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 <i>in-vivo</i> 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，凸显了探索疫苗研发新策略的迫切性。针对肯尼亚HIV抗性、高暴露血清阴性（highly exposed seronegative, HESN）女性性工作者的研究显示，天然保护性免疫与病毒特异性CD8 T细胞介导的靶向免疫反应密切相关。进一步研究表明，该免疫反应非常规地靶向HIV病毒蛋白酶切割位点（viral protease cleavage sites, VPCS）周围的高度保守序列。因此，本研究采用非常规策略开展HIV疫苗研发，设计了负载VPCS多表位编码mRNA的脂质纳米颗粒（MEVPCS-mRNA LNP）——该设计可增强树突状细胞的抗原呈递能力，进而促进有效细胞免疫。此外，本研究开发了一种新型可适配冷链的mRNA LNP制剂配方，可实现长期稳定储存与冷链储运，从而提升mRNA LNP疫苗在低收入国家的可及性。体内小鼠实验结果显示，免疫组小鼠可在全身循环及病毒入侵的黏膜部位产生VPCS特异性CD8记忆T细胞。MEVPCS-mRNA LNP疫苗诱导的CD8 T细胞免疫反应与HESN群体的免疫特征高度相似，且具备多功能性。值得注意的是，该疫苗几乎不会或仅引发极微弱的CD4 T细胞活化。本概念验证研究证实，MEVPCS-mRNA LNP疫苗可诱导针对多个高度保守VPCS的CD8 T细胞记忆免疫，因此可在人群中实现广谱覆盖，并限制病毒逃逸突变。MEVPCS-mRNA LNP疫苗有望成为一款有效的预防性HIV疫苗候选制剂。