PREPs: herpes simplex virus type 1-specific particles produced by infected cells when viral DNA replication is blocked.
Herpes simplex virus (HSV)-infected cells produce not only infectious nucleocapsid-containing virions but also virion-related noninfectious light particles (L-particles) composed of the envelope and tegument components of the virus particle (J. F. Szilágyi and C. Cunningham, J. Gen. Virol. 62:661-668, 1991). We show that BHK and MeWO cells infected either with wild-type (WT) HSV type 1 (HSV-1) in the presence of viral DNA replication inhibitors (cytosine-beta-D-arabinofuranoside, phosphonoacetic acid, and acycloguanosine) or with a viral DNA replication-defective mutant of HSV-1 (ambUL8) synthesize a new type of virus-related particle that is morphologically similar to an L-particle but differs in its relative protein composition. These novel particles we term pre-viral DNA replication enveloped particles (PREPs). The numbers of PREPs released into the culture medium were of the same order as those of L-particles from control cultures. The particle/PFU ratios of different PREP stocks ranged from 6 x 10(5) to 3.8 x 10(8), compared with ratios of 3 x 10(3) to 1 x 10(4) for WT L-particle stocks. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western immunoblot analyses revealed that true late proteins, such as 273K (VP1-2), 82/81K (VP13/14), and gC (VP8), were greatly reduced or absent in PREPs and that gD (VP17) and 40K proteins were also underrepresented. In contrast, the amounts of proteins 175K (VP4; IE3), 92/91K (VP11/12), 38K (VP22), and gE (with BHK cells) were increased. The actual protein composition of PREPs showed some cell line-dependent differences, particularly in the amount of gE. PREPs were biologically competent and delivered functional Vmw65 (VP16; alpha TIF) to target cells, but the efficiency of complementation of the HSV-1 (strain 17) mutant in1814 was 10 to 30% of that of WT L-particles.
Dargan
D J
DJ
Medical Research Council Virology Unit, University of Glasgow, United Kingdom.
Patel
A H
AH
Subak-Sharpe
J H
JH
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D006224:Cricetinae; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis*; D018259:Herpesvirus 1, Human / Q000235:genetics / Q000502:physiology*; D006801:Humans; D007668:Kidney / Q000473:pathology / Q000821:virology; D008168:Lung / Q000473:pathology / Q000821:virology; D008854:Microscopy, Electron; D014771:Virion / Q000502:physiology* / Q000648:ultrastructure; D014779:Virus Replication
D004279:DNA, Viral