Broadly Reactive Anti-Respiratory Syncytial Virus G Antibodies from Exposed Individuals Effectively Inhibit Infection of Primary Airway Epithelial Cells

Abstract

Respiratory syncytial virus (RSV) causes severe respiratory disease in young children. Antibodies specific for the RSV prefusion F protein have guided RSV vaccine research, and in human serum, these antibodies contribute to Ͼ90% of the neutralization response; however, detailed insight into the composition of the human B cell repertoire against RSV is still largely unknown. In order to study the B cell repertoire of three healthy donors for specificity against RSV, CD27 ϩ memory B cells were isolated and immortalized using BCL6 and Bcl-xL. Of the circulating memory B cells, 0.35% recognized RSV-A2-infected cells, of which 59% were IgAexpressing cells and 41% were IgG-expressing cells. When we generated monoclonal B cells selected for high binding to RSV-infected cells, 44.5% of IgGexpressing B cells and 56% of IgA-expressing B cells reacted to the F protein, while, unexpectedly, 41.5% of IgG-expressing B cells and 44% of IgA expressing B cells reacted to the G protein. Analysis of the G-specific antibodies revealed that 4 different domains on the G protein were recognized. These epitopes predicted cross-reactivity between RSV strain A (RSV-A) and RSV-B and matched the potency of antibodies to neutralize RSV in HEp-2 cells and in primary epithelial cell cultures. G-specific antibodies were also able to induce antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis of RSV-A2-infected cells. However, these processes did not seem to depend on a specific epitope. In conclusion, healthy adults harbor a diverse repertoire of RSV glycoprotein-specific antibodies with a broad range of effector functions that likely play an important role in antiviral immunity.IMPORTANCE Human RSV remains the most common cause of severe lower respiratory tract disease in premature babies, young infants, the elderly, and immunocompromised patients and plays an important role in asthma exacerbations. In developing countries, RSV lower respiratory tract disease has a high mortality. Without an effective vaccine, only passive immunization with palivizumab is approved for prophylactic treatment. However, highly potent RSV-specific monoclonal antibodies could potentially serve as a therapeutic treatment and contribute to disease control and mortality reduction. In addition, these antibodies could guide further vaccine development. In this study, we isolated and characterized several novel antibodies directed at the RSV G protein. This information can add to our understanding and treatment of RSV disease.

Structures of respiratory syncytial virus G antigen bound to broadly neutralizing antibodies

“…Indeed, nearly half of RSV-specific human memory B cells target the G glycoprotein (24) and more than half of the anti-G antibodies in human serum target specifically the RSV G CCD (35). Consistent with these studies, 17 out of 21 isolated human anti-G mAbs have linear epitopes that map to this region (22, 24) (Fig. S5).…”

Respiratory virus-induced heterologous immunity

“…Cross-reactivity of human antibodies has also been detected between two epitopes of the G-protein of RSV-A and RSV-B. Such human IgG antibodies showed neutralizing effects against both viruses in HEp-2 cell culture [75]. Furthermore, human mAbs, cross-neutralizing RSV and human metapneumovirus (HMPV), have been identified [15,78].…”

“…In response to RSV infection, the anti-fusion (F) protein and anti-attachment glycoprotein (G) are the main antibodies produced [74,75]. CD8 + T cells contribute to RSV clearance in murine models [74] and lung CD8 + Trm have protective effects in human RSV challenge [37].…”

Respiratory virus-induced heterologous immunity

“…Cross-reactivity of human antibodies has also been detected between two epitopes of the G protein of RSV-A and RSV-B. Such human IgG antibodies showed neutralizing e ects against both viruses in HEp-2 cell culture [75]. Furthermore, human mAbs, cross-neutralizing RSV and human metapneumovirus (HMPV), have been identi ed [15,78].…”

“…In response to RSV infection, the anti-fusion (F) protein and anti-attachment glycoprotein (G) are the main antibodies produced [74,75]. CD8 + T cells contribute to RSV clearance in murine models [74] and lung CD8 + T rm have protective e ects in human RSV challenge [37].…”