Protection against symptomatic dengue infection by neutralizing antibodies varies by infection history and infecting serotype

Dengue viruses (DENV1–4) are the most prevalent arboviruses in humans and a major public health concern. Understanding immune mechanisms that modulate DENV infection outcome is critical for vaccine development. Neutralizing antibodies (nAbs) are an essential component of the protective immune response, yet their measurement often relies on a single cellular substrate and partially mature virions, which does not capture the full breadth of neutralizing activity and may lead to biased estimations of nAb potency. Here, we analyze 125 samples collected after one or more DENV infections but prior to subsequent symptomatic or inapparent DENV1, DENV2, or DENV3 infections from a long-standing pediatric cohort study in Nicaragua. By assessing nAb responses using Vero cells with or without DC-SIGN and with mature or partially mature virions, we find that nAb potency and the protective NT50 cutoff are greatly influenced by cell substrate and virion maturation state. Additionally, the correlation between nAb titer and protection from disease depends on prior infection history and infecting serotype. Finally, we uncover variations in nAb composition that contribute to protection from symptomatic infection differently after primary and secondary prior infection. These findings have important implications for identifying antibody correlates of protection for vaccines and natural infections

Favipiravir (T-705) Protects IFNAR−/− Mice against Lethal Zika Virus Infection in a Sex-Dependent Manner

Zika virus (ZIKV), a member of the Flaviviridae family, is an important human pathogen that has caused epidemics in Africa, Southeast Asia, and the Americas. No licensed treatments for ZIKV disease are currently available. Favipiravir (T-705; 6-fluoro-3-hydroxy-2-pyrazinecarboxamide) and ribavirin (1-(β-D-Ribofuranosyl)-1H-1,2,4-triazole-3-carboxamide) are nucleoside analogs that have exhibited antiviral activity against a broad spectrum of RNA viruses, including some flaviviruses. In this study, we strengthened evidence for favipiravir and ribavirin inhibition of ZIKV replication in vitro. Testing in IFNAR−/− mice revealed that daily treatments of favipiravir were sufficient to provide protection against lethal ZIKV challenge in a dose-dependent manner but did not completely abrogate disease. Ribavirin, on the other hand, had no beneficial effect against ZIKV infection in this model and under the conditions examined. Combined treatment of ribavirin and favipiravir did not show improved outcomes over ribavirin alone. Surprisingly, outcome of favipiravir treatment was sex-dependent, with 87% of female but only 25% of male mice surviving lethal ZIKV infection. Since virus mutations were not associated with outcome, a sex-specific host response likely explains the observed sex difference

Protection against symptomatic dengue infection by neutralizing antibodies varies by infection history and infecting serotype.

Dengue viruses (DENV1-4) are the most prevalent arboviruses in humans and a major public health concern. Understanding immune mechanisms that modulate DENV infection outcome is critical for vaccine development. Neutralizing antibodies (nAbs) are an essential component of the protective immune response, yet their measurement often relies on a single cellular substrate and partially mature virions, which does not capture the full breadth of neutralizing activity and may lead to biased estimations of nAb potency. Here, we analyze 125 samples collected after one or more DENV infections but prior to subsequent symptomatic or inapparent DENV1, DENV2, or DENV3 infections from a long-standing pediatric cohort study in Nicaragua. By assessing nAb responses using Vero cells with or without DC-SIGN and with mature or partially mature virions, we find that nAb potency and the protective NT50 cutoff are greatly influenced by cell substrate and virion maturation state. Additionally, the correlation between nAb titer and protection from disease depends on prior infection history and infecting serotype. Finally, we uncover variations in nAb composition that contribute to protection from symptomatic infection differently after primary and secondary prior infection. These findings have important implications for identifying antibody correlates of protection for vaccines and natural infections