Review: Evidence of Neurological Sequelae in Children With Acquired Zika Virus Infection

Cohort study: Neurological and cognitive-behavioral sequelae of acquired Zika virus infection among Nicaraguan children

BACKGROUND

ZIKV has neuroinvasive properties, and in utero exposure can cause birth defects, but little is known about the neurological and neurocognitive impacts of acquired ZIKV infection, particularly in children.

METHODS

We assessed neurological symptoms frequency among ZIKV-infected children within one year after ZIKV infection. Three to 5 years post-infection, these children and a matched group of uninfected children were assessed via questionnaires, neurological exams, and neuropsychological testing to evaluate the association between prior ZIKV infection and subsequent neurological symptoms, and cognitive-behavioral function.

RESULTS

Among 194 ZIKV-infected children, 3 reported asthenia, 4 reported neck pain, and 10 reported back pain within one year post-infection. At follow-up, clinician-observed cranial nerve abnormalities were significantly more common among ZIKV-infected vs. uninfected children (16 vs. 3; p < 0.01), with vestibulocochlear nerve abnormalities observed most frequently. While ZIKV-infected children scored better than uninfected on cognitive measures, this difference was not clinically meaningful.

CONCLUSIONS

Neurological signs, including paresthesia and cranial nerve abnormalities, were observed among ZIKV-infected participants in our study. However, we did not observe a meaningful link between acquired ZIKV infection and subsequent neurological, cognitive, or behavioral outcomes in a representative sample. An exception may be hearing impairment and loss, which should be explored further in future studies.

IMPACT

Neurological symptoms, though rare, were observed and reported more frequently among ZIKV-infected vs. uninfected children. These included: asthenia, neck pain, back pain, paresthesia, and cranial nerve abnormalities. Neurocognitive and behavioral test scores were similar among ZIKV-infected and uninfected children. Our study suggests that ZIKV-infected children should be monitored for neurological symptoms and cranial neuropathy to better understand the full burden of acquired ZIKV infection among children.

Long-Term Growth and Neurodevelopmental Outcomes of Neonates Infected with SARS-CoV-2 during the COVID-19 Pandemic at 18-24 Months Corrected Age: A Prospective Observational Study

INTRODUCTION

During the early coronavirus disease (COVID-19) pandemic in 2020, researchers cautioned about the potential neuroinvasive capability of the virus and long-term neurological consequences. Although a few preliminary studies have found delayed communication, fine motor, and problem-solving skills in infants after COVID-19 infection, there continues to be a paucity of data on long-term development of neonates diagnosed with COVID-19.

METHODS

We conducted a prospective study of 20 neonates who acquired severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection during the first wave of the pandemic (April-July 2020). At 18-24 months corrected age, we assessed neurodevelopment by Bayley Scales of Infant and Toddler Development, the third edition (BSID-III), along with growth, hearing, and vision evaluation.

RESULTS

The mean corrected age at assessment was 21 months 11 days ± 1 month 28 days. We found developmental delay in nearly half of the children with scores below one standard deviation in either of the BSID-III domains. Mild delay in either motor, cognitive, or language domains was found in 9 (45%) children and moderate delay in 2 (10%). Expressive language, fine motor, and receptive language were predominantly affected. None of the children had hearing impairment, blindness, or significant growth faltering including clinically severe microcephaly. The mean composite cognitive, language, and motor scores were significantly lower in those with neurodevelopmental delay (p value - 0.02, 0.000, and 0.03, respectively) without any differences in their disease characteristics.

CONCLUSION

Neonates infected with SARS-CoV-2 have an increased risk of developmental delays in expressive language, fine motor, and receptive language skills at 18-24 months of age. The severity of delays is predominantly mild.

Zika virus screening during pregnancy: Results and lessons learned from a screening program and a post-delivery follow-up analysis (2016-2022)

OBJECTIVE

To evaluate a Zika virus screening program applied to asymptomatic exposed pregnant women.

METHODOLOGY

Analysis of data generated during the roll out of a Zika screening program. We included socio-demographic data, ultrasounds, and serological results (IgM, IgG, and Plaque Reduction Neutralization Test; PRNT) from asymptomatic pregnant women exposed to Zika virus enrolled in the screening program between 2016 to 2019.

RESULTS

We included 406 asymptomatic ZIKV-exposed pregnant women who gave 400 full-term new-borns. The median age was 30 years (IQR = 25-34), which was lower (29 years; IQR = 24-34) among women of non-EU migrant origin (76.4% of the sample). Migrant women tended to delay the first pre-natal consultation compared to EU origin women (p = .003). Overall, 83.2% (N = 328) of participants had ZIKV low risk serological profile (IgM-/IgG- or IgM-/IgG+ and PRNT-), 3.0% (N = 12) showed high risk of recent ZIKV infection (IgM+ or PRNT+) and 13.7% (N = 54) had indeterminate results. A fetal malformation was identified in 29 children (9.3%). Fetal malformation was associated with a ZIKV high risk serological profile [24 out of the 246 (1.6%) with low risk profile and 3 out of the 12 with at high risk profile (25.0%; p = .02)]. Four newborns with high risk profile had a positive ZIKV-PCR test, which included two cases with microcephaly. No association was observed between maternal exposure to ZIKV infection and developmental abnormalities during the post-natal period follow-up.

CONCLUSIONS

The ZIKV-screening program had considerable costs and yielded a high rate of indeterminate results among asymptomatic pregnant women. Considering the poor value for decision-making of the results, efforts should focus on providing early access to routine maternity care, especially to migrant women. A simpler screening protocol might consider an initial ZIKV-PCR or IgM determination and subsequent referral to a fetal medicine specialist in those women with a positive result and/or whom ultrasound examination has revealed fetal abnormalities (10% of total women in our study sample).

Neurotoxic properties of the Zika virus envelope protein

Prenatal Zika virus (ZIKV) infection is a serious global concern as it can lead to brain injury and many serious birth defects, collectively known as congenital Zika syndrome. Brain injury likely results from viral mediated toxicity in neural progenitor cells. Additionally, postnatal ZIKV infections have been linked to neurological complications, yet the mechanisms driving these manifestations are not well understood. Existing data suggest that the ZIKV envelope protein can persist in the central nervous system for extended periods of time, but it is unknown if this protein can independently contribute to neuronal toxicity. Here we find that the ZIKV envelope protein is neurotoxic, leading to overexpression of poly adenosine diphosphate -ribose polymerase 1, which can induce parthanatos. Together, these data suggest that neuronal toxicity resulting from the envelope protein may contribute to the pathogenesis of post-natal ZIKV-related neurologic complications.

NeuN distribution in brain structures of normal and Zika-infected suckling mice

Microcephaly is the more severe brain malformation because of Zika virus infection. Increased vulnerability of neural stem and progenitor cells to Zika infection during prenatal neurodevelopment impairs the complete formation of cortical layers. Normal development of cerebellum is also affected. However, the follow-up of apparently healthy children born to Zika exposed mothers during pregnancy has revealed other neurological sequelae. This suggests Zika infection susceptibility remains in nervous tissue after neurogenesis end, when differentiated neuronal populations predominate. The neuronal nuclear protein (NeuN) is an exclusive marker of postmitotic neurons. Changes in NeuN expression are associated with neuronal degeneration. We have evaluated immunohistochemical expression of NeuN protein in cerebral cortex, hippocampus, and cerebellum of normal and Zika-infected neonatal Balb/c mice. The highest NeuN immunoreactivity was found mainly in neurons of all cortical layers, pyramidal layer of hippocampus, granular layer of dentate gyrus and in internal granular layer of cerebellum. Viral infection caused marked loss of NeuN immunostaining in all these brain areas. This suggests neurodegenerative effects of Zika virus infection during postmitotic neuron maturation and contribute to interpretation of neuropathogenic mechanisms of Zika.

Acquired Hip Dysplasia in Children with Congenital Zika Virus Infection in the First Four Years of Life

Acquired hip dysplasia has been described in children with cerebral palsy (CP); periodic surveillance is recommended in this population to prevent hip displacement and dislocation. Children with congenital zika syndrome (CZS) may present a spectrum of neurological impairments with changes in tonus, posture, and movement similar to children with CP. However, the relationship between CZS and hip dysplasia has not been characterized. In this prospective cohort study, we aimed to describe the occurrence of hip dysplasia in patients with CZS. Sixty-four children with CZS from 6 to 48 months of age were included and followed at a tertiary referral center in Rio de Janeiro, Brazil, with periodic radiologic and clinical hip assessments. Twenty-six (41%) patients were diagnosed with hip dysplasia during follow-up; mean age at diagnosis was 23 months. According to the Gross Motor Function Classification System (GMFCS), 58 (91%) patients had severe impairment (GMFCS IV and V) at the first evaluation. All patients with progression to hip dysplasia had microcephaly and were classified as GMFCS IV or V. Pain and functional limitation were reported by 22 (84%) caregivers of children with hip dysplasia. All patients were referred to specialized orthopedic care; eight (31%) underwent surgical treatment during follow-up. Our findings highlight the importance of implementing a hip surveillance program and improving access to orthopedic treatment for children with CZS in order to decrease the chances of dysplasia-related complications and improve quality of life.

Molecular survey of Zika virus in the animal-human interface in traditional farming

Backyard animal husbandry is common in rural communities in developing countries and, given the conditions in which it occurs, it can increase the risk of disease transmission, such as arboviruses. To determine the presence of the Zika virus (ZIKV) and abundance of its arthropod vectors we evaluated the socioeconomic implications involved in its transmission in two highly vulnerable Mayan communities in the state of Yucatan that practice backyard farming. An analytical cross-sectional study was carried out throughout 2016 to understand socioeconomic variables and seasonal patterns in mosquito populations. We selected 20 households from each community. Social exclusion indicators were analyzed, human and domestic animals were sampled, and mosquitoes were collected and identified. Four out of eight indicators of social exclusion were higher than the reported national averages. We captured 5,825 mosquitoes from 16 species being Culex quinquefasciatus and Aedes aegypti the most abundant. The presence of chickens and human overcrowding in dwellings were the most significant factors (P = 0.026) associated with the presence of Ae. aegypti. Septic tanks (odds ratio = 6.64) and chickens (odds ratio = 27.41) in backyards were the main risk factors associated with the presence of immature states of Ae. aegypti in both communities. Molecular analysis to detect ZIKV was performed in blood samples from 416 humans, 1,068 backyard animals and 381 mosquito pools. Eighteen humans and 10 pig pools tested positive for ZIKV. Forty-three mosquito pools tested positive for flavivirus. Ten of the 43 pools of positive mosquitoes were sequenced, corresponding 3/10 to ZIKV and 1/10 to Dengue virus type 2. The findings obtained indicate the continuous circulation of Flavivirus (including ZIKV) in backyard environments in vulnerable communities, highlighting the importance of studying their transmission and maintenance in these systems, due that backyard animal husbandry is a common practice in these vulnerable communities with limited access to health services.

Neurological and neuropsychological sequelae of Zika virus infection in children in León, Nicaragua

Objectives.

To describe the presence and persistence of neurological and neuropsychological sequelae among children with acquired Zika virus infection and assess whether those sequelae were more common in children infected with Zika virus compared to uninfected children.

Methods.

We conducted a prospective cohort study of children with and without Zika virus infection in León, Nicaragua, using a standard clinical assessment tool and questionnaire to collect data on symptoms at three visits, about 6 months apart, and a battery of standardized instruments to evaluate neurocognitive function, behavior, depression, and anxiety at the last two visits.

Results.

Sixty-two children were enrolled, with no significant differences in demographics by infection group. Children infected with Zika virus had a range of neurological symptoms, some of which persisted for 6 to 12 months; however, no consistent pattern of symptoms was observed. At baseline a small percentage of children infected with Zika virus had an abnormal finger-to-nose test (13%), cold touch response (13%), and vibration response (15%) versus 0% in the uninfected group. Neurocognitive deficits and behavioral problems were common in both groups, with no significant differences between the groups. Children infected with Zika virus had lower cognitive efficiency scores at the 6-month visit. Anxiety and depression were infrequent in both groups.

Conclusions.

Larger studies are needed to definitively investigate the relationship between Zika virus infection and neurological symptoms and neurocognitive problems, with adjustment for factors affecting cognition and behavior, including mood and sleep disorders, home learning environment, history of neuroinvasive infections, and detailed family history of neuropsychological problems.

Bioprospection for new larvicides against Aedes aegypti based on ethnoknowledge from the Amazonian São Sebastião de Marinaú riverside community

ETHNOPHARMACOLOGICAL RELEVANCE

Vector-borne diseases represent a huge global burden impacting health systems. Aedes aegypti is the main vector of arboviral diseases including dengue, Zika, chikungunya and urban yellow fever in both tropical and subtropical areas. Ethnopharmacological investigations provide potential avenues for developing new vector control strategies.

AIM OF THE STUDY

The objective of this study is to document the São Sebastião de Marinaú riverside community's ethnoknowledge of local plants used to control mosquitoes and perform bioguided fractionation to isolate the compounds active against the arboviral disease vector Ae. aegypti.

MATERIALS AND METHODS

Semi-structured interviews were conducted with residents of the Marinaú community located in the Caxiuanã National Forest, in the Amazon biome, Pará, Brazil. The plants used to control mosquitoes were subjected to phytochemical studies guided by Ae. aegypti assays. Extracts were obtained from seven species using distinct organic solvents. Active extracts and fractions were separated by chromatographic techniques. Isolated compounds were characterized by NMR, LC/MS and GC/MS. Sample activity against Ae. aegypti larvae and pupae was evaluated after 24, 48 and 72 h exposure. The extracts were also investigated against adult female mosquitoes. The LC₅₀ values were determined by diluting each sample to obtain different concentrations in the respective activity range.

RESULTS

The Marinaú community uses more than ten plants as a repellent, most of which are trees native to the region. The primary applications of these plants to protect against insect bites were: burning plants (fumigation), application of body oils and bathing in macerated plants. Carapa guianensis is the predominant species used as a repellent. Extracts from Diospyros guianensis fruits, Carapa guianensis seed shells and Aspidosperma nitidum wood demonstrated Ae. aegypti larvicidal activity. The C. guianensis seed shell extract demonstrated a residual larvicidal effect. Plumbagin, stigmasterol, β-sitosterol, betulinic, ursolic and oleanolic acids, and betulin were identified in the D. guianensis extract. The plumbagin, ursolic and oleanolic acids displayed larvicidal activity. Oleanolic, ursolic and betulinic acids, and betulin were considered pupicidal. Aricine, the major alkaloid isolated from A. nitidum wood, also presented larvicidal activity.

