Figure 4.

Lateral flow assays (LFAs) are ideal as point-of-care (POC) tools. In the case of nanobody-based LFAs, the test line consists of a printed line of highly specific nanobodies (Nbs) that can capture their target even in the presence of host antibodies that bind the same antigen (Ag). This can be achieved due to the unique nature of heavy-chain camelid antibodies (HcIgG) that bind their target in the absence of the light chain that is present in conventional antibodies (IgG). Detection of a parasite Ag can be done using a gold-conjugated second sandwich Nb that is pre-incubated on the conjugation pad. At the point of sample application, the detection Nb will bind the target, and together they will migrate towards the printed capturing line. Sandwich formation and Ag accumulation will result in the development of a red line. A second control line is used to ensure the correct interpretation of the test results. Ag-detecting LFAs can be used as proof of infection, as well as a test of cure. This makes the format unique compared to antibody detecting LFAs, which measure ‘exposure’ rather than active infection.