Inflation in a five-dimensional brane world model with two boundary branes is studied .
We make use of the moduli space approximation whereby the low energy theory reduces to a four-dimensional biscalar-tensor gravity plus a minimally coupled scalar field .
After a detailed analysis of the inflationary solutions , we derive the evolution equations of the linear perturbations separating the adiabatic mode from two entropy modes .
We then examine the primordial scalar and tensor power spectra and show that their tilt depends on the scalar-tensor coupling constant .
Finally , the induced CMB anisotropies are computed and we present a Monte Carlo Markov Chains exploration of the parameter space using the first year WMAP data .
We find a marginalized probability bound for the associated Eddington parameter at the end of inflation 1 - \gamma < 2 \times 10 ^ { -3 } , at 95 \% confidence level .
This suggests that future CMB data could provide crucial information helping to distinguish scalar-tensor and standard inflationary scenarios .