Dengue virus is a major global health threat and can lead to life-threatening hemorrhagic complications due to immune activation and
cytokine production. Cross-reactive
antibodies to an earlier dengue virus
infection are a recognized risk factor for severe disease. These
antibodies bind heterologous
dengue serotypes and enhance
infection into
Fc-receptor-bearing cells, a process known as antibody-dependent enhancement of
infection. One crucial
cytokine seen elevated in
severe dengue patients is IL-1β, a potent inflammatory
cytokine matured by the
inflammasome. We used a highly-physiologic system by studying antibody-dependent enhancement of IL-1β in primary human monocytes with anti-
dengue human
monoclonal antibodies isolated from patients. Antibody-enhancement increased viral replication in primary human monocytes inoculated with supernatant harvested from Vero cells infected with dengue virus serotype 2 (DENV-2) 16681. Surprisingly, IL-1β secretion induced by infectious supernatant harvested from two independent Vero cell lines was not enhanced by antibody. Secretion of multiple other inflammatory
cytokines was also independent of antibody signaling. However, IL-1β secretion did require NLRP3 and caspase-1 activity. Immunodepletion of
dengue virions from the infectious supernatant confirmed that virus was not the main IL-1β-inducing agent, suggesting that a supernatant component(s) not associated with the virion induced IL-1β production. We excluded
RNA,
DNA, contaminating LPS, viral NS1
protein, complement, and
cytokines. In contrast, purified Vero-derived DENV-2 16681 exhibited antibody-enhancement of both
infection and IL-1β induction. Furthermore, C6/36 mosquito cells did not produce such an inflammatory component, as crude supernatant harvested from insect cells infected with DENV-2 16681 induced antibody-dependent IL-1β secretion. This study indicates that Vero cells infected with DENV-2 16681 may produce inflammatory components during dengue virus propagation that mask the virus-specific immune response. Thus, the choice of host cell and viral purity should be carefully considered, while insect-derived virus represents a system that elicits antibody-dependent
cytokine responses to dengue virus with fewer confounding issues.