of A. marginale msp1β copies. The surviving population of A. marginale entered a long-term stationary phase from 13 dpi until 29 dpi. Light microscopy was used to monitor the infection in the cells. The propagation kinetics of A. marginale in RBME-6 cells were shown to be essential for guiding future studies aimed at unraveling the crosstalk between this bacterium and its biological tick vector.