Establishment and preliminary evaluation of an RT-ERA combined with CRISPR/Cas12a assay for detection of H5 and H7 influenza viruses.

Background/objectives: Novel influenza A viruses (NIAV) infection is a zoonotic acute respiratory disease. The H5N1 and H7N9 subtypes cause high mortality, posing major public health threats. This study aimed to establish rapid, field-deployable subtype-specific nucleic acid detection assays for H5 and H7 by integrating reverse-transcription enzymatic recombinase amplification (RT-ERA) with CRISPR/Cas12a. Two separate reactions are required per sample. Methods: Conserved hemagglutinin (H) sequences were retrieved from the NCBI database, and primers, probes, and crRNAs were designed using Primer Premier 5 and Primer-BLAST. The sensitivity of RT-ERA alone was compared with that of the ERA-CRISPR/Cas12a using serially diluted virus strain nucleic acid. The specificity was verified against other respiratory pathogens with similar clinical manifestations. Results: The optimal primers were F1R2 for H5 and F2R3 for H7. The limit of detection (LOD) of RT-ERA alone was 2.63×10³ copies/µL for H5 and 1.86×10³ copies/µL for H7; the ERA-CRISPR/Cas12a assay improved the LOD to 2.63×10¹ copies/µL for H5 and 1.86 copies/µL for H7, representing 100-fold and 1000-fold enhancements in sensitivity, respectively. Specificity testing showed that the assay exclusively detected H5N1 and H7N9 with no cross-reactivity to other tested pathogens. Conclusion: The ERA-CRISPR/Cas12a method exhibits enhanced sensitivity for H5 and H7 subtypes detection, along with high specificity, rapidity, and minimal equipment requirements. It offers a promising screening tool for NIAV infections.