How Did the 'Berlin Patient' Rid Himself of HIV?

sciencehabit writes: Researchers are closer to unraveling the mystery of how Timothy Ray Brown, the only human cured of HIV, defeated the virus, according to a new study. Although the work doesn't provide a definitive answer, it rules out one possible explanation. [R]esearchers point to three different factors that could independently or in combination have rid Brown’s body of HIV. The first is the process of conditioning, in which doctors destroyed Brown’s own immune system with chemotherapy and whole body irradiation to prepare him for his bone marrow transplant. His oncologist, Gero Hütter, who was then with the Free University of Berlin, also took an extra step that he thought might not only cure the leukemia but also help rid Brown’s body of HIV. He found a bone marrow donor who had a rare mutation in a gene that cripples a key receptor on white blood cells the virus uses to establish an infection. (For years, researchers referred to Brown as "the Berlin patient.") The third possibility is his new immune system attacked remnants of his old one that held HIV-infected cells, a process known as graft versus host disease.

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Summary missing punchline

[quantaman]

According to the summary

Although the work doesn't provide a definitive answer, it rules out one possible explanation. [R]esearchers point to three different factors that could independently or in combination have rid Brown’s body of HIV.

Unfortunately the summary forgets to mention the explanation that was ruled out or even clearly delineate the three different factors (though the latter was more the fault of the original article).

From my reading of TFA:

Explanation 1: Conditioning: The radiation that destroyed his immune system also killed off the HIV (because HIV lives in the cells of the immune system).

Explanation 2: Shiny new immune system: The new bone marrow had a mutation that was immune to HIV and that cured him (maybe by detecting and killing HIV infected cells?).

Explanation 3: Graft vs host: The new immune system killed off his old one, not just the HIV infected cells but all the old immune systems cells including those infected with HIV.

So the researchers took chimps, extracted some stem cells (bone marrow?), infected them with SHIV (Simian HIV), destroyed their immune systems with radiation, then reinjected the uninfected stem cells.

The SHIV quickly came back which rules out explanation 1.