Abstract: Targeted disruption of a specific gene and its subsequent restoration in obligate intracellular bacteria remains extremely challenging due to their absolute requirement for residence inside a host cell to replicate. Here, targeted allelic exchange mutations were created to inactivate two genes and then to restore one of the two genes of a rickettsial pathogen, Ehrlichia chaffeensis. These methods were then also successfully utilized in Ehrlichia canis and Anaplasma phagocyophilum. The resultant mutated pathogens are useful in immunogenic compositions for reducing the incidence of or severity of infection with ricksettsial pathogens.

Abstract: Axenic media and methods for growing E. Chaffeensis and/or A. phagocytophilum are provided. In general, the axenic media includes intracellular phosphate buffer (IPB), a carbon source, FBS, a mixture of amino acids, and at least one further component selected from the group consisting of glucose 6-phosphate (G6P), ATP, DTT, GTP, UTP, CTP, and any combination thereof.

Abstract: Attenuated vaccines to protect vertebrate animals and people against tick-born rickettsial, Ehrlichia and Anaplasma species infections is disclosed. Also disclosed are methods to modify the organism to achieve the desired immunity through the modification of a novel genetic region involved in pathogenesis. These compounds represent a needed vaccine against an organism causing life-threatening febrile illness in humans and animals, and also represent the potential to develop new classes of drugs targeting the gene products of genes Ech_0379 and Ech_0230, and their homologs of other related rickettsial pathogens.

Abstract: Targeted disruption of a specific gene and its subsequent restoration in obligate intracellular bacteria remains extremely challenging due to their absolute requirement for residence inside a host cell to replicate. Here, targeted allelic exchange mutations were created to inactivate two genes and then to restore one of the two genes of a rickettsial pathogen, Ehrlichia chaffeensis. These methods were then also successfully utilized in Ehrlichia canis and Anaplasma phagocyophilum. The resultant mutated pathogens are useful in immunogenic compositions for reducing the incidence of or severity of infection with ricksettsial pathogens.

Abstract: The present disclosure provides immunogenic compositions and vaccines effective for reducing the incidence of or severity of clinical signs or symptoms of infection by a tick-borne pathogen selected from the group consisting of Rickettsia rickettsii, Ehrlichia chaffeensis, Ehrlichia canis, Ehrlichia ruminantium, Anaplasma marginale, and Anaplasma phagocytophilum. In preferred forms, the immunogenic composition comprises an inactivated whole cell bacteria selected from the group consisting of Rickettsia rickettsii, Ehrlichia chaffeensis, Ehrlichia canis, Ehrlichia ruminantium, Anaplasma marginale, Anaplasma phagocytophilum, and any combination thereof, together with an adjuvant.

Abstract: Attenuated vaccines to protect vertebrate animals and people against tick-born rickettsial, Ehrlichia and Anaplasma species infections is disclosed. Also disclosed are methods to modify the organism to achieve the desired immunity through the modification of a novel genetic region involved in pathogenesis. These compounds represent a needed vaccine against an organism causing life-threatening febrile illness in humans and animals, and also represent the potential to develop new classes of drugs targeting the gene products of genes Ech_0379 and Ech_0230, and their homologs of other related rickettsial pathogens.

Abstract: Attenuated vaccines to protect vertebrate animals and people against tick-born rickettsial, Ehrlichia and Anaplasma species infections is disclosed. Also disclosed are methods to modify the organism to achieve the desired immunity through the modification of a novel genetic region involved in pathogenesis. These compounds represent a needed vaccine against an organism causing life-threatening febrile illness in humans and animals, and also represent the potential to develop new classes of drugs targeting the gene products of genes Ech_0660, Ech_0379, and Ech_0230, and their homologs of other related rickettsial pathogens.

Abstract: Attenuated vaccines to protect vertebrate animals and people against tick-born rickettsial, Ehrlichia and Anaplasma species infections is disclosed. Also disclosed are methods to modify the organism to achieve the desired immunity through the modification of a novel genetic region involved in pathogenesis. These compounds represent a needed vaccine against an organism causing life-threatening febrile illness in humans and animals, and also represent the potential to develop new classes of drugs targeting the gene products of genes Ech_0660, Ech_0379, and Ech_0230, and their homologs of other related rickettsial pathogens.

Abstract: Attenuated vaccines to protect vertebrate animals and people against tick-born rickettsial, Ehrlichia and Anaplasma species infections is disclosed. Also disclosed are methods to modify the organism to achieve the desired immunity through the modification of a novel genetic region involved in pathogenesis. These compounds represent a needed vaccine against an organism causing life-threatening febrile illness in humans and animals, and also represent the potential to develop new classes of drugs targeting the gene products of genes Ech_0660, Ech_0379, and Ech_0230, and their homologs of other related rickettsial pathogens.