Abstract
Virus-like particles (VLPs) can be used as nano-carriers and antigen-display systems in vaccine development and therapeutic applications. Conjugation of peptides or whole proteins to VLPs can be achieved using different methods such as the SpyTag/SpyCatcher system. Here we investigate the conjugation of tandem Hepatitis B core (tHBcAg) VLPs and the model antigen GFP in vivo in Nicotiana benthamiana. We show that tHBcAg VLPs could be successfully conjugated with GFP in the cytosol and ER without altering VLP formation or GFP fluorescence. Conjugation in the cytosol was more efficient when SpyCatcher was displayed on tHBcAg VLPs instead of being fused to GFP. This effect was even more obvious in the ER, showing that it is optimal to display SpyCatcher on the tHBcAg VLPs and SpyTag on the binding partner. To test transferability of the GFP results to other antigens, we successfully conjugated tHBcAg VLPs to the HIV capsid protein P24 in the cytosol. This work presents an efficient strategy which can lead to time and cost saving post-translational, covalent conjugation of recombinant proteins in plants.
Highlights
Virus-like particles (VLPs) can be used as nano-carriers and antigen-display systems in vaccine development and therapeutic applications
Successful targeting of the ST/SC system to the endoplasmic reticulum (ER) might enable in vivo conjugation of VLPs and glycosylated antigens targeted to the ER
The SpyTag/SpyCatcher system is a powerful tool for the conjugation of VLPs to peptides or whole proteins for vaccine design and therapeutic approaches
Summary
Virus-like particles (VLPs) can be used as nano-carriers and antigen-display systems in vaccine development and therapeutic applications. The repetitive surface structure and a typical size range of 20–200 nm make VLPs highly immunogenic and they can induce a strong humoral and cellular immune response[1] They can be utilized as vaccines against the virus they are derived from or can be used as nano-carriers displaying foreign antigens or cell targeting ligands for vaccine or therapeutic approaches (as reviewed in[2,3,4]). The SpyTag/SpyCatcher strategy has been successfully used to conjugate different antigens to VLPs derived from bacteriophage A P20538, HBV surface a ntigen[39], potato virus X 40 or lentiviruses[41]. While the SpyTag/SpyCatcher system might enable improved antigen display, the in vivo conjugation in plants might offer a highly scalable, cheap and safe way for recombinant protein expression, avoiding in vitro conjugation and unnecessary purification steps. To investigate the possibility of using this technology to display glycosylated proteins, we localized the conjugation reaction of tHBcAg and GFP to the endoplasmic reticulum (ER)
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