A New Assay for Quantitative Determination of Pres1-Encoded Protein in Patients Infected with Hepatitis B and Delta Viruses

Author(s): Alessandra Biasiolo, Santina Quarta, Mariagrazia Ruvoletto, Pietro Guerra, Andrea Martini, Patrizia Pontisso

Background & Aims: The Pre-S1 protein of HBV is essential for the infectivity of both B and delta viruses and has been recently proposed as a useful prognostic tool in chronic HBV infection. To date, accurate quantitative methods for PreS1 testing are still lacking. Since PreS1 has a high binding affinity for SerpinB3, the aim of the study was to standardize and validate a new assay based on PreS1-SerpinB3 interaction.

Methods: An AlphaLISA® technology test, based on the interaction between PreS1-encoded protein and SerpinB3, was standardized. Validation was carried out by the assessment of PreS1 levels in serum of 51 HBV-infected patients (5 inactive carriers, 38 with chronic hepatitis, among which 36 were under antiviral treatment, 8 with HDV coinfection). As healthy controls, sera of 62 blood donors were used.

Results: Preliminary set-up experiments allowed us to define the PreS1 linear range of 0.12 to 7.7 µg/mL and the low detection limit of 0.013 µg/mL. The positivity rate and levels of PreS1 were significantly higher in untreated patients with chronic hepatitis B and in HDV patients than in treated patients with chronic hepatitis B, while none of the inactive HBV carriers was positive. No significant correlation between PreS1 levels and viral load was observed.

Conclusion: The developed AlphaLISA® assay is useful for PreS1 detection in serum in HBV and delta-infected patients and correlates with the HBV infection stage.