Effect of cloned human interferons on the replication of and cell fusion induced by herpes simplex virus

Evaluation of imiquimod 5% cream to modify the natural history of herpes labialis: a pilot study

BACKGROUND

Imiquimod is currently approved for the treatment of genital warts and has been shown to decrease recurrences of genital herpes in the guinea pig model of genital herpes. Therefore, we evaluated the safety and potential of topical imiquimod to decrease the rate of recurrence in humans with a history of recurrent herpes labialis.

METHODS

Forty-seven subjects with recurrent herpes labialis applied imiquimod 5% (n=30) or vehicle cream (n=17) to recurrent lesion(s) on days 1, 3, and 5 of the study (day 1 of observation occurred within 48 h after recurrence of lesion). Subjects were seen at the study centers between each dose and 3 days after application of the final dose or until resolution of the lesion.

RESULTS

After application to recurrent lesions, local erythema, edema, scabbing and/or flaking, pain, burning, and maximal lesion size were significantly greater in the imiquimod group than in the vehicle group. The study was terminated early because of severe local adverse events that occurred in 5 recipients of imiquimod. The median time until the next recurrence was, however, increased from 50 days in the vehicle group to 91 days in the imiquimod group (P=.018).

CONCLUSIONS

Application of imiquimod 5% cream to herpes labialis lesions was associated with a delay in the time to the first recurrence after treatment, but severe local inflammation occurred in some individuals.

IFN-alpha1 plasmid construct affords protection against HSV-1 infection in transfected L929 fibroblasts

The purpose of the present study was to evaluate the resistance against herpes simplex virus type 1 (HSV-1) using an interferon-alpha1 (IFN-alpha1) transgene in specifically targeted cells in vitro. Transfection of mouse fibroblast L929 cells with an IFN-alpha1 plasmid construct reduced viral load and viral gene expression in a time-dependent fashion. Supernatants from IFN-alpha1-transfected cells augmented natural killer (NK) cell activity, and such an effect was antagonized with neutralizing antibody to IFN-alpha/beta. In addition, transfected cells displayed an increase in the IFN inducible genes (2',5'-oligoadenylate synthetase [2',5'-OAS], T cell-specific guanine nucleotide triphosphate-binding protein, IFN regulatory factor 1 [IRF-1], and major histocompatibility complex [MHC] class I) compared with plasmid vector-treated controls. Collectively, these results show that IFN-alpha1 transfection of cells in vitro induces or upregulates a spectrum of IFN-regulated genes involved in the direct or indirect antiviral action of this cytokine. In addition, the transgene significantly increases the resistance of transfected cells in vitro to HSV-1 infection.

Human interferon reduces surface expression but not total production of herpes simplex virus type 1 glycoproteins gC and gE in heterologous hamster cells

The effect of interferon (IFN) on herpes simplex virus type 1 (HSV-1)-induced glycoproteins gC and gE was investigated in a heterologous IFN/cell model. In this model, the effect on surface expression of the glycoproteins could be studied separately from the effect on virus multiplication. Pretreatment of baby hamster kidney cells (BHK) with heterologous human leukocyte IFN suppressed surface expression of HSV-1-encoded gC and gE but had no influence on total production of the glycoproteins. This was in contrast to the effect on human embryonic fibroblast cells (HE) (homologous IFN and cells), where surface expression as well as total production of glycoproteins were reduced. The surface expression was demonstrated by antibody-sensitized monodisperse polystyrene beads, and immunoblotting and two-dimensional electrophoretic analysis of radioisotope-labeled proteins were used to study the total production.

Effect of protein kinase C inhibitors on the antiviral activity of human alpha interferon in herpes simplex virus-infected human neuroblastoma cells

Pretreatment of human neuroblastoma cells with an inhibitor of protein kinase C (PKC), staurosporine or H-7, prior to the addition of human alpha interferon (HuIFN-alpha), recombinant HuIFN-alpha, or recombinant HuIFN-beta blocked the inhibitory effect of these IFNs on the release of infectious herpes simplex virus type 1 from treated cells. In addition, staurosporine blocked the inhibitory effect of HuIFNs on the expressions of herpes simplex type 1 glycoproteins B, C, and D in treated neuroblastoma cells. Furthermore, addition of HuIFNs resulted in an increased expression of PKC in treated neuroblastoma cells. These results suggest that inhibitors of PKC block the expression of HuIFN-induced genes in treated human neuroblastoma cells. Thus, the activation of PKC is an important step in the HuIFN-treated cells of neuronal origin.

