  We study the electronic states that are formed due to the tunnel coupling
between helical edge states (HESs) and bound states of nonmagnetic point
defects in two-dimensional topological insulators in the general case of broken
axial spin symmetry. It is found that the coupling of HESs and a single defect
leads to the formation of composite HESs composed of the bound states and a set
of the conventional HESs. Their spectral density near the defect has a
resonance shifted relative to the energy level of the bound state. But of most
importance is a long-range perturbation of the HESs around the defect, which is
a cloud consisting of both Kramers partners of conventional edge states.
Therefore each of the composite HESs contains both the right- and left-moving
conventional HESs. The amplitude of this perturbation decreases inversely with
the distance from the defect. In a system of many defects, this perturbation
leads to a long-range coupling between bound states of different defects
mediated by the HESs and causes amazing effects. We study these effects for a
two-defect system where the proposed mechanism of indirect coupling leads to a
splitting of the resonances of isolated defects even if the distance between
them is very large. As a result an asymmetric structure of two-peak resonance
arises that very unusually changes with the distance between the defects.
