Changes in human granulocytic ehrlichiosis (HGE)-specific major outer membrane protein (p44 kD) were assayed by Western blot analysis in HL-60 cells in vitro infected by the HGE agent. Time course study demonstrated that the expression of p44 preceded the rise in cell infection as determined by the presence of intracellular morulae. To test whether the expression of p44 may be suitable for evaluating the effects of antibiotics in vitro, three recent isolates of the HGE agent were exposed to doxycycline and ampicillin during culture with HL-60 cells. Loss of infection concurrent with disappearance of the 44 kD protein was found with doxycycline treatment. In contrast, ampicillin treatment had no discernible effects on infection or 44 kD expression. There was excellent agreement between infection, as measured by morulae, and 44 kD) expression (coefficient of correlation r = 0.97, p < 0.01). Following treatment with doxycycline, the 44 kD protein disappeared with an estimated t(1/2) of ~24-30 h, which was considerably shorter than a t(1/2) of > 60 h calculated for loss of morulae. Measurement of p44 expression may be a more rapid and simple assay to determine antibiotic susceptibility of the HGE agent in cell culture. Furthermore, it may be used to indicate the presence of infection before morulae are apparent.
|Original language||English (US)|
|Number of pages||5|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Apr 13 1999|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology