Oncogenic transformation of hamster cells after exposure to herpes simplex virus type 2

Identification of epidermal growth factor receptor-tyrosine kinase inhibitor targeting the VP1 pocket of human rhinovirus

Screening a library of 1,200 preselected kinase inhibitors for anti-human rhinovirus 2 (HRV-2) activity in HeLa cells identified a class of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) as effective virus blockers. These were based on the 4-anilinoquinazoline-7-oxypiperidine scaffold, with the most potent representative AZ5385 inhibiting the virus with EC50 of 0.35 µM. Several structurally related analogs confirmed activity in the low µM range, while interestingly, other TKIs targeting EGFR lacked anti-HRV-2 activity. To further probe this lack of association between antiviral activity and EGFR inhibition, we stained infected cells with antibodies specific for activated EGFR (Y1068) and did not observe a dependency on EGFR-TK activity. Instead, consecutive passages of HRV-2 in HeLa cells in the presence of a compound and subsequent nucleotide sequence analysis of resistant viral variants identified the S181T and T210A alterations in the major capsid VP1 protein, with both residues located in the vicinity of a known hydrophobic pocket on the viral capsid. Further characterization of the antiviral effects of AZ5385 showed a modest virus-inactivating (virucidal) activity, while anti-HRV-2 activity was still evident when the inhibitor was added as late as 10 h post infection. The RNA copy/infectivity ratio of HRV-2 propagated in AZ5385 presence was substantially higher than that of control HRV indicating that the compound preferentially targeted HRV progeny virions during their maturation in infected cells. Besides HRV, the compound showed anti-respiratory syncytial virus activity, which warrants its further studies as a candidate compound against viral respiratory infections.

Modified ent-Abietane Diterpenoids from the Leaves of Suregada zanzibariensis

The leaf extract of Suregada zanzibariensis gave two new modified ent-abietane diterpenoids, zanzibariolides A (1) and B (2), and two known triterpenoids, simiarenol (3) and β-amyrin (4). The structures of the isolated compounds were elucidated based on NMR and MS data analysis. Single-crystal X-ray diffraction was used to establish the absolute configurations of compounds 1 and 2. The crude leaf extract inhibited the infectivity of herpes simplex virus 2 (HSV-2, IC50 11.5 μg/mL) and showed toxicity on African green monkey kidney (GMK AH1) cells at CC50 52 μg/mL. The isolated compounds 1-3 showed no anti-HSV-2 activity and exhibited insignificant toxicity against GMK AH1 cells at ≥100 μM.

Anti-respiratory syncytial virus and anti-herpes simplex virus activity of six Tanzanian medicinal plants with extended studies of Erythrina abyssinica stem bark

ETHNOPHARMACOLOGICAL RELEVANCE

Except for few highly pathogenic viruses, no antiviral drug has been approved for treatment of viral infections in humans. Plant extracts, selected based on their ethno-medical use, represent an important source of compounds for the development of novel candidate antiviral drugs. This especially concerns plants with ethnomedical records on their use in treatment of viral infections.

AIM OF THE STUDY

To identify and document medicinal plants used by traditional health practitioners (THPs) for treatment of respiratory infections and muco-cutaneous lesions in order to study their antiviral activity including identification of active components and elucidation of mode of antiviral activity.

MATERIALS AND METHODS

The ethno-medical survey was performed in the Kagera region of Tanzania. The THPs were asked for plants used for treatment of signs and symptoms of respiratory infections and watery muco-cutaneous blisters in oral and genital regions. The plants identified were successively extracted with n-hexane, ethyl acetate and water, and the extracts assayed for anti-respiratory syncytial virus (RSV), anti-herpes simplex virus 2 (HSV-2), and anti-human parainfluenza virus 2 (HPIV-2) activity in cultured cells. Antiviral components were separated by ethanol precipitation and CL-6B chromatography, and the mode of antiviral activity elucidated by the time-of-addition assay and selection for the virus variants resistant to antiviral plant extract.

RESULTS

THPs identified fifteen plants used for treatment of respiratory infections and muco-cutaneous blisters. The water extract, but not n-hexane or ethyl acetate extracts, of six of these plants including Erythrina abyssinica stem bark, inhibited infectivity of two glycosaminoglycan-binding viruses i.e., RSV and HSV-2 but not the sialic acid binding HPIV-2. An activity-guided separation revealed that antiviral component(s) of water extract of E. abyssinica could be precipitated with ethanol. This sample potently and selectively inhibited RSV and HSV-2 infectivity in cultured cells with IC50 values of 2.1 μg/ml (selectivity index >476) and 0.14 μg/ml (selectivity index >7143) respectively. The sample exhibited inhibitory effect on the virus attachment to and entry into the cells by directly targeting the viral particles. Indeed, 10 consecutive virus passages in HEp-2 cells in the presence of this extract selected for a resistant RSV variant lacking the attachment, viral membrane-associated, G protein due to a stop codon at amino acid residue 33 (Leu33stop). Fractionation of the E. abyssinica extract on a CL-6B column revealed that anti-RSV and HSV-2 activity correlated with carbohydrate content. The most pronounced antiviral activity was associated with a carbohydrate containing ingredient of molecular mass of <5 kDa, which may polymerize to antiviral composites of up to 410 kDa.

CONCLUSIONS

Altogether, the water extract of six medicinal plants showed anti-RSV and anti-HSV-2 activities. Extended studies of the stem bark of E. abyssinica identified antiviral components that potently and selectively inhibited infectivity of free RSV and HSV-2 particles, a feature of importance in topical treatment of these infections. This observation confirms ethno-medical information concerning the use of E. abyssinica extract for treatment of respiratory infections and herpetic lesions.

Herpes Simplex Virus Type 2 Mucin-Like Glycoprotein mgG Promotes Virus Release from the Surface of Infected Cells

The contribution of virus components to liberation of herpes simplex virus type 2 (HSV-2) progeny virions from the surface of infected cells is poorly understood. We report that the HSV-2 mutant deficient in the expression of a mucin-like membrane-associated glycoprotein G (mgG) exhibited defect in the release of progeny virions from infected cells manifested by ~2 orders of magnitude decreased amount of infectious virus in a culture medium as compared to native HSV-2. Electron microscopy revealed that the mgG deficient virions were produced in infected cells and present at the cell surface. These virions could be forcibly liberated to a nearly native HSV-2 level by the treatment of cells with glycosaminoglycan (GAG)-mimicking oligosaccharides. Comparative assessment of the interaction of mutant and native virions with surface-immobilized chondroitin sulfate GAG chains revealed that while the mutant virions associated with GAGs ~fourfold more extensively, the lateral mobility of bound virions was much poorer than that of native virions. These data indicate that the mgG of HSV-2 balances the virus interaction with GAG chains, a feature critical to prevent trapping of the progeny virions at the surface of infected cells.

