  String-brane interactions provide an ideal framework to study the dynamics of
the massive states of the string spectrum in a non-trivial background. We
present here an analysis of tree-level amplitudes for processes in which an
NS-NS string state from the leading Regge trajectory scatters from a D-brane
into another state from the leading Regge trajectory, in general of a different
mass, at high energies and small scattering angles. This is done by using
world-sheet OPE methods and effective vertex operators. We find that this class
of processes has a universal dependence on the energy of the projectile and
that the tree-level amplitudes are in agreement with the eikonal operator form
of the string S-matrix.
