Zika Virus Antagonizes Type I Interferon Responses during Infection of Human Dendritic Cells

115

Confirmed reports of Zika virus (ZIKV) in human seminal fluid for months after the clearance of viremia suggest the ability of ZIKV to establish persistent infection in the seminiferous tubules, an immune-privileged site in the testis protected by the blood-testis barrier, also called the Sertoli cell (SC) barrier (SCB). However, cellular targets of ZIKV in human testis and mechanisms by which the virus enters seminiferous tubules remain unclear. We demonstrate that primary human SCs were highly susceptible to ZIKV compared to the closely related dengue virus and induced the expression of alpha interferon (IFN-␣), key cytokines, and cell adhesion molecules (vascular cell adhesion molecule 1 [VCAM-1] and intracellular adhesion molecule 1 [ICAM-1]). Furthermore, using an in vitro SCB model, we show that ZIKV was released on the adluminal side of the SCB model with a higher efficiency than in the blood-brain barrier model. ZIKV-infected SCs exhibited enhanced adhesion of leukocytes that correlated with decreases in SCB integrity. ZIKV infection did not affect the expression of tight and adherens junction proteins such as ZO-1, claudin, and JAM-A; however, exposure of SCs to inflammatory mediators derived from ZIKV-infected macrophages led to the degradation of the ZO-1 protein, which correlated with increased SCB permeability. Taken together, our data suggest that infection of SCs may be one of the crucial steps by which ZIKV gains access to the site of spermatozoon development and identify SCs as a therapeutic target to clear testicular infections. The SCB model opens up opportunities to assess interactions of SCs with other testicular cells and to test the ability of anti-ZIKV drugs to cross the barrier.IMPORTANCE Recent outbreaks of ZIKV, a neglected mosquito-borne flavivirus, have identified sexual transmission as a new route of disease spread, which has not been reported for other flaviviruses. To be able to sexually transmit for months after the clearance of viremia, ZIKV must establish infection in the seminiferous tubules, the site of spermatozoon development. However, little is known about the cell types that support ZIKV infection in the human testis. Currently, there are no models to study mechanisms of virus persistence in the seminiferous tubules. We provide evidence that ZIKV infection of human Sertoli cells, which are an important component of the seminiferous tubules, is robust and induces a strong antiviral response. The use of an in vitro Sertoli cell barrier to describe how ZIKV or inflammatory mediators derived from ZIKV-infected macrophages compromise barrier integrity will enable studies to explore the interactions of other testicular cells with Sertoli cells and to test novel antivirals for clearing testicular ZIKV infection.

Section: Discussionmentioning

confidence: 62%

Zika Virus Infects Human Sertoli Cells and Modulates the Integrity of the In Vitro Blood-Testis Barrier Model

Siemann

Strange

Maharaj

et al. 2017

115

“…Numerous studies have demonstrated that type I interferon (IFN) deficiency impaired the CD8 ϩ T cell response during virus infection through many cellular and molecule mechanisms, such as by impairing the priming effect of dendritic cells and upregulating the expression of the inhibitory molecules PD-1 and Tim3 of CD8 ϩ T cells during virus infection (10,12,13). In addition, because of the deficiency of innate immune components, the IFNAR knockout (KO) mouse model could exclude a comprehensive study of the immune response (14,15) and did not reflect the natural immune response after infection. Therefore, we sought to investigate whether a CD8 ϩ T cell response can be induced in WT mice.…”

