Research
Interests:
Type 1 diabetes
(T1D or insulin-dependent diabetes mellitus, IDDM) results from
the autoimmune destruction of the insulin-producing pancreatic beta-cells.
Several target autoantigens have been identified, such as insulin/proinsulin,
glutamic acid decarboxylase (GAD), and a IA-2 tyrosine-phosphatase-like
protein known as IA-2. Both humoral and cellular immune responses
against these molecules are part of the autoimmune process leading
to beta-cell destruction, insulin deficiency, and finally diabetes.
There is growing evidence that these responses are dramatically
influenced by genetic factors (1;2). The Immunogenetics Laboratory
is dedicated to investigating the relationship between genetic factors
and the immune responses that lead to T1D.
Ongoing Research Projects:
Our research originates from the study of patients
and their families and aims at dissecting those genetically controlled
mechanisms that predispose or protect individuals from T1D. This
may prove helpful to devising strategies to prevent and cure diabetes
(3). It is in fact important that we are able to modulate the reactivity
of the immune system against beta-cells and their components in
order to prevent the recurrence of the original autoimmune attack
against any insulin-producing cells we may utilize to cure diabetes.
We are currently involved in both basic and clinical research projects
to dissect the genetic and immunological features of T1D.
Natural Expression and Genetic Control of Self-Antigens
Expression in the Thymus: Implications for Immunological Self-tolerance
and IDDM
Because proteins with tissue-restricted or peripheral expression
are traditionally thought to be unavailable for presentation in
the thymus, it has been proposed that tolerance to such proteins
can only be achieved through mechanisms of peripheral tolerance.
Against this traditional belief, recent evidence suggests that peripheral
molecules may also be expressed in the thymus (4). Overall, several
self-molecules have been detected in the thymus, including pancreatic
and thyroid hormones, neuroendocrine molecules, and other peripheral
proteins. We have discovered that the insulin, GAD, and IA-2, all
molecular targets of autoimmune responses in type 1 diabetes, are
expressed in human thymus throughout fetal life and childhood. Moreover,
allelic variation at the insulin gene diabetes susceptibility locus,
IDDM2, is associated with quantitative differences in the levels
of thymic insulin gene expression (5). This observation suggests
that differences in thymic insulin levels can modulate immune responsiveness
to insulin through effects on the negative selection of insulin-specific
autoreactive T cells. Our observation links the genetic risk of
diabetes with thymic selection processes specific for the insulin
autoantigen.
We
have also found that alternative splicing determines differential
expression of the IA-2 autoantigen in islets compared to thymus.
Islets express full-length mRNA and two alternatively spliced IA-2
transcripts while thymus exclusively expresses an alternatively
spliced transcript that comprises several T1D target epitopes, supporting
the concept that tolerance to IA-2 epitopes not expressed in the
thymus may not be achieved. Thus, alternative splicing of the IA-2
gene may facilitate the occurrence of autoimmune responses against
the IA-2 molecule (6).
The
studies outlined above about the expression of insulin and IA-2
in the thymus help in understanding the mechanisms by which genetic
factors control the risk of diabetes and the specific behavior of
autoreactive T-cells. Further progress in this area of investigation
has led us to identify a new subset of cells that express insulin
and other beta-cell molecules in the thymus. Moreover, these cells
exist not only in thymus but also in other organs of the immune
system, such as spleen and lymph nodes. We have conducted extensive
work to characterize these cells and obtained evidence that these
are “self-molecule-presenting cells” capable of delivering
a tolerogenic signal, in other words to induce tolerance to the
molecule they express (i.e., insulin) (7).
Genetic Studies in Families
Several genes are known or suspected to affect T1D risk. The HLA
region contains the known loci with the strongest effects, including
predisposing alleles and protective alleles. Over the past few years
we have focused on studying the genetic protection associated with
the DQB1*0602 allele (8-11). There is also evidence that additional
risk genes exist within/near the HLA complex and their characterization
may aid in predicting diabetes and improve our understanding of
the disease for prevention and therapy. We are actively involved
in an international collaboration to study the genetics of IDDM
and in particular to characterize the additional risk genes known
to exist in the HLA complex (12). This collaborative study is part
of the activities of the International
HLA Working Group.
