VRC
Home
Research Laboratories
Structural Virology Laboratory
Richard Wyatt, Ph.D.
Research
Statement
A daunting task in the development of a broadly
effective HIV-1 vaccine is to elicit humoral immune responses
directed toward conserved, functional elements of the HIV-1 exterior
envelope glycoprotein, gp120. Two functions common to virtually
all HIV-1 gp120 glycoproteins are the ability to bind the primary
virus receptor, CD4, and to bind to the more recently defined
co-receptors. In a collaborative study, we have recently solved
the crystal structure of gp120, in complex with CD4 and a neutralizing
antibody. This structure uniquely provides us with insight regarding
the means HIV-1 employs to mask these essential functional elements.
HIV-1 is tropic for CD4-positive cells by virtue
of the high affinity interaction between the HIV-1 gp120 glycoprotein,
and CD4, which acts as the primary virus receptor. The gp120 molecule
is derived from a gp160 precursor glycoprotein and noncovalently
associates with the transmembrane glycoprotein, gp41, to form
trimeric complexes on the virus or cell surface. The mature HIV-1
gp120 is comprised of five regions conserved among viral strains
(C1-C5) and five regions that exhibit considerable strain-to-strain
variability (V1-V5). Besides CD4, HIV-1 requires co-factors to
achieve entry into target cells. The second receptors used by
HIV-1, primarily CXCR4 and CCR5, belong to a family of seven-membrane
spanning, G-linked proteins which normally function as chemokine
receptors.
Schematic representation of modifications
used to produce soluble, stable HIV-1 trimeric envelope glycoproteins.
The two R to S changes render the molecules cleavage-defective
and maintain a covalent linkage between gp120 and gp41. These
changes, in combination with the addition of GCN4 trimeric
coiled coils, lend stability to the soluble envelope glycoproteins.
The additional introduction of cysteine residues at positions
576 and 577 further increase the stability of the oligomers. |
During the course of HIV-1 infection, neutralizing
antibodies are elicited against various elements of gp120. Neutralizing
antibodies appear to be an important component of the host immune
response. Most clinical (primary) HIV-1 isolates are relatively
resistant to neutralizing antibodies, suggesting that these viruses
are selected by the presence of neutralizing antibodies in infected
humans. In many HIV-1 infected individuals, two classes of neutralizing
antibodies are elicited: strain-restricted and broadly cross-reactive
antibodies. The strain-restricted antibodies appear early after
infection and are generally directed against linear determinants
within the gp120 third variable region. This class of antibodies
has been relatively easy to generate in both primate and non-primate
animal systems but are not broadly protective. A subset of the
broadly-neutralizing antibodies recognize conformationally-dependent,
discontinuous epitopes that overlap with the discontinuous CD4
binding site on gp120 and are termed CD4 binding site antibodies.
A second limited subset of broadly-neutralizing antibodies recognize
discontinuous gp120 epitopes, overlapping with the chemokine receptor
binding site, that are better exposed upon CD4 binding and thus
are referred to as CD4-induced antibodies. In naive individuals,
the presence of broadly cross-reactive neutralizing antibodies
and strain-restricted antibodies might help prevent or limit HIV-1
infection following exposure to the virus.
The broadly neutralizing antibodies, however, have
been difficult to elicit in animals using wild-type gp120 glycoproteins
as an immunogen. Through several hypotheses based upon evolving
structural information of HIV-1 envelope glycoproteins, we will
determine if rational modification of gp120 glycoproteins will
influence the exposure and presentation of conserved, functional
structures to the immune system. The elicitation of antibodies
with an expanded breadth of neutralization capacity may thereby
be enhanced. This rational approach to improve gp120 HIV-1 envelope
glycoprotein immunogenicity may have a significant impact on HIV-1
vaccine design.
Selected Publications:
- Wyatt R, Kwong P, Desjardins E, Sweet
R, Robinson J, Hendrickson W and Sodroski J. The antigenic
structure of the human immunodeficiency virus gp120 envelope
glycoprotein. Nature 1998;393:705-11.
- Kwong P, Wyatt R, Desjardins E, Sweet
R, Robinson J, Sodroski J and Hendrickson W. Structure
of an HIV gp120 envelope glycoprotein in complex with the CD4
and a neutralizing human antibody. Nature 1998;393:648-59.
- Rizzuto C, Wyatt R, Hernandez-Ramos,
Sun Y, Kwong P, Hendrickson W and Sodroski J. A conserved
human immunodeficiency virus gp120 glycoprotein structure involved
in chemokine receptor binding. Science 1998;280:1949-53.
- Wyatt R and Sodroski J. The
HIV-1 envelope glycoproteins: fusogens, antigens and immunogens.
Science 1998;280:1884-88.
- Farzan M, Choe H, Desjardins E, Sun Y,
Kuhn J, Cao J, Wyatt R, and Sodroski J. Stabilization
of HIV-1 envelope glycoprotein trimers by disulfide bonds introduced
into the gp41 glycoprotein ectodomain. J Virol 1998;72:7620-25.
- Kwong PD, Wyatt R, Desjardins E, Robinson
J, Culp JS, Hellmig BD, Sweet RW, Sodroski J, Hendrickson WA.
Probability analysis of variational crystallization and its
application to gp120, the exterior envelope glycoprotein of
type 1 human immunodeficiency virus (HIV-1). J Biol Chem 1999;274:4115-23.
- Mirzabekov T, Bannert N, Farzan M, Hofmann
W, Kolchinsky P, Wu L, Wyatt R, Sodroski J. Enhanced
expression, native purification, and characterization of CCR5,
a principal HIV-1 coreceptor. J Biol Chem 1999;274:28745-50.
- Kwong PD, Wyatt R, Sattentau QJ, Sodroski
J and Hendrickson WA. Oligomeric modeling and electrostatic
analysis of the gp120 envelope glycoprotein of human immunodeficiency
virus. J Virol 2000;74:1961-72.
- Yang X, Florin L, Farzan M, Kolchinsky
P, Kwong PD, Sodroski J and Wyatt R. Modifications
that stabilize human immunodeficiency virus envelope glycoprotein
trimers in solution. J Virol 2000;74:4746-4754.
- Myszka DG, Sweet RW, Hensley P, Birgham-Burke
M, Kwong PD, Hendrickson WA, Wyatt R, Sodroski J and Doyle M.
Energetics of the HIV gp120-CD4 Binding Reaction. Energetics
of the HIV gp120-CD4 binding reaction. Proc Natl Acad Sci U
S A. 2000 Aug 1;97(16):9026-31
- Koch M, Kwong PD, Kolchinsky P, Wang
L,Hendrickson W Sodroski J and Wyatt R. Structure-based,
Targeted Deglycosylation of the HIV-1 Exterior Envelope Glycoprotein,
gp120, and Effects on Neutralization Sensitivity. Submitted.
If you are interested in a Research Fellowship,
please send your CV to:
Dr. Richard Wyatt
NIH/Vaccine Research Center
40 Convent Drive
Bldg. 40, Room 4512
Bethesda, MD 20892-3005
Email: richw@mail.nih.gov |
|