Infectivity of Herpes simplex virus particles with and without envelopes

Abstract

Herpes simplex virions produced by infected human carcinoma No. 2 (HEp-2) cells appear in two general forms, unenveloped (naked) and enveloped. These two forms were separated by zone centrifugation at 18 000 g for 55 min through a 10 to 30% (w/v) sucrose density gradient. The three bands containing virus particles were found by electron microscopy to contain empty naked particles, full naked particles, and enveloped particles. The number of virus particles and the number of plaque-forming units (p.f.u.) were determined for each of the three types of particles. In the band containing enveloped virus particles the infectivity was 1 p.f.u./120 particles; the filled naked particle band yielded 1 p.f.u./60 000 particles; and the empty naked particle band yielded 1 p.f.u./960 000 particles. All of the infectivity of the starting material was recovered from the gradient after centrifugation. It appears that the plaque-forming efficiency of naked virus particles is extremely low, but is not negligible. Particle counts of enveloped full capsids indicate that empty and filled naked particles are enveloped indiscriminately.The infectivity of naked HSV particles as well as the number of naked particles that retain a core is increased when virus is harvested in pH 8.3 medium containing 0.01 M Na citrate, conditions that are unfavorable for DNase activity. The infectivity and morphology of enveloped particles are not affected by this harvesting method.

Membrane proteins specified by herpes simplex viruses. III. Role of glycoprotein VP7(B2) in virion infectivity

“…Adsorption on October 4, 2020 by guest http://jvi.asm.org/ Downloaded from of the labeled virions to the cells was carried out at room temperature on a shaker. At 15,30,60,and 120 min after addition of the virion suspensions to the cells, the inocula were removed from duplicate cultures, the monolayers were washed twice with PBS, and then the cells were disrupted and detached from the plastic surface by dispersion with PBS containing 0.1% Nonidet P-40. To quantitate the radioactive virions that had attached to the Vero cells, the suspended contents of each culture flask were mixed with trichloroacetic acid, and the precipitates were collected on glass fiber filters, washed with trichloroacetic acid and ethanol, and dissolved in Soluene (Packard Instrument Co., Inc., Downers Grove, Ill.) in preparation for liquid scintillation spectrometry.…”

“…The lipid-containing envelope of herpes simplex virus (HSV) mediates entry of the virus into a host cell, based on findings that naked nucleocapsids or particles with disrupted envelopes have very low specific infectivities relative to intact virions (22,30) and that envelope constituents are targets of neutralizing antibodies (2,8,16,18,27). Although the precise mechanism by which the HSV envelope facilitates viral entry into a host cell is not understood, it seems likely that the first event in the infectious process is specific adsorption of the virion to the host cell surface and that proteins on the virion surface mediate this initial interaction with the cell.…”