New therapeutic approaches to the alphaherpesvirus infections

Valproic Acid and Its Amidic Derivatives as New Antivirals against Alphaherpesviruses

Herpes simplex viruses (HSVs) are neurotropic viruses with broad host range whose infections cause considerable health problems in both animals and humans. In fact, 67% of the global population under the age of 50 are infected with HSV-1 and 13% have clinically recurrent HSV-2 infections. The most prescribed antiherpetics are nucleoside analogues such as acyclovir, but the emergence of mutants resistant to these drugs and the lack of available vaccines against human HSVs has led to an imminent need for new antivirals. Valproic acid (VPA) is a branched short-chain fatty acid clinically used as a broad-spectrum antiepileptic drug in the treatment of neurological disorders, which has shown promising antiviral activity against some herpesviruses. Moreover, its amidic derivatives valpromide and valnoctamide also share this antiherpetic activity. This review summarizes the current research on the use of VPA and its amidic derivatives as alternatives to traditional antiherpetics in the fight against HSV infections.

Anti-HSV-2 activity of Terminalia chebula Retz extract and its constituents, chebulagic and chebulinic acids

Background

Development of new and effective therapeutics for sexually transmitted herpes simplex virus-2 (HSV-2) infection is important from public health perspective. With an aim to identify natural products from medicinal plants, in the present study, the potential of Terminalia chebula Retz was investigated for its activity against HSV-2.

Methods

Fruits of Terminalia chebula Retz were used to prepare 50% ethanolic extract. In addition, chebulagic acid and chebulinic acid both purified from T. chebula were also used. The extract as well as purified compounds were first used to determine their in vitro cytotoxicity on Vero cells by MTT assay. T. chebula extract, chebulagic acid, chebulinic acid along with acyclovir were subsequently assessed for direct anti-viral activity, and their ability to inhibit attachment and penetration of HSV-2 to the Vero cells. In addition, their anti-HSV-2 activity was also determined by in vitro post-infection plaque reduction assay.

Results

Cytotoxicity assay using Vero cells revealed CC₅₀ = 409.71 ± 47.70 μg/ml for the extract whereas chebulagic acid and chebulinic acid showed more than 95% cell viability up to 200 μg/ml. The extract from T. chebula (IC₅₀ = 0.01 ± 0.0002 μg/ml), chebulagic (IC₅₀ = 1.41 ± 0.51 μg/ml) and chebulinic acids (IC₅₀ = 0.06 ± 0.002 μg/ml) showed dose dependent potent in vitro direct anti-viral activity against HSV-2. These also effectively prevented the attachment as well as penetration of the HSV-2 to Vero cells. In comparison, acyclovir showed poor direct anti-viral activity and failed to significantly (p > 0.05) prevent the attachment as well as penetration of HSV-2 to Vero cells when tested upto 50 μg/ml. However, in post-infection plaque reduction assay, T. chebula extract, chebulagic and chebulinic acids showed IC₅₀ values of 50.06 ± 6.12, 31.84 ± 2.64, and 8.69 ± 2.09 μg/ml, respectively, which were much lower than acyclovir (71.80 ± 19.95 ng/ml).

Conclusions

The results presented herein suggest that T. chebula extract, chebulagic and chebulinic acids have higher direct antiviral activity against HSV-2 and efficacy to inhibit virus attachment and penetration to the host cells as compared to acyclovir. However, acyclovir is more potent to inhibit post-infection virus replication. Hence, T. chebula may be a useful candidate for developing alternative therapy for prevention of sexually transmitted HSV-2 infection.

Graphical abstract

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Antiviral activity of aspirin against RNA viruses of the respiratory tract-an in vitro study

AIM

Aspirin (acetylsalicylic acid) has been used for more than 115 years in medicine. Research exists to show that aspirin has antiviral effects in vitro, for example, by blocking influenza virus propagation via NF-κB inhibition when used at high concentrations and short-term incubation steps. The aim of this study was to confirm the antiviral activity of aspirin against influenza virus and further elucidate the activity of aspirin against other respiratory viruses.

METHODS

Tests to detect antiviral activity were performed using plaque-reduction assays. Aspirin was administered to the virus-infected cell cultures one hour after infection. Prior to these assays, the non-cytotoxic concentrations of aspirin on cells used for propagation of the respective viruses were determined.

RESULTS

Aspirin was found to be highly effective against influenza A H1N1 virus. The antiviral activity against further respiratory RNA viruses was less distinct. Respiratory syncytial virus was minimally inhibited. However, the activity of aspirin against rhinoviruses was more pronounced. Aspirin demonstrated antiviral activity against all human rhinoviruses (HRV), but the effect on members of the "major group" viruses, namely HRV14 and HRV39, was greater than on those of the "minor group," HRV1A and HRV2.

CONCLUSIONS

These data demonstrate a specific antiviral activity of aspirin against influenza A virus and HRV. The mode of action against rhinoviruses is still unknown and requires further investigation, as does the possibility of aspirin being effective in vivo to treat the common cold.

Surviving and fatal Elephant Endotheliotropic Herpesvirus-1A infections in juvenile Asian elephants - lessons learned and recommendations on anti-herpesviral therapy

Background

Elephant Endotheliotropic Herpesviruses (EEHVs) can cause acute haemorrhagic disease in young Asian elephants (Elephas maximus) and clinical EEHV infections account for the majority of their fatalities. The anti-herpesviral drug famciclovir (FCV) has been used routinely to treat viraemic at-risk elephants, but thus far without proven efficacy. This paper presents clinical and virological investigations of two EEHV-1A infected elephants treated with FCV, and discusses anti-herpesvirus therapies of viraemic elephants.

Cases presentations

Two 1.5 year old male Asian elephants at a zoological collection in the UK developed clinical EEHV-1A infections. Case 1 showed signs of myalgia for the duration of 24 hours before returning back to normal. EEHV-1A DNAemia was confirmed on the day of clinical signs and continued to be present for 18 days in total. Trunk shedding of the virus commenced 10 days after detection of initial DNAemia. Case 2 tested positive for EEHV-1A DNAemia in a routine blood screening sample in the absence of clinical signs. The blood viral load increased exponentially leading up to fatal clinical disease seven days after initial detection of DNAemia. Both calves were treated with 15 mg/kg FCV per rectum on detection of DNAemia and penciclovir, the FCV metabolite, could be detected in the blood at assumed therapeutic levels. The early indicators for clinical disease were a marked absolute and relative drop in white blood cells, particularly monocytes prior to the detection of viraemia. The most prognostic haematological parameter at later stages of the disease was the platelet count showing a continuous sharp decline throughout, followed by a dramatic drop at the time of death.

Conclusions

The EEHV-1A viraemic animals investigated here further highlight the ongoing threat posed by these viruses to juvenile Asian elephants. The findings call into question the efficacy of rectal FCV in clinical cases and direct towards the use of alternative anti-herpesvirus drugs and complementary treatments such as plasma infusions if no improvement in either viral load or the above-mentioned blood parameters are observed in the initial days of viraemia despite anti-herpesvirus therapy.

