Date of Award

12-2009

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Microbiology

Advisor

Carol Kim

Second Committee Member

Paul Millard

Third Committee Member

Keith W. Hutchison

Abstract

Under certain conditions, membrane bilayers can undergo a lateral phase separation into liquid ordered (10) and liquid-disordered (la) domains. Clusters of saturated lipids, cholesterol, and proteins that form 10 domains are also known as lipid rafts. Lipid rafts are associated with a number of diseases (e.g. Alzheimer's, atherosclerosis) as well as viral infections. These nanodomains act as localized signaling centers on the cell's membranes. Caveolae are lipid rafts made up of oligomerized caveolin protein and cholesterol. Caveolin-1, in mammals, has been shown to play a role in inflammation and immune responses against bacteria and protozoa. Never before have caveolin-la and caveolin-lb been linked to the disruption of the innate immune response against viral infection. In this study we show that both isoforms of the gene cavla and cavlb in the zebrafish are needed to fight viral infection by snakehead rhabdovirus (SHRV). Cavla and cavlb expression levels were modulated upon virus infection as shown by quantitative RT-PCR. Morpholino knockdown of cavla and cavlb in zebrafish has shown that caveolin-la and caveolin-lb both are needed to clear the SHRV infection. Upon knockdown, cavla- and cav16-depleted juvenile zebrafish show a striking increase in mortality compared to standard control morpholino injected fish. The decline in viral clearance was due to a decreased innate immune response shown by means of respiratory burst assay. We have also shown that zebrafish liver cells that are deficient in cav1a and cav1b show dampened Type 1 IFN promoter activity and Interferon Stimulated Regulatory Element (ISRE) activity after exposure to poly(I:C). Fluorescence PhotoActivation Localization Microscopy (FPALM) studies demonstrated that cav1a and cav1b are colocalized with the zebrafish homolog of the interferon A receptor (IFNAR), CRFB1. These studies provide the first evidence that caveolin-1 modulates the innate immune system during SHRV infection and show lipid raft nanodomains might be used by zebrafish to elicit a broad range innate immune responses

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