Advances Toward a Cure for HIV: Getting Beyond N=2
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Advances Toward Cure Volume 27 Issue 4 December 2019/January 2020 Perspective Advances Toward a Cure for HIV: Getting Beyond n=2 Achieving a cure for HIV remains a priority in HIV research. Two cases of ‘ster- long-term complications of HIV despite ilizing cure’ have been observed—in Timothy Ray Brown and the “London” ART, including evidence for accelerated patient; both patients received allogeneic hematopoietic stem cell transplan- aging and increased risks of cognitive tation (HSCT) from donors homozygous for the CCR5-delta 32 deletion, which dysfunction, cardiovascular disease, impairs function of an HIV coreceptor on host cells. Other strategies that have renal disease, and other complica- been evaluated for achieving sterilizing cure or functional cure—ie, sustained tions.3-6 All of these factors provide a virologic remission in the absence of antiretroviral therapy (ART)—include: strong rationale for pursuing cure for HSCT with wild-type CC chemokine receptor (CCR5); early ART to limit size HIV infection. of the HIV latent reservoir; shock and kill strategies using latency reversing agents and/or anti-HIV broadly neutralizing antibodies; and gene therapy, Mechanisms of HIV Persistence including attempts to modify CCR5 genes, HIV proviruses in autologous host cells, or enhanced T cells. This article summarizes a presentation by Jonathan Data from long-term follow-up of a co- Li, MD, MMSc, at the International Antiviral Society-USA (IAS-USA) continuing hort of patients on ART indicate that education program held in Atlanta, Georgia, in March 2019. the HIV reservoir, indicated by levels of HIV DNA in CD4+ cells and periph- Keywords: HIV cure, CCR5-delta 32 deletion, London patient, post-treatment eral blood mononuclear cells, initially controllers, early ART, shock and kill, gene therapy. declines during ART but plateaus at around 4 years and remains stable thereafter (Figure 1).7 Key factors in HIV HIV cure remains a priority of research ever, it is currently estimated that only persistence include viral integration in HIV infection management and 75% of infected individuals know of into the host cell genome and that the treatment. Pursuing this goal requires their infection status, 59% are on treat- integrated provirus can become latent identifying and developing strate- ment, and 47% have viral suppression.2 or silent, such that little viral RNA or gies to overcome mechanisms of HIV There are numerous issues that con- proteins are being expressed that would persistence to induce and maintain tribute to suboptimal ART treatment permit the immune system to recog- HIV remission. and retention in care. Many infected nize and target the infected cells. individuals are asymptomatic, leading Other factors may contribute to HIV Update on the Epidemic to delayed diagnosis, denial, or com- persistence. For example, some re- placency. Other factors that contribute searchers believe that there continues The advent of effective combination to gaps in the cascade of care include to be active viral replication in patients antiretroviral therapy (ART) has resulted challenges in accessing affordable and on ART, particularly within certain tis- in marked declines in HIV mortality consistent care, ART intolerability, pill sues or compartments where ART lev- and incidence. However, there remains fatigue, drug-drug interactions, stigma, els may be suboptimal.8,9 However, this much work to be done in battling the life chaos, substance abuse, and chal- is a relatively controversial hypothesis, epidemic. Joint United Nations Pro- lenges in connecting with hard-to- with the predominance of evidence gramme on HIV and AIDS (UNAIDS)/ reach populations. Further, there are demonstrating the lack of active viral World Health Organization (WHO) data indicate that there are more than 37 10,000 l million people globally living with HIV infection. Of these, 23 million are on 1 1000 u l A RT. There are 1.8 million new infec- l l l tions and nearly 800,000 AIDS-related u u u u deaths each year. The WHO introduced 100 the 90-90-90 initiative, aimed at achiev- ing awareness of infection status in 90% 10 PBMCs or CD4+ Cells 6 of infected individuals, having 90% of 6 l Total HIV-1 DNA copies/10 PBMCs 6 10 u Total HIV-1 DNA copies/10 CD4+ cells those individuals maintained on treat- DNA Copies per HIV-1 Total 1 ment, and achieving virologic suppres- 0 1 4 7 10 sion in 90% of those on treatment. How- Years on ART Dr Li is Assistant Professor of Medicine at Figure 1. Persistence of the HIV reservoir, indicated by levels of HIV DNA in CD4+ cells and Brigham and Women’s Hospital at Harvard peripheral blood mononuclear cells (PBMCs), during antiretroviral therapy (ART).Adapted from Medical School in Boston, Massachusetts. Besson, et al.7 91 IAS–USA Topics in Antiviral Medicine ART ART More recently, details have been presented about the “London patient.” 