A NOVEL APPROACH TO UNRAVEL THE RESPIRATORY SYNCYTIAL VIRUS (RSV) PREFUSION F-PROTEIN FUNCTIONAL ANTIBODY REPERTOIRE IN ADULT HEALTHY DONORS

Respiratory syncytial virus (RSV) is the chief cause of low respiratory tract infection deaths in infants under 5 years of age. Since no vaccine is currently available, novel approaches are needed to support the development of new candidates. Herein, elements of the “Reverse Vaccinology 2.0” approach were used to unravel functional, genetic and structural features that characterize the effective adult human antibody response to RSV infection. The data presented in this thesis show that the majority of identified neutralizing antibodies (nAbs) recognize both RSV F-protein conformations (cross-binders) even if a preferential binding towards the prefusion (preF) was observed. Furthermore, the IGHV1 gene family was identified as predominant in the functional antibody response, despite different heavy chain gene rearrangements seem to better recognize specific epitope regions on the preF. Moreover, predominant gene derived-nAbs, showing high neutralization potency, were found to specifically recognize a defined epitope region placed between Site Ø, Site II and Site V on the preF surface. Finally, the co-crystal structure of preF bound to Pl2_E08, a predominant gene derived nAb belonging to the IGHV1-69 gene family, was determined. Structural data confirm what was previously observed in a competition assay and reveal an important epitope region that could play a pivotal role in eliciting nAbs against different RSV A strains and even human metapneumovirus (MPV). These findings identify a specific site of pathogen vulnerability and highlight the possibility to design novel strategies to target and expand predominant gene derived-nAbs. This approach could result in high protection against RSV and consequent reduction of the high burden brought by this pathogen.