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Kinetics of antibody response to Ehrlichia canis immunoreactive proteins
Jere W McBride1, Richard E Corstvet, Steven D Gaunt
1Department of Pathology, Sealy Center for Vaccine Development, and Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas 77555-0609, USA. jemcbride@utmb.edu
Abstract:
Immunoreactive proteins of Ehrlichia canis and Ehrlichia chaffeensis that have been characterized include a family of 28-kDa major outer membrane proteins (p28) and two large antigenically divergent surface glycoprotein orthologs. We previously demonstrated that recombinant E. canis p28 and the 140- and 200-kDa glycoproteins gp140 and gp200, respectively, react strongly with serum antibodies from suspect canine ehrlichiosis cases that were positive for E. canis by immunofluorescent antibody test and in various phases of acute or chronic infection (J. Clin. Microbiol. 39:315-322, 2001). The kinetics of the antibody response to these potentially important vaccine and immunodiagnostic candidates is not known. Acute-phase serum antibody responses to whole-cell E. canis lysates and recombinant p28, gp140, and gp200 were monitored for 6 weeks in dogs experimentally infected with E. canis. Irrespective of the inoculation route, a T-helper 1-type response was elicited to E. canis antigens consisting of immunoglobulin G2 antibodies exclusively in both acute and convalescent phases in most dogs. Analysis of immuoreactive antigens for peak intensity and relative quantity identified major immunoreactive E. canis antigens recognized early in the infection as the 19-, 37-, 75-, and 140-kDa proteins. Later in infection, additional major immunoreactive E. canis proteins were identified, including the 28-, 47-, and 95-kDa proteins and the recently identified 200-kDa glycoprotein. All dogs had developed antibody against the recombinant gp140, gp200, and p28 in the convalescent phase. Immunoreactivity and antibody response kinetics suggest that major immunoreactive proteins identified are immunodominant, but early recognition suggests increased dominance by some antigens.
Insights
This study tracked antibody responses in dogs infected with Ehrlichia canis, identifying key proteins like p28, gp140, and gp200 that elicit immune reactions. Early recognition of certain antigens suggests their importance in canine ehrlichiosis diagnosis and vaccines.
Area of Science:
- Veterinary Immunology
- Molecular Biology
- Infectious Diseases
Background:
- Ehrlichia canis causes canine ehrlichiosis, a significant tick-borne disease.
- Key immunoreactive proteins, including p28, gp140, and gp200, are known targets in canine ehrlichiosis.
- The kinetics of antibody response to these antigens are not well understood.
Purpose of the Study:
- To investigate the antibody response kinetics to Ehrlichia canis antigens in experimentally infected dogs.
- To identify immunodominant E. canis antigens recognized during acute and convalescent infection phases.
- To evaluate the potential of recombinant proteins (p28, gp140, gp200) as diagnostic or vaccine candidates.
Main Methods:
- Experimental infection of dogs with E. canis.
- Monitoring of acute-phase serum antibody responses over six weeks.
- Analysis of antibody response to whole-cell lysates and recombinant proteins (p28, gp140, gp200).
- Identification of major immunoreactive antigens based on intensity and quantity.
Main Results:
- A T-helper 1-type immune response, characterized by IgG2 antibodies, was observed in most dogs.
- Early infection recognized 19-, 37-, 75-, and 140-kDa proteins as major antigens.
- Later infection identified 28-, 47-, 95-kDa proteins and the 200-kDa glycoprotein.
- All dogs developed antibodies against recombinant gp140, gp200, and p28 by the convalescent phase.
Conclusions:
- The study elucidates the antibody response kinetics to E. canis antigens in dogs.
- Identified major immunoreactive proteins are immunodominant, with some antigens showing early dominance.
- Recombinant p28, gp140, and gp200 are promising candidates for immunodiagnostics and vaccines against canine ehrlichiosis.