The world's second HIV patient whose body appears to have rid itself off the virus without the use of antiretroviral drugs has been identified, scientists said on Tuesday.
The finding, published in the journal Annals of Internal Medicine, shows that the untreated person, known as the Esperanza Patient, living with HIV had no evidence of intact viral genomes in more than 1.5 billion blood and tissue cells analysed.
The international team noted that if the immune mechanisms underlying this response can be understood by researchers, they may be able to develop treatments that teach others' immune systems to mimic these responses in cases of HIV infection.
During infection, HIV places copies of its genome into the DNA or genetic material of cells, creating what is known as a viral reservoir, the researchers said.
In this state, the virus effectively hides from anti-HIV drugs and the body's immune response, they said.
In most people, new viral particles are constantly made from this reservoir.
Anti-retroviral therapy (ART) can prevent the new viruses from being made but cannot eliminate the reservoir, necessitating daily treatment to suppress the virus.
The researchers noted that some people, known as elite controllers, have immune systems that are able to suppress HIV without the need for medication.
Though they still have viral reservoirs that can produce more HIV virus, a type of immune cell called a killer T cell keeps the virus suppressed without the need for medication, they explained.
In their previous study, the scientists identified one patient who had no intact HIV viral sequence in her genome, indicating that her immune system may have eliminated the HIV reservoir -- what scientists call a sterilising cure.
The team sequenced billions of cells from this patient, known as the San Francisco Patient, searching for any HIV sequence that could be used to create new virus, and found none.
The finding, the first known incidence of a sterilising cure without a stem cell transplant, was reported in Nature journal in 2020.
The same group now reports a second untreated HIV-infected patient who, like the San Francisco Patient, has no intact HIV genomes found in more than 1.19 billion blood cells and 500 million tissue cells sequenced.
The finding may represent a second instance of a sterilising cure, the researchers said.
"These findings, especially with the identification of a second case, indicate there may be an actionable path to a sterilising cure for people who are not able to do this on their own," said Xu Yu, a physician investigator at Massachusetts General Hospital, US.
She explained that these findings may suggest a specific killer T cell response common to both patients driving this response, with the possibility that other people with HIV have also achieved a sterilising cure.
"We are now looking towards the possibility of inducing this kind of immunity in persons on ART through vaccination, with the goal of educating their immune systems to be able to control the virus without ART," Yu added.
