Development of DNA Aptamers Against Leishmania infantum GP63 Protein for Therapeutic and Diagnostic Applications

Background/Objectives: Leishmaniasis is a disease affecting millions of people caused by parasites of the genus Leishmania. The GP63 protein of Leishmania infantum (LiGP63) is one of its major surface antigens and a main virulence factor, playing a role in the adhesion of extracellular promastigote stages to macrophages and in the survival of intracellular amastigotes. Methods: Here, DNA aptamers have been developed against LiGP63 through the systematic evolution of ligands by exponential enrichment. Results: Twenty individual aptamer sequences were characterized using confocal fluorescence microscopy and flow cytometry analysis, and 14 of them had targeting to more than 70% of L. infantum promastigotes with different subcellular localization patterns. Subsequent dot blot analyses narrowed down the selection to five candidates for further characterization through an aptamer-linked immobilized sorbent assay where it was possible to detect endogenous LiGP63 in L. infantum promastigote lysates. The five selected aptamers recognized the recombinant LiGP63 protein with binding affinities ranging from 0.3 to 2.1 µM. Promastigotes preincubated with LiGP63Apt-4, -27 and -28 exhibited a significantly reduced adhesion to and infection of RAW 264.7 macrophages. Moreover, when LiGP63Apt-4 and -28 were conjugated to liposomes, these two aptamers significantly enhanced the targeting to L. infantum promastigotes compared to plain liposomes. Conclusions: Given their improved stability and cost-effectiveness over antibodies, the aptamers evolved here represent promising candidates for new therapeutic and diagnostic approaches and for future nanoparticle-based drug delivery strategies in leishmaniasis.