Zika Virus Infection In Humans Research Articles

Mutational analyses, pharmacophore-based inhibitor design and in silico validation for Zika virus NS3-helicase

Zika virus is responsible for causing Zika infections and was declared as a public health emergency of international concern in February 2016. The Zika virus NS3-helicase is a viable drug target for the design of inhibitors due to its essential role in the replication of viral genome. The viral RNA is unwound by the NS3-helicase in order to enable the reproduction of viral genome by the NS5 protein. Zika virus infections in humans are being reported for the last 15 years. We have therefore carried out amino acid mutational analyses of NS3-helicase. NS3-helicase has two crucial binding sites: the ATP and RNA binding sites. The cofactor-ATP based pharmacophore was generated for virtual screening of ZINC database using Pharmit server, that is followed by molecular docking and molecular dynamics simulations of potential hits as probable Zika virus NS3-helicase inhibitors at the cofactor binding site. The drug-like properties of the molecules were analysed and, DFT calculations were performed on the five best molecules to reveal their stability in solvent phase compared to gas phase, the HOMO and LUMO and electrostatic potential maps to analyze the electronic and geometric characteristics. These are significant findings towards the discovery of new inhibitors of Zika virus NS3-helicase, a promising drug target to treat the Zika virus infection. Communicated by Ramaswamy H. Sarma

The distinguishing NS5-M114V mutation in American Zika virus isolates has negligible impacts on virus replication and transmission potential.

During 2015–2016, outbreaks of Zika virus (ZIKV) occurred in Southeast Asia and the Americas. Most ZIKV infections in humans are asymptomatic, while clinical manifestation is usually a self-limiting febrile disease with maculopapular rash. However, ZIKV is capable of inducing a range of severe neurological complications collectively described as congenital Zika syndrome (CZS). Notably, the scale and magnitude of outbreaks in Southeast Asia were significantly smaller compared to those in the Americas. Sequence comparison between epidemic-associated ZIKV strains from Southeast Asia with those from the Americas revealed a methionine to valine substitution at residue position 114 of the NS5 protein (NS5-M114V) in all the American isolates. Using an American isolate of ZIKV (Natal), we investigated the impact of NS5-M114V mutation on virus replication in cells, virulence in interferon (IFN) α/β receptor knockout (Ifnar-/-) mice, as well as replication and transmission potential in Aedes aegypti mosquitoes. We demonstrated that NS5-M114V mutation had insignificant effect on ZIKV replication efficiency in cells, its ability to degrade STAT2, and virulence in vivo, albeit viremia was slightly prolonged in mice. Furthermore, NS5-M114V mutation decreased mosquito infection and dissemination rates but had no effect on virus secretion into the saliva. Taken together, our findings support the notion that NS5-M114V mutation is unlikely to be a major determinant for virus replication and transmission potential.

Molecular Approaches for the Validation of the Baboon as a Nonhuman Primate Model for the Study of Zika Virus Infection.

Nonhuman primates (NHP) are particularly important for modeling infections with viruses that do not naturally replicate in rodent cells. Zika virus (ZIKV) has been responsible for sporadic epidemics, but in 2015 a disseminated outbreak of ZIKV resulted in the World Health Organization declaring it a global health emergency. Since the advent of this last epidemic, several NHP species, including the baboon, have been utilized for modeling and understanding the complications of ZIKV infection in humans; several health issues related to the outcome of infection have not been resolved yet and require further investigation. This study was designed to validate, in baboons, the molecular signatures that have previously been identified in ZIKV-infected humans and macaque models. We performed a comprehensive molecular analysis of baboons during acute ZIKV infection, including flow cytometry, cytokine, immunological, and transcriptomic analyses. We show here that, similar to most human cases, ZIKV infection of male baboons tends to be subclinical, but is associated with a rapid and transient antiviral interferon-based response signature that induces a detectable humoral and cell-mediated immune response. This immunity against the virus protects animals from challenge with a divergent ZIKV strain, as evidenced by undetectable viremia but clear anamnestic responses. These results provide additional support for the use of baboons as an alternative animal model to macaques and validate omic techniques that could help identify the molecular basis of complications associated with ZIKV infections in humans.

Japanese Encephalitis Virus Vaccination Elicits Cross-Reactive HLA-Class I-Restricted CD8 T Cell Response Against Zika Virus Infection.

