Recombinant Ehrlichia TRP75 Rescues Molting Failure of Ticks Infected with TRP75 Mutant Ehrlichia

Recombinant TRP75 restores molting failure in Ixodes scapularis ticks infected with an Ehrlichia japonica TRP75{Delta}C mutant, rescuing molting efficiency to ~90%.

• Why it matters: Ehrlichia transmission between ticks and mammalian hosts depends on tick survival and development, but how specific bacterial molecules control tick molting is largely unknown.
• What they did: A Himar1 transposon mutant of Ehrlichia japonica lacking the TRP75 C-terminal intrinsically disordered region (TRP75{Delta}C) was tested in tick and mammalian cells and in mice; EcR mRNA was measured at 15 days post-feeding.
• The result: TRP75{Delta}C-infected ticks ingested similar blood and acquired similar infection but mostly failed to molt by 10 weeks post-feeding, with no EcR mRNA upregulation; recombinant full-length TRP75 microinjection restored molting and increased EcR mRNA versus solvent controls.