Characterization of Pre-Existing Neutralizing Antibody to Human Adenovirus Types 5 and 49 and Simian Type 23 in Chinese Population

Recombinant adenovirus vector has been widely used in vaccine development. Due to the pre-existing immunity of human adenovirus type 5 (HAd5) in humans, a range of rare human and chimpanzee adenovirus vectors have been developed. In the previous study, we constructed novel adenovirus vector Sad23L and Ad49L based on simian adenovirus type 23 (SAd23) and human adenovirus type 49 (HAd49), which were used in the development of ZIKV and COVID-19 vaccines. However, the levels of pre-existing neutralizing antibody (NAb) of HAd49 and SAd23 remain unclear in China. In this study, we measured NAbs titers of HAd5, HAd49, and SAd23 in 600 healthy blood donors from 6 regions across China. NAb titer of HAd49 or SAd23 was significantly lower than that of HAd5 (p < 0.001). There was no significant difference in seroprevalence and NAb titers of three adenoviruses between male and female donors. The seropositive rates of HAd5 and SAd23 increased with age growth in a positive correlation (p < 0.01), while in contrast to HAd5, HAd49, and SAd23 had a low level of pre-existing immunity in Chinese population, which suggested that Ad49L and Sad23L vectors could be used in vaccine development for humans.