Can the acronym package be told to use a certain style?

\renewcommand*{\acffont}[1]{\textit{#1}}

sets the font of the entire full expression, including the long form, parentheses and acronym. In order to only make the long form italics, one has to override the italic mode for the remainder of the full expression by adding:

\renewcommand*{\acfsfont}[1]{\textnormal{#1}}