Author

John M. Jones

Date

June 2008

Document Type

Dissertation

Degree Name

Ph.D.

Department

Dept. of Molecular Microbiology and Immunology

Institution

Oregon Health & Science University

Abstract

Chemokines are small, secreted cytokines with the capacity to induce cellular migration, also referred to as chemotaxis. Although primarily known for their ability to mediate leukocyte migration as part of the immune response to injury or pathogenic insult, chemokines also play an integral role in a variety of cellular processes like tissue and organ development, angiogenesis, and hematopoiesis. As such, some viruses have evolved mechanisms to either mimic or subvert normal chemokine function in an attempt to further their own lifecycle. In this work, we will address two such proteins, one, a chemokine homolog encoded by rhesus rhadinovirus, the other, a chemokine inhibitor encoded by monkeypox virus. Rhesus rhadinovirus (RRV) is the simian homolog of Kaposi sarcoma-associated herpesvirus (KSHV), and like KSHV, it encodes a viral macrophage inflammatory protein homolog (RRV vMIP) that, in many respects, mimics the function of cellular chemokine, rhesus macrophage inflammatory protein-1α (MIP-1α). In the first half of this thesis, we show that recombinant RRV vMIP induces migration of monocytic THP-1 cells in vitro. Moreover, RRV vMIP -saturated implants induce the recruitment of CD14+ cells in vivo, suggesting RRV vMIP might function as a chemokine during RRV infection. Acute in vitro infection of isolated peripheral blood mononuclear cells (PBMC) with RRV shows that CD14+ cells are permissive to RRV infection. Taken together, these data strongly suggest that RRV vMIP encodes a functional chemokine with the ability to recruit permissive CD14+ cells during acute infection, which may provide a mechanism for viral dissemination. Monkeypox virus (MPV) is an orthopoxvirus with considerable homology to variola major, the etiologic agent of smallpox. Like other orthopoxviruses, MPV encodes a secreted chemokine binding protein, MPV vCCI, that is abundantly expressed and secreted during MPV infection. In the second half of this thesis, we show via Electrophoretic mobility shift assay (EMSA) that MPV vCCI efficiently binds rhesus MIP-1α (rhMIP-1α). Furthermore, in vitro chemotaxis experiments demonstrate that MPV vCCI completely inhibits rhMIP-1α mediated chemotaxis, while in vivo recruitment assays in rhesus macaques using chemokine-saturated implants show a decrease in the number of CD14+ cells responding to rhMIP-1α when MPV vCCI is present, suggesting MPV vCCI is effectively inhibiting chemokine function both in vitro and in vivo. More importantly, we demonstrate that MPV vCCI can diminish the severity of the acute phase of infection and completely inhibit the relapsing phase of experimental allergic encephalomyelitis (EAE) disease. These data represent the first in vitro and in vivo characterization of MPV vCCI emphasizing its function as a potent inhibitor of rhMIP-1α. Furthermore, the ability of MPV vCCI to inhibit relapsing EAE disease represents a novel therapeutic approach for treating chemokine-mediated diseases.

Identifier

doi:10.6083/M4CF9N2W

School

School of Medicine

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