A man in London has become the second known HIV-positive adult to be cleared of the virus that causes the disease AIDS. The man received a stem cell transplant three years ago. He was treated with anti-retroviral drugs until about 18 months ago. Now, tests show he has no sign of the HIV virus in his blood.

    "There is no virus there that we can measure. We can't detect anything," said Ravindra Gupta, a professor and HIV scientist who helped lead a team of doctors treating the man.
    教授和艾滋病毒科学家拉文德拉·古普塔(Ravindra Gupta)协助领导了一个治疗该男子的医疗团队,他说:“我们(在病人体内)检测不到病毒,找不到任何病毒。”

    The patient's name, nationality or age is not public. He is being called "the London patient" because he was treated in the British capital. A similar identification was given to the first known person cleared of HIV infection more than ten years ago, the "Berlin patient." Both men experienced a similar treatment.

    Experts who study AIDS say the success of the Berlin patient and the London patient is very important. Their experiences show that scientists will one day be able to end AIDS.

    But experts warn that a cure has not been found. The blood treatments the Berlin and London patients had have failed in other patients. The treatments are also too dangerous, expensive and risky to do for the large number of people who already have the virus that causes AIDS. The United Nations estimates that 37 million people worldwide are living with HIV.

    The London patient

    The medical story of the London patient begins in 2003. At that time, he was found to have the HIV infection.

    Then, in 2016, he developed a kind of cancer that affects the immune system, the part of the body that fights disease. To treat the cancer, the London patient agreed to a treatment called a stem cell transplant.

    In the transplant, a healthy donor provides extremely small pieces of his or her body that can create new blood. These are released into the patient's blood system. If the treatment is successful, the patient's body uses the other person's stem cells to build a healthy immune system.

    But there was something unusual about the person who gave the London patient stem cells. The giver – or donor – had a natural resistance to HIV. In other words, something about this person's body made it impossible for him or her to become infected with the HIV virus. As a result, when the London patient received the stem cells, his immune system changed and he developed a natural resistance to HIV, too.

    The doctors note that the donor's natural resistance to HIV is very rare. Only about 1 percent of people who come from northern European relatives have it. The unusual situation is one reason why this way of treating HIV is not done more often.

    But in the case of the London patient, the treatment worked.

    Ravindra Gupta notes that the donor's unusual resistance to HIV may not be the only reason the treatment cleared the London patient's infection. He notes that the Berlin patient and the London patient had similar side effects after the treatment. In both cases, the donors' stem cells immediately began to attack the patients' immune cells. The interaction may have helped destroy some of the HIV infection in the patients, Gupta says.

    His team plans to use their findings to explore possibilities for future HIV treatment plans. They will present what they have learned so far in the next days in the journal Nature, and at a medical conference in the U.S. city of Seattle, Washington.

    I'm Jill Robbins.