Mechanisms of dengue virus neutralization by antibody

Dengue virus (DENV), the causative agent of dengue, is a group of viruses consisting of four different serotypes designated DENV1-4. Each serotype is further divided into different genotypes. Primary DENV infection induces a life-long type-specific immune response against the homologous DENV serotype. It is widely assumed that all the strains of a DENV serotype are equally neutralized by type-specific antibodies irrespective of the genetic variability within the serotype. Studies with mouse monoclonal antibodies (mAb) have demonstrated that serotype-specific neutralization of DENV is mainly mediated by antibody binding to epitopes on domain III of the viral Envelope protein (EDIII).;Although DENV3 has spread worldwide, neutralization mechanisms of DENV3 is poorly studied. Results of my studies with mouse mAbs demonstrate that type-specific neutralization of DENV3 was confined to EDIII lateral ridge as reported for other flaviviruses. I further demonstrated that DENV3 Envelope (E) protein sequences were variable between different genotypes of DENV3. Variable positions were located on or near the known antibody epitopes on E protein, and natural amino acid variations of DENV3 E protein led to complete or partial escape from antibody neutralization. These results suggest that natural intra-serotype variation should be considered when characterizing natural and vaccine induced immunity.;The specificity and functionality of the human antibody response to DENV is poorly characterized. It is unknown if humans also develop antibodies to EDIII epitopes recognized by mouse mAbs. Using a panel of sera from people exposed to DENV, I demonstrate that people develop low levels of type-specific EDIII reactive antibodies after primary infection and low levels of serotype cross reactive EDIII antibodies after secondary infection. I further demonstrated that these low levels of EDIII reactive antibodies only make a minor contribution to the total neutralization potency of human immune sera. I conclude that the EDIII epitopes identified using mouse reagents, which have been the focus of much recent work, are not the primary target of human antibodies that neutralize DENV. I believe these results will stimulate investigators to study previously neglected regions of the DENV envelope to identify functionally important epitopes engaged by human antibodies.