Antigen-specific lymphocyte proliferative responses in vaccinated and Hypoderma lineatum-infested calves

Area of Science:

• Veterinary immunology
• Parasitology
• Bovine immunology

Background:

• Cattle develop immune responses to common cattle grub (Hypoderma lineatum) proteins.
• Cellular immunity, specifically delayed-type hypersensitivity, is observed.
• Hypodermin A (HyA) is a key protein from first-instar H. lineatum larvae.

Purpose of the Study:

• To investigate the antigen-specific bovine lymphocyte response to hypodermin A (HyA).
• To monitor the kinetic development of cellular immune responses during vaccination and infestation.
• To correlate lymphocyte proliferation with larval mortality.

Main Methods:

• Calves were vaccinated with native or denatured HyA.
• Vaccinated calves were challenge-infested with H. lineatum.
• Antigen-specific lymphocyte proliferation was measured during vaccination and infestation.
• Immune responses were assessed 6 months post-infestation with a booster injection.

Main Results:

• HyA-specific immune responses were variable and weak during vaccination and infestation.
• No correlation was found between lymphocyte proliferation and larval mortality.
• Intense HyA-specific lymphocyte responses were observed 6 months after infestation in some calves.
• A booster injection of HyA heightened these delayed responses.

Conclusions:

• Bovine lymphocyte responses to HyA are weak and variable during active H. lineatum infestation.
• A significant, heightened HyA-specific lymphocyte response develops months after parasite clearance.
• This delayed response suggests a potential for long-term immune memory to H. lineatum antigens.