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Roberts, Brian Joseph

Cell and Molecular Biology Program

2013

Ph. D.

Coxsackievirus B3 (CVB3) induces myocarditis, an inflammatory heart disease, which affects men 2:1 over women. Since their discovery, Toll-like receptors (TLR) have been shown to play an important role in the development of the immune response against harmful pathogens. TLR signaling has been shown to determine the severity of CVB3 induced myocarditis. While no direct role forsignaling through TLR2 had been shown in myocarditis, published studies show that cardiac myosin can act as an endogenous TLR2 ligand and stimulates pro-inflammatory cytokine expression by dendritic cells in vitro. The goal of this dissertation was to determine if differential TLR expression in CVB3 infected animals correlated to sex differences in disease susceptibility. To assess role of TLRs in sex differences in CVBJ-induced myocarditis, male and female mice were infected with 100 PFU of the H3 strain of CVB3 and harvested on day 3 or 6 post infection.
Hearts were removed and prepared for RNA and evaluated for differential gene expression by microarray. In addition hearts were evaluated for histology, viral titer and splenic lymphocytes were evaluated for TLR2 and TLR4 expression on different lymphocyte populations. Mice were additionally treated with either a TLR2 -specific ligand (PAM3CSK4) or a TLR4-specific ligand (Ultra-pure LPS). Our results show that CVB3 infection caused an upregulation of TLR2 in female mice and T. LR4 in male mice in both cardiac mRNA and on lymphocyte populations which correlates with resistance in females and susceptibility in males. Treatment of C57Bl/6 mice with either PAM or LPS resulted in an increase in Th1 expression in both male and female mice, but reduced Regulatory T-cell expression in male mice. The suppression of Tregs in male mice correlated with increased susceptibility in male mice.