(487f) Antigenic Disguise of Model Surfaces Via Immobilization of Treponema Pallidum Protein Tp0483

Authors: 
Abney, M. B., University of Kentucky
Anderson, K. W., University of Kentucky
Bachas, L., University of Kentucky
Cameron, C. E., University of Victoria


Monumental advances in medicine and medical procedures in recent decades have led to the development of remarkable tools necessary for the field. However, due to the ability of the human immune system to target foreign bodies with such ferocity, all blood contacting devices must be created to limit the immune response. A biocompatible surface, by definition, is a surface that may be placed in the human body that will neither illicit a negative response by the immune system, nor be adversely affected by the body into which it is placed. A hemocompatible surface, is a blood compatible surface and is subject to the same provisions as a biocompatible surface with relation to the blood. Many surface coatings and materials have been employed for the purpose of hemocompatibility. However, due to the nature of the immune response, a wholly hemocompatible surface has yet to be produced. The purpose of this work is investigate the use of antigenic disguise to create a hemocompatible surface. Treponema pallidum, a spirochete bacterium and known cause of syphilis, has been extensively studied due the severity of the disease it causes. While the primary and secondary stages of the disease occur within months of infection, the disease often becomes latent for years. Documented cases have shown the disease latent up to five decades. Antigenic disguise occurs when a pathogen attaches host proteins to itself in an attempt to either infiltrate host cells or to avoid immune detection. This is a possible explanation regarding the ability of T.pallidum to remain undetected in the body for such long periods of time. T. pallidum is known to bind fibronectin (FN) and is believed to use this protein for the purpose of antigenic disguise. The purpose of this study is to create a surface that mimics the antigenic disguise properties of T. pallidum in an effort to produce a hemocompatible surface. For this purpose, Tp0483, a putative treponemal outer membrane protein that has been shown to bind both plasma and matrix FN, was studied. This protein was adsorbed to model surfaces made up of functionalized alkanethiol self-assembled monolayers (SAMs). Surfaces included a hydrophobic ?CH3 surface, a neutral hydrophilic ?OH surface, a negatively charged ?COOH surface, and a positively charged ?NH2 surface. All SAMs were characterized via contact angle and X-ray photoelectron microscopy (XPS). FN was subsequently exposed to Tp0483 on each of the surfaces using a Biacore surface plasmon resonance (SPR). Studies showed significant binding of Tp0483 to all surfaces. However, there was no statistical difference in binding between the surfaces (p>>0.05). Relative binding of FN was determined by comparing binding of FN to Tp0483 to FN on the functionalized surface alone (without Tp0483). Relative binding of FN to was found to be less than 4% to ?CH3, ?NH2 and ?OH surfaces whereas relative binding to the ?COOH surface was found to be approximately 16%. Antibody studies to determine the binding site for FN to Tp0483 will be discussed along with studies on the attachment of other plasma proteins (fibrinogen, human serum albumin, and vitronectin) to the Tp0483.