Combinatorial selection of high affinity RNA ligands to live African trypanosomes.
African trypanosomiasis is a parasitic disease caused by a specific class of protozoan organisms. The best-studied representative of that group is Trypanosoma brucei which is transmitted by tsetse flies and multiplies in the blood of many mammals. Trypanosomes evade the immune system by altering their surface structure which is dominated by a layer of a variant surface glycoprotein (VSG). Although invariant surface proteins exist, they are inaccessible to the humoral immune response. Using a combinatorial selection method in conjunction with live trypanosomes as the binding target, we show that short RNA ligands (aptamers) for constant surface components can be isolated. We describe the selection of three classes of RNA aptamers that crosslink to a single 42 kDa protein located within the flagellar pocket of the parasite. The RNAs associate rapidly and with high affinity. They do not discriminate between two different trypanosome VSG variant strains and, furthermore, are able to bind to other trypanosome strains not used in the selection protocol. Thus, the aptamers have the potential to function as markers on the surface of the extracellular parasite and as such they might be modified to function as novel drugs against African trypanosomiasis.
Homann
M
M
Laboratorium für Molekulare Biologie, Genzentrum der Ludwig-Maximilians-Universität München, Am Klopferspitz 18a, 82152 Martinsried, Germany.
Göringer
H U
HU
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D017404:In Situ Hybridization, Fluorescence; D008024:Ligands; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid; D014346:Trypanosoma brucei brucei / Q000378:metabolism*
D017931:DNA Primers; D008024:Ligands; D016601:RNA-Binding Proteins; D012313:RNA