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Effect of Antiretroviral Therapy on HIV Reservoirs in Elite Controllers
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Journal of Infectious Diseases Advance Access published July 11, 2013
Tae-Wook Chun1,6, J. Shawn Justement1, Danielle Murray1, Connie J. Kim2, Jana Blazkova1, Claire W. Hallahan1, Erika Benko3, Cecilia T. Costiniuk4, Gabor Kandel5, Mario Ostrowski2,5, Rupert Kaul2, Susan Moir1, Joseph P. Casazza1, Richard A. Koup1, Colin Kovacs2,3, and Anthony S. Fauci1
1National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, Maryland, USA 2Department of Medicine, University of Toronto, Toronto, Ontario, Canada 3Maple Leaf Medical Clinic, Toronto, Ontario, Canada 4Department of Medicine, The Ottawa Hospital, Ottawa, Ontario, Canada 5St. Michael's Hospital and the Li Ka Shing Knowledge Institute, Toronto, Ontario, Canada
"In summary, we demonstrated that ART results in a marked diminution of the number of infected CD4+ T cells carrying replication-competent HIV in elite controllers, suggesting that low levels of ongoing viral replication contributes to the maintenance of HIV reservoirs in the absence of detectable plasma viremia."
"the cultures from Subject 2, 3, and 4 had readily detectable levels of replication competent HIV at baseline and three months following cessation of ART.....Of note, the infectious HIV burden returned to the pre-therapy level in all study subjects 3 months following discontinuation of ART (Figure 1C and Online Table 1). Although testing for statistical significance was not performed due to the small sample size, the mean log10 decrease (month 0 vs. month 9) and increase (month 9 vs. month 12) of the infectious HIV burden were - 1.2938 and +1.3379, respectively, clearly demonstrating that ART had an impact on the size of the pool of infected CD4+ T cells carrying replication-competent HIV in the study subjects......levels of immune activation (T cells expressing CD38 and HLA-DR) were evaluated in the blood and sigmoid colon and found to be decreased during ART and returning to pre-ART levels following discontinuation of therapy in three of the four subjects studied....we investigated the impact of ART on the frequency of HIV-specific CD8+ T cells in the blood of the three elite controllers. As shown in Figure 1D, the frequency of HIV-specific CD8+ T cells expressing intracellular IFN-y and MIP-1ß decreased during the treatment period and levels remained low to undetectable following cessation of ART in all three individuals."
from Jules: several recent studies including at IAS Kuala Lumpur found ART during primary infection reduced HIV-DNA levels and slowed disease progression, that HIV-DNA levels were associated with disease progression, and that ART >500 CD4s also reduce HIV-DNA reservoirs compared to delayed ART. I think I recall several studies in elite controllers found they still had inflammation/activation ongoing which may increase their risk for comorbidities despite undetectable plasma HIV-RNA.
IAS: ART Started in Primary Infection May "Block Immunologic Storm" in French OPTIPRIM - (07/12/13)
Abstract
Elite controllers suppress HIV viremia to below the limit of detection in the absence of antiretroviral therapy (ART). However, precise frequencies of CD4+ T cells carrying replication-competent HIV and/or the dynamics of the infectious viral reservoirs in response to initiation and discontinuation of ART in elite controllers are unknown. We show that the size of the pool of CD4+ T cells harboring infectious HIV diminished significantly following initiation of ART and rebounded to baseline upon cessation of therapy. Our data provide compelling evidence that persistent viral replication occurs in untreated elite controllers even in the absence of detectable plasma viremia.
INTRODUCTION
Antiretroviral therapy (ART) suppresses plasma viremia to below the limit of detection in the vast majority of human immunodeficiency virus (HIV)-infected individuals and reduces the rate of viral transmission, morbidity, and mortality where antiretroviral drugs are available [1]. However, standard ART alone cannot eradicate HIV in infected individuals due in part to the persistence of viral reservoirs in the peripheral blood, lymphoid tissues, and other sequestered sites [2]. Consequently, there is a growing interest in developing therapeutic strategies to eliminate persistent HIV reservoirs and/or to enhance host immunity against the virus in order to control viral replication in the absence of ART [2]. In this regard, it has been shown that a small proportion of HIV-infected individuals spontaneously control plasma viremia in the absence of ART (controllers) [3]. Moreover, a subset of such individuals (elite controllers) are capable of maintaining relatively normal CD4+ T cell counts and undetectable levels (<50 copies of HIV RNA/ml) of plasma viremia for years to decades without the need for ART [3]. Although previous studies have suggested that ongoing viral replication may occur in elite controllers based on persistence of residual plasma viremia and immune activation [4, 5] as well as evidence for viral evolution in plasma HIV [6, 7], precise frequencies of infected CD4+ T cells carrying replication-competent virus and/or the impact of ART on immunologic and virology parameters have not been fully delineated in this patient population. Given recent interest in developing therapeutic strategies aimed at achieving containment of HIV replication in the absence of ART, as observed in elite controllers, and considering that a certain percentage of these individuals may eventually experience disase progression [8], we conducted the present study to address these questions.
