Reproduction

Experimental contraceptive vaccine may help address overpopulation

By Modern Equine Vet News Staff

Researchers from Purdue University have designed a vaccine to help address overpopulation among wild and feral mammals (Vaccine 2026;72:128071).

The vaccine, based on the IZUMO1 mammalian sperm protein, induces a robust and long-lasting immune response and infertility among female mammals, according to its designers, Harm HogenEsch, DVM, PhD, DACVP, distinguished professor of immunopathology in Purdue’s College of Veterinary Medicine, in West Lafayette, Ind., and Raluca Ostafe, PhD, director of Purdue’s Molecular Evolution Protein Engineering and Production Facility.

There are currently 2 types of contraceptive vaccines—both based on self-proteins—that require a breakdown of immune tolerance. Dr. HogenEsch said these vaccines have several drawbacks:

They reduce fertility, but the effect is not long-lasting

• They are associated with injection-site reactions ranging from swelling to abscesses
• 1 vaccine targets hormones that could cause behavioral changes
• 1 vaccine is prepared from sources that are at risk of supply-chain interruptions

Dr. HogenEsch said the Purdue experimental contraceptive vaccine addresses these limitations. “It is based on a male sperm protein that the female’s immune system recognizes as foreign,” he said. “It works exclusively by inhibiting the fusion of a sperm cell and the oocyte. The vaccine consists of a well-defined peptide produced in mammalian cells and an effective and safe adjuvant.”

Validation and next development steps
The successful production and purification of the Purdue vaccine were validated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and western blot analysis of the proteins. The vaccine’s ability to reduce fertility was observed by injecting different formulations into experimental groups; vaccination reduced overall fertility by 59% to 67%, but more research is planned before submitting it for approval.

“We will develop it into a single-dose, controlled-release formulation. This is critical to the use of the vaccine in wildlife, where giving a second dose to an animal is often very difficult, if not impossible. A vaccine that induces long-lasting infertility with a single injection will greatly facilitate the utility of the vaccine,” he said. “We are also working to further optimize the design of the vaccine to allow delivery via darts and oral delivery.”

The researchers have completed the first year of a 3-year project funded by the Bureau of Land Management to test the vaccine’s effects on horses. If successful, this could have an application in wild horse management.

Humane World for Animals, formerly the Humane Society of the United States, and the Elinor Patterson Baker Trust provided financial support for HogenEsch’s research.

The Purdue Innovates Office of Technology Commercialization has applied for a patent to protect the intellectual property. Industry partners interested in developing or commercializing it should contact Joe Kasper at jrkasper@prf.org about track code 70624. MEV