The role of hepatitis B virus surface proteins in regulating the maturation and secretion of complete and incomplete virions.

The expression of various forms of hepatitis B virus (HBV) surface proteins regulates the release of mature virion, but whether they affect the release of other incomplete viral particles, such as naked capsid, is not clear. Here, by stable overexpression of large or middle/small hepatitis B surface proteins (LHBs, M/SHBs) in HepAD38 cells, we evaluated their effects on the release of complete and incomplete viral particles. Overproduction of LHBs inhibited the release of all surface proteins, which increased the ratio of naked capsids/virions. This effect was accompanied by the elevated extracellular HBV RNA. On the other hand, overexpression of M/SHBs greatly improved the secretion of enveloped viral and subviral particles. In situ visualization of viral DNA and LHBs revealed intracellular retention of mature virions when LHBs were overexpressed. These results indicate that the molecular decision on secretion of enveloped or unenveloped viral particles is modulated by the intracellular ratio of large, middle and small surface antigens. This mechanism may be relevant in the progression and resolution of HBV-induced chronic liver disease.