Prolonged immune response to tick-borne Ehrlichia chaffeensis infection using a genetically modified live vaccine.

Ehrlichia chaffeensis, a tick transmitted rickettsial bacterium, causes monocytic ehrlichiosis in humans and dogs. Earlier, we demonstrated that dogs immunized with a mutant strain of E. chaffeensis having a functional disruption in the gene encoding the phage head-to-tail connector protein serves as a modified live vaccine (MLAV) capable of inducing immunity against intravenous and tick-transmitted infection challenges within one month of vaccination.

Long-Term Protective Immunity against Infection Induced by a Genetically Modified Live Vaccine.

Human monocytic ehrlichiosis, an emerging tick-borne disease, is caused by . Infections with the pathogen are also common in the canine host. Our previous studies demonstrated that functional disruption within the phage head-to-tail connector protein gene results in bacterial attenuation, creating a modified live attenuated vaccine (MLAV).

Genetically modified live vaccine offers protective immunity against wild-type Anaplasma marginale tick-transmission challenge.

Anaplasma marginale is a tick-borne pathogen of cattle that causes bovine anaplasmosis in tropical and subtropical regions throughout the world. Killed vaccines derived from infected erythrocytes have been used for control of this disease with limited success. Recently, we described a targeted deletion mutation in the phage head-to-tail connector protein gene of A.