Identification of Dominant Antibody-Dependent Cell-Mediated Cytotoxicity Epitopes on the Hemagglutinin Antigen of Pandemic H1N1 Influenza Virus

Abstract

c Antibody-dependent cell-mediated cytotoxicity (ADCC) bridges innate and adaptive immunity, and it involves both humoral and cellular immune responses. ADCC has been found to be a main route of immune protection against viral infections in vivo. Hemagglutinin (HA) of influenza virus is highly immunogenic and considered the most important target for immune protection. Several potent cross-reactive HA-specific neutralizing monoclonal antibodies (MAbs) have been reported, and their conserved neutralizing epitopes have been revealed, but there has been no report so far about ADCC epitopes on HA. Here we identified two dominant ADCC epitopes, designated E1 (amino acids [aa] 92 to 117) and E2 (aa 124 to 159), on HA of pandemic H1N1 influenza virus by epitope mapping of convalescent-phase plasma IgG antibodies from six H1N1-infected human subjects in China that exhibited different levels of ADCC activity. The E1 and E2 ADCC epitopes overlapped with immunodominant epitopes of HA. Depletion of purified patient plasma IgG antibodies with EBY100 yeast cells expressing E1 or E2 decreased the ADCC activity of the IgG antibodies. E1 and E2 sequences were found to be highly conserved in H1N1 strains but less so in other subtypes of influenza A viruses. Our study may aid in designing immunogens that can elicit antibodies with high ADCC activity. Vaccine immunogens designed to include the structural determinants of potent broadly neutralizing antibodies and ADCC epitopes may confer comprehensive immune protection against influenza virus infection.

Antibody-Mediated Response of NKG2Cbright NK Cells against Human Cytomegalovirus

“…Few studies have evaluated the capacity of Abs produced along the anti-HCMV immune response to prevent viral replication by triggering NK cell-mediated recognition of HCMV-infected cells (38,39), despite previous evidences showing the contribution of NK cell-mediated ADCC to the control of other viruses (e.g., HIV and influenza) (40)(41)(42)(43)(44). Our study demonstrates that anti-HCMV Abs in immune sera can trigger an effective NK cell activation exceeding the low natural cytotoxicity levels against infected MRC5 cells.…”

Influenza-Specific Antibody-Dependent Cellular Cytotoxicity: Toward a Universal Influenza Vaccine

“…Recent studies by our group (36,43) and other investigators (52,76) described assays that measure NK cell activation following incubation of donor PBMCs with either (mAbs or polyclonal IgG) Ab-coated infected target cells or Ab-Ag complexes on coated plates. In our studies, we coated recombinant influenza HA proteins onto a 96-well plate, incubated them with serum or purified Ig, and added PBMCs from healthy donors.…”

Influenza virus A(H1N1)2009 antibody-dependent cellular cytotoxicity in young children prior to the H1N1 pandemic

“…These responses could be mediated by the same antibodies, although both HA1 and HA2 epitopes for ADCC antibodies have been reported (DiLillo et al, 2014;Jegaskanda et al, 2014b;Srivastava et al, 2013). The role of neutralizing and non-neutralizing Abs in effector cell activation is highly dependent on the affinity of these antibodies to the Fc gamma receptor.…”