Because ProtoolsLe cannot process an input signal with a Plug-in, the only way to do this would be to use GuitarRig in standalone mode, using the Rig Controller under the ASIO driver(PC) or the (CoreAudioDriver) as the interface. ( Your guitar is plugged into Rig Control and the output of Rig Controller is routed to an input on your (MBox, or Digi002r etc)
Protools runs under a “DAE” driver.
On windows with Cubase, (Which also cannot process a VST plug-in on input) Guitar Rig Stand needs to run stand alone with ASIO drivers.
Note: Although this will work, it will really put a strain on the computer. Tons of ram and a fast CPU will be crucial.