Inhibition of human immunodeficiency virus type 1-induced cell fusion by recombinant human interferons

Pretreatment of HeLa T4 cells with recombinant alpha, beta, or gamma interferon (IFN) was found to significantly inhibit syncytium formation induced by the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein. All three IFNs were found to be potent inhibitors of fusion in a system in which Spodoptera frugiperda cells, infected with a baculovirus recombinant expressing the HIV-1 envelope protein, were cocultivated with HeLa T4 cells. In addition, these IFNs were also found to block HeLa T4 cell fusion induced by the HIV-1 envelope proteins expressed from a vaccinia virus recombinant. Furthermore, the IFNs inhibited cell fusion between HIV-1 envelope glycoprotein-expressing cells and either immortalized or fresh CD4+ lymphocytes pretreated with the IFNs. These results suggest that further testing of human IFNs for therapy of HIV-1 infection will be of interest.

Effect of interferon treatment on expression of gC and gE glycoproteins in herpes simplex virus-infected cells

The effect of interferon treatment on the herpes simplex virus type 1 (HSV-1)-specific glycoproteins gC and gE in homologous and heterologous cells has been investigated. In human embryonic fibroblastic cells, human leukocyte interferon inhibited virus multiplication and expression of the HSV-1-specific glycoproteins gC and gE on the cell surface in a dose-dependent manner. In heterologous baby hamster kidney cells, the human interferon had no effect on virus multiplication. However, the surface expression of the HSV-1-specific glycoproteins was reduced, as shown by erythrocyte rosette formation, by attachment of monodisperse polystyrene particles coated with antibodies and by immunogold scanning electron microscopy.

Inhibition of virus-induced cell fusion by apolipoprotein A-I and its amphipathic peptide analogs

Apolipoprotein A-I (apoA-I), the major protein component of serum high-density lipoproteins (HDL), was found to inhibit herpes simplex virus (HSV)-induced cell fusion at physiological (approximately 1 microM) concentrations, whereas HDL did not exert any inhibitory effect. Lipid-associating, synthetic amphipathic peptides corresponding to residues 1-33 (apoA-I[1-33]) or residues 66-120 (apoA-I[66-120]) of apoA-I, also inhibited HSV-induced cell fusion, whereas a peptide corresponding to residues 8-33 of apoA-I (apoA-I[8-33]), which fails to associate with lipids, did not exert any inhibitory effect. These results suggest that lipid binding may be a prerequisite for peptide-mediated fusion inhibition. Consistent with this idea, a series of lipid-binding 22-amino-acid-residue-long synthetic amphipathic peptides that correspond to the amphipathic helical domains of apoA-I (A-I consensus series), or 18-residue-long model amphipathic peptides (18A series), were found to exert variable levels of fusion-inhibitory activity. The extent of fusion-inhibitory activity did not correlate with hydrophobic moment, hydrophobicity of the nonpolar face, helix-forming ability, or lipid affinity of the different peptides. Peptides in which the nonpolar face was not interrupted by a charged residue displayed greater fusion-inhibitory activity. Also, the presence of positively charged residues at the polar-nonpolar interface was found to correlate with higher fusion-inhibitory activity.

Expression of herpes simplex virus type 1 glycoproteins in interferon-treated human neuroblastoma cells

Human alpha interferon (IFN) significantly inhibits the replication of herpes simplex virus type 1 in human neuroblastoma cells. This inhibitory effect can be blocked by pretreatment with antiserum to IFN. We observed no significant differences in the expression of major nucleocapsid proteins, including VP5, between IFN-treated and untreated neuroblastoma cells. Electron micrographs demonstrated that there were distinct viral nucleocapsids within IFN-treated neuroblastoma cells. The expression of glycoproteins B and E was significantly reduced in these IFN-treated cells. On the other hand, glycoprotein D, although reduced in quantity, was expressed after IFN treatment. An immunofluorescence assay of the IFN-treated and virus-infected cells detected glycoprotein D in the Golgi complexes and in the nuclear membranes. Our results indicate that human alpha IFN may be useful in the study of gene expression in IFN-treated cells of neuronal origin.

