Antiviral Chemotherapy Research Articles

IMP dehydrogenase: structure, mechanism, and inhibition.

George Weber was among the first to recognize that extensive metabolic changes must underlie the unbridled proliferation of cancer cells 1. His molecular correlation hypothesis postulated that a defined set of key “pace-maker” enzymes are stringently linked to neoplastic transformation and progression, and that inhibition of these enzymes would provide an effective strategy for chemotherapy. Weber's subsequent discovery that inosine 5′-monophosphate dehydrogenase (IMPDH) is amplified in tumors and rapidly proliferating tissues provided the foundation for drug design targeting this enzyme 2. Though yet to achieve much success in the cancer arena, IMPDH inhibitors are now widely used in immunosuppressive and antiviral chemotherapy, and IMPDH may also be a target for antimicrobial drugs. Clinical relevance aside, IMPDH is a fascinating enzyme. It traverses several conformations while catalyzing two different chemical transformations, utilizing unusual chemical strategies to promote each reaction. Monovalent cations such as K+ activate IMPDH, possibly by acting as a molecular lubricant to facilitate these conformational changes. The biology of IMPDH also displays some surprising twists. IMPDH binds nucleic acids and is associated with polyribosomes 3-6, though the physiological role of this interaction also has not yet been elucidated. Perhaps most intriguing is the discovery that mutations in IMPDH are associated with hereditary retinal disease 7-9. These mutations cluster to a subdomain that is not required for enzymatic activity, and the function of this subdomain is currently under debate. This article will review recent work on the biochemistry of IMPDH, integrating structure, function and inhibition. Earlier reviews on this topic include references 10-12. Several more focused reviews have addressed IMPDH as a drug target for immunosuppressive 13, cancer 14,15, antiviral 16 and antimicrobial chemotherapy 17, specific classes of IMPDH inhibitors 18, advances in structure and mechanism 19 and the role of IMPDH in retinal disease 20,21. The reader is also directed to a collection of papers from the 2000 meeting, Inosine monophosphate dehydrogenase: a major therapeutic target 22.

The regulation of disassembly of alphavirus cores

Alphaviruses are used as model viruses for structure determination and for analysis of virus entry. They are used also as vectors for protein expression and gene therapy. Virus particles are assembled by budding, using preformed cores and a modified cellular membrane. During entry, alphaviruses release the viral core into the cytoplasm. Cores are disassembled during virus entry and accumulate in the cytoplasm during virus multiplication. The regulation of core disassembly is the subject of this review. A working model compatible with all experimental data is formulated. This model comprises the following steps: (1) The incoming core is present in the cytoplasm in a metastable state, primed for disassembly. A core structure containing the so-called linker region of the core protein in an exposed position susceptible to proteolytic cleavage on the core surface might represent the primed state. (2) The primed core allows access of cellular proteins to the viral genome RNA, e.g. initiation factors of protein synthesis. (3) In a following step, ribosomal 60S subunits bind to the complex and lead to core disassembly with a concomitant transfer of core protein or of core protein fragments to the 28S rRNA. The linker region may be involved in this transfer. (4) During the later stages of virus multiplication, cellular components involved in step (2) and/or in step (3) are inactivated. This inactivation might involve the binding of newly synthesised core protein to 28S rRNA. (5) Unprimed cores, e.g. core particles containing the linker region in an unexposed position, are assembled during virus multiplication. Priming of cores and inactivation of host-cell factors each represent a complete mechanism of regulation of core disassembly. Future experiments will show whether or not both processes are actually used. Since alphaviruses, e.g. Chikungunya virus, Ross River virus, Semliki Forest virus, and Sindbis virus, are human pathogens, these experiments are of practical relevance, since they might identify targets for antiviral chemotherapy.

Cytomegalovirus (CMV)-Specific CD8+ T Cells Are Associated with Control of Viral Reactivation Post-Hemopoietic Stem Cell Transplantation (HSCT) Only If Shown to Be Functionally Active.

