ABSTRACT
OBJECTIVE: Biometric identification techniques for pediatric use are limited. This investigation studied iris scanning in minors aged 1-4 in two exploratory studies in Belgium (n = 197) and Sierra Leone (n = 230), and in a subsequent clinical study in Sierra Leone (n = 635). Images of participants' irises were captured using a camera, while a survey assessed the ease of use with children. RESULTS: The image capture success rate per individual was high; 86.0% of the participants had ≥ 2 successful captures. Iris scan quality and surface were similar in all age groups and in the matching population database. When including feasibility in the analysis of minors aged 3-4, sensitivity and specificity were non-inferior compared to using the biometric of a guardian. However, the quality of iris scanning in minors aged 1-4 was worse than the iris scanning reference quality in adults. A mean total usability score of 1.55 ± 0.27 was calculated; a usability threshold of 1.45 is required for routine use. Overall, this technique is feasible in minors aged 3-4, replacing the use of guardian biometrics. Additional work is ongoing to improve this technique further, striving for uniformity from the age of 1.
Subject(s)
Algorithms , Biometric Identification/methods , Image Processing, Computer-Assisted/methods , Iris/diagnostic imaging , Adult , Belgium , Child, Preschool , Humans , Infant , Reproducibility of Results , Sierra LeoneABSTRACT
VAR2CSA stands today as the leading vaccine candidate aiming to protect future pregnant women living in malaria endemic areas against the severe clinical outcomes of pregnancy associated malaria (PAM). The rational design of an efficient VAR2CSA-based vaccine relies on a profound understanding of the molecular interactions associated with P. falciparum infected erythrocyte sequestration in the placenta. Following immunization of a llama with the full-length VAR2CSA recombinant protein, we have expressed and characterized a panel of 19 nanobodies able to recognize the recombinant VAR2CSA as well as the surface of erythrocytes infected with parasites originating from different parts of the world. Domain mapping revealed that a large majority of nanobodies targeted DBL1X whereas a few of them were directed towards DBL4ε, DBL5ε and DBL6ε. One nanobody targeting the DBL1X was able to recognize the native VAR2CSA protein of the three parasite lines tested. Furthermore, four nanobodies targeting DBL1X reproducibly inhibited CSA adhesion of erythrocytes infected with the homologous NF54-CSA parasite strain, providing evidences that DBL1X domain is part or close to the CSA binding site. These nanobodies could serve as useful tools to identify conserved epitopes shared between different variants and to characterize the interactions between VAR2CSA and CSA.
Subject(s)
Antigens, Protozoan/immunology , Cross Reactions/immunology , Protein Interaction Domains and Motifs/immunology , Single-Domain Antibodies/immunology , Amino Acid Sequence , Animals , Antigens, Protozoan/chemistry , Camelids, New World , Epitope Mapping , Epitopes/chemistry , Epitopes/immunology , Erythrocytes/parasitology , Female , Humans , Immunization , Kinetics , Molecular Sequence Data , Placenta , Pregnancy , Protein Binding , Protein Conformation , Recombinant Proteins/chemistry , Recombinant Proteins/immunology , Sequence AlignmentABSTRACT
The VAR2CSA protein has been closely associated with pregnancy-associated malaria and is recognized as the main adhesin exposed on the surface of Plasmodium falciparum-infected erythrocytes. Chondroitin sulfate A was identified as the main host receptor in the placenta. Single-domain heavy-chain camelid antibodies, more commonly called nanobodies, were selected and produced against the DBL6â-FCR3 domain of VAR2CSA. Crystals of two specific nanobodies, Nb2907 and Nb2919, identified as strong binders to DBL6â-FCR3 and the full-length VAR2CSA exposed on the surface of FCR3 P. falciparum-infected erythrocytes, were obtained. Crystals of Nb2907 diffract to 2.45â Å resolution and belong to space group C2 with unit-cell parameters a=136.1, b=78.5, c=103.4â Å, ß=118.8°, whereas Nb2919 crystals diffract to 2.15â Å resolution and belong to space group P43212 with unit-cell parameters a=b=62.7, c=167.2â Å.
Subject(s)
Antibodies, Protozoan/chemistry , Antigens, Protozoan/chemistry , Plasmodium falciparum/chemistry , Single-Domain Antibodies/chemistry , Amino Acid Sequence , Animals , Antibodies, Protozoan/genetics , Antibodies, Protozoan/isolation & purification , Antigens, Protozoan/immunology , Binding Sites , Camelids, New World/immunology , Crystallography, X-Ray , Erythrocytes/parasitology , Escherichia coli/chemistry , Escherichia coli/genetics , Models, Molecular , Molecular Sequence Data , Plasmodium falciparum/metabolism , Protein Structure, Secondary , Protein Structure, Tertiary , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Sequence Alignment , Sequence Homology, Amino Acid , Single-Domain Antibodies/genetics , Single-Domain Antibodies/isolation & purificationABSTRACT
Nanobodies are single chain antibodies that are uniquely produced in Camelidae, e.g. camels and llamas. They have the desirable features of small sizes (Mw < 14 kDa) and high affinities against antigens (Kd approximately nM), making them ideal as structural probes for biomedically relevant motifs both in vitro and in vivo. We have previously shown that nanobody binding to amyloidogenic human lysozyme variants can effectively inhibit their aggregation, the process that is at the origin of systemic amyloid disease. Here we report the NMR assignments of a new nanobody, termed NbSyn2, which recognises the C-terminus of the intrinsically disordered protein, human alpha-synuclein (aS), whose aberrant self-association is implicated in Parkinson's disease.
