title: Use of flow cytometry for characterization of human cytomegalovirus vaccine particles.
abstract: Despite a 40-year effort, an effective vaccine against human cytomegalovirus (HCMV) remains an unmet medical need. The discovery of potent neutralizing epitopes on the pentameric gH complex (gH/gL/UL128/130/131) has reenergized HCMV vaccine development. Our whole-virus vaccine candidate, currently in a Phase I clinical trial, is based on the attenuated AD169 strain with restored expression of the pentameric gH complex. Given the complexity of a whole-virus vaccine, improved analytical methods have been developed to better characterize heterogeneous viral particles released from infected cells during vaccine production. Here we show the utility of a commercial flow cytometer for the detection of individual HCMV particles, either via light scattering or using fluorescence after labeling of specific antigens. Rapid measurements requiring minimal material provide near real-time information on particle concentration, distributions of different particle types, and product purity. Additionally, utilizing immunoreagents has allowed us to characterize the distribution of key antigens across individual particles and particle types.
authors.affiliation: Vaccine Bioprocess Research and Development, Merck Research Labs, Merck & Co., Inc., Kenilworth, NJ 07033, United States.
authors.forename: Josef
authors.initials: J
authors.lastname: Vlasak
authors.affiliation: Vaccine Bioprocess Research and Development, Merck Research Labs, Merck & Co., Inc., Kenilworth, NJ 07033, United States.
authors.forename: Van M
authors.initials: VM
authors.lastname: Hoang
authors.affiliation: Vaccine Bioprocess Research and Development, Merck Research Labs, Merck & Co., Inc., Kenilworth, NJ 07033, United States.
authors.forename: Sianny
authors.initials: S
authors.lastname: Christanti
authors.affiliation: Vaccine Bioprocess Research and Development, Merck Research Labs, Merck & Co., Inc., Kenilworth, NJ 07033, United States.
authors.forename: Richard
authors.initials: R
authors.lastname: Peluso
authors.affiliation: Vaccine Discovery, Merck Research Labs, Merck & Co., Inc., Kenilworth, NJ 07033, United States.
authors.forename: Fengsheng
authors.initials: F
authors.lastname: Li
authors.affiliation: Vaccine Bioprocess Research and Development, Merck Research Labs, Merck & Co., Inc., Kenilworth, NJ 07033, United States. Electronic address: timothy_culp@merck.com.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Culp
mesh_terms: D002460:Cell Line; D003587:Cytomegalovirus; D022482:Cytomegalovirus Vaccines / Q000737:chemistry*; D005434:Flow Cytometry; D006801:Humans; D014759:Viral Envelope Proteins / Q000737:chemistry; D014771:Virion / Q000737:chemistry*
chemical_list: D022482:Cytomegalovirus Vaccines; D014759:Viral Envelope Proteins; C071440:glycoprotein H, Cytomegalovirus
keywords: Cytomegalovirus; Flow cytometry; Flow virometry; HCMV vaccine; Pentameric gH complex; gB glycoprotein