A fully human monoclonal antibody possesses antibody-dependent cellular cytotoxicity (ADCC) activity against the H1 subtype of influenza A virus by targeting a conserved epitope at the HA1 protomer interface

The Diversitab^TM system produces target specific high titer fully human polyclonal IgG immunoglobulins from transchromosomic (Tc) bovines shown to be safe and effective against multiple virulent pathogens in animal studies and Phase 1, 2 and 3 human clinical trials. We describe the functional properties of a human monoclonal antibody (mAb), 38C2, identified from this platform, which recognizes recombinant H1 hemagglutinins (HAs) and induces appreciable antibody-dependent cellular cytotoxicity (ADCC) activity in vitro. Interestingly, 38C2 monoclonal antibody demonstrated no detectable neutralizing activity against H1N1 virus in both hemagglutination inhibition and virus neutralization assays. Nevertheless, this human monoclonal antibody induced appreciable ADCC against cells infected with multiple H1N1 strains. The HA-binding activity of 38C2 was also demonstrated in flow cytometry using Madin-Darby canine kidney cells infected with multiple influenza A H1N1 viruses. Through further investigation with the enzyme-linked immunosorbent assay involving the HA peptide array and 3-dimensional structural modeling, we demonstrated that 38C2 appears to target a conserved epitope located at the HA1 protomer interface of H1N1 influenza viruses. A novel mode of HA-binding and in vitro ADCC activity pave the way for further evaluation of 38C2 as a potential therapeutic agent to treat influenza virus infections in humans.

Asprellcosides B of Ilex asprella Inhibits Influenza A Virus Infection by Blocking the Hemagglutinin- Mediated Membrane Fusion

Ilex asprella is routinely used in China as a traditional medicinal herb to treat influenza (Flu). However, its specific antiviral activity and underlying molecular mechanism have not yet been determined. In this study, we sought to determine the antiviral activity and mechanism of Asprellcosides B, an active component extracted from Ilex asprella, and used against the influenza A virus cell culture. We also performed a computer-assisted structural modeling analysis and carried out surface plasmon resonance (SPR) experiments in the hope of determining the viral target of Asprellcosides B. Results from our studies show that Asprellcosides B reduced virus replication by up to 63% with an IC50 of about 9 μM. It also decreased the low pH-induced and virus-mediated hemolysis by 71% in vitro. Molecular docking simulation analysis suggested a possible binding of Asprellcosides B to the hemagglutinin (HA), which was confirmed by a surface plasmon resonance (SPR) assay. Altogether, our findings demonstrate that Asprellcosides B inhibits the influenza A virus, through a specific binding to the HA, resulting in the blockade of the HA-mediated membrane fusion.