Persistence Of Zika Virus Research Articles

Zika virus infection of first trimester trophoblast cells affects cell migration, metabolism and immune homeostasis control.

Zika virus (ZIKV) re-emerged after circulating almost undetected for many years and the last spread in 2015 was the major outbreak reported. ZIKV infection was associated with congenital fetal growth anomalies such as microcephaly, brain calcifications, and low birth weight related to fetal growth restriction. In this study, we investigated the effect of ZIKV infection on first trimester trophoblast cell function and metabolism. We also studied the interaction of trophoblast cells with decidual immune populations. Results presented here demonstrate that ZIKV infection triggered a strong antiviral response in first trimester cytotrophoblast-derived cells, impaired cell migration, increased glucose uptake and GLUT3 expression, and reduced brain derived neurotrophic factor (BDNF) expression. ZIKV infection also conditioned trophoblast cells to favor a tolerogenic response since an increased recruitment of CD14+ monocytes bearing an anti-inflammatory profile, increased CD4+ T cells and NK CD56Dim and NK CD56Bright populations and an increment in the population CD4+ FOXP3+ IL-10+ cells was observed. Interestingly, when ZIKV infection of trophoblast cells occurred in the presence of the vasoactive intestinal peptide (VIP) there was lower detection of viral RNA and reduced toll-like receptor-3 and viperin messenger RNA expression, along with reduced CD56Dim cells trafficking to trophoblast conditioned media. The effects of ZIKV infection on trophoblast cell function and immune-trophoblast interaction shown here could contribute to defective placentation and ZIKV persistence at the fetal-maternal interface. The inhibitory effect of VIP on ZIKV infection of trophoblast cells highlights its potential as a candidate molecule to interfere ZIKV infection during early pregnancy.

Persistent Zika Virus Clinical Susceptibility despite Reduced Viral Burden in Mice with Expanded Virus-Specific CD8+ T Cells Primed by Recombinant Listeria monocytogenes.

Vaccines against Zika virus (ZIKV) infection that target CD8+ T cells are of considerable interest because Abs may enhance infection susceptibility. However, whether CD8+ T cells are protective or promote susceptibility to clinical infection symptoms remains uncertain. To more precisely investigate ZIKV-specific CD8+ T cells in isolation, we engineered a Listeria monocytogenes-based vector to express a single MHC class I-restricted immune dominant peptide, E294-302, from ZIKV envelope protein. We show accumulation of activated ZIKV-specific CD8+ T cells primed by recombinant L. monocytogenes is associated with reductions in circulating virus levels after ZIKV challenge in type I IFN receptor-deficient mice and wildtype mice administered neutralizing Abs against type I IFN receptor. Interestingly, susceptibility to ZIKV clinical infection including weight loss and mortality each persists and is neither significantly improved nor worsened compared with isogenic L. monocytogenes-primed control mice. These data demonstrating persistent ZIKV clinical susceptibility despite reduced viral burden in mice with expanded virus-specific CD8+ T cells highlights the need for targeting other adaptive immune components in developing vaccines against ZIKV infection.

Zika virus RNA and IgM persistence in blood compartments and body fluids: a prospective observational study

