Maternal Antibody Kinetics and Infant Susceptibility to Dengue Infection in India.

Dengue is the most widespread mosquito-borne viral disease globally, as well as in India. Children are most susceptible to acquiring severe primary dengue infection because the protective levels of maternal antibodies decline over time. In view of the forthcoming introduction of dengue vaccines, understanding the kinetics of maternal antibodies is a critical parameter for determining the correct age of immunization in children. In this cross-sectional study conducted at a tertiary care hospital in Pune, India, 602 serum samples from infants were screened for anti-dengue IgG antibodies using ELISA. Dengue-specific antibodies were found in 71% of cord blood samples and gradually declined to 63%, 14%, 3%, 5%, and 7% in infants by the ages of 3, 6, 9, 12, and 15 months, respectively. At 3 months of age, 14 of 72 (19%) infants acquired dengue infection and became seropositive for anti-dengue IgM antibodies. A total of 80% (36/45) of infants tested for neutralizing antibodies at birth were positive for three or four dengue virus (DENV) serotypes. Geometric mean titers of neutralizing antibodies decreased to the lowest levels of 87%, 98%, 88%, and 92% against DENV-1, DENV-2, DENV-3, and DENV-4 in 9-month-old infants. The study results suggest that maternal antibodies drastically reduced in infants by the age of 6 months, and infants as young as 3 months were susceptible to dengue infection. In summary, the data in the current study provide useful insights into the kinetics of maternally transferred antibodies and susceptibility of Indian infants to DENV.