Fig. 7

Serum neutralization against VACV Tiantan strain. A-D In vitro neutralization assay against VACV Tiantan strain in the presence of polyclonal IgG antibodies purified from the indicated donors. The donors include two individuals recovered from previous VACV infection (A), four donors with low level anti-MPXV ELISA signal (B), and the top 13 antibody responders (C and D). Red, individuals born before 1980; blue, individuals born after 1980; orange, individuals recovered from previous VACV infection. The monolayer BHK 21 cells were stained by crystal violet, while the formed plaques were visualized and labeled in red by software. The number in the lower left corner of each well represents the plaque number in the corresponding well; while the number in the lower right corner means the percentage of well area covered by the plaques. E Scatter plot for VACV infection rates. The x axis is the plaque number, and the y axis is the percentage of well area covered by the plaques. Each sample has two repeats. F Statistical analysis based on the well area percentage. Means with standard deviations are shown. The p values were calculated using an unpaired Student’s t test