title: Identification of a Continuous Neutralizing Epitope within UL128 of Human Cytomegalovirus.
abstract: As human cytomegalovirus (HCMV) is the most common infectious cause of fetal anomalies during pregnancy, development of a vaccine that prevents HCMV infection is considered a global health priority. Although HCMV immune correlates of protection are only poorly defined, neutralizing antibodies (NAb) targeting the envelope pentamer complex (PC) composed of the subunits gH, gL, UL128, UL130, and UL131A are thought to contribute to the prevention of HCMV infection. Here, we describe a continuous target sequence within UL128 that is recognized by a previously isolated potent PC-specific NAb termed 13B5. By using peptide-based scanning procedures, we identified a 13-amino-acid-long target sequence at the UL128 C terminus that binds the 13B5 antibody with an affinity similar to that of the purified PC. In addition, the 13B5 binding site is universally conserved in HCMV, contains a previously described UL128/gL interaction site, and interferes with the 13B5 neutralizing function, indicating that the 13B5 epitope sequence is located within the PC at a site of critical importance for HCMV neutralization. Vaccination of mice with peptides containing the 13B5 target sequence resulted in the robust stimulation of binding antibodies and, in a subset of immunized animals, in the induction of detectable NAb, supporting that the identified 13B5 target sequence constitutes a PC-specific neutralizing epitope. These findings provide evidence for the discovery of a continuous neutralizing epitope within the UL128 subunit of the PC that could be an important target of humoral immune responses that are involved in protection against congenital HCMV infection.IMPORTANCENeutralizing antibodies (NAb) targeting the human cytomegalovirus (HCMV) envelope pentamer complex (PC) are thought to be important for preventing HCMV transmission from the mother to the fetus, thereby mitigating severe developmental disabilities in newborns. However, the epitope sequences within the PC that are recognized by these potentially protective antibody responses are only poorly defined. Here, we provide evidence for the existence of a highly conserved, continuous, PC-specific epitope sequence that appears to be located within the PC at a subunit interaction site of critical importance for HCMV neutralization. These discoveries provide insights into a continuous PC-specific neutralizing epitope, which could be an important target for a vaccine formulation to interfere with congenital HCMV infection.
authors.affiliation: Department of Experimental Therapeutics, Beckman Research Institute of the City of Hope, Duarte, California, USA.
authors.forename: Flavia
authors.initials: F
authors.lastname: Chiuppesi
authors.affiliation: Department of Experimental Therapeutics, Beckman Research Institute of the City of Hope, Duarte, California, USA.
authors.forename: Teodora
authors.initials: T
authors.lastname: Kaltcheva
authors.affiliation: Department of Experimental Therapeutics, Beckman Research Institute of the City of Hope, Duarte, California, USA.
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Meng
authors.affiliation: Center for Comparative Medicine, California National Primate Research Center, and Department of Pathology and Laboratory Medicine, University of California, Davis, Davis, California, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Barry
authors.affiliation: Department of Experimental Therapeutics, Beckman Research Institute of the City of Hope, Duarte, California, USA ddiamond@coh.org fwussow@coh.org.
authors.forename: Don J
authors.initials: DJ
authors.lastname: Diamond
authors.affiliation: Department of Experimental Therapeutics, Beckman Research Institute of the City of Hope, Duarte, California, USA ddiamond@coh.org fwussow@coh.org.
authors.forename: Felix
authors.initials: F
authors.lastname: Wussow
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood*; D000914:Antibodies, Viral / Q000097:blood*; D001665:Binding Sites; D017124:Conserved Sequence; D018604:Epitope Mapping; D018985:Epitopes, B-Lymphocyte / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000276:immunology*; D051379:Mice; D014759:Viral Envelope Proteins / Q000276:immunology*
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D018985:Epitopes, B-Lymphocyte; D008562:Membrane Glycoproteins; C532797:UL128 protein, human cytomegalovirus; D014759:Viral Envelope Proteins
keywords: HCMV; UL128; epitope; pentamer complex; peptide