RESULTS
Three elite controllers (Subjects 1, 2, and 3) and one controller (Subject 4) (Table 1) received standard ART consisting of tenofovir/emtricitabine and raltegravir for 9 months followed by discontinuation of ART. For this study, controllers and elite controllers are defined by the ability to suppress HIV plasma viremia <500 and <50 copies of HIV RNA/ml, respectively, in the absence of ART with no more than 1 viral blip above these cut-off values (Table 1).
Blood draws and leukapheresis were conducted at month 0 (prior to the initiation of ART), 6, and 9 months following the initiation of ART, and 3 months following discontinuation of ART. Gut biopsies (sigmoid colon) were also obtained at month 0 and 6 and 3 months after cessation of ART. CD4+ and CD8+ T cell percentages in the blood of all study subjects remained stable throughout the course of the study (Figure 1A). All elite controllers maintained <20 copies of HIV RNA per ml of plasma throughout the entire study period (Figure 1B). There was no significant difference in residual plasma viremia (1-19 copies of HIV RNA/ml) prior to and following initiation and after discontinuation of ART in the elite controllers (data not shown). In Subject 4, the baseline plasma viremia (88.0±25.9; mean±SD) became undetectable shortly after initiation of ART and returned to a detectable level (131.5±24.6; mean±SD) following discontinuation of therapy (Figure 1B).
Given that the vast majority of HIV-infected CD4+ T cells carry defective virus, we conducted quantitative coculture assays to determine the frequency of cells carrying replication-competent HIV. When standard quantitative coculture assays (up to 1x106 cells) were used, no replication-competent HIV could be detected from the CD4+ T cells of the elite controllers. Subsequently, large numbers of CD4+ T cells (37-92 replicates of 10x106 cells per well, Online Table 1) of the elite controllers were subjected to high input quantitative coculture assays in order to determine the frequency of cells that could give rise to replication-competent virus. A dramatic decrease (>1 log) in the frequency of CD4+ T cells carrying replication-competent HIV was seen in 2 elite controllers (Subject 2 and 3) and 1 controller (Subject 4) following initiation of ART (Figure 1C and Online Table 1). In Subject 1, the reduction in the frequency of CD4+ T cells carrying replication-competent HIV at baseline
versus month 6 or month 9 was modest due in part to the fact that the baseline infectious HIV burden was extremely low in this subject and detecting a larger difference post ART would have required a prohibitive number of cells. The level of replication-competent HIV was below the
limit of detection in all study subjects during ART despite culturing extraordinarily large numbers of cells in replicate (average of 62 wells containing 10x106 cells per well). In contrast to Subject 1, the cultures from Subject 2, 3, and 4 had readily detectable levels of replication competent HIV at baseline and three months following cessation of ART (Online Table 1). Of note, the infectious HIV burden returned to the pre-therapy level in all study subjects 3 months following discontinuation of ART (Figure 1C and Online Table 1). Although testing for statistical significance was not performed due to the small sample size, the mean log10 decrease (month 0 vs. month 9) and increase (month 9 vs. month 12) of the infectious HIV burden were - 1.2938 and +1.3379, respectively, clearly demonstrating that ART had an impact on the size of the pool of infected CD4+ T cells carrying replication-competent HIV in the study subjects.
