Five patients vaccinated against HIV manage virus levels without medication

The experimental vaccine, which underwent trails in Can Ruti, reduces the viral load to almost undetectable levels

Research into HIV has just taken a giant leap forward. For the first time, five patients have been able to manage the virus without taking any antiretroviral therapy for an extended period of time: five weeks in the shortest instance, and seven months in the longest. They were taking part in a clinical trial of a therapeutic vaccine conducted by the AIDS Research Institute and IrsiCaixa, a centre backed by La Caixa Foundation and the Catalan Government’s Department of Health. The results were presented yesterday at the world's largest conference on HIV, the Conference on Retroviruses and Opportunistic Infections (CROI) currently underway in Seattle (USA).

It is the first time that a patient who has stopped taking medication has gone longer than four weeks without increasing their viral load. Instances of "natural controllers", who keep the virus at bay without medication are exceptional cases. These are individuals with a unique genetic makeup and ultimately it is not known how this happens. By using the therapeutic vaccine, the researchers were able to induce this capacity for self-control. In spite of the excellent results, the researchers recommend caution. "We don’t know how long it might last", warns Dr Beatriz Mothe, who jointly coordinated the study with Dr Josep Moltó. "What we have achieved is a proof of concept", added IrsiCaixa’s director, Dr Bonaventura Clotet. "It will take between 10 and 15 years to develop a vaccine that can be used with the entire infected population, and it will be used in conjunction with other strategies".

13 patients participated in the study, which was conducted at the Hospital Germans Trias i Pujol, in Badalona. However, only five managed to control the virus. All of them received two doses of the therapeutic vaccine, which was developed at Oxford University. In between the two doses, they were given a drug commonly used to treat lymphoma which was administered intravenously.

The new treatment represents a two-pronged approach. On the one hand, it boosts the patient's immune response to the vaccine, by stimulating their CD8 lymphocytes, which are responsible for recognizing and destroying infected cells. On the other, the drug serves to "wake up" the viral reservoir, Clotet went on to explain. The vaccine alone is not enough, since it has been known for some time that these latent viruses are able to hide in certain cells. They thereby evade the immune system, which is unable to detect them, and remain ready for activation at any time. For this reason treatment cannot be permanently halted. "Our strategy seeks to purge the viral reservoir”, explained Moltó.

The five individuals who were able to manage their HIV without medication have almost undetectable levels of the virus. "They are not cured, we have turned them into controllers”, Moltó announced. Typically, when antiretroviral treatment is interrupted without any intervention, "virus levels begin to rise after four weeks", says Clotet. In the case of these five patients, there have been small sporadic increases in their viral load, but these have subsequently declined a short time later.

The challenge of improving efficacy

The next round of clinical trials will need to find "how to increase the efficacy of the treatment so that it is effective in all patients, either through an improved vaccine, repeated cycles of lower doses of antiviral drugs or through the use of other products that are currently under development", said Moltó. The trial’s success is also due to the fact that the participants in the study had been diagnosed so early, within six months of being infected, when it was not so acute, and their viral reservoir was low. Making progress in terms of early diagnosis is also key, therefore. At present, however, "only 5-10% of patients are diagnosed so early," says Clotet.

The patients in the trial had participated in an earlier study which only involved the vaccine and in which the treatment was not interrupted. It served to ensure the vaccine was safe to use.

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