Characterisation of the dynamics of Zika virus persistence following acute infection is needed to inform blood donor and diagnostic testing policies and understand the natural history of Zika virus infection. We aimed to characterise the natural history, persistence, and clinical outcomes of Zika virus infection through a prospective study in initially asymptomatic Zika virus RNA-positive blood donors. Zika virus-infected blood donors identified through Zika virus nucleic acid amplification test (NAAT) screening at three blood collection organisations in the USA were enrolled into a 1-year follow-up study, with blood and body fluid samples and detailed symptom data collected at up to seven visits. All samples were tested for Zika virus RNA by real-time PCR (rtPCR); follow-up plasma, whole blood, and urine were also tested by replicate NAAT. Plasma was tested for flavivirus-specific IgM and IgG by ELISA. Zika virus RNA persistence for each assay or sample type and plasma antibody persistence from estimated date of plasma NAAT-detectable infection were calculated from follow-up data using survival statistical methods. Between July 6, 2016 and March 7, 2017, we enrolled 53 participants. From the estimated date of plasma NAAT-detectable infection, Zika virus RNA was detectable in plasma for 9·9 days (95% CI 8·1-12·0), in red blood cells for 95·4 days (62·8-129·1), and in whole blood for 73·5 days (39·8-107·5). Replicate NAATs (one or more of eight replicates positive) extended detection of Zika virus RNA in plasma to 34·8 days (19·9-56·2) and in whole blood (at least one of two tests positive) to 104·8 days (76·7-129·9). Urine was rtPCR reactive up to 14·5 days (10·5-20·3) and saliva up to 26·4 days (19·7-38·7). Zika virus IgM persisted for 237·7 days (128·7-459·5) from estimated time since plasma NAAT-detectable infection. Zika virus RNA fell below detectable limits more rapidly in the saliva of participants with pre-existing dengue virus IgG than in those without. Of 25 donors identified pre-seroconversion with symptom data at the first or second study visit, 16 (64%) developed multiple Zika virus-related symptoms after asymptomatic index donations, compared with nine (36%) of 25 donors detected after seroconversion. Determination of viral marker persistence is enhanced by follow-up of blood donors who are pre-symptomatic or asymptomatic, Zika virus RNA-positive, and antibody negative. Zika virus RNA persists in red blood cells for several months following clearance from plasma and body fluids, and replicate, highly sensitive NAATs extend RNA detection in all compartments. Whole blood testing can extend detection of acute infection for diagnostics and monitoring of pregnant women, sexual partners, and travellers. National Heart, Lung, and Blood Institute, Biomedical Advanced Research and Development Authority.

Zika virus tropism during early infectionof thetesticular interstitium and its role in viral pathogenesis in the testes.

Sexual transmission and persistence of Zika virus (ZIKV) in the testes pose new challenges for controlling virus outbreaks and developing live-attenuated vaccines. It has been shown that testicular infection of ZIKV is initiated in the testicular interstitium, followed by spread of the virus in the seminiferous tubules. This leads to testicular damage and/or viral dissemination into the epididymis and eventually into semen. However, it remains unknown which cell types are targeted by ZIKV in the testicular interstitium, and what is the specific order of infectious events leading to ZIKV invasion of the seminiferous tubules. Here, we demonstrate that interstitial leukocytes expressing mir-511-3p microRNA are the initial targets of ZIKV in the testes, and infection of mir-511-3p-expressing cells in the testicular interstitium is necessary for downstream infection of the seminiferous tubules. Mir-511-3p is expressed concurrently with CD206, a marker of lineage 2 (M2) macrophages and monocyte derived dendritic cells (moDCs). Selective restriction of ZIKV infection of CD206-expressing M2 macrophages/moDCs results in the attenuation of macrophage–associated inflammatory responses in vivo and prevents the disruption of the Sertoli cell barrier in vitro. Finally, we show that targeting of viral genome for mir-511-3p significantly attenuates early ZIKV replication not only in the testes, but also in many peripheral organs, including spleen, epididymis, and pancreas. This incriminates M2 macrophages/moDCs as important targets for visceral ZIKV replication following hematogenous dissemination of the virus from the site of infection.

Zika virus dysregulates human Sertoli cell proteins involved in spermatogenesis with little effect on tight junctions.

Zika virus (ZIKV), a neglected tropical disease until its re-emergence in 2007, causes microcephaly in infants and Guillain-Barré syndrome in adults. Its re-emergence and spread to more than 80 countries led the World Health Organization in 2016 to declare a Public Health Emergency. ZIKV is mainly transmitted by mosquitos, but can persist in infected human male semen for prolonged periods and may be sexually transmitted. Testicular Sertoli cells support ZIKV replication and may be a reservoir for persistent ZIKV infection. Electrical impedance analyses indicated ZIKV infection rapidly disrupted Vero cell monolayers but had little effect upon human Sertoli cells (HSerC). We determined ZIKV-induced proteomic changes in HSerC using an aptamer-based multiplexed technique (SOMAscan) targeting >1300 human proteins. ZIKV infection caused differential expression of 299 proteins during three different time points, including 5 days after infection. Dysregulated proteins are involved in different bio-functions, including cell death and survival, cell cycle, maintenance of cellular function, cell signaling, cellular assembly, morphology, movement, molecular transport, and immune response. Many signaling pathways important for maintenance of HSerC function and spermatogenesis were highly dysregulated. These included IL-6, IGF1, EGF, NF-κB, PPAR, ERK/MAPK, and growth hormone signaling. Down-regulation of the PPAR signaling pathway might impact cellular energy supplies. Upstream molecule analysis also indicated microRNAs involved in germ cell development were downregulated by infection. Overall, this study leads to a better understanding of Sertoli cellular mechanisms used by ZIKV during persistent infection and possible ZIKV impacts on spermatogenesis.

