Jak Inhibitors Modulate Production of Replication-Competent Zika Virus in Human Hofbauer, Trophoblasts, and Neuroblastoma cells

Interferon alpha and beta receptor 1 knockout in human embryonic kidney 293 cells enhances the production efficiency of proteins or adenoviral vectors related to type I interferons

Human embryonic kidney (HEK) 293 cells are widely used in protein and viral vector production owing to their high transfection efficiency, rapid growth, and suspension growth capability. Given their antiviral, anticancer, and immune-enhancing effects, type I interferons (IFNs) have been used to prevent and treat human and animal diseases. However, the binding of type I IFNs to the IFN-α and-β receptor (IFNAR) stimulates the expression of IFN-stimulated genes (ISGs). This phenomenon induces an antiviral state and promotes apoptosis in cells, thereby impeding protein or viral vector production. In this study, we generated an IFNAR subtype 1 knockout (KO) HEK 293 suspension (IFNAR-KO) cell line by using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) technology. Upon treatment with human IFN-α, the IFNAR-KO cells showed a constant expression of ISGs, including 2'-5'-oligoadenylate synthetase 1 (OAS1), myxovirus resistance 1 (Mx1), protein kinase RNA-activated (PKR), and IFN-induced transmembrane protein 1 (IFITM1), when compared with the wild-type HEK 293 (WT) cells, wherein the ISGs were significantly upregulated. As a result, the titer of recombinant adenovirus expressing porcine IFN-α was significantly higher in the IFNAR-KO cells than in the WT cells. Furthermore, the IFNAR-KO cells continuously produced higher amounts of IFN-α protein than the WT cells. Thus, the CRISPR-Cas9-mediated IFNAR1 KO cell line can improve the production efficiency of proteins or viral vectors related to IFNs. The novel cell line may be used for producing vaccines and elucidating the type I IFN signaling pathway in cells.

Anti-inflammatory compounds reduce equine herpesvirus type 1 replication and cell-to-cell spread

Equine herpesvirus type 1 (EHV-1) is a highly transmissible pathogen that leads to a variety of clinical disease outcomes in infected horses. A major sequela that can occur after an EHV-1 infection is a neurological disease termed equine herpesvirus myeloencephalopathy (EHM). Clinical manifestations of EHM include fever, ataxia, incontinence, and partial to full paralysis, which may ultimately lead to the euthanization of the infected horse. To develop an effective treatment strategy for EHM, it is critical that the specific virus-host interactions that lead to EHM be investigated so that safe and effective therapeutic interventions can be developed and delivered. In this study, we examined the ability of four non-steroidal anti-inflammatory drugs (NSAIDs), a steroidal anti-inflammatory drug (dexamethasone), a Rho-kinase (ROCK) inhibitor, and a JAK/STAT inhibitor (AG490) to reduce EHV-1 virus yields and cell-to-cell spread. We show that the NSAID, flunixin meglumine (FM), and the JAK/STAT inhibitor, AG490, significantly reduced virus yields in endothelial and epithelial cell lines, and this inhibition was similar for two neurologic and two non-neurologic EHV-1 strains. In addition to reducing virus yields, AG490 and FM also significantly reduced the ability of EHV-1 to spread laterally from cell to cell.

Immune Recognition versus Immune Evasion Systems in Zika Virus Infection

The reemergence of the Zika virus (ZIKV) infection in recent years has posed a serious threat to global health. Despite being asymptomatic or mildly symptomatic in a majority of infected individuals, ZIKV infection can result in severe manifestations including neurological complications in adults and congenital abnormalities in newborns. In a human host, ZIKV is primarily recognized by RIG-like receptors and Toll-like receptors that elicit anti-viral immunity through the secretion of type I interferon (IFN) to limit viral survival, replication, and pathogenesis. Intriguingly, ZIKV evades its host immune system through various immune evasion strategies, including suppressing the innate immune receptors and signaling pathways, mutation of viral structural and non-structural proteins, RNA modulation, or alteration of cellular pathways. Here, we present an overview of ZIKV recognition by the host immune system and the evasion strategies employed by ZIKV. Characterization of the host-viral interaction and viral disease mechanism provide a platform for the rational design of novel prophylactic and therapeutic strategies against ZIKV infection.