CONCLUSIONS

Ten plant species traditionally used by the Marinaú community to afford protection against mosquitoes were reported. C. guianensis, D. guianensis and A. nitidum extracts were considered larvicidal against Ae. aegypti. Four triterpenes stood out as very active compounds against pupae. Aricine, an indole alkaloid, displayed larvicidal activity. Therefore, traditional knowledge of Amazonian plants combined with bioguided fractionation constitutes a strategy for the development of eco-friendly insecticides to control Ae. aegypti, an arbovirus vector.

Zika virus-like particle vaccine fusion loop mutation increases production yield but fails to protect AG129 mice against Zika virus challenge

Zika virus (ZIKV) is a mosquito-borne flavivirus with maternal infection associated with preterm birth, congenital malformations, and fetal death, and adult infection associated with Guillain-Barré syndrome. Recent widespread endemic transmission of ZIKV and the potential for future outbreaks necessitate the development of an effective vaccine. We developed a ZIKV vaccine candidate based on virus-like-particles (VLPs) generated following transfection of mammalian HEK293T cells using a plasmid encoding the pre-membrane/membrane (prM/M) and envelope (E) structural protein genes. VLPs were collected from cell culture supernatant and purified by column chromatography with yields of approximately 1-2mg/L. To promote increased particle yields, a single amino acid change of phenylalanine to alanine was made in the E fusion loop at position 108 (F108A) of the lead VLP vaccine candidate. This mutation resulted in a modest 2-fold increase in F108A VLP production with no detectable prM processing by furin to a mature particle, in contrast to the lead candidate (parent). To evaluate immunogenicity and efficacy, AG129 mice were immunized with a dose titration of either the immature F108A or lead VLP (each alum adjuvanted). The resulting VLP-specific binding antibody (Ab) levels were comparable. However, geometric mean neutralizing Ab (nAb) titers using a recombinant ZIKV reporter were significantly lower with F108A immunization compared to lead. After virus challenge, all lead VLP-immunized groups showed a significant 3- to 4-Log₁₀ reduction in mean ZIKV RNAemia levels compared with control mice immunized only with alum, but the RNAemia reduction of 0.5 Log₁₀ for F108A groups was statistically similar to the control. Successful viral control by the lead VLP candidate following challenge supports further vaccine development for this candidate. Notably, nAb titer levels in the lead, but not F108A, VLP-immunized mice inversely correlated with RNAemia. Further evaluation of sera by an in vitro Ab-dependent enhancement assay demonstrated that the F108A VLP-induced immune sera had a significantly higher capacity to promote ZIKV infection in FcγR-expressing cells. These data indicate that a single amino acid change in the fusion loop resulted in increased VLP yields but that the immature F108A particles were significantly diminished in their capacity to induce nAbs and provide protection against ZIKV challenge.

Zika virus (ZIKV) is transmitted by mosquitoes and is a serious health threat due to potential epidemic spread. Infection in adults may lead to Guillain-Barré syndrome, a neurological disorder, or may cause harm to a developing fetus resulting in preterm birth, fetal death, or devastating congenital malformations. There are currently no approved vaccines against ZIKV. We previously developed a lead candidate vaccine based on a virus-like particle (VLP) that was generated in tissue culture. This ZIKV shell is devoid of any viral genetic material. In previous studies, this lead VLP candidate generated neutralizing antibodies (nAbs) that recognized wild-type ZIKV and prevented viral replication in both mice and non-human primates. To increase production of the lead VLP candidate and decrease cost-of-goods, we introduced a single amino acid change, phenylalanine to alanine, in the envelope glycoprotein. This change resulted in a modest increase in VLP yield. However, this single amino acid change resulted in reduced induction of nAbs following immunization and no significant reduction of RNAemia following challenge compared to the lead candidate. The results of this study suggest this investigational vaccine candidate is not suitable for further vaccine development and that ZIKV VLP maturation may have an important role in protection.

Neurodevelopment in Children Exposed to Zika in utero: Clinical and Molecular Aspects

Five years after the identification of Zika virus as a human teratogen, we reviewed the early clinical manifestations, collectively called congenital Zika syndrome (CZS). Children with CZS have a very poor prognosis with extremely low performance in motor, cognitive, and language development domains, and practically all feature severe forms of cerebral palsy. However, these manifestations are the tip of the iceberg, with some children presenting milder forms of deficits. Additionally, neurodevelopment can be in the normal range in the majority of the non-microcephalic children born without brain or eye abnormalities. Vertical transmission and the resulting disruption in development of the brain are much less frequent when maternal infection occurs in the second half of the pregnancy. Experimental studies have alerted to the possibility of other behavioral outcomes both in prenatally infected children and in postnatal and adult infections. Cofactors play a vital role in the development of CZS and involve genetic, environmental, nutritional, and social determinants leading to the asymmetric distribution of cases. Some of these social variables also limit access to multidisciplinary professional treatment.