New Challenge for Zika Virus Infection: Human Reservoirs?

Zika virus (ZIKV) is considered to cause an acute self-limited infection in adults, and microcephaly in fetus. Presence of the virus for long periods has been detected in body fluids; however, persistent viremia in serum for more than 1 year has not yet been reported. We have investigated persistence of ZIKV in serum samples of 77 subjects who were infected by the virus between 18 months and 3 years before the start of this study. The subjects included children with microcephaly and their parents. Serum samples were subjected to routine RT-qPCR assay for ZIKV, Chikungunya virus, and Dengue virus. From the 77 subjects, five showed positive for the presence of ZIKV particles by RT-qPCR, including four members of the same family. Viral isolation in Vero cells and C6/36 cells confirmed the result and showed the viral particles were active. We have detected viremia in healthy carriers up to 3 years after symptom onset. Humans acting as potential viral reservoirs have major implication for the current understanding of ZIKV infection.

Zika virus infection in the genital tract of non-pregnant females: a systematic review.

ABSTRACTThis review provides a general overview on the positivity and persistence of Zika virus (ZIKV) in female genital tract (FGT) of non-pregnant women and animals, as well as in cell cultures, and its influence on FGT health. We performed a systematic review based on the PRISMA statement to identify studies focused on “Zika virus” and “non-pregnant female” in PubMed, Embase, Scopus Scholar and Web of Knowledge databases of full-text papers and abstracts published in English, with no restrictions regarding the initial date of publication, up to August 2019. Our search terms yielded 625 records, that were 108 after removal of duplicates, leaving 517 items for title and abstract reviews. Of these, 475 did not meet the inclusion criteria, leaving 42 records for full-text review and resulting in the exclusion of 6 additional records. The remaining 36 met our inclusion criteria. Variations were observed regarding the presence and persistence of ZIKV in lower and upper genital samples. However, the FGT was the place in which ZIKV RNA has been detected, sometimes for relatively long periods, even after the clearance from blood and urine. In addition to the vagina and cervix, the endometrium, uterus and ovary (oocytes and follicles) could also be involved in persistent ZIKV infections. Further prospective studies are needed to assess the effect of ZIKV on FGT health.

Use of Primary Human Fetal Astrocytes and Tissue Explants as Ex Vivo Models to Study Zika Virus Infection of the Developing Brain.

Zika virus (ZIKV) infection during pregnancy can result in congenital Zika syndrome which is characterized by microcephaly and other neurodevelopmental disorders. In this chapter, we describe methods to model ex vivo ZIKV infection in astrocytes and tissue explants from human fetal brain. These cell- and tissue-based platforms have been useful to elucidate mechanisms of ZIKV persistence and might lead to important clues about virus-induced neuropathogenesis. In addition, these ex vivo model systems allow researchers to conduct drug discovery and development experiments in more representative settings of the developing human brain.

Isolation and Detection of Zika Virus-Infected Rhesus Macaques Lymph Node Cells and Splenocytes.

