Functionally-derivatized Nanoantibodies as novel tools for Giardia lamblia cyst detection.

Giardia lamblia (syn. intestinalis, duodenalis) is the causative agent of Giardiasis, a diarrheal disease of global medical importance, especially problematic in young children living in unhygienic, resource-constrained settings. Diagnostics of potential Giardia infections are generally done through classic light-microscopy stool examination. This is often insufficient, and ELISA-based fluorescence detection using costly proprietary reagents is employed. These reagents are often not affordable in contexts where they are needed the most, and this limits their use to resource-rich settings where Giardiasis is rarely problematic. To address these issues in medical equity while designing novel strategies to investigate the Giardia cyst wall, we report on the development and characterisation of alpaca derived single-domain antibodies, known as nanoantibodies, elicited against G. lamblia enriched cyst-wall preparations. We evaluated the effectiveness and binding capacity of twelve unique E. coli-produced recombinant nanoantibody sequences for Giardia cyst wall detection and provide proof of concept for the effectiveness and versatility of these protein domains.