  Lines generated by marginal deformations of WZW models are considered. The
Weyl symmetry at the WZW point implies the existence of a duality symmetry on
such lines. The duality is interpreted as a broken gauge symmetry in string
theory. It is shown that at the two end points the axial and vector cosets are
obtained. This shows that the axial and vector cosets are equivalent CFTs both
in the compact and the non-compact cases. Moreover, it is shown that there are
$\s$-model deformations that interpolate smoothly between manifolds with
different topologies.
