A preliminary study to evaluate the immune responses induced by immunization of dogs with inactivated <i>Ehrlichia canis</i> organisms

Abstract

Ehrlichia canis is an intracellular pathogen that causes canine monocytic ehrlichiosis. Although the role of antibody responses cannot be discounted, control of this intracellular pathogen is expected to be by cell mediated immune responses. The immune responses in dogs immunized with inactivated E. canis organisms in combination with Quil A were evaluated. Immunization provoked strong humoral and cellular immune responses, which were demonstrable by Western blotting and lymphocyte proliferation assays. By Western blotting antibodies to several immunodominant E. canis proteins were detected in serum from immunized dogs and antibody titres increased after each immunization. The complement of immunogenic proteins recognized by the antisera were similar to those recognized in serum from infected dogs. Upon challenge with live E. canis, rapid anamnestic humoral responses were detected in the serum of immunized dogs and primary antibody responses were detected in the serum from control dogs. Following immunization, a lymphocyte proliferative response (cellular immunity) was detected in peripheral blood mononuclear cells (PBMNs) of immunized dogs upon stimulation with E. canis antigens. These responses were absent from non-immunized control dogs until after infection with live E. canis, when antigen specific-lymphocyte proliferation responses were also detected in the PBMNs of the control dogs. It can be thus concluded that immunization against canine monocytic ehrlichiosis may be feasible. However, the immunization regimen needs to be optimized and a detailed investigation needs to be done to determine if this regimen can prevent development of acute and chronic disease.

Recombinant Ehrlichia canis GP19 Protein as a Promising Vaccine Prototype Providing a Protective Immune Response in a Mouse Model

“…Despite its potential veterinary and medical importance, there is currently no commercial vaccine against E. canis. Previous studies have shown partial clinical protection of inactivated and attenuated vaccine candidates after being challenged with the virulent strain [3,4]. One of the disadvantages of primitive inactivated and live-attenuated vaccines is the undesirable effects associated with some of the antigenic proteins, this has led to the need for the development of modern vaccines [5,6].…”

Effect of GP19 Peptide Hyperimmune Antiserum on Activated Macrophage during Ehrlichia canis Infection in Canine Macrophage-like Cells

“…Vaccines for E. canis are needed; however, many obstacles have impeded their development including identification of ehrlichial antigens, an understanding of the relevant genetic and antigenic variabilities, and a lack of animal models that reflect the immune responses of the hosts [ 15 ]. Previous studies have shown that inactivated and attenuated vaccine candidates for CME were capable of provoking a humoral response, but only partial clinical protection was achieved in dogs challenged with the virulent strain [ 16 , 17 ]. The peptide vaccine is among a variety of modern vaccines that represent a potential strategy for the prevention and treatment of pathogenic diseases [ 18 , 19 , 20 ].…”