Systemic Response to Infection Induces Long-Term Cognitive Decline: Neuroinflammation and Oxidative Stress as Therapeutical Targets

In response to pathogens or damage signs, the immune system is activated in order to eliminate the noxious stimuli. The inflammatory response to infectious diseases induces systemic events, including cytokine storm phenomenon, vascular dysfunction, and coagulopathy, that can lead to multiple-organ dysfunction. The central nervous system (CNS) is one of the major organs affected, and symptoms such as sickness behavior (depression and fever, among others), or even delirium, can be observed due to activation of endothelial and glial cells, leading to neuroinflammation. Several reports have been shown that, due to CNS alterations caused by neuroinflammation, some sequels can be developed in special cognitive decline. There is still no any treatment to avoid cognitive impairment, especially those developed due to systemic infectious diseases, but preclinical and clinical trials have pointed out controlling neuroinflammatory events to avoid the development of this sequel. In this minireview, we point to the possible mechanisms that triggers long-term cognitive decline, proposing the acute neuroinflammatory events as a potential therapeutical target to treat this sequel that has been associated to several infectious diseases, such as malaria, sepsis, and, more recently, the new SARS-Cov2 infection.

Report of the intergovernmental panel on climate change: implications for the mental health policy of children and adolescents in Europe-a scoping review

Climate change is a worldwide challenge. Its consequences do encompass severe threats not only for the existence and somatic health, but also for the mental health of children and adolescents. Mental health can be impaired by three types of consequences. Direct consequences of climate change, such as natural disasters and indirect consequences, such as loss of land, flight and migration, exposure to violence, change of social, ecological, economic or cultural environment. Moreover, the increasing awareness of the existential dimension of climate change in children and adolescents can influence their well-being or challenge their mental health. Consequences of climate change for somatic health may interact with mental health or have psychological sequelae in children and adolescents. Based on the estimates by the United Nations Intergovernmental Panel on Climate Change, we have summarized current data on these differential pathways as to how climate change affects the mental health of children worldwide through selective literature research on Pubmed. Mental health sequelae of direct and indirect consequences of climate change, increased awareness and physical health problems caused by climate change are presented. We give insights into special vulnerabilities of children and adolescents and identify high-risk groups. As the "Fridays for Future" movement has been initiated in northern Europe, we will discuss these results with a focus on children and adolescents in Europe. The results indicate that climate change is a serious threat to children and adolescent mental health. Children´s rights, mental health and climate change should not continue to be seen as separate points; instead, they need to be brought together to address this major challenge determining the future of our children and their descendants.

Risk factors for neurological complications in children with Flavivirus infection

This study aims to characterize the acute neurological manifestations caused by DENV, ZIKV, and YFV during hospitalization; identify the risk factors associated with persistent neurological complications after discharge; and evaluate the time to resolution during clinical follow-up. A prospective study evaluated 505 children, between March 2014 and July 2019, hospitalized with neurological manifestations and that doctors suspected infection of the central nervous system (CNS). Viral infection of collected cerebrospinal fluid (CSF) was confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR). Patients were clinically followed up after hospital discharge. Analysis of predictive factors and survival curves was performed. This study identified clinical symptoms and changes in the CSF laboratory, electroencephalogram (EEG), and CNS image as predictors of complications in children with confirmed infection in the CNS by DENV, ZIKV, or YFV. No statistical difference was found (p value 0.574) in the time to the resolution of complications in children after hospital discharge between the three types of flaviviruses. Children with YFV, detected in CSF samples, had a 53% higher risk of developing neurological complications. Performing etiological diagnosis by RT-PCR of CSF samples of children with neurological manifestations, especially during Flavivirus outbreaks, is an essential tool for improving the prognosis and clinical follow-up of these patients.

Comparison of the Impact of Zika and Dengue Virus Infection, and Other Acute Illnesses of Unidentified Origin on Cognitive Functions in a Prospective Cohort in Chiapas Mexico

Zika has been associated with a variety of severe neurologic manifestations including meningitis and encephalitis. We hypothesized that it may also cause mild to subclinical neurocognitive alterations during acute infection or over the long term. In this observational cohort study, we explored whether Zika cause subclinical or mild neurocognitive alterations, estimate its frequency and duration, and compare it to other acute illnesses in a cohort of people with suspected Zika infection, in the region of Tapachula in Chiapas, Mexico during 2016-2018. We enrolled patients who were at least 12 years old with suspected Zika virus infection and followed them up for 6 months. During each visit participants underwent a complete clinical exam, including a screening test for neurocognitive dysfunction (Montreal Cognitive Assessment score). We enrolled 406 patients [37 with Zika, 73 with dengue and 296 with other acute illnesses of unidentified origin (AIUO)]. We observed a mild and transient impact over cognitive functions in patients with Zika, dengue and with other AIUO. The probability of having an abnormal MoCA score (<26 points) was significantly higher in patients with Zika and AIUO than in those with dengue. Patients with Zika and AIUO had lower memory scores than patients with dengue (Zika vs. Dengue: -0.378, 95% CI-0.678 to -0.078; p = 0.014: Zika vs. AIUO 0.264, 95% CI 0.059, 0.469; p = 0.012). The low memory performance in patients with Zika and AIUO accounts for most of the differences in the overall MoCA score when compared with patients with dengue. Our results show a decrease in cognitive function during acute illness and provides no evidence to support the hypothesis that Zika might cause neurocognitive alterations longer than the period of acute infection or different to other infectious diseases. While effects on memory or perhaps other cognitive functions over the long term are possible, larger studies using more refined tools for neurocognitive functioning assessment are needed to identify these. Trial Registration: NCT02831699.

