Characterization of Two Highly Specific Monoclonal Antibodies Targeting the Glycan Loop of the Zika Virus Envelope Protein.

Zika virus (ZIKV) is an emerging flavivirus associated with several neurological diseases such as Guillain-Barré syndrome in adults and microcephaly in newborn children. Its distribution and mode of transmission (via Aedes aegypti and Aedes albopictus mosquitoes) collectively cause ZIKV to be a serious concern for global health. High genetic homology of flaviviruses and shared ecology is a hurdle for accurate detection. Distinguishing infections caused by different viruses based on serological recognition can be misleading as many anti-flavivirus monoclonal antibodies (mAbs) discovered to date are highly cross-reactive, especially those against the envelope (E) protein. To provide more specific research tools, we produced ZIKV E directed hybridoma cell lines and characterized two highly ZIKV-specific mAb clones (mAbs A11 and A42) against several members of the Flavivirus genus. Epitope mapping of mAb A11 revealed glycan loop specificity in Domain I of the ZIKV E protein. The development of two highly specific mAbs targeting the surface fusion protein of ZIKV presents a significant advancement in research capabilities as these can be employed as essential tools to enhance our understanding of ZIKV identification on infected cells ex vivo or in culture.

Thermostable Ebola virus vaccine formulations lyophilized in the presence of aluminum hydroxide.

No United States Food and Drug Administration-licensed vaccines protective against Ebola virus (EBOV) infections are currently available. EBOV vaccine candidates currently in development, as well as most currently licensed vaccines in general, require transport and storage under a continuous cold chain in order to prevent potential decreases in product efficacy. Cold chain requirements are particularly difficult to maintain in developing countries. To improve thermostability and reduce costly cold chain requirements, a subunit protein vaccine against EBOV was formulated as a glassy solid using lyophilization. Formulations of the key antigen, Ebola glycoprotein (EBOV-GP), adjuvanted with microparticulate aluminum hydroxide were prepared in liquid and lyophilized forms, and the vaccines were incubated at 40 °C for 12 weeks. Aggregation and degradation of EBOV-GP were observed in liquid formulations during the 12-week incubation period, whereas changes were minimal in lyophilized formulations. Antibody responses against EBOV-GP following three intramuscular immunizations in BALB/c mice were used to determine vaccine immunogenicity. EBOV-GP formulations were equally immunogenic in liquid and lyophilized forms. After lyophilization and reconstitution, adjuvanted vaccine formulations produced anti-EBOV-GP IgG antibody responses in mice similar to those generated against corresponding adjuvanted liquid vaccine formulations. More importantly, antibody responses in mice injected with reconstituted lyophilized vaccine formulations that had been incubated at 40 °C for 12 weeks prior to injection indicated that vaccine immunogenicity was fully retained after high-temperature storage, showing promise for future vaccine development efforts.

Recombinant proteins of Zaire ebolavirus induce potent humoral and cellular immune responses and protect against live virus infection in mice.

Infections with filoviruses in humans are highly virulent, causing hemorrhagic fevers which result in up to 90% mortality. In addition to natural infections, the ability to use these viruses as bioterrorist weapons is of significant concern. Currently, there are no licensed vaccines or therapeutics available to combat these infections. The pathogenesis of disease involves the dysregulation of the host's immune system, which results in impairment of the innate and adaptive immune responses, with subsequent development of lymphopenia, thrombocytopenia, hemorrhage, and death. Questions remain with regard to the few survivors of infection, who manage to mount an effective adaptive immune response. These questions concern the humoral and cellular components of this response, and whether such a response can be elicited by an appropriate prophylactic vaccine. The data reported herein describe the production and evaluation of a recombinant subunit Ebola virus vaccine candidate consisting of insect cell expressed Zaire ebolavirus (EBOV) surface glycoprotein (GP) and the matrix proteins VP24 and VP40. The recombinant subunit proteins are shown to be highly immunogenic in mice, yielding both humoral and cellular responses, as well as highly efficacious, providing up to 100% protection against a lethal challenge with live virus. These results demonstrate proof of concept for such a recombinant non-replicating vaccine candidate in the mouse model of EBOV which helps to elucidate immune correlates of protection and warrants further development.