After dengue virus (DENV)
infection, antibody-dependent enhancement (ADE) is easy to occur when the
neutralizing antibody (NAb) gradually decreases to a sub-neutralizing concentration. In this cohort surveillance, we utilized sera samples collected from
dengue fever patients at different convalescent phases in Jinghong City, to investigate the dynamic change rule of DENV-specific
antibodies, and to analyze the risk of ADE caused by
secondary infection with heterologous serotypes DENVs. For baseline serosurvey, 191 four-year and 99 six-year sera samples during
convalescence were collected in 2017 and 2019, respectively. The positive rate of DENV-specific
immunoglobulin G was 98.4% in 2017, which significantly decreased to 82.8% in 2019. The geometric mean titer (GMT) of NAb decreased from 1:155.35 to 1:46.66. Among 290 overall samples, 73 paired consecutive samples were used for follow-up serosurvey. In four-year sera, the GMTs of NAb against DENV-3 and cross-reactive
antibodies against DENV-1, DENV-2 and DENV-4 were 1:167.70, 1:13.80, 1:18.54 and 1:45.26, respectively, which decreased to 1:53.18, 1:10.30, 1:14.60 and 1:8.17 in six-year sera. In age-stratified analysis, due to the increasing number of ADE positive samples from 2017 to 2019 in 31-40 and 51-60 years groups, the risk of ADE in DENV-4
infection was positively associated with the extension of convalescent phase, and the odd ratio was higher than other groups. With the recovery period lengthened, the risk of
secondary infection with DENV-1 and DENV-2 was reduced. Our results offer essential experimental data for risk prediction of
severe dengue in hyper-endemic
dengue areas, and provide crucial scientific insight for the development of effective
dengue vaccines.