Targeted antiviral chemotherapy has greatly reduced the incidence of CMV disease post-HSCT, but adverse side effects still make CMV seropositivity a negative prognostic factor for survival. Immune protection from CMV disease depends on the adaptive immune response, and various strategies for adoptive cellular therapy for CMV have been evaluated in clinical trials to reduce the dependency on antiviral drugs. Characterizing the development of post-transplantation CMV-specific T cell responses may help identify minimum requirements for successful immunologic control of CMV reactivation. We investigated CMV-specific T cell immune reconstitution in 15 patients who all received ACT for CMV 4 weeks post-HSCT. The CMV seropositive donor-derived ACT product consisted of 1x105 CD4+ and CD8+ T cells/kg, generated through 2-week in vitro co-culture with CMV antigen-pulsed autologous dendritic cells. No graft versus host disease >grade II occurred in the study group. CMV-specific T cells were characterized at various time points before, during, and after CMV reactivation events by IFN-γ secretion assay, and/or by phenotyping with HLA CMV pp65 and/or IE-1 peptide pentamers. Three patients who remained CMV PCR negative throughout had no detectable levels of CMV-specific T cells, whereas high levels of CMV-specific T cells developed in the other 12 patients who all experienced episodes of viral reactivation. 11/12 of the patients with CMV reactivation had pre-emptive antiviral chemotherapy, 1/12 controlled CMV reactivation unaided. 3/12 patients experienced a second episode of viral reactivation, which they controlled unaided. At the time of first CMV DNA detection, 1 week before the start of pre-emptive chemotherapy, pentamer+ cells were already detectable in 3/5 patients tested, with absolute numbers ranging from 1150-4900/ml blood. Only after a further 1 to 4 more weeks did T cells secreting IFN-γ in response to in vitro restimulation with CMV peptides first appear in 5 patients tested. By the time viral DNA had become undetectable post-antiviral chemotherapy or post-immunological control of viral replication, pentamer+ cells were present in 8/8 patients, with absolute numbers of pentamer+ T cells >10000/ml in 7/8 patients, a level often quoted as ‘protective’ (median: 37530 cells/ml, range: 3200–139300/ml). CMV-specific CD8 T cells were maintained at high levels long after resolution of CMV viraemia (median: 24200/ml, range: 5100–75900). Absolute numbers of IFN-γ + T cells also reached high levels shortly before to just after the end of a CMV reactivation episode in 5/5 patients tested (CD8+IFN-γ + median: 48490/ml, range: 2150–138290), but subsequently temporarily dropped again to undetectable levels in some patients. Four patients had CMV reactivation episodes that were immunologically controlled unaided. Just prior these four reactivation events there was a total lack of CD8+ T cells functionally responsive to CMV. This was in spite of the presence CMV-specific CD8+ cells by phenotype in 3/3 patients tested, at >10000/ml in one patient. 0% of these pentamer+ cells secreted IFN-γ in response to CMV peptide in vitro. Soon after, by the time of the first CMV PCR+ result CD8+ IFN-γ + T cells were already detected in all patients tested (median: 2180 cells/ml, range: 550–48480, n=3), with up to 64% of pent+ cells secreting IFN-γ. Pent+ cells were above the 10000 threshold in 2/3 patients tested at this time point. These data show that characterizing T cells by phenotype alone does not permit conclusions about their functionality, because some patients experienced CMV reactivation events in the presence of high levels of pentamer+ cells. Viral reactivation episodes however appeared to be associated with a prior lack of CMV-specific CD8+ cells capable of IFN-γ secretion. Immunological control of reactivation, on the other hand, may be associated with the ability to make rapid CMV-induced IFN-γ responses, because only patients with self-resolving CMV infection developed CD8+IFN-γ + responses immediately at the onset of viraemia. However it is not possible to know how many of the patients who received antiviral chemotherapy would have been able to control the infection unaided.

