Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.7 (DNA polymerase)
17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pyrophosphate analogue, foscarnet, selectively inhibits the DNA polymerase of human herpes viruses, including cytomegalovirus, and the reverse transcriptase of HIV. Viral replication is therefore prevented, but resumes when the drug is cleared from infected cells. In vitro, the combination of foscarnet and zidovudine (azidothymidine) has an additive effect against cytomegalovirus and acts synergistically against HIV. An improvement in cytomegalovirus retinitis is obtained in over 85% of affected AIDS patients during foscarnet induction therapy, but relapse usually occurs within a month of ceasing treatment. There is a similar duration of remission during maintenance therapy given for 5 days each week, but this can be extended 4- to 5-fold with daily administration of higher doses. In allograft recipients, progression of retinitis can be halted by foscarnet until immune function recovers and eradicates the virus. The incidence of acute renal failure, which is common during foscarnet therapy, may be reduced by dosage adjustment and adequate prehydration. Anaemia, phlebitis, nausea and vomiting, and disturbances in serum calcium and phosphate levels, perhaps resulting from uptake of foscarnet into bone or chelation with ionised calcium, have also been associated with administration of the drug. Cytomegalovirus retinitis is difficult to treat, with few therapeutic options available. Although treatment with foscarnet produces some severe adverse effects, with care these can be minimised, and the drug produces clinical improvement in a large proportion of patients; this is a highly encouraging finding at this stage in its development. Preliminary comparative data indicate that foscarnet and ganciclovir are similarly effective, but foscarnet may have some theoretical advantages in AIDS patients since it can be used in combination with zidovudine without potentiating myelosuppression.
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PMID:Foscarnet. A review of its antiviral activity, pharmacokinetic properties and therapeutic use in immunocompromised patients with cytomegalovirus retinitis. 170 82

Both ganciclovir, a nucleoside analogue, and foscarnet, a pyrophosphate analogue, specifically bind cytomegalovirus (CMV) DNA polymerase and inhibit CMV replication at plasma concentrations achievable with intravenous administration. The agents have similar plasma half-lives, and both are cleared solely by the kidneys. Foscarnet has a low solubility and a high degree of ionization at physiologic pH, requiring it to be administered in higher doses and larger volumes. Both drugs are administered as an initial induction regimen followed by a long-term maintenance regimen. Among patients with the acquired immune deficiency syndrome (AIDS) who have CMV retinitis, the efficacy of long-term maintenance therapy, as measured by median time to retinitis progression, appears to be similar for the two drugs. The major toxicity of ganciclovir is myelosuppression, with dose-limiting neutropenia occurring in approximately 16% and thrombocytopenia in 5% of AIDS patients. The major toxicity of foscarnet is nephrotoxicity, with dose-limiting toxicity occurring in approximately 10-23% of patients; other effects of foscarnet include hypocalcemia, which may be associated with seizure and arrhythmia. Studies in vitro indicate an additive or synergistic inhibitory effect on CMV when these two drugs are combined, suggesting that lower-dose combination regimens or higher-dose alternating regimens may result in greater efficacy with less toxicity than with either drug alone.
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PMID:Approaches to the treatment of cytomegalovirus retinitis: ganciclovir and foscarnet. 184 16

Mice inoculated intracerebrally (i.c.) with a mutant strain of HSV were found to develop cataracts 1 to 2 months after inoculation. Cataract formation was subsequently shown to follow an acute retinitis which commenced within 1 week of inoculation. The mutant had been selected for high resistance to the nucleoside analogue acyclovir and has been shown previously to be defective in the induction of thymidine kinase and also to express an altered DNA polymerase. The LD50 for mice inoculated i.c. was greater than 10(5) p.f.u. compared with approx 7 p.f.u. for the parental strain. Studies of virus replication following i.c. inoculation with a sublethal dose of the mutant revealed that only small amounts of infectious virus were produced in the brain, but during a period from 6 to 12 days after inoculation vigorous replication occurred in retinal tissue, producing very high titres of virus.
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PMID:Atypical patterns of neural infection produced in mice by drug-resistant strains of herpes simplex virus. 627 78

A unique pattern of bilateral miliary retinitis due to ocular toxoplasmosis developed in a patient in the late stages of acquired immunodeficiency syndrome. Results of serologic tests for toxoplasmosis remained negative throughout the clinical course of his ocular disease. The retinitis was unresponsive to a brief course of anti-toxoplasmosis therapy. At autopsy, the histopathologic material was consistent with toxoplasmic retinitis and the DNA polymerase chain reaction was positive for toxoplasmosis. Recognition of this pattern of retinitis is important in the appropriate treatment of immunosuppressed patients with retinitis.
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PMID:Miliary toxoplasmic retinitis in acquired immunodeficiency syndrome. 844 50

