A viral envelope is the outermost layer of the virus, consist of the glycoproteins. It serves to bind the receptor on the host’s cell membrane. When desired, the virus can be enveloped with a desired protein (so called pseudo-typing). The glycoproteins that able to maintain a viral particle structure, can be used as that virus’s envelope proteins. So not all proteins can be serves as envelope protein for a given virus type.
Gentarget’s Lentivirus-Like Particles (VLP):
Gentarget developed the virus-like particle product line as different pseudo-typed lentiviral particles. They are pseudo-typed with a desired envelope protein at its surface. It is packaged with a report (GFP or Luciferase) or just a non-sense Null-sequence as virion core. Such VLP are non-replicative, non-pathogenic and non-infectious to mammalian cells, or only infect the specific cell types that containing the corresponding receptor to the pseudo-typed envelope protein. If the mammalian cells can be successfully infected with VLP, it may express its GFP or Luciferase core depend upon the properties of the pseudo-type envelope protein. However, more often, the lentiviral-like-particles are used to present the surface enriched envelope protein.
Why use VLP?
1) Effective presentation of a specific viral antigen or Mimic viral Structure (Immunization and antibody Screening by ELISA):
Lenti-Virus-Like Particles (VLP) are more representative of how a specific virus antigen in vivo, mimic native exposed epitopes. The specific virus antigen is presented as the VLP’s surface envelope in high density, and easier access to immune response. They are highly immunogenic and more effectively activate the immune response. Therefore, the most effective antibodies can be raised from the VLP. So VLP can are often used as the more representative antigens or immunogen, for antibody development and validation, or for R&D immunoassays, vaccine research.
The VLPs are premade with high density of surface envelope protein, ready to use, no need to purify the antigen. You simply coat the VLP as antigen, onto wells in ELISA plate, for its antibody / vaccine detection or validation.
2) Targeted delivery:
VLPs are a target delivery of the report (here, GFP or Luciferase) to specific cells that contain the corresponding receptors to the VLP’s envelope protein.
3) Vaccine research:
VLP can be used as in platform for high through-put research in vaccine candidates. The customized VLPs resemble viruses with a specific coat protein, presented in higher density per particles with 3-dimensional conformation, such as VLPs for HBV, HPV, CA16, EV71 poliovirus, SARS-CoV virus, Zika virus, Ebola virus, and much more.