Virus Like Particles (VLPs)
Virus Like Particles (VLPs) have been designed to overcome the problems associated with certain recombinant protein vaccines. Recombinant protein vaccines may elicit a poor immune response as a result of a poor presentation of the viral antigens to the immune system. This can be overcome to a certain extent through the addition of adjuvants, but perhaps another more attractive option would be to use Virus Like Particles. VLPs are an assembly of viral antigens such that they create a more authentic structure and conformation of the viral antigen.
VLPs have been shown to have significant potential in eliciting a stronger and more lengthy immune response than more traditional recombinant protein vaccines. Measurement of both particle size and state of aggregation as well as particle concentration is vital information in the characterization of such products. The NanoSight technique represents a very attractive option for quantifying and sizing VLPs directly in liquid suspension. The immune response to a preparation of VLPs will be indicative of the particle concentration as well as particle size and state of aggregation. More typical methods of quantification in vaccine development such as infectivity assays and qPCR cannot be used to quantify VLPs because they are (a) non infectious and (b) do not contain DNA ruling out infectivity assays and qPCR respectively.
Fig 1. Shows a number size distribution generated by the NanoSight instrument on a suspension of Virus Like Particles. High resolution number vs size distributions such as these allow the user to quantify the purity, size and concentration of a VLP preparation.