[en] Human Toxocariasis (HT) is a zoonotic disease caused by the migration
of the larval stage of the roundworm Toxocara canis in the human host.
Despite of being the most cosmopolitan helminthiasis worldwide, its
diagnosis is elusive. Currently, the detection of specific immunoglobulins
IgG against the Toxocara Excretory-Secretory Antigens (TES), combined
with clinical and epidemiological criteria is the only strategy to diagnose
HT. Cross-reactivity with other parasites and the inability to distinguish
between past and active infections are the main limitations of this
approach. Here, we present a sensitive and specific novel strategy to
detect and quantify TES, aiming to identify active cases of HT. High
specificity is achieved by making use of nanobodies (Nbs), recombinant
single variable domain antibodies obtained from camelids, that due to
their small molecular size (15kDa) can recognize hidden epitopes not
accessible to conventional antibodies. High sensitivity is attained by the
design of an electrochemical magnetosensor with an amperometric readout
with all components of the assay mixed in one single step. Through
this strategy, 10-fold higher sensitivity than a conventional sandwich
ELISA was achieved. The assay reached a limit of detection of 2 and15
pg/ml in PBST20 0.05% or serum, spiked with TES, respectively. These
limits of detection are sufficient to detect clinically relevant toxocaral
infections. Furthermore, our nanobodies showed no cross-reactivity
with antigens from Ascaris lumbricoides or Ascaris suum. This is to our
knowledge, the most sensitive method to detect and quantify TES so far,
and has great potential to significantly improve diagnosis of HT. Moreover,
the characteristics of our electrochemical assay are promising for the
development of point of care diagnostic systems using nanobodies as a
versatile and innovative alternative to antibodies. The next step will be the
validation of the assay in clinical and epidemiological contexts.
Disciplines :
Biotechnology
Author, co-author :
Morales Yánez, Francisco Javier ; Vrije Universiteit Brussel - VUB > aboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
Trashin, Stanislav; Universiteit Antwerpen - UA > Department of Chemistry > AXES Research Group
Hermy, Marie; Institute of Tropical Medicine Antwerp > Department of Biomedical Sciences > Unit of Medical Helminthology
Sariego, Idalia; Institute of Tropical Medicine Pedro Kouri > Department of Parasitology
De Wael, Karolien; Universiteit Antwerpen - UA > Department of Chemistry > AXES Research Group
Polman, Katja; Institute of Tropical Medicine Antwerp > Department of Biomedical Sciences > Unit of Medical Helminthology
