Gaude et laetare is a versicle sung after the antiphon with the respond Quia surrexit... followed by the collect prayer. The versicle and respond are typically sung on a single pitch, droping a m3 at the end of each line, and the collect can be chanted to one of the collect formulas. If you are looking at the Parish Book of Chant at #215 you will see the text all there following the solemn tone of the Regina Caeli. The same would be true for the Simple tone, it's just not reprinted to save space.

This is true for all the votive antiphons, Alma Redemptoris, Salve Regina, and Ave Regina Caelorum. There is the antiphon proper, which can be sung on it's own, or it can be followed by the versicle, resond and collect as prescribed in night prayer.

Suzanne,

Many similar sorts of prayers and hymns are followed by the versicle and response, at least in the traditional singing of them. The Veni Creator, sung at Pentecost, has its own proper set of versicles, and so does the Asperges me, as does the Vidi Aquam, and (as Earl Grey points out) each of the Marian antiphons.

Scott,

I suppose it's possible, but there wasn't any reason to suppress it: it involved ordinary lay folk having a response; it could be massacred like the rest of the translation; the versicle and collect are used (mostly) among those who pray the Office, rather than adding uselessly to the time needed for no-repetitions-Mass.

They include the versicle in both Latin & English in iBreviary