2014-051 – Attenuated Vaccines to Protect Canines and Humans Against Tick-Borne Ehrlichia Species Infections

Researchers at Kansas State University aredeveloping modified live vaccine candidates to prevent tick-borne Ehrlichia andAnaplasma species infection in dogs and humans. Canine VaccineDevelopment: Canine ehrlichiosis is caused by threetick-borne rickettsials of the genus Ehrlichia: E. canis, E. ewingii,and E. chaffeensis. All three canine pathogens cause disease with clinicalsymptoms that include fever, lethargy, exercise intolerance, nasal dischargeand bleeding. Although clinical symptoms of the disease subside followingdoxycycline therapy, the treatment may not clear the pathogens completely. Dogsrecovered from clinical disease retain low infections for several years(potentially for life). Persistent infection has two important implications: 1)the disease can revert when the host immunity is suppressed, and 2) dogs withsubclinical-infections serve as infection reservoirs for ticks to acquire andtransmit the pathogens to naive dogs or people. Because Ehrlichia infectimmune cells, they have higher potential to suppress host defenses and impairthe health of dogs. Preliminary Data: K-State recently established mutagenesis methods forE. chaffeensis. The inventors have identified two mutants of the organism whose growth is attenuated in dogs and deer (reservoir host of the pathogen). Furthermore, preliminary data revealed that one of the two mutants tested conferred complete protection against wild-type needle infection challenge in both dogs and deer, while the second mutant offered partial protection. This preliminary data is being used to pursue grants to conduct a larger canine study to evaluate these twoE. chaffeensismutants for their potential as attenuated live vaccines to protect dogs against tick infection challenges with wild-typeE. chaffeensis(homologous) andE. canis(heterologous). Bret Ford bretford@ksu.edu 785-532-3924