Immune responses against rHaa86 in cross-bred cattle

Area of Science:

• Veterinary Immunology
• Parasitology
• Vaccine Development

Background:

• Tick vaccines are crucial for integrated pest management and controlling tick-borne diseases.
• Understanding immune responses to recombinant tick antigens is key for effective vaccine design.
• rHaa86, a homologue of Bm86, is a target antigen for tick vaccine development.

Purpose of the Study:

• To determine the humoral and cellular immune responses in calves immunized with rHaa86.
• To evaluate the antibody subclasses (IgG1 vs. IgG2) and interferon-gamma (IFN-γ) production.
• To elucidate the immune mechanism underlying protection against ticks.

Main Methods:

• Experimental crossbred calves were immunized with rHaa86.
• Humoral antibody responses were measured using an optimized ELISA.
• Interferon-gamma (IFN-γ) expression was evaluated in vitro using blood cell cultures stimulated with rHaa86, with results expressed as stimulation indices (SI).

Main Results:

• Strong humoral antibody responses (dominated by IgG1) were observed post-vaccination, peaking after the second booster and sustained for 120 days.
• Interferon-gamma (IFN-γ) levels did not reach significant levels, despite plotting standard curves for bovine IFN-γ.
• The dominance of IgG1 over IgG2 and the lack of significant IFN-γ response suggested a Th2-biased immune response.

Conclusions:

• The rHaa86 vaccine elicits a robust antibody response in calves, primarily of the IgG1 subclass.
• The immune response appears to be Th2-polarized, suggesting antibody-mediated protection against ticks.
• This study provides insights into the immunological mechanisms of rHaa86-based tick vaccines.