FRET-Based Assay for the Quantification of Extracellular Vesicles and Other Vesicles of Complex Composition

Research in the field of extracellular vesicles is rapidly expanding and finding footholds in many areas of medical science. However, the availability of methodologies to quantify the concentration of membrane material present in a sample remains limited. Herein, we present a novel approach for the quantification of vesicle material, specifically the quantification of the total lipid membrane surface area, found in a sample using Förster resonance energy transfer (FRET). In this assay, sonication is used to drive the fusion between vesicles in the sample to be quantified and liposomes containing a pair of FRET fluorophores. The change in emission spectrum upon vesicle fusion is directly related to the total membrane surface area of the sample added, and a calibration curve allows for the quantification of a variety of vesicle species, including enveloped viruses, bacterial outer membrane vesicles, and mammalian extracellular vesicles. Without extensive optimization of experimental parameters, we were able to quantify down to ∼10⁹ vesicles/mL, using as little as 60 μL of the sample. The assay precision was comparable to that of a commercial nanoparticle tracking analysis system. While its limit of detection was slightly higher, the FRET assay is superior for the detection of small vesicles, as its performance is vesicle-size-independent. Taken together, the FRET assay is a simple, robust, and versatile method for the quantification of a variety of purified vesicle samples.

Comparative in Vitro Titrations of Herpes Simplex Virus in Cells Derived from Normal Uterine Cervix and from Cervical Cancer

Sero-epidemiologic investigations showed a significant association between carcinoma of the cervix uteri and previous infections of the female genital tract with subtype 2, or genital, Herpes Simplex Virus (HSV-2) (ref. 3, 13, 14, 16). This association could be due to a carcinogenic, or co-carcinogenic effect of HSV (ref. 6 and 17), or else to a preferential viral growth in tumoral or transformed cells as against normal cells. To test the latter hypothesis we cultured in vitro cells from normal cervix and from cervical cancer, and assayed HSV-2 (and also HSV-1, or facial, and the MP mutant of HSV-1: ref. 9, 12) in our cell cultures as well as in the human HEp-2 cell line. Equivalent viral yields (results not reported in detail), equivalent numbers of viral plaques (table 1) and similar plaque morphology (fig.8) and intracellular ecp (fig.7) were observed in our cell cultures and in HEp-2 cells. Thus, a preferential viral growth in tumoral cells is not apparent.

The herpevac trial for women: Sequence analysis of glycoproteins from viruses obtained from infected subjects

The Herpevac Trial for Women revealed that three dose HSV-2 gD vaccine was 58% protective against culture-positive HSV-1 genital disease, but it was not protective against HSV-2 infection or disease. To determine whether vaccine-induced immune responses had selected for a particular gD sequence in strains infecting vaccine recipients compared with viruses infecting control subjects, genetic sequencing studies were carried out on viruses isolated from subjects infected with HSV-1 or HSV-2. We identified naturally occurring variants among the gD sequences obtained from 83 infected subjects. Unique or low frequency amino acid substitutions in the ectodomain of gD were found in 6 of 39 HSV-1-infected subjects and in 7 of 44 HSV-2-infected subjects. However, no consistent amino acid change was identified in isolates from gD-2 vaccine recipients compared with infected placebo recipients. gC and gE surround and partially shield gD from neutralizing antibody, and gB also participates closely in the viral entry process. Therefore, these genes were sequenced from a number of isolates to assess whether sequence variation may alter protein conformation and influence the virus strain’s capacity to be neutralized by vaccine-induced antibody. gC and gE genes sequenced from HSV-1-infected subjects showed more variability than their HSV-2 counterparts. The gB sequences of HSV-1 oral isolates resembled each other more than they did gB sequences rom genital isolates. Overall, however, comparison of glycoprotein sequences of viral isolates obtained from infected subjects did not reveal any singular selective pressure on the viral cell attachment protein or surrounding glycoproteins due to administration of gD-2 vaccine.

The Cholestanol-Conjugated Sulfated Oligosaccharide PG545 Disrupts the Lipid Envelope of Herpes Simplex Virus Particles

Herpes simplex virus (HSV) and many other viruses, including HIV, initiate infection of host cells by binding to glycosaminoglycan (GAG) chains of cell surface proteoglycans. Although GAG mimetics, such as sulfated oligo- and polysaccharides, exhibit potent antiviral activities in cultured cells, the prophylactic application of these inhibitors as vaginal microbicides failed to protect women upon their exposure to HIV. A possible explanation for this failure is that sulfated oligo- and polysaccharides exhibit no typical virucidal activity, as their interaction with viral particles is largely electrostatic and reversible and thereby vulnerable to competition with GAG-binding proteins of the genital tract. Here we report that the cholestanol-conjugated sulfated oligosaccharide PG545, but not several other sulfated oligosaccharides lacking this modification, exhibited virucidal activity manifested as disruption of the lipid envelope of HSV-2 particles. The significance of the virus particle-disrupting activity of PG545 was also demonstrated in experimental animals, as this compound, in contrast to unmodified sulfated oligosaccharide, protected mice against genital infection with HSV-2. Thus, PG545 offers a novel prophylaxis option against infections caused by GAG-binding viruses.

Antiherpetic mechanism of a sulfated derivative of Agaricus brasiliensis fruiting bodies polysaccharide

OBJECTIVE

To study the anti-herpes simplex virus (HSV) activity of a (1→6)-(1→3)-β-D-glucan isolated from Agaricus brasiliensis fruiting bodies (FR) as well as its chemically sulfated derivative (FR-S).

METHODS

The antiherpetic activity and mechanism of action was studied by viral plaque assay applying different methodological strategies.

RESULTS

Although FR presented no in vitro antiherpetic action at 1 mg/ml, FR-S displayed promising anti-HSV-1 and anti-HSV-2 activities in both simultaneous and postinfection treatments, resulting in selectivity indices (CC₅₀/EC₅₀) higher than 393. FR-S had no virucidal effect, but significantly suppressed HSV-1 (EC₅₀ = 0.32 µg/ml) and HSV-2 (EC₅₀ = 0.10 µg/ml) adsorption. FR-S was less effective on adsorption inhibition of mutant virus strains devoid of gC (HSV-1 gC⁻39 and HSV-2 gCneg1), indicating a possible interaction with this glycoprotein. The reduction of viral adsorption upon cell pretreatment with FR-S also suggests its interaction with cellular components. FR-S inhibited HSV-1 (EC₅₀ = 8.39 µg/ml) and HSV-2 (EC₅₀ = 2.86 µg/ml) penetration more efficiently than heparin. FR-S reduced HSV-1 and HSV-2 cell-to-cell spread. A synergic effect between FR-S and acyclovir was also detected.

CONCLUSIONS

FR-S displays an interesting mechanism of antiviral action and represents a promising candidate for the treatment and/or prevention of herpetic infections, to be used as a single therapeutic agent or in combination with acyclovir.

