Antiviral Activity of 4′-thioIDU and Thymidine Analogs against Orthopoxviruses

The search for effective therapies for orthopoxvirus infections has identified diverse classes of molecules with antiviral activity. Pyrimidine analogs, such as 5-iodo-2′-deoxyuridine (idoxuridine, IDU) were among the first compounds identified with antiviral activity against a number of orthopoxviruses and have been reported to be active both in vitro and in animal models of infection. More recently, additional analogs have been reported to have improved antiviral activity against orthopoxviruses including several derivatives of deoxyuridine with large substituents in the 5 position, as well as analogs with modifications in the deoxyribose moiety including (north)-methanocarbathymidine, and 5-iodo-4′-thio-2′-deoxyuridine (4′-thioIDU). The latter molecule has proven to have good antiviral activity against the orthopoxviruses both in vitro and in vivo and has the potential to be an effective therapy in humans

I Letter to the editor in response to the paper: Efficacy of ganciclovir in combination with zidovudine against cytomegalovirus in vitro and in vivo : Freitas, V.R., Fraser-Smith, E.B., Chiu, S., Michelson, S. and Schatzman, R.C. (1993) Antiviral Res. 21, 301-315

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31414/1/0000331.pd

II Letter to the editor in response to J. Suhnel's comment on the paper: A three-dimensional model to analyze drug-drug interactions : Prichard, M.N. and Shipman, C., Jr. (1990) Antiviral Res. 14, 181-206

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30292/1/0000694.pd

Human cytomegalovirus plasmid-based amplicon vector system for gene therapy

We have constructed and evaluated the utility of a helper-dependent virus vector system that is derived from Human Cytomegalovirus (HCMV). This vector is based on the herpes simplex virus (HSV) amplicon system and contains the HCMV orthologs of the two cis-acting functions required for replication and packaging of HSV genomes, the complex HCMV viral DNA replication origin (oriLyt), and the cleavage packaging signal (the a sequence). The HCMV amplicon vector replicated independently and was packaged into infectious virions in the presence of helper virus. This vector is capable of delivering and expressing foreign genes in infected cells including progenitor cells such as human CD34+ cells. Packaged defective viral genomes were passaged serially in fibroblasts and could be detected at passage 3; however, the copy number appeared to diminish upon serial passage. The HCMV amplicon offers an alternative vector strategy useful for gene(s) delivery to cells of the hematopoietic lineage

Human cytomegalovirus uracil DNA glycosylase associates with ppUL44 and accelerates the accumulation of viral DNA

BACKGROUND: Human cytomegalovirus UL114 encodes a uracil-DNA glycosylase homolog that is highly conserved in all characterized herpesviruses that infect mammals. Previous studies demonstrated that the deletion of this nonessential gene delays significantly the onset of viral DNA synthesis and results in a prolonged replication cycle. The gene product, pUL114, also appears to be important in late phase DNA synthesis presumably by introducing single stranded breaks. RESULTS: A series of experiments was performed to formally assign the observed phenotype to pUL114 and to characterize the function of the protein in viral replication. A cell line expressing pUL114 complemented the observed phenotype of a UL114 deletion virus in trans, confirming that the observed defects were the result of a deficiency in this gene product. Stocks of recombinant viruses without elevated levels of uracil were produced in the complementing cells; however they retained the phenotype of poor growth in normal fibroblasts suggesting that poor replication was unrelated to uracil content of input genomes. Recombinant viruses expressing epitope tagged versions of this gene demonstrated that pUL114 was expressed at early times and that it localized to viral replication compartments. This protein also coprecipitated with the DNA polymerase processivity factor, ppUL44 suggesting that these proteins associate in infected cells. This apparent interaction did not appear to require other viral proteins since ppUL44 could recruit pUL114 to the nucleus in uninfected cells. An analysis of DNA replication kinetics revealed that the initial rate of DNA synthesis and the accumulation of progeny viral genomes were significantly reduced compared to the parent virus. CONCLUSION: These data suggest that pUL114 associates with ppUL44 and that it functions as part of the viral DNA replication complex to increase the efficiency of both early and late phase viral DNA synthesis

Human cytomegalovirus UL27 is not required for viral replication in human tissue implanted in SCID mice

Inhibition of the human cytomegalovirus UL97 kinase by maribavir is thought to be responsible for the antiviral activity of this compound. Some mutations that confer resistance to maribavir map to UL97, however additional mutations that also confer resistance to the drug were mapped to UL27. These open reading frames share a low level of homology, yet the function of pUL27 remains unknown. A recombinant virus with a deletion in the UL27 open reading frame was reported previously to exhibit a slight replication deficit, but a more important function in vivo was hypothesized given its homology to the UL97 kinase. The potential for an important function in vivo was investigated by determining if these knockout viruses could replicate in human tissue implanted in SCID mice. None of the AD169 derived viruses replicated well in the implanted thymus/liver tissue, and is consistent with previous observations, although all of the viruses replicated to some degree in retinal tissue implants. Replication of the parent viruses was observed at 7 days post inoculation, whereas no replication was detected with any of the recombinant viruses with deletions in UL27. By day 14, replication was detected in two of the three knockout viruses and in all of the viruses by day 42. These data are consistent with minimal defects observed in cell culture, but are not consistent with an important role for UL27 in vivo. We conclude that UL27 is not required for viral replication in vivo

Isolation and characterization of cidofovir resistant vaccinia viruses

© 2008 Becker et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Triple Combination of Amantadine, Ribavirin, and Oseltamivir Is Highly Active and Synergistic against Drug Resistant Influenza Virus Strains In Vitro

The rapid emergence and subsequent spread of the novel 2009 Influenza A/H1N1 virus (2009 H1N1) has prompted the World Health Organization to declare the first pandemic of the 21st century, highlighting the threat of influenza to public health and healthcare systems. Widespread resistance to both classes of influenza antivirals (adamantanes and neuraminidase inhibitors) occurs in both pandemic and seasonal viruses, rendering these drugs to be of marginal utility in the treatment modality. Worldwide, virtually all 2009 H1N1 and seasonal H3N2 strains are resistant to the adamantanes (rimantadine and amantadine), and the majority of seasonal H1N1 strains are resistant to oseltamivir, the most widely prescribed neuraminidase inhibitor (NAI). To address the need for more effective therapy, we evaluated the in vitro activity of a triple combination antiviral drug (TCAD) regimen composed of drugs with different mechanisms of action against drug-resistant seasonal and 2009 H1N1 influenza viruses. Amantadine, ribavirin, and oseltamivir, alone and in combination, were tested against amantadine- and oseltamivir-resistant influenza A viruses using an in vitro infection model in MDCK cells. Our data show that the triple combination was highly synergistic against drug-resistant viruses, and the synergy of the triple combination was significantly greater than the synergy of any double combination tested (P<0.05), including the combination of two NAIs. Surprisingly, amantadine and oseltamivir contributed to the antiviral activity of the TCAD regimen against amantadine- and oseltamivir-resistant viruses, respectively, at concentrations where they had no activity as single agents, and at concentrations that were clinically achievable. Our data demonstrate that the TCAD regimen composed of amantadine, ribavirin, and oseltamivir is highly synergistic against resistant viruses, including 2009 H1N1. The TCAD regimen overcomes baseline drug resistance to both classes of approved influenza antivirals, and thus may represent a highly active antiviral therapy for seasonal and pandemic influenza