Beschreibung:
<jats:title>Abstract</jats:title><jats:p>Increasing antibiotic resistance and ever stricter control on antibiotic use are a driving force to develop alternatives to antibiotics. One such strategy is the use of multifunctional Host Defense Peptides. Here we examined the protective effect of prophylactic treatment with the D analog of chicken cathelicidin-2 (D-CATH-2) against a respiratory <jats:italic>E. coli</jats:italic> infection. Chickens were treated with D-CATH-2 <jats:italic>in ovo</jats:italic> at day 18 of embryonic development or intramuscularly at days 1 and 4 after hatch. At 7 days of age, birds were challenged intratracheally with avian pathogenic <jats:italic>E. coli</jats:italic>. Protection was evaluated by recording mortality, morbidity (Mean Lesion Score) and bacterial swabs of air sacs at 7 days post-infection. <jats:italic>In ovo</jats:italic> D-CATH-2 treatment significantly reduced morbidity (63%) and respiratory bacterial load (>90%), while intramuscular treatment was less effective. D-CATH-2 increased the percentage of peripheral blood lymphocytes and heterophils by both administration routes. <jats:italic>E. coli</jats:italic> specific IgM levels were lower in <jats:italic>in ovo</jats:italic> treated animals compared to intramuscular D-CATH-2 treatment. In short, <jats:italic>in ovo</jats:italic> treatment with the Host Defense Peptide derived D-CATH-2 can partially protect chickens from <jats:italic>E. coli</jats:italic> infection, making this peptide an interesting starting point to develop alternatives to antibiotics for use in the poultry sector.</jats:p>