Attempts at antiviral therapy of patients with active liver disease as
a consequence of chronic hepatitis B virus infection have been modera
tely successful. The molecular and cellular basis for a successful out
come in these patients is not understood and the same therapies do not
appear to benefit carriers that still have fairly normal livers and o
nly a moderate hepatitis as a result of the immune response to the inf
ection. Most carriers fall into this latter classification, at least d
uring the early years of infection, and a therapy that could be succes
sfully applied before extensive liver damage had occurred would presum
ably reduce the risk of subsequent liver damage and the progression to
primary hepatocellular carcinoma. Traditionally, it has been assumed
that the primary reason that individuals become chronically infected i
s that the cytotoxic T-cell response and/or antibody-dependent killing
of infected hepatocytes is insufficient to clear the infection. Less
attention has been focused on the role of the antibody response in the
generation of virus-neutralizing antibodies as the possible major def
iciency predisposing some individuals to become carriers. However, car
riers normally are antigenemic for HBsAg and virus, and carriers with
only antibodies to these structures in their circulation are virtually
unknown. In addition, it is usually assumed that the hepatocyte, the
major target of infection, does not spontaneously turn over and that,
in the absence of an immune response to the infected cell, hepatocellu
lar viability is unaffected. If, however, hepatocytes have a programme
d, albeit long, lifetime, then ongoing recruitment of hepatocytes into
the infected cell pool may be of major importance in the continuation
of a chronic infection. In this review, the possibility is discussed
that ongoing extracellular spread of virus infection is a requisite fo
r the maintenance of infection in the healthy carrier. The implication
s of this model for treatment of these patients are discussed and the
results of antiviral therapy in an animal model apparently lacking ant
iviral immune reactivity briefly reviewed.