Zika virus-like particle vaccine protects AG129 mice and rhesus macaques against Zika virus

Background

Zika virus (ZIKV), a mosquito-borne flavivirus, is a re-emerging virus that constitutes a public health threat due to its recent global spread, recurrent outbreaks, and infections that are associated with neurological abnormalities in developing fetuses and Guillain-Barré syndrome in adults. To date, there are no approved vaccines against ZIKV infection. Various preclinical and clinical development programs are currently ongoing in an effort to bring forward a vaccine for ZIKV.

Methodology/Principle findings

We have developed a ZIKV vaccine candidate based on Virus-Like-Particles (VLPs) produced in HEK293 mammalian cells using the prM (a precursor to M protein) and envelope (E) structural protein genes from ZIKV. Transient transfection of cells via plasmid and electroporation produced VLPs which were subsequently purified by column chromatography yielding approximately 2mg/L. Initially, immunogenicity and efficacy were evaluated in AG129 mice using a dose titration of VLP with and without Alhydrogel 2% (alum) adjuvant. We found that VLP with and without alum elicited ZIKV-specific serum neutralizing antibodies (nAbs) and that titers correlated with protection. A follow-up immunogenicity and efficacy study in rhesus macaques was performed using VLP formulated with alum. Multiple neutralization assay methods were performed on immune sera including a plaque reduction neutralization test, a microneutralization assay, and a Zika virus Renilla luciferase neutralization assay. All of these assays indicate that following immunization, VLP induces high titer nAbs which correlate with protection against ZIKV challenge.

Conclusions/Significance

These studies confirm that ZIKV VLPs could be efficiently generated and purified. Upon VLP immunization, in both mice and NHPs, nAb was induced that correlate with protection against ZIKV challenge. These studies support translational efforts in developing a ZIKV VLP vaccine for evaluation in human clinical trials.

Zika virus (ZIKV) is a significant global health threat particularly due to the speed in which epidemics can occur. The resulting infections have been demonstrated to harm a developing fetus and, in some adults, be a co-factor for the development of Guillain-Barré syndrome. ZIKV is typically spread by the Aedes mosquito, but sexual transmission is also possible. We sought to develop a ZIKV prophylactic vaccine based on surface glycoproteins of the virus that would be devoid of any viral genetic material. This Virus-Like-Particle (VLP) was generated in vitro following introduction of plasmid DNA encoding Zika structural protein (prM-E) genes into mammalian cells. The aluminum-adjuvanted VLP induced nAbs in mice and nonhuman primates and protected against ZIKV challenge in vivo. These studies support the evaluation of this VLP candidate vaccine in human clinical trials.

Encephalitis in Previously Healthy Children

Encephalitis is defined as altered mental status for more than 24 hours accompanied by 2 or more findings concerning for inflammation of the brain parenchyma: fever, seizures or other focal neurologic disorders, cerebrospinal fluid pleocytosis, and abnormal neuroimaging and electroencephalographic findings. Herpes simplex virus causes the most severe form of virus-induced encephalitis; the early administration of acyclovir can improve the prognosis of this disease. The rising interest in autoimmune causes of encephalitis, most notably anti-N-methyl-d-aspartate receptor, should prompt the clinician to consider immunomodulatory treatments, which may improve outcomes. A broad testing panel may be necessary to detect the etiologic agent; a few published pediatric cases suggest that infectious and autoimmune causes may occur concurrently in the same patient with encephalitis. More than 40% of children diagnosed as having encephalitis will not return to their previous level of neurologic function after resolution of their disease, although outcomes are highly variable depending on the etiologic agent.

Role of Inflammation in Virus Pathogenesis during Pregnancy

Viral infections during pregnancy lead to a spectrum of maternal and fetal outcomes, ranging from asymptomatic disease to more critical conditions presenting with severe maternal morbidity, stillbirth, preterm birth, intrauterine growth restriction, and fetal congenital anomalies, either apparent at birth or later in life. In this article, we review the pathogenesis of several viral infections that are particularly relevant in the context of pregnancy and intrauterine inflammation. Understanding the diverse mechanisms employed by viral pathogens as well as the repertoire of immune responses induced in the mother may help to establish novel therapeutic options to attenuate changes in the maternal-fetal interface and prevent adverse pregnancy outcomes.

