De or het leprastichting?

The correct Dutch article is:

de leprastichting

Rule Words ending in -ing: almost always de. See the rule

How to use leprastichting

the leprastichtingde leprastichting
this leprastichtingdeze leprastichting
that leprastichtingdie leprastichting
our leprastichtingonze leprastichting
your leprastichtingjouw leprastichting
every leprastichtingelke leprastichting
which leprastichting?welke leprastichting?
a big leprastichting / the big leprastichtingeen grote leprastichting, de grote leprastichting