Mycobacterium avium: Is It an Essential Ingredient for a Single-Injection Immunocontraceptive Vaccine?

Abstract

Greater demand for non-lethal means of alleviating human-wildlife conflict has led to an interest in contraception as a wildlife management tool. The development of a single-injection Gonadotropin-Releasing Hormone (GnRH) contraceptive vaccine by the USDA National Wildlife Research Center reduces logistical limitations and the cost of using a vaccine that requires 2 injections. This study assesses the efficacy of different GnRH-KLH (keyhole limpet hemocyanin) vaccine designs. Forty-two captive female black-tailed deer were divided into 3 groups. A control group was injected with saline solution, and 2 treated groups were given either GonaCon™, a GnRH vaccine paired with AdjuVac™ (an adjuvant containing 175 µg of killed Mycobacterium avium), or GnRH vaccine without AdjuVac™ (instead substituting DEAE-dextran/oil (DD) as the adjuvant). Pregnancy rates in deer treated with GonaCon™ were significantly reduced as compared to saline controls (P = 0.006). There was no significant difference between GnRH-DD compared to saline (P = 0.297). Significant difference was found between GonaCon™ and GnRH-DD (P = 0.055). Vaccinated does that remained fertile received booster injections according to treatment group and were administered either GonaCon™ containing 87 µg M. avium or GnRH-KLH conjugate bound to DEAE-dextran. Deer that received booster injections regardless of the adjuvant were 100% contracepted for 1 year. Six out of 10 deer that received a prime injection of GonaCon™ remained 100% contracepted for 3 years, suggesting that the killed M. avium in the adjuvant is essential for the success of GonaCon™ as a single-injection GnRH vaccine.