Fig. 2. Seroprevalences of HAdV-4 and HAdV-5 nAbs in healthy blood donors in China (Beijing, n = 255, and Jiangsu, n = 260) and Sierra Leone (Freetown, n = 498).

The nAb titers of HAdV-4 and HAdV-5 were tested using Ad4-Luc- and Ad5-Luc-based neutralization assays (IC₉₀) and were categorized into four subgroups as follows: negative, <12; low, 12–200; moderate, 201–1000; and high, >1000. The nAb distributions (a) and the seropositive rates (b) of HAdV-4 and HAdV-5 in Beijing, Jiangsu, and Sierra Leone are shown. The data were analyzed by the Pearson chi-square test. c The difference in the nAb titers between HAdV-4- and HAdV-5-positive serum samples was analyzed by the Mann–Whitney test. d The percentages of serum samples with moderate or high levels of HAdV-4 and HAdV-5 nAbs are shown. The comparison was performed with the Pearson chi-square test. In all of the above comparison tests, a P value of <0.05 was considered to be significant; ^**P value < 0.01, ^***P value < 0.001