title: Persistent Infections and Immunity in Ruminants to Arthropod-Borne Bacteria in the Family Anaplasmataceae.
abstract: Tick-transmitted gram-negative bacteria in the family Anaplasmataceae in the order Rickettsiales cause persistent infection and morbidity and mortality in ruminants. Whereas Anaplasma marginale infection is restricted to ruminants, Anaplasma phagocytophilum is promiscuous and, in addition to causing disease in sheep and cattle, notably causes disease in humans, horses, and dogs. Although the two pathogens invade and replicate in distinct blood cells (erythrocytes and neutrophils, respectively), they have evolved similar mechanisms of antigenic variation in immunodominant major surface protein 2 (MSP2) and MSP2(P44) that result in immune evasion and persistent infection. Furthermore, these bacteria have evolved distinct strategies to cause immune dysfunction, characterized as an antigen-specific CD4 T-cell exhaustion for A. marginale and a generalized immune suppression for A. phagocytophilum, that also facilitate persistence. This indicates highly adapted strategies of Anaplasma spp. to both suppress protective immune responses and evade those that do develop. However, conserved subdominant antigens are potential targets for immunization.
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington 99164; email: wbrown@vetmed.wsu.edu.
authors.forename: Wendy C
authors.initials: WC
authors.lastname: Brown
authors.affiliation: Department of Infectious Diseases and Pathology, University of Florida, Gainesville, Florida 32611; email: barbet@ufl.edu.
authors.forename: Anthony F
authors.initials: AF
authors.lastname: Barbet
mesh_terms: D000709:Anaplasma / Q000276:immunology / Q000302:isolation & purification; D042322:Anaplasma marginale / Q000276:immunology / Q000302:isolation & purification; D041081:Anaplasma phagocytophilum / Q000276:immunology / Q000302:isolation & purification; D000710:Anaplasmataceae / Q000276:immunology* / Q000302:isolation & purification; D000711:Anaplasmataceae Infections / Q000276:immunology* / Q000382:microbiology; D000818:Animals; D000940:Antigenic Variation; D001181:Arthropods / Q000382:microbiology*; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes; D002417:Cattle; D004285:Dogs; D006736:Horses; D054884:Host-Pathogen Interactions; D006801:Humans; D007109:Immunity; D012418:Ruminants; D012756:Sheep; D017282:Tick-Borne Diseases / Q000276:immunology* / Q000382:microbiology; D013987:Ticks / Q000382:microbiology
chemical_list: D001425:Bacterial Outer Membrane Proteins; C450839:p44 protein, Anaplasma phagocytophila
keywords: Anaplasma marginale; Anaplasma phagocytophilum; Rickettsiales; T-cell exhaustion; antigenic variation; immune evasion