CROI 2018 Abstract eBook

Abstract eBook

Poster Abstracts

Methods: PTCs were identified from the AIDS Clinical Trials Group (ACTG) studies, the Montreal Primary HIV Infection cohort, the Seattle Primary Infection Program, and the Ragon HIV Controllers cohort. PTCs were defined as individuals who underwent TI and maintained VLs ≤400 copies/mL at ≥2/3 of the time points for at least 24 weeks. Viral load and CD4+ dynamics were compared between PTCs and post-treatment non-controllers (NCs) from ACTG TI trials who received no immunologic intervention and exhibited loss of viral control post-TI. Results: A total of 58 PTCs were identified. PTCs were more commonly identified in those treated during early infection compared to those treated during chronic infection (11.6% vs. 4.4%, Fishers exact P=0.006). The median duration of documented viral control for the PTCs was 96 weeks. For participants treated during early infection, there was no significant difference between the highest reported pre-ART VL for the PTCs vs. NCs (median 4.6 vs. 4.7 log 10 copies/ mL). Over 24 weeks of TI, CD4+ counts were generally preserved in PTCs, but declined significantly in NCs (median +4 vs. -200 CD4+ cells/mm 3 , P<0.001). A VL ≥1000 copies/mL within the first 24 weeks was commonly seen in the PTCs: 24% of PTCs had a peak post-TI VL of 1000-9,999 copies/mL and 10% of PTCs had a peak VL ≥10,000 copies/mL. In those with post-TI VL peak ≥1000 copies, the median VL decline was 1.0 log 10 over the subsequent 2 weeks (range 7-15 days). Conclusion: PTCs were more frequently identified in those treated during early HIV infection and post-treatment control was associated with preserved CD4+ counts over the first 24 weeks. TI trials that restart ART at the 1,000 copy/mL VL threshold will miss 1/3 of PTCs, while trials that use a 10,000 copy/mL threshold will miss 10% of PTCs. Even in PTCs with peak post-TI VLs ≥1000 copies/mL, viral control was achieved relatively rapidly. 232LB TARGETING HIGHLY NETWORKED CTL EPITOPES AS A MECHANISM OF ELITE HIV-1 CONTROL Gaurav D. Gaiha 1 , Elizabeth Rossin 2 , Christian Landeros 1 , Itai Muzhingi 1 , Chioma A. Nwonu 1 , Bruce D. Walker 1 1 Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA, 2 Broad Institute of MIT and Harvard, Cambridge, MA, USA Background: Evaluation of cytotoxic T lymphocyte (CTL) epitopes by sequence-based methods such as amino acid (AA) conservation has not yielded a specific set of targets that confer elite HIV-1 control, in large part due to the lack of evidence linking sequence conservation to viral fitness cost. As a result, it has been challenging to leverage insights from elite controllers to generate a rationally designed T cell-based vaccine for the population at-large. In this study, we utilized a new approach - known as structure-based network analysis (SNA) - that systematically evaluates protein structure to define residues of structural and functional importance. Our hypothesis is that highly networked AAs identified by SNA would incur a viral fitness cost if mutated, and also be enriched in CTL epitopes targeted by elite controllers. Methods: Relying on structural data rather than sequence data, SNA builds networks of non-covalent interactions between AA side chains, and quantifies the sum contribution of each residue to the protein’s global structure assigned as an AA network score. Applying this approach to all available crystal structures for HIV-1 allowed us to quantitate network scores for 71% of the entire HIV proteome and 86% of reported optimal CTL epitopes. Results: Correlation of network scores with viral sequence entropy values revealed a strong negative association (P<0.001), but also identified multiple sequence conserved residues that were poorly networked. In vitro mutagenesis of conserved residues with high and low network scores revealed a differential mutational sensitivity (P<0.0001), with only disruption of highly networked residues leading to impaired HIV infectivity. Assessment of proliferative CTL responses in 134 HIV+ individuals also revealed a strong enrichment of highly networked residues in epitopes targeted by persons who spontaneously control HIV (P<0.001). Moreover, plasma viral sequencing revealed markedly reduced mutation rates specifically in highly networked epitopes, despite robust CTL targeting. Importantly, networked epitopes identified by SNA were found in both controller (e.g. B*5701) and non-controller HLA alleles. Conclusion: These findings demonstrate the superior ability of SNA to define fitness-constrained residues and implicate targeting highly networked epitopes by CTLs as a putative mechanism of immune control across diverse HLA. Application of this approach provides a rational framework for the design of a broadly applicable T cell-based vaccine for HIV-1.

