Cara joan, purtroppo S.V. (come SS.LL. = "Signorie Loro" per il plurale) si usa per rivolgersi a chiunque, quando si vuole fare un invito formale. Non c'è bisogno che siano nobili, scenziati, magistrati, cardinali, parlamentari o altro. Anche il parrucchiere o l'impiegato delle Poste possono ricevere un invito del genere dal loro circolo del bridgeWith more context, we'd be able to suggest the right translation. Depending on the title in English, we can say "your lordship," "your Honor," "your Excellency," etc.
There is an extremely formal way of writing an invitation in English very rarely used anymore, which puts the whole thing into the 3rd person passive. In this case it would read something like:
"The Dean is honored to invite the distinguished members of the commission to a dinner...."
[I learned to write and reply to these formal invitations in school, which is about as much use to me in these informal times as knowing how to use a slide rule has turned out to be.]