Woops, looked more carefully at your code and found a few problems.
RewriteCond %{QUERY_STRING} /interviews/?interview=(.*)
The 'query string' is everything in the URI after the question mark, so you probably want to remove everything before (and including) the question mark on that line.
Also, on my installation of Apache 2.2 (on Windows), the URL passed to the RewriteRule doesn't begin with a leading '/', so your pattern wouldn't ever match a URL on my computer. Not sure if the *nix version of the webserver is different (don't know why it would/should be, either), but you could cover both cases by adding a '?' after the slash (indicating it should appear 0 or 1 times, according to standard regular expression syntax).