The half-lives of the HIV reservoir during the treatment period (month 0, 6, and 9) in Subject 1, 2, 3 and 4 were 16.93, 2.06, 2.12, and 1.01 months, respectively. Of note, short half-lives (<4 months) of the viral reservoir had been reported in previous studies involving HIV-infected individuals who initiated ART during the acute/early phase of infection [9]. Frequencies of CD4+ T cells in the blood carrying HIV DNA were measured but no significant changes were observed in the elite controllers (Online Figure 1), possibly due to the fact that the vast majority of infected CD4+ T cells carry replication-defective HIV. In addition, levels of immune activation (T cells expressing CD38 and HLA-DR) were evaluated in the blood and sigmoid colon and found to be decreased during ART and returning to pre-ART levels following discontinuation of therapy in three of the four subjects studied (Online Figure 2). Finally, we investigated the impact of ART on the frequency of HIV-specific CD8+ T cells in the blood of the three elite controllers. As shown in Figure 1D, the frequency of HIV-specific CD8+ T cells expressing intracellular IFN-y and MIP-1ß decreased during the treatment period and levels remained low to undetectable following cessation of ART in all three individuals.
DISCUSSION
Despite the remarkable success of ART in controlling plasma viremia and recent advances in our understanding of the pathogenesis of HIV, the prospect for eradication of HIV by standard ART alone remains challenging [2]. Given the considerable difficulties of achieving a complete eradication (sterilizing cure) of HIV in a large proportion of infected individuals, immune-based strategies aimed at achieving containment of viral replication in infected individuals in the absence of ART represent more realistic and feasible avenues. In this regard, the unique ability of elite controllers to suppress plasma viremia and maintain normal CD4+ T cell counts for years to decades in the absence of ART has served as a model for achieving a 'functional' cure. To this end, it is critical to understand the dynamics of HIV reservoirs and the interplay between the virus and the host immune system in elite controllers. In the present study, we used the modulation of virologic and immunologic parameters by ART to provide evidence that ongoing/residual HIV replication does, in fact, occur in individuals who had been controlling their plasma viremia in the absence of ART.
We demonstrated that a short course of ART dramatically decreased the infectious HIV burden in elite controllers, providing compelling evidence that residual viral replication occurs in such individuals in the absence of therapy. Recent studies have suggested that on-going/residual HIV replication may be absent in infected individuals receiving ART as long as undetectable levels of plasma viremia (<50 copies) are maintained [10], although other studies have suggested otherwise [11, 12]. In addition, it has been suggested that residual plasma viremia fluctuates over time in elite controllers [4, 5, 13] although the clinical significance of such events and residual plasma viremia in general have not been fully delineated to date. Of note, previous studies have shown that initiation of ART in elite controllers led to decreases in the level of immune activation [14] and increases in CD4+ T cell counts [15] although the size of the pool of CD4+ T cells carrying replication-competent HIV was not determined in these studies. Our data suggest that on-going/residual viral replication can occur in infected individuals in the absence of detectable plasma viremia and indicate that one virologic marker (plasma viremia) alone may not accurately reflect the dynamics of HIV replication in vivo. While, the mechanism by which ART reduced the frequency of CD4+ T cells carrying replication-competent HIV is unclear, it is conceivable that the presence of ART inhibited bystander CD4+ T cell infection and/or induced transient lymphocyte redistribution.
Interestingly, the infectious HIV burden in the CD4+ T cell compartment of the elite controllers rebounded back to their original baseline levels upon cessation of ART, an indication that a virologic 'set-point' exists even at this very low level of viral replication, and that host immunity can efficiently control clinically relevant plasma viremia without completely blocking viral replication or completely eliminating the infected CD4+ T cells that are the source of this residual viral replication. We also demonstrated that the level of HIV-specific CD8+ T cells in elite controllers gradually declined upon initiation of ART, further supporting the virology evidence that low levels of viral replication occur in these infected individuals. It is unclear why the levels of HIV-specific CD8+ T cells did not return to baseline within the observed time frame following discontinuation of therapy although possible explanations include elimination of viral antigens during the period of ART and/or bystander cellular activation of CD8+ T cells after cessation of therapy. Long-term immunologic and virologic studies involving larger numbers of elite controllers, including non-HLA-B5701+ individuals should be conducted to strengthen and confirm our findings.
In summary, we demonstrated that ART results in a marked diminution of the number of infected CD4+ T cells carrying replication-competent HIV in elite controllers, suggesting that low levels of ongoing viral replication contributes to the maintenance of HIV reservoirs in the absence of detectable plasma viremia.
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