Date of Award

4-30-2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

First Advisor

Dr. Roberta Attanasio - Chair

Second Advisor

Dr. Franco Scinicariello

Third Advisor

Dr. Delon Barfuss

Fourth Advisor

Dr. Barbara Baumstark

Abstract

Host defense against infection and disease relies on the reciprocal communication between the immune and neuroendocrine systems where sex hormones exert negative and positive feedback actions on immune functions. Indeed, sex hormones have been implicated in gender dimorphic immune response and in the potentiation of immune-related disorders. The female hormone estrogen plays a role as an immunomodulator and may exert immunosuppressive and immunostimulatory effects. Though many studies focus on estrogen’s role in immunity within the female reproductive tract and autoimmunity, the modulatory effects of estrogen on vaccine responses are largely unexplored. The insufficient efficacy of some vaccines in certain target populations, as for example the elderly population, is well recognized. Hormones fluctuate throughout an individual’s life, and females in particular undergo several necessary reproductive (pregnancy and menopause) and lifestyle (oral contraceptive use) changes which involve sex hormones. Vaccine efficacy might be influenced by endogenous estrogen levels or by exogenous estrogen administration. Therefore, in the pursuit of improved vaccine efficacy, it is necessary to consider such hormonal factors and their contribution to immune status. We have studied estrogen’s role in modulation of vaccine responses using a mouse ovariectomy model where exogenous estrogen delivery can be controlled. Our studies included two different types of vaccines, a bacterial toxoid formulation and a bacterial secreted protein formulation. Results from these studies indicate that estrogen enhances vaccine-specific antibody production by likely supporting a general TH2 pathway and also modulates expression of genes encoding molecules critical in innate immune signaling and required for development of proper adaptive immune responses and antigen clearance through antibody-mediated mechanisms. The level at which estrogen modulates antibody responses appears to be dependent on the route of vaccine administration. The enhancement of specific humoral responses may involve mechanisms involving TLR2 and antibody Fc receptor expression on macrophages, cells that link innate and adaptive immune responses. Advances in our understanding of the relationship between sex hormones and the immune system may provide new insights into the mechanisms by which hormones act and thus may be exploited to guide the design of future vaccine strategies.

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Biology Commons

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