Single shot delivery for long-term contraception in animals

Scientists have developed a nonsurgical method to deliver long-term contraception to both male and female animals with a single shot, and it could be an alternative to spaying and neutering feral animals.
Researchers from California Institute of Technology in US used an adeno-associated virus (AAV) - a small, harmless virus that is unable to replicate on its own - to deliver a gene that directs muscle cells to produce an antibody that neutralises gonadotropin-releasing hormone (GnRH) in mice.
GnRH is what the researchers refer to as a "master regulator of reproduction" in vertebrates - it stimulates the release of two hormones from the pituitary that promote the formation of eggs, sperm, and sex steroids. Without it, an animal is rendered infertile.

In the past, other teams have tried neutralising GnRH through vaccination. However, the loss of fertility that was seen in those cases was often temporary.
In the new study, researchers saw that the mice - both male and female - were unable to conceive after about two months, and the majority remained infertile for the remainder of their lives.
"Inhibiting GnRH is an ideal way to inhibit fertility and behaviours caused by sex steroids, such as aggression and territoriality," said Bruce Hay, professor at Caltech.

His team also shows that female mice can be rendered infertile using a different antibody that targets a binding site for sperm on the egg.

"This target is ideal when you want to inhibit fertility but want to leave the individual otherwise completely normal in terms of reproductive behaviours and hormonal cycling," he said.
Hay's team has dubbed the new approach "vectored contraception" and said that there are many other proteins that are thought to be important for reproduction that might also be targeted by this technique.
"Spaying and neutering of animals to control fertility, unwanted behaviour, and population numbers of feral animals is costly and time consuming, and therefore often doesn't happen," said Hay.
"There is a strong desire in many parts of the world for quick, nonsurgical approaches to inhibiting fertility. We think vectored contraception provides such an approach," he said.

The study was published in the journal Current Biology.