Key to infertility found?

Hong Kong scientists said Friday they have discovered a molecule that binds human sperm to an egg, in a breakthrough which offers new hope for infertile couples.

The study by researchers at the University of Hong Kong (HKU) found a key molecule on the coating of the human egg, called sialyl-LewisX (SLeX), which acts as a binding agent to help the sperm and egg stick together.

"This research provides an enlightening answer to a basic important question and human fertilisation -- how does a sperm bind to an egg?" William Yeung, one of the researchers, told AFP.

"But this is only a first step that will lead to more discoveries," said Yeung, who is also a professor at HKU's department of obstetrics and gynaecology.

The identification of SLeX will help to pinpoint patients whose infertility results from a lack of the substance.

Armed with this information, they will then be able to choose a fertility treatment known as intracytoplasmic sperm injection, which directly injects a single sperm into the egg, said the researcher.

The study, which began in 2009, found SLeX on 70 percent of all the 195 unfertilised eggs tested. The eggs were donated by patients.

Researchers expect the discovery to be put into clinical use in two years.

The study was conducted jointly with research groups from Imperial College in Britain, Academia Sinica in Taiwan and University of Missouri in the United States.

The study said that infertility affects about 15 percent of couples of reproductive age, citing figures from the World Health Organization.