Protease Inhibitors as Ad-hoc Antibiotics

Background:

Proteases are important enzymes that can degrade proteins and are found in animals, plants, bacteria, fungi and viruses. The action of proteases can be controlled by Protease Inhibitors (PIs), chemical or proteinaceous in nature that can block the active site of protease. Since the step catalyzed by proteases may play important role in life cycle of microbes, hindering the action of proteases by PIs may act as therapeutic intervention for microbial infection.

Material and Methods:

A thorough study was performed and wide range of literature was surveyed to confirm our results of PIs showing antibacterial activity.

Results:

PIs have shown to be effective drugs against bacterial pathogens, pathogenic viruses- Human Immunodeficiency Virus (HIV), Herpes virus, Hepatitis Virus. PIs have recently been investigated for controlling protozoan parasites. Clinical value of proteases and their inhibitors has been studied inHelicobacter pyloriwhich is the etiologic agent of gastritis.

Conclusion:

This review is intended to highlight the role of PIs in the Battle against Microbial Pathogens.

In vitro Cytotoxicity and Anti-herpes Simplex Virus Type 1 Activity of Hydroethanolic Extract, Fractions, and Isolated Compounds from Stem Bark of Schinus terebinthifolius Raddi

Background:

Herpes simplex virus type 1 (HSV-1) is associated with orofacial infections and is transmitted by direct contact with infected secretions. Several efforts have been expended in the search for drugs to the treatment for herpes. Schinus terebinthifolius is used in several illnesses and among them, for the topical treatment of skin wounds, especially wounds of mucous membranes, whether infected or not.

Objective:

To evaluate the cytotoxicity and anti-HSV-1 activity of the crude hydroethanolic extract (CHE) from the stem bark of S. terebinthifolius, as well as its fractions and isolated compounds.

Materials and Methods:

The CHE was subjected to bioguided fractionation. The anti-HSV-1 activity and the cytotoxicity of the CHE, its fractions, and isolated compounds were evaluated in vitro by SRB method. A preliminar investigation of the action of CHE in the virus–host interaction was conducted by the same assay.

Results:

CHE presented flavan-3-ols and showed anti-HSV-1 activity, better than its fractions and isolated compounds. The class of substances found in CHE can bind to proteins to form unstable complexes and enveloped viruses, as HSV-1 may be vulnerable to this action. Our results suggest that the CHE interfered with virion envelope structures, masking viral receptors that are necessary for adsorption or entry into host cells.

Conclusion:

The plant investigated exhibited potential for future development treatment against HSV-1, but further tests are necessary, especially to elucidate the mechanism of action of CHE, as well as preclinical and clinical studies to confirm its safety and efficacy.

SUMMARY

Crude hydroethanolic extract (CHE) presents promising activity against herpes simplex virus type 1 (HSV 1), with selectivity index (SI) = 22.50

CHE has flavan-3-ols in its composition, such as catechin and gallocatechin

The fractions and isolated compounds obtained from CHE by bioguided fractionation are less active than the CHE against HSV-1

CHE interferes with viral entry process in the host cell and acts directly on the viral particle.

Abbreviations used: HSV: Herpes simplex virus, CHE: Crude hydroethanolic extract, WF: Water fraction, AF: Ethyl-acetate fraction, MPLC: Medium-performance liquid chromatography, TLC: Thin-layer chromatography, NMR: Nuclear magnetic resonance, ESI-MS: Electrospray ionization mass spectrometry, SRB: Sulforhodamine B, CPE: Cytopathic effect, CC50: 50% cytotoxic concentration, EC50: 50% effective concentration, PBS: Phosphate-buffered saline.

Antiviral activity of an aqueous extract derived from Aloe arborescens Mill. against a broad panel of viruses causing infections of the upper respiratory tract

BACKGROUND

A number of antiviral therapies have evolved that may be effectively administered to treat respiratory viral diseases. But these therapies are very often of limited efficacy or have severe side effects. Therefore there is great interest in developing new efficacious and safe antiviral compounds e.g. based on the identification of compounds of herbal origin.

HYPOTHESIS

Since an aqueous extract of Aloe arborescens Mill. shows antiviral activity against viruses causing infections of the upper respiratory tract in vitro we hypothesised that a product containing it such as Biaron C(®) could have an antiviral activity too.

STUDY DESIGN

Antiviral activity of Bioaron C(®), an herbal medicinal product consisting of an aqueous extract of Aloe arborescens Mill., Vitamin C, and Aronia melanocarpa Elliot. succus, added as an excipient, was tested in vitro against a broad panel of viruses involved in upper respiratory tract infections.

METHODS

These studies included human adenovirus and several RNA viruses and were performed either with plaque reduction assays or with tests for the detection of a virus-caused cytopathic effect.

RESULTS

Our studies demonstrated an impressive activity of Bioaron C(®) against members of the orthomyxoviridae - influenza A and influenza B viruses. Replication of both analysed influenza A virus strains - H1N1 and H3N2 - as well as replication of two analysed influenza B viruses - strains Yamagatal and Beiying - was significantly reduced after addition of Bioaron C(®) to the infected cell cultures. In contrast antiviral activity of Bioaron C(®) against other RNA viruses showed a heterogeneous pattern. Bioaron C(®) inhibited the replication of human rhinovirus and coxsackievirus, both viruses belonging to the family of picornaviridae and both representing non-enveloped RNA viruses. In vitro infections with respiratory syncytial virus and parainfluenza virus, both belonging to the paramyxoviridae, were only poorly blocked by the test substance. No antiviral activity of Bioaron C(®) was detected against adenovirus - a non-enveloped DNA virus.

CONCLUSIONS

These results represent the first proof of a selective antiviral activity of Bioaron C(®) against influenza viruses and create basis for further analyses of type and molecular mechanisms of the antiviral activity of this herbal medicine.

Linalool exhibits cytotoxic effects by activating antitumor immunity

According to recent studies, the Plantaginaceae, which are traditional Chinese herbal remedies, have potential for use in viral infection treatment and cancer therapy. Linalool and p-coumaric acid are two of the biologically active compounds that can be isolated from the Plantaginaceae. This study mainly focused on investigating the bioactivity of linalool as well as the bioactivity of p-coumaric acid in terms of their cytotoxic effects on cancer cells. Whether the mechanisms of such effects are generated through apoptosis and immunoregulatory activity were also investigated. By using WST-1 analysis, it was shown that linalool and p-coumaric acid have good inhibitory effects against breast, colorectal and liver cancer cells. The IC₅₀ values of linalool for those cancer cell types were 224 μM, 222 μM, and 290 μM, respectively, and the IC₅₀ values of p-coumaric acid were 693 μM, 215 μM and 87 μM, respectively. Cell cycle analysis also confirmed that linalool and p-coumaric acid can lead to apoptosis. By using flow cytometry, it was determined that treatment with linalool rather than p-coumaric acid significantly increased the sub-G1 phase and that there were more cells concentrated in the G1 phase. Furthermore, by using cytokine array analysis, we found that linalool can stimulate IFN-γ, IL-13, IL-2, IL-21, IL-21R, IL-4, IL-6sR and TNF-α secretion. This demonstrated that in addition to the bidirectional regulation capabilities found in linalool, it also induces Th1 cellular immune response in T-47D cells. These results showed that linalool holds great potential for use in cancer therapy, and we believe that it could provide an alternative way to take action against tumors.

