Ch. 5— The Use of Animals in Research • 91 
to grow the poliovirus in human tissue culture 
(15), and an effective vaccine became available to 
the public in 1955. When the vaccine was devel- 
oped, monkey kidney tissue was essential for pro- 
duction of pure virus in great quantities, and live 
monkeys were essential for safety and effective- 
ness testing. Today, noninfectious polio vaccine 
can be produced in continuously propagating cells 
without the need for monkeys, although monkeys 
are required to test for safety. The impact of the 
polio vaccine has been dramatic: In 1952, at the 
height of one epidemic, 58,000 cases of polio 
occurred in the United States; in 1984, just 4 cases 
were reported (39). 
Hepatitis B 
Hepatitis B is the most dangerous form of hepa- 
titis, a debilitating liver disease characterized by 
fever, weakness, loss of appetite, headache, and 
muscle pain. There are nearly 1 million hepatitis 
B virus carriers in the United States today, and 
the infection is estimated to cost $1 million per 
day in this country. Worldwide, there are some 
200 million carriers, primarily in Asia and Africa. 
Up to 1 percent of those infected with hepatitis 
B die of the disease, and 5 to 10 percent become 
chronic carriers of the virus who can remain in- 
fectious indefinitely (21). Since there is no known 
treatment for hepatitis B infection, prevention is 
essential. 
Research with rhesus monkeys and chimpan- 
zees led to the development just a few years ago 
of a vaccine, derived from human plasma, against 
hepatitis B infection. In 1981, the Food and Drug 
Administration (FDA) licensed this vaccine for hu- 
man use. In 1984Trecombinant DNA technology 
wgsjjsed lo prepare a hepatitis B vaccine from 
yeast cells (the first vaccine for human use so 
produced). Prior to its trial in 37 human volun- 
teers, this yeast recombinant hepatitis B vaccine 
was administered to African green monkeys in 
order to gauge its effectiveness (52). These new 
vaccines are expected to have a worldwide im- 
pact on the disease, and they may also reduce the 
incidence of hepatocellular carcinoma, a form of 
liver cancer associated with chronic hepatitis B 
infection (40). 
Herpes 
Estimates of the number of persons afflicted 
with recurrent genital herpes virus infections 
range from 5 million to 20 million worldwide (61). 
A new antiviral drug, acyclovir, was recently li- 
censed for use against human genital herpes in- 
fections and appears to yield antiviral and clini- 
cal benefits when taken orally (48). Acyclovir was 
extensively tested in African green monkeys. The 
opportunity to run such tests arose because of 
a natural outbreak of a virus closely related to 
that causing both chickenpox and shingles (i.e., 
herpes zoster) in humans. The infected monkey 
colony at the Delta Regional Primate Research 
Center in Louisiana enabled scientists to study the 
herpes disease process and test antiviral drugs. 
In 1984, researchers reported an in vitro model 
system for studying the herpes simplex virus, 
using human fetal nerve cells as the host. This 
in vitro model is expected to enable analysis of 
the state of the herpes virus as it establishes and 
remains latent in human nerve cells (62). 
High Blood Pressure 
High blood pressure, when untreated, increases 
the risk of stroke, heart disease, and kidney fail- 
ure. In most cases, the cause or causes of high 
blood pressure remain unknown, and the condi- 
tion is a public health problem of immense pro- 
portions. Data from the early 1980s indicate that 
fully one-third of Americans use medication to 
control blood pressure. From 1971 to 1981, visits 
to physicians for diagnosis and therapy of high 
blood pressure increased by 55 percent, while 
visits for all other causes decreased by approxi- 
mately 5 percent (32). 
Mon k eys a re used to examine mechanisms of 
high blood pressure because the natural hormone 
molecules controlling blood pressure (e.g., the kid- 
ney hormone renin) are identical in humans and 
other primates. In contrast, the renin molecules 
of humans and nonprimate species are dissimi- 
lar. In addition to using monkeys to study the ef- 
fects of diet and drugs on high blood pressure, 
researchers are examining the genetic transmis- 
sion of high blood pressure. One breeding colony 
of cynomolgus monkeys exhibiting high blood 
