New broad-spectrum anti-Flavivirus human antibodies with Zika virus-neutralizing potential

Abstract

Flavivirus infections show recurrent outbreaks and can be responsible for disease complications such as Hemorrhagic Dengue Fever and Congenital Zika Virus Syndrome. Effective therapeutic interventions are still a challenge. Antibodies can provide significant protection, although antibody response may fail due to ADE (Antibody-Dependent Enhancement) reactions or immune escape mutations. To generate effective neutralizing antibodies, the choice of the target antigen is a crucial part of the process. Human anti-Flavivirus antibodies were selected from a combinatorial library displayed on a phage surface. The antibodies were selected against a mimetic peptide based on the fusion loop region in Domain II of the protein E, which is highly conserved among different Flavivirus. Four rounds of selection were performed using the synthetic peptide in two strategies: the first was using acidic elution of bound phages, and the second was applying a competing procedure. After panning, the selected VH and VL domains were determined by combining NGS and bioinformatic approaches. Three different human monoclonal antibodies were expressed as scFvs and further characterized. All showed binding capacity to Zika (ZIKV), Yellow Fever (YFV), and Dengue (DENV) viruses. Two of these antibodies, AZ1p and AZ6m, could neutralize the ZIKV infection in a PRNT assay. These new antibodies have the potential to be used in therapeutic intervention against different Flavivirus illnesses and, due to the conservation of the fusion loop region, they may be resistant to scape mutations. Author summaryThe central idea of this work is to present a possible unique therapeutic approach to combat different diseases that cause health problems annually, such as Dengue and yellow fever infections and Zika congenital syndromes. The viruses that cause these diseases, of the Flavivirus genus, typically have disease amplification reactions and evasion mechanisms of the immune response that hinder the success of specific therapies and vaccines and require new forms of effective and safe treatments. We have developed new neutralizing human antibodies so that they bind to a highly conserved region of Flavivirus, called the fusion loop, and in such a way as to avoid adverse effects associated with anti-Flavivirus antibodies. We showed that the antibodies have high cross-reactivity against different Flaviviruses and we exemplified their neutralizing capacity for Zika virus infection in an ex vivo assay. New monoclonal antibodies such as those presented here may contribute to the control of important tropical diseases in a safer and more efficient way.