233LB WOUND HEALING MECHANISMS REQUIRED IN PATHOGENESIS CONTROL OF SIV IN NATURAL HOST Fredrik Barrenas 1 , Kevin D. Raehtz 2 , Lynn Law 3 , Richard Green 3 , Guido Silvestri 4 , Steven E. Bosinger 4 , Qingsheng Li 5 , Matthew Thomas 3 , Jean Chang 3 , Elise Smith 3 , Reem A. Dawoud 4 , Cristian Apetrei 2 , Ivona Pandrea 2 , Michael Gale 3 1 Uppsala University, Uppsala, Sweden, 2 University of Pittsburgh, Pittsburgh, PA, USA, 3 University of Washington, Seattle, WA, USA, 4 Emory University, Atlanta, GA, USA, 5 University of Nebraska–Lincoln, Lincoln, NE, USA Background: Protracted inflammation is a primary driver of HIV pathogenesis. Several African non-human primates (NHPs) remarkably avoid AIDS despite lifelong infection with SIV, and mucosal CD4+ cell depletion. Comparative pathogenesis studies between natural SIV hosts and AIDS-susceptible NHP species can reveal disease mechanisms and treatment targets. Also, NHP studies enable close examination of the first virus-host interactions, showing how the natural and pathogenic host responses diverge. Methods: We devised a systems biology approach to investigate the early host response to high-dose rectal SIV transmission, by transcriptomic comparative analysis of a natural reservoir host SIV model species, African green monkeys (AGMs – Chlorocebus sabaeus, N=28) and a pathogenic model, rhesus macaques (RMs - Macaca mulatta, N=24). Serial necropsies were performed at time points as early as one-day post-infection, and RNA-Seq was performed on rectal tissues for both AGMs and RMs. Results: To explore diverse aspects of acute SIV infection, we created a functionally annotated co-expression network. Innate immune response, representing an early response to SIV infection, were activated earlier in the AGMs, and closely associated with induction and response to type I and III interferons. By contrast, the RM response included general immune activation, including anti-bacterial, LPS-driven responses. The AGM response was concomitant with rapid activation of wound healing processes and epithelial remodeling. RMs, by contrast, activate the inflammatory stage response to wounding, but lack tissue remodeling gene activation. This response included a significant TGF-β signature. IHC confirmed preserved expression of epithelial wound healing protein FN in AGMs, but not RMs. Using RNA-Seq, we found overexpression of several key regulators of wound healing in sorted monocytes from AGMs, compared to RMs. This overexpression was present before SIV challenge, suggesting that natural hosts are constitutively poised to resist SIV pathogenesis. Conclusion: These results show that the response to SIV infection in natural and pathogenic host organisms diverge during the early acute stage. Natural hosts activate antiviral immune responses that favor wound healing, and avoid tissue damage from excessive inflammation. 234 PERSISTENT DYSREGULATION OF HIV-SPECIFIC T FOLLICULAR HELPER CELLS DURING ART Julia Niessl 1 , Amy E. Baxter 1 , Antigoni Morou 1 , Elsa Brunet-Ratnasingham 1 , Madelene Lindqvist 2 , Parsia A. Vagefi 3 , Eileen P. Scully 2 , Jean-Pierre Routy 4 , Daniel E. Kaufmann 1 1 Université de Montréal, Montreal, QC, Canada, 2 Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA, 3 Massachusetts General Hospital, Boston, MA, USA, 4 McGill University, Montreal, QC, Canada Background: Germinal center follicular T helper cells (GC Tfh) provide B cell help to support high affinity antibody responses. HIV infection leads to impairment of GC Tfh and their circulating counterpart (circulating Tfh, cTfh) contributing to inefficient humoral response to HIV. Tfh impairment persists in HIV-infected subjects on antiretroviral therapy (ART) despite viral control. Due to technical limitations in assessing antigen (Ag)-specific Tfh, previous studies on mechanisms of Tfh impairment have been restricted to bulk Tfh. Therefore, it remains unclear if this Tfh dysfunction is HIV-specific or reflects a global dysregulation of the Tfh compartment. Methods: Here, we used co-expression of the surface activation-induced markers CD40L and CD69 after Ag stimulation to identify HIV-specific CD4 independently of their functional profile. We studied blood of HIV+ subjects on ART and compared phenotype and function of the CD4 responses specific to HIV Ags (Gag, Env, Nef) to those specific for another chronic but controlled virus (CMV) and to responses to a resolved infection or vaccine (HBV) within the same donors. Results: We observed a preferential expansion of cTfh within HIV-specific CD4 responses when compared to CMV and HBV. In contrast to non-cTfh cells and to all other Ags tested, Gag-specific cTfh exhibited an increased CXCR3+ Th1-like

Poster Abstracts

82

CROI 2018