Zika Virus Enters Soma of Neuron through NGF/TrkA-Like Endosomal Signaling Pathway

Infection with the Zika virus results in severe neurological disease in adults or congenital Zika syndrome in newborns. We employed the domain search strategy to study the Zika virus glycoprotein E in this work. The results revealed that immature E contains a NGF domain (“MNKCYIQIMDLGHMCDATMSYECPMLDEGVEPDDVDCWCNTTSTWVVYGTCHH”) and is capable of interacting with TrkA. The E/TrkA complex increased E's interaction with receptors such as Axl and facilitated Zika virus endocytosis via clathrin. Rab5 retrograded transmission of Zika virus-containing E/TrkA endosomal signals to neuronal soma. Rab7 helped dissociation of E/TrkA in late acidic endosomes, and then E became mature after the NGF domain was cut. After membrane fusion with the endosome, the Zika virus was released into the neuron cell body. It showed only the immature E protein of Zika had NGF activity. The retrograde trafficking of endosomal signals (E/TrkA) similar to NGF/TrkA enabled Zika virus to infect neuronal cells. E's interference with the TrkA signal impaired neuronal cell growth and results in neuronal cell apoptosis.

Flavivirus replication kinetics in early-term placental cell lines with different differentiation pathways

Background The uncontrollable spread of Zika virus (ZIKV) in the Americas during 2015–2017, and its causal link to microcephaly in newborns and Guillain-Barré syndrome in adults, led the World Health Organisation to declare it a global public health emergency. One of the most notable features of ZIKV pathogenesis was the ability of the virus to pass the placental barrier to infect the growing foetus. This pathogenic trait had not been observed previously for medically important flaviviruses, including dengue and yellow fever viruses. Methods In this study we evaluated the replication kinetics of ZIKV and the related encephalitic flavivirus West Nile strain Kunjin virus (WNVKUN) in early-term placental cell lines. Results We have observed that WNVKUN in fact replicates with a greater rate and to higher titres that ZIKV in these cell lines. Conclusions These results would indicate the potential for all flaviviruses to replicate in placental tissue but it is the ability to cross the placenta itself that is the restrictive factor in the clinical progression and presentation of congenital Zika syndrome.

Differential Type 1 IFN Gene Expression in CD14+ Placenta Cells Elicited by Zika Virus Infection During Pregnancy

Zika virus (ZIKV) is an arthropod-borne Flavivirus that can also be transmitted vertically from infected mother to fetus. Infection of the fetus during pregnancy can lead to congenital malformations and severely impact fetal brain development causing a myriad of diseases now labeled Congenital Zika Syndrome (CZS). The mechanisms by which ZIKV crosses the placenta into the fetal circulation and the extent of ZIKV-induced changes remain unclear. We have previously shown that ZIKV infection of pregnant rhesus macaques results in abnormal oxygen transport across the placenta which may promote uterine vasculitis and placental villous damage. Changes in immune cell frequencies and activation status were also detected, as were distinct changes in the proportions of CD14+ cell subsets with an altered ratio of classical to non-classical CD14+ monocyte cells in both the maternal decidua and placental villous from ZIKV-infected animals compare to uninfected controls. In the current study, we performed single cell RNA sequencing on CD14+ cells isolated from the decidua of animals that were ZIKV infected at 31, 51, or 115 days of gestation (where term is ~168 days) compared to pregnant, time-matched uninfected controls. Bioinformatic analysis identified unique transcriptional phenotypes between CD14+ cells of infected and uninfected animals suggesting a distinct and sustained difference in transcriptomes between infected and uninfected CD14+ cells derived from the decidua. The timing of ZIKV infection had no effect on the CD14+ cell transcriptional profiles. Interestingly, ZIKV infection caused changes in expression of genes in pathways related to cellular stress and metabolism as well as immune response activation. Type 1 interferon response genes (ISGs) were among those that were differentially expressed following infection and these included members of the ISG12 family, IFI27 and IFI6. These ISGs have been recently described as effectors of the IFN response to flaviviruses. Supplementing our animal findings, in CD14+ cells isolated from human placenta, ZIKV infection similarly induced the expression of IFI27 and IFI6. Overall, our results showed that ZIKV infection during pregnancy induces the stable expression of antiviral genes within CD14+ cells of the placenta, which may provide an immune shield to protect the placenta from further infection and damage.

Congenital Zika Syndrome Is Associated With Interferon Alfa Receptor 1

Host factors that influence Congenital Zika Syndrome (CZS) outcome remain elusive. Interferons have been reported as the main antiviral factor in Zika and other flavivirus infections. Here, we accessed samples from 153 pregnant women (77 without and 76 with CZS) and 143 newborns (77 without and 66 with CZS) exposed to ZIKV conducted a case-control study to verify whether interferon alfa receptor 1 (IFNAR1) and interferon lambda 2 and 4 (IFNL2/4) single nucleotide polymorphisms (SNPs) contribute to CZS outcome, and characterized placenta gene expression profile at term. Newborns carrying CG/CC genotypes of rs2257167 in IFNAR1 presented higher risk of developing CZS (OR=3.41; IC=1.35-8.60; Pcorrected=0.032). No association between IFNL SNPs and CZS was observed. Placenta from CZS cases displayed lower levels of IFNL2 and ISG15 along with higher IFIT5. The rs2257167 CG/CC placentas also demonstrated high levels of IFIT5 and inflammation-related genes. We found CZS to be related with exacerbated type I IFN and insufficient type III IFN in placenta at term, forming an unbalanced response modulated by the IFNAR1 rs2257167 genotype. Despite of the low sample size se findings shed light on the host-pathogen interaction focusing on the genetically regulated type I/type III IFN axis that could lead to better management of Zika and other TORCH (Toxoplasma, Others, Rubella, Cytomegalovirus, Herpes) congenital infections.

