Presbyter Quintus is probably to be identified with Deacon Quintus, who carried a letter of Augustine to Nola (Augustinus, Letter 94,1 = Paulinus, Letter 35, 1).
A. Mandouze thinks that Presbyter Paulinus may have later become the bishop of Nola (PCBE Italie 1: Paulinus Iunior 7), known by the epitaph from 10 September 442 (Corpus Inscriptionum Latinarum X, 1340); he is of course different from the St Paulinus of Nola, who is the addressee of this letter.