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Current Molecular Medicine
ISSN: 1566-5240
Current Molecular Medicine
Volume 7, Number 4, June 2007
Contents
Tuberculosis (Part 2)*
Guest Editor: Douglas B. Lowrie
Mycobacterial Heat Shock Proteins as Vaccines - A
Model of Facilitated Antigen Presentation Pp. 339-350
K. Barry Walker, James Keeble and Camilo Colaco
[Abstract]
Epitope-Driven TB Vaccine Development: A Streamlined
Approach Using Immuno-Informatics, ELISpot Assays, and HLA
Transgenic Mice Pp. 351-363
Julie A. McMurry, Sarah Kimball, Jin Hee Lee, Daniel Rivera,
William Martin, David B. Weiner, Michele Kutzler, David R.
Sherman, Hardy Kornfeld and Anne S. De Groot
[Abstract]
Recombinant BCG Vaccine Candidates Pp. 365-372
Rogelio Hernàndez-Pando, Mauricio Castañòn,
Clara Espitia and Yolanda Lopez-Vidal
[Abstract]
Current Strategies in TB Immunotherapy Pp.
373-386
Eleanor Roy, Douglas B. Lowrie and Stephen R. Jolles
[Abstract]
Novel Perspectives on Glycosylation and Human
Disease
Guest Editor: Hudson H. Freeze
Editorial Pp. 387
Hudson H. Freeze
Congenital Disorders of Glycosylation: CDG-I,
CDG-II, and Beyond Pp. 389-396
Hudson H. Freeze
[Abstract]
Clinical Laboratory Testing in Human Medicine Based
on the Detection of Glycoconjugates Pp. 397-416
Benjamin L. Schulz, Wouter Laroy and NicoCallewaert
[Abstract]
Congenital Muscular Dystrophies Involving the O-Mannose
Pathway Pp. 417-425
Paul T. Martin
[Abstract]
Notch Signaling in Normal and Disease States: Possible
Therapies Related to Glycosylation Pp. 427-445
Raajit Rampal, Kelvin B. Luther and Robert S. Haltiwanger
[Abstract]
Abstracts
[Back to top]
Mycobacterial Heat Shock Proteins as Vaccines
- A Model of Facilitated Antigen Presentation
K. Barry Walker, James Keeble and Camilo Colaco
Heat shock proteins (hsps) are a highly conserved family of
proteins, first recognized by their upregulated expression
in response to host exposure to raised temperatures. Further
study has revealed that they have numerous functions in the
cell, primarily as chaperones mediating both the correct folding
of nascent polypeptide chains and the dissolution of aggregated
protein complexes. The energy requirement for this chaperone
activity is provided by the ATPase activity found in most
families of hsps and thus the peptide binding capacity is
controlled by ATP hydrolysis. The structural consequence of
this is that hsps isolated in situ are found complexed
to chaperoned peptides (hspCs). Much previous work has implicated
hsps in the immune response to pathogens and recent studies
have shown that the interaction of hsps with antigen presenting
cells, such as dendritic cells (DCs), mediates the integration
of the innate and acquired immune responses. This central
role for hspCs in immunity is facilitated by their dual function
in both innate immunity, with the induction of cytokines and
the maturation of DCs mediated by the hsp component, and acquired
immunity, with the trafficking of antigens chaperoned in hspCs
for antigen presentation by the mature DCs.
[Back to top]
Epitope-Driven TB Vaccine Development: A Streamlined
Approach Using Immuno-Informatics, ELISpot Assays, and HLA
Transgenic Mice
Julie A. McMurry, Sarah Kimball, Jin Hee Lee, Daniel Rivera,
William Martin, David B. Weiner, Michele Kutzler, David R.