Type I interferon receptor (IFNAR2) deficiency reveals Zika virus cytopathicity in human macrophages and microglia

Macrophages are key target cells of Zika virus (ZIKV) infection, implicated as a viral reservoir seeding sanctuary sites such as the central nervous system and testes. This rests on the apparent ability of macrophages to sustain ZIKV replication without experiencing cytopathic effects. ZIKV infection of macrophages triggers an innate immune response involving type I interferons (IFN-I), key antiviral cytokines that play a complex role in ZIKV pathogenesis in animal models. To investigate the functional role of the IFN-I response we generated human induced pluripotent stem cell (iPSC)-derived macrophages from a patient with complete deficiency of IFNAR2, the high affinity IFN-I receptor subunit. Accompanying the profound defect of IFN-I signalling in IFNAR2 deficient iPS-macrophages we observed significantly enhanced ZIKV replication and cell death, revealing the inherent cytopathicity of ZIKV towards macrophages. These observations were recapitulated by genetic and pharmacological ablation of IFN-I signalling in control iPS-macrophages and extended to a model of iPS-microglia. Thus, the capacity of macrophages to support noncytolytic ZIKV replication depends on an equilibrium set by IFN-I, suggesting that innate antiviral responses might counterintuitively promote ZIKV persistence via the maintenance of tissue viral reservoirs relevant to pathogenesis.

Placental Macrophage (Hofbauer Cell) Responses to Infection During Pregnancy: A Systematic Scoping Review

BACKGROUND

Congenital infection of the fetus via trans-placental passage of pathogens can result in severe morbidity and mortality. Even without transmission to the fetus, infection of the placenta itself is associated with pregnancy complications including pregnancy loss and preterm birth. Placental macrophages, also termed Hofbauer cells (HBCs), are fetal-origin macrophages residing in the placenta that are likely involved in responding to placental infection and protection of the developing fetus. As HBCs are the only immune cell present in the villous placenta, they represent one of the final opportunities for control of infection and prevention of passage to the developing fetus.

OBJECTIVE AND RATIONALE

The objective of this review was to provide a systematic overview of the literature regarding HBC responses during infection in pregnancy, including responses to viral, bacterial, and parasitic pathogens.

METHODS

PubMed and Scopus were searched on May 20th, 2021, with no limit on publication date, to identify all papers that have studied placental macrophages/Hofbauer cells in the context of infection. The following search strategy was utilized: (hofbauer* OR "hofbauer cells" OR "hofbauer cell" OR "placental macrophage" OR "placental macrophages") AND [infect* OR virus OR viral OR bacteri* OR parasite* OR pathogen* OR LPS OR "poly(i:c)" OR toxoplasm* OR microb* OR HIV)].

OUTCOMES

86 studies were identified for review. This included those that investigated HBCs in placentas from pregnancies complicated by maternal infection and in vitro studies investigating HBC responses to pathogens or Pathogen-Associated Molecular Patterns (PAMPs). HBCs can be infected by a variety of pathogens, and HBC hyperplasia was a common observation. HBCs respond to pathogen infection and PAMPs by altering their transcriptional, translational and secretion profiles. Co-culture investigations demonstrate that they can replicate and transmit pathogens to other cells. In other cases, they may eliminate the pathogen through a variety of mechanisms including phagocytosis, cytokine-mediated pathogen elimination, release of macrophage extracellular traps and HBC-antibody-mediated neutralization. HBC responses differ across gestation and may be influenced by pre-existing immunity. Clinical information, including gestational age at infection, gestational age of the samples, mode of sample collection and pregnancy outcome were missing for the majority of studies.

An overview of Zika virus genotypes and their infectivity

Zika virus (ZIKV) is an enveloped, single-stranded RNA arbovirus belonging to the genus Flavivirus. It was first isolated from a sentinel monkey in Uganda in 1947. More recently, ZIKV has undergone rapid geographic expansion and has been responsible for outbreaks in Southeast Asia, the Pacific Islands, and America. In this review, we have highlighted the influence of viral genetic variants on ZIKV pathogenesis. Two major ZIKV genotypes (African and Asian) have been identified. The Asian genotype is subdivided into Southwest Asia, Pacific Island, and American strains, and is responsible for most outbreaks. Non-synonymous mutations in ZIKV proteins C, prM, E, NS1, NS2A, NS2B, NS3, and NS4B were found to have a higher prevalence and association with virulent strains of the Asian genotype. Consequently, the Asian genotype appears to have acquired higher cellular permissiveness, tissue persistence, and viral tropism in human neural cells. Therefore, mutations in specific coding regions of the Asian genotype may enhance ZIKV infectivity. Considering that mutations in the genomes of emerging viruses may lead to new virulent variants in humans, there is a potential for the re-emergence of new ZIKV cases in the future.

