Browsing by Author "Dr. Fred Fuller, Committee Member"

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Characterization of the Prostaglandin E2 Response to Poxvirus Infection and of a Novel Poxvirus Antiviral
(2009-12-18) Pollara, Joseph; Dr. Frank Scholle, Committee Member; Dr. Fred Fuller, Committee Member; Dr. Ian T. D. Petty, Committee Chair; Dr. Scott M. Laster, Committee Member
The Role of the B7 Co-stimulation Pathway in Feline Immunodeficiency Virus (FIV) and Human Immunodeficiency Virus (HIV)Associated T cell depletion
(2003-03-09) Bull, Marta Eileen; Dr. Mary Tompkins, Committee Member; Dr. Wayne Tompkins, Committee Chair; Dr. Fred Fuller, Committee Member; Dr. Holly Jordan, Committee Member; Dr. Gregg Dean, Committee Member
Feline immunodeficiency virus (FIV) in the domestic cat provides a good animal model for dissecting the immunopathology associated with HIV infected individuals, as the immune dysfunction in the cat replicates the immune deterioration in humans. Lentiviruses characteristically cause a gradual loss in T-helper cells numbers and functions. A variety of mechanisms have been proposed to account for lentivirus-induced T cell depletion although none of these mechanisms alone account for all the T cell changes. The B7/cytotoxic T lymphocyte antigen four (CTLA4) signaling pathway is a major signaling pathway in the initiation and termination of T cell immune responses. The B7 receptors are normally expressed on the surface of antigen presenting cells (APC), while CD28 and CTLA4 are differentially expressed on the surface of T cells. Recent studies show that chronic stimulation in vitro or in vivo results in an unusual increase in the percent of T cells that express the B7 and CTLA4 molecules. These chronically activated T cells also up-regulate major histocompatibility complex class II molecules (MHC II) and are capable of inducing anergy and apoptosis of other activated T cells. In this study we found that individuals with a HIV or FIV infections had increased expression of B7 and CTLA4 on T cells in peripheral blood and lymph nodes (LN). These B7+CTLA4+ T cells were associated with an increased frequency of spontaneous apoptosis. Analysis of MHCII receptor expression on PBMC from HIV infected patients revealed a significant increase in MHCII+ expression on B7+ or CTLA4+ T cells. TUNEL analysis of B7+MHCII+ or CTLA4+MHCII+ compared to B7+MHCIIneg or CTLA4+MHCIIneg T cells revealed that the increased frequency of T cell apoptosis could almost exclusively be attributed to B7+MHCII+ and CTLA4+MHCII+ T cells, similar to our observations in the cat From these data we hypothesize that T: T interactions between CD4+ and CD8+ B7+CTLA4+MHCII+ T cells within the LN results in IL2 inhibition rendering them susceptible to cytokine deprived apoptosis.
Strategies for the Management of Strawberry Anthracnose
(2006-04-27) Schwegel, Rosemary; Dr. Frank Louws, Committee Chair; Dr. Marc Cubeta, Committee Member; Dr. Fred Fuller, Committee Member; Dr. Jean Ristaino, Committee Member
Strawberry anthracnose, which can be caused by Colletotrichum acutatum, C. dematium, C. fragariae, or C. gloeosporioides, is an economically important disease in North Carolina. As a response to the Fall 2003 anthracnose epidemic in NC resulting from the use of latently infected Canadian planting stock, three related studies were conducted to present management options for this disease, which is difficult to control chemically and is often introduced through planting stock. First, to secure a source of uninfected plants, three strawberry transplant sources (NC Registered, NC Certified, and noncertified Canadian) were evaluated in the field for the presence of anthracnose and horticultural characteristics. None of the plants showed symptoms of anthracnose. The Canadian plants showed significantly greater leaf dry weights, root dry weights, and leaf areas before planting, but this difference decreased over time. Crown dry weights of the Canadian plants remained greater on average than those of the NC plants over the course of the growing season. Root health ratings for the Canadian plants were significantly greater than those of the NC plants at the peak bloom and harvest samplings. The Canadian plants produced a significantly greater total berry number (69% greater) and weight (53% greater) but a slightly lower average berry size than the North Carolina-produced plants. This difference in yield may be due to the difference in transplant size, the difference in root health, or the possibility that NC-grown plants require more frequent overhead watering after planting for good establishment. In a second study designed to evaluate diagnosis and control measures for the disease, petioles were sampled at two sites in NC, each containing 30,000 plug plants, 105 petioles from the first site and 100 from the second. The level of infection was evaluated visually in the field and by a bioassay of the collected petioles in which the petioles were treated with herbicide to induce senescence of the plant tissue and encourage fungal sporulation. Spore suspensions of isolates collected from the sampled petioles were plated on media containing the strobilurin fungicide pyraclostrobin, and the percent germination was compared to the incidence of germination for isolates which had never been exposed to strobilurin fungicides. The collected isolates were not found to be resistant to pyraclostrobin, indicating that this fungicide may prove to be a viable management option for strawberry anthracnose in fruiting fields. In the third study, a real-time PCR protocol for detection of Colletotrichum spp. in strawberry petiole tissue was developed and compared to the previously described bioassay method. Petioles were sampled from strawberry plants grown in a controlled environment and artificially inoculated with C. acutatum, and from field-grown strawberry plants naturally infected with C. gloeosporioides; the sampled petioles were screened using both assays. The real-time PCR protocol was more rapid and showed significantly greater sensitivity than the bioassay when evaluating the artificially inoculated petioles. A lack of sensitivity in the real-time PCR assay was observed when evaluating the naturally infected petioles; this problem was likely due to poor tissue disruption of the tougher field-grown petioles during the DNA extraction protocol. Once issues of contamination and poor tissue disruption are addressed, real-time PCR may become an important tool for sensitive and specific detection of Colletotrichum spp. in strawberry tissue.