Sherman, Hardy Kornfeld and Anne S. De Groot
New vaccine candidates that might better control the worldwide
prevalence of Mycobacterium tuberculosis (Mtb) have
yet to be described. Strong CD4+ T cell-mediated immune response
(CMI) is correlated with protection from the development of
TB disease; however, the selection of suitable vaccine antigens
has been thwarted by the size and complexity of the (Mtb)
proteome, and by the relative difficulty of delivering these
antigens in the right immunological context. One possible
solution is to develop immunotherapeutic vaccines for TB that
are based on T cell epitopes representing multiple antigens.
This text illustrates the stepwise development of epitope-driven
vaccines from in silico epitope mapping to testing
the vaccine in a live Mtb challenge model. First, we used
the whole genome Mtb microarray to identify bacterial proteins
expressed under the conditions thought to model Mtb survival
and replication in human macrophages. Eighteen of these proteins
were also found by Behr et al. to be absent from
at least one strain of BCG; the sequences of these eighteen
proteins were then screened for T-cell epitopes using the
immuno-informatics algorithm, EpiMatrix. Of the seventeen
representative epitopes evaluated in ELISpot assays, all seventeen
were confirmed to elicit interferon (IFN)-gamma secretion
by PBMC from Mtb-exposed subjects. A parallel live Mtb challenge
study in mice showed prototype epitope-based TB vaccines to
be robustly immunogenic but not as effective as BCG. These
experiments illustrate the use of immuno-informatics tools
for vaccine development and describe a pathway for the development
of a more effective, epitope-driven, immunotherapeutic vaccine
for TB.
[Back to top]
Recombinant BCG Vaccine Candidates
Rogelio Hernàndez-Pando, Mauricio Castañòn,
Clara Espitia and Yolanda Lopez-Vidal
Given the variable protective efficacy provided by Mycobacterium
bovis BCG (Bacillus Calmette-Guérin), there is
a concerted effort worldwide to develop better vaccines that
could be used to reduce the burden of tuberculosis. Recombinant
BCG (rBCG) are vaccine candidates that offer some potential
in this area. In this paper, we will discuss the molecular
methods used to generate rBCG, and the results obtained with
some of these new vaccines as compared with the conventional
BCG vaccine in diverse animal models. Tuberculosis vaccine
candidates based on rBCG are promising candidates, and some
of them are now being tested in clinical trials.
[Back to top]
Current Strategies in TB Immunotherapy
Eleanor Roy, Douglas B. Lowrie and Stephen R. Jolles
Currently available chemotherapy for the treatment of
pulmonary tuberculosis (TB) is far from ideal, requiring multiple
anti-tuberculous drugs to be taken in combination for extended
time periods. This long duration of therapy, coupled with
the side effects of current regimens, often results in poor
patient adherence, treatment failure and the associated emergence
of drug resistance with major financial implications. Thus,
the development of novel, shorter treatment regimens is an
urgent objective of anti-tuberculous drug discovery. Immunotherapy
is an area that merits more consideration than it has previously
received, not least, as it could potentially avoid the problem
of pathogen resistance. However, this must be undertaken with
caution, as at least part of the disease pathology is a consequence
of the host immune response. Thus, the protective, and not
the harmful, aspects of immunity must be stimulated. Various
attempts at utilizing immunotherapy as an adjunct to chemotherapy
are reviewed with particular emphasis on the evidence from
human studies, including the modulation of cytokine levels,
administration of environmental mycobacteria and antibody
therapy, in order to modulate or enhance the host immune response
to Mycobacterium tuberculosis.
[Back to top]
Editorial
Hudson H. Freeze
This issue of Current Molecular Medicine has
a series of four articles that focus on Glycobiology in Medicine.
