Broadly Reactive Nanobody Targeting the H3 Hemagglutinin of the Influenza A Virus.

Monoclonal antibodies and recombinant antibody fragments are a very promising therapeutic tool to combat infectious diseases. Due to their unique paratope structure, nanobodies (VHHs) hold several advantages over conventional monoclonal antibodies, especially in relation to viral infections. Influenza A viruses (IAVs) remain a major threat to public health. The hemagglutinin (HA) protein is the main protective and immunodominant antigen of IAVs. In this study, three broadly reactive nanobodies (D9.2, E12.2, and D4.2) to H3N2 influenza strains were isolated and Fc-fusion proteins (VHH-Fcs) were obtained and characterized in vitro. This modification improved the nanobodies' binding activity and allowed for their interaction with a wider range of strains. The D9.2-Fc antibody showed a 100% protection rate against mortality in vivo in a mouse lethal model. Furthermore, we demonstrated that the observed protection has to do with Fc-FcγR interactions. These results indicate that D9.2-Fc can serve as an effective antiviral agent against the H3N2 influenza infection.

Construction of a pIX-modified Adenovirus Vector Able to Effectively Bind to Nanoantibodies for Targeting.

Current targeting strategies for genetic vectors imply the creation of a specific vector for every targeted receptor, which is time-consuming and expensive. Therefore, the development of a universal vector system whose surface can specifically bind molecules to provide efficient targeting is of particular interest. In this study, we propose a new approach in creating targeted vectors based on the genome of human adenovirus serotype 5 carrying the modified gene of the capsid protein pIX (Ad5-EGFP-pIX-ER): recombinant pseudoadenoviral nanoparticles (RPANs). The surfaces of such RPANs are able to bind properly modified chimeric nanoantibodies that specifically recognize a particular target antigen (carcinoembryonic antigen (CEA)) with high affinity. The efficient binding of nanoantibodies (aCEA-RE) to the RPAN capsid surfaces has been demonstrated by ELISA. The ability of the constructed vector to deliver target genes has been confirmed by experiments with the tumor cell lines A549 and Lim1215 expressing CEA. It has been shown that Ad5-EGFP-pIX-ER carrying aCEA-RE on its surface penetrates into the tumor cell lines A549 and Lim1215 via the CAR-independent pathway three times more efficiently than unmodified RPAN and Ad5-EGFP-pIX-ER without nanoantibodies on the capsid surface. Thus, RPAN Ad5-EGFP-pIX-ER is a universal platform that may be useful for targeted gene delivery in specific cells due to "nanoantibody-modified RPAN" binding.