There are many publications that suggest that autism spectrum disorders are caused by different neuron wiring compared to so called neuro-typical human. The nature of this differences is not well understood but it does not sound like something that can simply 'treated'
With some anecdotal evidence: my nephews autism (two nephews) have been improved (the symptoms lessened) by putting them on something called the "GAPS diet" for the past few years, moving them from pretty much being locked in a world of their own to interacting playfully with each other and making eye contact with trusted adults.
Of course, this is not a scientific study, and there may have been other influences in their improvement. But a definite improvement has been made.
EDIT: good article how some people are able to function with autism (which may look like treatment but it is not) http://www.nytimes.com/2014/08/03/magazine/the-kids-who-beat...