The rise of highly transmissible SARS-CoV-2 variants brings new challenges and concerns with vaccine efficacy, diagnostic sensitivity, and public health responses to end the pandemic. Widespread detection of variants is critical to inform policy decisions to mitigate further spread, and postpandemic multiplexed screening of respiratory viruses will be necessary to properly manage patients presenting with similar respiratory symptoms.
Researchers from Johns Hopkins University have developed a portable, magnetofluidic cartridge platform for automated polymerase chain reaction testing in <30 min. Cartridges are designed for multiplexed detection of SARS-CoV-2 with either identification of variant mutations or screening for Influenza A and B. Moreover, the platform can perform identification of B.1.1.7 and B.1.351 variants and the multiplexed SARS-CoV-2/Influenza assay using archived clinical nasopharyngeal swab eluates and saliva samples. This work illustrates a path toward affordable and immediate testing with potential to aid surveillance of viral variants and inform patient treatment.
Cartridge platform operation
A) Nasal swab eluate or saliva is injected directly into the cartridge with magnetic beads followed by sealing the cartridge and inserting it into the instrument. After magnetofluidic sample preparation and PCR, the instrument reports that the assay results on the built-in touchscreen within 30 min. B) Each PCR well contains two fluorescent probes in the FAM (green/left) or Cy5 (red/right) spectrum. Cartridges include a duplexed assay for the conserved N1 SARS-CoV-2 sequence and control RNA in the first well. The cartridge designed for detection of SARS-CoV-2 variants includes a duplexed PCR assay in the second well with probes spanning regions that contain deletions found in variants of concern. A lack of amplification in the second well indicates the presence of a mutation and can be used to classify the type of variant present. C) Cartridges designed for multiplexed detection of respiratory pathogens have a duplexed Influenza A and Influenza B PCR assay in the second well.