Highly divergent SARS-CoV-2 variants have continuously emerged and spread around the world, and updated vaccines and innovative vaccination strategies are urgently needed to address the global SARS-COV2 pandemic. Here, we established a series of Ad5-vectored SARS-CoV-2 variant vaccines encoding multiple spike proteins derived from the Alpha, Beta, Gamma, Epsilon, Kappa, Delta and Omicron lineages and analyzed the antibody immune responses induced by single-dose and prime-boost vaccination strategies against emerging SARS-CoV-2 variants of concern (VOCs). Single-dose vaccination with SARS-CoV-2 variant vaccines tended to elicit the optimal self-matched neutralizing effects, and Ad5-B.1.351 produced more broad-spectrum cross-neutralizing antibodies against diverse variants. In contrast, prime-boost vaccination further strengthened and broadened the neutralizing antibody responses against highly divergent SARS-CoV-2 variants. The heterologous administration of Ad5-B.1.617.2 and Ad5-B.1.429 to Ad5-WT-primed mice resulted in superior antibody responses against most VOCs. In particular, the Omicron spike could only stimulate self-matched neutralizing antibodies with infrequent cross-reactivities to other variants used in single-dose vaccination strategies; moreover, with prime-boost regimens, this vaccine elicited an optimal specific neutralizing antibody response to Omicron, and prompted cross-antibody responses against other VOCs that were very similar to those obtained with Ad5-WT booster. Overall, this study delineated the unique characteristics of antibody responses to the SARS-CoV-2 VOC spikes with the single-dose or prime-boost vaccination strategies and provided insight into the vaccine development of next SARS-CoV-2 VOCs.

高度分化的 SARS-CoV-2 变体不断出现并在世界范围内传播，迫切需要更新的疫苗和创新的疫苗接种策略来应对全球 SARS-COV2 大流行。在这里，我们建立了一系列以 Ad5 为载体的 SARS-CoV-2 变体疫苗，编码来自 Alpha、Beta、Gamma、Epsilon、Kappa、Delta 和 Omicron 谱系的多种刺突蛋白，并分析了单剂量和针对新出现的 SARS-CoV-2 关注变体 (VOC) 的主要加强疫苗接种策略。用 SARS-CoV-2 变体疫苗进行单剂量疫苗接种往往会引发最佳的自我匹配中和作用，而 Ad5-B.1.351 产生了针对多种变体的更广谱的交叉中和抗体。相比之下，初免加强疫苗接种进一步加强和扩大了针对高度不同的 SARS-CoV-2 变体的中和抗体反应。Ad5-B.1.617.2 和 Ad5-B.1.429 对 Ad5-WT 引发的小鼠的异源施用导致针对大多数 VOC 的优异抗体反应。特别是，Omicron 刺突只能刺激自我匹配的中和抗体，很少与单剂量疫苗接种策略中使用的其他变体发生交叉反应。此外，通过初免加强方案，该疫苗引发了对 Omicron 的最佳特异性中和抗体反应，并促进了针对其他 VOC 的交叉抗体反应，这些反应与使用 Ad5-WT 加强剂获得的那些非常相似。全面的，