Background: Dengue virus is transmitted by mosquitoes and has four serotypes. Cross-protection to other serotypes lasting
for a few months is observed following infection with one serotype. There is evidence that low-affinity T and/or B cells from
primary infections contribute to the severe syndromes often associated with secondary dengue infections. such
pronounced immune-mediated enhancement suggests a dengue-specific pattern of immune cell activation. This study
investigates the acute and early convalescent B cell response leading to the generation of cross-reactive and neutralizing
antibodies following dengue infection.
Methodology/Principal Findings: We assayed blood samples taken from dengue patients with primary or secondary
infection during acute disease and convalescence and compared them to samples from patients presenting with nondengue
related fever. Dengue induced massive early plasmablast formation, which correlated with the appearance of
polyclonal, cross-reactive IgG for both primary and secondary infection. Surprisingly, the contribution of IgG to the
neutralizing titer 4–7 days after fever onset was more than 50% even after primary infection.
Conclusions/Significance: Poly-reactive and virus serotype cross-reactive IgG are an important component of the innate
response in humans during both primary and secondary dengue infection, and ‘‘innate specificities’’ seem to constitute part
of the adaptive response in dengue. While of potential importance for protection during secondary infection, cross-reactive
B cells will also compete with highly neutralizing B cells and possibly interfere with their development.