AARHUS UNIVERSITY Different serum levels of mannose‐ binding lectin influence the immune responses in chickens after infectious bronchitis infection by Rikke M. Kjærup Immunology and Microbiology, Department of Animal Science Faculty of Science and Technology Aarhus University Rikke M. Kjærup April 2014 1 AARHUS UNIVERSITY Mannose‐binding lectin (MBL) Collectin MBL‐A and MBL‐C Characterised in several species incl. humans, chickens, pigs, cattle, mice, fish Only one form of the protein in humans (MBL‐C) and chickens (MBL) Chicken MBL located on chromosome 6 Mainly expressed in the liver Also in thymus, air sac, larynx and infundibulum MBL serum levels vary Human: diminutive ‐ 10 µg/mL Chicken: 0.4 ‐ 37.8 µg/mL Pig: diminutive ‐ 43.3 µg/mL Rikke M. Kjærup April 2014 2 AARHUS UNIVERSITY MBL genetic polymorphisms Coding region: Human MBL2, porcine MBL1 and bovine MBL1 and MBL2 Promoter region: Human MBL2, porcine MBL2 Associations to severity of various infectious conditions In chickens: association between MBL serum levels and disease severity: Infectious bronchitis virus Pasteurella multocida Ascaridia galli Rikke M. Kjærup April 2014 3 AARHUS UNIVERSITY MBL function Weak acute phase protein (2 – 3 fold increase) 2 main functions: Opsonin facilitating phagocytosis Initiator of the lectin pathway in the complement activation Also: Coagulation and clearance of apoptotic cells Regulation of inflammation and the adaptive response Rikke M. Kjærup April 2014 4 AARHUS UNIVERSITY Infectious bronchitis virus (IBV) Coronavirus specific for chickens Single‐stranded positive RNA genome Envelope: S, M and E proteins Viral RNA bound by the N protein April 2014 5 AARHUS UNIVERSITY Pathogenesis Respiratory tract Clinical signs: gasping, coughing, tracheal rales, depression, nasal/ocular discharge Non‐respiratory epithelial cells Inflammation of the kidney and poor egg production and quality Different strains of IBV Morbidity and mortality depend on the virus strain Spread by: Air between flocks and chicks Faecal shedding Rikke M. Kjærup April 2014 6 AARHUS UNIVERSITY Experimental layout Day 0 Infection 7 14 21 End Two treatment groups: Non‐infected Infected Each treatment group: 16 L10L and 16 L10H (3 weeks of age at beginning) Rikke M. Kjærup April 2014 7 AARHUS UNIVERSITY Viral load H - infected * P<0.03 L - infected 8,0E-04 * 7,0E-04 6,0E-04 Viral load 5,0E-04 4,0E-04 3,0E-04 2,0E-04 1,0E-04 0,0E+00 0 1 2 3 4 5 Day PI 6 7 8 14 Rikke M. Kjærup 21 April 2014 8 AARHUS UNIVERSITY MBL serum concentrations H - Control 45 H - Infected L - Control L - Infected MBL serum concentration µg / mL 40 35 30 25 20 15 10 5 0 0 3 6 7 14 21 Day PI Rikke M. Kjærup April 2014 9 AARHUS UNIVERSITY Relative MBL expression Liver: Lung: P<0.02 P<0.02 Rikke M. Kjærup April 2014 10 AARHUS UNIVERSITY Effect of sublines and treatments on T cell subsets * P<0.05 ** P<0.01 Rikke M. Kjærup H - control H - infected L - control L - infected April 2014 11 AARHUS UNIVERSITY Conclusion: Lower viral load in L10H than L10L following IBV infection ‐> L10H are less severely affected by the infection MBL was expressed in the lungs of healthy chickens MBL expression in the lung and the liver was upregulated at days 3 and 7 after the IBV infection MBL may play a role in the regulation of the cellular immune response after IBV infection Rikke M. Kjærup April 2014 12
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