Herpes simplex virus 2 ICP34.5 confers neurovirulence by regulating the type I interferon response

The γ34.5 gene of herpes simplex virus (HSV) 2 encodes ICP34.5, which enhances HSV-2 neurovirulence by an unknown mechanism. We found that an HSV-2 γ34.5-null mutant (γ34.5(-/-)) replicated less robustly than its rescue virus (γ34.5R) in wild-type mouse embryo fibroblasts (MEFs), and in cells primed with IFNβ. Increased eIF2α phosphorylation correlated with γ34.5(-/-) attenuation. However, γ34.5(-/-) achieved titers equivalent to γ34.5R in MEFs lacking the type I IFN receptor (IFNα/βR(-/-)) or lacking protein kinase R. γ34.5(-/-) also replicated poorly in the vaginal mucosa of wild-type mice, caused little genital inflammation, and spread to the nervous system at lower levels compared to γ34.5R. In IFNα/βR(-/-) mice, however, γ34.5(-/-) regained the capacity to replicate and cause disease equivalent to γ34.5R after intravaginal infection or direct inoculation into the central nervous system. Thus, the capacity of HSV-2 ICP34.5 to interdict the type I IFN response in vivo largely determines its neurovirulence.

Tannic acid modified silver nanoparticles show antiviral activity in herpes simplex virus type 2 infection

The interaction between silver nanoparticles and herpesviruses is attracting great interest due to their antiviral activity and possibility to use as microbicides for oral and anogenital herpes. In this work, we demonstrate that tannic acid modified silver nanoparticles sized 13 nm, 33 nm and 46 nm are capable of reducing HSV-2 infectivity both in vitro and in vivo. The antiviral activity of tannic acid modified silver nanoparticles was size-related, required direct interaction and blocked virus attachment, penetration and further spread. All tested tannic acid modified silver nanoparticles reduced both infection and inflammatory reaction in the mouse model of HSV-2 infection when used at infection or for a post-infection treatment. Smaller-sized nanoparticles induced production of cytokines and chemokines important for anti-viral response. The corresponding control buffers with tannic acid showed inferior antiviral effects in vitro and were ineffective in blocking in vivo infection. Our results show that tannic acid modified silver nanoparticles are good candidates for microbicides used in treatment of herpesvirus infections.

Up to four distinct polypeptides are produced from the γ34.5 open reading frame of herpes simplex virus 2

The herpes simplex virus 1 (HSV-1) ICP34.5 protein strongly influences neurovirulence and regulates several cellular antiviral responses. Despite the clinical importance of HSV-2, relatively little is known about its ICP34.5 ortholog. We found that HSV-2 produces up to four distinct forms of ICP34.5 in infected cells: a full-length protein, one shorter form sharing the N terminus, and two shorter forms sharing the C terminus. These forms appeared with similar kinetics and accumulated in cells over much of the replication cycle. We confirmed that the N-terminal form is translated from the primary unspliced transcript to a stop codon within the intron unique to HSV-2 γ34.5. We found that the N-terminal form was produced in a variety of cell types and by 9 of 10 clinical isolates. ICP27 influenced but was not required for expression of the N-terminal form. Western blotting and reverse transcription-PCR indicated the C-terminal forms did not contain the N terminus and were not products of alternative splicing or internal transcript initiation. Expression plasmids encoding methionine at amino acids 56 and 70 generated products that comigrated in SDS-PAGE with the C1 and C2 forms, respectively, and mutation of these sites abolished C1 and C2. Using a recombinant HSV-2 encoding hemagglutinin (HA)-tagged ICP34.5, we demonstrated that the C-terminal forms were also produced during infection of many human and mouse cell types but were not detectable in mouse primary neurons. The protein diversity generated from the HSV-2 γ34.5 open reading frame implies additional layers of cellular regulation through potential independent activities associated with the various forms of ICP34.5.

IMPORTANCE

The herpes simplex virus 1 (HSV-1) protein ICP34.5, encoded by the γ34.5 gene, interferes with several host defense mechanisms by binding cellular proteins that would otherwise stimulate the cell's autophagic, translational-arrest, and type I interferon responses to virus infection. ICP34.5 also plays a crucial role in determining the severity of nervous system infections with HSV-1 and HSV-2. The HSV-2 γ34.5 gene contains an intron not present in HSV-1 γ34.5. A shorter N-terminal form of HSV-2 ICP34.5 can be translated from the unspliced γ34.5 mRNA. Here, we show that two additional forms consisting of the C-terminal portion of ICP34.5 are generated in infected cells. Production of these N- and C-terminal forms is highly conserved among HSV-2 strains, including many clinical isolates, and they are broadly expressed in several cell types, but not mouse primary neurons. Multiple ICP34.5 polypeptides add additional complexity to potential functional interactions influencing HSV-2 neurovirulence.

Stimulation of cellular DNA synthesis by human cytomegalovirus

Human cytomegalovirus (CMV) is able to induce cellular DNA synthesis in both permissive (human embryonic lung) and nonpermissive (Vero) cells. The induction of cell DNA synthesis was assayed by the incorporation of [methyl-(3)H]thymidine into macromolecules having the buoyant density characteristics of cell DNA. The DNA synthesis induced by CMV infection appears to represent normal semiconservative replication as opposed to repair synthesis. Both strains of CMV tested were capable of inducing cell DNA synthesis. Virus exposed to heat or UV light prior to infection lost the ability to induce DNA synthesis, indicating that a virus-coded function expressed after infection is responsible for stimulation of cell DNA synthesis.

Human antibodies to herpes simplex virus type 1 glycoprotein C are neutralizing and target the heparan sulfate-binding domain

Human antibodies specific for glycoprotein C (gC1) of herpes simplex virus type 1 (HSV-1) neutralized the virus infectivity and efficiently inhibited attachment of HSV-1 to human HaCaT keratinocytes and to murine mutant L cells expressing either heparan sulfate or chondroitin sulfate at the cell surface. Similar activities were observed with anti-gC1 monoclonal antibody B1C1. In addition to HaCaT and L cells, B1C1 antibody neutralized HSV-1 infectivity in simian GMK AH1 cells mildly pre-treated with heparinase III. Human anti-gC1 antibodies efficiently competed with the binding of gC1 to B1C1 antibody whose epitope overlaps a part of the attachment domain of gC1. Human anti-gC1 and B1C1 antibodies extended survival time of mice experimentally infected with HSV-1. We conclude that in HaCaT cells and in cell systems showing restricted expression of glycosaminoglycans, human and some monoclonal anti-gC1 antibodies can target the cell-binding domain of this protein and neutralize viral infectivity.

