The long-term goal of this new R29 proposal is to understand the antigenic determinants and immunologic requirements involved in alloimmunization. This proposal focuses on human platelet alloantigen 1 (HPA-1). HPA-1 is a biallelic system; a single nucleotide difference between alleles creates a polymorphism at position 33 of GP IIIa, a component of the fibrinogen receptor. Homozygotes for HPA-1a encode a leucine at position 33; homozygotes for HPA-1b encode proline. HPA-1 is the most common cause of two bleeding disorders, neonatal alloimmune thrombocytopenia and posttransfusion purpura. In both disorders, anti-HPA-1a antibodies are made against HPA-1a GPIIIa, leading to thrombocytopenia. In this proposal, experiments are designed to further explore the HPA-1a and test the feasibility of making a murine model. In pursuing this goal, important questions about the HPA-1 system will be addressed.
The specific aims are 1) to further define the structural requirements for HPA-1a antigenicity, 2) to determine if the structural requirements for HPA-1a antigenicity can be recreated in murine GPIIIa, and 3) to test the feasibility of making an animal model of HPA-1a alloimmunization by first creating a murine cell line expressing an HPA-1a fibrinogen receptor. By manipulating recombinant proteins containing human GPIIIa domains, the role of the polymorphism, the three N-terminal disulfide bonds, and the long range Cys5 Cys435 disulfide bond in HPA-1a antigenicity will be evaluated. This information will be used to recreate an HPA-1a-like antigen in murine GPIIIa and the criteria for eliciting an anti-HPA-1a response in mice will be determined. The ability of HPA-1a murine GPIIIa to assemble into a fibrinogen receptor and bind ligand in transfected megakaryoblastic cells will also be tested.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29HL059955-03
Application #
6184433
Study Section
Hematology Subcommittee 2 (HEM)
Project Start
1998-07-01
Project End
2003-06-30
Budget Start
2000-07-01
Budget End
2001-06-30
Support Year
3
Fiscal Year
2000
Total Cost
$113,400
Indirect Cost
Name
Johns Hopkins University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218