Johns Hopkins said it was set to perform the first kidney and liver transplants between H.I.V.-positive donors and H.I.V.-positive patients in the United States, a development that advocates said could create a lifesaving pipeline for H.I.V. patients while shortening organ donor waiting lists for all. r. Dorry Segev, an associate professor of surgery at the Johns Hopkins University School of Medicine, estimated that organs from 500 to 600 H.I.V.-positive potential donors have gone to waste each year.