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Jan. 11, 1995                                       Contact: Renee Twombly
                                                    (919) 684-4148
                                                    twomb001@md.duke.edu

NEWS BACKGROUNDER:
DUKE SCIENTISTS WORK ON POSSIBLE AIDS VACCINE

      DURHAM, N.C. -- Scientists from four Duke University Medical
Center departments have started 1995 with an ambitious
resolution: they want significant progress in their goal of
developing an AIDS vaccine made from artificial pieces of the
virus that causes the disease.
      The research team is tearing the Human Immunodeficiency
Virus (HIV) down to the atomic level and building harmless mimics
that can be used as a vaccine. At the same time, the scientists
are unraveling the intricacies of human immunity to understand
how the vaccine can best protect against HIV.
      As ambitious as the project sounds, the Duke effort is seen
as so promising that the National Institutes of Health granted
the scientific team $2.2 million last year to help develop the
vaccine for national clinical trials. The first local test of the
prototype vaccine will begin this month. The Department of
Defense provided another $2 million last November. The DOD hopes
a version of the Duke vaccine can be used to protect soldiers
overseas who may be exposed to exotic strains of HIV.
      In short, the researchers, including virologists,
immunologists, structural biologists and biochemists, believe
they have a good chance to turn the tide on AIDS.
      But the team, led by Dr. Barton Haynes, is the first to say
that where HIV is concerned, progress is far from guaranteed.
Despite a worldwide, decade-long effort to solve the mystery of
HIV, no one knows how it causes disease. And over the past
several years, vaccines once viewed with hope have failed in
human tests.
      Still, the Duke vaccine remains promising, made even more so
because of knowledge gained from numerous false starts and
misconceptions in the AIDS research field, Haynes said in an
interview.
      "What we have learned is that it is time for a new
approach," said Haynes, chief of Duke's division of rheumatology,
allergy and clinical immunology. "We are trying, methodically, to
understand how the virus functions so that we can disarm it. It's
the only way to win."

                   Designing a better vaccine

      Many AIDS vaccines attempt to marshall the body's immune
defenses by mimicking a key part of the outer coating of the HIV
viral body. The theory is that the human immune system is
triggered to fight the virus by recognizing this outer shell.
      But scientists have found that many such vaccines fail in
clinical trials. Haynes and Duke virologist Thomas Palker say
there are two likely reasons for this failure.
      One reason is that many of the early vaccines were designed
using artificial pieces of a strain of HIV that grows well in the
laboratory, but which is not a "wild type" -- a variant found
most often in infected humans.
      The researchers say these early vaccines are aimed at
eliciting a response from only one part of the human immune
system, called "helper T cells."  These cells are a complex
network of cells that need to work in concert to effectively
destroy a "foreign" invader, whether a virus, a bacterium, or a
chemical. Helper T cells, which are thought to be the first
affected by HIV, set off a cascade response within the immune
system during actual HIV infection, including the production of
antibodies and killer T cells, both of which can destroy infected
cells.
      However, the failed vaccines do not elicit a response
directly from the immune system's most potent weapons -- killer T
cells -- Haynes said. He and Palker contend that a vaccine needs
to produce armies of both killer T cells and helper T cells to be
on the defensive.
      The second major problem with current vaccines is that "wild
type" HIV -- the kind most frequently transmitted sexually --
infects and hides within a separate class of immune cells known
as macrophages, which are large cells that ingest foreign
invaders. The virus replicates itself in the macrophages, and in
the process changes its structure so that the immune system can't
recognize it once it later emerges as a full-blown infection.
Until last year, scientists did not realize that the virus
changes itself so radically within the infected macrophages.
      The Duke vaccine attempts to solve these two problems. It is
a unique vaccine "cocktail" that mimics the wild type virus by
combining several synthetic imitations of parts of the outer coat
from four different "real world" variants of HIV. The Duke
scientists believe the many tiny pieces they selected to mimic
are the only parts of HIV that can trigger the immune system,
even after it has "mutated" inside macrophages.
      "Some molecules of the AIDS virus work to turn off the
immune system, so our strategy is to delete those sequences and
hook together the most potent stimulators of HIV immunity,"
Palker said.
      To this single chain of immune-stimulating molecules, the
scientists then attached several other protein pieces not
associated with HIV, but which are known to be powerful
stimulators of helper and killer T cells.
      The idea is that a human vaccinated with this chain of short
protein pieces, called peptides will produce a strong immune
response. The body will "remember" this immune response should
the actual virus infect the body. "Then, we hope, the initial
invading virus will be wiped out," Haynes said.
      The vaccine has worked in animal tests, and the first human
test of its effectiveness is expected to start in late January.
The trial, which will include HIV-positive patients, will check
only to see if the vaccine elicited any change in immune cell
function.
      The researchers believe that slowly but surely, laboratory
research as well as a progression of small tests in humans will
help to perfect the HIV vaccine.

