  We consider an interacting theory of an infinite tower of massless
higher-spin fields in flat space with cubic vertices and their coupling
constants found previously by Metsaev. We compute the one-loop bubble diagram
part of the self-energy of the spin 0 member of the tower by summing up all
higher-spin loop contributions. We find that the result contains an
exponentially UV divergent part and we discuss how it could be cancelled by a
tadpole contribution depending on yet to be determined quartic interaction
vertex. We also compute the tree-level four-scalar scattering amplitude due to
all higher-spin exchanges and discuss its inconsistency with the BCFW
constructibility condition. We comment on possible relation to similar
computations in AdS background in connection with AdS/CFT.
