Phytochemical Characterization of Olea europea Leaf Extracts and Assessment of Their Anti-Microbial and Anti-HSV-1 Activity.

Owing to the richness of bioactive compounds, Olea europea leaf extracts exhibit a range of health effects. The present research evaluated the antibacterial and antiviral effect of leaf extracts obtained from Olea europea L. var. sativa (OESA) and Olea europea var. sylvestris (OESY) from Tunisia. LC-DAD-ESI-MS analysis allowed the identification of different compounds that contributed to the observed biological properties. Both OESA and OESY were active against Gram-positive bacteria (MIC values between 7.81 and 15.61 µg/mL and between 15.61 and 31.25 µg/mL against Staphylococcus aureus ATCC 6538 for OESY and OESA, respectively). The antiviral activity against the herpes simplex type 1 (HSV-1) was assessed on Vero cells. The results of cell viability indicated that Olea europea leaf extracts were not toxic to cultured Vero cells. The half maximal cytotoxic concentration (CC50) values for OESA and OESY were 0.2 mg/mL and 0.82 mg/mL, respectively. Furthermore, both a plaque reduction assay and viral entry assay were used to demonstrate the antiviral activity. In conclusion, Olea europea leaf extracts demonstrated a bacteriostatic effect, as well as remarkable antiviral activity, which could provide an alternative treatment against resistant strains.

Natural Products-Derived Chemicals: Breaking Barriers to Novel Anti-HSV Drug Development.

Recently, the problem of viral infection, particularly the infection with herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2), has dramatically increased and caused a significant challenge to public health due to the rising problem of drug resistance. The antiherpetic drug resistance crisis has been attributed to the overuse of these medications, as well as the lack of new drug development by the pharmaceutical industry due to reduced economic inducements and challenging regulatory requirements. Therefore, the development of novel antiviral drugs against HSV infections would be a step forward in improving global combat against these infections. The incorporation of biologically active natural products into anti-HSV drug development at the clinical level has gained limited attention to date. Thus, the search for new drugs from natural products that could enter clinical practice with lessened resistance, less undesirable effects, and various mechanisms of action is greatly needed to break the barriers to novel antiherpetic drug development, which, in turn, will pave the road towards the efficient and safe treatment of HSV infections. In this review, we aim to provide an up-to-date overview of the recent advances in natural antiherpetic agents. Additionally, this paper covers a large scale of phenolic compounds, alkaloids, terpenoids, polysaccharides, peptides, and other miscellaneous compounds derived from various sources of natural origin (plants, marine organisms, microbial sources, lichen species, insects, and mushrooms) with promising activities against HSV infections; these are in vitro and in vivo studies. This work also highlights bioactive natural products that could be used as templates for the further development of anti-HSV drugs at both animal and clinical levels, along with the potential mechanisms by which these compounds induce anti-HSV properties. Future insights into the development of these molecules as safe and effective natural anti-HSV drugs are also debated.

Chemically sulfated polysaccharides from natural sources: Assessment of extraction-sulfation efficiencies, structural features and antiviral activities.

The provisioning of compound libraries with a high degree of diversity and attractive pharmacological properties is a limiting step in drug development. This study reports the production of highly bioactive sulfated polysaccharides, originally present in a nonsulfated, dormant state in natural sources, and demonstrates their antiviral activity (human cytomegalovirus EC50 values of 2.34-7.77 µg/mL) at a low degree of cytotoxicity. Furthermore, data strongly suggested the inhibition of virus entry as the main mode of antiviral action. Remarkably, the utilized oleum-DMF reagent was able to generate a range of sulfated polysaccharides from various natural sources, possessing varying saccharide compositions, degrees of sulfation (0.4-1.7) and molecular masses (38-94,000 g/mol). Typically, in a matter of minutes, this reagent not only solubilized polysaccharides but also chemically converted their hydroxyl functionality into sulfates. The most active sulfated polysaccharide (EC50 of 2.62 µg/mL) proved to be a 94,000 g/mol branched glucan with sulfates at C-6/C-3,6/C-2,3,6 positions. In conclusion, the important determinants of such compounds' antiviral activity are: (i) degree of sulfation, (ii) molecular mass and (iii) structural features. Thus, our approach offers a huge prospect for the improvement of natural source-derived libraries based on biologically active polysaccharides with diversified chemical profiles.

