title: Impact of Antibodies and Strain Polymorphisms on Cytomegalovirus Entry and Spread in Fibroblasts and Epithelial Cells.
abstract: Cytomegalovirus (CMV) entry into fibroblasts differs from entry into epithelial cells. CMV also spreads cell to cell and can induce syncytia. To gain insights into these processes, 27 antibodies targeting epitopes in CMV virion glycoprotein complexes, including glycoprotein B (gB), gH/gL, and the pentamer, were evaluated for their effects on viral entry and spread. No antibodies inhibited CMV spread in fibroblasts, including those with potent neutralizing activity against fibroblast entry, while all antibodies that neutralized epithelial cell entry also inhibited spread in epithelial cells and a correlation existed between the potencies of these two activities. This suggests that exposure of virions to the cell culture medium is obligatory during spread in epithelial cells but not in fibroblasts. In fibroblasts, the formation of syncytiumlike structures was impaired not only by antibodies to gB or gH/gL but also by antibodies to the pentamer, suggesting a potential role for the pentamer in promoting fibroblast fusion. Four antibodies reacted with linear epitopes near the N terminus of gH, exhibited strain specificity, and neutralized both epithelial cell and fibroblast entry. Five other antibodies recognized conformational epitopes in gH/gL and neutralized both fibroblast and epithelial cell entry. That these antibodies were strain specific for neutralizing fibroblast but not epithelial cell entry suggests that polymorphisms external to certain gH/gL epitopes may influence antibody neutralization during fibroblast but not epithelial cell entry. These findings may have implications for elucidating the mechanisms of CMV entry, spread, and antibody evasion and may assist in determining which antibodies may be most efficacious following active immunization or passive administration.IMPORTANCECytomegalovirus (CMV) is a significant cause of birth defects among newborns infectedin uteroand morbidity and mortality in transplant and AIDS patients. Monoclonal antibodies and vaccines targeting humoral responses are under development for prophylactic or therapeutic use. The findings reported here (i) confirm that cell-to-cell spread of CMV is sensitive to antibody inhibition in epithelial cells but not fibroblasts, (ii) demonstrate that antibodies can restrict the formationin vitroof syncytiumlike structures that resemble syncytial cytomegalic cells that are associated with CMV diseasein vivo, and (iii) reveal that neutralization of CMV by antibodies to certain epitopes in gH or gH/gL is both strain and cell type dependent and can be governed by polymorphisms in sequences external to the epitopes. These findings serve to elucidate the mechanisms of CMV entry, spread, and antibody evasion and may have important implications for the development of CMV vaccines and immunotherapeutics.
authors.affiliation: Virginia Commonwealth University, Richmond, Virginia, USA.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Cui
authors.affiliation: Merck & Co., Inc., Kenilworth, New Jersey, USA.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Freed
authors.affiliation: Merck & Co., Inc., Kenilworth, New Jersey, USA.
authors.forename: Dai
authors.identifier: http://orcid.org/0000-0001-5666-8622
authors.initials: D
authors.lastname: Wang
authors.affiliation: Merck & Co., Inc., Kenilworth, New Jersey, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Qiu
authors.affiliation: Merck & Co., Inc., Kenilworth, New Jersey, USA.
authors.forename: Fengsheng
authors.initials: F
authors.lastname: Li
authors.affiliation: Merck & Co., Inc., Kenilworth, New Jersey, USA.
authors.forename: Tong-Ming
authors.identifier: http://orcid.org/0000-0003-1420-2271
authors.initials: TM
authors.lastname: Fu
authors.affiliation: Trellis Bioscience, LLC, Menlo Park, California, USA.
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Kauvar
authors.affiliation: Virginia Commonwealth University, Richmond, Virginia, USA michael.mcvoy@vcuhealth.org.
authors.forename: Michael A
authors.initials: MA
authors.lastname: McVoy
mesh_terms: D057134:Antibodies, Neutralizing / Q000276:immunology*; D000914:Antibodies, Viral / Q000276:immunology*; D002460:Cell Line; D003587:Cytomegalovirus / Q000276:immunology* / Q000502:physiology*; D004847:Epithelial Cells / Q000821:virology*; D005347:Fibroblasts / Q000821:virology*; D006801:Humans; D014759:Viral Envelope Proteins / Q000276:immunology; D053586:Virus Internalization
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D014759:Viral Envelope Proteins; C040495:glycoprotein B, Simplexvirus; C071440:glycoprotein H, Cytomegalovirus
keywords: antibodies; cytomegalovirus; fusion; neutralization; neutralizing antibodies; polymorphisms; spread; virus entry