The London-based tenor, who left the successful opera group Amici Forever in 2006 when his then two-year-old daughter Sienna was diagnosed, has set up a foundation for Kiwi parents of autistic children and is donating part of the proceeds of his new solo album, Believe, to the cause.

He and his wife, Simone Lanham, co-wrote "Sienna's Song" on the album and say it's about giving parents hope.

Sewell said Sienna, who turns five tomorrow, had already been at school in the UK for six months and her progress was "awesome".

When Sienna was diagnosed, doctors told Sewell and Lanham that it was unlikely she would ever be able to speak, go to school, get married or have children.

Sewell says Sienna is speaking and learning, with the help of a one-on-one teacher aide in the classroom, and is making normal eye contact. Autism is a disorder of no known cause and people with it are often unable to communicate or interact socially with others.

The couple has just returned from a three-day autism conference in Philadelphia and said world experts spoke of the importance of a gluten and dairy-free detoxing diet and use of a therapy known as applied behaviour analysis to understand and change a child's behaviour.

They also met television star and former Playboy playmate Jenny McCarthy, who wrote a book about her son's autism.

The conference also heard debate about suggested links between autism and the measles, mumps and rubella vaccine.

The parents of Hannah Poling, a nine-year-old Atlanta girl, have won a case for compensation after authorities accepted their claim that vaccines contributed to the development of her autism. She was developing normally until she received a series of nine vaccines when she was 18 months old, after which she rapidly deteriorated.

Autism affects about one in 150 New Zealand children and numbers are increasing although there is debate about whether the prevalence is increasing or just awareness and diagnosis.

Source: Sunday Star Times