Wild-Type Yellow Fever Virus RNA in Cerebrospinal Fluid of Child

Square the Circle: Diversity of Viral Pathogens Causing Neuro-Infectious Diseases

Neuroinfections rank among the top ten leading causes of child mortality globally, even in high-income countries. The crucial determinants for successful treatment lie in the timing and swiftness of diagnosis. Although viruses constitute the majority of infectious neuropathologies, diagnosing and treating viral neuroinfections remains challenging. Despite technological advancements, the etiology of the disease remains undetermined in over half of cases. The identification of the pathogen becomes more difficult when the infection is caused by atypical pathogens or multiple pathogens simultaneously. Furthermore, the modern surge in global passenger traffic has led to an increase in cases of infections caused by pathogens not endemic to local areas. This review aims to systematize and summarize information on neuroinvasive viral pathogens, encompassing their geographic distribution and transmission routes. Emphasis is placed on rare pathogens and cases involving atypical pathogens, aiming to offer a comprehensive and structured catalog of viral agents with neurovirulence potential.

Neuroinvasion of emerging and re-emerging arboviruses: A scoping review

Background

Arboviruses are RNA viruses and some have the potential to cause neuroinvasive disease and are a growing threat to global health.

Objectives

Our objective is to identify and map all aspects of arbovirus neuroinvasive disease, clarify key concepts, and identify gaps within our knowledge with appropriate future directions related to the improvement of global health.

Methods

Sources of Evidence: A scoping review of the literature was conducted using PubMed, Scopus, ScienceDirect, and Hinari. Eligibility Criteria: Original data including epidemiology, risk factors, neurological manifestations, neuro-diagnostics, management, and preventive measures related to neuroinvasive arbovirus infections was obtained. Sources of evidence not reporting on original data, non-English, and not in peer-reviewed journals were removed. Charting Methods: An initial pilot sample of 30 abstracts were reviewed by all authors and a Cohen's kappa of κ = 0.81 (near-perfect agreement) was obtained. Records were manually reviewed by two authors using the Rayyan QCRI software.

Results

A total of 171 records were included. A wide array of neurological manifestations can occur most frequently, including parkinsonism, encephalitis/encephalopathy, meningitis, flaccid myelitis, and Guillain-Barré syndrome. Magnetic resonance imaging of the brain often reveals subcortical lesions, sometimes with diffusion restriction consistent with acute ischemia. Vertical transmission of arbovirus is most often secondary to the Zika virus. Neurological manifestations of congenital Zika syndrome, include microcephaly, failure to thrive, intellectual disability, and seizures. Cerebrospinal fluid analysis often shows lymphocytic pleocytosis, elevated albumin, and protein consistent with blood-brain barrier dysfunction.

Conclusions

Arbovirus infection with neurological manifestations leads to increased morbidity and mortality. Risk factors for disease include living and traveling in an arbovirus endemic zone, age, pregnancy, and immunosuppressed status. The management of neuroinvasive arbovirus disease is largely supportive and focuses on specific neurological complications. There is a need for therapeutics and currently, management is based on disease prevention and limiting zoonosis.

Aminopyrimidine Derivatives as Multiflavivirus Antiviral Compounds Identified from a Consensus Virtual Screening Approach

Around three billion people are at risk of infection by the dengue virus (DENV) and potentially other flaviviruses. Worldwide outbreaks of DENV, Zika virus (ZIKV), and yellow fever virus (YFV), the lack of antiviral drugs, and limitations on vaccine usage emphasize the need for novel antiviral research. Here, we propose a consensus virtual screening approach to discover potential protease inhibitors (NS3pro) against different flavivirus. We employed an in silico combination of a hologram quantitative structure-activity relationship (HQSAR) model and molecular docking on characterized binding sites followed by molecular dynamics (MD) simulations, which filtered a data set of 7.6 million compounds to 2,775 hits. Lastly, docking and MD simulations selected six final potential NS3pro inhibitors with stable interactions along the simulations. Five compounds had their antiviral activity confirmed against ZIKV, YFV, DENV-2, and DENV-3 (ranging from 4.21 ± 0.14 to 37.51 ± 0.8 μM), displaying aggregator characteristics for enzymatic inhibition against ZIKV NS3pro (ranging from 28 ± 7 to 70 ± 7 μM). Taken together, the compounds identified in this approach may contribute to the design of promising candidates to treat different flavivirus infections.

