CHICAGO--(BUSINESS WIRE)--Fitch Ratings affirms the 'AAA' ratings of the Variable Rate MuniFund Term Preferred Shares (VMTP Shares) issued by DTF Tax-Free Income Inc. (NYSE: DTF), a closed-end fund managed by Duff & Phelps Investment Management Co.: --$65,000,000 Series 2018 VMTP shares due August 2018. KEY RATING DRIVERS The rating affirmation primarily reflects: -- Sufficient asset coverage provided to the VMTP shares as calculated per the fund's over-collateralization (OC) tests; -- The