A highly lipophilic sulfated tetrasaccharide glycoside related to muparfostat (PI-88) exhibits virucidal activity against herpes simplex virus

Although sulfated polysaccharides potently inhibit the infectivity of herpes simplex virus (HSV) and human immunodeficiency virus in cultured cells, these compounds fail to show protective effects in humans, most likely due to their poor virucidal activity. Herein we report on sulfated oligosaccharide glycosides related to muparfostat (formerly known as PI-88) and their assessment for anti-HSV activity. Chemical modifications based on the introduction of specific hydrophobic groups at the reducing end of a sulfated oligosaccharide chain enhanced the compound's capability to inhibit the infection of cells by HSV-1 and HSV-2 and abrogated the cell-to-cell transmission of HSV-2. Furthermore, modification with a highly lipophilic cholestanyl group provided a compound with virucidal activity against HSV. This glycoside targeted the viral particle and, to a lesser degree, the cell, and exhibited an antiviral mode of action typical for sulfated polysaccharides and virucides, i.e., interference with the virus attachment to cells and irreversible inactivation of virus infectivity, respectively. The virucidal activity was decreased in the presence of human cervical secretions suggesting that higher doses of this glycoside might be needed for in vivo application. Altogether, the sulfated oligosaccharide-cholestanyl glycoside exhibits potent anti-HSV activity and is, therefore, a good candidate for development as a virucide.

Increased eIF2alpha phosphorylation attenuates replication of herpes simplex virus 2 vhs mutants in mouse embryonic fibroblasts and correlates with reduced accumulation of the PKR antagonist ICP34.5

Herpes simplex virus 2 (HSV-2) strains containing mutations in the virion host shutoff (vhs) protein are attenuated for replication compared with wild-type virus in mouse embryonic fibroblasts (MEFs). However, HSV-2 vhs mutants replicate to near wild-type levels in the absence of the RNA-activated protein kinase (PKR). PKR is one of several kinases that phosphorylates the eukaryotic initiation factor 2alpha (eIF2alpha) to inhibit translation initiation, and we previously found that more of the phosphorylated form of eIF2alpha accumulates in MEFs infected with HSV-2 vhs mutants than with wild-type virus. Here, we show that this increase in phosphorylated eIF2alpha is primarily PKR dependent. Using MEFs expressing nonphosphorylatable eIF2alpha, we demonstrate that phosphorylated eIF2alpha is the primary cause of attenuated replication of HSV-2 vhs mutants and that attenuation correlates with decreased accumulation of viral proteins. Normally, HSV antagonizes eIF2alpha phosphorylation through the action of ICP34.5, which redirects protein phosphatase 1alpha (PP1alpha) to dephosphorylate eIF2alpha during infection. We show that ICP34.5 does not accumulate efficiently in MEFs infected with HSV-2 vhs mutant viruses, suggesting that the accumulation of phosphorylated eIF2alpha and the attenuated phenotype of HSV-2 vhs mutants in MEFs result from a deficiency in ICP34.5.

Reconsideration of viral protein immunoblotting for differentiation of human herpes simplex viruses

Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) are ubiquitous human pathogens that infect their hosts for life and reactivate to cause disease at or near the initial site of infection. As the incidence of genital HSV-1 infections increase, there is an increased demand for valid viral typing diagnostics. In this report, we reconsidered and developed a triple-phase immune-typing procedure that compares differences in electrophoretic mobilities of viral ICP4, ICP27, and VP22 proteins between HSV-1 and HSV-2 strains. We isolated and immunotyped 5 primary HSV-1 strains derived from orofacial, ocular, and genital areas along with 2 primary HSV-2 strains from the genital area. Advantages of this methodology include its general technical simplicity, sensitivity, and ability to definitively type HSV. It is anticipated that this methodology will be useful in distinguishing viruses obtained in clinical cultures.

Evaluation of anti-HSV-2 activity of gallic acid and pentyl gallate

The synthetic n-alkyl esters of gallic acid, also known as gallates, are widely employed as antioxidants by food and pharmaceutical industries. Besides the antioxidant activity, other biological activities have been described for this group of molecules, mainly anticancer, antibacterial and antifungal properties. In the present study, the anti-herpes simplex virus (HSV)-2 activity of gallic acid and pentyl gallate was evaluated followed by the determination of the site of antiviral activity of these compounds. Our results demonstrated that both compounds reduced HSV-2 replication in a concentration-dependent manner when either incubated with the virus prior to the addition of the mixture to cells, or added to and incubated with cells after their infection. In summary, the anti-HSV-2 activity of gallic acid and pentyl gallate was ascribed to their virucidal effect on virus particles, a change that was likely accompanied by partial inhibition of the virus attachment to cells and its subsequent cell-to-cell spread activity. This suggests that these compounds can be regarded as promising candidates for development as topical anti-HSV-2 agents.

Herpes simplex virus type 2 glycoprotein G is targeted by the sulfated oligo- and polysaccharide inhibitors of virus attachment to cells

Variants of herpes simplex virus type 2 (HSV-2) generated by virus passage in GMK-AH1 cells in the presence of the sulfated oligosaccharide PI-88 were analyzed. Many of these variants were substantially resistant to PI-88 in their initial infection of cells and/or their cell-to-cell spread. The major alteration detected in all variants resistant to PI-88 in the initial infection of cells was a frameshift mutation(s) in the glycoprotein G (gG) gene that resulted in the lack of protein expression. Molecular transfer of the altered gG gene into the wild-type background confirmed that the gG-deficient recombinants were resistant to PI-88. In addition to PI-88, all gG-deficient variants of HSV-2 were resistant to the sulfated polysaccharide heparin. The gG-deficient virions were capable of attaching to cells, and this activity was relatively resistant to PI-88. In addition to having a drug-resistant phenotype, the gG-deficient variants were inefficiently released from infected cells. Purified gG bound to heparin and showed the cell-binding activity which was inhibited by PI-88. Many PI-88 variants produced syncytia in cultured cells and contained alterations in gB, including the syncytium-inducing L792P amino acid substitution. Although this phenotype can enhance the lateral spread of HSV in cells, it conferred no virus resistance to PI-88. Some PI-88 variants also contained occasional alterations in gC, gD, gE, gK, and UL24. In conclusion, we found that glycoprotein gG, a mucin-like component of the HSV-2 envelope, was targeted by sulfated oligo- and polysaccharides. This is a novel finding that suggests the involvement of HSV-2 gG in interactions with sulfated polysaccharides, including cell surface glycosaminoglycans.

Molecular basis for resistance of herpes simplex virus type 1 mutants to the sulfated oligosaccharide inhibitor PI-88

Herpes simplex virus type 1 variants selected by virus propagation in cultured cells in the presence of the sulfated oligosaccharide PI-88 were analyzed. Many of these variants were substantially resistant to the presence of PI-88 during their initial infection of cells and/or their cell-to-cell spread. Nucleotide sequence analysis revealed that the deletion of amino acids 33-116 of gC but not lack of gC expression provided the virus with selective advantage to infect cells in the presence of PI-88. Purified gC (Delta33-116) was more resistant to PI-88 than unaltered protein in its binding to cells. Alterations that partly contributed to the virus resistance to PI-88 in its cell-to-cell spread activity were amino acid substitutions Q27R in gD and R770W in gB. These results suggest that PI-88 targets several distinct viral glycoproteins during the course of initial virus infection and cell-to-cell spread.

