CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

Conclusions: The pattern of epitope recognition and antigen binding in the response to HIV-1 JR-FL gp140, in part, is on D H sequence may underlie some of the difficulty that patients experience in HIV-1 neutralizing antibody. 356 Human Rhinovirus Displaying HIV-1 4E10 Epitope Elicits Broad Neutralization in hICAM-1 Tg Mice Guohua Yi 1 ; XiongyingTu 2 ; Preeti Bharaj 1 ; Premlata Shankar 1 ; Manjunath Swamy 1 1 Texas Tech University Health Sciences Center, El Paso, TX, US; 2 University of Minnesota, St Paul, MN, US natural selection of D H

gene segment sequence. Restrictions imposed by

Background: Induction of bnAbs remains a critical goal towards developing a vaccine against HIV-1. We previously grafted 4E10 epitope of HIV-1 gp41 on the surface of human rhinovirus connected via linkers of varying lengths and sequences to construct combinatorial HRV display libraries. One chimeric HRV:HIV immunoselected from the libraries was able to elicit broad neutralization against 10 of 12 HIV-1 pseudoviruses in guinea pigs. However, guinea pigs do not get infected with HRV because they lack the viral receptor, human ICAM-1 and thus the antibody titers were rather modest. Since the recently developed hICAM-1 Tg mice support productive HRV infection, in this study we evaluated the efficacy of chimeric HRV:HIV vaccine in these mice. Methods: hICAM Tg mice were intranasally immunized with three representative chimeric HRV:HIV viruses chosen from our previous study. The sera collected at different time points were tested for immunogenicity and HIV neutralization. ELISA was used to test the binding affinity against 4E10 peptide as well as HIV-1 gp140 trimer. The neutralizing ability against HIV-1 isolates was tested by single-round Tat-regulated luciferase assay in TZM-bl cells. Also, 11 HIV-1 internationally circulating isolates of diverse subtypes and coreceptor usages were used to test the breadth of neutralizing ability. HRV pre-immunized Tg mice were further immunized with chimeric HRV:HIV to test whether nasal administration can bypass HRV pre-immunity. Results: The sera from the immunized mice showed good binding affinity with 4E10 peptide as well as with HIV-1 gp140 trimer. All three chimeric HRV:HIV elicited neutralizing antibody responses in hICAM-1 Tg mice against diverse isolates of HIV-1, with one eliciting anti-HIV antibodies capable of neutralizing 9 of the 11 internationally circulating HIV-1 isolates at IC50 level (from six subtypes and two co-receptor usages of HIV-1). Furthermore, intranasal administration of chimeric HRV:HIV could bypass the preexisting immunity to HRV to elicit anti-HIV response. Conclusions: This work demonstrates that productive infection of HRV susceptible animals with chimeric HRV effectively elicits broadly neutralizing anti-HIV-1 antibodies. This strategy therefore appears to have potential for human vaccination. 357 WITHDRAWN 358 A Superagonist Antibody to Human Interleukin-21 Increases HIV-Specific T-Cell Function Yew Ann Leong 1 ;Yanfang Cui 1 ; Zhian Chen 1 ; FionaWightman 1 ; Pellegrini Marc 2 ; Jamie Rossjohn 1 ; Sharon R. Lewin 3 ; Alan Landay 4 ; Charles Mackay 1 ; DiYu 1 1 Monash University/Alfred Hospital, Melbourne, Australia; 2 Walter and Eliza Hall Institution, Melbourne, Australia; 3 University of Melbourne, Melbourne, Australia; 4 Rush University Medical Center, Chicago, IL, US; 5 Monash University/Alfred Hospital, Melbourne, Australia Background: Interleukin-21 (IL-21) is an immunostimulatory cytokine showing promising results in phase II clinical trials for cancer immunotherapy. IL-21 also enhances anti-viral immunity in HIV/SIV infections. It is a suitable candidate that can be targeted by the kick and kill strategy to boost immunity to eliminate HIV. This study focused on developing an agonistic monoclonal antibody (mAb) to human IL-21 (hIL-21) that enhances the anti-viral function of hIL-21. Methods: A hIL-21-dependent Ba/F3 cell line proliferation assay was used to screen a library of anti-hIL-21 mAbs to identify agonistic clones. Binding of the agonist mAb to hIL-21 was characterized by Surface Plasmon Resonance (SPR) and crystallography. To test the anti-HIV function of the mAb, peripheral blood mononuclear cells (PBMCs; n=5) from HIV infected patients on antiretroviral therapy (ART>3 years, CD4 + T-cell count>500/ m L, viral load<50 copies/mL) were stimulated with MHC-I-restricted gag peptides in the presence of hIL-21 and the mAb. Cytotoxicity of natural killer (NK) and CD8 + T cells were analyzed by measuring intracellular granzyme B and perforin expression by flow cytometry (FACS). The phamacokinetics and phamacodynamics of the mAb were studied in mice humanized with hIL-21 and the hIL-21 receptor (hIL-21R) and infected with lymphocytic choriomeningitis virus (LCMV). Bioavailability (BA) of hIL-21 with the mAb was measured by enzyme-linked immunosorbent assay. Agonistic effect of mAb was determined by quantifying virus-specific CD8 + T-cell response by FACS and viral load by plaque assay. Results: We identified a mAb SG1 that enhanced hIL-21’s activity ≥ 10 folds in the Ba/F3 cell proliferation assay. It bound to hIL-21 with an affinity of 7.1E-11(K D ). Crystal structure and protein docking stimulation revealed that SG1 changed the conformation of hIL-21 to suit its binding to the receptor. In cultured PBMCs from HIV-infected patients, SG1 significantly increased the cytotoxicity of NK and CD8 + T cells by 5-10 folds. In the chronic LCMV infection, SG1 increased the BA of hIL-21 >50 folds. An enhanced generation of functional virus-specific CD8+ T cells led to early resolution of the infection. Conclusions: The high-affinity mAb SG1 has a unique function to enhance hIL-21’s activity by changing its conformation and increasing the BA in vivo . Superagonist mAb SG1 promotes the anti-viral function of hIL-21 in vitro and in vivo . SG1 might be used in a kick and kill approach to eliminate HIV latency.

