title: Asynchronous progression through the lytic cascade and variations in intracellular viral loads revealed by high-throughput single-cell analysis of Kaposi's sarcoma-associated herpesvirus infection.
abstract: Kaposi's sarcoma-associated herpesvirus (KSHV or human herpesvirus-8) is frequently tumorigenic in immunocompromised patients. The average intracellular viral copy number within infected cells, however, varies markedly by tumor type. Since the KSHV-encoded latency-associated nuclear antigen (LANA) tethers viral episomes to host heterochromatin and displays a punctate pattern by fluorescence microscopy, we investigated whether accurate quantification of individual LANA dots is predictive of intracellular viral genome load. Using a novel technology that integrates single-cell imaging with flow cytometry, we found that both the number and the summed immunofluorescence of individual LANA dots are directly proportional to the amount of intracellular viral DNA. Moreover, combining viral (immediate early lytic replication and transcription activator [RTA] and late lytic K8.1) and cellular (syndecan-1) staining with image-based flow cytometry, we were also able to rapidly and simultaneously distinguish among cells supporting latent, immediate early lytic, early lytic, late lytic, and a potential fourth "delayed late" category of lytic replication. Applying image-based flow cytometry to KSHV culture models, we found that de novo infection results in highly varied levels of intracellular viral load and that lytic induction of latently infected cells likewise leads to a heterogeneous population at various stages of reactivation. These findings additionally underscore the potential advantages of studying KSHV biology with high-throughput analysis of individual cells.
authors.affiliation: Myles H. Thaler Center for AIDS and Human Retrovirus Research, Box 800734, Departments of Microbiology and Internal Medicine, University of Virginia Health Systems, Charlottesville, VA 22908, USA.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Adang
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Parsons
authors.forename: Dean H
authors.initials: DH
authors.lastname: Kedes
mesh_terms: D000956:Antigens, Viral / Q000032:analysis*; D002460:Cell Line; D004279:DNA, Viral / Q000032:analysis*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006023:Glycoproteins / Q000032:analysis; D019288:Herpesvirus 8, Human / Q000254:growth & development*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D017874:Immediate-Early Proteins / Q000032:analysis; D008562:Membrane Glycoproteins / Q000032:analysis; D009687:Nuclear Proteins / Q000032:analysis*; D016133:Polymerase Chain Reaction; D011509:Proteoglycans / Q000032:analysis; D053668:Syndecan-1; D053667:Syndecans; D015534:Trans-Activators / Q000032:analysis; D019562:Viral Load; D014764:Viral Proteins / Q000032:analysis
chemical_list: D000956:Antigens, Viral; D004279:DNA, Viral; D006023:Glycoproteins; D017874:Immediate-Early Proteins; C113454:K8.1 protein, Human herpesvirus 8; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D011509:Proteoglycans; C417604:Rta protein, Human herpesvirus 8; C508241:SDC1 protein, human; D053668:Syndecan-1; D053667:Syndecans; D015534:Trans-Activators; D014764:Viral Proteins; C109540:latency-associated nuclear antigen