Effect of concurrent intratracheal lipopolysaccharide and human serum albumin challenge on primary and secondary antibody responses in poultry.

Activation of the innate immune system by pathogen-associated molecular patterns (PAMPs) may direct specific immune responses and as a consequence probably significantly affect vaccination. Previously, we described modulation of specific antibody responses to systemically administered model antigens by intravenously (i.v.) as well as intratracheally (i.t.) administered PAMP such as the endotoxin lipopolysaccharide (LPS). In this study effects of various doses of i.t.-administered LPS on primary and secondary specific total and individual isotype (IgM, IgG and IgA)-specific antibody responses of chickens simultaneously i.t. challenged with various doses of human serum albumin (HuSA) were determined. i.t.-administered LPS enhanced primary and secondary HuSA-specific total and isotype-specific antibody titers depending on the dose of LPS and the dose of simultaneously administered HuSA. i.t.-administered HuSA enhanced primary and secondary total antibody responses to 'environmental' LPS as shown in birds receiving the zero i.t. LPS treatment, which also depended on dose of HuSA. HuSA administration decreased antibody responses to high doses of LPS. Body weight gain as a measurement of an acute phase cachectin response to LPS was affected by a HuSA by LPS interaction, indicating that simultaneously administered higher doses of HuSA decreased LPS-induced cachectin responses of the birds. Our results suggest a complex interaction of innate and specific immune system activating airborne antigens, which may have significant consequences for vaccination and husbandry management procedures.