1-Sulfonyl-3-amino-1H-1,2,4-triazoles as Yellow Fever Virus Inhibitors: Synthesis and Structure-Activity Relationship

Yellow fever virus (YFV) transmitted by infected mosquitoes causes an acute viral disease for which there are no approved small-molecule therapeutics. Our recently developed machine learning models for YFV inhibitors led to the selection of a new pyrazolesulfonamide derivative RCB16003 with acceptable in vitro activity. We report that the N-phenyl-1-(phenylsulfonyl)-1H-1,2,4-triazol-3-amine class, which was recently identified as active non-nucleoside reverse transcriptase inhibitors against HIV-1, can also be repositioned as inhibitors of yellow fever virus replication. As compared to other Flaviviridae or Togaviridae family viruses tested, both compounds RCB16003 and RCB16007 demonstrate selectivity for YFV over related viruses, with only RCB16007 showing some inhibition of the West Nile virus (EC50 7.9 μM, CC50 17 μM, SI 2.2). We also describe the absorption, distribution, metabolism, and excretion (ADME) in vitro and pharmacokinetics (PK) for RCB16007 in mice. This compound had previously been shown to not inhibit hERG, and we now describe that it has good metabolic stability in mouse and human liver microsomes, low levels of CYP inhibition, high protein binding, and no indication of efflux in Caco-2 cells. A single-dose oral PK study in mice has a T1/2 of 3.4 h and Cmax of 1190 ng/mL, suggesting good availability and stability. We now propose that the N-phenyl-1-(phenylsulfonyl)-1H-1,2,4-triazol-3-amine class may be prioritized for in vivo efficacy testing against YFV.

Serum soluble mediators as prognostic biomarkers for morbidity, disease outcome, and late-relapsing hepatitis in yellow fever patients

This study described a soluble mediator storm in acute Yellow Fever/YF infection along the kinetic timeline towards convalescent disease. The analyses of the YF Viral RNAnemia, chemokines, cytokines, and growth factors were performed in YF patients at acute/(D1-15) and convalescent/(D16-315) phases. Patients with acute YF infection displayed a trimodal viremia profile spreading along D3, D6, and D8-14. A massive storm of mediators was observed in acute YF. Higher levels of mediators were observed in YF with higher morbidity scores, patients under intensive care, and those progressing to death than in YF patients who progress to late-relapsing hepatitis/L-Hep. A unimodal peak of biomarkers around D4-6 with a progressive decrease towards D181-315 was observed in non-L-Hep patients, while a bimodal pattern with a second peak around D61-90 was associated with L-Hep. This study provided a comprehensive landscape of evidence that distinct immune responses drive pathogenesis, disease progression, and L-Hep in YF patients.

Neuropathology of yellow fever autopsy cases

BACKGROUND

Yellow fever is a viral hemorrhagic fever caused by yellow fever virus, a mosquito-borne flavivirus. Despite an effective vaccine, major outbreaks continue to occur around the world. Even though it is not a proven neurotropic virus, neurological symptoms in more severe clinical forms are frequent. The understanding of this apparent paradox is still rarely addressed in literature.

METHODS

The brains of thirty-eight patients with yellow fever confirmed by RT-PCR, who underwent autopsy, were analyzed morphologically to identify and characterize neuropathological changes. The data were compared with brains collected from individuals without the disease, as a control group. Both cases and controls were subdivided according to the presence or absence of co-concurrent septic shock, to exclude changes of the sepsis associated encephalopathy. To verify possible morphological differences between the yellow fever cases groups, between the control groups, and between the cases and the controls, we applied the statistical tests Fisher's exact test and chi-square, with p values < 0.05 considered statistically significant.

RESULTS

All cases and controls presented, at least focally, neuropathological changes, which included edema, meningeal and parenchymal inflammatory infiltrate and hemorrhages, and perivascular inflammatory infiltrate. We did not find an unequivocal aspect of encephalitis. The only parameter that, after statistical analysis, can be attributed to yellow fever was the perivascular inflammatory infiltrate.

CONCLUSIONS

The neuropathological findings are sufficient to justify the multiple clinical neurologic disturbances detected in the YF cases. Since most of the parameters evaluated did not show statistically significant difference between cases and controls, an explanation for most of the neuropathological findings may be the vascular changes, consequent to shock induced endotheliopathy, associated with stimulation of the immune system inherent to systemic infectious processes. The statistical difference obtained in yellow fever cases regarding perivascular infiltrate can be can be explained by the immune activation inherent to the condition.