Japanese encephalitis virus (JEV) exposure or vaccination could elicit cross-reactive CD8 T cell immunity against heterologous flaviviruses in humans. In addition, cross-reactive CD8 T cells induced by dengue virus (DENV) have been shown to play a protective role against Zika virus (ZIKV). However, how JEV exposure or vaccination affects ZIKV infection in humans remains unclear. In this report, epitope prediction algorithms were used to predict the cross-reactive CD8 T cell epitope restricted to human HLA between JEV and ZIKV. We found that these predicted CD8 T cell epitopes are immunogenic and cross-reactive in humanized HLA transgenic mice. Moreover, JEV vaccine immunization provided cross-protection against ZIKV infection. Furthermore, CD8 T cells were involved in the protection against ZKIV infection in vivo. Our results have an important clinical implication that vaccination with JEV SA14-14-2 may provide protection against ZIKV infection in humans.

Health-Related Quality of Life in Neurological Disorders Most Commonly Associated With Zika-Virus Infection: A Systematic Review.

In this systematic review, we synthesize the current evidence on health-related quality of life (HRQoL) for the two of the most relevant outcomes of Zika virus infection in humans, microcephaly and Guillain-Barré Syndrome (GBS). We searched the following databases: MEDLINE, Embase, CINAHL, LILACS, WHO's ICTRP clinical trials registries database and PROSPERO. Search terms included quality of life, microcephaly, and Guillain-Barré Syndrome. We included primary studies where HRQoL was quantitatively assessed for microcephaly and GBS using validated instruments. We used the Joanna Briggs Institute Critical Appraisal Tools to assess the risk of bias of individual studies. From a total of 1,657 abstracts screened and 66 full texts reviewed, 21 studies met the eligibility criteria; one study for microcephaly and 20 for GBS. Adjusted disutilities for microcephaly compared to a normative childhood utility ranged from -0.745 to -0.820. For GBS, time traded-off the expected lifetime ranged from 16 days to 3 years. HRQoL follows the clinical course of GBS, with lower scores in the first months, recovery within the first year post onset, and stabilization after one year. Included studies reported a wide range of HRQoL for GBS, due in part to a high level of heterogeneity in methods, inclusion criteria, follow-up and reporting of results. Opportunities exist for primary studies assessing the longitudinal HRQoL over the entire course of the diseases to inform clinical practice, economic evaluations and health policy.

Modeling mosquito-borne and sexual transmission of Zika virus in an enzootic host, the African green monkey.

Mosquito-borne and sexual transmission of Zika virus (ZIKV), a TORCH pathogen, recently initiated a series of large epidemics throughout the Tropics. Animal models are necessary to determine transmission risk and study pathogenesis, as well screen antivirals and vaccine candidates. In this study, we modeled mosquito and sexual transmission of ZIKV in the African green monkey (AGM). Following subcutaneous, intravaginal or intrarectal inoculation of AGMs with ZIKV, we determined the transmission potential and infection dynamics of the virus. AGMs inoculated by all three transmission routes exhibited viremia and viral shedding followed by strong virus neutralizing antibody responses, in the absence of clinical illness. All four of the subcutaneously inoculated AGMs became infected (mean peak viremia: 2.9 log10 PFU/mL, mean duration: 4.3 days) and vRNA was detected in their oral swabs, with infectious virus being detected in a subset of these specimens. Although all four of the intravaginally inoculated AGMs developed virus neutralizing antibody responses, only three had detectable viremia (mean peak viremia: 4.0 log10 PFU/mL, mean duration: 3.0 days). These three AGMs also had vRNA and infectious virus detected in both oral and vaginal swabs. Two of the four intrarectally inoculated AGMs became infected (mean peak viremia: 3.8 log10 PFU/mL, mean duration: 3.5 days). vRNA was detected in oral swabs collected from both of these infected AGMs, and infectious virus was detected in an oral swab from one of these AGMs. Notably, vRNA and infectious virus were detected in vaginal swabs collected from the infected female AGM (peak viral load: 7.5 log10 copies/mL, peak titer: 3.8 log10 PFU/mL, range of detection: 5–21 days post infection). Abnormal clinical chemistry and hematology results were detected and acute lymphadenopathy was observed in some AGMs. Infection dynamics in all three AGM ZIKV models are similar to those reported in the majority of human ZIKV infections. Our results indicate that the AGM can be used as a surrogate to model mosquito or sexual ZIKV transmission and infection. Furthermore, our results suggest that AGMs are likely involved in the enzootic maintenance and amplification cycle of ZIKV.