Assessment of antiherpetic activity of nonsulfated and sulfated polysaccharides from Azadirachta indica.

Azadirachta indica leaf is used by Indian population for the healing of various diseases including viral infection. Herein, we analyzed the antiherpetic (HSV-1) activity of two polysaccharides (P1 and P2) isolated from the leaf of A. indica and their chemically sulfated derivatives (P1S and P2S). The molecular weights of P1S and P2S are 41 and 11 kDa, respectively. Sulfate groups are located at positions C3 of the Araf and C6 of both Galp and Glcp residues of the most active polysaccharide (P1S). These compounds were not cytotoxic in HEp-2 cells, up to 1000 µg/mL. Both P1S and P2S exhibited antiviral activity when used simultaneously to HSV-1, with 50% inhibitory concentration/selectivity index, respectively, of 31.1 µg/mL/>51.4 and 80.5 µg/mL/>19.8. P1S showed better inhibitory effect (91.8%) compared to P1 (50%), P2 (71.1%) and P2S (70%) at 200 µg/mL. Synthesis of viral protein showed a dose-dependent response and the nucleic acid synthesis was inhibited up to 25 µg/mL, by P1 and P1S and up to 50 µg/mL, by P2 and P2S. The antiviral effect is probably due to the interference of polysaccharides at the early stages of HSV-1 replication, including adsorption. Further studies are under way to get insight into the mechanism of action of the substances.

Enhanced acyclovir delivery using w/o type microemulsion: preclinical assessment of antiviral activity using murine model of zosteriform cutaneous HSV-1 infection.

The present study was aimed to develop and evaluate a microemulsion-based dermal drug delivery of an antiviral agent, acyclovir. A water-in-oil microemulsion was prepared using isopropyl myristate, Tween 20, Span 20, water and dimethylsulphoxide. It was characterized for drug content, stability, globule size, pH, viscosity and ex vivo permeation through mice skin. In vivo antiviral efficacy of optimized formulation was assessed in female Balb/c mice against herpes simplex virus-I (HSV-I)-induced infection. It was observed that optimized formulation when applied 24-h post-infection could completely inhibit the development of cutaneous herpetic lesions vis-à-vis marketed cream.

Bayesian active learning for drug combinations.

The dynamics of complex diseases are governed by intricate interactions of myriad factors. Drug combinations, formed by mixing several single-drug treatments at various doses, can enhance the effectiveness of the therapy by targeting multiple contributing factors. The main challenge in designing drug combinations is the highly nonlinear interaction of the constituent drugs. Prior work focused on guided space-exploratory heuristics that require discretization of drug doses. While being more efficient than random sampling, these methods are impractical if the drug space is high dimensional or if the drug sensitivity is unknown. Furthermore, the effectiveness of the obtained combinations may decrease if the resolution of the discretization grid is not sufficiently fine. In this paper, we model the biological system response to a continuous combination of drug doses by a Gaussian process (GP). We perform closed-loop experiments that rely on the expected improvement criterion to efficiently guide the exploration process toward drug combinations with the optimal response. When computing the criterion, we marginalize out the GP hyperparameters in a fully Bayesian manner using a particle filter. Finally, we employ a hybrid Monte Carlo algorithm to rapidly explore the high-dimensional continuous search space. We demonstrate the effectiveness of our approach on a fully factorial Drosophila dataset, an antiviral drug dataset for Herpes simplex virus type 1, and simulated human Apoptosis networks. The results show that our approach significantly reduces the number of required trials compared to existing methods.

Current management and recommendations for access to antiviral therapy of herpes labialis.

Herpes labialis is a common skin infective condition, worldwide, which is primarily caused by HSV-1. Recurrent episodes of herpes labialis, also known as cold sores, can be frequent, painful, long-lasting and disfiguring for infected patients. At present, there are two types of antivirals for the treatment of herpes labialis, topical and oral, which are available over the counter or as prescription-only. The aim of antiviral therapy is to block viral replication to enable shortening the duration of symptoms and to accelerate healing of the lesions associated with herpes labialis. This review examines the evidence for the effectiveness of current topical and oral antivirals in the management of recurrent episodes of herpes labialis. In most countries, oral antivirals for herpes labialis are available as prescription-only. However, in early 2010, the oral antiviral famciclovir was reclassified from prescription-only medicine to pharmacist-controlled status in New Zealand. The benefits and risks associated with moving an antiviral therapy for herpes labialis from prescription-only to pharmacist-controlled status are reviewed here, and the implications for patients, general physicians and pharmacists are considered.