Targeting the Open‐Flap Conformation of HIV‐1 Protease with Pyrrolidine‐Based Inhibitors

HIV protease is a well-established drug target in antiviral chemotherapy. Immense research efforts have been made to discover effective inhibitors, thus making the enzyme one of the most studied and best characterized proteins. Although the protease exhibits high flexibility, all approved drugs target virtually the same protein conformation. The development of viral cross-resistance demands the generation of inhibitors with novel scaffolds and deviating modes of binding. Herein we report the design and the short, high-yielding stereoselective synthesis of a series of chiral, symmetric pyrrolidine-based inhibitors targeting the open-flap conformation of the protease. The obtained co-crystal structure with one derivative provides a valuable starting point for further inhibitor design.

Development of a quantitative real-time TaqMan PCR assay for testing the susceptibility of feline herpesvirus-1 to antiviral compounds

Feline herpesvirus-1 (FHV-1) is considered as the most common viral infection of domestic cats worldwide. It causes a disease characterized by upper respiratory and ocular clinical signs. Several attempts are currently underway to develop antiviral chemotherapy for treating FHV-1 infections. The availability of a rapid quantitative method for detecting FHV-1 would greatly facilitate prompt therapy, and hence enhance the success of any antiviral regime. In this study, a TaqMan real-time PCR assay was established for measuring FHV-1 DNA levels in culture supernatants. This assay was shown to be highly specific, reproducible and allows quantitation over a range of 2 to 2 × 10 8 copies per reaction. The assay was then applied to measure the reduction of FHV-1 DNA levels in the presence of increasing concentrations of acyclovir (ACV), penciclovir (PCV) and cidofovir (CDV). The 50% inhibitory concentrations (IC 50s) obtained with the B927 laboratory strain of FHV-1 were 15.8 μM for ACV, 7.93 μM for CDV and 1.2 μM for PCV. The assay described here is sensitive, time-saving and does not involve prior titration of virus stocks or monitoring virus-induced cytopathic effects. Therefore, it is suitable for routine anti-FHV-1 drug susceptibility testing in veterinary clinics.

Acute Skin Eruptions That Are Positive for Herpes Simplex Virus DNA Polymerase in Patients With Stem Cell Transplantation

Patients with stem cell transplantation (SCT) develop erythematous eruptions (SCTE) that are often misdiagnosed and poorly treated. Latent herpes simplex virus (HSV) is likely to be reactivated by SCT-associated immunosuppression. Therefore, one of the differential diagnostic possibilities for SCTE is HSV-associated erythema multiforme (HAEM) in which HSV genetic fragments localize in stem cells that deliver them to the skin on differentiation. Lesional skin from patients with SCTE, HAEM, HSV, or drug-induced erythema (DIEM) was stained with antibodies to the HSV antigen DNA polymerase (Pol) and the major capsid protein, virion protein 5 (VP5). The HSV DNA polymerase Pol was expressed in 79% of patients with SCTE and 75% of those with HAEM. The protein VP5 was not expressed in these patients, indicative of the absence of virus replication. Findings in patients with DIEM were negative for both antigens, and those with HSV lesions were positive for both antigens. There is a growing problem with SCTE, related to the increasing numbers of performed SCT. The greater frequency of SCT-generated circulating stem cells in patients with hematological malignant neoplasms (who have latent HSV infection) may result in a widespread SCTE characterized by skin deposition of HSV DNA fragments, notably those expressing Pol antigen. This HAEM-like presentation should be considered in the differential diagnosis of SCTE. Prolonged high-dosage antiviral chemotherapy during and after hospitalization may be warranted.

Coronaviruses: Molecular and Cellular Biology.

