There's no built-in way to do this, but there are a lot of ways to do it with additional tools. For example, you might try using a preprocessor: https://adityam.github.io/context-blog/post/markdown-with-gpp/
You could also use <div lang="italian">
and <span lang="italian">
, together with a custom filter. See http://johnmacfarlane.net/pandoc/scripting.html.