In vitro antiviral activity of dermaseptin S(4) and derivatives from amphibian skin against herpes simplex virus type 2

Herpes simplex virus (HSV) infections have become a public health problem worldwide. The emergence of acyclovir-resistant viral strains and the failure of vaccination to prevent herpetic infections have prompted the search for new antiviral drugs. Accordingly, the present study was undertaken to synthesize chemically and evaluate Dermaseptin S(4) (S(4)), an anti-microbial peptide derived from amphibian skin, and its derivatives in terms of anti-herpetic activity. The effects of biochemical modifications on their antimicrobial potential were also investigated. The peptides were incubated together with HSV-2 on target cells under various conditions, and the antiviral effects were examined via a cell metabolic labeling method. The findings revealed that DS(4) derivatives elicited concentration-dependent antiviral activity at micromole concentrations. The biochemical modifications of S(4) allowed for the reduction of peptide cytotoxicity without altering antiviral activity. Dermaseptins were added at different times during the viral cycle to investigate the mode of antiviral action. At the highest non-cytotoxic concentrations, most of the tested derivatives were noted to exhibit high antiviral activity particularly when pre-incubated with free herpes viruses prior to infection. Among these peptides, K(4)K(20)S(4) exhibited the highest antiviral activity against HSV-2 sensitive and resistant strains. Interestingly, the antiviral activity of K(4)K(20)S(4) was effective on both acyclovir-resistant and -sensitive viruses. The findings indicate that K(4)K(20)S(4) can be considered a promising candidate for future application as a therapeutic virucidal agent for the treatment of herpes viruses.

Inactivation of microbial infectiousness by silver nanoparticles-coated condom: a new approach to inhibit HIV- and HSV-transmitted infection

Recent research suggests that today’s condoms are only 85% effective in preventing human immunodeficiency virus (HIV) and other sexually transmitted diseases. In response, there has been a push to develop more effective ways of decreasing the spread of the disease. The new nanotechnology-based condom holds the promise of being more potent than the first-generation products. The preliminary goal of this study was to develop a silver nanoparticles (Ag-NPs)-coated polyurethane condom (PUC) and to investigate its antimicrobial potential including the inactivation of HIV and herpes simplex virus (HSV) infectiousness. The Ag-NPs-coated PUC was characterized by using ultraviolet-visible spectrophotometry, Fourier transform-infrared spectroscopy, high-resolution scanning electron microscopy, and energy-dispersive analysis of X-ray spectroscopy. Nanoparticles were stable on the PUC and not washed away by water. Morphology of the PUC was retained after coating. The NP binding is due to its interaction with the nitrogen atom of the PUC. No significant toxic effects was observed when human HeLa cells, 293T and C8166 T cells were contacted to Ag-NPs-coated PUC for three hours. Interestingly, our results demonstrated that the contact of the Ag-NPs-coated PUC with HIV-1 and HSV-1/2 was able to efficiently inactivate their infectiousness. In an attempt to elucidate the antiviral action of the Ag-NPs, we have demonstrated that the anti-HIV activity was primarily mediated by the Ag-NPs, which are associated with the PUC. In addition, the data showed that both macrophage (M)-tropic and T lymphocyte (T)-tropic strains of HIV-1 were highly sensitive to the Ag-NPs-coated PUC. Furthermore, we also showed that the Ag-NPs-coated PUC was able to inhibit the growth of bacteria and fungi. These results demonstrated that the Ag-NPs-coated PUC is able to directly inactivate the microbe’s infectious ability and provides another defense line against these sexually transmitted microbial infections.

Cytotoxic, virucidal, and antiviral activity of South American plant and algae extracts

Herpes simplex virus type 1 (HSV-1) infection has a prevalence of 70% in the human population. Treatment is based on acyclovir, valacyclovir, and foscarnet, three drugs that share the same mechanism of action and of which resistant strains have been isolated from patients. In this aspect, innovative drug therapies are required. Natural products offer unlimited opportunities for the discovery of antiviral compounds. In this study, 28 extracts corresponding to 24 plant species and 4 alga species were assayed in vitro to detect antiviral activity against HSV-1. Six of the methanolic extracts inactivated viral particles by direct interaction and 14 presented antiviral activity when incubated with cells already infected. Most interesting antiviral activity values obtained are those of Limonium brasiliense, Psidium guajava, and Phyllanthus niruri, which inhibit HSV-1 replication in vitro with 50% effective concentration (EC(50)) values of 185, 118, and 60 μg/mL, respectively. For these extracts toxicity values were calculated and therefore selectivity indexes (SI) obtained. Further characterization of the bioactive components of antiviral plants will pave the way for the discovery of new compounds against HSV-1.

Antiviral activity in vitro of two preparations of the herbal medicinal product Sinupret® against viruses causing respiratory infections

Sinupret(®), a herbal medicinal product made from Gentian root, Primula flower, Elder flower, Sorrel herb, and Verbena herb is frequently used in the treatment of acute and chronic rhinosinusitis and respiratory viral infections such as common cold. To date little is known about its potential antiviral activity. Therefore experiments have been performed to measure the antiviral activity of Sinupret(®) oral drops (hereinafter referred to as "oral drops") and Sinupret(®) dry extract (hereinafter referred to as "dry extract"), in vitro against a broad panel of both enveloped and non-enveloped human pathogenic RNA and DNA viruses known to cause infections of the upper respiratory tract: influenza A, Chile 1/83 (H1N1) virus (FluA), Porcine Influenza A/California/07/2009 (H1N1) virus (pFluA), parainfluenza type 3 virus (Para 3), respiratory syncytial virus, strain Long (RSV), human rhinovirus B subtype 14 (HRV 14), coxsackievirus subtype A9 (CA9), and adenovirus C subtype 5 (Adeno 5). Concentration-dependent antiviral activity (EC(50) between 13.8 and 124.8 μg/ml) of Sinupret(®) was observed against RNA as well as DNA viruses independent of a viral envelope. Remarkable antiviral activity was shown against Adeno 5, HRV 14 and RSV in which dry extract was significantly superior to oral drops. This could be ascertained with different assays as plaque-reduction assays in plaque forming units (PFU), the analyses of a cytopathogenic effect (CPE) and with enzyme immunoassays (ELISA) to determine the amount of newly synthesised virus. Our results demonstrate that Sinupret(®) shows a broad spectrum of antiviral activity in vitro against viruses commonly known to cause respiratory infections.