Targeting Macrophage Dysregulation for Viral Infections: Novel Targets for Immunomodulators

A major barrier to human immunodeficiency virus (HIV-1) cure is the latent viral reservoir, which persists despite antiretroviral therapy (ART), including across the non-dividing myeloid reservoir which is found systemically in sanctuary sites across tissues and the central nervous system (CNS). Unlike activated CD4+ T cells that undergo rapid cell death during initial infection (due to rapid viral replication kinetics), viral replication kinetics are delayed in non-dividing myeloid cells, resulting in long-lived survival of infected macrophages and macrophage-like cells. Simultaneously, persistent inflammation in macrophages confers immune dysregulation that is a key driver of co-morbidities including cardiovascular disease (CVD) and neurological deficits in people living with HIV-1 (PLWH). Macrophage activation and dysregulation is also a key driver of disease progression across other viral infections including SARS-CoV-2, influenza, and chikungunya viruses, underscoring the interplay between macrophages and disease progression, pathogenesis, and comorbidity in the viral infection setting. This review discusses the role of macrophages in persistence and pathogenesis of HIV-1 and related comorbidities, SARS-CoV-2 and other viruses. A special focus is given to novel immunomodulatory targets for key events driving myeloid cell dysregulation and reservoir maintenance across a diverse array of viral infections.

Placental macrophages: Origin, heterogeneity, function and role in pregnancy-associated infections

Placental macrophages are a heterogenous population of immune cells present throughout pregnancy. They are essential for maintenance of the homeostatic placenta environment and host defense against infections. The characterization of placental macrophages as well as their activation have been limited for a long time by the lack of convenient tools. The emergence of unbiased methods makes it possible to reappraise the study of placental macrophages. In this review, we discuss the diversity and the functions of placental macrophages to better understand their dysfunctions during placental infections.

The potential of JAK/STAT pathway inhibition by ruxolitinib in the treatment of COVID-19

Ruxolitinib is the first approved JAK1 and JAK2 inhibitor, and is known to interfere with the JAK / STAT signaling pathway, one of the critical cellular signaling pathways involved in the inflammatory response. This review presents an overview of SARS-CoV-2 and the COVID-19 pandemic, and then focuses on the potential efficacy of ruxolitinib in this infection. The potential targets of ruxolitinib were determined by using genetic alterations that have been reported in COVID-19 patients. The potential effectiveness of ruxolitinib is suggested by evaluating the interactions of these potential targets with ruxolitinib or JAK/STAT pathway.

7-Deaza-7-fluoro-2'-C-methyladenosine inhibits Zika virus infection and viral-induced neuroinflammation

Zika virus (ZIKV) has gained a lot of attention in the past few years due to its rapid spread worldwide and its close association to severe neurological outcomes, such as microcephaly and Guillain-Barre syndrome. In this study, the in vitro and in vivo anti-ZIKV activity of 7-deaza-7-fluoro-2'-C-methyl-adenosine (DFMA) was evaluated. In vitro, using primary mouse neuronal cells and human neural stem cells infected by ZIKV, treatment with DFMA resulted in impaired viral replication and protection against virus-induced cell death. In vivo, when administrated prior to infection, DFMA prevented lethality and markedly reduced viral loads and neuroinflammation, including microgliosis and overall brain damage. Additionally, as an early therapeutic treatment, DFMA increased survival rates in mice. Collectively, these findings demonstrate that the nucleoside analog DFMA inhibits ZIKV infection and viral-induced neuroinflammation in vitro and in vivo without apparent untoward effects, suggesting it may be useful in individuals infected with ZIKV.

Norovirus Replication in Human Intestinal Epithelial Cells Is Restricted by the Interferon-Induced JAK/STAT Signaling Pathway and RNA Polymerase II-Mediated Transcriptional Responses