‘The knowledge contained in the book demonstrates how quickly and relatively efficiently the worldwide research community can meld together into a giant collaborative effort and concentrate its resources to rapidly begin to understand and solve problems, in this case a health problem.’ Coronaviruses cause respiratory and gastrointestinal diseases in various vertebrates, including minor respiratory diseases in humans. Because of that fact, focused research on these viruses was limited to a few dedicated, but talented, research groups. However, that changed in 2003, when a new coronavirus emerged, designated as severe acute respiratory syndrome corona-like virus (SARS-CoV), which caused a life-threatening respiratory disease characterized as an acute respiratory distress syndrome with a fatality rate of almost 10%. Suddenly, the world’s researchers devoted countless hours to attempting to identify, characterize and develop

Strategies to protect the transplanted liver from hepatitis B virus infection

Strategies to protect the transplanted liver from hepatitis B virus infection

Combination of an antiviral drug and immunomodulation against hepadnaviral infection in the woodchuck model.

The essential role of multispecific immune responses for the control of hepatitis B virus (HBV) infection implies the need of multimodal therapeutic strategies for chronic HBV infection, including antiviral chemotherapy and immunomodulation. This hypothesis was tested in the woodchuck model by a combination of lamivudine pretreatment and subsequent immunizations of woodchucks chronically infected with woodchuck hepatitis virus. The immunizations were performed with DNA vaccines or antigen-antibody immune complexes (IC)/DNA vaccines. Immunizations with IC/DNA vaccines led to an anti-woodchuck hepatitis virus surface antibody response and significant reductions of viral load and antigenemia, suggesting that such a strategy may be effective against chronic HBV infection.

Splenic Embolization in Liver Transplant Recipients: Early Outcomes

Clinical improvement has been reported following splenic embolization for a wide variety of indications. Improvement following splenic embolization has been described in cirrhotic patients awaiting hepatic transplantation who are not candidates for surgical splenectomy. Occasionally, patients who have undergone hepatic transplantation have conditions that may also benefit from nonsurgical intervention with splenic embolization. Indications include persistent hypersplenism and pancytopenia precluding optimal treatment with antiviral therapy or chemotherapy, risk for persistent gastroesophageal variceal hemorrhage, and splenic artery steal syndrome attenuating hepatic arterial perfusion. Limited data is available on the outcome of splenic embolization in liver transplant recipients. We present the early outcomes of liver transplant recipients who were treated with splenic embolization. A retrospective chart review of all liver transplant recipients who underwent splenic embolization between 1997 and 2006 was performed, under minimal-risk study approval by the institutional review board. Five liver transplant recipients received splenic embolization: 3 for persistent hypersplenism, 1 for increased risk of gastroesophageal variceal hemorrhage, and 1 for splenic artery steal syndrome. The patients with hypersplenism demonstrated hematologic improvement, the patient with gastroesophageal varices did not experience any hemorrhage on follow-up, and the patient with splenic artery steal experienced resolution of the steal phenomenon. Postembolization syndrome was observed but no splenic abscess or death occurred. Mean follow-up was 20.2 months. In conclusion, splenic embolization is a safe and effective nonsurgical alternative for a variety of indications in liver transplant recipients.

