Current and future treatment of chronic hepatitis B.

Hepatitis B virus (HBV) infection is an ongoing worldwide pandemic. In general, the mode of transmission is different according to its prevalence in different areas: mostly perinatal in highly prevalent zones and predominantly sexual and/or parenteral in low prevalence areas. The variation in presentations of chronic hepatitis B (CHB) make its management complex. Aminotransferase levels, viral load, histologic changes, age of the patient, viral mutations (e.g. hepatitis B e antigen negative) and pregnancy are all factors that impact on treatment decisions. The ideal drug that will eradicate the HBV has yet to be developed. This review focuses on the currently available medications for CHB: alpha-interferon, lamivudine, adefovir, as well as new drugs that have proven to be active against HBV in clinical trials and are closer to licensure; pegylated interferon tenofovir, entecavir, emtricitabine, telbivudine and clevudine. The antiviral properties and the advantages and disadvantages in HBeAg-positive and negative patients are discussed. Combinations of different medications currently under study were not included in this review. A suggested algorithm, developed from recent literature, may serve as a practical guide on tailoring drug selection based on viral load, aminotransferases, hepatitis B e antigen status and histological findings. Finally, practical management questions are raised.

Tyrosine is involved in protection from oxidative stress in Saccharomyces cerevisiae.

The phenotypic characterization of a Saccharomyces cerevisiae mutant unable to grow under agitated conditions is presented here. When this strain was incubated under aerobic conditions, it did not grow and the viability of the culture decreased. The loss in viability was prevented by the addition of antioxidants or chelating agents to the medium, indicating that this mutant was unable to withstand the oxidative stress generated by aerobic metabolism. This strain was complemented with plasmids from a yeast genomic library. The transformants that were obtained carried plasmids harbouring the TYR1 gene, which codes for one of the enzymes involved in tyrosine biosynthesis. A monogenic S. cerevisiae tyr1 mutant obtained from the Yeast Genetic Stock Center showed higher sensitivity to hydrogen peroxide than a TYR1 strain. This sensitivity was reverted when this strain was complemented with the TYR1 gene. Considering these results, we propose that tyrosine plays a role in the protection against oxidative stress.