Antiviral activity of tunicamycin on herpes simplex virus

Abstract

Tunicamycin (0.5 ,ig/ml) significantly lowers (2 to 3 log,o) the infectious yield of herpes simplex virus type 1 grown in chicken embryo fibroblasts and in BSC1 cells. Although virus particles are formed and the synthesis of the viral deoxyribonucleic acid is only partially affected by the antibiotic, the glycosylation of herpesvirus glycopeptides is almost completely inhibited. The morphology of virus particles made in the presence of tunicamycin is similar to that of intact virus particles, as demonstrated by electron microscopy. This suggests that the absence of the carbohydrate side-chain from the viral glycopeptides does not affect the overall integrity of the virion but decreases very significantly the infectivity of these particles.Herpes simplex type 1 virus (HSV) is an enveloped deoxyribonucleic acid (DNA)-containing virus that assembles by budding from the cell nuclear membranes during its maturation process (13,14). The virion contains more than 30 structural polypeptides, to several of which carbohydrate side chains are covalently linked (7,21). The role of these glycopeptides in the overall integrity and stability of the virions is yet to be clarified.Tunicamycin is a glucosamine-containing antibiotic (23, 24) that specifically inhibits glycosylation of proteins (2,18,22). It blocks the transfer of N-acetylglucosamine-l-phosphate from uridine 5'-diphosphate-N-acetylglucosamine to the dolichyl monophosphate that serves as a lipid carrier (12,25) by inhibition of the transferase involved (6). Changes in the cell morphology and in the membrane properties of normal and virus-transformed fibroblasts occur in the presence of tunicamycin (3, 4). Tunicamycin significantly lowers the yield of several enveloped ribonucleic acid (RNA)-containing viruses (10,15,17,20). Whereas formation of virions of Semliki Forest, fowl plague (20), Sindbis, and vesicular stomatitis viruses (10) is greatly inhibited by tunicamycin, formation of Rous sarcoma and influenza virions occurs in the presence of the antibiotic; however, these virus particles show reduced infectivity and undetectable amounts of glycoproteins (15,20).In the present study, we examine the effect of tunicamycin on formation, structure, and infectivity of HSV particles to determine the involvement of the carbohydrate side chains of the glycopeptides in these viral processes and functions. MATERIALS

Adsorption and Penetration of Enveloped Herpes Simplex Virus Particles Modified by Tunicamycin or 2-Deoxy-D-glucose

“…This result was confirmed by electron microscopy. These results are in close agreement with the observations of Courtney et al (1973) and Katz et al (1980), showing no major influence of glycosylation inhibitors on the proportion of enveloped particles.…”

“…The non-glycosylated G protein of vesicular stomatitis virus is not transported to the plasma membrane and therefore no budding of virus is observed (Gibson et al, 1978). With herpes simplex virus (HSV) and Rous sarcoma virus (RSV), no significant reduction in formation of enveloped virus particles is observed but the yields of infectious virions are markedly reduced (Courtney et al, 1973;Katz et al, 1980;Pizer et al, 1980;Stohrer & Hunter, 1979). The low yields of infectious RSV have been ascribed to the inadequate production of an essential envelope glycoprotein (Stohrer & Hunter, 1979) whereas the mechanism behind the reduction in infectivity of unglycosylated HSV is unknown.…”

Analysis of Rab GTPase-Activating Proteins Indicates that Rab1a/b and Rab43 Are Important for Herpes Simplex Virus 1 Secondary Envelopment

“…This is because glycosylation is essential for infectivity, as shown by experiments in which infected cells were treated with tunicamycin, which blocks N-linked glycosylation (19)(20)(21). While a reduction in Rab1 activity would trap all of the envelope proteins in the ER, it is possible that assembly could occur at the ER membrane rather than at post-Golgi complex membranes, but in the absence of glycosylation of envelope proteins, viruses produced in this manner would be noninfectious.…”

A Novel Class of Growth Factors Related to Herpesviruses

“…PAA and tunicamycin completely inhibited PRGF production (Golais et al 1990). As PAA is known to inhibit the synthesis of herpesvirus structural proteins (Boetzi 1979), and tunicamycin inhibits N-glycosylation (Katz et al 1980;Norrild and Pedersen 1982), it was assumed that glycosylation might play at least an indirect role in PRGF synthesis. Both transforming and transformed phenotype repressing activity could be removed with antiserum against corresponding virus (Golais et al 1990).…”