Exploring the potential of self‐assembling nanoparticles in displaying structurally defined antigens for vaccines development

To meet the growing need for medical interventions against infectious diseases, several vaccines containing isolated and highly purified antigenic proteins have been developed. Compared to traditional vaccines, they are safer but show a lower immunogenicity. To overcome the latter, the use of nanoparticles for the display of target antigens is a promising strategy [1]. Virus-like particles (VLPs) and protein nanoparticles (NPs), thanks to their repetitive and highly ordered structure, can present multiple copies of the target antigens allowing the potential induction of a potent B- and T-cell response [2]. This work is focused on (i) identification of NPs prone to genetic fusion to display protein antigen, (ii) development of a strategy for the epitope display and (iii) design and development of a polyvalent NP. Different NPs and VLPs were genetically fused to a meningococcal antigen. The Domain 3 of Group B Streptococcus pilus protein has been engineered with foreign epitopes allowing the display on a NP surface. Combining structural and computational biology each chimeric molecule has been designed and its 3D has been predicted. Computationally designed molecules were produced in Escherichia coli and biochemically and structurally characterized. By combining genetic fusion and chemical conjugation approaches, a polyvalent NP has been developed displaying simultaneously two different streptococcal antigens Results obtained show that particles can maintain their 3D structure when genetically fused with a foreign protein and they are able to correctly display the target antigen. The use of D3 allowed the identification of most immunogenic epitopes from unsoluble membrane antigens and their display on mI3 surface. Moreover, the in vivo study conducted with the polyvalent NP revealed that the use of the NP as scaffold increased the immunogenicity of both streptococcal antigens. In conclusion, this work represents a template strategy for the development of new effective NP-based vaccines against bacterial pathogens