Sensitive detection of influenza a virus based on a CdSe/CdS/ZnS quantum dot-linked rapid fluorescent immunochromatographic test.

Prevention is the most effective management strategy for influenza A infection in humans. In this study, we developed a CdSe/CdS/ZnS quantum dot (QD) fluorescent dye for rapid and sensitive detection of two common subtypes (H1N1 and H3N2) of influenza A virus, and examined its utility. CdSe/CdS/ZnS QD was conjugated with antibody (Ab) after conjugation with latex, making QD conjugate of QD + Latex + Ab. A stable photoluminescence of QD conjugate and advantage of CdSe/CdS/ZnS QD used was characterized in this study. The performance of a rapid fluorescent immunochromatographic test (FICT) employing QD conjugate (QD-FICT) in detecting influenza A/H1N1 was 8-fold and 64-fold higher than that of a europium nanoparticle-based FICT and a rapid diagnostic test (RDT; Standard Diagnostics BIOLINE Influenza A/B), respectively. For influenza A/H3N2, QD-FICT showed 8-fold and 128-fold higher performance than europium nanoparticle-based FICT and RDT, respectively. In clinical evaluations, QD-FICT showed 93.75% clinical sensitivity [45/48; 95% confidence interval (95% CI): 82.80-98.69], 100% clinical specificity (117/117; 95% CI: 96.90-100.00), and strong correlation (kappa; 0.98) with rRT-PCR (20 ≤ Ct ≤ 40). Europium nanoparticle-linked FICT showed 79.17% clinical sensitivity (38/48; 95% CI: 65.01-89.53) and 100% clinical specificity (117/117; 95% CI: 96.90-100.00), whereas RDT showed 77.08% sensitivity (37/48; 95% CI: 62.69-87.97), 100% specificity (117/117; 95% CI: 96.90-100.00), and reasonably good correlation with rRT-PCR (kappa; 0.93). Water-soluble QDs can therefore be used as an effective material for developing fluorescent diagnostic systems for rapid detection of human influenza A virus in clinical specimens.

Peptide Aptamer of Complementarity-determining Region to Detect Avian Influenza Virus.

Despite significant progress in the development of diagnostic methods for influenza, avian influenza (AI) infection continues to represent a substantial threat to human health. Among the subtypes of AI, H5 influenza is highly infectious to animals and humans; however, there are no reliable H5 subtype-specific diagnostic systems owing to a scarcity of H5 subtype-specific detection elements. In this study, a new peptide aptamer (P1:KASGYTFTSF) was developed to recognize the H5 viral subtype using an in silico bioinformatics approach for predicting complementarity-determining regions (CDRs), and the aptamer was evaluated by immunoassays. The three-dimensional structure of influenza hemagglutinin (HA) and the peptide were used in a molecular docking study, and the peptide was compared to the epitope-derived peptide aptamer (H5-P2:KPNGAINF). Interactions between the peptides and the virus were then assessed by fluorescence-linked sandwich immunosorbent assay (FLISA), immunofluorescence staining assay (IFA), and rapid fluorescent immunochromatographic assay (FICT). P1 and H5-P2 both significantly detected H5N3 at 15.6 HAU/mL (P < 0.05), and P1 detected the virus more effectively (P < 0.05), consistent with the docking result. An optical image of the peptide recognizing an H5N3-infected cell was acquired by IFA, and was consistent with the antibody-linked IFA result. FICT employing the peptide showed the ability for H5 subtype-specific diagnosis, with 2-fold higher performance than that of a conventional, antibody-linked rapid test. This work shows the potential of a CDR-predicted peptide aptamer as a probe for immunological assays that can specifically recognize AI virus.