Fig 3.

A. phagocytophilum differentially expresses OmpA during infection of mammalian and tick cells. (A) A. phagocytophilum-infected HL-60, RF/6A, and ISE6 cells were fixed and viewed by indirect immunofluorescence confocal microscopy to determine immunoreactivity with antibodies against Msp2 (P44) (major surface protein; used to identify bacteria) and OmpA or Asp62 (confirmed surface protein). Host cell nuclei are stained with DAPI (4′,6-diamidino-2-phenylindole). Note that staining of OmpA and staining of Asp62 yield comparable ring-like bacterial surface staining patterns. (B) Percentages of morulae [based on the presence of Msp2 (P44)-positive A. phagocytophilum organisms] that are positive for OmpA in infected HL-60, RF/6A, and ISE6 cells. The data are the means and standard deviations of results of at least two separate experiments. At least 200 Msp2 (P44)-positive morulae were scored for OmpA per condition. Statistically significant (***, P < 0.001) values are indicated.