ULTRASTRUCTURAL AND ANTIGENIC CHARACTERIZATION OF A GRANULOCYTIC EHRLICHIOSIS AGENT DIRECTLY ISOLATED AND STABLY CULTIVATED FROM A PATIENT IN NEW-YORK-STATE

A human granulocytic ehrlichiosis (HGE) agent with 16S rDNA sequence i dentical to the published sequence of HGE agents was isolated from a p atient from New York State by inoculation of the blood leukocyte fract ion directly into a human promyelocytic leukemia cell line HL-60. The HGE agent was also isolated from the leukocyte fraction of the blood a nd bone marrow of a mouse inoculated with the leukocyte fraction of th e patient's blood. The isolate has been passaged in tissue culture 30 times over 8 months. Electron microscopy revealed pleomorphic coccobac illi with a thin and highly rippled outer membrane in the clear inclus ion matrix. Comparison of IFA reactivity of antisera obtained from a v ariety of sources with the cell-cultured HGE agent revealed that 3 HGE agent strains (Neu York isolate, Wisconsin [BDS] isolate, and a tick- derived isolate) are highly cross-reactive and there are diverse antig enic cross-reactivities between HGE agent and Ehrlichia chaffeensis.