A direct-acting antiviral drug abrogates viremia in Zika virus-infected rhesus macaques.

Zika virus infection in humans has been associated with serious reproductive and neurological complications. At present, no protective antiviral drug treatment is available. Here, we describe the testing and evaluation of the antiviral drug, galidesivir, against Zika virus infection in rhesus macaques. We conducted four preclinical studies in rhesus macaques to assess the safety, antiviral efficacy, and dosing strategies for galidesivir (BCX4430) against Zika virus infection. We treated 70 rhesus macaques infected by various routes with the Puerto Rico or Thai Zika virus isolates. We evaluated galidesivir administered as early as 90 min and as late as 72 hours after subcutaneous Zika virus infection and as late as 5 days after intravaginal infection. We evaluated the efficacy of a range of galidesivir doses with endpoints including Zika virus RNA in plasma, saliva, urine, and cerebrospinal fluid. Galidesivir dosing in rhesus macaques was safe and offered postexposure protection against Zika virus infection. Galidesivir exhibited favorable pharmacokinetics with no observed teratogenic effects in rats or rabbits at any dose tested. The antiviral efficacy of galidesivir observed in the blood and central nervous system of infected animals warrants continued evaluation of this compound for the treatment of flaviviral infections.

Clinical performance evaluation of five commercial IgM tests for diagnostic of Zika virus infection

Background: Zika Virus (ZIKV) is an emerging mosquito-transmitted flavivirus currently causing large epidemics and represents a global public health. Most ZIKV infections in humans are asymptomatic or mild with self-limiting clinical manifestations. Certainty, an available and sustainable surveillance for risk individual groups to ZIKV infection it is necessary and serological methods offer a good alternative.

A high infectious simian adenovirus type 23 vector based vaccine efficiently protects common marmosets against Zika virus infection

Zika virus (ZIKV) has spread in many countries or territories causing severe neurologic complications with potential fatal outcomes. The small primate common marmosets are susceptible to ZIKV, mimicking key features of human infection. Here, a novel simian adenovirus type 23 vector-based vaccine expressing ZIKV pre-membrane-envelope proteins (Sad23L-prM-E) was produced in high infectious titer. Due to determination of immunogenicity in mice, a single-dose of 3×108 PFU Sad23L-prM-E vaccine was intramuscularly inoculated to marmosets. This vaccine raised antibody titers of 104.07 E-specific and 103.13 neutralizing antibody (NAb), as well as robust specific IFN-γ secreting T-cell response (1,219 SFCs/106 cells) to E peptides. The vaccinated marmosets, upon challenge with a high dose of ZIKV (105 PFU) six weeks post prime immunization, reduced viremia by more than 100 folds, and the low level of detectable viral RNA (<103 copies/ml) in blood, saliva, urine and feces was promptly eliminated when the secondary NAb (titer >103.66) and T-cell response (>726 SFCs/106 PBMCs) were acquired 1-2 weeks post exposure to ZIKV, while non-vaccinated control marmosets developed long-term high titer of ZIKV (105.73 copies/ml) (P<0.05). No significant pathological lesions were observed in marmoset tissues. Sad23L-prM-E vaccine was detectable in spleen, liver and PBMCs at least 4 months post challenge. In conclusion, a prime immunization with Sad23L-prM-E vaccine was able to protect marmosets against ZIKV infection when exposed to a high dose of ZIKV. This Sad23L-prM-E vaccine is a promising vaccine candidate for prevention of ZIKV infection in humans.

Evaluating Zika Virus Pathogenesis in Immunocompromised Mice.

Mouse models of Zika virus (ZIKV) infection, which recapitulate certain aspects of ZIKV infection in humans, have demonstrated their utility for studying ZIKV pathogenesis and for the initial screening of antivirals, experimental therapeutics, and candidate vaccines for protective efficacy against ZIKV infection. In this chapter we outline the available mouse models and describe the evaluation of ZIKV pathogenesis in an immunocompromised mouse model of ZIKV infection.

Zika Virus Infection, Reproductive Organ Targeting, and Semen Transmission in the Male Olive Baboon.

