Local cellular immune response plays a key role in protecting chickens against hepatitis-hydropericardium syndrome (HHS) by vaccination with a recombinant fowl adenovirus (FAdV) chimeric fiber protein

• DOI: 10.3389/fimmu.2022.1026233
• Publication Date: 2022-10-28T13:33:22Z
• Authors: Carlotta De Luca; Anna Schachner; Sarah Heidl; Michael Hess; Dieter Liebhart; Taniya Mitra
• Keywords: 0301 basic medicine; Immunity, Cellular; Recombinant Fusion Proteins; Adenoviridae Infections; Aviadenovirus; Immunology; Vaccination; cellular immunity; RC581-607; Pericardial Effusion; chimeric fiber vaccine; Adenoviridae; Hepatitis; 3. Good health; FAdV-4; hepatitis-hydropericardium syndrome; 03 medical and health sciences; humoral immunity; fowl adenovirus; Animals; Immunologic diseases. Allergy; Chickens; Poultry Diseases

Fowl adenovirus (FAdV)-induced diseases hepatitis-hydropericardium syndrome (HHS) and inclusion body hepatitis (IBH) have been affecting the poultry industry with increasing severity in last two decades. Recently, a subunit vaccine based on chimeric fiber protein epitopes from different fowl serotypes (named crecFib-4/11) has shown to confer simultaneous protection against both HHS IBH. However, underlying immune mechanisms chickens are still enigmatic, especially because of frequently absent neutralizing response despite high levels protection. In this study, we investigated kinetics humoral cellular responses specific pathogen-free after vaccination crecFib-4/11 and/or challenge HHS-causing strain, systemic level, as well locally target lymphoid organs. The was assessed via enzyme-linked immunosorbent assay (ELISA) virus neutralization test serum, while determined by phenotyping using flow cytometry. Although induced serum antibodies, confirmed ELISA, such antibodies exhibited no pre-challenge activity FAdV-4. Nevertheless, immunized birds experienced significant B cell increase liver upon challenge, remaining throughout experiment. Furthermore, stimulated proliferation cytotoxic T lymphocytes, earlier circulation blood compared control subsequent spleen. Overall, these findings imply that relies prominent local organs, instead circulating antibodies.