Notoginsenoside ST-4 inhibits virus penetration of herpes simplex virus in vitro

Further study on steam-treated notoginseng, the roots of Panax notoginseng (Burk.) F.H. Chen (Araliaceae), which is a famous traditional Chinese medicine that is used both in raw and treated forms for a long time, led to the isolation of a new dammarane-type saponin, namely notoginsenoside ST-4. Its structure was elucidated to be 3β,12β,20(S)-tri-hydroxydammar-24-ene-3-O-β-d-xylopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 2)-β-d-glu-copyranoside, based on the detailed analyses of the 1D and 2D NMR spectral data and acidic hydrolysis. Notoginsenoside ST-4 was investigated for its antiviral activity on herpes simplex type 1 (HSV-1) and type 2 (HSV-2) in vitro. The 50% effective concentration (EC(50)) values, determined by plaque reduction assay, were 16.47 ± 0.67 and 19.44 ± 1.16 μM for HSV-1 and HSV-2, respectively, whereas the 50% cytotoxic concentration (CC(50)) determined by the XTT test on Vero cells was 510.64 ± 4.56 μM. As analyzed by attachment assay and penetration assay based on plaque reduction assay, the antiviral activity of notoginsenoside ST-4 was principally due to the penetration inhibition effects, which was confirmed by fluorescence microscopy observation that notoginsenoside ST-4 blocked the penetration of virus. Therefore, notoginsenoside ST-4 might be a promising agent for herpes simplex virus infection.

Excoecarianin, Isolated from Phyllanthus urinaria Linnea, Inhibits Herpes Simplex Virus Type 2 Infection through Inactivation of Viral Particles

Phyllanthus urinaria Linnea (Euphorbiaceae) is one of the traditional medicinal plants widely used by oriental people to treat various diseases. We have previously demonstrated that the acetone extract of P. urinaria inhibits herpes simplex virus type 2 (HSV-2) but not HSV-1 infection. In a continuing effort to clarify the antiviral mechanisms of P. urinaria, we isolated the pure compound excoecarianin from the whole plant of P. urinaria through acetone extraction, and investigated its anti-HSV-1 and HSV-2 activities. Our results indicated that excoecarianin protected Vero cells from HSV-2 but not HSV-1 infection, and its 50% inhibitory concentration (IC₅₀) was 1.4 ± 0.1 μM. The antiviral effective concentration of excoecarianin did not affect the viability or the morphology of Vero cells. Although excoecarianin inhibited HSV-2 infection, the inhibitory effect, however, was most prominent when excoecarianin was concurrently added with the virus. Pretreatment of Vero cells with excoecarianin with removal of the drug prior to infection did not yield any antiviral effects, and the same observation was made for post viral entry treatment. Subsequent studies revealed that excoecarianin inactivated HSV-2 virus particles to prevent viral infection. A synergistic antiviral effect against HSV-2 was also observed when Vero cells were treated with a combination of acyclovir (ACV) and excoecarianin. These results suggested that excoecarianin merits to be further explored as an entry inhibitor against HSV-2 and could potentially be investigated for combinatorial drug treatment with nucleoside analogues such as ACV in therapeutic management of HSV-2 infection.

Screening for antiviral activities of isolated compounds from essential oils

Essential oil of star anise as well as phenylpropanoids and sesquiterpenes, for example, trans-anethole, eugenol, β-eudesmol, farnesol, β-caryophyllene and β-caryophyllene oxide, which are present in many essential oils, were examined for their antiviral activity against herpes simplex virus type 1 (HSV-1) in vitro. Antiviral activity was analyzed by plaque reduction assays and mode of antiviral action was determined by addition of the drugs to uninfected cells, to the virus prior to infection or to herpesvirus-infected cells. Star anise oil reduced viral infectivity by >99%, phenylpropanoids inhibited HSV infectivity by about 60-80% and sesquiterpenes suppressed herpes virus infection by 40-98%. Both, star anise essential oil and all isolated compounds exhibited anti-HSV-1 activity by direct inactivation of free virus particles in viral suspension assays. All tested drugs interacted in a dose-dependent manner with herpesvirus particles, thereby inactivating viral infectivity. Star anise oil, rich in trans-anethole, revealed a high selectivity index of 160 against HSV, whereas among the isolated compounds only β-caryophyllene displayed a high selectivity index of 140. The presence of β-caryophyllene in many essential oils might contribute strongly to their antiviral ability. These results indicate that phenylpropanoids and sesquiterpenes present in essential oils contribute to their antiviral activity against HSV.

The clinical spectrum and therapeutic challenge of eczema herpeticum

We present 5 cases of eczema herpeticum in patients with severe recalcitrant atopic dermatitis to illustrate the range of possible clinical findings and supporting laboratory data that can obscure the diagnosis and complicate treatment. Major issues include: the need for aggressive laboratory evaluation (molecular diagnostics, viral cultures, skin biopsy, serology); the possibility of recurrent or chronic infection; the value of empiric antiviral therapy; the possibility of infection with thymidine-kinase resistant strains; and the importance of achieving control over the dermatitis with nonmyelosuppressive immunomodulating agents such as intravenous immunoglobulin or interferon gamma for dermatitis that requires systemic treatment.

Comparative study on the antiviral activity of selected monoterpenes derived from essential oils

Essential oils are complex natural mixtures, their main constituents, e.g. terpenes and phenylpropanoids, being responsible for their biological properties. Essential oils from eucalyptus, tea tree and thyme and their major monoterpene compounds α‐terpinene, γ‐terpinene, α‐pinene, p‐cymene, terpinen‐4‐ol, α‐terpineol, thymol, citral and 1,8‐cineole were examined for their antiviral activity against herpes simplex virus type 1 (HSV‐1) in vitro. These essential oils were able to reduce viral infectivity by >96%, the monoterpenes inhibited HSV by about >80%. The mode of antiviral action has been determined, only moderate antiviral effects were revealed by essential oils and monoterpenes when these drugs were added to host cells prior to infection or after entry of HSV into cells. However, both essential oils and monoterpenes exhibited high anti‐HSV‐1 activity by direct inactivation of free virus particles. All tested drugs interacted in a dose‐dependent manner with herpesvirus particles thereby inactivating viral infection. Among the analysed compounds, monoterpene hydrocarbons were slightly superior to monoterpene alcohols in their antiviral activity, α‐pinene and α‐terpineol revealed the highest selectivity index. However, mixtures of different monoterpenes present in natural tea tree essential oil revealed a ten‐fold higher selectivity index and a lower toxicity than its isolated single monoterpenes. Copyright © 2009 John Wiley & Sons, Ltd.

