A patient with HIV remission induced by stem cell transplantation continues to be disease free at the 30-month mark.
The individual, referred to as the London patient, received allogeneic hematopoietic stem cell transplantation (allo-HSCT) for stage IVB Hodgkin lymphoma. The transplant donor was homozygous for the CCR5 delta-32 mutation, which confers immunity to HIV because there’s no point of entry for the virus into immune cells.
After extensive sampling of various tissues, including gut, lymph node, blood, semen, and cerebrospinal fluid (CSF),, and colleagues found no detectable virus that was competent to replicate. However, they reported that the testing did detect some “fossilized” remnants of HIV DNA persisting in certain tissues.
The results were shared in a video presentation of the research during the Conference on Retroviruses & Opportunistic Infections, which was presented online this year. CROI organizers chose to holdbecause of concerns about the spread of COVID-19.
The London patient’s HIV status had been reported the previous year at CROI 2019, but only blood samples were used in that analysis.
Inaccompanying the , , and , asked: “A key question now for the area of HIV cure is how soon can one know if someone has been cured of HIV?
“We will need more than a handful of patients cured of HIV to really understand the duration of follow-up needed and the likelihood of an unexpected late rebound in virus replication,” continued Dr. Zerbato, of the University of Melbourne, and Dr. Lewin, of the Royal Melbourne Hospital and Monash University, also in Melbourne.
In their ongoing analysis of data from the London patient, Dr. Gupta, a virologist at the University of Cambridge (England), and associates constructed a mathematical model that maps the probability for lifetime remission or cure of HIV against several factors, including the degree of chimerism achieved with the stem cell transplant.
In this model, when chimerism reaches 80% in total HIV target cells, the probability of remission for life is 98%; when donor chimerism reaches 90%, the probability of lifetime remission is greater than 99%. Peripheral T-cell chimerism in the London patient has held steady at 99%.
Dr. Gupta and associates obtained some testing opportunistically: A PET-CT scan revealed an axillary lymph node that was biopsied after it was found to have avid radiotracer uptake. Similarly, the CSF sample was obtained in the course of a work-up for some neurologic symptoms that the London patient was having.
In contrast to the first patient who achieved ongoing HIV remission from a pair of stem cell transplants received over 13 years ago – the Berlin patient – the London patient did not receive whole-body radiation, but rather underwent a reduced-intensity conditioning regimen. The London patient experienced a bout of gut graft-versus-host disease (GVHD) about 2 months after his transplant, but has been free of GVHD in the interval. He hasn’t taken cytotoxic agents or any GVHD prophylaxis since 6 months post transplant.
Though there’s no sign of HIV that’s competent to replicate, “the London patient has shown somewhat slow CD4 reconstitution,” said Dr. Gupta and coauthors in discussing the results.
The patient had a reactivation of Epstein-Barr virus (EBV) about 21 months after analytic treatment interruption (ATI) of antiretroviral therapy that was managed without any specific treatment, but he hasn’t experienced any opportunistic infections. However, his CD4 count didn’t rebound to pretransplant levels until 28 months after ATI. At that point, his CD4 count was 430 cells per mcL, or 23.5% of total T cells. The CD4:CD8 ratio was 0.86; normal range is 1.5-2.5.
The researchers used quantitative real-time polymerase chain reaction (rt-PCR) to look for packaging site and envelope (env) DNA fragments, and droplet digital PCR to quantify HIV-1 DNA.
The patient’s HIV-1 plasma load measured at 30 months post ATI on an ultrasensitive assay was below the lower limit of detection (less than 1 copy per mL). Semen viremia measured at 21 months was also below the lower limit of detection, as was CSF measured at 25 months.
Samples were taken from the patient’s rectum, cecum, sigmoid colon, and terminal ileum during a colonoscopy conducted 22 months post ATI; all tested negative for HIV DNA via droplet digital PCR.
The lymph node had large numbers of EBV-positive cells and was positive for HIV-1 env and long-terminal repeat by double-drop PCR, but no integrase DNA was detected. Additionally, no intact proviral DNA was found on assay.
Dr. Gupta and associates speculated that “EBV reactivation could have triggered EBV-specific CD4 and CD8 T-cell responses and proliferation, potentially including CD4 T cells containing HIV-1 DNA.” Supporting this hypothesis, EBV-specific CD8 T-cell responses in peripheral blood were “robust,” and the researchers also saw some CD4 response.
“Similar to the Berlin patient, highly sensitive tests showed very low levels of so-called fossilized HIV-1 DNA in some tissue samples from the London patient. Residual HIV-1 DNA and axillary lymph node tissue could represent a defective clone that expanded during hyperplasia within the lymph note sampled,” noted Dr. Gupta and coauthors.
Responses of CD4 and CD8 T cells to HIV have also remained below the limit of detection, though cytomegalovirus-specific responses persist in the London patient.
As with the Berlin patient, standard enzyme-linked immunosorbent assay (ELISA) testing has remained positive in the London patient. “Standard ELISA testing, therefore, cannot be used as a marker for cure, although more work needs to be done to assess the role of detuned low-avidity antibody assays in defining cure,” noted Dr. Gupta and associates.
The ongoing follow-up plan for the London patient is to obtain viral load testing twice yearly up to 5 years post ATI, and then obtain yearly tests for a total of 10 years. Ongoing testing will confirm the investigators’ belief that “these findings probably represent the second recorded HIV-1 cure after CCR5 delta-32/delta-32 allo-HSCT, with evidence of residual low-level HIV-1 DNA.”
Dr. Zerbato and Dr. Lewin advised cautious optimism and ongoing surveillance: “In view of the many cells sampled in this case, and the absence of any intact virus, is the London patient truly cured? The additional data provided in this follow-up case report is certainly exciting and encouraging but, in the end, only time will tell.”
Dr. Gupta reported being a consultant for ViiV Healthcare and Gilead Sciences; several coauthors also reported financial relationships with pharmaceutical companies. The work was funded by amfAR, the American Foundation for AIDS Research, and the Wellcome Trust. Dr. Lewin reported grants from the National Health and Medical Research Council of Australia, the National Institutes of Health, the American Foundation for AIDS Research, Gilead Sciences, Merck, ViiV Healthcare, Leidos, the Wellcome Trust, the Australian Centre for HIV and Hepatitis Virology Research, and the Melbourne HIV Cure Consortium. Dr. Zerbato reported grants from the Melbourne HIV Cure Consortium,