Basically, our group is working on projects developing recombinant vaccine candidates based on VLPs (Virus-Like Particles). Expression systems (mostly E.coli) and purification procedures for large spectrum of different proteins, VLPs and their chimeric derivatives are systematically developed and different expression-purification conditions are compared for the best yield and outcome of particular target proteins and vaccine candidates. Also, relevant functional proteins are expressed and purified to the level suitable for chemical coupling to VLPs of RNA-phages and hepatitis B virus (HBV) core-antigen (HBcAg). Genetically modified chimeric VLPs displaying immunologically relevant epitopes of HBV, HCV, Rubella and other viruses are systematically investigated and characterized for stability on subunit and VLP level, and their immunological potential in mouse models is evaluated. For T-cell immunogenicity of VLP-based vaccine candidates, it is crucial to have the characterized nucleic acid material inside the capsids, therefore, HBc-VLPs of different structure (with variable nucleic acid binding capacity) and origin (using HBcAg from different HBV genotypes) are investigated in our group for packaging of immunomodulatory substances such as oligonucleotides, single- and double-stranded RNA for their T-cell inducing potential and biotechnological properties. To reach the goal, VLP purification protocols of extra-pure quality are developed for HBc antigen itself and its structural derivatives, based on dissociation of HBc VLPs to dimeric subunits with further reassociation in the presence or absence of target substances (nucleic acids, peptides, proteins), - in latter case, the VLPs are loaded with substances after their reconstruction from dimers. Ptrp based system, pET, pQE and pCold expression systems have been used in our facility to reach the goal – high level expression and yield of target proteins. Advanced protein purification systems are used for purification of VLPs and other target proteins.