228
T. Zhang et al.
The peptide-based phage display and the oligonucleotide-based aptamer techniques with high affinity to targets on the cell surface are the two powerful methods
in diagnosis. Particularly, phage display has been employed in the investigation
of pathogen–host interactions. In malaria, once inside into the liver, sporozoites
dividing in the bloodstream will infect the red blood cells (RBCs). The surface of
RBCs is covered by glycoprotein from which merozoite will be invading. Therefore,
glycoprotein is another malaria biomarker in molecule diagnosis. Alves et al. [98]
proposed a phage display assay for P. falciform glycoprotein detection from in vitro
to in vivo. To identify the molecular ligands of the glycoprotein, a phage display
cDNA library from a P. falciparum strain was used in panning assays against purified human glycoprotein or isolated RBCs. After several rounds of selection, several
parasite proteins that can specifically bind to glycoprotein and RBCs were identified,
including erythrocyte-binding ligand-1 (EBL-1). Moreover, the phage cDNA insert
bears the binding site for glycoprotein and EBL-1 (Table 8.6).
8.4.2 Schistosomiasis
Schistosomiasis is a major parasitic disease infected by blood flukes of the genus
Schistosoma. It affects the liver, mesentery and urogenital tract of infected individuals. WHO reported that schistosomiasis has affected over 240 million people in
low- and middle-income countries dated to 2018 [99]. Human schistosomiasis is
mostly caused by haematoidin (S. haematoidin), Schistosoma mansoni (S. mansoni)
and Schistosoma japonica (S. japonica). Among these, S. japonica is the major one
that occurs in Asia, particularly in China, Thailand and Indonesia [100]. S. japonica
ovulates Schistosoma eggs, which can be deposited in the host organs, causing the
symptoms of schistosomiasis such as granuloma and fibrosis [101]. Schistosomiasis
transmission starts from Schistosoma eggs discharged into water with the host feces.
In recent years, the global strategy for schistosomiasis has heavily focused on
the control of disease morbidity. The current gold standard diagnostic method for
schistosomiasis is the demonstration of schistosome eggs in the stool. However, the
sensitivity of the method is undesired. Antibody-based detection techniques may be
more sensitive and specific but the expenditure is relatively high [102].
Similar to antibodies, aptamers behave high-binding affinity as well as high
specificity. Compared to antibodies, aptamers can be manufactured with chemical
methods, so the cost is relatively acceptable. Long et al. [103] applied SELEX to
employ egg-based ssDNA aptamers and identified a panel of ssDNA aptamers specifically binding to schistosome eggs. Two aptamers LC6 and LC15, which exhibited
strong binding to and specific recognition of S. japonica eggs, were finally selected.
In particular, tissue imaging results revealed that LC15 could recognize S. japonica
eggs in liver tissues with a detection ratio of 80.5% (Fig. 8.9). The work will facilitate
the development of an effective tool for schistosomiasis diagnosis.
T. Zhang et al.
The peptide-based phage display and the oligonucleotide-based aptamer techniques with high affinity to targets on the cell surface are the two powerful methods
in diagnosis. Particularly, phage display has been employed in the investigation
of pathogen–host interactions. In malaria, once inside into the liver, sporozoites
dividing in the bloodstream will infect the red blood cells (RBCs). The surface of
RBCs is covered by glycoprotein from which merozoite will be invading. Therefore,
glycoprotein is another malaria biomarker in molecule diagnosis. Alves et al. [98]
proposed a phage display assay for P. falciform glycoprotein detection from in vitro
to in vivo. To identify the molecular ligands of the glycoprotein, a phage display
cDNA library from a P. falciparum strain was used in panning assays against purified human glycoprotein or isolated RBCs. After several rounds of selection, several
parasite proteins that can specifically bind to glycoprotein and RBCs were identified,
including erythrocyte-binding ligand-1 (EBL-1). Moreover, the phage cDNA insert
bears the binding site for glycoprotein and EBL-1 (Table 8.6).
8.4.2 Schistosomiasis
Schistosomiasis is a major parasitic disease infected by blood flukes of the genus
Schistosoma. It affects the liver, mesentery and urogenital tract of infected individuals. WHO reported that schistosomiasis has affected over 240 million people in
low- and middle-income countries dated to 2018 [99]. Human schistosomiasis is
mostly caused by haematoidin (S. haematoidin), Schistosoma mansoni (S. mansoni)
and Schistosoma japonica (S. japonica). Among these, S. japonica is the major one
that occurs in Asia, particularly in China, Thailand and Indonesia [100]. S. japonica
ovulates Schistosoma eggs, which can be deposited in the host organs, causing the
symptoms of schistosomiasis such as granuloma and fibrosis [101]. Schistosomiasis
transmission starts from Schistosoma eggs discharged into water with the host feces.
In recent years, the global strategy for schistosomiasis has heavily focused on
the control of disease morbidity. The current gold standard diagnostic method for
schistosomiasis is the demonstration of schistosome eggs in the stool. However, the
sensitivity of the method is undesired. Antibody-based detection techniques may be
more sensitive and specific but the expenditure is relatively high [102].
Similar to antibodies, aptamers behave high-binding affinity as well as high
specificity. Compared to antibodies, aptamers can be manufactured with chemical
methods, so the cost is relatively acceptable. Long et al. [103] applied SELEX to
employ egg-based ssDNA aptamers and identified a panel of ssDNA aptamers specifically binding to schistosome eggs. Two aptamers LC6 and LC15, which exhibited
strong binding to and specific recognition of S. japonica eggs, were finally selected.
In particular, tissue imaging results revealed that LC15 could recognize S. japonica
eggs in liver tissues with a detection ratio of 80.5% (Fig. 8.9). The work will facilitate
the development of an effective tool for schistosomiasis diagnosis.