Long-Term Protective Immunity against <i>Ehrlichia chaffeensis</i> Infection Induced by a Genetically Modified Live Vaccine
Swetha Madesh,
Jodi McGill,
Deborah C. Jaworski,
Jonathan Ferm,
Huitao Liu,
Shawna Fitzwater,
Paidashe Hove,
Dominica Ferm,
Arathy Nair,
Cheyenne A. Knox,
Kimia Alizadeh,
Ashley Thackrah,
Roman R. Ganta
Affiliations
Swetha Madesh
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Jodi McGill
Department of Veterinary Microbiology & Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA
Deborah C. Jaworski
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Jonathan Ferm
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Huitao Liu
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Shawna Fitzwater
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Paidashe Hove
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Dominica Ferm
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Arathy Nair
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Cheyenne A. Knox
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Kimia Alizadeh
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Ashley Thackrah
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Roman R. Ganta
Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
Human monocytic ehrlichiosis, an emerging tick-borne disease, is caused by Ehrlichia chaffeensis. Infections with the pathogen are also common in the canine host. Our previous studies demonstrated that functional disruption within the E. chaffeensis phage head-to-tail connector protein gene results in bacterial attenuation, creating a modified live attenuated vaccine (MLAV). The MLAV confers protective immunity against intravenous and tick transmission challenges one month following vaccination. In this study, we evaluated the duration of MLAV protection. Dogs vaccinated with the MLAV were challenged with wild-type E. chaffeensis via intravenous infection at 4-, 8-, and 12-months post-vaccination. Immunized dogs rapidly cleared the wild-type pathogen infection and tested positive for bacteremia less frequently than unvaccinated controls. While immune responses varied among dogs, vaccinees consistently mounted IgG and CD4+ T-cell responses specific to E. chaffeensis throughout the assessment period. Our findings demonstrate that MLAV-mediated immune protection persists for at least one year against wild-type bacterial infection, marking a major advancement in combating this serious tick-borne disease. The data presented here serve as the foundation for further studies, elucidating the molecular mechanisms underlying virulence and vaccine development and aiding in preventing the diseases caused by E. chaffeensis and other tick-borne rickettsial pathogens.