Potency and breadth of human primary ZIKV immune sera shows that Zika viruses cluster antigenically as a single serotype

Global evaluation of lineage-specific human papillomavirus capsid antigenicity using antibodies elicited by natural infection

Human Papillomavirus (HPV) type variants have been classified into lineages and sublineages based upon their whole genome sequence. Here we have examined the specificity of antibodies generated following natural infection with lineage variants of oncogenic types (HPV16, 18, 31, 33, 45, 52 and 58) by testing serum samples assembled from existing archives from women residing in Africa, The Americas, Asia or Europe against representative lineage-specific pseudoviruses for each genotype. We have subjected the resulting neutralizing antibody data to antigenic clustering methods and created relational antigenic profiles for each genotype to inform the delineation of lineage-specific serotypes. For most genotypes, there was evidence of differential recognition of lineage-specific antigens and in some cases of a sufficient magnitude to suggest that some lineages should be considered antigenically distinct within their respective genotypes. These data provide compelling evidence for a degree of lineage specificity within the humoral immune response following natural infection with oncogenic HPV.

A safe replication-defective Zika virus vaccine protects mice from viral infection and vertical transmission

With the explosive emergence of Zika virus (ZIKV) and the consequent devastating fetal malformations in infected expectant women, a safe and effective vaccine is urgently needed. Here, using our established NS1 trans-complementation system, we generated high titer of replication-defective ZIKV with NS1 deletion (ZIKV-ΔNS1) in the BHK-21 cell line stably expressing NS1 (BHK_NS1). NS1 deletion of ZIKV-ΔNS1 was stably maintained as no replicative virus was found in naïve BHK-21 cells after continuous passaging of ZIKV-ΔNS1 in BHK_NS1 cells. The safety of ZIKV-ΔNS1 was demonstrated when a high dose of ZIKV-ΔNS1 (10⁷ IU) was used to infect the highly susceptible type I and type II interferon (IFN) receptor-deficient mice. ZIKV-ΔNS1 could induce antibody responses in both immunocompetent (BALB/c) and immunodeficient mice and a single dose of ZIKV-ΔNS1 vaccine protected the immunodeficient mice from a highly lethal dosage of challenge with WT ZIKV. ZIKV-ΔNS1 immunization also attenuated vertical transmission during pregnancy of type I IFN receptor-deficient IFNAR^-/- mice and protected fetuses from ZIKV infection. Our data reported here not only provide a promising ZIKV vaccine candidate with a satisfied balance between safety and efficacy, but also demonstrate the potential of the NS1 trans-complementation system as a platform for flavivirus vaccine development, especially for highly pathogenic flaviviruses.

A potent candidate against Zika virus infection: Synthesis, bioactivity, radiolabeling and biodistribution studies

Compound VI exhibits potent activity against Zika virus infection combined with favorable cellular uptake and biodistribution without apparent cytotoxicity in a mouse model.

Non-structural protein 1-specific antibodies directed against Zika virus in humans mediate antibody-dependent cellular cytotoxicity

There is growing interest in understanding antibody (Ab) function beyond neutralization. The non-structural protein 1 (NS1) of Zika virus (ZIKV) is an attractive candidate for an effective vaccine as Abs against NS1, unlike the envelope or premembrane, do not carry the risk of mediating antibody-dependent enhancement. Our aim was to evaluate whether ZIKV NS1 Abs elicited following natural infection in humans can mediate antibody-dependent cellular cytotoxicity (ADCC). We evaluated the isotype specificity of ZIKV-specific Abs in immune sera and supernatants from stimulated immune PBMC and found that Abs against ZIKV NS1 and virus-like particles were predominantly of the IgG1 isotype. Using a recently developed FluoroSpot assay, we found robust frequencies of NS1-specific Ab-secreting cells in PBMC of individuals who were naturally infected with ZIKV. We developed assays to measure both natural killer cell activation by flow cytometry and target cell lysis of ZIKV NS1-expressing cells using an image cytometry assay in the presence of ZIKV NS1 Abs. Our data indicate efficient opsonization of ZIKV NS1-expressing CEM-NK^R cell lines using ZIKV-immune but not ZIKV-naïve sera, a prerequisite of ADCC. Furthermore, sera from immune donors were able to induce both NK cell degranulation and lysis of ZIKV NS1 CEM-NK^R cells in vitro. Our data suggest that ADCC is a possible mechanism for ZIKV NS1 Abs to eliminate virally infected target cells.

A Zika Vaccine Generated Using the Chimeric Insect-Specific Binjari Virus Platform Protects against Fetal Brain Infection in Pregnant Mice

Zika virus (ZIKV) is the etiological agent of congenital Zika syndrome (CZS), a spectrum of birth defects that can lead to life-long disabilities. A range of vaccines are in development with the target population including pregnant women and women of child-bearing age. Using a recently described chimeric flavivirus vaccine technology based on the novel insect-specific Binjari virus (BinJV), we generated a ZIKV vaccine (BinJ/ZIKA-prME) and illustrate herein its ability to protect against fetal brain infection. Female IFNAR^−/− mice were vaccinated once with unadjuvanted BinJ/ZIKA-prME, were mated, and at embryonic day 12.5 were challenged with ZIKV_PRVABC59. No infectious ZIKV was detected in maternal blood, placenta, or fetal heads in BinJ/ZIKA-prME-vaccinated mice. A similar result was obtained when the more sensitive qRT PCR methodology was used to measure the viral RNA. BinJ/ZIKA-prME vaccination also did not result in antibody-dependent enhancement of dengue virus infection or disease. BinJ/ZIKA-prME thus emerges as a potential vaccine candidate for the prevention of CSZ.