Zika virus (ZIKV) infection in pregnant women is a serious threat to the development and viability of the fetus. The primary mode of ZIKV transmission to humans is through mosquito bites, but sexual transmission has also been well documented in humans. However, little is known of the short- and long-term effects of ZIKV infection on the human male reproductive system. This study examines the effects of ZIKV infection on the male reproductive organs and semen and the immune response of the olive baboon (Papio anubis). Nine mature male baboons were infected with ZIKV (French Polynesian strain) subcutaneously. Six animals were euthanized at 41 days, while three animals were euthanized at 10 or 11 days postinfection (dpi). Viremia and clinical evidence of infection were present in all nine baboons. ZIKV RNA was present in the semen of five of nine baboons. ZIKV was present in the testes of two of three males euthanized at 10 or 11 dpi, but in none of six males at 41 dpi. Immunofluorescence of testes suggested the presence of ZIKV in sperm progenitor cells, macrophage penetration of seminiferous tubules, and increased tumor necrosis factor alpha (TNF-α), particularly in vascular walls. These data demonstrate that male olive baboons approximate the male human ZIKV response, including viremia, the adaptive immune response, and persistent ZIKV in semen. Although gross testicular pathology was not seen, the demonstrated breach of the testes-blood barrier and targeting of spermatogenic precursors suggest possible long-term implications in ZIKV-infected primates.IMPORTANCE Zika virus (ZIKV) is an emerging flavivirus spread through mosquitoes and sexual contact. ZIKV infection during pregnancy can lead to severe fetal outcomes, including miscarriage, fetal death, preterm birth, intrauterine growth restriction, and fetal microcephaly, collectively known as congenital Zika syndrome. Therefore, it is important to understand how this virus spreads, as well as the resulting pathogenesis in translational animal models that faithfully mimic ZIKV infection in humans. Such models will contribute to the future development of efficient therapeutics and prevention mechanisms. Through our previous work in olive baboons, we developed a nonhuman primate model that is permissive to ZIKV infection and transfers the virus vertically from mother to fetus, modeling human observations. The present study contributes to understanding of ZIKV infection in male baboon reproductive tissues and begins to elucidate how this may affect fertility, reproductive capacity, and sexual transmission of the virus.

Vector distribution and transmission risk of the Zika virus in South and Central America.

BackgroundZika is of great medical relevance due to its rapid geographical spread in 2015 and 2016 in South America and its serious implications, for example, certain birth defects. Recent epidemics urgently require a better understanding of geographic patterns of the Zika virus transmission risk. This study aims to map the Zika virus transmission risk in South and Central America. We applied the maximum entropy approach, which is common for species distribution modelling, but is now also widely in use for estimating the geographical distribution of infectious diseases.MethodsAs predictor variables we used a set of variables considered to be potential drivers of both direct and indirect effects on the emergence of Zika. Specifically, we considered (a) the modelled habitat suitability for the two main vector species Aedes aegypti and Ae. albopictus as a proxy of vector species distributions; (b) temperature, as it has a great influence on virus transmission; (c) commonly called evidence consensus maps (ECM) of human Zika virus infections on a regional scale as a proxy for virus distribution; (d) ECM of human dengue virus infections and, (e) as possibly relevant socio-economic factors, population density and the gross domestic product.ResultsThe highest values for the Zika transmission risk were modelled for the eastern coast of Brazil as well as in Central America, moderate values for the Amazon basin and low values for southern parts of South America. The following countries were modelled to be particularly affected: Brazil, Colombia, Cuba, Dominican Republic, El Salvador, Guatemala, Haiti, Honduras, Jamaica, Mexico, Puerto Rico and Venezuela. While modelled vector habitat suitability as predictor variable showed the highest contribution to the transmission risk model, temperature of the warmest quarter contributed only comparatively little. Areas with optimal temperature conditions for virus transmission overlapped only little with areas of suitable habitat conditions for the two main vector species. Instead, areas with the highest transmission risk were characterised as areas with temperatures below the optimum of the virus, but high habitat suitability modelled for the two main vector species.ConclusionModelling approaches can help estimating the spatial and temporal dynamics of a disease. We focused on the key drivers relevant in the Zika transmission cycle (vector, pathogen, and hosts) and integrated each single component into the model. Despite the uncertainties generally associated with modelling, the approach applied in this study can be used as a tool and assist decision making and managing the spread of Zika.

Identification of Novel Natural Products as Effective and Broad-Spectrum Anti-Zika Virus Inhibitors.

