visual feedback for the user when he/she selects a filter - this can be acheived with the help of a simple loader icon in the results pane whenever the user has selected the filters.
I am guessing the filters is flyout menu below your header and it will be collapsed once the user has selected his filters .
In such a case , once the menu has collapsed, i would suggest dim the result screen with a centered loader icon, while the user waits for results from server.
Also denote a number in your collapsed filters menu section, so that the user is aware at any time a filter has been applied.