Long-term persistence of infectious Zika virus: Inflammation and behavioral sequela in mice

The neurodevelopmental defects associated with ZIKV infections early in pregnancy are well documented, however the potential defects and long-term consequences associated with milder infections in late pregnancy and perinatal period are less well understood. To model these, we challenged 1 day old (P1) immunocompetent C57BL/6 mice with ZIKV. The animals developed a transient neurological syndrome including unsteady gait, kinetic tremors, severe ataxia and seizures 10-15 days post-infection (dpi) but symptoms subsided after a week, and most animals survived. Despite apparent recovery, MRI of convalescent mice show reduced cerebellar volume that correlates with altered coordination and motor function as well as hyperactivity and impulsivity. Persistent mRNA levels of pro-inflammatory genes including Cd80, Il-1α, and Ifn-γ together with Cd3, Cd8 and perforin (PrfA), suggested persistence of low-grade inflammation. Surprisingly, the brain parenchyma of convalescent mice harbor multiple small discrete foci with viral antigen, active apoptotic processes in neurons, and cellular infiltrates, surrounded by activated astrocytes and microglia as late as 1-year post-infection. Detection of negative-sense strand viral RNA and isolation of infectious virus derived from these convalescent mice by blinded passage in Vero cells confirmed long-term persistence of replicating ZIKV in CNS of convalescent mice. Although the infection appears to persist in defined reservoirs within CNS, the resulting inflammation could increase the risk of neurodegenerative disorders. This raises concern regarding possible long-term effects in asymptomatic children exposed to the virus and suggests that long-term neurological and behavioral monitoring as well as anti-viral treatment to clear virus from the CNS may be useful in patients exposed to ZIKV at an early age.

Animal models of congenital zika syndrome provide mechanistic insight into viral pathogenesis during pregnancy

In utero Zika virus (ZIKV; family Flaviviridae) infection causes a distinct pattern of birth defects and disabilities in the developing fetus and neonate that has been termed congenital zika syndrome (CZS). Over 8,000 children were affected by the 2016 to 2017 ZIKV outbreak in the Americas, many of whom developed CZS as a result of in utero exposure. To date, there is no consensus about how ZIKV causes CZS; animal models, however, are providing mechanistic insights. Using nonhuman primates, immunocompromised mice, immunocompetent mice, and other animal models (e.g., pigs, sheep, guinea pigs, and hamsters), studies are showing that maternal immunological responses, placental infection and inflammation, as well as viral genetic factors play significant roles in predicting the downstream consequences of in utero ZIKV infection on the development of CZS in offspring. There are thousands of children suffering from adverse consequences of CZS. Therefore, the animal models developed to study ZIKV-induced adverse outcomes in offspring could provide mechanistic insights into how other viruses, including influenza and hepatitis C viruses, impact placental viability and fetal growth to cause long-term adverse outcomes in an effort to identify therapeutic treatments.

Neurocognitive impacts of arbovirus infections

Arthropod-borne viruses or arbovirus, are most commonly associated with acute infections, resulting on various symptoms ranging from mild fever to more severe disorders such as hemorrhagic fever. Moreover, some arboviral infections can be associated with important neuroinflammation that can trigger neurological disorders including encephalitis, paralysis, ophthalmological impairments, or developmental defects, which in some cases, can lead to long-term defects of the central nervous system (CNS). This is well illustrated in Zika virus-associated congenital brain malformations but also in West Nile virus-induced synaptic dysfunctions that can last well beyond infection and lead to cognitive deficits. Here, we summarize clinical and mechanistic data reporting on cognitive disturbances triggered by arboviral infections, which may highlight growing public health issues spanning the five continents.

West Nile Virus-Induced Neurologic Sequelae-Relationship to Neurodegenerative Cascades and Dementias

Purpose of Review

West Nile virus (WNV) emerged from Central Africa in the 1990s and is now endemic throughout much of the world. Twenty years after its introduction in the USA, it is becoming apparent that neurological impairments can persist for years following infection. Here, we review the epidemiological data in support of such long-term deficits and discuss possible mechanisms that drive these persistent manifestations.

Recent Findings

Focusing on the recently discovered antimicrobial roles of amyloid and alpha-synuclein, we connect WNV late pathology to overlapping features encountered in neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. We also summarize new research on microglial activation and engulfment of neural synapses seen in recovered WNV as well as in neurodegenerative diseases, and discuss how loss of integrity of the blood-brain barrier (BBB) may exacerbate this process.

Summary

Neuroinvasive viral infections such as WNV may be linked epidemiologically and mechanistically to neurodegeneration. This may open doors to therapeutic options for hitherto untreatable infectious sequelae; additionally, it may also shed light on the possible infectious etiologies of age-progressive neurodegenerative dementias.

Human Coronaviruses and Other Respiratory Viruses: Underestimated Opportunistic Pathogens of the Central Nervous System?