Zika virus (ZIKV) is a mosquito-borne viral infection that is shed in biological fluids promoting vertical and sexual transmission. Recent outbreaks of ZIKV have been associated with an increase in adult and fetal infection-related diseases. ZIKV infection in rhesus macaques is considered a robust animal model for studying Zika viral infection dynamics and fetal disease. A compelling feature of ZIKV is its ability to persist for long periods of time in immunocompetent hosts and during pregnancy, which may be linked to adverse infection outcomes. One consistent site of viral persistence is lymph node tissues. Utilizing this feature of ZIKV infection could be useful to diagnose viral persistence and to improve efficacy evaluation of antiviral vaccines and therapeutics, as well as for diagnostic and prognostic assessments in humans. We have developed a protocol to isolate lymph node cells using cell type-specific antibody-magnetic bead techniques followed by a one-step qRT-PCR detection of Zika virus RNA. This method fostered the identification of dendritic cells, macrophages, and B cells from the lymph node and spleen as harboring persistent ZIKV RNA.

Zika Virus Causes Acute and Chronic Prostatitis in Mice and Macaques.

Sexual transmission and persistence of Zika virus (ZIKV) in the male reproductive tract has raised concerned for potential damaging effects on function. Animal studies have demonstrated that ZIKV virus can infect and damage the testis and epididymis, and these results has been correlated to lower sperm counts in ZIKV-infected humans. The prostate plays a vital role in the male reproductive tract, with acute and chronic prostatitis linked to male infertility. In this study, we evaluated the effects of ZIKV virus on the prostate in mice and nonhuman primates. In mice, ZIKV infected the prostate and triggered inflammation that persisted even after virus clearance. Evidence of chronic prostatitis associated with ZIKV infection remained for several months. Similar histological findings were observed in the prostate of ZIKV-infected rhesus macaques. These studies establish that ZIKV replicates in the prostate and can cause acute and chronic inflammatory and proliferative changes in mouse and nonhuman primate models.

High susceptibility, viral dynamics and persistence of South American Zika virus in New World monkey species

South American Zika virus (ZIKV) recently emerged as a novel human pathogen, linked with neurological disorders. However, comparative ZIKV infectivity studies in New World primates are lacking. Two members of the Callitrichidae family, common marmosets (Callithrix jacchus) and red-bellied tamarins (Saguinus labiatus), were highly susceptible to sub-cutaneous challenge with the Puerto Rico-origin ZIKVPRVABC59 strain. Both exhibited rapid, high, acute viraemia with early neuroinvasion (3 days) in peripheral and central nervous tissue. ZIKV RNA levels in blood and tissues were significantly higher in New World hosts compared to Old World species (Macaca mulatta, Macaca fascicularis). Tamarins and rhesus macaques exhibited loss of zonal occludens-1 (ZO-1) staining, indicative of a compromised blood-brain barrier 3 days post-ZIKV exposure. Early, widespread dissemination across multiple anatomical sites distant to the inoculation site preceded extensive ZIKV persistence after 100 days in New and Old World lineages, especially lymphoid, neurological and reproductive sites. Prolonged persistence in brain tissue has implications for otherwise resolved human ZIKV infection. High susceptibility of distinct New World species underscores possible establishment of ZIKV sylvatic cycles in primates indigenous to ZIKV endemic regions. Tamarins and marmosets represent viable New World models for ZIKV pathogenesis and therapeutic intervention studies, including vaccines, with contemporary strains.

Zika Virus Transmission Through Blood Tissue Barriers.

The recent Zika virus (ZIKV) epidemic in the Americas and the Caribbean revealed a new deadly strain of the mosquito-borne virus, which has never been associated with previous outbreaks in Asia. For the first time, widespread ZIKV infection was shown to cause microcephaly and death of newborns, which was most likely due to the mutation acquired during the large outbreak recorded in French Polynesia in 2013–2014. Productive ZIKV replication and persistence has been demonstrated in placenta and fetal brains. Possible association between ZIKV and microcephaly and fetal death has been confirmed using immunocompetent mouse models in vitro and in vivo. Having crossed the placenta, ZIKV directly targets neural progenitor cells (NPCs) in developing human fetus and triggers apoptosis. The embryonic endothelial cells are exceptionally susceptible to ZIKV infection, which causes cell death and tissue necrosis. On the contrary, ZIKV infection does not affect the adult brain microvascular cell morphology and blood–brain barrier function. ZIKV is transmitted primarily by Aedes mosquito bite and is introduced into the placenta/blood through replication at the site of the entry. Also, virus can be transmitted through unprotected sex. Although, multiple possible routes of virus infection have been identified, the exact mechanism(s) utilized by ZIKV to cross the placenta still remain largely unknown. In this review, the current understanding of ZIKV infection and transmission through the placental and brain barriers is summarized.

