  In this note, we construct a BRST invariant cubic vertex for massless fields
of arbitrary mixed symmetry in flat space-time. The construction is based on
the vertex given in bosonic Open String Field Theory. The algebra of gauge
transformations is closed without any additional, higher than cubic, couplings
due to the presence of an infinite tower of massless fields. We briefly discuss
the generalization of this result to a curved space-time and other possible
implications.
