CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

ribosome display selection rounds. The resulting sub-libraries were screened by binding ELISA and pseudovirus neutralization assay. Epitopes were mapped by alanine-scan and characterized by competition ELISA. Results: Focusing selection of DARPins on the V3 loop using a structurally arrested V3 mimetic proved to be successful. The selected DARPins varied in their binding preference for specific V3 structures and most importantly, showed different degrees of neutralization breadth. As the panning targets were of subtype B origin, the neutralization activity of DARPins was mostly restricted to this subtype. This was improved using the 2nd generation DARPin library, fromwhich we selected a novel type of V3 DARPin with broad neutralization capacity. DARPin 13.2 G10 neutralizes 62.5% of pseudoviruses out of 32 viruses from 5 different clades. Conclusions: The structurally arrested V3 mimetic proved to be a valuable tool to focus the selection of DARPin clones to V3 and to derive a broadly active entry inhibitor. This result opens novel opportunities for selecting HIV-1 inhibitory DARPins specific for different epitopes.

WEDNESDAY, FEBRUARY 25, 2015 Session P-E3 Poster Session

Poster Hall

2:30 pm– 4:00 pm New Approaches to Immunostimulation

352 Use of Pre-ART-Adjusted Endpoints in the Analysis of an HIV Therapeutic Vaccine Trial Yunda Huang 1 ; Lily Zhang 1 ; Darren Jolliffe 3 ; Arnt-Ove Hovden 4 ; Mats Okvist 4 ; Pantaleo Giuseppe 2 ; Maja A. Sommerfelt 4

