  The quadruply lensed quasar HE0435-1223 shows a clear microlensing effect
that affects differently the blue and red wings of the H$\alpha$ line profile
in its image D. To interpret these observations, and constrain the broad
emission line region (BLR) properties, the effect of gravitational microlensing
on quasar broad emission line profiles and their underlying continuum has been
simulated considering representative BLR models and microlensing magnification
maps. The amplification and distortion of the H$\alpha$ line profile,
characterized by a set of four indices, can be reproduced by the simulations.
Although the constraints on the BLR models set by the observed single-epoch
microlensing signal are not very robust, we found that flattened geometries
(Keplerian disk and equatorial wind) can more easily reproduce the observed
line profile deformations than a biconical polar wind. With an additional
independent constraint on the size of the continuum source, the Keplerian disk
model of the H$\alpha$ BLR is slightly favored.
