Abstract

On average, 21 people in the United States die every day while waiting for a transplantable organ. Moreover, at the end of 2014, nearly 130,000 additional individuals were still on the transplant waiting list. Xenotransplantation, the transplantation of cells and/or organs from a member of another species, is both a viable supplement for, and bridge to, allotransplantation. Pigs are the favored organ donor because they: 1) breed and grow rapidly, 2) can be genetically modified, and 3) present few ethical concerns. However, due in part to their phylogenetic distance, several barriers must be successfully overcome before clinical xenotransplantation can be fully realized. Antibody deposition is presently a barrier to successful cardiac, renal, and non-encapsulated islet xenotransplantation; although all xenografts are likely susceptible to antibody-mediated damage. The purpose of this dissertation is twofold: 1) to provide further molecular characterization of the elicited antibodies which mediate rejection of porcine xenografts, and 2) to identify clinically applicable small molecules capable of selectively inhibiting these antibodies. We have found that vascular pig xenografts, and isolated porcine pancreatic islets, both elicit antibody responses encoded by structurally related antibody gene progenitors. These structurally related antibody gene progenitors are both known to encode human antibodies capable of inhibiting clotting factor VIII (FVIII). Therefore, we subsequently identified FVIII as a novel xenoantigen, and provided a preliminary molecular analysis of the interaction between FVIII and the antibodies elicited after xenotransplantation. Additionally, our analyses strongly suggested that it was feasible for a single reagent to inhibit the majority of the antibodies elicited against transplanted xenografts. Consequently, we screened for, and identified, a single clinically relevant small molecule drug which, when tested in vitro, inhibited elicited antibody from multiple xenotransplant settings. However, it was only when utilized in combination with a previously identified experimental reagent that it was possible to reduce the post-transplant antibody to levels below, or comparable to, those present before transplantation. These results challenge long-standing presumptions with regard to the nature of xenoantigens and their role in antibody-mediated xenograft rejection. Furthermore, identification of a clinically relevant selectively inhibitory small molecule should expedite transition into large animal work.

LLU Discipline

Pharmacology

Department

Basic Sciences

School

School of Medicine

First Advisor

Kearns-Jonker, Mary

Second Advisor

Buchholz, John N.

Third Advisor

Cowan, Peter J.

Fourth Advisor

Oberg, Kerby C.

Fifth Advisor

Payne, Kimberly J.

Sixth Advisor

Pearce, William J.

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

2015

Date (Title Page)

6-2015

Language

English

Library of Congress/MESH Subject Headings

Transplantation - Heterologous; Antibodies - Heterophile; Galactosyltransferases; Graft Rejection; Fucosyltransferases; Immunoglobulin M; von Willebrand Factor; Genetic Markers; Biomarkers; Molecular Sequence Data; Gene Knockout Techniques; Animals - Genetically Modified; Swine

Subject - Local

Organ transplants; Xenotransplantation; Allotransplantation; Pigs; Antibody Deposition; Xenografts; Antibody-mediated Damage

Type

Dissertation

Page Count

184

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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