In the last decade it has become clear that defective protein
glycosylation—the physiological addition of sugar chains,
or glycans, results in human disease. Impressive progress
has been made in the identification of more than 35 inherited
diseases that affect human development and nearly every organ
system. The glycan-dependent development of the nervous system,
the high demand for glycosylated proteins in the liver and
rapid turnover of glycoproteins in the gastrointestinal tract
make these organs particularly susceptible to perturbations
in normal glycan addition. The Congenital Disorders of Glycosylation
(CDG) cover a broad spectrum of clinical phenotypes making
these autosomal recessive defects particularly difficult for
physicians to recognize and diagnose. Clinically-oriented
collaborations between glycobiologists and physicians led
to the diagnosis of many patients and to novel insights into
the roles of glycans in human and mammalian physiology. Continuing
that collaboration in search of new glycosylation disorders
presents some unexpected challenges in diagnosis, but solving
them will likely produce novel insights into the “well-understood”
N-glycosylation pathway. Freeze gives one example of such
a challenge. Glycan-based diagnosis was critical for the progress
in discovery of these disorders.
Renewed and expanded appreciation of glycans as disease diagnostic
markers makes the review by Schluz, et al., quite timely.
This thorough and insightful analysis is impressive for the
breadth of medical settings in which glycans serve as both
diagnostic and therapeutic agents. The search for Glycobiomarkers
of cancer recently spawned a serious in-depth program sponsored
by the National Cancer Institute seeking a consortium of glycobiologists
to study promising markers of disease progression and therapy.
In a review on potential therapy for congenital muscular dystrophies
resulting from faulty glycosylation, Paul Martin provides
a clear and critical insider’s view of the potential
for gene manipulation in this series of disorders. Here again,
a decade ago, even within the glycobiology community, O-mannose
linked glycans were regarded as a curiosity. Their identification
on α-dystroglycan,
member of the dystrophin glycoprotein complex, found in the
brain and in neuromuscular junctions presented a novel perspective
since the glycans were implicated in ligand binding to S-laminin.
Antibodies that recognize these glycans on α-dystroglycan
have severely reduced binding in several types of muscular
dystrophy disorders.
Another curiosity in the Glycobiology field was the discovery
of novel types of glycosylation in proteins containing EGF-like
repeats. These O-Fucose based glycans were later found in
conserved domains in Notch proteins that are involved in critical
signaling pathways during development and adult life. Initial
O-fucosylation and further modifications influence the potentiation
of ligand binding and signaling. Moreover, defects in these
signaling pathways have been implicated in a series of human
diseases. The review by Rampal, et al, highlights
the importance of glycosylation in normal Notch signaling
and discusses how targeting this type of glycosylation may
have therapeutic potential.
These reviews only touch the surface, giving a glimpse of
a few medical aspects of glycosylation. Many of these subjects
are now appearing in recent revisions of traditional medical
specialty textbooks. The conversation between physicians and
basic glyco-scientists needs to continue with the goal of
enriching that already fertile ground for the benefit of afflicted
patients, dedicated physicians and curious scientists.
Hudson H. Freeze
Professor of Glycobiology, Director
Glycobiology and Carbohydrate Chemistry Program
Burnham Institute for Medical Research
10901 N. Torrey Pines Rd.
La Jolla, CA 92037
USA
Tel: 858-646-3142
Fax: 858-713-6281
E-mail: hudson@burnham.org
[Back to top]
Congenital Disorders of Glycosylation: CDG-I,
CDG-II, and Beyond
Hudson H. Freeze
The Congenital Disorders of Glycosylation (CDG) are a collection
of over 20 inherited diseases that impair protein N-glycosylation.
The clinical appearance of CDG patients is quite diverse making
it difficult for physicians to recognize them. A simple blood
test of transferrin glycosylation status signals a glycosylation
abnormality, but not the specific defect. An abnormal trasferrin
glycosylation pattern suggests that the defect is in either
genes that synthesize and add the precursor glycan (Glc3Man9GlcNAc2)
to proteins (Type I) or genes that process the protein-bound
N-glycans (Type II). Type I defects create unoccupied glycosylation
sites, while Type II defects give fully occupied sites with
abnormally processed glycans. These types are expected to
be mutually exclusive, but a group of patients is now emerging
who have variable coagulopathy and hypoglycemia together with
a combination of Type I and Type II transferrin features.
