Eli Wheatley and Christian Guardino are among a growing number of patients whose lives are apparently being saved or radically improved by gene therapy.  Wheatley, 3, of Lebanon, Ky., and Guardino, 17, of Patchogue, N.Y., were both diagnosed with what were long thought to be incurable genetic disorders. In the past, Wheatley’s condition would have probably killed him before his first birthday. Guardino’s would have blinded him early in life.