Efficacy of anise oil, dwarf-pine oil and chamomile oil against thymidine-kinase-positive and thymidine-kinase-negative herpesviruses

The effect of anise oil, dwarf-pine oil and chamomile oil against different thymidine-kinase-positive (aciclovir-sensitive) and thymidine-kinase-negative (aciclovir-resistant) herpes simplex virus type 1 (HSV-1) strains was examined. Clinical HSV-1 isolates containing frameshift mutations in the thymidine kinase (TK) gene, an insertion or a deletion, yield a non-functional thymidine kinase enzyme resulting in phenotypical resistance against aciclovir. The inhibitory activity of three different essential oils against herpes simplex virus isolates was tested in-vitro using a plaque reduction assay. All essential oils exhibited high levels of antiviral activity against aciclovir-sensitive HSV strain KOS and aciclovir-resistant clinical HSV isolates as well as aciclovir-resistant strain Angelotti. At maximum noncytotoxic concentrations of the plant oils, plaque formation was significantly reduced by 96.6–99.9%, when herpesviruses were preincubated with drugs before attachment to host cells. No significant effect on viral infectivity could be achieved by adding these compounds during the replication phase. These results indicate that anise oil, dwarf-pine oil and chamomile oil affected the virus by interrupting adsorption of herpesviruses and in a different manner than aciclovir, which is effective after attachment inside the infected cells. Thus the investigated essential oils are capable of exerting a direct effect on HSV and might be useful in the treatment of drug-resistant viruses. Chamomile oil did not reveal any irritating potential on hen's egg chorioallantoic membrane, demonstrated the highest selectivity index among the oils tested and was highly active against clinically relevant aciclovir-resistant HSV-1 strains.

Efficacy of an aqueous Pelargonium sidoides extract against herpesvirus

The compounds of an aqueous root extract of the African medicinal plant Pelargonium sidoides were analysed by LC-MS spectroscopy and the antiviral effect of this extract against herpes simplex virus was examined in cell culture. Besides predominant coumarins, simple phenolic structures as well as flavonoid and catechin derivatives were identified as major constituents in the Pelargonium extract. The inhibitory activity of this extract against herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) was tested in vitro on RC-37 cells using a plaque reduction assay and exhibited high antiviral activity against both herpesviruses in viral suspension tests. The 50% inhibitory concentration (IC(50)) of the aqueous Pelargonium sidoides extract for herpes simplex virus plaque formation was determined at 0.00006% and 0.000005% for HSV-1 and HSV-2, respectively. At maximum noncytotoxic concentrations of the extract, plaque formation was significantly reduced by more than 99.9% for HSV-1 and HSV-2 and a clear concentration-dependent antiviral activity against HSV could be demonstrated for this extract. In order to determine the mode of antiviral action, the extract was added at different times to the cells or viruses during the infection cycle. Both herpesviruses were significantly inhibited when pretreated with the plant extract or when the extract was added during the adsorption phase, whereas acyclovir demonstrated antiviral activity only intracellularly during replication of HSV. These results indicate that P. sidoides extract affected the virus before penetration into the host cell and reveals a different mode of action when compared to the classical drug acyclovir. Hence this extract is capable of exerting an antiviral effect on herpes simplex virus and might be suitable for topical therapeutic use as antiviral drug both in labial and genital herpes infection.

Inhibitory effect of essential oils against herpes simplex virus type 2

Essential oils from anise, hyssop, thyme, ginger, camomile and sandalwood were screened for their inhibitory effect against herpes simplex virus type 2 (HSV-2) in vitro on RC-37 cells using a plaque reduction assay. Genital herpes is a chronic, persistent infection spreading efficiently and silently as sexually transmitted disease through the population. Antiviral agents currently applied for the treatment of herpesvirus infections include acyclovir and its derivatives. The inhibitory concentrations (IC50) were determined at 0.016%, 0.0075%, 0.007%, 0.004%, 0.003% and 0.0015% for anise oil, hyssop oil, thyme oil, ginger oil, camomile oil and sandalwood oil, respectively. A clearly dose-dependent virucidal activity against HSV-2 could be demonstrated for all essential oils tested. In order to determine the mode of the inhibitory effect, essential oils were added at different stages during the viral infection cycle. At maximum noncytotoxic concentrations of the essential oils, plaque formation was significantly reduced by more than 90% when HSV-2 was preincubated with hyssop oil, thyme oil or ginger oil. However, no inhibitory effect could be observed when the essential oils were added to the cells prior to infection with HSV-2 or after the adsorption period. These results indicate that essential oils affected HSV-2 mainly before adsorption probably by interacting with the viral envelope. Camomile oil exhibited a high selectivity index and seems to be a promising candidate for topical therapeutic application as virucidal agents for treatment of herpes genitalis.

Mucositis in the cancer patient and immunosuppressed host

Oral mucositis is a serious complication of cancer therapy and in severely immunosuppressed patients. In immunosuppressed patients, the signs and symptoms of infection often are muted because of limited host response, and accurate diagnosis and appropriate treatment may be difficult. Prevention of mucosal breakdown, suppression of microbial colonization, control of viral reactivation, and effective management of severe xerostomia are all critical steps to reducing the overall morbidity and mortality of oromucosal infections.

Management of recurrent oral herpes simplex infections

The literature has been reviewed for evidence of the efficacy of antiviral agents in both the prophylaxis and treatment of recurrent oral herpes simplex virus (HSV) infections and discussed by a panel of experts. Emphasis was given to randomized controlled trials. Management of herpes-associated erythema multiforme and Bell palsy were also considered. The evidence suggests that 5% acyclovir (ACV) in the cream base may reduce the duration of lesions if applied early. Recurrent herpes labialis (RHL) and recurrent intraoral HSV infections can be effectively treated with systemic ACV 400 mg 3 times a day or systemic valacyclovir 500 to 1000 mg twice a day for 3 to 5 days (longer in the immunocompromised). RHL in the immunocompetent can be effectively prevented with (1) sunscreen alone (SPF 15 or above), (2) systemic ACV 400 mg 2 to 3 times a day, or (3) systemic valacyclovir 500 to 2000 mg twice a day. Valacyclovir 500 mg twice a day is also effective in suppressing erythema multiforme triggered by HSV. Further studies are needed to compare treatment efficacy between topical penciclovir, docosanol, and ACV cream for RHL.

Chemical properties, mode of action, and in vivo anti-herpes activities of a lignin-carbohydrate complex from Prunella vulgaris

The chemical nature, the mode of action, and the in vitro and in vivo anti-HSV activities of the polysaccharide from Prunella vulgaris were characterized. The polysaccharide was isolated by ethanol precipitation, dialysis, CTAB precipitation, and gel exclusion chromatography. The isolated compound (PPS-2b) was a lignin-carbohydrate complex with a molecular weight of 8500. The carbohydrate moiety was composed of glucose, galactose, mannose, galacturonic acid, rhamnose, xylose, and arabinose with glucose as the major sugar. In plaque reduction assay, PPS-2b showed activities against HSV-1 and HSV-2. The anti-HSV activity could be abolished by periodate oxidation. Mechanism studies showed that PPS-2b inactivated HSV-1 directly, blocked HSV-1 binding to Vero cells, and inhibited HSV-1 penetration into Vero cells. A similar inhibition was observed with a gC-deficient strain of HSV-1. The in vivo activities of a Prunella cream formulated with a semi-purified fraction was assessed in a HSV-1 skin lesion model in guinea pigs and a HSV-2 genital infection model in BALB/c mice. Guinea pigs that received the Prunella cream treatment showed a significant reduction (P<0.01) in skin lesions. Mice that received the Prunella cream treatment showed a significant reduction (P<0.01) in mortality. In conclusion, the anti-HSV compound from P. vulgaris is a lignin-polysaccharide complex with potent activity against HSV-1 and HSV-2. Its mode of action appears to be inhibiting viral binding and penetration into host cells.