Respiratory viruses infect the human upper respiratory tract, mostly causing mild diseases. However, in vulnerable populations, such as newborns, infants, the elderly and immune-compromised individuals, these opportunistic pathogens can also affect the lower respiratory tract, causing a more severe disease (e.g., pneumonia). Respiratory viruses can also exacerbate asthma and lead to various types of respiratory distress syndromes. Furthermore, as they can adapt fast and cross the species barrier, some of these pathogens, like influenza A and SARS-CoV, have occasionally caused epidemics or pandemics, and were associated with more serious clinical diseases and even mortality. For a few decades now, data reported in the scientific literature has also demonstrated that several respiratory viruses have neuroinvasive capacities, since they can spread from the respiratory tract to the central nervous system (CNS). Viruses infecting human CNS cells could then cause different types of encephalopathy, including encephalitis, and long-term neurological diseases. Like other well-recognized neuroinvasive human viruses, respiratory viruses may damage the CNS as a result of misdirected host immune responses that could be associated with autoimmunity in susceptible individuals (virus-induced neuro-immunopathology) and/or viral replication, which directly causes damage to CNS cells (virus-induced neuropathology). The etiological agent of several neurological disorders remains unidentified. Opportunistic human respiratory pathogens could be associated with the triggering or the exacerbation of these disorders whose etiology remains poorly understood. Herein, we present a global portrait of some of the most prevalent or emerging human respiratory viruses that have been associated with possible pathogenic processes in CNS infection, with a special emphasis on human coronaviruses.

Impression Cytology Is a Non-invasive and Effective Method for Ocular Cell Retrieval of Zika Infected Babies: Perspectives in OMIC Studies

IMPORTANCE

Non-invasive techniques for retrieving ocular surface cells from babies infected by zika virus (ZIKV) during the gestational period remain to be determined.

OBJECTIVES

The aim of this study was to describe an optimized impression cytology method for the isolation of viable cells from Zika infected babies with and without Congenital Zika Syndrome (CZS) in satisfactory amount and quality to enable easy adoption in the field and application in the context of genomic and molecular approaches.

DESIGN SETTINGS AND PARTICIPANTS

Ocular surface samples were obtained with a hydrophilic nitrocellulose membrane (through optimized impression cytology method) from twelve babies referred to the Pediatric Service of the Antonio Pedro Hospital, Universidade Federal Fluminense (UFF), Niteroi, Rio de Janeiro, Brazil. After an authorized written informed consent from the parents, samples were collected from both eyes of 12 babies (4 babies with maternal ZIKV exposure during gestation and presence of clinical signs which included ocular abnormalities and microcephaly; 4 babies with maternal ZIKV exposure during gestation but no clinical signs; and 4 unaffected control babies with negative PCR for Zika virus and without clinical signs). Cells were used for microscopy analyses and evaluated for their suitability for downstream molecular applications in transcriptomic and proteomic experiments.

RESULTS

Our optimized impression cytology protocol enabled the capture of a considerable number of viable cells. The microscopic features of the conjunctival epithelial cells were described by both direct analysis of the membrane-attached cells and analysis of cytospinned captured cells using several staining procedures. Epithelial basal, polyhedral and goblet cells were clearly identified in all groups. All cases of ZIKV infected babies showed potential morphological alterations (cell keratinization, pyknosis, karyolysis, anucleation, and vacuolization). Molecular approaches were also performed in parallel. Genomic DNA and RNA were successfully isolated from all samples to enable the establishment of transcriptomic and proteomic studies.

CONCLUSIONS AND RELEVANCE

Our method proved to be a suitable, fast, and non-invasive tool to obtain ocular cell preparations from babies with and without Zika infection. The method yielded sufficient cells for detailed morphological and molecular analyses of samples. We discuss perspectives for the application of impression cytology in the context of ZIKV studies in basic and clinical research.

Flaviviruses as agents of childhood central nervous system infections in Brazil

Flaviviruses are agents of a major emerging human public health issue and members of this genus have been associated with central nervous system (CNS) infections. In Brazil, a country endemic for some arboviruses, the most clinically relevant neurotropic flaviviruses include Dengue virus and Zika virus. Flaviviruses cause diseases ranging from mild or sub-clinical infections to severe cases as CNS infections. There is a lack of data about the incidence of flaviviruses in the CNS of children in Brazil. In this review, we provide a general overview of several flaviviruses that cause CNS infections in Brazilian children and explore the importance of epidemiological surveillance of CNS infections in cases of flavivirus infections.

Flaviviruses as agents of childhood central nervous system infections in Brazil

Flaviviruses are agents of a major emerging human public health issue, and members of the Flavivirus genus have been associated with central nervous system (CNS) infections. In Brazil, a country endemic for some arboviruses, the most clinically relevant neurotropic flaviviruses include dengue virus and Zika virus. Flaviviruses cause diseases ranging from mild or subclinical infections to severe cases as CNS infections. There is a lack of data about the incidence of flaviviruses in the CNS of children in Brazil. In this review, we provide a general overview of several flaviviruses that cause CNS infections in Brazilian children and explore the importance of epidemiologic surveillance of CNS infections in cases of Flavivirus infections.