SUMMARY CD8+ T cells protect against and promote the pathogenesis of some flaviviruses, but their role in Zika virus (ZIKV) infection is unknown. We developed mice lacking the type I interferon receptor specifically in a subset of myeloid cells (LysMCre+IFNARfl/fl C57BL/6 (H-2b) mice) as a model for ZIKV infection and used it to evaluate CD8+ T cell responses to ZIKV. 26 and 15 CD8+ T cell-reactive peptides for ZIKV African (MR766) and Asian (FSS13025) lineage strains respectively were identified and validated. CD8+ T cells from infected mice were polyfunctional and mediated cytotoxicity. Adoptive transfer of ZIKV-immune CD8+ T cells reduced viral burdens, whereas their depletion led to higher tissue burdens and CD8−/− mice displayed higher mortality to ZIKV-infection. Collectively, these results demonstrate that CD8+ T cells protect against ZIKV infection. Further, this study provides an immunocompetent mouse model for investigating ZIKV-specific T cell responses.

SUMMARY Zika virus (ZIKV) related neuropathology is an important global health concern. Several studies have shown that ZIKV can infect neural stem cells in the developing brain, but infection in the adult brain has not been examined. Two areas in the adult mouse brain contain neural stem cells: the subventricular zone of the anterior forebrain and the subgranular zone of the hippocampus. Here using six week old mice triply deficient in interferon regulatory factor (IRF) as a model, we show that blood-borne ZIKV administration can lead to pronounced evidence of ZIKV infection in these adult neural stem cells, leading to cell death and reduced proliferation. Our data therefore suggest that adult as well as fetal neural stem cells are vulnerable to ZIKV neuropathology. Thus, although ZIKV is considered a transient infection in adult humans without marked long-term effects, there may in fact be consequences of exposure in the adult brain.

CD8+ T cells play an important role in controlling Flavivirus infection, including Zika virus (ZIKV). Here, we have identified 25 HLA-B*0702-restricted epitopes and 1 HLA-A*0101-restricted epitope using interferon (IFN)-γ enzyme-linked immunospot (ELISPOT) and intracellular cytokine staining (ICS) in ZIKV-infected IFN-α/β receptor-deficient HLA transgenic mice. The cross-reactivity of ZIKV epitopes to dengue virus (DENV) was tested using IFN-γ-ELISPOT and IFN-γ-ICS on CD8+ T cells from DENV-infected mice, and five cross-reactive HLA-B*0702-binding peptides were identified by both assays. ZIKV/DENV cross-reactive CD8+ T cells in DENV-immune mice expanded post ZIKV challenge and dominated in the subsequent CD8+ T cell response. ZIKV challenge following immunization of mice with ZIKV-specific and ZIKV/DENV cross-reactive epitopes elicited CD8+ T cell responses that reduced infectious ZIKV levels, and CD8+ T cell depletions confirmed that CD8+ T cells mediated this protection. These results identify ZIKV-specific and ZIKV/DENV cross-reactive epitopes and demonstrate both an altered immunodominance pattern in the DENV-immune setting relative to naive, as well as a protective role for epitope-specific CD8+ T cells against ZIKV. These results have important implications for ZIKV vaccine development and provide a mouse model for evaluating anti-ZIKV CD8+ T cell responses of human relevance.

One of the major challenges of the current Zika virus (ZIKV) epidemic is to prevent congenital foetal abnormalities, including microcephaly, following ZIKV infection of pregnant women. Given the urgent need for ZIKV prophylaxis and treatment, repurposing of approved drugs appears to be a viable and immediate solution. We demonstrate that the common anti-malaria drug chloroquine (CQ) extends the lifespan of ZIKV-infected interferon signalling-deficient AG129 mice. However, the severity of ZIKV infection in these mice precludes the study of foetal (vertical) viral transmission. Here, we show that interferon signalling-competent SJL mice support chronic ZIKV infection. Infected dams and sires are both able to transmit ZIKV to the offspring, making this an ideal model for in vivo validation of compounds shown to suppress ZIKV in cell culture. Administration of CQ to ZIKV-infected pregnant SJL mice during mid-late gestation significantly attenuated vertical transmission, reducing the ZIKV load in the foetal brain more than 20-fold. Given the limited side effects of CQ, its lack of contraindications in pregnant women, and its worldwide availability and low cost, we suggest that CQ could be considered for the treatment and prophylaxis of ZIKV.

SUMMARY Zika virus (ZIKV) targets neural progenitor cells in the brain, attenuates cell proliferation, and leads to cell death. Here, we describe a role for the ZIKV protease NS2B-NS3 heterodimer in mediating neurotoxicity through cleavage of a host protein required for neurogenesis. Similar to ZIKV infection, NS2B-NS3 expression led to cytokinesis defects and cell death in a protease activity-dependent fashion. Among binding partners, NS2B-NS3 cleaved Septin-2, a cytoskeletal factor involved in cytokinesis. Cleavage of Septin-2 occurred at residue 306 and forced expression of a non-cleavable Septin-2 restored cytokinesis, suggesting a direct mechanism of ZIKV-induced neural toxicity.