Oral and perioral herpes simplex virus type 1 (HSV-1) infection: review of its management

Herpes simplex virus type 1 (HSV-1) gives rise to a variety of clinical disorders and is a major cause of morbidity and mortality worldwide. HSV-1 infections are common in oral and perioral area. The aim of the present report was to critically examine the published literature to evaluate the advantages and limitations of therapy of HSV-1 infection in both immunocompetent and immunocompromised patients. Systemic antiviral therapy has been widely accepted as effective for primary herpetic gingivostomatitis. Aciclovir (ACV) 5% cream seems to be the accepted standard topical therapy for herpes labialis, being both effective and well tolerated, although penciclovir 1% cream has been proposed as a potentially useful treatment. Systemic ACV may be effective in reducing the duration of symptoms of recurrent HSV-1 infection, but the optimal timing and dose of the treatment are uncertain. Aciclovir and famciclovir may be of benefit in the acute treatment of severe HSV-1 disease in immunocompromised patients. There is also evidence that prophylactic oral ACV may reduce the frequency and severity of recurrent attack of herpetic infection in immunocompromised patients, but the optimal timing and duration of treatment is uncertain and can vary in different situations.

Pharmacotherapeutic options for the management of human polyomaviruses

Polyomaviruses [BK virus (BKV), JC virus (JCV) and simian virus 40 (SV40)] have been known to be associated with diseases in humans for over thirty years. BKV-associated nephropathy and JCV-induced progressive multifocal leukoencephalopathy (PML) were for many years rare diseases occurring only in patients with underlying severe impaired immunity. Over the past decade, the use of more potent immunosuppression (IS) in transplantation, and the Acquired Immune Deficiency Syndrome (AIDS) epidemic, have coincided with a significant increase in the prevalence of these viral complications. Prophylactic and therapeutic interventions for human polyomavirus diseases are limited by our current understanding of polyomaviral pathogenesis. Clinical trials are limited by small numbers of patients affected with clinically significant diseases, lack of defined risk factors and disease definitions, no proven effective treatment and the overall significant morbidity and mortality associated with these diseases. This chapter will focus on a review of the current and future research related to therapeutic targets and interventions for polyomavirus-associated diseases.

Inhibition of Cyclooxygenase 2 Synthesis SuppressesHerpes simplexVirus Type 1 Reactivation

Recurrent herpes virus infection, in which the virus reactivates from the nervous system and causes painful lesions in peripheral tissues, is a significant clinical problem. Our recent studies showing that the amount of cyclooxygenase 2 (COX-2) in the trigeminal ganglia of heat-stressed untreated mice is higher than the amount in heat-stressed mice treated with the COX-2 inhibitor, celecoxib, have indicated that the prostaglandin synthesis pathway--and in particular COX-2--may be an intermediate in the pathway to herpes viral reactivation. To further study this process, we infected the corneas of mice using topical application to a lightly scratched epithelium and waited 30 days for Herpes simplex virus type 1 (HSV-1) latency to be established in the trigeminal ganglia. Prior to the induction of viral reactivation, the mice were treated orally with celecoxib. Treated and untreated mice were induced to undergo reactivation by immersion in 43 degrees C water for 10 min. The shedding of virus at the ocular surface was determined by culturing ocular swabs with indicator cells. The presence of infectious virus in the trigeminal ganglion was evaluated by incubating ganglion homogenates with indicator cells and observing for cytopathic effect. Celecoxib treatment significantly suppressed viral reactivation when given prophylactically by the gastrointestinal route. The numbers of corneas and ganglia containing infectious virus were significantly lower in the celecoxib-treated animals, compared to the placebo-treated mice. These experiments demonstrate that a selective COX-2 inhibitor can suppress hyperthermic stress-induced herpes viral reactivation in the nervous system. It may be possible to use COX-2 inhibitors to prevent viral reactivation in high-risk patients by drug prophylaxis.

Mechanism of action of the suppression of herpes simplex virus type 2 replication by pterocarnin A

The purpose of this study was to investigate the in vitro antiviral properties of pterocarnin A, extracted from the bark of Pterocarya stenoptera (Juylandaceae). Results showed that pterocarnin A exhibited anti-herpes simplex virus (HSV) activity. It had a low selectivity index (SI) value and only possessed some level of cell cytotoxic effect at high antiviral concentrations. Mechanism studies demonstrated that pterocarnin A inhibited herpes simplex virus type 2 (HSV-2) from attaching and penetrating into cells. It also actively suppressed HSV-2 multiplication in Vero cells even when added 12 h after infection. This observation indicated that pterocarnin A affected the late stage(s) of HSV-2 infection cycle. Pterocarnin A also significantly reduced viral infectivity at high concentrations. From these observations, it was concluded that pterocarnin A suppressed both early and late in the replication cycle of HSV-2. The various modes of action of pterocarnin A in interfering with certain steps of viral infection thus merit further investigation.

A polysaccharide fraction from medicinal herb Prunella vulgaris downregulates the expression of herpes simplex virus antigen in Vero cells

Herpes simplex viruses (HSV) are pathogenic. With the emergence of drug-resistant strains of HSV, new antiviral agents, especially those with different modes of action, are urgently needed. Prunella vulgaris L. (Labiatae), a perennial plant commonly found in China and Europe, has long been used as a folk medicine to cure ailments. In this study, a polysaccharide fraction was prepared from Prunella vulgaris (PPV), and its effects on the expressions of HSV-1 and HSV-2 antigens in their host Vero cells were investigated with flow cytometry. The HSV antigen increased time-dependently in the infected cells, and PPV reduced its expression. The effective concentrations of PPV with 50% reductions of the HSV-1 and HSV-2 antigens were 20.6 and 20.1 microg/ml, respectively. The novelty of PPV is that it also reduces the antigen expression of acyclovir-resistant strain of HSV-1. After incubations with 25-100 microg/ml of PPV the HSV antigen-positive cells were reduced by 24.8-92.6%, respectively, showing that this polysaccharide fraction has a different mode of anti-HSV action from acyclovir. Results from this study show that PPV is effective against both the HSV-1 and HSV-2 infections, and flow cytometry offers a quantitative and highly reproducible anti-HSV drug-susceptibility assay.