Resistance of herpes simplex viruses to nucleoside analogues: mechanisms, prevalence, and management.

Herpes simplex viruses (HSV) type 1 and type 2 are responsible for recurrent orolabial and genital infections. The standard therapy for the management of HSV infections includes acyclovir (ACV) and penciclovir (PCV) with their respective prodrugs valacyclovir and famciclovir. These compounds are phosphorylated by the viral thymidine kinase (TK) and then by cellular kinases. The triphosphate forms selectively inhibit the viral DNA polymerase (DNA pol) activity. Drug-resistant HSV isolates are frequently recovered from immunocompromised patients but rarely found in immunocompetent subjects. The gold standard phenotypic method for evaluating the susceptibility of HSV isolates to antiviral drugs is the plaque reduction assay. Plaque autoradiography allows the associated phenotype to be distinguished (TK-wild-type, TK-negative, TK-low-producer, or TK-altered viruses or mixtures of wild-type and mutant viruses). Genotypic characterization of drug-resistant isolates can reveal mutations located in the viral TK and/or in the DNA pol genes. Recombinant HSV mutants can be generated to analyze the contribution of each specific mutation with regard to the drug resistance phenotype. Most ACV-resistant mutants exhibit some reduction in their capacity to establish latency and to reactivate, as well as in their degree of neurovirulence in animal models of HSV infection. For instance, TK-negative HSV mutants establish latency with a lower efficiency than wild-type strains and reactivate poorly. DNA pol HSV mutants exhibit different degrees of attenuation of neurovirulence. The management of ACV- or PCV-resistant HSV infections includes the use of the pyrophosphate analogue foscarnet and the nucleotide analogue cidofovir. There is a need to develop new antiherpetic compounds with different mechanisms of action.

Assessment of correlation between skin target site free drug concentration and the in vivo topical antiviral efficacy in hairless mice for (E)-5-(2-bromovinyl)-2'-deoxyuridine and acyclovir formulations.

Recently, we reported that the in vivo efficacy of acyclovir (ACV) formulations was a single valued function of skin target site free drug concentration (C) irrespective of the formulation compositions. A long-term objective of this research has been to generalize the C concept using model drugs which are similar to as well as different from ACV in their mechanism of actions. (Bromovinyl)deoxyuridine (BVDU) was selected as a model drug based on the reported similarity in its mechanism of action with ACV. The relationship between the C predictions and the in vivo efficacies for some topical formulations containing different concentrations (0.05-10%) of either ACV or BVDU in 95% DMSO as a vehicle with or without 5% Azone as skin permeation enhancer was examined. Hairless mice infected cutaneously with HSV-1 were used to quantitatively estimate the in vivo topical antiviral efficacy. A finite dose of the test antiviral formulation was applied twice a day for 4 days, starting the day after virus inoculation. On the fifth day, the lesions were scored and the efficacy values were calculated. For each formulation, in vitro flux experiments were performed in an in vivo-in vitro experimental design that closely approximated the in vivo study protocol. As was previously shown, with all ACV formulations, a good correlation was found between the C predictions and the in vivo topical efficacy. With the BVDU formulations, on the other hand, this was found not to be the case. BVDU formulations with 5% Azone were generally much more effective than those without Azone at comparable C values. This finding is believed to be the first of its kind showing that skin "permeation enhancers" may enhance efficacy by more than simply increasing skin permeation rates.

Assessment trials of the therapeutic efficacy of the drug "Zovirax" in some recurrent ocular and genital herpetic infections.