1 Fred Hutchinson Cancer Research Center, Seattle, WA, US; 2 Lausanne University Hospital, Lausanne, Switzerland; 3 S-cubed Biometrics Ltd, Oxfordshire, United Kingdom; 4 Bionor Pharma ASA, Oslo, Norway Background: In one of the largest randomized, double-blind, placebo-controlled phase 2 therapeutic HIV vaccine clinical trials, Vacc-4x was found safe, well-tolerated and immunogenic. While on combination antiretroviral therapy (cART), 135 HIV-infected participants (vaccine: placebo = 92: 43) were randomized and received 4 weekly immunizations followed by booster immunizations at weeks 16 and 18. At week 28, cART was interrupted for up to 24 weeks. Based on the primary analyses, Vacc-4x did not significantly reduce the proportion of participants resuming cART or change in CD4 counts during the cART interruption. We assessed the vaccine effect based on additional exploratory endpoints. Methods: All analyses included per-protocol (PP) participants who received the full immunization and underwent cART interruption. Linear regression models were used to identify predictors of outcomes measured after cART interruption, and to estimate the vaccine effect adjusted for potential baseline confounding factors. We assessed vaccine effect based on four novel preART-adjusted clinical endpoints: fold changes in CD4 counts at week 40 or in the geometric mean of CD4 counts at weeks 48 and 52 over preART CD4 counts, and fold changes in viral load (VL) at week 40 or in the geometric mean of VL at weeks 48 and 52 over preART VL. We used a multiple imputation approach to account for missing CD4 counts or VL due to cART resumption or dropout. Results: PreART CD4 counts and VL were significant predictors of levels after cART interruption. A significant vaccine effect was observed in the analysis of all four preART- adjusted endpoints. Compared to the placebo recipients, the vaccine recipients had a higher fold change in week 40 CD4 counts (vaccine vs. placebo mean fold-change difference = 0.08; 95% CI 0.02, 0.15; p=0.02), a higher fold change in weeks 48/52 CD4 counts (0.07; 95% CI 0.01, 0.13; p=0.03), a lower fold change in week 40 VL (-0.46; 95% CI -0.88 to -0.04; p=0.03), and a lower fold change in weeks 48/52 VL (-0.44; 95% CI -0.86, -0.02; p=0.04). Conclusions: These exploratory analyses consistently suggested that Vacc-4x provided improved effect on preART-adjusted clinical endpoints for CD4 counts and VL over participants’ preART conditions. Future HIV therapeutic vaccine studies may adopt similar endpoints of fold changes over preART values to account for participants’ heterogeneity and to increase the statistical power of vaccine effect evaluations. 353 Decreased HIV-Specific T-Regulatory Responses Mark Effective Vaccine-Induced Immunity Vedran Brezar 1 ; Nicolas Ruffin 1 ; Laura Richert 2 ; Mathieu Surenaud 1 ; Christine Lacabaratz 1 ; Karolina Palucka 3 ; RodolpheThiebaut 2 ; Jacques Banchereau 1 ;Yves Lévy 1 ; Nabila Seddiki 1 1 Inserm U955 (Eq16)-UPEC-VRI, Créteil, France; 2 Univ Bordeaux-ISPED-Inserm U897-VRI, Bordeaux, France; 3 Ralph M. Steinman Center for Cancer Vaccines–Baylor Institute for Immunology Research, Dallas, TX, US Background: The role of regulatory T cells (Tregs) in vaccination has been poorly investigated. We have reported that vaccination with ex vivo -generated dendritic-cells (DC) loaded with HIV-lipopeptides (LIPO-5-DC vaccine) in HIV-infected patients was well tolerated and highly immunogenic. However, patients responded differently to vaccination. Here we hypothesized that the presence and/or induction of HIV-specific Tregs might explain this observation. Methods: Fourteen HIV-1 infected individuals under effective antiretroviral therapy have been included in this study. Patients received LIPO-5-DC vaccine every 4 weeks during 16 weeks period. Blood was drawn prior (week -4) and after (week 16) vaccination. This was followed by analytical treatment interruption (ATI) at week 24 to measure the magnitude of viral rebound. To assess the antigen-specific effectors (Teffs) and Tregs responses, a novel assay was used in which coexpression of CD25 and CD134 reveals these cells after stimulation in vitro . CD39 and FoxP3 markers were used to delineate antigen-specific Tregs and distinguish them from effector specific- responses. Results: Median LIPO-5-specific CD25 + CD134 + polyfunctional T cells increased from 0.1% (IQR 0-0.3) before vaccination (week -4) to 2.1% (IQR 1.1-3.9) at week 16 following 4 immunizations (P=0.001) and were inversely correlated with viral replication following ATI (r=-0.71, p=0.006). The frequency of LIPO-5-specific Tregs prior to vaccination was elevated, accounting for a median 69.3% (IQR 55.8-75.2) of LIPO-5-specific response. After vaccination, the frequency of HIV-specific Tregs decreased (from 69.3 at week -4 to 31.7% at week 16) and inversely correlated with the HIV-specific IFN γ -producing cells (r=-0.64, P=0.002). These Tregs are highly suppressive as their depletion prior to stimulation led to a further increase in IFN γ responses. Vaccinees who displayed lower levels of LIPO-5-specific CD4 + CD134 + CD25 + CD39 + FoxP3 + Tregs responded better to the vaccine as indicated by a negative correlation between LIPO-5-specific Tregs and post-vaccination immune score. Conclusions: We show that DC-vaccine skewed the HIV-specific response from regulatory to effector phenotype. Patients with lower magnitude of viral replication following ATI presented lower levels of HIV-specific Tregs. This underlies the role these cells play in HIV-infection and the necessity to take them into account for future vaccine trials. 354 Viral Reservoir Dynamics After Therapeutic Vaccination and cART Interruption Cristina Andres 1 ; Carmen Alvarez-Fernandez 1 ; Nuria Climent 1 ;Teresa Gallart 1 ; Montserrat Plana 1 ; Agathe Leon 1 ; Nicolas Chomont 2 ; Jose M. Gatell 1 ; Felipe Garcia 1 ; Sonsoles Sanchez-Palomino 1 1 Hospital Clinic, Barcelona, Spain; 2 Vaccine and Gene Therapy Institute, Port St Lucie, FL, US Background: We reported a decrease viral set-point of 1.2 log10 associated with an increase in HIV-1–specific T cell responses in HIV infected individuals receiving autologous myeloid derived dendritic cells (MDDC) pulsed with autologous heat-inactivated whole HIV. Here, we assessed changes in viral reservoirs during vaccinations and the dynamics of viral reservoir replenishment during cART interruption after immunizations.

Poster Abstracts

270

CROI 2015