Anti-herpes simplex virus activities of crude water extracts of Thai medicinal plants.

A number of Thai medicinal plants, recommended as remedies for herpesvirus infection and have been used in primary health care were investigated for their intracellular activities against herpes simplex viruses (HSV). Centella asiatica L., Maclura cochinchinensis Cornor, and Mangifera indica L. contained both anti-HSV-1 and -2 activities, as determined by plaque inhibition assay. An inhibition of the production of infectious HSV-2 virions from infected Vero cells could also be demonstrated. Combinations of each of these reconstituted extracts with 9-(2-hydroxyethoxymethyl) guanosine (acyclovir; ACV) resulted either in subadditive, additive, or synergistic interaction, against HSV-2, depending on the dose of ACV used; mixture of C. asiatica and M. indica exerted an additive effect in a similar assay. Furthermore, the inhibitory effects of these plant extracts were also substantiated by flow cytometric analysis of virus-specific antigens in the infected cells. The active constituent present in C. asiatica extract was determined to be asiaticoside while in M. indica was mangiferin. Thus, these data suggest therapeutic potential of these plant extracts.     

Anti-herpes simplex virus activity of sulfated galactans from the red seaweeds Gymnogongrus griffithsiae and Cryptonemia crenulata

This study presents the chemical composition and antiviral activity against herpes simplex virus type 1 (HSV-1) and 2 (HSV-2) of sulfated galactan crude extracts and main fractions obtained from two red seaweeds collected in Brazil, Gymnogongrus griffithsiae and Cryptonemia crenulata. Most of the eighteen tested products, including homogeneous kappa/iota/nu carrageenan and DL-galactan hybrid, exhibited antiherpetic activity with inhibitory concentration 50% (IC50) values in the range 0.5-5.6 microg/ml, as determined in a virus plaque reduction assay in Vero cells. The galactans lacked cytotoxic effects and showed a broad spectrum of antiviral activity against HSV-1 and HSV-2. No direct virus inactivation was observed after virion treatment with the galactans. The mode of action of these compounds could be mainly ascribed to an inhibitory effect on virus adsorption. Most importantly, a significant protection against a murine vaginal infection with HSV-2 was afforded by topical treatment with the sulfated galactans.     

Anti-herpes simplex virus efficacies of 2-aminobenzamide derivatives as novel HSP90 inhibitors

After the widespread use of the acyclic purine nucleoside analogues for therapy of herpes simplex virus (HSV) infection since the 1980s, new antiviral strategies are urgently needed to counter the emergence of drug-resistant clinical isolates. In this report, we define the anti-HSV efficacies of three optimized 2-aminobenzamide derivatives in vitro and in vivo. The synthetic analogues SNX-25a, SNX-2112 and SNX-7081, which selectively bind to the N-terminal ATP pocket of heat shock protein 90 (HSP90), exhibited significant anti-HSV-1 and HSV-2 activities at non-cytotoxic concentrations in Vero cells, with EC(50) values close to that of acyclovir (ACV). The in vivo antiviral potentials were then confirmed using a herpes simplex keratitis (HSK) rabbit model, where eye gels containing 0.1% or 0.025% SNX-25a displayed the highest efficacies against HSV-1 infection, which were better than that obtained with 0.1% ACV. SNX-2112 and SNX-7081 gels were also effective against HSV-1 with different magnitude of activities. Our results for the first time confirmed the anti-HSV efficacies of these 2-aminobenzamide derivatives and suggest that with alternative mechanisms of action these novel HSP90 inhibitors, especially SNX-25a, could be potent as new anti-HSV clinical trial candidates.     

Flavonoids from Maclura tinctoria.

Seven flavonoids, including two new natural products, were isolated from an ethanol extract of the bark of Maclura tinctoria (L.) Gaud. The new compounds are steppogenin 4'-O-beta-D-glucoside and orobol 5,3'-di-O-methyl-8-C-glucoside. Orobol, steppogenin, aromadendrin, dihydromorin and orobol 7-O-beta-D-glucoside were also isolated.     

Anatomy of herpes simplex virus DNA. VI. Defective DNA originates from the S component.

We previously reported that serial propagation of the Justin strain of herpes simplex virus 1 [HSV-1 (Justin)] results in the generation of defective DNA molecules consisting of tandem repetitions of sequences of limited complexity. In the present study, HSV-1 DNA was cleaved with the restriction endonucleases BglII and EcoRI. The fragments were electrophoretically separated on agarose gels, transferred to nitrocellulose strips, and then hybridized with 32P-labeled HSV-1 (Justin) defective DNA. The data allow us to conclude that DNA sequences contained in the repeat unit of defective DNA originate from the S segment of the wild-type viral DNA molecule.     

Synthesis of herpes simplex virus DNA in isolated chromatin.

Herpes simplex virus DNA synthesis was studied in isolated chromatin (HSV chromatin) of African green monkey kidney (RC-37) cells after HSV type 1 infection. After optimizing the in vitro system, HSV chromatin was shown to synthesize both viral and cellular DNA at ratios identical with those seen in vivo. After 30 min of DNA synthesis in vitro, the DNA products were identical in size to the prelabeled parental DNA. More than 60% of the newly synthesized single-stranded DNA fragments sedimented with a sedimentation constant of greater than 10 S. HSV DNA polymerase was found to be responsible for the synthesis of 80% of all in vitro made viral and most likely also cellular DNA sequences.     

