The selectivity of action of an antiherpetic agent, 9-(2-hydroxyethoxymethyl) guanine. Reproduced from Proc. Natl. Acad. Sci. USA 74, 5716-5720 (1977)

Engineering of Bioinspired, Size-Controllable, Self-Degradable Cancer-Targeting DNA Nanoflowers via the Incorporation of an Artificial Sandwich Base

In this article, we used an artificial DNA base to manipulate the formation of DNA nanoflowers (NFs) to easily control their sizes and functionalities. Nanoflowers have been reported as the noncanonical self-assembly of multifunctional DNA nanostructures, assembled from long DNA building blocks generated by rolling circle replication (RCR). They could be incorporated with myriad functional moieties. However, the efficacy of these DNA NFs as potential nanocarriers delivering cargo in biomedicine is limited by the bioavailability and therapeutic efficacy of their cargo. Here we report the incorporation of metal-containing artificial analogues into DNA strands to control the size and the functions of NFs. We have engineered bioinspired, size-controllable, self-degradable cancer-targeting DNA nanoflowers (Sgc8-NFs-Fc) via the incorporation of an artificial sandwich base. More specifically, the introduction of a ferrocene base not only resulted in the size controllability of Sgc8-NFs-Fc from 1000 to 50 nm but also endowed Sgc8-NFs-Fc with self-degradability in the presence of H2O2 via Fenton's reaction. In vitro experiments confirmed that Sgc8-NFs-Fc/Dox could be selectively taken up by protein tyrosine kinase 7 (PTK7)-positive cancer cells and subsequently cleaved via Fenton's reaction, resulting in rapid release kinetics, nuclear accumulation, and enhanced cytotoxicity of their cargo. In vivo experiments further confirmed that Sgc8-NFs-Fc has good tumor-targeting ability and could significantly improve the therapeutic efficacy of doxorubicin in a xenograft tumor model. On the basis of their tunable size and on-demand drug release kinetics upon H2O2 stimulation, the Sgc8-NFs-Fc nanocarriers possess promising potential in drug delivery.

Acyclovir as an Ionic Liquid Cation or Anion Can Improve Aqueous Solubility

Six ionic liquid (IL)-forming ions (choline, tetrabutylphosphonium, tetrabutylammonium, and trimethylhexadecylammonium cations, and chloride and docusate anions) were paired with acyclovir as the counterion to form four low melting solid salts and two waxes; five of these compounds could be classified as ILs. All of the newly synthesized acyclovir ILs exhibited increased aqueous solubilities by at least 2 orders of magnitude when compared to that of neutral acyclovir. For three of the prepared compounds, the solubilities in simulated body fluids (phosphate-buffered saline, simulated gastric, and simulated intestinal fluids) were also greatly enhanced when compared to that of neutral acyclovir. Acyclovir in its anionic form was more water- or buffer-soluble than acyclovir in its cationic form, though this might be the effect of the particular ions, indicating that the solubilities can be finely tuned by proper choice of the cationic or anionic form of acyclovir and the counterion paired with it.

Effectiveness and safety of 0.15% ganciclovir in situ ophthalmic gel for herpes simplex keratitis - a multicenter, randomized, investigator-masked, parallel group study in Chinese patients

Objectives

Parallel comparison with 0.15% ganciclovir (GCV) ophthalmic gel to evaluate the effectiveness and safety of 0.15% GCV in situ ophthalmic gel for the treatment of herpes simplex keratitis (HSK).

Methods

This was a multicenter, randomized, investigator-masked, parallel group study. HSK patients were randomly divided into two groups, with the corresponding treatment of 0.15% GCV ophthalmic gel or 0.15% GCV in situ ophthalmic gel. Symptoms and signs were observed before administration, and 3 (±1), 7 (±1), 14 (±2), and 21 (±3) days after the administration. The clinical effective rate was considered as the primary outcome. The safety profile was evaluated by AEs, visual acuity, and ocular tolerance.

Results

The clinical effective rate in the per-protocol (PP) dataset for the treatment group and the control group were 95.10% and 93.00%, respectively (P = 0.5282). The noninferiority test showed significant differences (P = 0.000305, P < 0.025), indicating that the tested drug was noninferior to the control. Patients in the PP dataset of both groups experienced decreases in the total scores of clinical indicators. Ocular AEs were few but similar between the two groups. There were no significant differences between patients’ visions between the two groups before and after administration in the safety analysis set. In terms of drug tolerance, the rates of patients without transient blurred vision during all the visits in the treatment group were higher than those for the control group (P < 0.05). During the third and fourth visits, the rates of patients with eye itching were 4.08% and 1.22% in the treatment group, and 13.59% and 8.14% in the control group, respectively (P < 0.05). During the second visit, the rates of patients with eye irritation were 14.42% in the treatment group and 25.71% in the control group (P < 0.05).

