Assuming imcastleman the CO? If so, since you have the A
I'd have a hard time putting him on anything other than JJ or 88 here, weighted toward the JJ. If unknown is CO, I can't find a fold.
I hate criticizing preflop raise sizes, but maybe a bit more (250?) to discourage pocket pairs from seeing a flop? Potentially getting 10:1 flopping a set is too much for a lot of people to pass on.