Electrochemical detection of the oligomerization of PB1-F2 influenza A virus protein in infected cells.

PB1-F2 is a nonstructural accessory protein of Influenza A virus described to enhance the mortality and the morbidity of the virus in a host-dependent manner. In this work, an electrochemical biosensor based on an immunodetection system was developed to follow the oligomerization of PB1-F2 during the viral cycle. The immunosensor was based on conductive polypyrrole modified with ferrocenyl groups as a redox marker for enhancing signal detection. Antibodies specific for monomeric or oligomeric PB1-F2 forms were immobilized on polypyrrole matrix via biotin/streptavidin layer. We demonstrated that this electrochemical biosensor sensitively detects PB1-F2 in both conformational forms. The linear range extends from 5 nM to 1.5 μM and from 5 nM to 0.5 μM for monomeric and oligomeric PB1-F2, respectively. The calculated limit of detection was 0.42 nM for monomeric PB1-F2 and 16 nM for oligomers. The biosensor platform allows the detection and quantification of PB1-F2 in lysates of infected cells during viral cycle. We show that at early stages of viral cycle, PB1-F2 is mainly monomeric but switched to amyloid-like structures at a later stage of infection. The quantification of two protein structural forms points out that PB1-F2 expression profiles and kinetics of oligomerization are cell-type-dependent.