VP1 Virus-like Particles Research Articles

Molecular cloning and expression of major structural protein VP1 of the human polyomavirus JC virus: formation of virus-like particles useful for immunological and therapeutic studies.

The major structural viral protein, VP1, of the human polyomavirus JC virus (JCV), the causative agent of progressive multifocal leukoencephalopathy (PML), was expressed by using recombinant baculoviruses. Recombinant VP1 formed virus-like particles (VLP) with the typical morphology of empty JCV capsids. Purified VP1 VLP bind to SVG, B, and T cells, as well as to monkey kidney cells. After binding, VP1 VLP were also internalized with high efficiency and transported to the nucleus. Immunization studies revealed these particles as highly immunogenic when administered with adjuvant, while immunization without adjuvant induced no immune response. VP1 VLP hyperimmune serum inhibits binding to SVG cells and neutralizes natural JCV. Furthermore, the potential of VP1 VLP as an efficient transporter system for gene therapy was demonstrated. Exogenous DNA could be efficiently packaged into VP1 VLP, and the packaged DNA was transferred into COS-7 cells as shown by the expression of a marker gene. Thus, VP1 VLP are useful for PML vaccine development and represent a potential new transporter system for human gene therapy.

Oligonucleotide and plasmid DNA packaging into polyoma VP1 virus-like particles expressed in Escherichia coli.

The drug delivery system described here is based on the properties of the capsoid or capsid-like structure resulting from the assembly of polyoma virus capsid protein VP1 expressed in Escherichia coli. The capsid protein VP1 was expressed as a fusion protein with a completely removable N-terminal His6 affinity tag. The pentameric morphology of the recombinant VP1 protein was confirmed by electron microscopy after affinity chromatography and factor Xa cleavage under conditions of low ionic strength. The self-assembly of VP1 capsoids can be induced from purified VP1 pentamers by increasing the ionic strength with (NH4)2SO4. These VP1 capsoid particles were packed in vitro with anti-sense oligonucleotides and plasmid DNA. The loading with DNA was pH-dependent. We observed the highest efficiency at pH 5. DNase I treatment of particles with encapsidated material showed that 37-55% of the bound oligonucleotides and fragments of 1.5-1.8 kb double-stranded DNA were protected against degradation.