Summary auto-generated
This study investigates the role of VP7, a surface protein of bluetongue virus (BTV), in binding to cellular receptors in Culicoides variipennis, the insect vector of bluetongue disease. Researchers compared binding of whole BTV particles and core particles (lacking outer proteins VP2 and VP5) to membrane preparations from C. variipennis adults, cultured vector cells (KC cells), and non-vector insects. Core particles and whole viruses bound more strongly to C. variipennis and KC cell membranes than to non-vector membranes. Using Western blot overlay assays and anti-idiotypic antibodies targeting VP7, the researchers identified a 23 kDa membrane protein present predominantly in vector insect membranes that specifically binds both viral particles and VP7. Virus precipitation experiments confirmed this protein co-purifies with BTV core and whole particles. The findings indicate that VP7, the exposed core surface protein, mediates virus attachment to vector cells through interaction with this specific receptor protein, suggesting VP7 plays a critical role in viral recognition and infection of the insect vector.
Key findings
- VP7 serves as the primary attachment protein for BTV binding to C. variipennis cellular membranes
- BTV core particles lacking outer proteins VP2 and VP5 bind more efficiently to vector cell membranes than intact virus particles, likely due to increased VP7 accessibility
- A 23 kDa membrane protein present predominantly in vector insect (C. variipennis) and derived cell cultures acts as a specific receptor for both BTV particles and VP7
- Membrane preparations from C. variipennis specifically reduce antibody binding to VP7, indicating direct receptor-VP7 interaction
- The VP7 receptor protein is largely absent from non-vector insect cell membranes, suggesting it may be a determinant of vector competence
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Abstract
The importance of VP7 of bluetongue virus (BTV) in the binding of BTV to membrane proteins of the BTV vector Culicoides variipennis was investigated. Core BTV particles, prepared from whole viruses, lacked outer proteins VP2 and VP5 and had VP7 exposed. More core particles and whole viruses bound to membrane preparations of adults of C. variipennis and KC cells, which were cultured from this vector insect, than to membrane preparations of Manduca sexta larvae. More core particles than whole viruses bound to membrane preparations of adults of C. variipennis and KC cells. Polyclonal anti-idiotypic antibodies (anti-Id), which were made against an antigen-combining region of an anti-BTV-10 VP7 antibody and functionally mimicked VP7, bound more to the membrane preparations of adults of C. variipennis and KC cells, and less to cytosol preparations. In Western overalay analysis, the Culicoides plasma membrane preparation reduced binding of an anti-VP7 monoclonal antibody to VP7. Whole and core BTV particles and the anti- Id bound to a membrane protein with a molecular mass of 23 kDa that was present predominantly in membrane preparations of adults of C. variipennis and KC cells. This protein was present in much lower concentrations in membrane preparations of C6/36 and DM-2 insect cells.