Human immunodeficiency virus is notorious for its persistence. The virus can lurk within the body for decades and attacks immune cells, compromising a person’s ability to fight other infections. If untreated, HIV infections nearly always progress into AIDS, or acquired immunodeficiency syndrome, which is lethal without intervention. But for the second time, researchers have found a person whose body seems to have managed to rid itself of the virus.  

Published in Annals of Internal Medicine on November 16, the case report details a likely “sterilizing cure” of an HIV-1 infection. The only other potential case was reported in a 2020 Nature study of elite controllers—rare individuals whose immune systems can limit the replication of HIV without antiretroviral drugs.

In the 2020 study, researchers attempted to determine the persistence of HIV over several years in 64 elite controllers by sequencing copies of the viral genome that had integrated into their cells’ DNA, a technique called provirus sequencing. The researchers identified intact HIV genomic sequences in all of the participants except for one: Loreen Willenberg, also known as the “San Francisco Patient.” The team was unable to detect viral genetic material in more than 1.5 billion of her blood cells.

For the new report, researchers employed similar methods to an elite controller in Argentina who has been the subject of an HIV study since 2017, and found that the patient appears to have cleared the virus without medical aid. The Argentinian woman, now dubbed the “Esperanza patient,” was diagnosed with HIV in 2013 when antibodies and fragments of HIV suggested she was previously infected, according to STAT and The Washington Post. She has not received any HIV treatment in the eight years since her diagnosis, save for antiretroviral pills taken during the last two trimesters of her pregnancy in 2020. Proviral sequencing and viral outgrowth assays were unable to detect HIV in almost 1.2 billion of her blood cells collected since 2017 and 503 million of her placental cells collected after she gave birth in March 2020. The woman exhibits no signs of illness, the researchers report, and hospital tests found no evidence that the virus was replicating in her body.

Immunologist Xu Yu, the new study’s senior author, tells STAT that “This gives us hope that the human immune system is powerful enough to control HIV and eliminate all the functional virus.”

University of California, San Francisco HIV researcher Steven Deeks, who helped identify the San Francisco Patient but was not involved in the new research, tells the Post that the study’s observations are unique. “It’s not that she’s controlling the virus, which we do see, but that there’s no virus there, which is quite different,” he says. Deeks also proposes a possible explanation for the self-curing abilities of these two women, suggesting they may possess ultra-powerful T cells.

See “‘Public’ T-Cell Receptors From Resistant People Fend Off HIV”

Johns Hopkins HIV researcher Joel Blankson postulates in an editorial that the Esperanza patient’s immune system could have developed an HIV-specific response before she was ever infected, as her partner had died from AIDS. He also suggests lines for future research, suggesting the cells of the Esperanza patient can be used to replicate her immune system in mouse HIV models, which could in turn inform future HIV treatment techniques.

The team acknowledges limitations to their work, including that their results cannot prove the complete absence of HIV. HIV researcher and physician Natalia Laufer at El Instituto de Investigaciones Biomédicas en Retrovirus y SIDA in Buenos Aires, who treated the Esperanza patient, tells STAT that it is impossible to sequence every single cell in a person, and thus scientists may never be able to use the word “cure” to describe their findings. Nevertheless, she says she is confident in the conclusion that the patient is HIV-free and that the results are paradigm-shifting.

Esperanza is the Spanish word for hope, and the Esperanza patient—who did not want her identity revealed—wrote to STAT that she feels blessed and that she has a responsibility to help others with HIV.