The clinical spectrum and immunopathological mechanisms underlying ZIKV-induced neurological manifestations

Mechanistic insights into bone remodelling dysregulation by human viral pathogens

Bone-related diseases (osteopathologies) associated with human virus infections have increased around the globe. Recent findings have highlighted the intricate interplay between viral infection, the host immune system and the bone remodelling process. Viral infections can disrupt bone homeostasis, contributing to conditions such as arthritis and soft tissue calcifications. Osteopathologies can occur after arbovirus infections such as chikungunya virus, dengue virus and Zika virus, as well as respiratory viruses, such as severe acute respiratory syndrome coronavirus 2 and enteroviruses such as Coxsackievirus B. Here we explore how human viruses dysregulate bone homeostasis, detailing viral factors, molecular mechanisms, host immune response changes and bone remodelling that ultimately result in osteopathologies. We highlight model systems and technologies to advance mechanistic understanding of viral-mediated bone alterations. Finally, we propose potential prophylactic and therapeutic strategies, introduce 'osteovirology' as a research field highlighting the underestimated roles of viruses in bone-related diseases, and discuss research avenues for further investigation.

Hsa_circ_0007321 regulates Zika virus replication through miR-492/NFKBID/NF-κB signaling pathway

IMPORTANCE

Over the past decade, increasing evidence has shown that circular RNAs (circRNAs) play important regulatory roles in viral infection and host antiviral responses. However, reports on the role of circRNAs in Zika virus (ZIKV) infection are limited. In this study, we identified 45 differentially expressed circRNAs in ZIKV-infected A549 cells by RNA sequencing. We clarified that a downregulated circRNA, hsa_circ_0007321, regulates ZIKV replication through targeting of miR-492 and the downstream gene NFKBID. NFKBID is a negative regulator of nuclear factor-κB (NF-κB), and we found that inhibition of the NF-κB pathway promotes ZIKV replication. Therefore, this finding that hsa_circ_0007321 exerts its regulatory role on ZIKV replication through the miR-492/NFKBID/NF-κB signaling pathway has implications for the development of strategies to suppress ZIKV and possibly other viral infections.

Peripheral nervous system is injured by neutrophil extracellular traps (NETs) elicited by nonstructural (NS) protein-1 from Zika virus

The involvement of innate immune mediators to the Zika virus (ZIKV)-induced neuroinflammation is not yet well known. Here, we investigated whether neutrophil extracellular traps (NETs), which are scaffolds of DNA associated with proteins, have the potential to injure peripheral nervous. The tissue lesions were evaluated after adding NETs to dorsal root ganglia (DRG) explants and to DRG constituent cells or injecting them into mouse sciatic nerves. Identification of NET harmful components was achieved by pharmacological inhibition of NET constituents. We found that ZIKV inoculation into sciatic nerves recruited neutrophils and elicited the production of the cytokines CXCL1 and IL-1β, classical NET inducers, but did not trigger NET formation. ZIKV blocked PMA- and CXCL8-induced NET release, but, in contrast, the ZIKV nonstructural protein (NS)-1 induced NET formation. NET-enriched supernatants were toxic to DRG explants, decreasing neurite area, length, and arborization. NETs were toxic to DRG constituent cells and affected myelinating cells. Myeloperoxidase (MPO) and histones were identified as the harmful component of NETs. NS1 injection into mouse sciatic nerves recruited neutrophils and triggered NET release and caspase-3 activation, events that were also elicited by the injection of purified MPO. In summary, we found that ZIKV NS1 protein induces NET formation, which causes nervous tissue damages. Our findings reveal new mechanisms leading to neuroinflammation by ZIKV.