Comparative Genomics, Infectivity and Cytopathogenicity of American Isolates of Zika Virus that Developed Persistent Infections in Human Embryonic Kidney (HEK293) Cells.

Zika virus (ZIKV) transmission can cause serious fetal neurological abnormalities. ZIKV persistence in various human cells and tissues can serve as infectious reservoirs and post serious threats to public health. The human embryonic kidney (HEK293) cell line with known neuronal developmental properties was readily infected by ZIKV in a strain-dependent fashion. Significant cytopathic effect in HEK293 cells infected by the prototype MR 766 strain of ZIKV resulted in complete loss of cells, while small numbers of HEK293 cells infected by contemporary ZIKV isolates (PRV or FLR strain) continued to survive and regrow to confluency in the culture around two months after initial infection. Most, if not all, of the cells in the two resulting persistently ZIKV-infected HEK293 cell lines tested positive for ZIKV antigen. Compared to HEK293 control cells, the persistently ZIKV-infected HEK293 cells had slower growth rates with some cells undergoing apoptosis in culture. The “persistent ZIKVs” produced constitutively by both PRV and FLR strains ZIKV-infected HEK293 cells had significantly attenuated cell infectivity and/or cytopathogenicity. Comparative genome sequence analyses between the persistent ZIKVs and the original inoculum ZIKVs showed no clonal selection with specific gene mutations in the prolonged process of establishing persistently PRV strain ZIKV-infected HEK293 cells; while selection of ZIKV subclones with mutations in the envelope, protein pr and multiple NS genes was evident in developing persistently FLR strain ZIKV-infected HEK293 cell line. Our study provides molecular insights into the complex interplays of ZIKV and human host cells in establishing ZIKV persistence.

Zika virus antagonizes interferon response in patients and disrupts RIG-I\u2013MAVS interaction through its CARD-TM domains

BackgroundThe emerging threat to global health associated with the Zika virus (ZIKV) epidemics and its link to severe complications highlights a growing need to better understand the pathogenic mechanisms of ZIKV. Accumulating evidence for a critical role of type I interferon (IFN-I) in protecting hosts from ZIKV infection lies in the findings that ZIKV has evolved various strategies to subvert the host defense line by counteracting the early IFN induction or subsequent IFN signaling. Yet, mechanisms underlying the counter-IFN capability of ZIKV and its proteins, which might contribute to the well-recognized broad cellular tropisms and persistence of ZIKV, remain incompletely understood.ResultsUsing RNA sequencing-based transcriptional profiling of whole blood cells isolated from patients acutely infected by ZIKV, we found that transcriptional signature programs of antiviral interferon-stimulated genes and innate immune sensors in ZIKV-infected patients remained inactive as compared to those of healthy donors, suggesting that ZIKV was able to suppress the induction of IFN-I during the natural infection process in humans. Furthermore, by analyzing the molecular interaction in a ZIKV NS4A-overexpression system, or in the context of actual ZIKV infection, we identified that ZIKV NS4A directly bound MAVS and thereby interrupted the RIG-I/MAVS interaction through the CARD-TM domains, leading to attenuated production of IFN-I.ConclusionsOur findings collectively revealed that ZIKV NS4A targeted MAVS and contributed to ZIKV immune evasion through abrogating MAVS-mediated IFN production. These findings obtained from patient studies have added new knowledge and molecular details to our understanding regarding how ZIKV mediates suppression of the IFN-I system and may provide a new basis for the future development of anti-ZIKV strategies.

An update on the aspects of Zika virus infection on male reproductive system.

