Browsing by Subject "immunology"
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Item An inhalation model of acute Q fever in guinea pigs(2009-05-15) Russell-Lodrigue, Kasi ElizabethCoxiella burnetii is an intracellular pathogen that can cause both acute and chronic disease (Q fever) in humans and infects many animals with varying clinical illness and persistence. A guinea pig aerosol-challenge model of acute Q fever was developed using infection with C. burnetii across a 5-log range of challenge doses. Clinical signs included fever, weight loss, respiratory difficulty, and death, with degree and duration of response corresponding to dose of organism delivered. Histopathologic evaluation revealed coalescing panleukocytic bronchointerstitial pneumonia 7 days after a high-dose challenge, resolving to multifocal lymphohistiocytic interstitial pneumonia by 28 days. Clinical and pathologic changes noted in these guinea pigs were comparable to those seen in human acute Q fever, making this an accurate and valuable animal model. This model was used to compare the relative virulence of eight isolates from four different genotypic groups: I (RSA493, RSA334, and RSA270), IV (Q177 and Q173), V (Q212 and Q217), and VI (5J108-111). Guinea pigs infected with group I acute-diseaseassociated isolates had severe respiratory disease, while no to moderate clinical illness was observed in animals given group IV or V chronic-disease-associated isolates. 5J108- 111 appeared avirulent. These data suggest that C. burnetii isolates have a range of disease potentials and support a distinction in strain virulence between established genotypic groups, though isolates within the same genomic group cause similar pathologic responses. Heterologous protection was confirmed by cross vaccination and challenge with RSA493 and Q217. A marked non-specific suppression of lymphoproliferation was noted at 14 and 28 days post infection with RSA493; similar suppression was seen after infection with Q173 and Q212 but not 5J108-111. Proinflammatory cytokines IFN-? and TNF-? were produced during early C. burnetii infection, at which time anti-inflammatory cytokines TGF-? and IL-10 were repressed. A vaccine made from phase I C. burnetii was found to be completely protective against lethal infection in the guinea pig model, while vaccination with killed phase II organisms conferred only partial protection, preventing death and reducing but not precluding fever and respiratory illness. Protective vaccination significantly stimulated cell-mediated immunity and elicited increases in IFN-?, TNF-?, and IL-12p40 mRNA levels.Item Characterization of single-cycle flavivirus particles for use as a vaccine to prevent West Nile disease and to examine immune responses to flavivirus infection(2009-08-28) Douglas Gregory Widman; Peter W. Mason; Stanley M. Lemon; Nigel Bourne; Mark Heise; Gustavo ValbuenaWest Nile virus (WNV) is responsible for the largest outbreak of viral encephalitis in the history of North America, yet there are no vaccines available to prevent this disease. To address these needs we have developed RepliVAX WN, a single-cycle flavivirus (SCFV)-based vaccine to prevent West Nile disease. RepliVAX WN contains a C-deleted WNV genome, and is produced in trans-complementing cell lines that express WNV C. When used for vaccination, RepliVAX WN infects a single cell where the genome replicates and drives the production of highly antigenic subviral particles (SVPs) and NS1 without producing infectious virions. Thus, RepliVAX is expected to be highly potent yet exhibit a safety profile superior to traditional live-attenuated viral vaccines.\r\nHere we demonstrate that RepliVAX WN can be safely passaged in C-expressing cell lines and that this blind passage selected for mutations used to engineer a second-generation RepliVAX WN with an enhanced in vitro growth phenotype. When evaluated in mouse and hamster models of WN disease, this second-generation RepliVAX was safe, exhibited 100% protective efficacy, and induced significantly higher antibody levels than the parental virus. Furthermore, we observed that RepliVAX WN-induced antibody levels remain steadily at high levels for at least 6 months after vaccination of hamsters, and all animals were protected from lethal WNV challenge at this time. Evaluation in non-human primates indicated that one or two doses of RepliVAX WN was safe, induced WNV-specific antibody responses, and protected animals from WNV viremia. \r\nHaving demonstrated the usefulness of RepliVAX WN as a vaccine to prevent WN disease, we were interested in the immunological mechanisms underlying vaccine immunity. We observed that although RepliVAX WN vaccination induces high levels of interferon (IFN) alpha, the ability to respond to either type-I or type-II IFNs was not required for the development of activated B cells, IgG, IgM, or neutralizing antibody titers. Type-I IFN signaling did, however, play a role in viral gene expression, as in vivo imaging of animals inoculated with luciferase-expressing SCFVs revealed 1000-fold greater bioluminescence in the absence of a type-I IFN response. The affect of this IFN response on gene expression was dramatic, but short lived and did not appear to play a role in SCFV persistence, as SCFV gene expression was detectable for at least 18 days after SCFV