In both cases, the critical transplant was from a donor with a mutation in the CCR5 protein. The Times explained that HIV uses the protein to enter certain immune cells but cannot latch on to the mutated version. In other words, the donor was HIV-resistant.

Castillejo’s transplant was in May 2016. He has been off anti-HIV drugs since September 2017. He and Brown are the only patients known to have stayed HIV-free for more than a year after quitting the drugs.

To be cured of both cancer and HIV was “surreal,” Castillejo told the newspaper. “I never thought that there would be a cure during my lifetime.”

Details of the new case, to be published March 10 in Nature, were scheduled for presentation at this week’s Conference on Retroviruses and Opportunistic Infections, in Seattle.

Brown, whose case was described in 2007, is now 52 and living in Palm Springs, California.

He was far sicker after his procedures than Castillejo, and nearly died.