The
Immunogenetics Program of the Diabetes Research Institute
Laboratory: Room 5335, Diabetes Research Institute
-
Alberto Pugliese, M.D., Principal Investigator
-
Carlos Garcia, M.D., Post-doctoral Fellow
- Kamalaveni Prabakar, Ph.D., Research Associate
- Gloria Allende, M.S., Research Associate
-
Rajpreet Dogra, B.S., Research Clinical Technician
Selected Publications:
- Pugliese,A. 2003. Genetics of Type 1 Diabetes. In Diabetes
from Research to Diagnosis and Treatment. I.Raz, Skyler,J.S.,
and Shafrir,E., editors. Martin Dunitz, London, New York. 11-34.
- Pugliese,A. and Miceli,D. 2002. The insulin gene in diabetes.
Diabetes Metab Res.Rev. 18:13-25.
- Pugliese,A. 2003. Peptide-based treatment for autoimmune diseases:
learning how to handle a double-edged sword. J.Clin.Invest 111:1280-1282.
- Pugliese,A. 2002. Peripheral antigen-expressing cells and autoimmunity.
Endocrinol.Metab Clin.North Am. 31:411-30, viii.
- Pugliese,A., Zeller,M., Fernandez,A.J., Zalcberg,L.J., Bartlett,R.J.,
Ricordi,C., Pietropaolo,M., Eisenbarth,G.S., Bennett,S.T., and
Patel,D.D. 1997. The insulin gene is transcribed in the human
thymus and transcription levels correlated with allelic variation
at the INS VNTR-IDDM2 susceptibility locus for type 1 diabetes.
Nat.Genet. 15:293-297.
- Diez,J., Park,Y., Zeller,M., Brown,D., Garza,D., Ricordi,C.,
Hutton,J., Eisenbarth,G.S., and Pugliese,A. 2001. Differential
splicing of the IA-2 mRNA in pancreas and lymphoid organs as a
permissive genetic mechanism for autoimmunity against the IA-2
IDDM autoantigen. Diabetes 50:895-900.
- Pugliese,A., Brown,D., Garza,D., Murchison,D., Zeller,M., Redondo,M.J.,
Diez,J., Eisenbarth,G.S., Patel,D.D., and Ricordi,C. 2001. Self-antigen
presenting cells expressing IDDM-associated autoantigens exist
in both thymus and peripheral lymphoid organs in humans. Journal
of Clinical Investigation 107:585-593.
- Pugliese,A., Kawasaki,E., Zeller,M., Yu,L., Babu,S., Solimena,M.,
Moraes,C.T., Pietropaolo,M., Friday,R.P., Trucco,M. et al. 1999.
Sequence analysis of the diabetes-protective human leukocyte antigen-DQB1*0602
allele in unaffected, islet cell antibody-positive first degree
relatives and in rare patients with type 1 diabetes. J.Clin.Endocrinol.Metab
84:1722-1728.
- Gianani,R., Verge,C.F., Moromisato-Gianani,R.I., Yu,L., Zhang,Y.J.,
Pugliese,A., and Eisenbarth,G.S. 1996. Limited loss of tolerance
to islet autoantigens in ICA+ first degree relatives of patients
with type I diabetes expressing the HLA DQB1*0602 allele. J.Autoimmun.
9:423-425.
- Pugliese,A., Gianani,R., Moromisato,R., Awdeh,Z.L., Alper,C.A.,
Erlich,H.A., Jackson,R.A., and Eisenbarth,G.S. 1995. HLA-DQB1*0602
is associated with dominant protection from diabetes even among
islet cell antibody-positive first-degree relatives of patients
with IDDM. Diabetes 44:608-613.
- Pugliese,A., Solimena,M., Awdeh,Z.L., Alper,C.A., Bugawan,T.,
Erlich,H.A., De Camilli,P., and Eisenbarth,G.S. 1993. Association
of HLA-DQB1*0201 with stiff-man syndrome. J.Clin.Endocrinol.Metab.
77:1550-1553.
- Pugliese,A., Li,H., Schoch,G., Thomson,G., Thorsby,E., Lathrop,M.,
Caillat-Zucman,S., Awdeh,Z., Babu,S., Berrino,M. et al. 2002.
The IDDM Component of the 13th International HLA Working Group:
A Preliminary Report. Diabetes Metabolism Research and Reviews
18:S14 (Abstr.)
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