NBC's A Different World ran for six seasons. It is a spin-off of The Cosby Show and centered on Denise Huxtable and students at Hillman College, a fictional mixed but historically black college in Virginia. After Bonet's first-season exit, the sitcom focused on Southern belle Whitley Gilbert and math whiz Dwayne Wayne. The series often featured black fraternities and sororities. A Different World was a spin-off of The Cosby Show, although it addressed subjects overlooked by that show. One of the first American network TV episodes to discuss HIV/AIDS aired in 1990.