In this work are reported the results of the researches performed by the authors more than a decade ago, aimed at assessing the clinical benefit of the introduction of the drug "Zovirax" in the treatment of recurrent herpetic infections with genital or ocular location. The results of the treatment carried out on a restricted group of patients were positive both in cases of genital herpes and of herpetic keratitis. The clinical benefit consisted in the reduction of the mean duration of the disease, in the shortening of the period of the infective virus elimination from the lesion, as well as in the decrease of the intensity and duration of the clinical symptomatology as a whole. With respect to these clinical parameters, the observations of the authors performed on a low number of cases are consistent with the data obtained by other authors in the framework of more extensive studies. The renewed discussion of these clinical and laboratory observations carried out by the authors during the first years after the introduction in our country of this drug in the therapeutic arsenal of herpetic infections is aimed at establishing a landmark for the comparison with more recent results of similar studies, starting from the idea of the opportunity of assessing periodically the sensitivity of herpes simplex virus strains, circulating among the autochthonous population, to the inhibitory action of some antiviral drugs. In other words, the in vitro testing of the susceptibility of these strains to the chemotherapeutic agents in current use is predictive for the efficacy degree of these drugs in the treatment of some forms of herpetic infections. This evaluation represents at the same time, undoubtedly, a useful epidemiological surveillance means of the circulation of human herpes viruses among the population. We refer especially to the risk of appearance of pharmacoresistant mutants, a risk possible under the conditions of the increased access of patients to the antiviral chemotherapeutic medication, which implicitly augments the probability of a fortuitous administration of treatments insufficient as regards the dose or the duration. In this work there are also shown the results regarding some experimental aspects related to the immune control mechanisms of the herpetic infection, which may complement the chemotherapeutic action. Under the treatment with acycloguanosine the synthesis of herpetic antigens is kept at a level sufficient for the circulating antibody synthesis induction and the HSV infected cells treated with the drug are recognized and lysed by effectors of the cell-mediated immune response of the host. Hence, it may be asserted that, in some clinical cases of recurrent herpes with frequent episodes, it is useful to perform immunostimulating treatments, able to potentiate the cell-mediated immune mechanisms possibly involved in the limitation of the herpetic infection at the peripheral level and of its spreading in the central nervous system.

Assessment of antiviral activity, efficacy, and toxicity of prostaglandin A2 in a rabbit model of herpetic keratitis.

Prostaglandin A2 (PGA2) inhibited the replication of herpes simplex virus type 1 in rabbit and human cornea stromal cells at concentrations of 1 to 5 microM while causing significant toxicity at 55 to 150 microM. Despite favorable therapeutic indices in cultured cells, PGA2 was not effective as a therapeutic agent in the treatment of herpetic keratitis in a rabbit model. The sequelae of disease appeared more severe in animals receiving PGA2 than in untreated or placebo-treated controls. The recovery of virus from tissues of latently infected rabbits was not affected by therapy. PGA2 therapy alone induced breakdown of the blood-aqueous barrier, indicating that pharmacologically active concentrations of drug were achieved in the eye. Thus, PGA2 had antiviral activity, but its proinflammatory effects appeared to be more detrimental than beneficial in the treatment of herpetic keratitis.

Parallel-compound synthesis: methodology for accelerating drug discovery.

Parallel compound synthesis enables large numbers of individual compounds to be prepared simultaneously using semiautomated techniques. This fast and efficient methodology has an important role to play in accelerating lead optimisation and hence the whole drug discovery process. The potential of this strategy to rapidly optimise chemical leads and provide structure-activity relationship (SAR) information was demonstrated in two therapeutic areas, antiviral agents (herpes simplex virus), and neurokinin-2 receptor antagonists.

Assessment of cytosine arabinoside as an antiviral agent in humans.

Cytotoxicity, minimal inhibitory concentrations of herpesviruses, and pharmacokinetic studies of cytosine arabinoside (ara-C) were done. Ara-C compared favorably with idoxuridine in in vitro studies of antiviral activity versus herpes simplex, varicella-zoster, and cytomegalovirus. However, ara-C was 10 times more toxic to tissue cultures, and concentrations in serum and urine of three patients who were given ara-C at acceptable dosages (1 mg/kg per day) were not measurable by our assay. These studies predict that ara-C is not likely to be a useful antiviral agent in humans because its therapeutic to toxic ratio approaches unity. These predictions of little clinical efficacy seem now to have been confirmed by clinical trails in humans. Pharmacokinetic studies outlined here should precede and help formulate controlled clinical trials of potential antiviral agents in humans.