Fig. 3

Fold-enhancement activity in 34 pair serum samples obtained from 34 individuals who were DENV IgG positive before the dengue season and demonstrated elevated DENV IgG after the season versus patient group. Fold enhancement value was determined by the ratio of (mean plaque count at 1:20 serum dilution)/(mean plaque count in the absence of human serum samples) by using FcγR expressing BHK cells. Dash line represents for cut-off plus 2 times SD value of infection-enhancement. Positive infection-enhancing activity was defined as fold enhancement value greater than cut-off value plus 2 times SD (above dash line). P-value was determined by Mann -Whitney test. P-value ≤0.05 = significant. NA-: Neutralizing antibody titer <10; NA+: Neutralizing antibody titer ≥10. Non patient 1 = pre-dengue season group; Non patient 2 = post-dengue season group; Patient = confirmed DENV infected patient group. The results were represented as Median ± interquartile range (Median ± IQR)