Elucidation of mammalian binding and entry of cowpea mosaic virus via surface vimentin; implications for nanotechnology and virus evolution

Cowpea mosaic virus (CPMV), a plant virus, is the type member of the Comovirus genus. Comoviruses are members of the larger picornavirus superfamily; for which the host range spans the plant and animal kingdoms and includes viruses such as poliovirus, coxsackievirus, and Theiler's virus. The ease of genetic and chemical manipulation of CPMV has led to its use as nanoscaffold for vaccines, antiviral therapeutics, targeted drug delivery, and vascular imaging. These applications have revealed that CPMV is rapidly internalized into endothelial cells following intravenous administration and that CPMV has systemic bioavailability after oral introduction in model systems. Herein we determined that a 54 kDa cell-surface protein is responsible for the interactions of CPMV with the mammalian cell surface through in vitro binding assays, flow cytometry evaluation of virion uptake, and characterization experiments. Through proteomic screens, ELISAs, use of a knockout cell line, and in vivo colocalization we identify the 54kD cell-surface protein as a surface-exposed form of the intermediate filament vimentin. We then further delineated which specific protein domains facilitate this interaction through binding assays, and identification of reactive vimentin cleavage fragments. Finally biosafety concerns of using CPMV in vivo are minimized through use of our developed ultraviolet-inactivation method that preserves mammalian cell reactivity and chemical addressability. These discoveries expand CPMV capabilities as a nanoscaffold, reveal a tool for understanding surface vimentin function, as well as provide an interesting window into the determinants of the picornavirus host range.