To: Gladys Kist and Susan Shultz


From: Harold Varmus


Re:

Grant application for 1985 Hepatitis B Virus Meeting

A. The Challenge of Hepatitis B Viruses.

The serendipitous discovery of the viral agent of a widely recognized  form

of infectious hepatitis 5n man in the 1960's has stimulated the growth of a new
field of biomedical research, one that joins traditional approaches to infec-
tious disease with the techniques of modern molecular biology,  in an effort to
understand and control a major cause of human suffering.
estimated that well over 200 million people are currently infected with the hu-
man hepatitis B virus (HBV). In many parts of the world, virtually everyone is
infected at least transiently and the 5-20s who remain chronically infected are
at high risk of inflammatory hepatic disease and primary hepatocellular cancer;
in addition, they serve as a ready source of further infection.
world
particularly high, HBV-associated hepatic cancer is the most common form of fa-
tal cancer. Even in the United States, where infection is less common, at least
0.1% of the population is composed of chronic carriers of HBV and  life-time in-
fection rates may be as high as 10%.

It has been frequently

In parts of the

(particularly Africa and Southeast Asia) where rates of infection are

From the first identification of HBV, it has been appreciated that the

agent has many novel properties that distinguish it structurally and  functional-
ly from the known animal viruses.  Virus particles have an unusual structure and
are vastly outnumbered in serum from infected individuals by incomplete parti-
cles composed principally of viral surface antigen (sAg) without nucleic acid.
The interactions between virus and host are manifestly complex, leading some-
times to an immune response that appears to eliminate the virus and sometimes to
extraordinarily persistant infection with very high titres of virus in the
bloodstream; furthermore, the extent of pathological effect may vary from un-
detectable to profound loss of hepatic cells, hepatic cirrhosis, or liver canc-
er. From the early 1970'9, efforts to describe HBV in molecular terms have pro-
vided further examples of' its oddities: the genome is composed of a small circle
of double stranded DNA in which neither strand is closed, the virus particles
include a DNA polymerase activity, and protein is linked to one of the DNA
strands.

Despite the obvious medical importance of HBV and its intriguing biochemi-

cal features, efforts to apply traditional strategies for the study of animal
viruses to HBV have been frustrated by several problems. First, the virus has
remained refractory to efforts to propagate it in cell culture. Second, HBV is
strongly hepatotropic and highly species specific, confining studies of its
growth largely to naturally infected human subjects and experimentally infected
chimpanzees.  Third, until a few years ago, there were no known HBV-related
viruses found among experimentally-manipulable animals.

   Remarkable advances have occurred during the past few years in the study of
HBV, attributable in large part to the application of molecular cloning tech-
niques and  to the discovery of viruses closely related to HBV in a number of
animals, including the Eastern woodchuck, the California ground squirrel, and

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the domestic duck.  Growth of DNA copies of the genomes of all of these viruses
in bacteria has permitted nucleotide sequencing (revealing the extraordinary or-
ganization of viral coding domains) and some expression of viral gene products.
The genomes of the four best studied hepatitis B viruses are now known to con-
tain at least 3-4 open reading frames that overlap each other on a single strand
and may be translated from more than one-initiation codon in some frames. The
incompletely described programs for transciption and translation of hepatitis  B
virus genes indicate that a surprisingzy large amount of information is extract-
ed from relatively small genomes (ca. 3200 nucleotide pairs, the shortest of the
known animal virus genomes).
coding potential of these viruses will be required to probe interactions with
their hosts in detail, it has already been possible to use the newly available
information to design vaccines for human use, to raise antibodies for the iden-
tification of heretofore unseen viral proteins, and to gain insight into the
mechanisms of tissue tropism and host range.

Although a more complete understanding of the

The pursuit of those hepatitis B viruses native to woodchucks, ground

squirrels, and ducks has, in a few years, exposed the central features of the
hepatitis B life cycle and generated opportunities for conducting sophisticated
genetic and biochemical studies of the fascinating biological properties of
these viruses. At the heart of these new discoveries is the finding that the
hepatitis B viruses reproduce their DNA genomes through RNA intermediates, sug-
gesting that the viruses use a replicative strategy that is a permuted version
of the life cycle of retroviruses and that they encode an RNA-directed DNA po-
lymerase ("reverse transcriptase"). Efforts to pursue these predicatfons form a
substantial part of current activity in the study of hepatitis  B viruses.  These
efforts are now supported by recent evidence that molecularly cloned genomes of
hepatitis B viruses can initiate infection when introduced directly into the
livers of susceptible animals.
recombinant genomes produced by in vitro methods for their ability to grow and
produce disease in the animal, providing an important supplement to functional
tests of portions of genomes by DNA transformation of cultured cells.

Thus it is now possible to test mutant and

  Finally, molecular techniques and precedents from the study of other kinds
of tumor viruses have been used to explore the contribution made by HBV to
hepatic cancer. Many tumors and tumor cell lines have been shown to carry in-
tegrated and usually rearranged copies of HBV DNA, and it is now possible to ask
whether the viral DNA is active in the carcinogenic mechanism.

B. Rational for a regular meeting on the molecular properties of hepatitis
  B viruses.

The progress in hepatitis B research briefly outlined in the preceding sec-

tion has been accompanied by an influx of people from various fields - animal
virologists, genetic engineers, biochemists, immunologists, pathologists - who
now share interests in the molecular biology of hepatitis B viruses.
less, despite the rapid growth of the field of hepatitis B viruses, there has
been no appropriate forum for serious scientific discussion among its members.
Traditionally, hepatitis B viruses, especially HBV, have been included mainly in
medically-oriented gatherings and generally excluded from (or ignored at) meet-
ings addressed to tumor viruses or animal viruses. The only consistent forum has
been the tri-annual hepatitis meetings, sprawling events attended by many hun-
dreds of clinicians, pathologists, and blood bank experts, as well as virolo-

Neverthe-

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gists,  and not conducive to the kind of concentrated attention upon the molecu-
lar biology of hepatitis B viruses that is now called for. This state of rela-
tive disorder is reinforced by an examination of the vehicles for publication of
work in this area of research. People doing rather closely related experiments
often publish in journals that reflect their academic backgrounds (e .g. Gas-
troenterology or Hepatology for those with clinical training, versus 2.  Virolo-
gy, Cell, or Proceedings of the National Academy of Sciences for those with
backgrounds in basic science). Furthermore, the review articles about the
molecular aspects of these viruses are few and generally focussed rather narrow-
ly.
of modest size and length that is specifically addressed to advances on the
molecular level in hepatitis B research.

All of these factors support the idea that the time is ripe for a meeting

C. Composition of the meeting.

See notes from our get-together in May.

P.S. I have not supplied references. You could use as a general reference,
   Chapter 11 from Readings in Tumor Virology (CSH press). In fact,
   you might want to include a copy of that chapter's introduction,  as I
   may have suggested before.