Characterisation of penciclovir resistant acyclovir sensitive herpes simplex virus type 2 isolated from an AIDS patient

A heterogeneous herpes simplex virus type 2 (HSV-2) population was characterised from an AIDS patient with relapsing genital ulcer. The isolate had an unusual antiviral spectrum, showing resistance to penciclovir and susceptibility to acyclovir. Two viral populations were plaque purified, one resistant and the other susceptible to both antiviral drugs. The resistant clone was deficient in thymidine kinase (TK) activity and a nucleotide substitution, thymine for cytosine, at position 153 was identified in its TK gene. This mutation resulted in an amino acid change, arginine to tryptophan, in the ATP binding site. In the deficient mutant, a loss of virulence was observed in mice.

Current and potential therapies for the treatment of herpes-virus infections

Human herpesviruses are found worldwide and are among the most frequent causes of viral infections in immunocompetent as well as in immunocompromised patients. During the past decade and a half a better understanding of the replication and disease-causing state of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella zoster virus (VZV), and human cytomegalovirus (HCMV) has been achieved due in part to the development of potent antiviral compounds that target these viruses. While some of these antiviral therapies are considered safe and efficacious (acyclovir, penciclovir), some have toxicities associated with them (ganciclovir and foscarnet). In addition, the increased and prolonged use of these compounds in the clinical setting, especially for the treatment of immunocompromised patients, has led to the emergence of viral resistance against most of these drugs. While resistance is not a serious issue for immunocompetent individuals, it is a real concern for immunocompromised patients, especially those with AIDS and the ones that have undergone organ transplantation. All the currently approved treatments target the viral DNA polymerase. It is clear that new drugs that are more efficacious than the present ones, are not toxic, and target a different viral function would be of great use especially for immunocompromised patients. Here, an overview is provided of the diseases caused by the herpesviruses as well as the replication strategy of the better studied members of this family for which treatments are available. We also discuss the various drugs that have been approved for the treatment of some herpesviruses in terms of structure, mechanism of action, and development of resistance. Finally, we present a discussion of viral targets other than the DNA polymerase, for which new antiviral compounds are being considered.

Virucidal effect of peppermint oil on the enveloped viruses herpes simplex virus type 1 and type 2 in vitro

The virucidal effect of peppermint oil, the essential oil of Mentha piperita, against herpes simplex virus was examined. The inhibitory activity against herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) was tested in vitro on RC-37 cells using a plaque reduction assay. The 50% inhibitory concentration (IC50) of peppermint oil for herpes simplex virus plaque formation was determined at 0.002% and 0.0008% for HSV-1 and HSV-2, respectively. Peppermint oil exhibited high levels of virucidal activity against HSV-1 and HSV-2 in viral suspension tests. At noncytotoxic concentrations of the oil, plaque formation was significantly reduced by 82% and 92% for HSV-1 and HSV-2, respectively. Higher concentrations of peppermint oil reduced viral titers of both herpesviruses by more than 90%. A clearly time-dependent activity could be demonstrated, after 3 h of incubation of herpes simplex virus with peppermint oil an antiviral activity of about 99% could be demonstrated. In order to determine the mode of antiviral action of the essential oil, peppermint oil was added at different times to the cells or viruses during infection. Both herpesviruses were significantly inhibited when herpes simplex virus was pretreated with the essential oil prior to adsorption. These results indicate that peppermint oil affected the virus before adsorption, but not after penetration into the host cell. Thus this essential oil is capable to exert a direct virucidal effect on HSV. Peppermint oil is also active against an acyclovir resistant strain of HSV-1 (HSV-1-ACV(res)), plaque formation was significantly reduced by 99%. Considering the lipophilic nature of the oil which enables it to penetrate the skin, peppermint oil might be suitable for topical therapeutic use as virucidal agent in recurrent herpes infection.

Use of a single monoclonal antibody to determine the susceptibilities of herpes simplex virus type 1 and type 2 clinical isolates to acyclovir

This report describes a flow cytometry drug susceptibility assay that uses a single fluorochrome-labeled monoclonal antibody to determine the acyclovir susceptibilities of herpes simplex virus (HSV) type 1 or type 2 clinical isolates. This assay yields 50% effective doses (drug concentrations that reduce the number of antigen-positive cells by 50%) for HSV clinical isolates that are equivalent to those obtained with the plaque reduction assay.

Clinical manifestations and treatment considerations of herpes simplex virus infection

Herpes simplex viruses (HSV) types 1 and 2 cause infections manifesting as dermatologic, immunologic, and neurologic disorders. Some of the most important manifestations and complications of HSV infection are considered here in a neuroanatomic context. This discussion should aid in understanding the pathogenesis and, in some cases, diagnosis and management of associated HSV-related diseases. The sensory nervous system, rather than skin and mucous membranes, is the primary target of HSV infection. With the intention of extending the benefits of acyclovir, valacyclovir is now being explored in a number of HSV-related conditions. This review extends contemporary thinking about how new antiherpetic drugs might be put to greater therapeutic use in the future.

Diagnosis and management of recurrent herpes simplex infections

BACKGROUND

Dentists are frequently asked by patients to diagnose and treat recurrent herpetic infections, which are painful and disfiguring. The author explores the diagnosis and treatment of these commonly encountered viral conditions.

OVERVIEW

Herpetic infections represent a reactivation of the herpes simplex virus, which is highly infectious to patients, their families, dentists and staff members. The diagnosis of these conditions usually is based on case-specific historical findings, the characteristic clinical appearance and the location of the lesions.

CONCLUSIONS

Dentists often treat patients with a history of recurrent herpetic infections. Currently used topical antiviral agents, when used in a timely manner, are well-absorbed and quite effective in decreasing the severity and duration of herpetic episodes.

CLINICAL IMPLICATIONS

Until the herpetic lesions are completely healed, the dental team and patient should use management strategies to prevent spread of the virus, ensure adequate nutrition and maintain appropriate oral hygiene practices.

Antiherpes simplex virus type 2 activity of casuarinin from the bark of Terminalia arjuna Linn

Casuarinin, a hydrolyzable tannin isolated from the bark of Terminalia arjuna Linn. (Combretaceae), was investigated for its antiviral activity on herpes simplex type 2 (HSV-2) in vitro. Results showed that the IC(50) of casuarinin in XTT and plaque reduction assays were 3.6+/-0.9 and 1.5+/-0.2 microM, respectively. The 50% cytotoxic concentration for cell growth (CC(50)) was 89+/-1 microM. Thus, the selectivity index (SI) (ratio of CC(50) to IC(50)) of casuarinin was 25 and 59 for XTT and plaque reduction assays, respectively. Casuarinin continued to exhibit antiviral activity even added 12 h after infection. During the attachment assay, casuarinin was shown to prevent the attachment of HSV-2 to cells. Furthermore, casuarinin also exhibited an activity in inhibiting the viral penetration. Interestingly, casuarinin was virucidal at a concentration of 25 microM, reducing viral titers up to 100,000-fold. This study concludes that casuarinin possesses anti-herpesvirus activity in inhibiting viral attachment and penetration, and also disturbing the late event(s) of infection.

