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Mpact of early nutrition on the development of lung immunity in the piglet

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Title: Mpact of early nutrition on the development of lung immunity in the piglet
Author(s): Cope Thorum, Shannon C.
Advisor(s): Donovan, Sharon M.
Department / Program: Nutritional Sciences
Discipline: Nutritional Sciences
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: M.S.
Genre: Thesis
Subject(s): Early nutrition Lung immunity Piglet development
Abstract: Abstract This thesis covers a variety of topics and analyses related to early nutrition on the impact it has on the development of lung immunity in the piglet. In the first section, an introduction is given. In short, neonates are susceptible to infection early in life, especially respiratory infections (Murphy et al. 2008). Respiratory infections are a major cause of morbidity and mortality in infants and children world-wide. The immune system exists to protect the host against infection and to help the neonate respond appropriately to critical transition periods of life, namely birth and weaning where the infant is exposed to a variety of new environmental and food antigens. Deficiencies of the immune system, both innate and adaptive immunity contribute to impaired host defense (Marodi and Notarangelo 2007) which can lead to increased susceptibility to infection. Exposure to dietary antigens influences the rate of maturation of the immune system (Kelly and Coutts 2000) and can even help provide a protective effect against infection. Breast milk is the optimal form of nutrition and is thought to help the immune system develop by providing signals to the immune system (Kelly and Coutts 2000), contributing bioactive components and stimulating the release of cytokines in peripheral blood mononuclear cells (PBMC) (Bessler et al. 1996) thus decreasing the risk of pneumonia (Chantry et al. 2006), upper respiratory, lower respiratory and gastrointestinal infections (Duijts et al. 2010). Despite the benefits of breast milk, only about 13% of infants are exclusively breastfed by 6 months of age (CDC 2010), therefore, increased understanding of lung immune characteristics and how they differ between breastfed and formula infants is necessitated. The next section of the thesis looks at developmental differences in lung, mediastinal lymph nodes, and thoracic lymph nodes in breastfed compared to formula-fed piglets. In this study, colostrum-fed newborn piglets were either fed medicated sow milk replacer formula beginning at 48 hours of life (n=11) or remained with the sow (n=12) throughout the duration of the study. On d7 and d21 postpartum, approximately half of the piglets in each group were euthanized and blood and tissue samples were collected. Immune cells in the lungs, MSLN and TLN were analyzed through a variety of techniques. T lymphocyte subpopulations were identified using flow cytometry, cytokine mRNA expression was evaluated via RT-PCR, and total IgG, IgM, and IgA concentrations in serum were analyzed using enzyme linked immunoabsorbant assay (ELISA). Both dietary (SR vs. FF) and developmental effects on immunological development were observed. Through flow cytometry, it was found that NK cells were affected by diet in TLN, but not in PBMC or MSLN. However, an effect of day (e.g. development) was seen in PBMC NK cells. CD4+CD8+ T cell ratios were not different between FF and SR piglets in PBMC; however, diet affected MSLN at d21 and TLN at d7. Expression of CD4+CD8+ double positive T cells in PBMC were affected by day, while diet effects were seen in TLN on d7 and MSLN on d21. mRNA expression was investigated in whole tissue samples from the lung, TLN, and MSLN. Diet also affected the mRNA expression of IL-1β and TNF-α in TLN, dectin, IFN-α, and TGF-β2, in MSLN and IFN-β in lung tissue in which FF animals had higher mRNA expression than the SR counterpart. In addition, the expression of TLN IL-12 and dectin and MSLN IFN-α decreased over time while lung IL-6, TGF-β1, INF-α, and TNF-α increased over time. Turning to systemic immunity, serum IgG concentrations were lower in the SR piglets than FF piglets (p<0.05), and IgG levels in d7 animals were higher than at d14 and d21 (p<0.05). Serum IgM concentrations were not significantly different in SR piglets compared to FF piglets nor did the concentrations exhibit developmental changes. Serum IgA levels were lower in the SR piglets when compared to the FF piglets (p<0.05), and IgA levels in d7 animals were higher than on d14 and d21 (P<0.05). The findings of this study have established a set of baseline measurements that establish the developmental changes in immune cells populations and cytokine expression in bronchial associated lymph tissues. Furthermore, these data demonstrated that differences exist between SR and FF piglets and provide a framework for future respiratory challenge studies to continue to pinpoint diet/immunological factors that increase the neonate’s ability to resist respiratory infections and recover more quickly from pathogenic invasion. This developmental study also established a foundation of normative changes over time for future studies to probe effectiveness of various formula components on mucosal lung immune development. The next section of the thesis discusses one component, β-glucan, and the effect it has on mucosal lung immune development. In this study, piglets (n=5-6/group) were fed formula containing 0 (control), 5 (WGP5), 50 (WGP50), or 250 (WGP250) mg/L formula. Half of the piglets in each treatment were vaccinated (FV) by i.m. injection against influenza (Fluzone™, Sanofi Pasteur, Swiftwater, PA) on d7 and received a booster on d14. Piglets were euthanized on d7 and d21. Weight gain and formula intake were unaffected by diet or vaccination. Fluzone-specific serum IgG concentrations was measured by ELISA. FV piglets had higher (p<0.0001) fluzone-specific IgG titer at d14 and 21 than non-V piglets independent of diet. Vaccination response were unaffected by oral WGP supplementation. TNF-α, dectin, IL-1α, -2, -4, and -12 mRNA expression in lung were unaffected by age or dietary WGP. Lung TGFβ-1 mRNA expression was greater (p<0.05) at d21 than d7, and lung TGFβ-2 mRNA was lower (p<0.01) in all WGP diets compared to control. TNF-α, dectin, TGFβ-1, IL-2, -4, -6, or -12 mRNA in mediastinal lymph nodes (MSLN) were unaffected by age or dietary WGP. In MSLN, TGFβ-2 mRNA expression increased from d7 to d21 (p<0.05). TNF-α, TGFβ-1, TGFβ-2, IL-4, -6, or -12 mRNA in thorasic lymph nodes (TLN) were unaffected by age or dietary WGP. Dectin mRNA expression in TLN was lower at d21 compared to d7 (p<0.05). T-cell phenotypes were examined in MSLN and TLN by flow cytometry. In MSLN and TLN, CD4+ T-cells decreased, while CD8+ T-cells increased between d7 and d21 piglets (p<0.001), but these developmental patterns were unaffected by dietary WGP. Total serum IgG, IgM and IgA concentrations were also analyzed via ELISA. Total serum IgG, IgM and IgA were unaffected by WGP but followed typical developmental patterns. Thus, with the exception of reducing TGFβ-2 mRNA in lung, dietary WGP did not affect cytokine expression, T-cell phenotypes or vaccination response in piglets. The thesis comes to a close with a discussion of overall conclusions and future directions for this work.
Issue Date: 2011-05-25
URI: http://hdl.handle.net/2142/24059
Rights Information: Copyright 2011 Shannon C. Cope Thorum
Date Available in IDEALS: 2011-05-25
Date Deposited: 2011-05
 

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