CROI 2017 Abstract e-Book

Abstract eBook

Oral Abstracts

46 VISUALIZING PERSISTENT HIV IN CLINICAL SAMPLES Daniel E. Kaufmann, Univ of Montreal, Montreal, QC, Canada

HIV cure efforts are hampered by limited characterization of the cells supporting HIV replication in vivo and inadequate methods for quantifying the latent viral reservoir in individuals receiving antiretroviral therapy (ART). To overcome these limitations we developed a highly specific and sensitive flow-FISH (fluorescence in situ hybridization) assay that allows for the simultaneous detection of HIV-1 transcription and translation (HIV-1 RNA+/Gag+ CD4 T cells), in conjunction with phenotypic markers in peripheral blood. The HIV RNA/Gag method is 1,000-fold more sensitive than Gag protein staining alone, with a detection limit of 0.5-1 gag-pol mRNA+/Gag protein+ infected cells per million CD4 T cells. We will present how we used this technique to quantify CD4 T cells maintaining both the ongoing infection in untreated individuals and the inducible reservoir in ART- suppressed subjects. We will illustrate the power of this technology by single-cell phenotypic analyses of translation-competent reservoirs in primary blood samples. To exemplify potential applications for HIV cure research, we will present data on latently infected cells capable of producing HIV mRNA and protein after stimulation with PMA/ionomycin and latency reversing agents (LRAs). We will show qualitative differences in the patterns of reactivation obtained by specific LRAs. We will outline some recent developments of this technology that can be applied to a broad array of research questions. 47 CHARACTERIZING HIV EXPRESSION IN VIVO Mary F. Kearney, NCI, NIH, Frederick, MD, USA HIV proviruses persist in vivo in latent and transcriptionally active forms. Little is known regarding the fraction of infected cells in blood and in tissues that are quiescent versus those that actively express HIV RNA in either ART treated or untreated individuals, although it is known that the majority of proviruses are defective for viral replication due to deletion or hypermutation. It is thought that cells expressing HIV, defective or not, are susceptible to cell killing by cytopathic effects or immune responses. It stands to reason, therefore, that long-lived latently-infected cells may accumulate over the course of HIV infection and persist after ART is initiated. Indeed, many studies have demonstrated the persistence of latently-infected cells during ART and, it is believed that such cells, when activated, are the source of viral rebound when ART is interrupted. However, it has been reported that HIV-expressing cells in lymph nodes may be protected from the cytotoxic T-cell immune response, and therefore, may persist during ART despite HIV expression and, therefore, may be the primary source of viral rebound when treatment is stopped. It was also recently discovered that HIV infected T-cells can persist in vivo through cellular proliferation, which occurs both prior to and during ART. In one case thus far, a highly expanded infected CD4+ T cell clone was shown to be the source of persistent infectious viremia during ART, demonstrating that at least some members within clones can express HIV RNA and produce virus particles. This talk will summarize emerging data from studies investigating the fraction of HIV infected cells that express HIV RNA in blood and tissues both prior to and during ART and the fraction of HIV expressing cells within cell clones, including those carrying replication-competent proviruses. Understanding the fractions of viral RNA expressing cells and levels of HIV RNA expressed by them during ART will lead to a better understanding of the HIV reservoir, the nature of latency, and the sources of rebound viremia when ART is interrupted. 48 IMMUNE-BASED INTERVENTIONS TARGETING INFLAMMATION AND VIRAL PERSISTENCE Mirko Paiardini, Emory Univ Sch of Med, Atlanta, GA, USA Antiretroviral therapy (ART) suppresses viral replication in HIV-infected individuals, but does not eliminate an extremely durable reservoir of latently infected cells that is established early after infection. Consequently, discontinuation of ART typically leads to rapid rebound of plasma viremia Understanding the phenotype and location of latently infected cells represents a critical challenge in designing a cure for HIV; furthermore, many HIV-infected individuals given ART exhibit residual inflammation, which is associated with non-AIDS-related morbidity and mortality and may contribute to virus persistence. In this context, there is a strong consensus that a cure for HIV infection will not be achieved through ART intensification alone, and that novel approaches aimed at limiting residual inflammation and targeting persistently infected cells are needed. This presentation will discuss state-of-the-art concepts and immune based