Adenosine deaminase augments SARS-CoV-2 specific cellular and humoral responses in aged mouse models of immunization and challenge

Aged patients suffer disproportionately increased morbidity and mortality associated with SARS-CoV-2 infection. Despite numerous clinically available vaccines and therapeutics, aged patients remain at increased risk for COVID-19 morbidity. Furthermore, the aged patient population has suboptimal responses to SARS-CoV-2 vaccine antigens. Here, we characterize vaccine-induced responses to SARS-CoV-2 synthetic DNA vaccine antigens in 18-month-old mice and interrogate protection. Aged mice have altered cellular responses, including decreased IFN? secretion and increased TNFa secretion as compared to young mice. Aged mice had significantly decreased binding and neutralizing antibodies in their serum compared to their young counterparts. Co-immunization with the plasmid-encoded molecular adjuvant adenosine deaminase-1 (pADA) enhanced cellular responses and expanded the breadth of humoral responses in aged mice. pADA co-delivery also altered the gene expression profiles of lymph node lymphocytes in aged animals. Upon challenge pADA co-immunization modestly decreased age-associated morbidity and mortality in ACE2 transgenic and mouse-adapted SARS-CoV-2 challenge models. These data support the use of aged mice as a model for age-associated decreased vaccine immunogenicity and infection-mediated morbidity and mortality in the context of SARS-CoV-2 and provide further support of the use of adenosine deaminase as a molecular adjuvant. Overall design: single cell RNA-seq in young and aged treated and naïve mice

老年患者感染严重急性呼吸综合征冠状病毒2（SARS-CoV-2）后，其发病与死亡风险不成比例地升高。尽管目前已有多款临床可用的疫苗与治疗药物，老年群体罹患新型冠状病毒肺炎（COVID-19）后的发病风险仍显著升高。此外，老年人群对SARS-CoV-2疫苗抗原的应答效果欠佳。本研究对18月龄小鼠体内SARS-CoV-2合成DNA疫苗抗原的疫苗诱导应答特征进行了系统表征，并探究了其保护效力。与年轻小鼠相比，老年小鼠的细胞免疫应答发生显著改变，具体表现为γ干扰素（IFN-γ）分泌减少、肿瘤坏死因子α（TNF-α）分泌增加。老年小鼠血清中的结合抗体与中和抗体水平均显著低于年轻同龄小鼠。联合使用质粒编码的分子佐剂腺苷脱氨酶1（pADA）进行共免疫，可增强老年小鼠的细胞免疫应答，并拓宽其体液免疫应答的广度。pADA联合递送还可改变老年动物淋巴结淋巴细胞的基因表达谱。在攻毒实验中，pADA共免疫可轻度降低血管紧张素转换酶2（ACE2）转基因小鼠与小鼠适应性SARS-CoV-2攻毒模型中与年龄相关的发病与死亡风险。本研究数据支持以老年小鼠作为SARS-CoV-2感染背景下与年龄相关的疫苗免疫原性降低以及感染介导的发病与死亡的研究模型，并进一步证实了腺苷脱氨酶作为分子佐剂的应用潜力。整体实验设计：对年轻、老年免疫处理组与未免疫（naïve）小鼠开展单细胞RNA测序（single cell RNA-seq）。