CHIP-Seq analysis of CREB1 binding after ALVAC vaccination in Human PBMC

The RV144 HIV vaccine trial remains the only study to demonstrate significant protection from future HIV-1 acquisition. One of the key components of the RV144 vaccine was the use of the canarypox vector ALVAC as the priming component. Since AIDSVAX, the booster component, alone failed to provide protection we hypothesized that the ALVAC prime contributed significantly to the generation of protection. To test this, we designed a NHP immunogenicity trial to mechanistically link ALVAC vaccination with the magnitude of V1V2 titers, the most significant immune correlate of reduced HIV-1 acquisition in RV144. Our objective was to use a systems biology approach to identify the transcription factors, target genes and immune pathways which were being induced by ALVAC vaccination and associated with higher V1V2 titers. We identified the transcription factor CREB1 and its target genes as rapidly induced by ALVAC in multiple immune subsets and that CREB1 drives the expression and activation of a network of other TFs which are critical for modulating immune responses. Pathways induced by this ALVAC-CREB1 axis include lymphocyte/leukocyte migration, lymphocyte differentiation, antigen processing and presentation, T cell co-stimulation and cytokine signaling. PBMCs were infected in vitro with an MOI 10:1 of ALVAC-HIV, with media cultured cells as a control. ALVAC-infected PBMCs were compared with media condition at 24 hours after CREB1 chromatin immunoprecipitation.

RV144型艾滋病病毒（HIV）疫苗临床试验是目前唯一被证实可显著降低未来HIV-1型感染风险的研究。RV144疫苗的核心组分之一为以金丝雀痘载体ALVAC作为初免组分。由于单独使用加强免疫组分AIDSVAX无法提供保护，我们推测ALVAC初免在保护效力的产生中发挥了关键作用。为验证这一推测，我们设计了一项非人类灵长类（non-human primate, NHP）免疫原性试验，以在机制层面关联ALVAC疫苗接种与V1V2抗体滴度水平——V1V2滴度是RV144试验中与HIV-1型感染风险降低关联最显著的免疫相关性标志物。本研究的目标为通过系统生物学方法，鉴定ALVAC疫苗接种所诱导、且与更高V1V2滴度相关的转录因子、靶基因及免疫通路。我们发现，转录因子CREB1及其靶基因可在多种免疫亚群中被ALVAC快速诱导，且CREB1可驱动一系列其他转录因子（Transcription Factor, TF）的表达与激活——这些转录因子对调控免疫应答至关重要。该ALVAC-CREB1信号轴所诱导的通路包括淋巴细胞/白细胞迁移、淋巴细胞分化、抗原加工提呈、T细胞共刺激及细胞因子信号传导。我们以感染复数（Multiplicity of Infection, MOI）10:1的ALVAC-HIV体外感染外周血单个核细胞（Peripheral Blood Mononuclear Cell, PBMC），并以仅含培养基的培养细胞作为对照。在CREB1染色质免疫共沉淀（Chromatin Immunoprecipitation, ChIP）完成后的24小时，我们将ALVAC感染的PBMC与培养基对照组进行了比较分析。