Specific Monoclonal Antibodies Targeting Unique HA Epitopes Block H7N9 Influenza A Viral Replication

Computational design and improvement of a broad influenza virus HA stem targeting antibody

Broadly neutralizing antibodies (nAbs) are vital therapeutic tools to counteract both pandemic and seasonal influenza threats. Traditional strategies for optimizing nAbs generally rely on labor-intensive, high-throughput mutagenesis screens. Here, we present an innovative structure-based design framework for the optimization of nAbs, which integrates epitope-paratope analysis, computational modeling, and rational design approaches, complemented by comprehensive experimental assessment. This approach was applied to optimize MEDI8852, a nAb targeting the stalk region of influenza A virus hemagglutinin (HA). The resulting variant, M18.1.2.2, shows a marked enhancement in both affinity and neutralizing efficacy, as demonstrated both in vitro and in vivo. Computational modeling reveals that this improvement can be attributed to the fine-tuning of interactions between the antibody's side-chains and the epitope residues that are highly conserved across the influenza A virus HA stalk. Our dry-wet iterative protocol for nAb optimization presented here yielded a promising candidate for influenza intervention.

Preclinical animal models to evaluate therapeutic antiviral antibodies

Despite the availability of effective preventative vaccines and potent small-molecule antiviral drugs, effective non-toxic prophylactic and therapeutic measures are still lacking for many viruses. The use of monoclonal and polyclonal antibodies in an antiviral context could fill this gap and provide effective virus-specific medical interventions. In order to develop these therapeutic antibodies, preclinical animal models are of utmost importance. Due to the variability in viral pathogenesis, immunity and overall characteristics, the most representative animal model for human viral infection differs between virus species. Therefore, throughout the years researchers sought to find the ideal preclinical animal model for each virus. The most used animal models in preclinical research include rodents (mice, ferrets, …) and non-human primates (macaques, chimpanzee, ….). Currently, antibodies are tested for antiviral efficacy against a variety of viruses including different hepatitis viruses, human immunodeficiency virus (HIV), influenza viruses, respiratory syncytial virus (RSV), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and rabies virus. This review provides an overview of the current knowledge about the preclinical animal models that are used for the evaluation of therapeutic antibodies for the abovementioned viruses.

Identification of Unique and Conserved Neutralizing Epitopes of Vestigial Esterase Domain in HA Protein of the H9N2 Subtype of Avian Influenza Virus

The H9N2 subtype of avian influenza virus (AIV) has been reported to infect not only birds, but also humans. The hemagglutinin (HA) protein is the main surface antigen of AIV and plays an important role in the viral infection. For treatment strategies and vaccine development, HA protein has been an important target for the development of broadly neutralizing antibodies against influenza A virus. To investigate the vital target determinant cluster in HA protein in this work, HA gene was cloned and expressed in the prokaryotic expression vector pET28a. The spleen lymphocytes from BALC/c mice immunized with the purified recombinant HA protein were fused with SP2/0 cells. After Hypoxanthine-Aminopterin-Thymidine (HAT) medium screening and indirect ELISA detection, six hybridoma cell lines producing anti-HA monoclonal antibodies were screened. The gradually truncated HA gene expression and western blotting were used to identify their major locations in epitopes specific to these monoclonal antibodies. It was found that the epitopes were located in three areas: 112NVENLEEL119, 117EELRSLFS124, and 170PIQDAQ175. Epitope 112NVENLEEL119 has a partial amino acid crossover with 117EELRSLFS124, which is located in the vestigial esterase domain "110-helix" of HA, and the monoclonal antibody recognizing these epitopes showed the neutralizing activity, suggesting that the region 112NVENLEELRSLFS124 might be a novel neutralizing epitope. The results of the homology analysis showed that these three epitopes were generally conserved in H9N2 subtype AIV, and will provide valuable insights into H9N2 vaccine design and improvement, as well as antibody-based therapies for treatment of H9N2 AIV infection.