Many men in the gay community have been test for various strains of HPV and some are
in trials being vaccinated against the strains
in the HPV Vaccination. The doctors might also be able to do HPV titers. If he is already exposed (many males have been) then there may be no risk by additional exposures.
You can take the same precautions that serodiscordant (One person HIV Positive and the other person HIV Negative) partners take (dental dams, condoms, etc.