Researching immunocontraceptive vaccines with mares (Equus caballus) as both a target and model for African elephant (Loxodonta africana) cows: A review.

The research article discusses using mares as a test platform for immunocontraceptive vaccines aimed at controlling the population of African elephants. In the study, various immunocontraceptive vaccines were deployed and the outcomes were observed, eventually leading to more informed and improved decisions regarding elephant population control.

Experimental Process

• The researchers used domestic horse mares as a platform for testing the immunocontraceptive vaccines. This provided a convenient and effective means of gathering clinical and lab data.
• Experiments utilized anti-GnRH and zona pellucida (ZP) vaccines. These types of vaccines are known for their potential contraceptive properties.
• The GnRH vaccine, referred to as Improvac, was initially used and its effectiveness, safety, and reversibility was confirmed via methods like reproductive tract ultrasonography, serum antibody titres, and progesterone concentrations monitoring.
• Further experiments were conducted using a porcine ZP (pZP) vaccine, which was monitored with the same methods mentioned above.

Findings

• The study found that the GnRH vaccine demonstrated contraceptiveness in mares, and these results were used to help design strategies for using the vaccine in free-ranging African elephants.
• Subsequent experiments using the pZP vaccine also showed contraceptive efficacy, though most mares exhibited ovarian inactivity after treatment.
• This unexpected inactivity led to further analysis and the discovery that high levels of cytotoxic (CD8+) T-cells were present, correlating negatively with serum ovarian steroid and anti-Müllerian hormone (AMH) levels, hence suggesting their role in the observed ovarian response.
• Injection-site lesions were a notable concern, tentatively linked to Freund’s adjuvants used in the vaccines.

Improvements and Future Work

• The researchers replaced Freund’s adjuvants with non-Freund’s adjuvants in a reZP vaccine. The results were comparable to the previous applications, but without causing any adverse reactions at the injection site.
• The application of the anti-ZP vaccine indicates potential for AMH as an indicator for monitoring ovarian function.
• The study contributes to improving vaccine formulation and protocols for more effective and safe elephant population management using immunocontraceptive vaccines.