COVID-19 and SARS-CoV-2 update from Immunopaedia.org.za.
Majority of (direct) SARS-CoV-2 diagnostics either detect nucleic acid or viral antigens in nasal or oral swabs, however, these diagnostics are most useful within the first three weeks of the onset of symptoms when most individuals have detectable viral burden. Antibody testing helps to confirm post-infections and are important for epidemiological studies. In this study, Garcia-Cordero’s lab have designed an indirect immunoassay microfluidic chip that can detect the presence of circulating IgM and IgG against main SARS-CoV-2 antigens in an automated high-throughput system.
The microdevice (Figure 1) detects circulating antibodies against of Spike (S), S1 subunit (S1), the Receptor Binding Domain (RBD), and Nucleocapsid (N) simultaneously and in an independent manner operated by microvalves which creates microchambers. The microdevices uses only 6 mL of serum to detect the presence of anti-SARS-Cov-2 antibodies from up to 50 samples (in one run) in less than 3 hours with a limit of detection comparable to an ELISA and a high sensitivity (90-95%) and specificity (88-94%). Authors report that “the accuracy of the assay increased to 100% when analyzing samples acquired between 20-30 days after symptom onset, consistent with other reports”. This is not surpising because its measuring antibody immunity which requires time to develop, especially for IgG.
Current authorized antibodies test is still expensive for some low- and middle-income countries. Thus, this kind of microdevices can be quickly applied to monitor the adaptative responses naturally or induced by the upcoming vaccines in with a very low cost due the reduced reagents volume in massive qualitative and semi-quantitative screenings.
Journal Article: Rodriguez-Moncayo et al. 2020. A high-throughput multiplexed microfluidic device for COVID-19 serology assays. Lab on a Chip