Human noroviruses (HuNoV) are a leading cause of viral gastroenteritis worldwide and a significant cause of morbidity and mortality in all age groups. The recent finding that HuNoV can be propagated in B cells and mucosa-derived intestinal epithelial organoids (IEOs) has transformed our ability to dissect the life cycle of noroviruses. Using transcriptome sequencing (RNA-Seq) of HuNoV-infected intestinal epithelial cells (IECs), we have found that replication of HuNoV in IECs results in interferon (IFN)-induced transcriptional responses and that HuNoV replication in IECs is sensitive to IFN. This contrasts with previous studies that suggested that the innate immune response may play no role in the restriction of HuNoV replication in immortalized cells. We demonstrated that inhibition of Janus kinase 1 (JAK1)/JAK2 enhanced HuNoV replication in IECs. Surprisingly, targeted inhibition of cellular RNA polymerase II-mediated transcription was not detrimental to HuNoV replication but instead enhanced replication to a greater degree than blocking of JAK signaling directly. Furthermore, we demonstrated for the first time that IECs generated from genetically modified intestinal organoids, engineered to be deficient in the interferon response, were more permissive to HuNoV infection. Taking the results together, our work revealed that IFN-induced transcriptional responses restrict HuNoV replication in IECs and demonstrated that inhibition of these responses mediated by modifications of the culture conditions can greatly enhance the robustness of the norovirus culture system.IMPORTANCE Noroviruses are a major cause of gastroenteritis worldwide, and yet the challenges associated with their growth in culture have greatly hampered the development of therapeutic approaches and have limited our understanding of the cellular pathways that control infection. Here, we show that human intestinal epithelial cells, which represent the first point of entry of human noroviruses into the host, limit virus replication by induction of innate responses. Furthermore, we show that modulating the ability of intestinal epithelial cells to induce transcriptional responses to HuNoV infection can significantly enhance human norovirus replication in culture. Collectively, our findings provide new insights into the biological pathways that control norovirus infection but also identify mechanisms that enhance the robustness of norovirus culture.

Synthesis of 4'-Substituted-2'-Deoxy-2'-α-Fluoro Nucleoside Analogs as Potential Antiviral Agents

Nucleoside analogs are widely used for the treatment of viral diseases (Hepatitis B/C, herpes and human immunodeficiency virus, HIV) and various malignancies. ALS-8176, a prodrug of the 4'-chloromethyl-2'-deoxy-2'-fluoro nucleoside ALS-8112, was evaluated in hospitalized infants for the treatment of respiratory syncytial virus (RSV), but was abandoned for unclear reasons. Based on the structure of ALS-8112, a series of novel 4'-modified-2'-deoxy-2'-fluoro nucleosides were synthesized. Newly prepared compounds were evaluated against RSV, but also against a panel of RNA viruses, including Dengue, West Nile, Chikungunya, and Zika viruses. Unfortunately, none of the compounds showed marked antiviral activity against these viruses.

Pre- and peri-implantation Zika virus infection impairs fetal development by targeting trophectoderm cells

Zika virus (ZIKV) infection results in an increased risk of spontaneous abortion and poor intrauterine growth although the underlying mechanisms remain undetermined. Little is known about the impact of ZIKV infection during the earliest stages of pregnancy, at pre- and peri-implantation, because most current ZIKV pregnancy studies have focused on post-implantation stages. Here, we demonstrate that trophectoderm cells of pre-implantation human and mouse embryos can be infected with ZIKV, and propagate virus causing neural progenitor cell death. These findings are corroborated by the dose-dependent nature of ZIKV susceptibility of hESC-derived trophectoderm cells. Single blastocyst RNA-seq reveals key transcriptional changes upon ZIKV infection, including nervous system development, prior to commitment to the neural lineage. The pregnancy rate of mice is >50% lower in pre-implantation infection than infection at E4.5, demonstrating that pre-implantation ZIKV infection leads to miscarriage. Cumulatively, these data elucidate a previously unappreciated association of pre- and peri-implantation ZIKV infection and microcephaly.

Clinical Importance of Placental Testing among Suspected Cases of Congenital Zika Syndrome

Contemporaneous Zika virus (ZIKV) strains can cause congenital Zika syndrome (CZS). Current ZIKV clinical laboratory testing strategies are limited and include IgM serology (which may wane 12 weeks after initial exposure) and nucleic acid testing (NAT) of maternal serum, urine, and placenta for (+) strand ZIKV RNA (which is often transient). The objectives of this study were to determine if use of additional molecular tools, such as quantitative PCR and microscopy, would add to the diagnostic value of current standard placental ZIKV testing in cases with maternal endemic exposure and indeterminate testing. ZIKV RNA was quantified from dissected sections of placental villi, chorioamnion sections, and full cross-sections of umbilical cord in all cases examined. Quantitation with high-resolution automated electrophoresis determined relative amounts of precisely verified ZIKV (74-nt amplicons). In order to localize and visualize stable and actively replicating placental ZIKV in situ, labeling of flaviviridae glycoprotein, RNA ISH against both (+) and (⁻) ZIKV-specific ssRNA strands, and independent histologic examination for significant pathologic changes were employed. We demonstrate that the use of these molecular tools added to the diagnostic value of placental ZIKV testing among suspected cases of congenital Zika syndrome with poorly ascribed maternal endemic exposure.