Section: Resultsmentioning

confidence: 99%

CD8 ⁺ T Cell Immune Response in Immunocompetent Mice during Zika Virus Infection

Huang

Zhang

et al. 2017

104

100

Zika virus (ZIKV) infection causees neurologic complications, includingGuillain-Barré syndrome in adults and central nervous system (CNS) abnormalities in fetuses. We investigated the immune response, especially the CD8 ϩ T cell response in C57BL/6 (B6) wild-type (WT) mice, during ZIKV infection. We found that a robust CD8 ϩ T cell response was elicited, major histocompatibility complex class I-restricted CD8 ϩ T cell epitopes were identified, a tetramer that recognizes ZIKV-specific CD8 ϩ T cells was developed, and virus-specific memory CD8 ϩ T cells were generated in these mice. The CD8 ϩ T cells from these infected mice were functional, as evidenced by the fact that the adoptive transfer of ZIKV-specific CD8 ϩ T cells could prevent ZIKV infection in the CNS and was cross protective against dengue virus infection. Our findings provide comprehensive insight into immune responses against ZIKV and further demonstrate that WT mice could be a natural and easy-access model for evaluating immune responses to ZIKV infection.IMPORTANCE ZIKV infection has severe clinical consequences, including GuillainBarré syndrome in adults, microcephaly, and congenital malformations in fetuses and newborn infants. Therefore, study of the immune response, especially the adaptive immune response to ZIKV infection, is important for understanding diseases caused by ZIKV infection. Here, we characterized the CD8 ϩ T cell immune response to ZIKV in a comprehensive manner and identified ZIKV epitopes. Using the identified immunodominant epitopes, we developed a tetramer that recognizes ZIKVspecific CD8 ϩ T cells in vivo, which simplified the detection and evaluation of ZIKVspecific immune responses. In addition, the finding that tetramer-positive memory CD8 ϩ T cell responses were generated and that CD8 ϩ T cells can traffic to a ZIKVinfected brain greatly enhances our understanding of ZIKV infection and provides important insights for ZIKV vaccine design.KEYWORDS CD8 ϩ T cell, ZIKV, central nervous system, cross protection, immunocompetent mouse model Z ika virus (ZIKV) is a mosquito-transmitted flavivirus and a member of the Flaviviridae family of positive-stranded RNA enveloped viruses; the virus has also been found to be sexually and vertically transmitted (1). It was identified in 1947 in sentinel monkeys in Uganda (2). After its introduction into Brazil in 2015, ZIKV spread rapidly, both (i) causing a mild syndrome characterized by self-limiting fever, headache, myalgia, rash, and conjunctivitis and (ii) resulting in severe clinical consequences, including Guillain-

“…Moreover, recent studies have demonstrated the importance of the interferon response in modulating Zika virus infection and disease outcome (61)(62)(63)(64). In response to these mechanisms, Zika virus inhibits RIGI and type I IFN signaling in dendritic cells (DCs) by antagonizing type I IFN-mediated phosphorylation of STAT1 and STAT2 (65). Another study showed that Zika virus infection impairs the induction of type I IFNs and that the viral NS5 protein mediates the degradation of STATs in the proteasome (66).…”

Section: Zika Virus Escapes Nk Cell Detectionmentioning

confidence: 99%

Zika Virus Escapes NK Cell Detection by Upregulating Major Histocompatibility Complex Class I Molecules

Glasner

Oiknine‐Djian

Weisblum

et al. 2017

NK cells are innate lymphocytes that participate in many immune processes encompassing cancer, bacterial and fungal infection, autoimmunity, and even pregnancy and that specialize in antiviral defense. NK cells express inhibitory and activating receptors and kill their targets when activating signals overpower inhibitory signals. The NK cell inhibitory receptors include a uniquely diverse array of proteins named killer cell immunoglobulin-like receptors (KIRs), the CD94 family, and the leukocyte immunoglobulin-like receptor (LIR) family. The NK cell inhibitory receptors recognize mostly major histocompatibility complex (MHC) class I (MHC-I) proteins. Zika virus has recently emerged as a major threat due to its association with birth defects and its pandemic potential. How Zika virus interacts with the immune system, and especially with NK cells, is unclear. Here we show that Zika virus infection is barely sensed by NK cells, since little or no increase in the expression of activating NK cell ligands was observed following Zika infection. In contrast, we demonstrate that Zika virus infection leads to the upregulation of MHC class I proteins and consequently to the inhibition of NK cell killing. Mechanistically, we show that MHC class I proteins are upregulated via the RIGI-IRF3 pathway and that this upregulation is mediated via beta interferon (IFN-␤). Potentially, countering MHC class I upregulation during Zika virus infection could be used as a prophylactic treatment against Zika virus.IMPORTANCE NK cells are innate lymphocytes that recognize and eliminate various pathogens and are known mostly for their role in controlling viral infections. NK cells express inhibitory and activating receptors, and they kill or spare their targets based on the integration of inhibitory and activating signals. Zika virus has recently emerged as a major threat to humans due to its pandemic potential and its association with birth defects. The role of NK cells in Zika virus infection is largely unknown. Here we demonstrate that Zika virus infection is almost undetected by NK cells, as evidenced by the fact that the expression of activating ligands for NK cells is not induced following Zika infection. We identified a mechanism whereby Zika virus sensing via the RIGI-IRF3 pathway resulted in IFN-␤-mediated upregulation of MHC-I molecules and inhibition of NK cell activity. Countering MHC class I upregulation and boosting NK cell activity may be employed as prophylactic measures to combat Zika virus infection.KEYWORDS Zika virus, MHC class I, NK cells, NK escape mechanisms N K cells are lymphocytes belonging to the innate immune system. NK cells participate in many immunological activities, from killing cancerous cells (1-7) and fighting bacteria (8-10) and fungi (11) to playing roles in allergy (12) and graft-versushost disease (13). NK cells also play roles in autoimmunity (14-18) and pregnancy (19).