This surprising finding makes identifying their defects more
challenging, but the defects and associated clinical manifestations
of these patients suggest that the N-glycosylation pathway
has some secrets left to share.
[Back to top]
Clinical Laboratory Testing in Human Medicine Based
on the Detection of Glycoconjugates
Benjamin L. Schulz, Wouter Laroy and NicoCallewaert
The purpose of this review is to provide a concise overview
of developments over the last 15 years in the field of laboratory
tests in human medicine that are based on the detection of
alterations in the glycan part of glycoconjugates. We show
how glycosylation-based diagnostic testing is widespread in
the current clinical practice, in different formats. To provide
the necessary focus in this extremely broad field, we have
only included assays that are either in actual clinical use
or that are under active development towards clinical use,
with some bias towards assays that were recently developed.
The fields included are: cancer, infectious disease, genetic
defects of glycoconjugate biosynthesis and catabolism, auto-immunity,
drug abuse and liver disease.
To conclude this review, we provide a viewpoint on the future
of the glyco-diagnostics field in terms of novel technologies,
especially with regard to the discovery and clinical implementation
of biomarkers that are based on pathologically altered endogenous
glycotopes.
[Back to top]
Congenital Muscular Dystrophies Involving the O-Mannose
Pathway
Paul T. Martin
A number of forms of congenital muscular dystrophy (CMD) have
been identified that involve defects in the glycosylation
of dystroglycan with O-mannosyl-linked glycans. There are
at least six genes that can affect this type of glycosylation,
and defects in these genes give rise to disorders that have
many aspects of muscle and brain pathology in common. Overexpression
of one gene implicated in CMD, LARGE, was recently
shown to increase dystroglycan glycosylation and restore its
function in cells taken from CMD patients. Overexpression
of Galgt2, a glycosyltransferase not implicated in CMD, also
alters dystroglycan glycosylation and inhibits muscular dystrophy
in a mouse model of Duchenne muscular dystrophy. These findings
suggest that a common approach to therapy in muscular dystrophies
may be to increase the glycosylation of dystroglycan with
particular glycan structures.
[Back to top]
Notch Signaling in Normal and Disease States: Possible
Therapies Related to Glycosylation
Raajit Rampal, Kelvin B. Luther and Robert S. Haltiwanger
The Notch signaling pathway is involved in a wide variety
of highly conserved developmental processes in mammals. Importantly,
mutations of the Notch protein and components of its signaling
pathway have been implicated in an array of human diseases
(T-cell leukemia and other cancers, Multiple Sclerosis, CADASIL,
Alagille Syndrome, Spondylocostal Dysostosis). In mammals,
Notch becomes activated upon binding of its extracellular
domain to ligands (Delta and Jagged/Serrate) that are present
on the surface of apposed cells. The extracellular domain
of Notch contains up to 36 tandem Epidermal Growth Factor-like
(EGF) repeats. Many of these EGF repeats are modified at evolutionarily-conserved
consensus sites by an unusual form of O-glycosylation
called O-fucose. Work from several groups indicates
that O-fucosylation plays an important role in ligand
mediated Notch signaling. Recent evidence also suggests that
the enzyme responsible for addition of O-fucose to
Notch, protein O-fucosyltransferase-1 (POFUT1), may
serve a quality control function in the endoplasmic reticulum.
Additionally, some of the O-fucose moieties are further
elongated by the action of members of the Fringe family of
β-1,3-N-acetylglucosaminyltransferases.
The alteration in O-fucose saccharide structure caused
by Fringe modulates the response of Notch to its ligands.
Thus, glycosylation serves an important role in regulating
Notch activity. This review focuses on the role of glycosylation
in the normal functioning of the Notch pathway. As well, potential
roles for glycosylation in Notch-related human diseases, and
possible roles for therapeutic targeting of POFUT1 and Fringe
in Notch-related human diseases, are discussed.
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