A businessman pledged $100 million Wednesday to Massachusetts General Hospital to create an institute that will search for vaccines for AIDS and other infectious diseases.

The gift from Phillip Ragon will help create an institute whose first task will be finding an effective vaccine against AIDS.

The Phillip T. and Susan M. Ragon Institute eventually will bring scientists, clinicians and engineers together from the hospital, Harvard University and the Massachusetts Institute of Technology to fight a wide range of infectious diseases and cancers.

"Recent scientific advances have brought us closer to the elusive goal of an AIDS vaccine," said Bruce Walker, a physician-investigator at Massachusetts General who will be the institute's director. "But reaching that goal will require broad collaboration."

The hospital will get $10 million in each of the next 10 years. According to hospital officials, the $100 million pledge is the largest donation in the hospital's history.

The 59-year-old Ragon is the founder and sole owner of InterSystems Corp., a Cambridge company that provides database software to hospitals and other industries.