Antiviral effects of apolipoprotein A-I and its synthetic amphipathic peptide analogs

Apolipoprotein A-I (apo A-I), the major protein component of serum high density lipoproteins, was found to inhibit herpes simplex virus (HSV)-induced cell fusion at physiological (approximately 1 microM) concentrations. An 18 amino acid-long synthetic amphipathic alpha-helical peptide analog of apo A-I (18A) was also found to inhibit HSV-induced cell fusion at similar concentration (approximately 2 microM). Dimers of 18A connected via a proline (37pA) or an alanine (37aA) residue also inhibited virus-induced cell fusion at similar concentration, suggesting that the presence of a proline turn does not influence the antiviral activity of the amphipathic peptides. However, a peptide analog 18R, in which the distribution of charged residues was reversed, inhibited virus-induced cell fusion only at a higher (approximately 125 microM) concentration, suggesting that the anti-viral activity of the amphipathic peptide is strongly influenced by the nature of the charge distribution at the polar-nonpolar interface. Consistent with their ability to inhibit virus-induced cell fusion, the peptides inhibited the spread of HSV infection as demonstrated by a 10-fold reduction in the virus yield, when virus-infected cells were maintained in the presence of amphipathic peptides. The amphipathic peptides also inhibited penetration of virus into cells, but did not exert any effect on virus adsorption. A nearly complete inhibition of virus penetration was observed when the virus, or both virus and cells, was pretreated with the peptide, suggesting that the peptides may have a direct effect on the virus. The results indicate that amphipathic helices may be useful in designing novel antiviral agents that inhibit penetration and spread of enveloped viruses.

Ocular avirulence of a herpes simplex virus type 1 strain is associated with heightened sensitivity to alpha/beta interferon

BALB/c mice infected on the scarified cornea with herpes simplex virus type 1 strain 35 [HSV-1(35)] rarely developed ocular disease even at challenge doses as high as 10(7) PFU per eye. In contrast, HSV-1(RE) consistently induced stromal keratitis at an inoculum of 2 x 10(4) PFU. The goal of this study was to determine the reason for the difference in virulence between the two HSV strains. Both HSV-1 strains replicated to similar titers in excised corneal "buttons." However, after in vivo infection of the cornea, the growth of strain 35 was evident only during the first 24 h postinfection, whereas the replication of strain RE persisted for at least 4 days. In vitro tests revealed that HSV-1(35) was greater than 10 times more sensitive to alpha/beta interferon (IFN-alpha/beta) than HSV-1(RE). Both strains induced comparable serum levels of IFN after intraperitoneal inoculation. The kinetics of HSV-1(35) clearance from the eye was markedly altered by treatment with rabbit anti-IFN-alpha/beta. Virus titers exceeding 10(4) PFU per eye could be demonstrated 4 to 5 days postinfection in mice given a single inoculation of antiserum 1 h after infection. Furthermore, anti-IFN treatment in 3-week-old mice infected with HSV-1(35) led to the development of clinically apparent corneal disease which subsequently progressed to stromal keratitis in the majority of recipients. These results indicate that the striking difference in the capacity of HSV-1(35) and HSV-1(RE) to induce corneal disease was related to the inherently greater sensitivity of strain 35 to IFN-alpha/beta produced by the host in response to infection.

Individual NK cell clones lyse both tumor cell targets and herpes simplex virus-infected fibroblasts in the absence of interferon

The target specificity of natural killer (NK) cells for either tumor cells or virus-infected cells has been investigated. Lymphocyte clones with the surface phenotype of NK cells (CD3-, CD16+) were obtained by limiting dilution of peripheral blood mononuclear cells stimulated with PHA, Herpes simplex virus type 1 (HSV-1), or Varicella-Zoster antigens. Clones were maintained in media with recombinant interleukin 2 (IL-2). Both NK-sensitive (K562 cells) and NK-resistant (Raji cells) targets were lysed by three cloned lines of NK cells. The ability to lyse NK-resistant target cells was largely lost when the cloned lymphocytes were cultured overnight in the absence of IL-2. Effector cells from all three clones were also capable of specifically lysing HSV-1 infected human fibroblasts in comparison with uninfected fibroblasts. We also showed that lysis of HSV-1 infected targets by NK cloned cells was independent of interferons in the culture system.