Anti-herpes simplex virus activities of two novel disulphated cyclitols

By screening a library of sulphated compounds of low molecular weight, we have found that several cyclitol derivatives, each modified with two sulphate groups in addition to pyrrole and various aromatic moieties, inhibited infectivity of herpes simplex virus (HSV) at concentrations approximately 100 times lower than those toxic for cultured cells. These disulphated cyclitols interfered with HSV-1 attachment to cells, and efficiently reduced the cell-to-cell spread of the virus. This effect is most likely due to their low molecular weight and associated with the compounds' capability to access the narrow intercellular spaces. Furthermore, these disulphated cyclitols also inactivated infectivity of HSV. However, the virus-inactivating activities of these compounds were to some extent diminished in the presence of human cervical secretions or other protein-rich solutions suggesting that disulphated cyclitols may have some features of surfactant-type virucides. In conclusion, this new class of anti-HSV compounds offers potential for further development.

Chondroitin Sulfate Characterized by the E-disaccharide Unit Is a Potent Inhibitor of Herpes Simplex Virus Infectivity and Provides the Virus Binding Sites on gro2C Cells

Although cell surface chondroitin sulfate (CS) is regarded as an auxiliary receptor for binding of herpes simplex virus to cells, and purified CS chain types A, B, and C are known to interfere poorly or not at all with the virus infection of cells, we have found that CS type E (CS-E), derived from squid cartilage, exhibited potent antiviral activity. The IC(50) values ranged from 0.06 to 0.2 mug/ml and substantially exceeded the antiviral potency of heparin, the known inhibitor of virus binding to cells. Furthermore, in mutant gro2C cells that express CS but not heparan sulfate, CS-E showed unusually high anti-herpes virus activity with IC(50) values of <1 ng/ml. Enzymatic degradation of CS-E with chondroitinase ABC abolished its antiviral activity. CS-E inhibited the binding to cells of the purified virus attachment protein gC. A direct interaction of gC with immobilized CS-E and inhibition of this binding by CS-E oligosaccharide fragments greater than octasaccharide were demonstrated. Likewise, the gro2C-specific CS chains interfered with the binding of viral gC to these cells and were found to contain a considerable proportion (13%) of the E-disaccharide unit, suggesting that this unit is an essential component of the CS receptor for herpes simplex virus on gro2C cells and that the antiviral activity of CS-E was due to interference with the binding of viral gC to a CS-E-like receptor on the cell surface. Knowledge of the determinants of antiviral properties of CS-E will help in the development of inhibitors of herpes simplex virus infections in humans.

Conservation of type-specific B-cell epitopes of glycoprotein G in clinical herpes simplex virus type 2 isolates

Glycoprotein G (gG-2) of herpes simplex virus type 2 (HSV-2) is cleaved to a secreted amino-terminal portion and to a cell-associated, heavily O-glycosylated carboxy-terminal portion that constitutes the mature gG-2 (mgG-2). The mgG-2 protein is commonly used as a type-specific antigen in the serodiagnosis of HSV-2 infection. As the amino acid sequence variability of mgG-2 in clinical isolates may affect the performance of such assays, the gG-2 gene was sequenced from 15 clinical HSV-2 isolates. Few mutations were identified, and these were mostly localized outside the epitope regions described earlier. Five isolates were identical to different laboratory strains, indicating that the gG-2 gene is highly conserved over time. In the search for HSV-2 isolates harboring mutations within the immunodominant region of mgG-2, a pool of 2,400 clinical HSV-2 isolates was tested for reactivity with two anti-mgG-2 monoclonal antibodies (MAbs). Ten MAb escape HSV-2 mutants, which all harbored structurally restricted single- or dual-point mutations within the respective epitopes explaining the loss of binding, were identified. Sera from corresponding patients were reactive to mgG-2, as well as to a peptide representing the immunodominant region, suggesting that the point mutations detected did not diminish seroreactivity to mgG-2. The conservation of the gG-2 gene reported here further supports the use of mgG-2 as a type-specific antigen in the diagnosis of HSV-2 infections.

Herpes simplex virus types 1 and 2 differ in their interaction with heparan sulfate

Cell surface heparan sulfate (HS) serves as an initial receptor for many different viruses, including herpes simplex virus types 1 and 2 (HSV-1 and 2, respectively). Glycoproteins C and B (gC and gB) are the major components of the viral envelope that mediate binding to HS. In this study, purified gB and gC homologous proteins as well as purified HSV-1 and HSV-2 virions were compared for the ability to bind isolated HS receptor molecules. HSV-1 gC and HSV-2 gC bound comparable amounts of HS. Similarly, HSV-1 gB and its HSV-2 counterpart showed no difference in the HS-binding capabilities. Despite the similar HS-binding potentials of gB and gC homologs, HSV-1 virions bound more HS than HSV-2 particles. Purified gC and gB proteins differed with respect to sensitivity of their interaction with HS to increased concentrations of sodium chloride in the order gB-2 > gB-1 > gC-1 > gC-2. The corresponding pattern for binding of whole HSV virions to cells in the presence of increased ionic strength of the medium was HSV-2 gC-neg1 > HSV-1 gC(-)39 > HSV-1 KOS 321 > HSV-2 333. These results relate the HS-binding activities of individual glycoproteins with the cell-binding abilities of whole virus particles. In addition, these data suggest a greater contribution of electrostatic forces for binding of gB proteins and gC-negative mutants compared with binding of gC homologs and wild-type HSV strains. Binding of wild-type HSV-2 virions was the least sensitive to increased ionic strength of the medium, suggesting that the less extensive binding of HS molecules by HSV-2 than by HSV-1 can be compensated for by a relatively weak contribution of electrostatic forces to the binding. Furthermore, gB and gC homologs exhibited different patterns of sensitivity of binding to cells to inhibition with selectively N-, 2-O-, and 6-O-desulfated heparin compounds. The O-sulfate groups of heparin were found to be more important for interaction with gB-1 than gB-2. These results indicate that HSV-1 and HSV-2 differ in their interaction with HS.

Functions and proteins of herpes simplex virus type-1 that are involved in raising the mutation frequency of infected cells

When cells are infected by herpes simplex virus type-1 (HSV-1) the mutation frequency is increased. To find which functions of the virus are responsible for this, a variety of viral strains and one fragment of viral DNA were tested in a mutagenesis assay. Mutagenesis was dependent on the binding of the virus to the cell surface and disassembly of the virus particle, but expression of virus genes was not necessary. Since this implied that mutagenesis was a result of the exposure of the interior of the cell to an internal structural component of the virus, the role of two likely components was examined. The host-shutoff function of the virus was not required for mutagenesis. However, a fragment of DNA from within the minimum transforming region of HSV-1 that encodes a possible virion protein was mutagenic when expressed from a eukaryotic expression vector. The encoded product of this DNA fragment is therefore a candidate for a transforming protein of HSV-1, and is the only protein currently suggested to be responsible for that function.