Antiviral properties of prodelphinidin B-2 3'-O-gallate from green tea leaf

Prodelphinidin B-2 3-O-gallate, a proanthocyanidin gallate isolated from green tea leaf, was investigated for its anti-herpes simplex virus type 2 properties in vitro. Prodelphinidin B-2 3'-O-gallate exhibited antiviral activity with IC50 of 5.0 +/-1.0 microM and 1.6 +/-0.3 pM for XTT and plaque reduction (PRA) assays, respectively. Cytotoxicity assay had shown that prodelphinidin B-2 3'-O-gallate possessed cytotoxic effect toward Vero cell at concentration higher than its IC50. The 50% cytotoxic concentration for cell growth (CC50) was 33.3 +/- 3.7 microM. Thus, the selectivity index (SI) (ratio of IC50 to CC50) for XTT assay and PRA was 6.7 and 20.8, respectively. Prodelphinidin B-2 3'-O-gallate significantly reduced viral infectivity at concentrations 10 microM or more. Result of time-of-addition studies suggested that prodelphinidin B-2 3'-O-gallate affected the late stage of HSV-2 infection. In addition, it was also shown to inhibit the virus from attaching and penetrating into the cell. Thus, prodelphinidin B-2 3'-O-gallate was concluded to possess antiviral activity with mechanism of inhibiting viral attachment and penetration, and disturbing the late stage of viral infection.

Periodontal disease and periodontal management in patients with cancer

Periodontal infection may exacerbate during cancer therapy and may result in oral pain and infection, and systemic infection, which may cause morbidity and can lead to mortality in neutropenic cancer patients. Periodontal disease in head and neck cancer patients treated with radiation therapy may lead to acute and chronic complications. The literature was reviewed by a search of Medline of the National Library of Medicine. The search was conducted to identify publications assessing periodontal disease in cancer patients. In addition, a review of papers referenced in the retrieved papers was conducted to identify additional publications for review. Periodontal disease should be assessed and managed prior to medical treatment of cancer for those with oropharyngeal cancer, and for patients in whom neutropenia may develop during treatment. Pretreatment assessment and management, and maintenance of oral hygiene have been shown to be effective in preventing oral and systemic complications during treatment. A complete oral and periodontal examination is appropriate for all patients planned to receive head and neck radiation therapy and those to be treated with medical protocols that are anticipated to result in neutropenia. Oral and periodontal care must continue following cancer therapy, and requires that the health care provider have an understanding of the malignant disease, oral manifestations of the disease, medical management of the disease, and of the oral complications that may develop.

Current and potential therapies for the treatment of herpesvirus infections

Human herpesviruses are found worldwide and are among the most frequent causes of viral infections in immunocompetent as well as in immunocompromised patients. During the past decade and a half a better understanding of the replication and disease causing state of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), and human cytomegalovirus (HCMV) has been achieved due in part to the development of potent antiviral compounds that target these viruses. While some of these antiviral therapies are considered safe and efficacious (acyclovir, penciclovir), some have toxicities associated with them (ganciclovir and foscarnet). In addition, the increased and prolonged use of these compounds in the clinical setting, especially for the treatment of immunocompromised patients, has led to the emergence of viral resistance against most of these drugs. While resistance is not a serious issue for immunocompetent individuals, it is a real concern for immunocompromised patients, especially those with AIDS and the ones that have undergone organ transplantation. All the currently approved treatments target the viral DNA polymerase. It is clear that new drugs that are more efficacious than the present ones, are not toxic, and target a different viral function would be of great use especially for immunocompromised patients. Here, we provide an overview of the diseases caused by the herpesviruses as well as the replication strategy of the better studiedmembers of this family for which treatments are available. We also discuss the various drugs that have been approved for the treatment of some herpesviruses in terms of structure, mechanism of action, and development of resistance. Finally, we present a discussion of viral targets other than the DNA polymerase, for which new antiviral compounds are being considered.

Infection due to acyclovir resistant herpes simplex virus in patients undergoing allogeneic hematopoietic stem cell transplantation

Over an eight-month period from October 1997 to May 1998, four patients who had received bone marrow transplant (BMT) from unrelated donor presented with severe mucosal cutaneous infections involving acyclovir resistant herpes simplex virus 1 (HSV-1). The four isolates were acyclovir (ACV) resistant, three of which were also foscarnet resistant as determined by the dye uptake method. The sequencing of the thymidine kinase (TK) gene did not permit to establish a relation between mutations and resistance to ACV. Three patients were considered as clinically cured of their HSV infection by replacement of ACV or foscarnet with either valacyclovir (one case) or cidofovir (two cases) but eventually two of them died of graft vs host disease. One patient died of extensive HSV infection despite administration of cidofovir. This study emphasizes the importance of monitoring the herpes virus resistance to antiviral drugs in bone marrow transplant recipients and the usefulness of the evaluation of novel antiviral drug for treatment of infections due to strains of HSV resistant to ACV and foscarnet that occur in about 5% of immunocompromised patients.

Current and potential therapies for the treatment of herpesvirus infections

Human herpesviruses are found worldwide and are among the most frequent causes of viral infections in immunocompetent as well as in immunocompromised patients. During the past decade and a half a better understanding of the replication and disease causing state of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), and human cytomegalovirus (HCMV) has been achieved due in part to the development of potent antiviral compounds that target these viruses. While some of these antiviral therapies are considered safe and efficacious (acyclovir, penciclovir), some have toxicities associated with them (ganciclovir and foscarnet). In addition, the increased and prolonged use of these compounds in the clinical setting, especially for the treatment of immunocompromised patients, has led to the emergence of viral resistance against most of these drugs. While resistance is not a serious issue for immunocompetent individuals, it is a real concern for immunocompromised patients, especially those with AIDS and the ones that have undergone organ transplantation. All the currently approved treatments target the viral DNA polymerase. It is clear that new drugs that are more efficacious than the present ones, are not toxic, and target a different viral function would be of great use especially for immunocompromised patients. Here, we provide an overview of the diseases caused by the herpesviruses as well as the replication strategy of the better studied members of this family for which treatments are available. We also discuss the various drugs that have been approved for the treatment of some herpesviruses in terms of structure, mechanism of action, and development of resistance. Finally, we present a discussion of viral targets other than the DNA polymerase, for which new antiviral compounds are being considered.

Oral complications associated with immunosuppression and cancer therapies

The oral manifestations of oropharyngeal infection in immunocompromised patients present a particular challenge for both medical and dental professionals because clinical signs and symptoms may be minimal and accurate diagnosis and appropriate treatment may be difficult. Effective control of infection and management of oral symptoms are important and may be achieved by the judicious use of topical and systemic agents and by maintaining good oral hygiene. Prevention of mucosal breakdown, suppression of microbial colonization, control of viral reactivation, and effective management of severe xerostomia are all critical steps to reduce the overall morbidity and mortality of oromucosal infections in the severely immunocompromised patient.