Delayed-type hypersensitivity reaction induced in broilers via trachea inoculation of killed Staphylococcus aureus

Area of Science:

• Immunology
• Veterinary Medicine
• Cellular Biology

Background:

• Delayed-type hypersensitivity (DTH) is a crucial cell-mediated immune response.
• Assessing DTH in poultry is important for understanding immune responses to bacterial antigens.
• Staphylococcus aureus is a common pathogen affecting livestock.

Purpose of the Study:

• To investigate if multiple intratracheal inoculations of killed Staphylococcus aureus antigen can induce a DTH reaction in chickens.
• To compare the DTH response induced by intratracheal inoculation with the traditional subcutaneous injection method.
• To evaluate DTH using delayed footpad reaction, monocyte/macrophage migration inhibition, and histopathological analysis.

Main Methods:

• Broiler chickens were sensitized via subcutaneous injection or intratracheal inoculation with killed S. aureus antigen at 2, 3, and 4 weeks of age.
• Delayed footpad reaction (DFR) was assessed by measuring footpad thickness post-challenge.
• Monocyte/macrophage migration inhibition tests and histopathological examinations were performed.

Main Results:

• Both subcutaneous and intratracheal sensitization induced significant DTH reactions, with peak responses at 24 hours post-challenge.
• Subcutaneous sensitization inhibited monocyte/macrophage migration, but intratracheal sensitization did not.
• Histological analysis revealed mononuclear cell infiltration in the footpads of both sensitized groups.

Conclusions:

• Multiple intratracheal inoculations are effective in inducing a cell-mediated DTH reaction in chickens.
• Intratracheal sensitization provides an alternative route for inducing DTH responses to killed S. aureus antigen.
• The study highlights the utility of DTH assessment in evaluating poultry immune responses.