Foscarnet, Phosphonoformate, has recently approved for the treatment of HCMV retinitis in AIDS patients in Japan. It inhibits the viral DNA polymerase and effective against ganciclovir-resistant HCMV. Cidofovir, (S)-1-[3-hydroxy-2-(phosphonylmethoxy)propyl]cytosine, a new acyclic nucleotide phosphonate analogues has potent activity against HCMV retinitis in AIDS at 3-7.5 mg/kg/week, once/week with concomitant oral probenecid and saline prehydration to prevent nephrotoxicity. The highest potency and selectivity against HHV-6 and HHV-7 was demonstrated S2242 (N7-isomer of 6-deoxy-ganciclovir). Ganciclovir, foscarnet, and cidofovir also exhibited selective inhibitory activity to these viruses, although the activities were not so remarkable compared with in case of HCMV. Thymidine kinase-dependent drugs (acyclovir, brivudin) showed little, if any, activity. These results suggest a structural homology of the DNA polymerase and a lack of TK gene among these three beta-herpesviruses.
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PMID:[Recent advances in antiviral drugs--antiviral agents to HCMV, HHV-6, and HHV-7]. 946 79

Three human immunodeficiency virus-infected subjects with progressive cytomegalovirus (CMV) retinitis despite prolonged antiviral therapy had buffy coat CMV isolates that were resistant to both ganciclovir and foscarnet. Genetic analysis of the resistant isolates showed that each contained a well-known ganciclovir resistance mutation in the viral UL97 phosphotransferase sequence, as well as a mutation (Ala to Val at codon 809, V809) in conserved region III of the DNA polymerase (Pol) sequence. A segment of the Pol sequence from one of the clinical isolates was transferred to CMV laboratory strain AD169 by homologous recombination. The recombinant virus containing V809 showed 6.3-fold increased foscarnet resistance and 2.6-fold increased ganciclovir resistance. Occurrence of the V809 mutation in 3 unrelated cases suggests that it is a clinically significant viral genetic marker for foscarnet resistance and decreased susceptibility to ganciclovir.
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PMID:Mutation in region III of the DNA polymerase gene conferring foscarnet resistance in cytomegalovirus isolates from 3 subjects receiving prolonged antiviral therapy. 969 36

We describe a 46-year-old man in whom retinitis was diagnosed as his initial HIV and AIDS defining illness. A diagnosis of CMV infection was made based on the clinical appearance of the fundus and confirmed by DNA polymerase chain reaction (PCR) on his vitreous biopsy. His CD4+ T lymphocyte count at the time was 580 x 10(6)/l (16%) with a CD4:CD8 ration of 0.28. He had a splenectomy following trauma more than 20 years earlier. He responded very well to intravenous and oral ganciclovir and remains recurrence-free almost 2 years later. This case and others highlight two issues: (i) CMV retinitis in HIV positive is not confined to those with very low CD4+ T lymphocyte counts; (ii) previous splenectomy may have an impact on CD4+ cell numbers and function.
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PMID:Cytomegalovirus retinitis, human immunodeficiency virus antibody positivity and normal T helper cell numbers. 982 Oct 96