Characterization of the early steps of herpes simplex virus replication in interferon-treated human cells

Interferon (IFN) was shown to inhibit herpes simplex virus type 1 (HSV-1) replication at the transcription of the immediate early (alpha) genes. This apparent inhibition could be due to a direct effect on viral transcription or on one of the preceding steps of infection, i.e., penetration and uncoating. In the present study, we analyze the effects of IFN on the very early steps of HSV-1 infection in HEp-2 human cells. Analysis of the parental HSV-1 viral DNA accumulated in the infected cell nuclei indicated that viral DNA penetration, migration to the nuclei, and stability were not affected by IFN treatment. To analyze the effect of IFN on the uncoating of the parental HSV-1 DNA following infection, we developed a technique based on DNase I sensitivity of the infecting viral DNA genome. Within 1 h of infection, the parental viral DNA became sensitive to DNase I digestion. HSV-1 DNA in the nuclei of both control and IFN-treated cells was equally sensitive to DNase I digestion, suggesting that IFN's mode of action was unrelated to the uncoating of HSV-1 virions. Because IFN does not affect the events in the HSV-1 lytic cycle prior to the onset of the immediate-early gene transcription, it appears that IFN exerts a direct effect on this process.

Defective transport of hemagglutinin-neuraminidase glycoprotein of bovine parainfluenza-3 virus in interferon treated cell

A defective transport of bovine parainfluenza-3 virus (PI-3V) hemagglutinin-neuraminidase (HN) glycoprotein was evidenced in interferon (IFN)-treated bovine turbinate (BTu) cells. Indirect immunofluorescence performed with monoclonal antibody to PI-3 HN glycoprotein demonstrated accumulation of this protein in the perinuclear cytoplasm of IFN-treated cells. Untreated, infected control cells had a generalized widespread fluorescence. Unfixed control cells showed a uniform surface fluorescence in contrast to a few specs of fluorescence on the plasma membrane of IFN-treated cells. Electron microscopic localization of HN protein was done by immuno-gold ultrastructural cytochemistry. Untreated cells had uniform gold label on the plasma membrane and around the budding virus particles with no label in the cytoplasm. In IFN-treated cells, however, there was an accumulation of gold particles in the cytoplasm with only a few particles on the cell surface. Quantitative analysis of HN protein on the cell surface by solid phase radioimmune-assay revealed a greater amount of this protein on the surface of control cells, than those on the IFN-treated cells.

Effect of recombinant hybrid human interferon on replication and morphogenesis of HSV-1 in monkey cells

Human recombinant alpha interferon, A/D, significantly reduced the replication and cell fusion induced by herpes simplex virus type 1 in monkey cells. Thin-section electron microscopy of interferon-treated monkey cells showed distinct assembly of nucleocapsids within the nucleus. Analysis of virus-specific proteins by the immunoblot technique confirmed that A/D interferon had no significant effect on the expression of major nucleocapsid proteins, although the expression of glycoproteins B and D was reduced in interferon-treated cells. The possibility of an interferon-induced block at a late stage in virus morphogenesis is discussed.

Interferon treatment inhibits onset of herpes simplex virus immediate-early transcription

Pretreatment of primary cultures of splenic mouse macrophages with murine IFN-alpha/beta leads to a stable inhibition of herpes simplex virus type 1. Analysis of viral DNA, RNA, and protein synthesis identifies expression of "immediate-early" genes as a major target of IFN-mediated inhibition. Determination of viral DNA in the nuclei early after infection, i.e., before onset of DNA replication, suggests that virus uptake, transport to the nucleus, and DNA stability are not decreased in IFN-pretreated macrophages. Nuclear runoff transcription analysis shows a significant reduction of immediate-early transcription rates following IFN treatment. End-specific probes for the ICP4 gene locate the inhibition to the onset of transcription. Northern blot analysis reveals a decrease in ICP4 transcripts in accordance with the observed inhibition of transcription. The observed inhibition of early gene transcription may be a consequence of decreased immediate-early gene expression.