Transformation of rodent fibroblasts by herpes simplex virus: presence of morphological transforming region 1 (MTR 1) is not required for the maintenance of the transformed state

Studies on the mechanisms of transformation of mammalian cells by herpes simplex virus (HSV) in vitro have been prevented so far by the extremely low transformation frequencies obtained in monolayer culture. Here we present a transformation system that relies on the direct seeding in soft agar of infected single cells, thus avoiding negative interactions between normal and transformed cells. We took advantage of HSV-I temperature-sensitive mutants at the UL9 locus, which codes for a DNA-binding protein necessary for viral DNA replication. At the non-permissive temperature, viral DNA synthesis and late gene expression are prevented. Viral gene expression is restricted to immediate early and early genes. Induction of transformation was highly efficient in our one-step transformation system. It depended on intact viral particles and viral DNA. Immediate early and/or early viral gene expression was sufficient to induce transformation. Colonies were stably transformed and did not show any rescue of viable virus after temperature downshift and co-cultivation with susceptible cells. Transformed cells maintained the transformed state in the absence of viral DNA. Our data therefore support the "hit-and-run" hypothesis for the transforming effect of HSV.

Viruses and oral cancer

Oral cancer is a disease with a complex etiology. There is evidence for important roles of smoking, drinking, and genetic susceptibility, as well as strong indications that DNA viruses could be involved. The herpes simplex virus type 1 has been associated with oral cancer by serological studies, and animal models and in vitro systems have demonstrated that it is capable of inducing oral cancer. Papillomaviruses are found in many oral cancers and are also capable of transforming cells to a malignant phenotype. However, both virus groups depend on co-factors for their carcinogenic effects. Future research on viruses and oral cancer is expected to clarify the role of these viruses, and this will lead to improvements in diagnosis and treatment of the disease.

DNA sequence of mutations induced in cells by herpes simplex virus type-1

The shuttle vector plasmid pZ189 was used to find the kinds of mutations that are induced in cells by herpes simplex virus type-1 (HSV-1). A significant increase in mutation frequency was detected as early as 2 hr after infection, and reached a peak of two- to sevenfold over background at 4 hr after infection. Several differences were detected between spontaneous mutants and those induced by HSV-1 when they were analyzed by gel electrophoresis and DNA sequencing. Point mutations accounted for 63% of spontaneous mutants but for only 44% of HSV-1-induced mutants (P less than 0.05). In each case the predominant type of point mutation was the G:C to A:T transition, which comprised 51% of point mutations induced by HSV-1, and 32% of spontaneous point mutations. Deletions of DNA were seen in HSV-1-induced mutants at a frequency of 44%, compared with only 29% in spontaneous mutants. HSV-1-induced deletions were less than half the length of spontaneous deletions, and 3 contained short filler sequences. An increase in size was seen in 13% of HSV-1-induced mutants and was due either to duplication of plasmid DNA, or, in 8 instances, to insertion of sequences derived from cellular DNA. Among spontaneous mutants, only 8% were increased in size and none of them had inserted cellular DNA. The proportion of complex mutants increased as infection by the virus progressed and they accounted for 79% of mutants at 24 hr after infection. The observed mutations have implications for understanding the "hit and run" mechanism of malignant transformation of cells by HSV-1.

Failure to detect viral genomic sequences of three viruses (herpes simplex, simian virus 40 and adenovirus) in human and rat brain tumors

Little is known about oncogenesis in brain tumors. Viruses are thought to be involved in some neurological diseases, the presence of subfractions of viral DNA has been reported in various circumstances and the oncogenicity of some viruses has been demonstrated in animal experiments. The discovery of homologies between retroviral oncogenes and normal cellular genes (proto-oncogenes) has stimulated once again the search for viral responsibility in oncogenesis. Having a large bank of tumor material available, we systematically examined 39 brain tumors using Southern blot hybridization with DNAs of three viruses, known to be involved in neurological diseases: herpes simplex virus (HSV), simian virus 40 (SV40) and adenovirus type 2 (Ad2). We detected no homology between the DNAs of the examined material and the viral DNA probes. We compare these negative results with those of other published studies and discuss the experimental conditions, with special reference to the possibility of non-specific hybridization, which could account for the positive results reported. The present negative results could be interpreted either as absence of involvement of the three investigated viruses in brain tumor oncogenesis, or an indirect involvement through a hit-and-run mechanism or a highly dispersed state of the viral sequences among the host genome, which would prevent hybridization with the probe, as it has been supposed to be the case during the latency phase of herpes virus.

Alterations in the cellular phenotype induced by herpes simplex viruses

Numerous studies have shown that herpes simplex virus types 1 and 2 (HSV-1, HSV-2) are able to transform the morphological phenotype of rodent cells. Unlike other DNA tumor viruses the transformed cells did not consistently retain or express a given set of viral genes. In fact, transformation could be obtained using fragments of viral DNA that did not wholly encode viral proteins. Of interest within the transforming fragments were sequences which could assume a secondary structure like that of insertion elements. The failure to detect viral DNA in transformed cells led to the hit-and-run hypothesis of HSV transformation. The mechanism by which HSV induces transformation is not understood. Various lines of investigation have shown that HSV is able to cause mutations--both point mutations and gene rearrangements. HSV is also able to induce gene amplification, particularly of sequences harboring an origin of replication such as SV40 or papillomaviruses. Other experiments have shown that HSV can activate the expression of endogenous type C retroviruses. More broadly, HSV has been shown to activate cellular transcription or to switch on the synthesis of host cell proteins not normally expressed in untransformed cells. The failure to detect viral DNA in a high proportion of human anogenital tumors made it difficult to implicate HSV in the etiology of those neoplasias, but it is consistent, however, with the observations on the mode of HSV transformation in vitro, and suggests that HSV could be involved in a multistage process of oncogenic transformation.

Phenotypic properties of herpesvirus-transformed cells with high tumorigenic and metastatic ability

Herpes simplex virus type 2-transformed hamster embryo fibroblasts (333-8-9 cells) produce increased plasminogen activator (PA) compared with normal hamster cells. These cells produce undifferentiated fibrosarcomas at the inoculation site in newborn hamsters, and metastasize to the lungs. Using a direct PA assay, in which 125I-labeled plasminogen is cleaved, the optimum pH and osmolarity for detection of the 333-8-9 extracellular PA were pH 8.9 and approximately 150 mOsmol. Secretion of enzyme did not vary significantly on a per cell basis over cell densities from 0.1 to 8.0 X 10(7) cells/T-75 cm2 flask. This assay demonstrates that the 333-8-9 cells produce at least 20-fold greater levels of PA than normal cell counterparts. Based on the molecular weight (50-58 kDa) of secreted 333-8-9 cells PA and lack of fibrin stimulation, we conclude that it is a urokinase type PA. Subclonal lines of the 333-8-9 cells, selected for an increased PA phenotype were stable in culture, more tumorigenic and probably more metastatic. Correlation of these two events was examined by passaging 333-8-9 cells in vivo to select for greater tumorigenic potential and then determining the production of PA by the in vivo-derived sublines. The metastatic potential of the resulting cells was heterogeneous. Increased PA production upon increased passage in vivo did not always occur, whether the cells were passaged as subcutaneous tumors or as ascites tumors. Thus, while enzyme production correlated with tumorigenicity when selecting cells for an increased protease phenotype, this correlation was not observed when selecting for in vivo tumorigenicity. The results suggest that increased ability to make PA represents only one of multiple selective advantages for tumor growth.