Cidofovir is the first nucleoside monophosphate analogue currently being used for the treatment of human cytomegalovirus (HCMV) retinitis in individuals with AIDS. Unfortunately, the period of therapy with the use of this compound may be limited due to the possible emergence of serious irreversible nephrotoxic effects. New drugs with improved toxicity profiles are needed. The goal of this study was to investigate the anticytomegaloviral properties and drug-induced toxicity of a novel phosphonate analogue, namely, (-)-2-(R)-dihydroxyphosphinoyl-5-(S)-(guanin-9'-yl-methyl) tetrahydrofuran (compound 1), in comparison with those of cidofovir. The inhibitory activities of both compounds on HCMV propagation in vitro were similar against the AD 169 and Towne strains, with 50% inhibitory concentrations ranging from 0.02 to 0.17 microgram/ml for cidofovir and < 0.05 to 0.09 microgram/ml for compound 1. A clinical HCMV isolate that was resistant to ganciclovir and that had a known mutation within the UL54 DNA polymerase gene and a cidofovir-resistant laboratory strain derived from strain AD 169 remained sensitive to compound 1, whereas their susceptibilities to ganciclovir and cidofovir were reduced by 33- and 10-fold, respectively. Both compound 1 and cidofovir exhibited equal potencies in an experimentally induced murine cytomegalovirus (MCMV) infection in mice, with a prevention or prolongation of mean day to death at dosages of 1.0, 3.2, and 10.0 mg/kg of body weight/day. In cytotoxicity experiments, compound 1 was found to be generally more toxic than cidofovir in cell lines Hs68, HFF, and 3T3-L1 (which are permissive for HCMV or MCMV replication) but less toxic than cidofovir in MRC-5 cells (which are permissive for HCMV replication). Drug-induced toxic side effects were noticed for both compounds in rats and guinea pigs in a 5-day repeated-dose study. In guinea pigs, a greater weight loss was noticed with cidofovir than with compound 1 at dosages of 3.0 and 10.0 mg/kg/day. An opposite effect was detected in rats, which were treated with the compounds at relatively high dosages (up to 100 mg/kg/day). Compound 1 and cidofovir were nephrotoxic in both rats and guinea pigs, with the epithelium lining the proximal convoluted tubules in the renal cortex being the primary target site. The incidence and the severity of the lesions were found to be dose dependent. The lesions observed were characterized by cytoplasm degeneration and nuclear modifications such as karyomegaly, the presence of pseudoinclusions, apoptosis, and degenerative changes. In the guinea pig model, a greater incidence and severity of lesions were observed for cidofovir than for compound 1 (P < 0.001) with a drug regimen of 10 mg/kg/day.
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PMID:Comparative study of the anti-human cytomegalovirus activities and toxicities of a tetrahydrofuran phosphonate analogue of guanosine and cidofovir. 1004 67

A patient with AIDS and cytomegalovirus (CMV) retinitis received ganciclovir and foscarnet for 20 and 5 months, respectively, with evidence of periodic disease progression. After this therapy, a CMV isolate from the patient was resistant to ganciclovir, foscarnet, and cidofovir. Sequence analysis showed a known ganciclovir resistance mutation in the viral UL97 phosphotransferase (L595F) and a new mutation in conserved region V of the DNA polymerase gene (pol) sequence (codons 981-982 deleted). The pol mutation was transferred to a laboratory CMV strain (Towne) by homologous recombination and selection with either ganciclovir or foscarnet. Recombinant viruses containing this deletion showed a 6-8-fold increased ganciclovir resistance and a 3-5-fold increased resistance to both foscarnet and cidofovir, compared with the wild-type CMV. A single mutation in region V of CMV pol can, therefore, confer multiple drug resistance in a clinical isolate.
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PMID:A deletion mutation in region V of the cytomegalovirus DNA polymerase sequence confers multidrug resistance. 1106 51

A 1-year-old male chinchilla with a 2-week history of conjunctivitis suffered subsequently from neurological signs comprising seizures, disorientation, recumbency and apathy. After 3 weeks of progressive central nervous disease the animal was killed in view of the poor prognosis. A non-suppurative meningitis and polioencephalitis with neuronal necrosis and intranuclear inclusion bodies were observed at necropsy and by light microscopy. The brain stem and cerebral cortices were most severely affected. Both eyes displayed ulcerative keratitis, uveitis, retinitis and retinal degeneration, and optical neuritis. Additionally, a purulent rhinitis with focal erosions, epithelial degeneration and intranuclear inclusion bodies was present. Ultrastructurally, herpes virus particles were detected in neurons of the brain. Immunohistochemistry with antisera specific for human herpes virus types 1 and 2 resulted in viral antigen labeling in neurons, glial cells and in neuronal processes. Viral antigen was found in the rhinencephalon, cerebral cortices, hippocampus, numerous nuclei of the brain stem, single foci in the cerebellum, and in a solitary erosive lesion of the right nasal vestibulum. Viral antigen was not detected in the eyes. The virus was isolated from the CNS, and nucleic acid sequence analysis of the glycoprotein B and the DNA polymerase revealed a sequence homology with human herpes virus type 1 of 99% and 100%, respectively. The clinical signs, the distribution of the lesions and the viral antigen suggest a primary ocular infection with subsequent spread to the CNS. Chinchillas are susceptible to human herpes virus 1 and may play a role as a temporary reservoir for human infections.
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PMID:Spontaneous human herpes virus type 1 infection in a chinchilla (Chinchilla lanigera f. dom.). 1241 Mar 90


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