Low CCL2 and CXCL8 Production and High Prevalence of Allergies in Children with Microcephaly Due to Congenital Zika Syndrome

Congenital Zika Syndrome (CZS) is associated with an increased risk of microcephaly in affected children. This study investigated the peripheral dysregulation of immune mediators in children with microcephaly due to CZS. Gene expression quantified by qPCR in whole blood samples showed an increase in IFNγ and IL-13 transcripts in children affected with microcephaly compared to the control group. The microcephaly group exhibited significantly decreased CCL2 and CXCL8 levels in serum, quantified by CBA assay. An allergic profile questionnaire revealed a high prevalence of allergies in the microcephaly group. In accordance, elevated serum IgE level measured by the Proquantum Immunoassay was observed in children affected with microcephaly compared to the control group. Altogether, these findings show a persistent systemic inflammation in children with microcephaly due to CZS and suggest a possible impairment in leukocyte migration caused by low production of CCL2 and CXCL8, in addition to high levels of IgE associated with high prevalence of allergies. The dysregulation of inflammatory genes and chemokines underscores the importance of understanding the immunological characteristics of CZS. Further investigation into the long-term consequences of systemic inflammation in these children is crucial for developing appropriate therapeutic strategies and tailored vaccination protocols.

The Aedes aegypti RNA interference response against Zika virus in the context of co-infection with dengue and chikungunya viruses

Since its detection in 2015 in Brazil, Zika virus (ZIKV) has remained in the spotlight of international public health and research as an emerging arboviral pathogen. In addition to single infection, ZIKV may occur in co-infection with dengue (DENV) and chikungunya (CHIKV) viruses, with whom ZIKV shares geographic distribution and the mosquito Aedes aegypti as a vector. The main mosquito immune response against arboviruses is RNA interference (RNAi). It is unknown whether or not the dynamics of the RNAi response differ between single arboviral infections and co-infections. In this study, we investigated the interaction of ZIKV and DENV, as well as ZIKV and CHIKV co-infections with the RNAi response in Ae. aegypti. Using small RNA sequencing, we found that the efficiency of small RNA production against ZIKV -a hallmark of antiviral RNAi-was mostly similar when comparing single and co-infections with either DENV or CHIKV. Silencing of key antiviral RNAi proteins, showed no change in effect on ZIKV replication when the cell is co-infected with ZIKV and DENV or CHIKV. Interestingly, we observed a negative effect on ZIKV replication during CHIKV co-infection in the context of Ago2-knockout cells, though his effect was absent during DENV co-infection. Overall, this study provides evidence that ZIKV single or co-infections with CHIKV or DENV are equally controlled by RNAi responses. Thus, Ae. aegypti mosquitoes and derived cells support co-infections of ZIKV with either CHIKV or DENV to a similar level than single infections, as long as the RNAi response is functional.

Immunopathogenesis of viral infections in neurological autoimmune disease

Autoimmune diseases develop due to self-tolerance failure in recognizing self and non-self-antigens. Several factors play a role in inducing autoimmunity, including genetic and environmental elements. Several studies demonstrated the causative role of viruses; however, some studies showed the preventive effect of viruses in the development of autoimmunity. Neurological autoimmune diseases are classified based on the targets of autoantibodies, which target intracellular or extracellular antigens rather than neurons. Several theories have been hypothesized to explain the role of viruses in the pathogenesis of neuroinflammation and autoimmune diseases. This study reviewed the current data on the immunopathogenesis of viruses in autoimmunity of the nervous system.

Zika virus induced microcephaly and aberrant hematopoietic cell differentiation modeled in novel neonatal humanized mice

Introduction

Immunocompetent and immunocompromised murine models have been instrumental in answering important questions regarding ZIKV pathogenesis and vertical transmission. However, mimicking human congenital zika syndrome (CZS) characteristics in these murine models has been less than optimal and does not address the potential viral effects on the human immune system.

Methods

Here, we utilized neonatal humanized Rag2-/-γc-/- mice to model CZS and evaluate the potential viral effects on the differentiation of human hematopoietic stem cells in vivo. Newborn Rag2-/-γc-/- mice were engrafted with ZIKV-infected hematopoietic stem cells (HSC) and monitored for symptoms and lesions.

Results

Within 13 days, mice displayed outward clinical symptoms that encompassed stunted growth, hunched posture, ruffled fur, and ocular defects. Striking gross pathologies in the brain and visceral organs were noted. Our results also confirmed that ZIKV actively infected human CD34+ hematopoietic stem cells and restricted the development of terminally differentiated B cells. Histologically, there was multifocal mineralization in several different regions of the brain together with ZIKV antigen co-localization. Diffuse necrosis of pyramidal neurons was seen with collapse of the hippocampal formation.