Zika virus (ZIKV) infection during pregnancy leads to severe congenital Zika syndrome, which includes microcephaly and other neurological malformations. No therapeutic agents have, so far, been approved for the treatment of ZIKV infection in humans; as such, there is a need for a continuous effort to develop effective and safe antiviral drugs to treat ZIKV-caused diseases. After screening a natural product library, we have herein identified four natural products with anti-ZIKV activity in Vero E6 cells, including gossypol, curcumin, digitonin, and conessine. Except for curcumin, the other three natural products have not been reported before to have anti-ZIKV activity. Among them, gossypol exhibited the strongest inhibitory activity against almost all 10 ZIKV strains tested, including six recent epidemic human strains. The mechanistic study indicated that gossypol could neutralize ZIKV infection by targeting the envelope protein domain III (EDIII) of ZIKV. In contrast, the other natural products inhibited ZIKV infection by targeting the host cell or cell-associated entry and replication stages of ZIKV. A combination of gossypol with any of the three natural products identified in this study, as well as with bortezomib, a previously reported anti-ZIKV compound, exhibited significant combinatorial inhibitory effects against three ZIKV human strains tested. Importantly, gossypol also demonstrated marked potency against all four serotypes of dengue virus (DENV) human strains in vitro. Taken together, this study indicates the potential for further development of these natural products, particularly gossypol, as the lead compound or broad-spectrum inhibitors against ZIKV and other flaviviruses, such as DENV.

Health outcomes associated with Zika virus infection in humans: a systematic review of systematic reviews

ObjectiveWith the emergence of Zika virus (ZIKV) disease in Central and South America in the mid-2010s and recognition of the teratogenic effects of congenital exposure to ZIKV, there has been...

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.

Human Polyclonal Antibodies Prevent Lethal Zika Virus Infection in Mice

Zika virus (ZIKV) is an emerging mosquito-borne flavivirus that represents a major threat to global health. ZIKV infections in adults are generally asymptomatic or present with mild symptoms. However, recent outbreaks of ZIKV have revealed that it can cause Congenital Zika Syndrome in neonates and Guillain-Barré syndrome in adults. Currently, no ZIKV-specific vaccines or antiviral treatments are available. In this study, we tested the efficacy of convalescent plasma IgG hyperimmune product (ZIKV-IG) isolated from individuals with high neutralizing anti-ZIKV titers as a therapeutic candidate against ZIKV infection using a model of ZIKV infection in Ifnar1−/− mice. ZIKV-IG successfully protected mice from lethal ZIKV challenge. In particular, ZIKV-IG treatment at 24 hours after lethal ZIKV infection improved survival by reducing weight loss and tissue viral burden and improving clinical score. Additionally, ZIKV-IG eliminated ZIKV-induced tissue damage and inflammation in the brain and liver. These results indicate that ZIKV-IG is efficacious against ZIKV, suggesting this human polyclonal antibody is a viable candidate for further development as a treatment against human ZIKV infection.

Zika virus: persisting tissue reservoirs and their potential for clinically relevant pathology

The rapid spread of Zika virus through the Caribbean and Americas appears associated with greater levels of congenital zika and Guillain-Barre syndromes than previously seen. In addition, new disease pathologies such as persisting sexual transmission and severe liver injury have been identified. With zika vaccines years away from licensing an understanding of potential long-term health consequences following adult infection needs to be gained, especially where organs from infected people may be used for transplantation. To model the pathology of human Zika virus infection Old World and New World non-human primates were sub-cutaneously infected with a Caribbean Zika virus isolate. Following termination during primary viremia or later time points post peripheral viral clearance FFPE tissue sections were analysed for Zika virus RNA (RNAscope) and host responses (immunohistochemistry). Zika virus RNA was detected in multiple tissues from 3dpc with low levels of viral RNA detectable by RNAscope through to 101 dpc. New World non-human primates retained higher levels of persisting virus within tissues, notably within spleen, small intestine, kidney, liver and genital tissues. Differing pathologies were observed with Zika virus detected clustered within kidney glomeruli and associated with liver inflammatory infiltrates within New World species. Such pathologies are being documented in adults with resolved primary infection symptoms. This includes clinical complications following solid organ transplantation where immune suppression may allow viral reactivation either from the patient or transplanted organ. In the absence of a protective vaccine the potential risks from persisting viral reservoirs needs to be understood to ensure appropriate clinical management.

