Novel epitope-based diagnostic probes selected by phage display for the serological detection of HDV

BACKGROUND Hepatitis delta virus (HDV) is associated with the worst prognosis among viral hepatitis infections; however, it remains largely underdiagnosed, particularly in endemic developing regions, underscoring the need for new, accessible serological methods for large-scale screening. OBJECTIVES To develop HDV-mimetic molecules using phage display for application in immunodiagnostic platforms. METHODS HDV-mimetic peptides were selected via phage display biopanning, sequenced and screened by phage-enzyme-linked immunosorbent assay (ELISA). Based on the sequences of these peptides, a recombinant protein (rHDV) was constructed and employed in an ELISA. The test was validated using 87 anti-HDV-positive samples and 93 hepatitis B virus (HBV) control samples collected from a public diagnostic laboratory in the Amazon region. Statistical analyses were performed to evaluate the diagnostic performance of the synthetic peptides and the recombinant protein. FINDINGS Overall, rHDV exhibits a sensitivity of 74.71%, specificity of 97.85%, and area under the curve (AUC) of 0.8906. In HDV ribonucleic acid (HDV RNA)-positive patients, diagnostic performance improved, with a sensitivity of 88.0%, specificity of 98.92%, and AUC of 0.96. MAIN CONCLUSIONS These findings highlight that the rHDV protein used in ELISA effectively discriminated HDV-infected individuals from patients monoinfected with hepatitis B. This demonstrates the potential of rHDV as an effective, rapid, and low-cost tool for HDV detection for broader HDV screening.