Human Monoclonal Antibodies to Pandemic 1957 H2N2 and Pandemic 1968 H3N2 Influenza Viruses

Abstract

Investigation of the human antibody response to the 1957 pandemic H2N2 influenza A virus has been largely limited to serologic studies. We generated five influenza virus hemagglutinin (HA)-reactive human monoclonal antibodies (MAbs) by hybridoma technology from the peripheral blood of healthy donors who were born between 1950 and 1968. Two MAbs reacted with the pandemic H2N2 virus, two recognized the pandemic H3N2 virus, and remarkably, one reacted with both the pandemic H2N2 and H3N2 viruses. Each of these five naturally occurring MAbs displayed hemagglutination inhibition activity, suggesting specificity for the globular head domain of influenza virus HA. When incubated with virus, MAbs 8F8, 8M2, and 2G1 each elicited H2N2 escape mutations immediately adjacent to the receptor-binding domain on the HA globular head in embryonated chicken eggs. All H2N2-specific MAbs were able to inhibit a 2006 swine H2N3 influenza virus. MAbs 8M2 and 2G1 shared the V H 1-69 germ line gene, but these antibodies were otherwise not genetically related. Each antibody was able to protect mice in a lethal H2N2 virus challenge. Thus, even 43 years after circulation of H2N2 viruses, these subjects possessed peripheral blood B cells encoding potent inhibiting antibodies specific for a conserved region on the globular head of the pandemic H2 HA.

Heterosubtypic antibody recognition of the influenza virus hemagglutinin receptor binding site enhanced by avidity

“…Hydrophobic HCDR2s are the hallmark of V H 1-69 germ-line antibodies, such as the HA stem-targeted CR6261 (17,22) and F10 (23) antibodies. That a hydrophobic HCDR2 can enter the receptor binding site, as in the case of S139/1, raises the possibility that similar receptor binding site-targeted antibodies from the V H 1-69 germ line can be raised in humans (37). The S139/1 binding mode involves a tightly constrained network of residue contacts and conformations of the outer loops that compose the receptor binding site, including antigenic sites A, B, and D (7).…”

Hemagglutinin Stalk-Based Universal Vaccine Constructs Protect against Group 2 Influenza A Viruses

“…Importantly, this vaccination strategy also induced high titers of stalk-reactive antibodies against the H7 HA from the emerging Chinese H7N9 virus (10). Recently, broadly reactive anti-head antibodies have also been described in the literature (35)(36)(37), and it is theoretically possible that such antibodies are induced by the cHA vaccination regimen. However, we did not detect such antibodies in sera from cHA-immunized animals, suggesting that these antibodies are not induced significantly by this vaccine.…”

“…Broadly reactive anti-globular head antibodies have recently been described in the literature (35)(36)(37). Though rare in nature, these antibodies tend to recognize conserved regions of the receptor-binding site and recognize divergent globular head domains without closely following phylogenetic relatedness.…”

Chimeric Hemagglutinin Influenza Virus Vaccine Constructs Elicit Broadly Protective Stalk-Specific Antibodies

“…It is possible that a similar outcome could be achieved by using different vaccination schemes or employing other constructs that express conserved epitopes of influenza virus proteins (11,21,(29)(30)(31), including those within the receptor binding site (32,33) or the extracellular domain of the M2 protein (34). While we focused on a proof-of-principle experiment with group 1 influenza viruses, we believe that a similar approach could be employed for group 2 and influenza B viruses, leading to the development of a trivalent universal influenza virus vaccine.…”