Dideoxynucleoside HIV reverse transcriptase inhibitors and drug-related hepatotoxicity: a case report

This report regards the case of a 43 year-old HIV-positive woman who developed an episode of serious transaminase elevation during stavudine-including antiretroviral therapy. Diagnostic assessment ruled out hepatitis virus co-infection, alcohol abuse besides other possible causes of liver damage. No signs of lactic acidosis were present. Liver biopsy showed portal inflammatory infiltrate, spotty necrosis, vacuoles of macro- and micro-vesicular steatosis, acidophil and foamy hepatocytes degeneration with organelles clumping, poorly formed Mallory bodies and neutrophil granulocytes attraction (satellitosis). A dramatic improvement in liver function tests occurred when stavudine was discontinued and a new antiretroviral regimen with different nucleoside reverse transcriptase inhibitors was used. The importance of considering hepatotoxicity as an adverse event of HAART including stavudine, even in absence of other signs of mitochondrial toxicity should therefore be underlined. Liver biopsy may provide further important information regarding patients with severe transaminase elevation, for a better understanding of the etiology of liver damage

A Systematic Review of Side Effects of Nucleoside and Nucleotide Drugs Used for Treatment of Chronic Hepatitis B

Although nucleosides and nucleotides have a good safety record for the treatment of hepatitis B, there have been no systematic reviews on this topic. We searched Medline to include studies of the oral antiviral agents for hepatitis B and adverse events, with at least 48 weeks of follow-up from the initiation of treatment with the drug. Important toxicities include nephrotoxicity, myopathy, and resistance. It is often difficult to ascertain whether an adverse effect is from the study drug or the natural progression of the disease. Further safety data are needed for the newer agents and for all agents with regard to patients with decompensated liver disease, renal dysfunction, the elderly, children, and pregnant women

An Analysis of Enzyme Kinetics Data for Mitochondrial DNA Strand Termination by Nucleoside Reverse Transcription Inhibitors

Nucleoside analogs used in antiretroviral treatment have been associated with mitochondrial toxicity. The polymerase-γ hypothesis states that this toxicity stems from the analogs' inhibition of the mitochondrial DNA polymerase (polymerase-γ) leading to mitochondrial DNA (mtDNA) depletion. We have constructed a computational model of the interaction of polymerase-γ with activated nucleoside and nucleotide analog drugs, based on experimentally measured reaction rates and base excision rates, together with the mtDNA genome size, the human mtDNA sequence, and mitochondrial dNTP concentrations. The model predicts an approximately 1000-fold difference in the activated drug concentration required for a 50% probability of mtDNA strand termination between the activated di-deoxy analogs d4T, ddC, and ddI (activated to ddA) and the activated forms of the analogs 3TC, TDF, AZT, FTC, and ABC. These predictions are supported by experimental and clinical data showing significantly greater mtDNA depletion in cell culture and patient samples caused by the di-deoxy analog drugs. For zidovudine (AZT) we calculated a very low mtDNA replication termination probability, in contrast to its reported mitochondrial toxicity in vitro and clinically. Therefore AZT mitochondrial toxicity is likely due to a mechanism that does not involve strand termination of mtDNA replication

Development and Characterization of a Chronic Hepatitis B Murine Model With a Mutation in the START Codon of an HBV Polymerase

Chronic hepatitis B (CHB) is caused by the Hepatitis B virus (HBV) and affects millions of people worldwide. Developing an effective CHB therapy requires using in vivo screening methods, such as mouse models reflecting CHB based on hydrodynamic delivery of plasmid vectors containing a replication-competent HBV genome. However, long-term expression of HBV proteins is accompanied by production of progeny virions, thereby requiring a Biosafety Level (BSL) 3 animal facility. In the present study, we introduced a point mutation in the START codon of the HBV polymerase to develop a mouse model reflecting chronic hepatitis B infection without formation of viral progeny. We induced the mouse model by hydrodynamic injection of adeno-associated virus plasmid vector (pAAV) and minicircle plasmid (pMC) constructs into C57Bl/6 and C3H/HeN mouse strains, monitoring HBV antigens and antibodies in blood by enzyme-linked immunosorbent assay and analyzing liver expression of HBV core antigen by immunohistology. Persisting expression of viral antigens over 140 days (study endpoint) was observed only in the C3H/HeN mouse strain when using pAAV/1.2HBV-A and pMC/1.0HBV-D with pre-C and pre-S recombination sites. In addition, pAAV/1.2HBV-A in C3H/HeN sustained HBV core antigen positivity up to the study endpoint in C3H/HeN mice. Moreover, introducing the point mutation in the START codon of polymerase effectively prevented the formation of viral progeny. Our study establishes an accessible and affordable experimental paradigm for developing a robust mouse model reflecting CHB suitable for preclinical testing of anti-HBV therapeutics in a BSL2 animal facility.</jats:p

Ligand Strain and Its Conformational Complexity Is a Major Factor in the Binding of Cyclic Dinucleotides to STING Protein

STING stimulator of interferon genes is a key regulator of innate immunity that has recently been recognized as a promising drug target. STING is activated by cyclic dinucleotides CDNs which eventually leads to expression of type I interferons and other cytokines. Factors underlying the affinity of various CDN analogues are poorly understood. Herein, we correlate structural biology, isothermal calorimetry ITC and computational modeling to elucidate factors contributing to binding of six CDNs three pairs of natural ribo and fluorinated 2 amp; 8242; fluororibo 3 amp; 8242;,3 amp; 8242; CDNs. X ray structural analyses of six STING CDN complexes did not offer any explanation for the different affinities of the studied ligands. ITC showed entropy enthalpy compensation up to 25 amp; 8197;kcal amp; 8201;mol amp; 8722;1 for this set of similar ligands. The higher affinities of fluorinated analogues are explained with help of computational methods by smaller loss of entropy upon binding and by smaller strain free energ