We show that a dispiration (a disclination plus a screw dislocation) polarizes the vacuum of a scalar field giving rise to an energy momentum tensor which, as seen from a local inertial frame, presents non vanishing off-diagonal components. The results may have applications in cosmology (chiral cosmic strings) and condensed matter physics (materials with linear defects).It is fairly well known that a needle solenoid carrying a magnetic flux makes virtual charged particles to run around the solenoid inducing a non vanishing current density (see e.g. Ref [1]). We wish to consider what seems to be a gravitational (geometric) analogue of this AharonovBohm effect, by computing the vacuum expectation value of the energy momentum tensor of a massless and neutral scalar field far away from a dispiration.Let us begin by presenting the geometry of the background (units are such that c =h = 1),where the points labeled by (t, r, θ, z) and (t, r, θ+ 2π, z) are identified [2,3]. When α = 1 and κ = 0 Eq (1) becomes the line element of the flat spacetime written in cylindrical coordinates. Borrowing terminologies in condensed matter physics, the parameters α and κ correspond to a disclination and a screw dislocation, respectively. We should remark that Eq (1) may be associated with the gravitational background of certain chiral cosmic strings [4] (as has been suggested in Ref.[2]), as well as can describe (in the continuum limit) the effective geometry around a dispiration in an elastic solid (see Ref.[5] and references therein). The definitions ϕ := αθ and Z := z + κθ lead to2) * delorenci@unifei.edu.br † moreira@unifei.edu.br which should be considered together with the peculiar identification (t, r, ϕ, Z) ∼ (t, r, ϕ + 2πα, Z + 2πκ).Although Eq. (2) expresses the fact that the background is locally flat, due to Eq. (3) we cannot use Eq. (2) (which is a local statement) to infer that the global symmetries of the background are the same as those of the Minkowski spacetime (in this sense Eq. (2) is singular). In fact, Eq. (2) disguises a curvature singularity on the symmetry axis [2] (when κ = 0, in the context of the Einstein-Cartan theory, there is also a torsion singularity at r = 0 [3,6]). The vacuum expectation value of the energy momentum tensor is obtained by applying a differential operator to the renormalized scalar propagator around a dispiration (see e.g. Ref.[7]),