Sequence and expression analysis of a surface antigen gene family of the rickettsia Anaplasma marginale.

The tick-borne rickettsial organism, Anaplasma marginale, causes a disease in cattle of world-wide economic significance. This disease, anaplasmosis, is characterized by severe hemolytic anemia, high levels of rickettsemia and, often, death in animals over 3years of age. Animals that survive acute infection remain carriers, with continuous sub-microscopic cycles of rickettsemia that can persist for the lifetime of the animal.

Analysis of the Anaplasma marginale genome by pulsed-field electrophoresis.

Anaplasma marginale is a rickettsial parasite of bovine erythrocytes causing world-wide economic losses in livestock production. Despite its importance, little is known about this rickettsia at a molecular level because it has not been cultured in vitro, and there is no small-animal model. Although several genes have been cloned and sequenced, the gross genome structure of the organism has not yet been well characterized.

The importance of mosaic genes to trypanosome survival.

African trypanosomes possess several elegant ways to evade the immune defenses o f mammalian hosts. They have an extensive repertoire o f genes for a variant surface antigen and recent data show that this finite repertoire can be further amplified by mosaic gene formation and point mutation, producing an almost limitless capacity to vary. The significance of these mechanisms of antigenic diversity to trypanosome biology and the parasite-host relationship in general are discussed here by Anthony Barbet and Sondra Kamper.

Surface epitope variation via mosaic gene formation is potential key to long-term survival of Trypanosoma brucei.

Trypanosoma brucei evades the immune response of its mammalian host by antigenic variation in the major surface antigen (the variable surface glycoprotein or VSG). We examined the generation of diversity in 4 in vivo-derived antigenically related clones of T. brucei by sequencing VSG cDNA from each of the 4 clones and all 5 related genomic copies in the WaTat 1.