Immunogenicity of herpes simplex virus glycoprotein gB-1-related protein produced in yeast

A protein related to glycoprotein B of herpes simplex virus type 1 (HSV-1) produced in yeast (ygB-1) was purified with an immunoadsorbent. The molecular weight of the purified ygB-1 as determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis was 96,000. Mice injected twice with ygB-1 adsorbed to alum developed ELISA antibody to ygB-1, neutralizing antibody to HSV-1 and a lymphoproliferative response to ygB-1 and HSV-1. The immunized mice were protected against intraperitoneal and corneal challenge with HSV-1. Latent infection in the trigeminal ganglia after corneal challenge was also inhibited by immunization with ygB-1. Guinea-pigs pigs immunized with ygB-1 adsorbed to alum also developed ELISA antibody to to ygB-1 and neutralizing antibody to both types of HSV. After the second dose, strong lymphoproliferative responses were seen upon stimulation with HSV-2. Animals were protected against intravaginal challenge with HSV type 2.

Cellular polypeptides overexpressed after herpes simplex infection permit virus subtyping and may help diagnose cervical cancer

The synthesis of cellular macromolecules is inhibited after infection with herpes simplex viruses (HSV) although certain host proteins accumulate to high concentrations as identified by monoclonal antibody TG7A. By western blotting, a polypeptide with a relative molecular weight of 90 kilodaltons was identified in cells infected with type 2 viruses and a polypeptide of 40 kilodaltons relative molecular weight in type 1 infected cells, and virus typing was confirmed by restriction enzyme analysis of viral DNA. Thirty seven clinical isolates from the genital region were subtyped as HSV type 2 and 18 from the orofacial region as type 1 by the different intracellular location of the 90 kilodalton and 40 kilodalton proteins seen on immunofluorescent staining of cells infected with HSV. Expression of these proteins has been associated with cellular transformation due to gene products of HSV or other viruses. Overexpression of the cellular proteins identified by TG7A reactivity was shown to be a marker for cells in cervical smears from patients with CIN III that appeared to be dyskaryotic. Little or no reaction was observed in squamous epithelial cells found in normal or abnormal smears.

Hypomethylation of host cell DNA synthesized after infection or transformation of cells by herpes simplex virus

Infection of rat embryo cells with herpes simplex virus type 2 caused undermethylation of host cell DNA synthesized during infection. DNA made prior to infection was not demethylated, but some of its degradation products, including methyl dCMP, were incorporated into viral DNA. The use of mutant virus showed that some viral DNA synthesis appears to be required for the inhibition of methylation. Inhibition of methylation cannot be explained by an absence of DNA methyltransferase as the activity of this enzyme did not change during the early period of infection. Inhibition of host cell DNA methylation may be an important step in the transformation of cells by herpesviruses, and various transformed cell lines tested showed reduced levels of DNA methylation.

Hypomethylation of host cell DNA synthesized after infection or transformation of cells by herpes simplex virus

Infection of rat embryo cells with herpes simplex virus type 2 caused undermethylation of host cell DNA synthesized during infection. DNA made prior to infection was not demethylated, but some of its degradation products, including methyl dCMP, were incorporated into viral DNA. The use of mutant virus showed that some viral DNA synthesis appears to be required for the inhibition of methylation. Inhibition of methylation cannot be explained by an absence of DNA methyltransferase as the activity of this enzyme did not change during the early period of infection. Inhibition of host cell DNA methylation may be an important step in the transformation of cells by herpesviruses, and various transformed cell lines tested showed reduced levels of DNA methylation.

Tumorigenicity of herpesvirus-transformed cells correlates with production of plasminogen activator

Our studies first demonstrated that established hamster cell lines transformed in vitro by herpesviruses activate plasminogen more effectively than normal hamster fibroblasts. This ability is probably due to increased levels of the enzyme plasminogen activator (PA). In the studies described here, the 333-8-9 cell line, originally transformed by herpes simplex virus type 2 strain 333, was used to derive subclonal lines that maintained stable PA phenotypes over the course of long in vitro passage. We were interested in correlating tumor formation by the subclones with their fibrinolytic capacity. Cells were, therefore, single-cell subcloned twice, and resulting cultures were tested for ability to activate plasminogen in vitro. PA activity was then quantitated by [125I]fibrin lysis assay, and high- and low-activity subclones were isolated; these retained high- or low-activity phenotypes. Syngeneic newborn hamsters were inoculated with these subclones and observed for the appearance of palpable tumors. A strong correlation between enzyme activity and tumor formation was observed in four separate trials; animals receiving high-PA subclones developed tumors more rapidly than those inoculated with the parental cell line. Tumors were also excised from test animals, and the cell lines established from the tumors were tested in vitro at different passages for their ability to activate plasminogen. These tumor cells were then reinoculated into syngeneic animals to confirm the tumorigenicity of cell lines with high fibrinolytic activity. In these experiments, the positive correlation between PA production and tumorigenicity was confirmed.

Transcriptional induction of proto-oncogene fos by HSV-2

HSV-2 induces the transcription of c-fos gene in both human (diploid) cell strains and mouse (heteroploid) cell lines. HSV-1 is incapable of such induction. The induction of transcription is rapid and transient in both cell types. The product of transcriptional induction of c-fos in mouse cells is mainly a 4.5 kb fos mRNA along with lesser amount of a 2.2 kb fos mRNA, while in human cells the 4.5 kb mRNA is the only detectable product. Both the 4.5 kb and 2.2 kb fos mRNAs are mature gene products as judged by their presence exclusively in the cytoplasm of infected mouse L929 cells, while a 3.5 kb putative precursor of the 2.2 kb fos mRNA appears exclusively in the nucleus. In infected human WI38 cells, the 4.5 kb mRNA also appears exclusively in the cytoplasm. Virus specific protein synthesis is an absolute requirement for the transcriptional activation. The 4.5 kb fos mRNA is under different control mechanisms since it is not induced by serum stimulation of serum starved cells as is the 2.2 kb fos transcript. Moreover, in serum starved cells simultaneously stimulated by serum and infected, only the 2.2 kb fos transcript can be superinduced by the protein synthesis inhibitor cycloheximide, while the appearance of the 4.5 kb fos mRNA is completely blocked by this treatment.