Poster Abstracts

THURSDAY, FEBRUARY 26, 2015 Session P-E4 Poster Session

Poster Hall

2:30 pm– 4:00 pm Cellular Immune Response to HIV 359 Evolution of HIV-Specific CD8+ T-Cell Responses in Hyperacute HIV Infection Zaza M. Ndhlovu 1 ; Nikoshia Mewalal 1 ; Philomena Kamya 1 ;Thandeka Nkosi 1 ; Karyn Pretorius 1 ; Nasreen Ismail 1 ; Amber Moodley 2 ; Krista Dong 2 ;Thumbi Ndung’u 1 ; BruceWalker 2 1 University of KwaZulu-Natal, Durban, South Africa; 2 Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, US Background: CD8 + T cells suppress HIV replication, but the relationship to initial onset of plasma viremia has not been well defined since acute infections are rarely identified prior to peak viremia. Moreover, pre-infection samples are rarely available. Methods: To address evolving viral and T cell dynamics from the onset of plasma viremia, hyperacute cases of HIV infection were identified by biweekly HIV RNA screening of plasma from high risk uninfected women in KwaZulu-Natal, South Africa, as part of a comprehensive HIV prevention program. Pre-infection and post infection blood samples were evaluated in 12 subjects identified with initial viral load as low as 140 RNA copies/ml plasma. Assays performed on fresh and/or cryopreserved cells included intracellular cytokine staining (Ki67, Bcl-2, CD38, HLA-DR, CD107a, IFN-g, TNF-a and IL-2) as well as IFN-g ELISPOT and class I tetramer staining.

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