IgG4/7 responses correlate with contraception in mares vaccinated with SpayVac

Theriogenology. 2018 Nov;121:168-174. doi: 10.1016/j.theriogenology.2018.08.015. Epub 2018 Aug 16.


SpayVac® is an immunocontraceptive vaccine based on porcine zona pellucida (pZP) antigens and uses a patented liposome formulation (VacciMax or DepoVax®). It has delivered single-dose, long-lasting (4-10 years) immunocontraception in several species. Previous studies have demonstrated a positive correlation between levels of pZP antibodies produced and contraceptive effect; however, individual mares that were consistently infertile did not necessarily have the highest antibody titers. The objective of this study was to identify potential differences in specific immunoglobulin G (IgG) isotype responses among mares treated with SpayVac (VacciMax formulation) to improve our understanding of vaccine efficacy and potential management applications. We analyzed serum samples collected 1, 2 and 4 years post-vaccination from mares in another study that were continuously infertile or had foaled at least once during the 4-year period (n = 14 each). Additional samples from the continuously infertile mares were collected 5 years post-vaccination. A fluorescent bead-based assay was used to distinguish IgG isotype responses against pZP. IgG1 antibodies were generally higher in the infertile compared to the fertile mares, but only IgG4/7 antibodies were significantly higher in infertile mares during years 1 and 2 post-vaccination (p < 0.05). Interestingly, IgG4/7 isotype levels were significantly higher during year 5 compared to year 4 in the continuously infertile mares (p < 0.02). SpayVac's ability to preferentially stimulate IgG4/7 antibodies may contribute to its long-term immunocontraceptive efficacy, and measuring IgG4/7 isotypes may help differentiate effectively contracepted mares from those that may need additional vaccination.

Keywords: IgG isotypes; Immunocontraception; Mares; SpayVac(®).

Publication types

  • Clinical Trial, Veterinary

MeSH terms

  • Animals
  • Contraception, Immunologic / methods
  • Contraception, Immunologic / veterinary*
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Fertility
  • Horses / physiology*
  • Immunoglobulin G / metabolism
  • Pregnancy
  • Random Allocation


  • Immunoglobulin G