Vitamin B12 and hepatitis C: Molecular biology and human pathology

Cobalamins are stored in high concentrations in the human liver and thus ar e available to participate in the regulation of hepatotropic virus function s. We show that cyanocobalamin (vitamin B12) inhibited the H(IV internal ri bosome entry site (IRES)-dependent translation of a reporter gene in vitro in a dose-dependent manner without significantly affecting the cap-dependen t mechanism. Vitamin B12 failed to inhibit translation by IRES elements fro m encephalomyocarditis virus (EMCV) or classical swine fever virus (CSFV), We also demonstrate a relationship between the total cobalamin concentratio n in human sera and HCV viral load (a measure of viral replication in the h ost), The mean viral load was two orders of magnitude greater when the seru m cobalamin concentration was above 200 pM (P < 0.003), suggesting that the total cobalamin concentration in an HCV-infected liver is biologically sig nificant in HCV replication.