Zika virus: out of sight but not out of the mind. Viral persistence and host responses within the central and peripheral nervous systems

Following the rapid spread of Zika virus infection through the Caribbean and Americas, model systems of Zika virus infection have been established to determine disease pathology and potential health impacts for those infected with this neurotropic flavivirus. NIBSC has established both Old World (rhesus and cynomolgus macaques) and New World (red-bellied tamarins) non-human primate disease models of human Zika virus infection. Animals were infected sub-cutaneously with the Caribbean Zika isolate PRVABC59 and pairs terminated during primary viremia (3 dpc) or post clearance of plasma viremia (42 and 101 dpc). FFPE sections from multiple tissues, including brain and peripheral nerves were analysed for Zika virus RNA (RNAscope), viral proteins and host responses (immunohistochemistry). All animals became infected and rapidly cleared high levels of peripheral viremia. Zika virus RNA was detected in multiple tissues from 3 dpc with low levels of viral RNA and viral NS1 protein remaining detectable through to 101 dpc. Viral RNA was associated with both glial and neuronal cells throughout the brain and schwann cell nuclei in peripheral nerves. Neuroinflammation (astrogliosis, microgliosis, peri-vascular cuffing) and increased levels of CD3+, CD8+ or CD45+ cells were present from 3 dpc through to 101 dpc. Disruption of MAP2 neuronal dendrite staining and peripheral nerve myelin basic protein staining was also observed. The continued detection of Zika virus within tissues 3 months post infection and in the absence of a detectable peripheral viremia raises questions regarding potential long term effects of this virus and associated inflammatory responses within the nervous systems.

Human Fetal Astrocytes Infected with Zika Virus Exhibit Delayed Apoptosis and Resistance to Interferon: Implications for Persistence.

Zika virus (ZIKV) infection and persistence during pregnancy can lead to microcephaly and other fetal neurological disorders collectively known as Congenital Zika Syndrome. The immunological and virological events that contribute to the establishment of persistent ZIKV infection in humans are unclear though. Here we show that human fetal astrocytes (HFAs), the most abundant cell type in the central nervous system, become persistently infected with ZIKV resulting in continuous viral shedding for at least one month; a process that is facilitated by TIM/TAM receptors. HFAs are relatively resistant to ZIKV-induced apoptosis, a factor that may be important for chronic infection of these cells. Once infection was established, interferon treatment did not reduce virus replication. Moreover, the fact that the innate immune system was highly activated in persistently infected HFAs indicates that the virus can thrive in the presence of a sustained antiviral response. RNAseq analyses of persistently infected cells revealed that ZIKV alters host gene expression in a manner that could affect developmental processes. Conversely, data from sequencing of ZIKV genomes in persistently infected HFAs suggest that adaptive mutations were not required for establishing chronic infection. Based on these results, we postulate that HFAs are reservoirs for ZIKV in the fetal brain and that moderate apoptosis combined with inefficient antiviral response from these cells may contribute to the establishment of chronic brain infection associated with the ZIKV neurodevelopmental abnormalities.

Insights into ZIKV-Mediated Innate Immune Responses in Human Dermal Fibroblasts and Epidermal Keratinocytes

Zika virus (ZIKV) has emerged as a global pathogen causing significant public health concern. ZIKV infections in humans principally occur via mosquito bites. Thus, host skin cells are permissive to ZIKV infection and are the first line of defense against the virus. Here, we examined the role and mechanisms of antiviral skin immunity against ZIKV infection. ZIKV infection (African lineage MR766) in human dermal fibroblasts, human epidermal keratinocytes, and HaCaT keratinocytes resulted in distinct expression changes in RIG-I-like receptors, such as RIG-I and MDA5. Inhibition of RIG-I using small interfering RNA resulted in increased viral gene expression and reduced induction of IFNs and IFN-stimulated genes. Furthermore, ZIKV NS1 directly interacted with RIG-I or MDA5 and down-regulated RIG-I-like receptor-mediated antiviral signaling pathways. Asian lineage ZIKV (PRVABC59) infection also showed a distinct pattern of antiviral immunity in human skin cells, compared with other ZIKV strains. Additionally, ZIKV infections in human neural progenitor cells induced the robust activation of RIG-I-like receptor-mediated signaling, followed by highly enhanced IFN-stimulated gene expression. Our findings provide important insights into ZIKV tropism and subsequent antiviral signaling pathways that regulate ZIKV replication in human dermal fibroblasts and human epidermal keratinocytes.