Zika virus infection during development impairs the formation of corpus callosum by disturbing axon guidance and growth of callosal neurons.

Congenital Zika Syndrome (CZS) is a set of birth defects caused by Zika virus (ZIKV) infection during pregnancy. Microcephaly is its main feature, but other brain abnormalities are found in CZS patients, such as ventriculomegaly, brain calcifications, and dysgenesis of the corpus callosum. Many studies have focused on microcephaly, but it remains unknown how ZIKV infection leads to callosal malformation. To tackle this issue, we infected mouse embryos in utero with Brazilian ZIKV and found that they are born with a reduction in callosal area and density of callosal neurons. ZIKV infection also causes a density reduction of PH3+ cells, intermediate progenitor cells and SATB2+ neurons. Moreover, axonal tracing revealed that callosal axons are reduced and misrouted. Also, ZIKV infected cultures show a reduction of callosal axon length. GFAP labelling showed that in utero infection compromises glial cells responsible for midline axon guidance. The RNA-Seq data from infected brains identified downregulation of axon guidance and axonogenesis related genes. In sum, we showed that ZIKV infection impairs critical steps of corpus callosum formation by disrupting not only neurogenesis but also axon guidance and growth across the midline.

Association between Maternal Non-Coding Interferon-λ Polymorphisms and Congenital Zika Syndrome in a Cohort from Brazilian Northeast

Congenital Zika syndrome (CZS) is characterized by a diverse group of congenital malformations induced by ZIKV infection during pregnancy. Type III interferons have been associated with placental immunity against ZIKV and restriction of vertical transmission in mice, and non-coding single-nucleotide polymorphisms (SNPs) on these genes are well known to influence susceptibility to other viral infections. However, their effect on ZIKV pathogenesis has not yet been explored. To investigate whether maternal non-coding SNPs at IFNL genes are associated with CZS, 52 women infected with ZIKV during pregnancy were enrolled in a case–control association study. A total of 28 women were classified as cases and 24 as controls based on the presence or absence of CZS in their infants, and seven Interferon-λ non-coding SNPs (rs12980275, rs8099917, rs4803217, rs4803219, rs8119886, rs368234815, rs12979860) were genotyped. The results of logistic regression analyses show an association between the G allele at rs8099917 and increased susceptibility to CZS under a log-additive model (adjustedOR = 2.80; 95%CI = 1.14–6.91; p = 0.02), after adjustment for trimester of infection and genetic ancestry. These results provide evidence of an association between Interferon-λ SNPs and CZS, suggesting rs8099917 as a promising candidate for further studies on larger cohorts.

Prevalence of microcephaly: the Latin American Network of Congenital Malformations 2010–2017

ObjectiveThe Latin American Network of Congenital Malformations: ReLAMC was established in 2017 to provide accurate congenital anomaly surveillance. This study used data from ReLAMC registries to quantify the prevalence of microcephaly from 2010 to 2017 (before, during and after the Zika virus epidemic).DesignNine ReLAMC congenital anomaly registries provided case-level data or aggregate data for any live births, still births or terminations of pregnancy with microcephaly. Births to pregnant women infected with Zika virus first occurred in Brazil in 2015, and in the remaining registry areas in 2016 with the exception of Chile that did not experience Zika virus. Therefore the prevalence of microcephaly for 2010–2014 and individual years 2015, 2016 and 2017 was estimated using multilevel random effect Poisson models. Clinical classification and characteristics of the cases were compared pre and post Zika for all centres providing individual case-level data.ResultsThe prevalence of microcephaly for all registries excluding Brazil was 2.3 per 10 000 (95% CI 2.0 to 2.6) for 2010–2014 rising to 5.4 (95% CI 4.8 to 6.0) in 2016 and 5.9 (95% CI 5.3 to 6.6) in 2017. Brazil had a prevalence of 0.6 per 10 000 (95% CI 0.5 to 0.6) in 2010–2014, rising to 5.8 (95% CI 5.6 to 6.1) in 2015, 8.0 (95% CI 7.6 to 8.3) in 2016 and then falling in 2017. Only 29 out of 687 cases of microcephaly were reported as congenital Zika syndrome in countries excluding Brazil.ConclusionsThe prevalence of microcephaly was influenced both by Zika causing congenital Zika syndrome and by increased reporting awareness.

Dual burden of Zika and COVID-19 in India: challenges, opportunities and recommendations

The COVID-19 pandemic has wreaked havoc in the world from last year, and any further insults like Zika virus will surely bring the apocalypse unto us. In July 2021, Zika began spreading in India, mainly in the state of Kerala. Zika infection resembles closely COVID-19 and other arboviral infections, which might lead to delayed and misdiagnosis, further leading to underreporting of cases. Some of the feared complications of Zika include Guillain–Barré syndrome and congenital Zika syndrome leading to microcephaly. Thus, Zika virus disease (ZVD) has significant public health and social impacts. Since the trifecta of infectious diseases (host, agent and environment) are all conducive to the spread of Zika in India, there is a huge risk that ZVD might become endemic in India, which is especially dangerous in the backdrop of this pandemic. This has to be stopped at all costs: the main aspects of which are public health measures, vector control and early diagnosis, especially in case of pregnant women. The diversion of healthcare resources for this pandemic has albeit made this difficult, but we must do our bit if we have to overcome this situation.