107 p This patient had Hodgkin lymphoma 106 and also received allogeneic HSCT with cells from a donor homozygous for the 105 CCR5 delta 32 deletion. The patient p 104 p had viral rebound during ART inter- ruption and achieved resuppression 3 p 10 with resumption of ART. After approxi- Copies RNA/mL HIV-1 102 p mately 18 months, ART was stopped, p and the patient has been free of viral p p p pp pp pp p p p p p p p p rebound for more than 2 years off ART 0 23 −227 −226 −85 −4 +61 +108 +159 +332 +391 +416 +548 (Figure 3). Differences between Mr Brown and First SCT the London patient include the fact that AML relapse Rectal biopsy AML relapse Second SCT AML diagnosis 100% chimerism Days 100% chimerism Mr Brown was initially heterozygous for the CCR5 delta 32 deletion, whereas the London patient was homozygous Figure 2. HIV remission in Timothy Brown by allogenic hematopoietic skin cell transplant for wild-type CCR5 before the trans- from a donor with the chemokine receptor 5–delta 32 deletion. Abbreviations: AML, acute myeloid leukemia; ART, antiretroviral therapy; SCT, gene for a human hormone secretion. plant. For AML, Mr Brown underwent Adapted from Hutter et al.22 2 HSCTs, total body irradiation, and full intensity conditioning chemother- replication in patients on fully suppres- allogeneic hematopoietic stem cell apy. For lymphoma, the London pa- sive ART.10-12 Another cause of HIV per- transplantation (HSCT), requiring condi- tient underwent a single HSCT, re- sistence lies in the infection of long- tioning chemotherapy and whole-body ceived no irradiation, and underwent lived cells as memory CD4+ cells and irradiation. In the search for a donor reduced-intensity conditioning. The hematopoietic progenitor cells.13 Fur- for the transplant, his physicians iden- mechanisms for T-cell depletion in the ther, infected cells, particularly CD4+ tified one who was both an HLA match 2 patients also differed. Perhaps the cells, can undergo homeostatic or clonal for Mr Brown and who was homozy- take-home lesson from the comparison proliferation, expanding the HIV reser- gous for the CCR5-delta 32 deletion. is that the highly toxic conditioning reg- voir.14-18 Finally, B cell follicles within As shown in Figure 2, Mr Brown’s viral imen and whole-body irradiation Mr lymph nodes act as an “immune sanctu- load increased during ART interrup- Brown received may not be necessary ary” that prevents access of HIV-specific tion for chemotherapy, and decreased for HIV eradication, that the same re- CD8+ cells, potentially allowing persis- when ART was resumed prior to trans- sult can be achieved with less intense tence of virus within lymph nodes.19,20 plantation.22 ART was stopped when he conditioning and without radiation. received a first transplantation, with no Together, the cases point to the impor- tance of the donor being homozygous Cure—Success Stories viral rebound. He subsequently experi- enced leukemic relapse and underwent for the CCR5-delta 32 deletion, but One example of cure is Timothy Ray a second transplantation, and has now additional studies will be needed to Brown (initially known as the “Ber- been HIV-free for more than 12 years assess the impact of other factors, such lin patient”). To understand this case off ART. as graft-versus-host reactions. it needs to be understood that HIV requires a CD4 receptor and a core- ART ART ceptor to gain entry to the host cell, 10,000 600 n especially the CC chemokine receptor 5 CD4+ Cells/µL l (CCR5). Individuals have been iden- 1,000 400 n n tified who are naturally resistant to n n l n n n acquiring HIV infection with the most n n 100 200 frequently transmitted CCR5-tropic vi- l ¢l ¢l¢l ¢l ¢l ¢l ¢l ¢l ¢l ¢ll ¢lll ¢l¢l¢l¢l¢l¢l ¢l¢l ¢l¢l ¢l ¢l¢l¢l ¢l rus due to the presence of a deletion in l Copies ofRNA/mL HIV the CCR5 gene, called the CCR5-delta 10 0 −215 −141 −27 +29 +77 +150 +424 +510 +1028 32 deletion, that impairs expression of 0 the CCR5 receptor.21 Days Timothy Ray Brown was living with HIV infection when he was diagnosed Figure 3. HIV remission in the London patient following CC chemokine receptor 5-delta 32/ with acute myeloid leukemia (AML). To delta 32 deletion hematopoietic stem-cell transplantation. ART indicates antiretroviral therapy. treat the leukemia, he was to undergo Adapted from Gupta et al.23 92 Advances Toward Cure Volume 27 Issue 4 December 2019/January 2020 Timothy Brown and the London for 8 months (Figure 4).28 Although no PTCs.31 PTCs accounted for 13% of par- patient represent achievement of a sterilizing cure was achieved, the find- ticipants who had early ART versus 4% sterilizing HIV cure, in which there is ings indicate that depletion of the HIV of participants who began ART during no functional HIV remaining in the reservoir can result in suppression lon- chronic infection (P < .01), suggesting body.