Zika virus (ZIKV) is mainly transmitted through Aedes mosquito bites, but sexual and post-transfusion transmissions have been reported. During acute infection, ZIKV is detectable in most organs and body fluids including human semen. Although it is not currently epidemic, there is a concern that the virus can still reemerge since the male genital tract might harbor persistent reservoirs that could facilitate viral transmission over extended periods, raising concerns among public health and assisted reproductive technologies(ART) experts and professionals. So far, the consensus is that ZIKV infection in the testes or epididymis might affect sperm development and, consequently, male fertility. Still, diagnostic tests have not yet been adapted to resource-restricted countries. This manuscript provides an updated overview of the cellular and molecular mechanisms of ZIKV infection and reviews data on ZIKV persistence in semen and associated risks to the male reproductive system described in human and animal models studies. We provide an updated summary of the impact of the recent ZIKV outbreak on human-ART, weighing on current recommendations and diagnostic approaches, both available and prospective, with special emphasis on mass spectrometry-based biomarker discovery. In the light of the identified gaps in our accumulated knowledge on the subject, we highlight the importance for couples seeking ART to follow the constantly revised guidelines and the need of specific ZIKV diagnosis tools for semen screening to contain ZIKV virus spread and make ART safer.

Transmission of Zika Virus Through the Rectal Route Leads to Mucosal and Systemic Infection with Reduced Neuropathology in Mice

Zika virus (ZIKV) is a mosquito‐borne flavivirus originally confined to Africa and Asia that has most recently spread to the Americas and the Caribbean. ZIKV circulates in sylvatic and urban transmission cycles and causes asymptomatic infection in most affected individuals, while the rest of the population experiences mild febrile syndrome. In some adults, ZIKV causes neurotropic Guillain–Barré syndrome. Vertical transmission of ZIKV in infected mothers causes fetal growth restriction, microcephaly, and congenital eye disease. There have been reports of infected individuals transmitting ZIKV sexually from male to female, male to male, and a suspected case of female to male. ZIKV has been detected in the semen of infected males months after symptom onset and thus, ZIKV persistence in the semen and testes can increase the risk of viral transmission for men having sex with men (MSM) and between heterosexual partners through rectal route. To further understand the risk of ZIKV acquisition through this route, we established a rectal route of infection model using immunocompromised (Ifnar1−/−) mice to investigate the sexual (rectal) and mosquito (subcutaneous) modes of transmission and their resulting systemic and mucosal responses to infection. Rectal inoculation of ZIKV results in viremia with non‐lethal infection, while establishing active rectal and testicular infection that persists for at least 21 days. We found that after one day of infection, ZIKV infects epithelial cells comprising the mucosal epithelium and dendritic cells within the lamina propria and submucosa. Significantly increased levels of the chemokine CCL2 and CD4+ T‐cell response were observed at 3 and 7 days post‐infection, respectively, relative to the subcutaneously infected group. Moreover, rectal route of infection results in reduced immune cell infiltration and inflammation in the brain with a robust CCL2 and CXCl10 response, while subcutaneous infection caused severe brain pathology and induces a more robust CD8+ T‐cell response. Lastly, at 21 days, the rectal group had specific anti‐ZIKV antiviral response suggesting the role of adaptive immune response in restricting lethal viral infection. Our studies provide comprehensive insight of ZIKV transmission through rectal route and the resulting reduced neuropathology and control of disease progression in mice due to early virological and immunological events following infection of the rectal mucosa.Support or Funding InformationThis research was funded by Cedars‐Sinai Medical Center's Institutional Research Award to V.A., the California Institute for Regenerative Medicine (CIRM) Quest – Discovery Stage Research Projects Grant (DISC2‐10188) to V.A. at UCLA, and the UCLA Interdisciplinary Postdoctoral Training Grant (T32) in Virology and Gene Therapy to L.E.M.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

High susceptibility, viral dynamics and persistence of South American Zika virus in New World monkeys