                   Making the vaccine stronger

      While Haynes and Palker are refining the vaccine's content,
other scientists are shoring it up structurally.
      The chain of virus-mimicking peptides that Haynes and Palker
have built is in some ways like an overcooked spaghetti noodle.
Because the molecule is relatively small, it is very flexible.
The linkage of peptides can bend into shapes at will -- from a
rotini to a spiral, or fat egg noodle that can become like
linguini.
      But the scientists believe that only one particular shape of
molecule will attract immune cells, and it is the job of
structural biologist Leonard Spicer to figure out how the
peptides should be aligned to fit into cellular receptors. Then
he has to make it stay that way, stabilizing the tiny shape.
      "The hypothesis is that if we modify the shape of the
peptide chain, we can change its reactivity with the immune
system," said Spicer, a professor of biochemistry and radiology.
"If we are right, this will be opening the door to a whole new
way of thinking about peptides. No one has explored just how
important their shape is."
      Scientists have long known the folded shape of proteins is
critical, they haven't determined how shape determines the
protein function, Spicer said. The answer could have major
implications for the pharmaceutical industry, which is seeking to
perfect effective peptide drugs.
      To figure out what shape Duke's AIDS vaccine should have,
Spicer is dissecting Haynes' chain of peptides down to its
thousands of atoms. Spicer directs Duke's state-of-the-art $2.5
million nuclear magnetic resonance (NMR) facility that allows
scientists to "observe" the location of almost every atom of a
molecule.
      The NMR looks at how each atom interacts with others nearby
by calculating the strength of magnetic interactions between
them. It bombards the atoms with radio waves that excite them,
producing little nuclear magnets that can be detected. The
machine then assesses how intensely protons within the atoms
influence each other, based on their positions in the peptide.
      In this way, Spicer and researchers in his lab are
constructing a three-dimensional mathematical "model" of the AIDS
vaccine, based on how the atoms are aligned. When completed,
Spicer will be able to move the amino acids around to test how
the composition stabilizes its shape.
      Spicer is believed to be the first to attempt to define,
atom by atom, portions of the outer shell of HIV. He has already
found that the same part of each envelope in different strains is
structured differently, "which explains why a vaccine needs to
have elements of several different viral variations," he said.

               Tailoring a vaccine for each human

      The extraordinary task Spicer has undertaken has its match
in the job of another team member, immunologist Donna Kostyu. She
is examining how the Duke AIDS vaccine prototype can trigger the
human immune system to fight the real virus after a person is
infected. In the process she is hoping to fit a few more pieces
into the intricate puzzle of human immunity.
      Kostyu is keying in on how an individual's own unique
immunity "fingerprint" -- the molecules and proteins that
recognize what is foreign to the body and what is "self" -- may
interact with HIV, as well as an AIDS vaccine.
      She knows that some people infected with HIV progress
rapidly to full-blown AIDS. Others, infected for more than a
decade, have never developed the disease. The difference, she and
the vaccine team believe, is the combination of molecules that
trigger a shield of immunity.
      On the outer surface of each human cell are proteins whose
job is to "display" foreign molecules to circulating immune
system cells that can then destroy the invaders. These molecules,
known as human leukocyte antigens (HLA), are divided into two
different classes. HLA class I molecules display pieces of
foreign substances (such as viruses, bacteria and chemicals) that
have entered the cell. The cell "chews" up the invader and sends
a piece to the HLA receptor for display. This alerts the killer T
cells, which are capable of then annihilating cell invaders. HLA
class II molecules display bits of foreign bodies plucked from
outside cells, flagging the helper T cells, the ones that signal
a cascade of immune defenses which attack the foreign body. HIV
destroys T helper cells, leaving the host open to infection.
      Haynes and Palker believe that to be effective, a vaccine
must be recognized and presented to both class I and class II
molecules and thus trigger an assault by both killer and helper T
cells.
      The question Kostyu is trying to answer is: what effect does
the variation of HLA types among individuals have on immune
responses to the vaccine. The team believes that one reason HIV
is such an effective pathogen in the majority of infected people
is that the HLA system cannot completely recognize the virus as
foreign, and so does not fight it effectively.
      The problem is that there are thousands of different
combinations of HLA types found in people, and this variation
increases depending on ethnicity, Kostyu said. Each person
inherits three class I genes and three class II genes from each
parent. But each gene is known to exist in numerous forms or
alleles. So an individual with one set of HLA alleles may be a
good responder to the vaccine, while another person with a
different set of HLA alleles may not react to the vaccine.
      Kostyu and her laboratory associates are, therefore, testing
how different HLA molecules "bind" the Duke vaccine. So far, they
have found that it adheres to some of the molecules, but not to
others. "We can't help but be somewhat excited because we are
getting a binding pattern in the test tube," says Kostyu. The
molecules and vaccine pieces that bind are then sent back to
Spicer to see if there is a certain shape to the vaccine that is
working best in these cases.
      The ultimate goal, says Kostyu, is to find some portion of
the vaccine peptide that will fit all HLA molecules. And it will
take a lot of effort, she said. "Many HLA alleles are still being
defined. It's a brand new science and we have years of work ahead
of us."
      The research team acknowledges that only luck will quickly
produce the right combination of peptide pieces, structured in
the most effective way to trigger everyone's immune system to
mount a total defense against the virus.
      At times, their task seems like shades of the impossible.
Haynes has spent almost a decade in a sustained effort to conquer
HIV.
      But now a well-funded battle plan has been set, and the
first volleys fired. "We have a new concept of HIV biology,"
Haynes said. "Time, as always, will tell if we are right."
                              -----
      Barton Haynes, M.D., chief of the division of rheumatology,
allergy and clinical immunology, can be reached at (919) 684-
5093.
      Thomas Palker, Ph.D., associate research professor in the
division of rheumatology, allergy and clinical immunology, can be
reached at (919) 684-8823.
      Leonard Spicer, Ph.D., professor in the department of
radiology, can be reached at (919) 684-4327.
      Donna Kostyu, Ph.D., assistant research professor in the
department of immunology, can be reached at (919) 684-2840.
                               ###