Antiviral Briefs

AIDS Patient Care and STDsVol. 21, No. 9 Antiviral BriefsPublished Online:5 Oct 2007https://doi.org/10.1089/apc.2007.9970AboutSectionsPDF/EPUB ToolsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail FiguresReferencesRelatedDetailsCited byLogistic Regression Classifiers in the Analysis of HIV-1 Use of CCR5 and CXCR4 Coreceptors4 June 2019Journal of Natural Medicines, Vol. 71, No. 4Increased CXCR4 Use of HIV-1 Subtype C Identified by Population Sequencing in Patients Failing Antiretroviral Treatment Compared with Treatment-Naive Patients in Botswana Lotta Pramanik Sollerkvist, Simani Gaseitsiwe, Madisa Mine, Gaseene Sebetso, Thongbotho Mphoyakgosi, Thabo Diphoko, Max Essex, and Anneka Ehrnst2 May 2014 | AIDS Research and Human Retroviruses, Vol. 30, No. 5Determination of HIV tropism and its use in the clinical practice10 January 2014 | Expert Review of Anti-infective Therapy, Vol. 11, No. 12When and how to use maraviroc in HIV-infected patientsAIDS, Vol. 23, No. 18HIV Type-1 Latency: Targeted Induction of Proviral Reservoirs1 April 2009 | Antiviral Chemistry and Chemotherapy, Vol. 19, No. 5Design and validation of new genotypic tools for easy and reliable estimation of HIV tropism before using CCR5 antagonists5 March 2009 | Journal of Antimicrobial Chemotherapy, Vol. 63, No. 5Optimal use of maraviroc in clinical practiceAIDS, Vol. 22, No. 17Maraviroc: farmacocinética, interacciones y mecanismo de acciónEnfermedades Infecciosas y Microbiología Clínica, Vol. 26Métodos de determinación del tropismo viral: tests genotípicos y fenotípicosEnfermedades Infecciosas y Microbiología Clínica, Vol. 26A sensitive HPLC–MS–MS method for the determination of raltegravir in human plasmaJournal of Chromatography B, Vol. 867, No. 2 Volume 21Issue 9Sep 2007 InformationMary Ann Liebert, Inc.To cite this article:Antiviral Briefs.AIDS Patient Care and STDs.Sep 2007.702-705.http://doi.org/10.1089/apc.2007.9970Published in Volume: 21 Issue 9: October 5, 2007PDF download

Highlights of the 20th International Conference on Antiviral Research (ICAR)

The International Conference on Antiviral Research (ICAR) meetings cover all aspects of antiviral research into human viruses. The meeting included two major award lectures, invited plenary speakers and a minisymposium, based this year on HCV. In addition, there were many contributor presentations, both oral and poster. This report focuses on the major highlights of the contributor presentations. A full report, including summaries of all the invited speakers and the pre-conference clinical update satellite symposium, will be included in the International Society of Antiviral Research (ISAR) news to be published in Antiviral Chemistry and Chemotherapy (18.4).

John F. Enders Lecture 2006: Antivirals for Influenza

The long history of influenza drug development has both contributed practical advances in antiviral chemotherapy and improved the understanding of influenza pathogenesis and epidemiology. The role played by these antivirals continues to grow with the dual threats of seasonal and pandemic influenza. The neuraminidase inhibitors are proven effective for the chemoprophylaxis and treatment of influenza A and B, although early therapy is essential for disease mitigation. Studies of topically applied zanamivir have demonstrated the importance of viral replication in the lower respiratory tract, even in uncomplicated influenza. Antiviral resistance, especially to the M2 ion channel inhibitors, sometimes limits clinical utility. Oseltamivir-resistant variants may emerge during treatment but have not yet circulated widely and are usually less fit than wild-type virus; most retain susceptibility to zanamivir. The transmission fitness cost of these resistant variants is drug-, neuraminidase subtype-, and mutation-specific. Continued vigilance in drug resistance surveillance is imperative, as is research into the development of new agents that will provide the potential for alternative and combination antiviral therapy.

Dengue virus: viral targets and antiviral drugs

This work reviews the opportunities and scientific bases in the development of anti-dengue drugs. The timeliness of anti-dengue drug development is addressed in the context of the growing impact of dengueworldwide and existing strategies to fight the virus. The antiviral approach in therapy or prophylaxis during an epidemic as well as the impact of recent technological advances in drug-discovery and antiviral chemotherapy on the development of anti-dengue drugs are discussed. An analysis of current sources of synthetic or natural drugs is provided. Finally, we summarize the current knowledge on dengue virus proteins, which are currently considered the most viable as drug targets, as the envelop protein E and non-structural proteins NS3 and NS5 carrying protease, helicase, RNA triphosphatase, methyltransferase and RNA-dependent RNA polymerase activities. Other viral proteins proposed to be part of the replication complex and the complex itself are considered as potential targets of anti-dengue drugs. State-of-the-art methods are listed, that are expected to allow the discovery, design, and characterisation of anti-dengue drugs effective against the four serotypes.