inoculation. Taken together these results demonstrate the usefulness of SCFVs like RepliVAX WN as vaccines to prevent flavivirus disease, and tools with which to examine immune responses to viral infection.Item Evaluation of Arginine and Glutamine as Dietary Supplements to Enhance Edwardsiella ictaluri Vaccine Effectivness in Channel Catfish(2012-02-14) Pohlenz Castillo, CamiloRapid expansion of the aquaculture industry in recent decades has resulted in infectious diseases emerging as a major constraint to fish production, causing large economical losses worldwide. Therefore, prevention practices are indispensable for maintaining the industry's profitability and sustainability. Vaccination is a proven effective strategy for disease control in aquaculture; however, improvements in vaccine efficacy are still needed. Because amino acid supplementation not only enhances fish growth but also immune responses, a series of experiments were conducted to test the hypothesis that dietary supplementation of arginine and glutamine, two amino acids with immunomodulatory roles, may promote growth and increase the efficacy of vaccination against Edwardsiella ictaluri in channel catfish. An initial experiment demonstrated that dietary arginine supplementation at 2 and 4% of diet enhanced growth and feed efficiency of channel catfish. Dietary arginine deficiency diminished plasma levels of arginine, citrulline, ornithine, glutamine and glutamate, and impaired innate performance of macrophages and neutrophils. In a separate experiment, dietary glutamine supplementation failed to enhance growth responses; however, supplementation at 2% of diet had strong positive effects on intestinal histology and enterocyte migration rate. In addition, serine, asparagine, glycine and threonine were increased in plasma of fish fed the diet with glutamine at 2%. A third experiment revealed that activated macrophages utilized large quantities of glutamine in media and to a lesser extent arginine. These two amino acids also were the most utilized by proliferating lymphocytes. Supplementing media with these amino acids positively modulated phagocytosis and bactericidal capacity of macrophages, as well as increased the proliferation rate of lymphocytes. A final experiment indicated that dietary supplementation of arginine (4%) and glutamine (2%) optimized the nutritional and immunological status of channel catfish, and enhanced responses to E. ictaluri vaccination. At the same time, this supplementation ameliorated some short-term adverse effects of vaccination on growth. Higher specific antibody titers, better lymphocyte responsiveness and survival to the bacterium were seen in vaccinated fish fed arginine- and glutamine-supplemented diets. These results support an expanded role of dietary arginine and glutamine manipulation as a tool to improve growth and vaccine efficacy of channel catfish.Item Supplementation of Organic Acids and Algae Extracts in Aqua Feeds: Immunological Impacts(2013-12-02) Mendoza Rodriguez, Maria GTwo organic acids, polyhydroxybutyrate (PHB) and potassium diformate (KDF) have been researched to only a limited extent with aquatic species but have been shown to have various positive effects on terrestrial animals. Two algae extracts, carrageenan and alginic acid, also have been shown to elicit immunostimulation in some fish. Therefore, the present study was conducted with red drum (Sciaenops ocellatus) as a model marine species to study the effects of organic acids and algae extracts as feed supplements by evaluating several humoral immune responses. Two feeding trials, one of 7-week duration and the other of 3-week were conducted with disease-free juvenile red drum (average initial wt. 2.6?0.2 g and 78.2 ?0.2 g, respectively). Semipurified diets were formulated to be isocaloric and contain 40% crude protein. Experimental diets were produced by supplementing the basal diet with KDF at 0.6%, PHB at 2%, alginic acid at 1% or carrageenan at 0.5% by weight in place of cellulose. Fish were stocked into 110-L aquaria operated as a recirculating system with each diet assigned to three replicate aquaria containing either 15 fish (7-week trial) or 9 fish per aquarium (3-week trial). All fish were fed their respective diets at the same fixed percentage of body weight (initially 6% and gradually reduced to 4% as the fish grew). Body weight was monitored by collectively weighing fish from each aquarium every week. At the end of each feeding trial, weight gain and feed efficiency were significantly (P<0.0001) reduced in fish feed PHB compared to the basal diet and both algae extracts. There were no significant differences in condition indices such as hepatosomatic index (HSI) and intraperitoneal fat (IPF) ratio among fish fed the various diets. Lysozyme activity was significantly higher in fish fed alginic acid. The greatest phagocytic activity was found in fish fed the diet containing PHB. Total immunoglobulin level was higher in fish fed the diet supplemented with carrageenan. Goblet cell proliferation was greatest in the posterior end of the gastrointestinal tract but not different among dietary treatments. Organic acids and algae extracts evaluated in this study produced variable immunological responses in red drum with carrageenan showing the greatest potential as an immunostimulant.