Basis of HBV persistence and new treatment options.

The majority of the morbidity and mortality associated with hepatitis B virus infection is due to viral persistence and its consequences. The heterogeneity of outcomes from HBV infection suggests that both viral and host factors influence the development of chronic infection. Study of host genetic susceptibility has revealed a number of genes including MHC class II loci and cytokine receptors, which decrease the risk of persistence. On the viral side, the replication system is adapted to generate high levels of virions without stimulating the innate immune system. Secreted viral proteins (HBsAg and HBeAg) suppress innate responses through inhibition of TLR signaling, which leads to a weak adaptive immune response with an exhausted phenotype that is incapable of inducing viral elimination. However, even when the adaptive immune system begins to take effect after HBe seroconversion, the ability of the virus to mutate and evade T and B cell-mediated responses helps to sustain persistent infection. Understanding the mechanisms of persistence is important for the design of therapeutic strategies. Although there are currently no specific drugs that target the viral minichromosome (cccDNA), it is expected that in the future we will be able to use existing drugs more effectively to eliminate the infection.