A long-term stable cold-chain-friendly HIV mRNA vaccine encoding multi-epitope viral protease cleavage site immunogens inducing immunogen-specific protective T cell immunity

The lack of success in clinical trials for HIV vaccines highlights the need to explore novel strategies for vaccine development. Research on highly exposed seronegative (HESN) HIV-resistant Kenyan female sex workers revealed naturally protective immunity is correlated with a focused immune response mediated by virus-specific CD8 T cells. Further studies indicated that the immune response is unconventionally focused on highly conserved sequences around HIV viral protease cleavage sites (VPCS). Thus, taking an unconventional approach to HIV vaccine development, we designed lipid nanoparticles loaded with mRNA that encodes multi-epitopes of VPCS (MEVPCS-mRNA LNP), a strategic design to boost antigen presentation by dendritic cells, promoting effective cellular immunity. Furthermore, we developed a novel cold-chain compatible mRNA LNP formulation, ensuring long-term stability and compatibility with cold-chain storage/transport, widening accessibility of mRNA LNP vaccine in low-income countries. The in-vivo mouse study demonstrated that the vaccinated group generated VPCS-specific CD8 memory T cells, both systemically and at mucosal sites of viral entry. The MEVPCS-mRNA LNP vaccine-induced CD8 T cell immunity closely resembled that of the HESN group and displayed a polyfunctional profile. Notably, it induced minimal to no activation of CD4 T cells. This proof-of-concept study underscores the potential of the MEVPCS-mRNA LNP vaccine in eliciting CD8 T cell memory specific to the highly conserved multiple VPCS, consequently having a broad coverage in human populations and limiting viral escape mutation. The MEVPCS-mRNA LNP vaccine holds promise as a candidate for an effective prophylactic HIV vaccine.

HIV疫苗临床试验屡屡受挫，凸显了探索新型疫苗研发策略的迫切需求。针对肯尼亚女性性工作者中的艾滋病毒高暴露血清阴性（HESN）群体的研究显示，天然保护性免疫与病毒特异性CD8阳性T细胞介导的靶向免疫反应密切相关。后续研究进一步表明，该免疫反应非常规地聚焦于HIV病毒蛋白酶切割位点（VPCS）周围的高度保守序列。基于此非常规研发思路，我们设计了搭载编码病毒蛋白酶切割位点多表位信使RNA（mRNA）的脂质纳米颗粒（LNP）——即MEVPCS-mRNA LNP，该策略旨在增强树突状细胞的抗原呈递能力，从而诱导有效的细胞免疫。此外，我们开发了一种新型冷链兼容型mRNA LNP制剂，可实现长期稳定储存与运输，大幅提升mRNA LNP疫苗在低收入国家的可及性。体内小鼠实验结果显示，免疫组不仅在全身循环中，还在病毒入侵的黏膜部位均产生了VPCS特异性CD8记忆T细胞。MEVPCS-mRNA LNP疫苗诱导的CD8 T细胞免疫与HESN群体的免疫特征高度相似，且呈现多功能表型。值得注意的是，该疫苗仅诱导极微弱甚至无CD4阳性T细胞活化。这项概念验证研究证实，MEVPCS-mRNA LNP疫苗有望诱导针对高度保守的多VPCS的CD8 T细胞记忆免疫，进而实现人群广谱覆盖并限制病毒逃逸突变，有望成为一款高效的预防性HIV疫苗候选产品。