Conclusion

The 0.15% GCV in situ ophthalmic gel was effective and safe for the treatment of HSK, and was not inferior to 0.15% GCV ophthalmic gel. The 0.15% GCV in situ ophthalmic gel presented superior ocular tolerance.

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.

Antiviral drug resistance: mechanisms and clinical implications

Antiviral drug resistance is an increasing concern in immunocompromised patient populations, where ongoing viral replication and prolonged drug exposure lead to the selection of resistant strains. Rapid diagnosis of resistance can be made by associating characteristic viral mutations with resistance to various drugs as determined by phenotypic assays. Management of drug resistance includes optimization of host factors and drug delivery, selection of alternative therapies based on knowledge of mechanisms of resistance, and the development of new antivirals. This article discusses drug resistance in herpesviruses and hepatitis B.

Enzymatic therapeutic index of acyclovir. Viral versus human polymerase gamma specificity

We have examined the kinetics of incorporation of acyclovir triphosphate by the herpes simplex virus-1 DNA polymerase holoenzyme (Pol-UL42) and the human mitochondrial DNA polymerase using transient kinetic methods. For each enzyme, we compared the kinetic parameters for acyclovir to those governing incorporation of dGTP. The favorable ground state dissociation constant (6 microM) and rate of polymerization (10 s(-1)) afford efficient incorporation of acyclovir triphosphate by the Pol-UL42 enzyme. A discrimination factor of approximately 50 favors dGTP over acyclovir triphosphate, mostly due to a faster maximum rate of dGTP incorporation. Once incorporated, acyclovir is removed with a half-life of approximately 1 h in the presence of a normal concentration of deoxynucleoside triphosphates, leading to a high toxicity index (16,000) toward viral replication. To assess the potential for toxicity toward the host we examined the incorporation and removal of acyclovir triphosphate by the human mitochondrial DNA polymerase. These results suggest moderate inhibition of mitochondrial DNA replication defining a toxicity index of 380. This value is much higher than the value of 1.5 determined for tenofovir, another acyclic nucleoside analog. The enzymatic therapeutic index is only 42 in favoring inhibition of the viral polymerase over polymerase gamma, whereas that for tenofovir is greater than 1,200. Mitochondrial toxicity is relatively low because acyclovir is activated only in infected cells by the promiscuous viral thymidine kinase and otherwise, mitochondrial toxicity would accumulate during long term treatment.

Resistance of Herpes Simplex Virus Infections to Nucleoside Analogues in HIV‐Infected Patients

Antiviral treatment of herpes simplex virus (HSV) infections with nucleoside analogues has been well established for >2 decades, but isolation of drug-resistant HSV from immunocompetent patients has remained infrequent (0.1%-0.7% of isolates) during this period. Even when drug-resistant HSV is isolated from an immunocompetent patient, this virus, with rare exceptions, is cleared normally without adverse clinical outcome. Although drug-resistant HSV is more commonly isolated from immunocompromised patients (4%-7% of isolates) and is more likely to be clinically significant, the prevalence of drug-resistant HSV even among these patients, has been stable over the past 2 decades. Despite this stable prevalence, disease due to drug-resistant HSV remains an important problem for many immunocompromised patients, including those with HIV infection. This article reviews the prevalence, pathogenesis, and implications of drug-resistant HSV infections in HIV-infected patients.

Monitoring of viral susceptibility: new challenges with the development of influenza NA inhibitors

With the clinical development of anti-viral agents, monitoring for the continued susceptibility of wild-type strains has become important in disease management. Various methods have been used to monitor viral susceptibility; the advantages and disadvantages of which depend on the virus, the target and the scale of the research being undertaken. The plaque-reduction assay is valuable for measuring susceptibility of most viruses but is not ideal for large-scale monitoring. Yield-reduction, measuring specific virus antigens, and dye-uptake assays, measuring virus cytopathic effects, are more suitable for high-throughput requirements, but the IC(50) value (the concentration that inhibits 50% of virus) varies with the viral inoculum. Surveillance of influenza susceptibility to rimantadine/amantadine in the clinic has predominantly used EIA-based assays, since plaquing of influenza clinical isolates is variable. With development of the influenza NA inhibitors it became apparent that current cell-based assays were unsuitable for monitoring susceptibility to this new class of drugs. Variability may result from virus spread directly from cell to cell in culture by-passing the NA function. Furthermore, mutations selected in the HA, while not apparently contributing to phenotypic resistance in vivo, may result in cell-culture based resistance, and may mask NA resistance in cell culture by modifying receptor-binding specificity. One important distinction between NA inhibitors and other antiviral enzyme inhibitors is that both target enzyme and inhibitor work extracellularly. NA assays are therefore most representative of the in vivo situation for monitoring susceptibility, supported by HA sequencing. As the clinical use of NA inhibitors escalates, a major change will be required in approaches used to monitor susceptibility of influenza isolates in virology laboratories world-wide.