From Ineffabilis Deus, 1854, Pope Piux IX
Here is my literal translation of the dogma of the Immaculate Conception:
Declaramus, pronuntiamus et definimus
doctrinam quae tenet beatissimam Virginem Mariam
in primo instanti suae conceptionis fuisse
singulari Omnipotentis Dei gratia et privilegio,
intuitu meritorum Christi Jesu Salvatoris humani generis,
ab omni originalis culpae labe praeservatam immunem,
esse a Deo revelatam,
atque idcirco ab omnibus fidelibus
firmiter constanterque credendam.
We declare, pronounce, and define
the doctrine which holds the most blessed Virgin Mary,
in the first instance of her conception, to have been,
by a singular grace and privilege of Almighty God,
in view of the merits of Christ Jesus, Savior of the human race,
preserved immune from all stain of original sin,
has been revealed by God,
and so, for that reason, is to be believed
firmly and constantly by all the faithful.
Interestingly, the usual phrase for original sin, “originalis peccata”, is not used; instead, the phrasing is “originalis culpae”, which might also be translated as “original guilt”.