Developmentally regulated expression of a Haemonchus contortus surface antigen

Area of Science:

• Veterinary Parasitology
• Molecular Biology
• Immunology

Background:

• Haemonchus contortus is a significant gastrointestinal nematode parasite of livestock.
• Understanding parasite antigen expression is crucial for vaccine development.
• Antibody-secreting cells (ASCs) can be used as probes to identify parasite antigens recognized by the host immune system.

Purpose of the Study:

• To identify and characterize Haemonchus contortus antigens expressed across different life cycle stages.
• To investigate the relationship between a major 3rd-stage larval antigen and molecules expressed in earlier developmental stages.

Main Methods:

• Screening of all Haemonchus contortus life cycle stages using antibody-secreting cell (ASC) probes from immune sheep.
• Characterization of antigen molecular weights using SDS-PAGE and Western blotting.
• Generation of antisera against purified antigens and elution of antibodies from specific molecular weight regions.

Main Results:

• A 70-90 kDa antigen was predominantly expressed in 3rd-stage larvae (L3).
• A 28-31 kDa molecule was recognized by ASC probes in earlier larval stages (L2).
• Antisera against the 70-90 kDa antigen reacted with the 28-31 kDa molecule in L2, indicating a shared antigenic determinant.

Conclusions:

• The 70-90 kDa surface antigen of H. contortus L3 larvae is synthesized as a lower molecular weight precursor (28-31 kDa) in earlier larval stages.
• This precursor molecule is assembled into a higher molecular weight complex via non-reducible covalent bonds.
• This finding provides insights into the post-translational modification and assembly of parasite antigens, relevant for targeted intervention strategies.