title: Experimental Ehrlichia canis infection in the dog does not cause immunosuppression.
abstract: A carrier state develops in some Ehrlichia canis-infected dogs due to ineffective host defenses. The subsequent development of immune-mediated diseases or opportunistic infections in chronic ehrlichiosis suggests dysregulation of immunity; however, the immunobiology of this infection has not been well characterized. In this study, eight dogs were infected with E. canis, and changes in seroreactivity, serum immunoglobulin (Ig) concentrations, peripheral blood T cell subsets, lymphocyte blastogenesis (LBT), and lymphokine-activated killer (LAK) activity were evaluated over 4 months. Infection, which was documented by seroconversion, polymerase chain reaction, and blood culture, caused self-limiting fever and thrombocytopenia. Infected dogs developed an anti-E. canis antibody response but were not immune to re-infection. Serum IgM, IgG, and IgA concentrations were unaffected by E. canis. The percentage of circulating CD4(+) T cells was similar in uninfected and infected dogs at all points. Infected dogs developed a CD8(+) lymphocytosis 6 weeks after inoculation that subsequently subsided, despite organism persistence. Functional defects of cell-mediated immunity, measured as suppression of LAK activity or mitogen-driven LBT, were not observed. These results suggest that immune responses are not grossly impaired in young dogs during the first several months following experimental E. canis infection.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Box 8401, 4700 Hillsborough Street, Raleigh, NC 27606, USA.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Hess
authors.forename: Robert V
authors.initials: RV
authors.lastname: English
authors.forename: Barbara C
authors.initials: BC
authors.lastname: Hegarty
authors.forename: G Dale
authors.initials: GD
authors.lastname: Brown
authors.forename: Edward B
authors.initials: EB
authors.lastname: Breitschwerdt
mesh_terms: D000818:Animals; D000917:Antibody Formation / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000382:microbiology; D004283:Dog Diseases / Q000276:immunology* / Q000382:microbiology*; D004285:Dogs; D004318:Doxycycline / Q000627:therapeutic use; D041061:Ehrlichia canis / Q000235:genetics / Q000276:immunology*; D016873:Ehrlichiosis / Q000097:blood / Q000276:immunology* / Q000382:microbiology / Q000662:veterinary*; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D007111:Immunity, Cellular / Q000276:immunology; D005779:Immunodiffusion / Q000662:veterinary; D007136:Immunoglobulins / Q000097:blood; D016130:Immunophenotyping / Q000662:veterinary; D015979:Killer Cells, Lymphokine-Activated / Q000276:immunology; D011897:Random Allocation; D013047:Specific Pathogen-Free Organisms
chemical_list: D007136:Immunoglobulins; D004318:Doxycycline