Differences in the expression of antimicrobial peptides in vivo have been proposed as underlying factors influencing susceptibility to infection. In this context, the role of avian b-defensins in inhibiting avian influenza infections is a study object in an ongoing collaboration with the Zoonotic Ecology and Epidemiology group at Lnu. In this report, an attempt to synthesize two variants of the peptide Anas Platyrhynchos AvBD-8, using Fmoc-based SPPS, is described. The length of AvBD-8 (43 aa) necessitated peptide synthesis in two segments to subsequently be ligated using native chemical ligation. The first component of a 19 aa segment was thus a Dbz-linker, which would allow to ligate this end with a second segment (24 aa). Halfway through the synthesis of this larger segment the batch was split into two pots, allowing the synthesis of two segments differing by one single amino acid (R for W). The composition of these segments were: Dbz-HDTSCTGGAQKCQVANNPA (Dbz-segment), SVVTRCCPIGQKCWGFARTNPPPC(boc) (W-segment), and  SVVTRCCPIGQKCRGFARTNPPPC(boc) (R-segment). Crude product yields were 284,5 mg; 67,6% (Dbz-segment), 137,6 mg; 52,3% (W-segment), and 166,3 mg; 64,2%. Preliminary mass spectrometric analysis on the crude products did not indicate the presence of the desired segments in major mass peaks. Further product purification is necessary in order to allow definite conclusions, but it appears as if the synthesis has not worked. Possible explanations are either impure or degraded reactant(-s), folding or shielding effects of the growing peptide chain at some point inhibiting synthesis, or experimental errors during one or more of the many steps involved in the synthesis.

Host defense peptides (HDPs) are a large group of small positively charged peptides that play an important role in innate immunity. Their role is more critical at early ages when other components of the immune system have not fully developed. There are three classes of avian HDPs: avian beta defensins (AvBDs), cathelicidins (Cath) and liver-expressed antimicrobial peptide 2 (LEAP-2). The objective was to compare expression of HDPs in male turkey poults at day of hatch (D0), D7, D14, D21 and D28 from the thymus, spleen, bursa, duodenum, jejunum and ileum. The expression of AvBD1, AvBD2, AvBD8, AvBD9, AvBD10, AvBD13, Cath2, Cath3 and LEAP-2 was measured using qPCR (n=6 birds/tissue/age). Data were analyzed by one-way ANOVA and Tukey's test, and significance considered at P ≤ 0.05. AvBDs and Caths exhibited greater expression in immune organs than intestinal tissues, with the greatest expression of AvBDs observed in the spleen. The intestinal tissues showed very low expression of AvBDs except for AvBD10 at D0. Similar to AvBDs, Caths expression in the immune organs was greater than the intestinal tissues with the spleen having the greatest expression among immune organs. Conversely, LEAP-2 showed greater expression in the intestinal tissues than in the immune tissues, which showed very low LEAP-2 expression unlike other HDPs. Understanding the differential expression of HDPs could reveal the innate immune status of poults, and may subsequently allow improvement of their health through appropriate mitigation strategies. / Master of Science