South American Zika virus (ZIKV) emerged as a novel enzootic pathogen linked with neonatal brain defects and acute neuropathies, its natural history characterised by a sylvatic transmission cycle with arboreal mosquitoes and African primates. Yet infectivity studies in New World primates indigenous to Zika-endemic regions including host range, susceptibility, replication dynamics, tissue tropism and virus persistence are currently lacking. New World species Callithrix jacchus (marmosets) and Saguinus labiatus (red-bellied tamarins) were highly susceptible to sub-cutaneous challenge with South American ZIKVPRVABC59 inducing rapid, high, acute viraemia in each species. Differences in acute phase vRNA in blood were highly statistically significant at day 3 between these New and two Old World species Macaca mulatta (rhesus macaque) and Macaca fascicularis (cynomolgus macaque), Mann-Whitney U testp=0.00058. Comparative quantitative RT-PCR and RNAscope in situ hybridisation analysis of tissue viral copy number and cellular localisation patterns with Old World NHP revealed early, widespread distribution across multiple skin biopsies distant to the inoculation site, lymphoid organs, reproductive sites and the brain. While viraemia was cleared from blood by day 42 in all individuals, ZIKV persistence in most tissues was identified 100 days post-inoculation. Early neuroinvasion and persistence, following acutely resolved infection characterises ZIKV susceptibility in multiple hosts, especially New World species. Establishment of a ZIKV sylvatic cycle in the Americas may provide persistent animal reservoirs for future outbreak resurgence. New World monkeys represent viable models to understand ZIKV pathogenesis, potential therapeutic interventions and vaccine development strategies.

Persistence and clinical relevance of Zika virus in the male genital tract.

Zika virus (ZIKV) is a re-emerging mosquito-transmitted flavivirus associated with congenital abnormalities in newborns and with Guillain-Barré syndrome in adults. The virus can also be sexually transmitted and can persist in the male genital tract. Studies evaluating the kinetics of ZIKV in seminal shedding of men who have been infected, as well as in animal and cellular models of infection, have shown that, in addition to the testis and epididymis, the prostate and seminal vesicles could also be involved in persistent ZIKV infection. Additionally, some studies have reported that men infected with ZIKV can present with genitourinary symptoms such as haematospermia, prostatitis, painful ejaculation, penile discharge, and oligospermia; however, little is known about the effect of ZIKV on fertility. Understanding the mechanisms that underlie persistent ZIKV infections in men is crucial to developing guidelines, effective vaccines, and therapies.

A 'Furry-Tale' of Zika Virus Infection: What Have We Learned from Animal Models?

The worldwide attention that the Zika virus (ZIKV) attracted, following its declaration as a Public Health Emergency of International concern by WHO in 2016, has led to a large collective effort by the international scientific community to understand its biology. Despite the mild symptoms caused by ZIKV in most infected people, the virus displays a number of worrying features, such as its ability to cause transplacental infection, fetal abnormalities and vector independent transmission through body fluids. In addition, the virus has been associated with the induction of Guillain-Barre syndrome in a number of infected individuals. With travelling, the virus has spread outside the original ZIKV endemic areas making it imperative to find ways to control it. Thus far, the large number of animal models developed to study ZIKV pathogenesis have proven to be valuable tools in understanding how the virus replicates and manifests itself in the host, its tissue tropism and the type of immune responses it induces. Still, vital questions, such as the molecular mechanisms of ZIKV persistence and the long-term consequences of ZIKV infection in the developing brain, remain unanswered. Here, we reviewed and discussed the major and most recent findings coming from animal studies and their implications for a ZIKV vaccine design.

Routes of Zika virus dissemination in the testis and epididymis of immunodeficient mice

Sexual transmission and persistence of Zika virus (ZIKV) in the male reproductive tract (MRT) poses new challenges for controlling virus outbreaks and developing live-attenuated vaccines. To elucidate routes of ZIKV dissemination in the MRT, we here generate microRNA-targeted ZIKV clones that lose the infectivity for (1) the cells inside seminiferous tubules of the testis, or (2) epithelial cells of the epididymis. We trace ZIKV dissemination in the MRT using an established mouse model of ZIKV pathogenesis. Our results support a model in which ZIKV infects the testis via a hematogenous route, while infection of the epididymis can occur via two routes: (1) hematogenous/lymphogenous and (2) excurrent testicular. Co-targeting of the ZIKV genome with brain-, testis-, and epididymis-specific microRNAs restricts virus infection of these organs, but does not affect virus-induced protective immunity in mice and monkeys. These defined alterations of ZIKV tropism represent a rational design of a safe live-attenuated ZIKV vaccine.