Antibodies capable of activating the complement system (CS) when bound with antigen are referred to as “complement-fixing antibodies” and are involved in protection against Flaviviruses. A complement-fixing antibody test has been used in the past to measure the ability of dengue virus (DENV)-specific serum antibodies to activate the CS. As originally developed, the test is time-consuming, cumbersome, and has limited sensitivity for DENV diagnosis. Here, we developed and characterized a novel multiplex anti-DENV complement-fixing assay based on the Luminex platform to quantitate serum antibodies against all four serotypes (DENV1-4) that activate the CS based on their ability to fix the complement component 1q (C1q). The assay demonstrated good reproducibility and showed equivalent performance to a DENV microneutralization assay that has been used to determine DENV serostatus. In non-human primates, antibodies produced in response to primary DENV1-4 infection induced C1q fixation on homologous and heterologous serotypes. Inter-serotype cross-reactivity was associated with homology of the envelope protein. Interestingly, the antibodies produced following vaccination against Zika virus fixed C1q on DENV. The anti-DENV complement fixing antibody assay represents an alternative approach to determine the quality of functional antibodies produced following DENV natural infection or vaccination and a biomarker for dengue serostatus, while providing insights about immunological cross-reactivity among different Flaviviruses.

Problem Interferon epsilon (IFNε) is a unique type I IFN that is expressed in response to sex steroids. Studies suggest that type I IFNs regulate inflammation‐induced preterm birth (PTB), but no study has examined the role of IFNε in human pregnancy. Method of Study We used stored vaginal swabs between 8 and 26 weeks of gestation from the Global Alliance to Prevent Prematurity and Stillbirth (GAPPS) biobank and measured IFNε by enzyme‐linked immunosorbent assay (ELISA). A total of 29 women with spontaneous preterm births, 34 women with medically indicated preterm births, and 134 women with term births were included. Secondary outcomes included a preterm birth with chorioamnionitis and preeclampsia with a preterm birth. Logistic regression calculated odds ratios (OR) and 95% confidence intervals (CI) adjusting for maternal age, race, body mass index, prior pregnancy complications, lower genital tract infections, chronic health conditions, and gestational age at blood draw. Results and Conclusions There was no significant association between IFNε and spontaneous preterm birth (ORadj 1.0, 0.8–1.3) or chorioamnionitis (ORadj 1.6, 0.7–3.5). A trend toward increased odds of medically indicated preterm birth (ORadj. 1.3, 1.0–1.8) was observed. This was likely due to elevated IFNε among women with preterm preeclampsia (ORadj. 2.0, 95% CI 1.3–3.2). While exploratory, our novel findings suggest that larger longitudinal studies of IFNε across human pregnancy may be warranted.

Background Antibody-driven complement system (CS) activation has been associated with protection against symptomatic dengue virus (DENV) infection. Aggregation, opsonization, lysis, and phagocytosis are mechanisms triggered by antibody-antigen immunocomplexes following fixation of the component 1q (C1q) and activation of the classical pathway. As a result, DENV neutralization and clearance are facilitated, whereas antibody-dependent enhancement of infection is inhibited. We investigated the ability of antibodies produced in response to Takeda’s dengue vaccine candidate, TAK-003, to fix C1q and activate CS. Methods Serum samples were collected from seronegative and seropositive participants in a phase 2 clinical trial (DEN-203; ClinicalTrials.gov: NCT01511250), pre- and post-vaccination. Samples were evaluated for the presence of complement-fixing antibodies (CFAs) against DENV using a Luminex multiplex-based immunoassay. Results TAK-003 elicited production of CFAs against all 4 DENV serotypes, which persisted for 1 year post-vaccination, irrespective of baseline serostatus. CFA levels were correlated with neutralizing antibody titers and virus-binding total IgG and IgG1 concentrations. Furthermore, efficiency of CFA fixation was greater in samples with higher polyclonal IgG avidity. Conclusion These results indicate that antibodies produced after TAK-003 vaccination are functional in both activating CS and neutralizing virus infection by all DENV serotypes, which may contribute to efficacy of TAK-003.