Hofbauer Cells: Their Role in Healthy and Complicated Pregnancy

Hofbauer cells are placental villous macrophages of fetal origin that are present throughout pregnancy. Although Hofbauer cell populations are antigenically and morphologically heterogeneous, their epigenetic, antigenic, and functional profiles most closely resemble alternatively activated macrophages or what are referred to as M2a, M2b, M2c, and M2d polarity subtypes. Consistent with an M2-like profile, these cells play an important role in placental development including vasculogenesis and angiogenesis. During placental inflammation Hofbauer cells may produce pro-inflammatory cytokines or mediators that damage the villous cell barrier, and induce fibrotic responses within the villi as a continuum of chronic inflammation. However, to date, there is no evidence that Hofbauer cells become classically activated or adopt an M1 polarity phenotype that is able to kill microbes. To the contrary, their predominant M2 like qualities may be why these cells are ineffective in controlling most TORCH infections. Moreover, Hofbauer cells may contribute to vertical transmission of various pathogens to the fetus since they can harbor live virus and serve as reservoirs within the placenta. The goal of this review is to summarize what is currently known about the role of Hofbauer cells in normal and complicated pregnancies that involve immunologic disorders, inflammation, and/or infection.

An Update on Sexual Transmission of Zika Virus

Zika virus (ZIKV) is a single-stranded RNA virus belonging to the arthropod-borne flaviviruses (arboviruses) which are mainly transmitted by blood-sucking mosquitoes of the genus Aedes. ZIKV infection has been known to be rather asymptomatic or presented as febrile self-limited disease; however, during the last decade the manifestation of ZIKV infection has been associated with a variety of neuroimmunological disorders including Guillain–Barré syndrome, microcephaly and other central nervous system abnormalities. More recently, there is accumulating evidence about sexual transmission of ZIKV, a trait that has never been observed in any other mosquito-borne flavivirus before. This article reviews the latest information regarding the latter and emerging role of ZIKV, focusing on the consequences of ZIKV infection on the male reproductive system and the epidemiology of human-to-human sexual transmission.

Experimental Zika Virus Infection in the Pregnant Common Marmoset Induces Spontaneous Fetal Loss and Neurodevelopmental Abnormalities

During its most recent outbreak across the Americas, Zika virus (ZIKV) was surprisingly shown to cause fetal loss and congenital malformations in acutely and chronically infected pregnant women. However, understanding the underlying pathogenesis of ZIKV congenital disease has been hampered by a lack of relevant in vivo experimental models. Here we present a candidate New World monkey model of ZIKV infection in pregnant marmosets that faithfully recapitulates human disease. ZIKV inoculation at the human-equivalent of early gestation caused an asymptomatic seroconversion, induction of type I/II interferon-associated genes and proinflammatory cytokines, and persistent viremia and viruria. Spontaneous pregnancy loss was observed 16-18 days post-infection, with extensive active placental viral replication and fetal neurocellular disorganization similar to that seen in humans. These findings underscore the key role of the placenta as a conduit for fetal infection, and demonstrate the utility of marmosets as a highly relevant model for studying congenital ZIKV disease and pregnancy loss.

Zika in the Americas, year 2: What have we learned? What gaps remain? A report from the Global Virus Network

In response to the outbreak of Zika virus (ZIKV) infection in the Western Hemisphere and the recognition of a causal association with fetal malformations, the Global Virus Network (GVN) assembled an international taskforce of virologists to promote basic research, recommend public health measures and encourage the rapid development of vaccines, antiviral therapies and new diagnostic tests. In this article, taskforce members and other experts review what has been learned about ZIKV-induced disease in humans, its modes of transmission and the cause and nature of associated congenital manifestations. After describing the make-up of the taskforce, we summarize the emergence of ZIKV in the Americas, Africa and Asia, its spread by mosquitoes, and current control measures. We then review the spectrum of primary ZIKV-induced disease in adults and children, sites of persistent infection and sexual transmission, then examine what has been learned about maternal-fetal transmission and the congenital Zika syndrome, including knowledge obtained from studies in laboratory animals. Subsequent sections focus on vaccine development, antiviral therapeutics and new diagnostic tests. After reviewing current understanding of the mechanisms of emergence of Zika virus, we consider the likely future of the pandemic.