University of Texas Health Science Center at Houston

Author Of 1 Presentation

Pathogenesis – Immunology Poster Presentation

P0971 - Immunoglobulins specific for Epstein-Barr virus proteins bind to microglia (ID 587)

Speakers
Presentation Number
P0971
Presentation Topic
Pathogenesis – Immunology

Abstract

Background

The etiology of multiple sclerosis (MS) is unknown, but there is a strong association with Epstein-Barr virus (EBV) infection. In healthy young adults, high levels of antibodies against the nuclear antigen EBNA-1 predict increased risk of MS. Some studies report that antibodies to the small EBV capsid protein, BFRF3, are associated with more severe MRI findings in MS patients. In previous studies, we have shown that antibodies to the EBV antigens EBNA-1, BFRF3, and the tegument protein BRRF2 are increased in MS, but antibodies to other EBV antigens are not. The role that EBV plays in MS is controversial, and a mechanism by which EBV infection would cause MS has not been established. We propose the hypothesis that antibodies to these three EBV antigens have a direct pathogenic effect and contribute to the disease process of MS.

Objectives

The objective of this work was to determine if antibodies to EBNA-1, BFRF3, or BRRF2 have direct pathogenic effects on central nervous system cells.

Methods

The EBV proteins BFRF3 and BRRF2 were produced in our laboratory from recombinant bacteria. EBNA-1 was purchased from commercial sources. Proteins were coupled to agarose beads to create affinity columns. Blood was obtained from MS patients in clinic, and plasma was separated and stored frozen at -80. For each antibody extraction, we combined plasma from 10 to 20 MS patients. We extract antibodies specific for the 3 EBV proteins with affinity columns. The concentration of the extracted antibodies is measured with ELISA and the specificity is confirmed with Western blot. Unselected IgG from MS patients and healthy controls was used as a control. Initial experiments were done with mixed cultures of CNS cells derived from rats. Subsequent experiments were done with the human microglial HMC3 cell line. Immunoglobulin was added to the cells, incubated for various amounts of time, and then the cells were used for immunohistochemistry, MTT assay, or proliferation assay.

Results

Antibodies to each of the 3 EBV antigens bound to cells in the mixed rat CNS cell cultures. Double labeling with antibodies specific for the various types of cells demonstrated that the majority of the binding was to microglia. There was no consistent binding to oligodendrocytes, neurons, or astrocytes. Antibodies to each of the EBV antigens also bound to human microglial HMC3 cells. There was some variation in the binding pattern depending on specificity of the antibody. The antibodies caused a modest decrease in proliferation and metabolic activity of the HMC3 cells. Assessment of effects on RNA expression are in progress.

Conclusions

Antibodies to EBV antigens bind to microglia. Further experiments are needed to clarify the effects of the antibodies on microglia and whether these antibodies play a role in the pathogenesis of MS.

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