Serum antibody immunoreactivity and safety of native porcine and recombinant zona pellucida vaccines formulated with a non-Freund’s adjuvant in horses.

This research explores alternatives to traditionally used adjuvants in vaccines for horses, specifically looking at native porcine zona pellucida (pZP) and recombinant ZP (reZP) vaccines. The study found that a newly tested reZP vaccine formulated with an alternative adjuvant produced similar immune responses to traditional pZP vaccines with limited side-effects, marking the first time these results have been achieved in mares.

Objective of the Research

The main objective of the research was to find an alternative to the Freund’s adjuvants that are commonly used in native porcine zona pellucida (pZP) vaccines due to limitations associated with their commercial and regulatory use. The focus was on developing effective recombinant ZP (reZP) vaccines and testing adjuvant formulations that could evoke similar immune response as the traditionally used pZP vaccines.

Methodology

• The researchers conducted a two-part study involving 15 geldings and 31 mares. In the initial stage, numerous alternative adjuvant formulations such as Addavax, Quil A, Quil A and Poly (I:C), Pet Gel A, and Pet Gel A and Poly (I:C) were tested on geldings. The horses’ anti-pZP antibody response, injection site reactions, rectal temperature, and heart and respiratory rates were monitored post-treatment.
• In the second part of the study, the researchers administered pZP, reZP, and a combination of both, prepared in Pet Gel A and Poly (I:C) to 31 mares. Post inoculation, they monitored the serum anti-pZP and -reZP antibody responses. They also assessed the safety of the treatment by inspecting the injection sites and measuring rectal temperature for a week post-treatment.

Results

• The researchers found that Pet Gel A and Pet Gel A and Poly (I:C) elicited suitable anti-pZP antibody responses in the first phase of the experiment.
• In the second phase, all treatment groups (pZP, reZP, and the combination) elicited a significant antibody response compared to an adjuvant control group.
• The temporal changes in both anti-pZP and -reZP antibody titres in all the groups were similar to patterns reported in other species vaccinated with pZP formulated with Freund’s adjuvants.
• There was no significant difference in anti-pZP antibody titres between the groups treated with pZP and reZP.
• The side effects observed were mild and temporary, suggesting the alternative was safe for use.

Conclusions

The researchers concluded that a reZP vaccine formulated with non-Freund’s adjuvants can elicit a similar immune response to native pZP vaccination. This is the first time this effect has been found in mares, which indicates a possible alternative to the traditionally used Freund’s adjuvants in pZP vaccines for horses, overcoming commercial and regulatory constraints.