strategies targeting HIV persistence developed over the past several years using the model of SIV infection in rhesus macaques (RMs). Collectively, these studies support a model in which among memory CD4+ T-cells, those expressing co-inhibitory receptors (Co-IRs) are enriched in latent HIV. Recent work identified PD-1+ follicular helper CD4+ T-cells as an important cellular compartment for viral persistence. We have described that CTLA-4+PD-1- memory CD4+ T-cells, which share phenotypic markers with regulatory T-cells and localize outside the B-cell follicle of the lymph nodes, are significantly enriched in SIV-DNA; contain robust levels of replication-competent virus; and significantly increase their contribution to the SIV reservoir with prolonged ART. Finally, we showed that Interleukin-21 administration in ART-treated, SIV-infected RMs reduces residual inflammation in blood and intestinal mucosa, which is in turn associated with diminished viral persistence during ART. These recent advancements highlight the complexity and diversity of the mechanisms and T-cell populations that can contribute to the residual reservoirs of virally infected cells. Understanding this complexity and developing a range of different interventions to target individual components of viral reservoirs represent both a formidable challenge and an exciting opportunity for the years to come. 49 THERAPEUTIC VACCINATION FOR HIV/SIV: WHAT WILL IT TAKE FOR CURE? Louis J. Picker, Oregon Hlth & Sci Univ, Beaverton, OR, USA Current understanding of the residual virus remaining in HIV-infected subjects on optimally effective antiretroviral therapy (ART) suggests that functional HIV cure will require either viral eradication or substantial viral reservoir reduction combined with potent, long-term anti-viral immunity such that any viral reactivation that occurs after ART cessation is eliminated or stringently controlled over a lifetime. Achieving this state might entail up to 4 mechanistically distinct interventions, including 1) induction of viral gene expression in the transcriptionally “quiescent”, latent HIV reservoir (allowing for immune targeting of these infected cells), 2) targeted immune destruction of all cells expressing HIV gene products, 3) establishment of a long-term potently antiviral immune response for immune surveillance after ART cessation, and 4) elimination of immunologic sanctuaries, such as the B follicular barrier for infected CD4+ T follicular helper T cells, that shield virally infected cells from immune destruction. Given the unproven benefits and potential risks of such interventions, there is a great need for an animal model that can be used for concept development and both pre-clinical safety and proof-of-concept studies. Our group has invested significant effort and resources in developing appropriate, state-of-the-art nonhuman primate models for such studies. In this talk, I will review the progress made in these models to both understand the immunobiology of ART-suppressed SIV infection and post-ART viral recrudescence and to develop therapeutic vaccination strategies that counter viral persistence and post-ART viral rebound. 50 MDR-TB EPIDEMIOLOGY AND TRANSMISSION N. Sarita Shah, CDC, Atlanta, GA, USA Drug-resistant tuberculosis (TB) is a global public health crisis, with 480,000 cases occurring annually and 190,000 dying of this disease. Extensively drug-resistant (XDR) TB involves resistance to the most potent first-line and second-line drugs to treat TB and has been reported from over 100 countries. Although the End TB Strategy calls for universal access to drug-susceptibility testing (DST), less than one-third of bacteriologically-confirmed TB cases had DST done, leading to massive diagnostic gaps. Among those diagnosed with MDR-TB, inadequate access to second-line TB drugs – in part due to bottlenecks created by centralized models of MDR-TB care – result in large treatment gaps. Current treatment regimens for MDR-TB are lengthy (minimum 18-24 months), costly (10-15 times the cost of drug-susceptible TB), have numerous side effects and result in cure for less than 50% of patients. Taken together, these major shortfalls in diagnosis, treatment and outcomes create a perfect storm for perpetuating the cycle of MDR-TB transmission and epidemic spread. Although transmission of MDR-TB strains has been well-described in outbreak settings for decades, the role of transmission in widespread epidemics is less understood. Characterizing the role of transmission is critical for informing public health interventions which, until now, have focused primarily on preventing acquired resistance (though the DOTS strategy) and far less on preventing transmission (through infection control strategies). In settings that have begun to address transmission prevention, efforts

Oral Abstracts

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CROI 2017