Effect of cloned human interferon-alpha 2a on bovine parainfluenza-3 virus. Brief report

Pretreatment of bovine turbinate (BTu) cells with cloned human interferon (IFN)-alpha 2a reduced the yield of infectious bovine parainfluenza-3 virus (PI-3 V). Intracellular synthesis of HN glycoprotein was reduced on postinfection day 1 (PID 1), but it recovered to normal levels subsequently. However, reduction of this protein persisted in the released virus through PID 2. Thin section electron microscopy demonstrated a drastically reduced release of mature virions and an accumulation of viral nucleocapsids inside the cytoplasm on PID 2. These results suggest that cloned human IFN-alpha 2a affects the glycoprotein synthesis, and morphogenesis of bovine PI-3 V, and thus inhibits the release of viral particles from treated cells.

Effect of interferon on replication of herpes simplex virus types 1 and 2 in human macrophages

Macrophages derived from human peripheral blood and cultured for 1 week were permissive for the replication of herpes simplex virus (HSV) types 1 and 2. Low titers of interferon (IFN) were produced after virus infection. The yield of infectious virions was reduced by pretreatment of cells with natural and recombinant IFN-alpha and natural IFN-beta. Recombinant and natural IFN-gamma exhibited very low antiviral activity. Treatment of cells with IFN-gamma mixed with IFN-alpha or with IFN-beta did not result in a synergistic inhibition of virus yield. We studied the synthesis of HSV type 1- and HSV type 2-coded proteins in macrophages treated with IFN-beta. Induction of the HSV beta-protein DNA polymerase was strongly inhibited in IFN-treated cells in a dose-dependent manner. As shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, other beta- and gamma-proteins of HSV were inhibited as well. Immunofluorescence studies revealed a strong inhibition of the expression of immediate early alpha-protein ICP4. The results indicate that IFN acts early during the viral replication cycle to inhibit the synthesis of HSV alpha- and beta-proteins.

Studies on herpes simplex virus type 1 glycoproteins using monoclonal antibodies

Monoclonal antibodies against herpes simplex virus type 1 glycoproteins were isolated and utilized to study the synthesis and processing of glycoproteins B, C, and D (gB, gC, gD, respectively). Monoclonal antibodies against both gB and gD had higher virus-neutralizing activity when compared to that of gC. Differences among these glycoproteins were observed in their time of appearance in the virus-infected cells. The presence of gD was detected at a very early stage of infection when compared to gB and gC. The localization of these glycoproteins during their synthesis and processing was studied.

Synthesis of herpes simplex virus proteins and nucleic acids in interferon-treated macrophages

Mouse macrophages grown from spleen cells were found to be very sensitive to the interferon (IFN) activity against herpes simplex virus type 1 (HSV-1). Therefore we have used these cells to investigate the level at which IFN blocks the replication of HSV-1. IFN treatment resulted in a strong inhibition of the induction of HSV DNA polymerase and other beta proteins. RNA hybridization experiments revealed that the amount of mRNA for the beta protein thymidine kinase was strongly reduced in IFN treated HSV-1 infected cells. Analysis of the effect of IFN on expression of the alpha genes indicated a strong inhibition of alpha protein synthesis. In contrast the synthesis of mRNA of the alpha protein ICP 4 was only moderately inhibited. The results indicate that IFN primarily acts on the translation of HSV alpha proteins.

Effect of cloned human interferons on protein synthesis and morphogenesis of herpes simplex virus

Pretreatment of human fibroblast cells with 100 U of either cloned human alpha-2 or beta interferon per ml for 24 h reduced the release of infectious herpes simplex virus type 1 by more than 99%. This inhibition in infectivity correlated well with the total number of extracellular virus particles released from treated cells as determined by DNA dot blot hybridization analysis. Electron microscopic observations of interferon-treated human fibroblast cells clearly demonstrated typical assembly of nucleocapsids inside the nucleus, even though very few mature extracellular particles were seen. Analysis of virus-specific proteins by the immunoblot technique showed that neither species of interferon had a significant inhibitory effect on the synthesis of major nucleocapsid proteins. However, the synthesis of specific glycoproteins (D and B) was drastically reduced or delayed in beta-interferon-treated cells. The results presented in this communication suggest that cloned human interferons block herpes simplex virus morphogenesis at a late stage and inhibit the release of particles from the treated cells.