Cellular gene induction during herpes simplex virus infection can occur without viral protein synthesis

Infection of cultured cells with herpes simplex virus (HSV) results in the transcriptional induction of a small number of cellular genes. Although the majority of such genes are dependent upon viral protein synthesis for their induction, a small minority are not. These genes are induced by events occurring prior to the onset of viral protein synthesis, in particular by binding of the virus to the cell surface and cellular entry of the virion. The significance of such cellular gene induction early in viral infection is discussed in terms of virus-cell interaction in general and the mechanism of transformation by HSV in particular.

In vivo transformation of human skin with human papillomavirus type 11 from condylomata acuminata

Human papillomaviruses (HPVs) have been implicated in the development of a number of human malignancies, but direct tests of their involvement have not been possible. We describe a system in which human skin from various sites was infected with HPV type 11 (HPV-11) extracted from vulvar condylomata and was grafted beneath the renal capsule of athymic mice. Most of the skin grafts so treated underwent morphological transformation, resulting in the development of condylomata identical to those which occur spontaneously in patients. Foreskins responded with the most vigorous proliferative response to HPV-11. The lesions produced the characteristic intranuclear group-specific antigen of papillomaviruses. Both dot blot and Southern blot analysis of DNA from the lesions revealed the presence of HPV-11 DNA in the transformed grafts. These results demonstrate the first laboratory system for the study of the interaction of human skin with an HPV. The method may be useful in understanding the mechanisms of HPV transformation and replication and is free of the ethical restraints which have impeded study. This system will allow the direct study of factors which permit neoplastic progression of HPV-induced cutaneous lesions in human tissues.

Combined effect of herpes simplex virus and tobacco on the histopathologic changes in lips of mice

In the present study we have examined the combined effect of HSV-1 inoculation and tobacco application (snuff water extract or smoking tar condensate) on the histopathologic changes of mouse labial mucosa. Two months' exposure to tobacco or HSV-1 inoculation alone did not induce dysplasia in the epithelium of labial mucosa, while HSV-1 inoculation combined with snuff water extract or smoking tar condensate produced epithelial dysplasia and other histomorphologic changes (that is, hyperkeratosis, increased granular cell layer thickness, acanthosis, and increased inflammatory cell infiltration in a significant number of animals). This result indicates that HSV-1 and tobacco could possibly act synergistically in the development of precancerous oral lesions and oral cancer.

Oral carcinoma: evidence for viral oncogenesis

Since early this century, when Rous (1911) first demonstrated the association of a tumour (chicken sarcoma) with a transmissible agent, evidence has accumulated on possible associations between viruses and various neoplasms. There is now conclusive evidence linking some RNA viruses (Temin, 1972) and DNA viruses (Rapp, 1973) with tumours in animals--including sub-human primates (Leading article, 1982). Indeed, a serious complication of hepatitis B infection in man is now recognised to be hepatocellular carcinoma. (Editorial, 1982). The evidence association other viruses with human neoplasms is not unequivocal but there are strong associations between, for example, herpesviruses and some human malignant neoplasms (Klein, 1972; Rapp, 1973; zur Hausen, 1975).

Characterization of mRNAs that map in the BglII N fragment of the herpes simplex virus type 2 genome

The BglII N DNA fragment (0.580 to 0.620 map units) of herpes simplex virus type 2 strain (333) is of interest because of its transforming potential. This fragment contains either partial or the complete coding sequences for nine mRNA transcripts that can be detected during a lytic infection. Subclones of the BglII N DNA fragment were generated in plasmid vectors, and the approximate locations of the mRNA transcripts were mapped by RNA blot hybridization technology. Precise 5' or 3' ends (or both) of these mRNA species were determined by S1 nuclease mapping, using the BglII N subclones as DNA probes. At least four mRNA transcripts are fully encoded in the BglII N fragment. The coding regions for all of the mRNA transcripts are densely packaged along the BglII N fragment with less than 150 base pairs between neighboring mRNA ends. Analysis of both neutral and alkaline gels failed to reveal the presence of any detectable introns. This manuscript reports a detailed transcription map for this region.

Small fragments of herpesvirus DNA with transforming activity contain insertion sequence-like structures

A 737-base-pair fragment of herpes simplex virus type 2 DNA with morphological-transforming ability was identified by transfecting into rodent cells deleted fragments of the left-hand end of the Bgl II N fragment region (map position 0.58-0.625), which were constructed in vitro. The transforming sequences lie within the coding region for a Mr 61,000 protein, but the fragment itself does not appear to specify a viral polypeptide. Contained within the transforming fragment are sequences that can be drawn as a stem-loop structure flanked by direct repeats, similar to an insertion sequence-like element. An insertion sequence-like structure was also found in a small fragment of human cytomegalovirus DNA that has transforming activity. Possible mechanisms of herpesvirus transformation are discussed.

Current knowledge of mechanisms of viral carcinogenesis

Retroviruses are RNA-containing viruses using reverse transcriptase to produce DNA copies capable of insertion into host chromosomes. Appropriate genes are required to confer transforming ability to retroviruses. The src gene, a 60,000-dalton protein with protein kinase activity, is required by avian viruses to induce sarcomas. Normal cells have a gene (sarc) similar to the src gene. Retroviruses with oncogenic properties can arise by recombining with genes on the host chromosome. Herpesviruses, adenoviruses, and papovaviruses have transforming properties residing in only a portion of the genome. Probably, only one to two genes are required for transformation, regardless of the complexity of the virus.

Viruses in the etiology of atherosclerosis

To examine the possible role of viruses in the etiology of atherosclerosis, we searched for the presence of viral genomes in arterial tissues by in situ hybridization. Because chickens infected with Marek disease virus, a herpesvirus, develop atherosclerotic lesions after infection, we looked for the presence of herpesvirus or parts thereof in human artery wall tissue, particularly in individuals with evidence of atherosclerosis. Herpesvirus probes were used on specimens of aortic wall removed from patients undergoing coronary bypass surgery. Evidence for the presence of herpes simplex viral mRNA was obtained in 13 specimens. Some of the specimens positive for herpes simplex virus appear to represent early stages in atherogenesis. Evidence for the presence of cytomegalovirus or Epstein-Barr viral genome was not observed in any of the specimens examined. We have also shown that herpes simplex virus can infect human fetal smooth muscle cells in culture. There are several ways in which viruses could operate in the pathogenesis of atherosclerosis: They could induce proliferation of artery wall intimal smooth muscle cells via injury or by genomic alterations leading to clonal expansion of intimal smooth muscle cell populations. We suggest that expression of at least a part of the herpesvirus genome in arterial smooth muscle cells may in some cases be instrumental in initiating or maintaining this enhanced cell proliferation. Furthermore, viral agents could explain other puzzling features in the occurrence of atherosclerosis and the attendant heart disease and strokes.