Discussion

Overall, this model recapitulated ZIKV microcephaly and CZS together with viral adverse effects on the human immune cell ontogeny thus providing a unique in vivo model to assess the efficacy of novel therapeutics and immune interventions.

The Innate Defense in the Zika-Infected Placenta

Zika virus (ZIKV) is an arthropod-borne virus that belongs to the Flaviviridae family, genus Flavivirus and was first isolated 1947 in Uganda, Africa, from the serum of a sentinel Rhesus monkey. Since its discovery, the virus was responsible for major outbreaks in several different countries, being linked to severe complications in pregnant women, neonatal birth defects and the congenital zika syndrome. Maternal-fetal transmission of ZIKV can occur in all trimesters of pregnancy, and the role of the placenta and its cells in these cases is yet to be fully understood. The decidua basalis and chorionic villi, maternal-fetal components of the placenta, contain a rich immunological infiltrate composed by Hofbauer cells, mastocytes, dendritic cells and macrophages, primary cells of the innate immune response that have a role that still needs to be better investigated in ZIKV infection. Recent studies have already described several histopathological features and the susceptibility and permissiveness of placenta cells to infection by the Zika virus. In this review, we address some of the current knowledge on the innate immune responses against ZIKV, especially in the placenta.

MiR-103a-3p Promotes Zika Virus Replication by Targeting OTU Deubiquitinase 4 to Activate p38 Mitogen-Activated Protein Kinase Signaling Pathway

Background

MicroRNAs (miRNAs) play critical roles in regulating virus infection and replication. However, the mechanism by which miRNA regulates Zika virus (ZIKV) replication remains elusive. We aim to explore how the differentially expressed miR-103a-3p regulates ZIKV replication and to clarify the underlying molecular mechanism.

Methods

Small RNA sequencing (RNA-Seq) was performed to identify differentially expressed miRNAs in A549 cells with or without ZIKV infection and some of the dysregulated miRNAs were validated by quantitative real time PCR (qRT-PCR). The effect of miR-103a-3p on ZIKV replication was examined by transfecting miR-103a-3p mimic or negative control (NC) into A549 cells with or without p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 and expression levels of ZIKV NS5 mRNA and NS1 protein were detected by qRT-PCR and Western blot, respectively. The potential target genes for miR-103a-3p were predicted by four algorithms and further validated by mutation analysis through luciferase reporter assay. The predicated target gene OTU deubiquitinase (DUB) 4 (OTUD4) was over-expressed by plasmid transfection or silenced by siRNA transfection into cells prior to ZIKV infection. Activation status of p38 MAPK signaling pathway was revealed by looking at the phosphorylation levels of p38 (p-p38) and HSP27 (p-HSP27) by Western blot.

Results

Thirty-five differentially expressed miRNAs in ZIKV-infected A549 cells were identified by RNA-Seq analysis. Five upregulated and five downregulated miRNAs were further validated by qRT-PCR. One of the validated upregulated miRNAs, miR-103a-3p significantly stimulated ZIKV replication both at mRNA (NS5) and protein (NS1) levels. We found p38 MAPK signaling was activated following ZIKV infection, as demonstrated by the increased expression of the phosphorylation of p38 MAPK and HSP27. Blocking p38 MAPK signaling pathway using SB203580 inhibited ZIKV replication and attenuated the stimulating effect of miR-103a-3p on ZIKV replication. We further identified OTUD4 as a direct target gene of miR-103a-3p. MiR-103a-3p over-expression or OTUD4 silencing activated p38 MAPK signaling and enhanced ZIKV replication. In contrast, OTUD4 over-expression inhibited p38 MAPK activation and decreased ZIKV replication. In addition, OTUD4 over-expression attenuated the stimulating effect of miR-103a-3p on ZIKV replication and activation of p38 MAPK signaling.

Conclusion

Zika virus infection induced the expression of miR-103a-3p, which subsequently activated p38 MAPK signaling pathway by targeting OTUD4 to facilitate ZIKV replication.