Pomiferin, histone deacetylase inhibitor isolated from the fruits of Maclura pomifera

The major constituents from the fruits of Maclura pomifera are the prenylated isoflavones, osajin (1) and pomiferin (2). Their structures were elucidated using NMR spectroscopic techniques and mass spectrometric analysis. Compound 2 showed potential inhibitory activity in histone deacetylase (HDAC) enzyme assay. It also exhibited growth inhibitory activity on five human tumor cell lines and more sensitive inhibitory activity on the HCT-15 colon tumor cell line. Further structure-activity relationships of position 3 on ring B from aromatic ring will be reported in due course.     

Anti-herpes simplex virus effect of a seed extract from the tropical plant Licania tomentosa (Benth.) Fritsch (Chrysobalanaceae)

Incubation of acyclovir-resistant herpes simplex virus type 1 (ACVr-HSV1), during infection of the HEp-2 cell culture, with an extract prepared from the seeds of Licania tomentosa (Benth.) Fritsch (Chrysobalanaceae) species impaired the productive replication of this virus in a concentration-dependent manner. The extract was able to inhibit extracellular virus (virucidal effect) and also interfered with a very early event of cell infection, at a non-cytotoxic concentration.     

Herpes simplex virus glycoprotein D mediates interference with herpes simplex virus infection.

We showed that the expression of a single protein, glycoprotein D (gD-1), specified by herpes simplex virus type 1 (HSV-1) renders cells resistant to infection by HSV but not to infection by other viruses. Mouse (LMtk-) and human (HEp-2) cell lines containing the gene for gD-1 under control of the human metallothionein promoter II expressed various levels of gD-1 constitutively and could be induced to express higher levels with heavy metal ions. Radiolabeled viruses bound equally well to gD-1-expressing and control cell lines. Adsorbed viruses were unable to penetrate cells expressing sufficient levels of gD-1, based on lack of any cytopathic effects of the challenge virus and on failure to detect either the induction of viral protein synthesis or the shutoff of host protein synthesis normally mediated by a virion-associated factor. The resistance to HSV infection conferred by gD-1 expression was not absolute and depended on several variables, including the amount of gD-1 expressed, the dosage of the challenge virus, the serotype of the challenge virus, and the properties of the cells themselves. The interference activity of gD-1 is discussed in relation to the role of gD-1 in virion infectivity and its possible role in permitting escape of progeny HSV from infected cells.     

Virion component of herpes simplex virus type 1 KOS interferes with early shutoff of host protein synthesis induced by herpes simplex virus type 2 186.

Herpes simplex virus (HSV) strains HSV type 1 (HSV-1) KOS and HSV-2 186 are representative of delayed and early shutoff strains, respectively, with regard to their ability to inhibit protein synthesis in Friend erythroleukemia cells. When these cells were simultaneously infected with HSV-1 KOS and HSV-2 186, HSV-1 KOS interfered with the rapid suppression of globin synthesis induced by HSV-2 186. The observed interference was competitive and not due to exclusion of HSV-2 by HSV-1 at the level of adsorption. Furthermore, UV-irradiated HSV-1 KOS was also effective at interfering with the early shutoff function of HSV-2 186, indicating that a virion component is responsible for the observed interference.     

In vitro synthesis of DNA in nuclei isolated from human lung cells infected with herpes simplex type II virus.

An isolated nuclei system prepared from herpes type II- and mock-infected human embryonic lung cells is able to synthesize cellular and viral DNA in the same proportion as in vivo at various times after infection. Incorporation of (3H)TTP in the in vitro reaction mixture requires Mg2 plus and ATP. Overall in vitro DNA synthesis in nuclei isolated from herpes-infected cells is semiconservative as demonstrated by bromodeoxyuridine-substituted DNA density-transfer experiments, but exhibits a significant fraction of repair-type replication. Relative rates of total DNA synthesis in vitro and in vivo are the same any time after infection. Isolated nuclei synthesize cell and viral DNA for a length of time and at a rate dependent upon the incubation temperature, but there are differences in the length of time of linear in vitro DNA synthesis between herpes- and mock-infected cells. The temperature optima for in vitro DNA synthesis differ significantly for herpes- and mock-infected cells, and are the same for cells abortively infected with herpes type II as for mock-infected cells.     

Protease-deficient herpes simplex virus protects mice from lethal herpesvirus infection.

Null mutants and attenuated mutants of herpes simplex virus (HSV) have been shown to induce immunity against challenge from wild-type virus. Null viruses with a defect in late gene products would be expected to express more viral genes than viruses with defects in essential early gene products and thus induce a better immune response. Herpesviruses encode a late gene product (serine protease) that is autocatalytic and cleaves the capsid assembly protein during viral replication. To determine whether a virus with a mutation in this gene could induce immunity, we constructed a recombinant virus containing the gusA reporter gene in the protease domain of the HSV type 1 UL26 open reading frame (ORF). Consistent with previous results (M. Gao, L. Matusick-Kumar, W. Hurlburt, S. F. DiTusa, W. W. Newcomb, J. C. Brown, P. J. McCann, I. Deckman, and R. J. Colonno, J. Virol. 68:3702-3712, 1994), recombinant virus could be isolated only from helper cell lines expressing the product of the UL26 ORF. Mice inoculated with the recombinant virus were unaffected by doses of virus that were lethal to mice infected with wild-type virus. Mice which were previously inoculated with the recombinant virus were also protected by a subsequent challenge with wild-type virus in a dose-dependent manner. These results indicate that recombinant viruses lacking the protease gene are avirulent but render protection from subsequent challenge.