Therapies for human cytomegalovirus

Human cytomegalovirus (HCMV) is a viral infection disseminated worldwide and ∼ 70% of the world population presents antibodies to CMV; usually the infection is asymptomatic in healthy individuals. However, the virus may be reactivated from latency if the host develops an immunodeficiency or is immunosuppressed by drugs. Congenital HCMV infection is also an important public health problem. Although in the last decade improved antiviral chemotherapy is becoming more readly available, an effective and safe monotherapy is so far not offered for the management of CMV infection. In addition, existing drugs are ineffective to treat certain strains of CMV. Attenuated and recombinant live virus vaccine approaches have been proposed, but safe use of these types of vaccines in healthy populations remains to be shown. This review emphasizes the existing scientific therapeutic approaches and patents regarding clinical antiviral treatment in HCMV since 2003.

Current non-AIDS antiviral chemotherapy

The evolution of antiviral therapy began with developments in the management of influenza and herpes simplex keratitis in the 1960s and early 1970s. However, the field exploded with the successful treatment of herpes simplex encephalitis, herpes zoster and genital herpes simplex virus infections, all occurring in the late 1970s and early 1980s. These advances have contributed to the development of therapies for HIV that have transformed the lives of infected patients in recent years. The clinical fruit of all of these research advances has been an armamentarium of drugs that can be used to successfully treat a variety of viral illnesses. In addition to HIV/AIDS, current antiviral therapy focuses primarily on herpesviruses, hepatitis viruses and influenza. Notably, considerable progress remains to be made in these areas. Moreover, a variety of additional viral diseases currently require the development of specific therapies.

Superficial Hepatic Capsular Lesions in a Systemically Ill Young Woman

Superficial Hepatic Capsular Lesions in a Systemically Ill Young Woman

Improved Outcome From Invasive Adenovirus Infection in Pediatric Patients After Hemopoietic Stem Cell Transplantation Using Intensive Clinical Surveillance and Early Intervention

Adenovirus is a common cause of morbidity and mortality after hemopoietic stem cell transplantation in children. Recently the incidence, risk factors, and outcome of such infections have been better defined using improved virologic detection methods, in particular polymerase chain reaction. We have introduced intensive virologic surveillance for adenovirus in our institution including at least weekly polymerase chain reaction testing of blood and stool samples. We report on 71 prospectively monitored transplants, including 40 from unrelated donors. In total, there were 8 cases of invasive adenovirus infection, 3 of whom died. Mortality was less than in previous studies as cases were managed with antiviral chemotherapy and reduction of immune suppression. In fatal cases, there was concurrent difficult graft versus host disease making withdrawal of immune suppression therapy impossible. We describe 2 cases of graft failure in association with adenovirus viremia and its treatment that were successfully managed with further donor cell infusion.

Studies on a Novel Minor-groove Targeting Artificial Nuclease: Synthesis and DNA Binding Behavior

Nucleases play an important role in molecular biology, for example, in DNA sequencing. Synthetic polyamide conjugates can be considered as a novel tool for the selective inhibition of gene expressions and also as potential drugs in anticancer or antiviral chemotherapy. In this article, the synthesis of a novel minor-groove targeting artificial nuclease, an oligopyrrol-containing compound, has been reported. It was found that this novel compound can bind DNA in AT-rich minor groove with high affinity and site specificity. DNA binding behavior was determined by using UV-Vis and CD. It is indicated that compound 6 can enhance the T m of DNA from 80. 4 °C to 84. 4 °C and that it possesses a high binding constant value (K b = 3. 05 × 10 4 L/mol).

Synthesis and Biological Activity of Phosphonated Nucleosides: Part 1Furanose, Carbocyclic and Heterocyclic Analogues

Phosphonated nucleosides represent a promising alternative in the improvement of the biological activity of nucleoside analogues in antiviral and anticancer chemotherapy. The basic concept, the chemistry, the different structural modifications and their effects on the antiviral potency will be discussed in this review.