Semisynthetic Viral Inhibitor for Light Control of the MHC I Peptide Loading Complex.

The immune system detects virally or malignantly transformed cells via peptide-loaded major histocompatibility complex class I (pMHC I) molecules on the cell surface. MHC I molecules are loaded with cargo peptides in the endoplasmic reticulum (ER) by the highly dynamic multiprotein peptide loading complex (PLC). Here, we developed a semisynthetic approach to generate a photocleavable immune modulator ICP47 of Herpes simplex virus. Using this nanotool, we revealed key mechanistic events of the purified PLC, such as peptide binding and translocation coupled to ATP hydrolysis, triggered by light. We established a single-organelle flow cytometry assay to monitor light-controlled activation of the antigen processing machinery in native ER membranes. This photochemical modulation opens new opportunities for a comprehensive mechanistic analysis of the antigen processing machinery in vitro and native membrane environment.

Novel ssRNA phage VLP platform for displaying foreign epitopes by genetic fusion.

Virus-like particles (VLPs) can be used as efficient carriers of various antigens and therefore serve as attractive tools in vaccine development. Although VLPs of different viruses can be used, VLPs of ssRNA phages have convincing advantages due to their unique properties, including efficient protein production in bacterial and yeast expression systems, low production cost and easy and fast purification. Currently, the range of ssRNA phage VLPs is limited. In particular, this is true for VLPs that tolerate insertions at the N- and C-termini of the coat protein. It is therefore necessary to find new alternatives within the known ssRNA phage VLP range. From previous studies, we found approximately 80 new VLPs forming ssRNA phage coat proteins. In the current study, we attached a model peptide to the N- and C-termini of coat proteins. As a model peptide, we used a triple repeat of 23 N-terminal residues of the ectodomain of the influenza M2 protein, used previously in the development of the flu vaccine. Examining 43 novel phage coat proteins for the ability to form chimeric VLPs, we found ten new promising candidates for further vaccine design, five of which were tolerant to insertions at both the N- and C-termini. Furthermore, we demonstrate that most of the chimeric VLPs have good antigenic properties as judged from their reactivity with anti-M2 antibodies.