Crystal structure of the Ilheus virus helicase: implications for enzyme function and drug design

Background

The Ilheus virus (ILHV) is an encephalitis associated arthropod-borne flavivirus. It was first identified in Ilheus City in the northeast Brazil before spreading to a wider geographic range. No specific vaccines or drugs are currently available for the treatment of ILHV infections. The ILHV helicase, like other flavivirus helicases, possesses 5ʹ-triphosphatase activity. This allows it to perform ATP hydrolysis to generate energy as well as sustain double-stranded RNA’s unwinding during ILHV genome replication. Thus, ILHV helicase is an ideal target for inhibitor design.

Results

We determined the crystal structure of the ILHV helicase at 1.75-Å resolution. We then conducted molecular docking of ATP-Mn²⁺ to the ILHV helicase. Comparisons with related flavivirus helicases indicated that both the NTP and the RNA-ILHV helicase binding sites were conserved across intra-genus species. This suggested that ILHV helicase adopts an identical mode in recognizing ATP/Mn²⁺. However, the P-loop in the active site showed a distinctive conformation; reflecting a different local structural rearrangement. ILHV helicase enzymatic activity was also characterized. This was found to be relatively lower than that of the DENV, ZIKV, MVE, and ALSV helicases. Our structure-guided mutagenesis revealed that R26A, E110A, and Q280A greatly reduced the ATPase activities. Moreover, we docked two small molecule inhibitors of DENV helicase (ST-610 and suramin) to the ILHV helicase and found that these two molecules had the potential to inhibit the activity of ILHV helicase as well.

Conclusion

High-resolution ILHV helicase structural analysis demonstrates the key amino acids of ATPase activities and could be useful for the design of inhibitors targeting the helicase of ILHV.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00777-8.

Wild-type Yellow fever virus in cerebrospinal fluid from fatal cases in Brazil, 2018

Yellow fever virus (YFV) is the causative agent of yellow fever (YF), a hemorrhagic and viscerotropic acute disease. Severe YF has been described in approximately 15-25% of YF patients, with 20-50% of severe YF cases being fatal. Here we analyzed cerebrospinal fluid (CSF) samples collected during the YF outbreak in Brazil in 2018, aiming to investigate CNS neuroinvasion in fatal YFV cases. YFV RNA was screened by RT-qPCR targeting the 3'UTR region of the YFV genome in CSF. CSF samples were tested for the presence of anti-YFV IgM and neutralizing antibodies, coupled with routine laboratory examinations. Among the 13 patients studied, we detected anti-YFV IgM in CSF from eight patients and YFV RNA in CSF from five patients. YFV RNA genomic load in CSF samples ranged from 1.75×103 to 5.42×103 RNA copies/mL. We genotyped YFV from three CSF samples that grouped with other YFV samples from the 2018 outbreak in Brazil within the South-American I genotype. Even though descriptions of neurologic manifestations due to wild type YFV (WT-YFV) infection are rare, since the last YF outbreak in Brazil in 2017-2018, a few studies have demonstrated WT-YFV RNA in CSF samples from YF fatal cases. Serological tests indicated the presence of IgM and neutralizing antibodies against YFV in CSF samples from two patients. Although the presence of viral RNA, IgM and neutralizing antibodies in CSF samples could indicate neuroinvasiveness, further studies are needed to better elucidate the role of YFV neuroinvasion and possible impacts in disease pathogenesis.

Neuroimaging features of arboviral infections in the Americas

Arboviruses are zoonotic RNA viruses maintained in nature in cycles that involve arthropod vectors. The arboviruses that cause disease in humans are members of the Bunyaviridae, Togaviridae, Flaviviridae, and Reoviridae families. These viral species have geographically and climatically restricted distributions due to particular ecological and vector features. The main emerging arboviruses in the Americas are dengue, zika, yellow fever (Flaviviridae), and chikungunya (Togaviridae). All of these viruses can be transmitted by the Aedes aegypti and Aedes albopictus mosquitoes. Although not commonly, these infections are associated with neurological complications, characterized mainly by hemorrhage, encephalitis, myelitis, acute disseminated encephalomyelitis, Guillain-Barré syndrome, and/or congenital malformations. This review describes the imaging features of the neurological complications of these emerging arbovirus infections.

The impact of viral infections on childhood central nervous system infections

BACKGROUND

Viruses are a common cause of central nervous system (CNS) infections. However, studies of CNS viral pathogens in pediatric patients are poorly explored because viral infections are often erroneously diagnosed as bacterial infections.

METHODS

299 CNS samples were collected from pediatric patients aged from one month to 14 years old. A total of 140 viral meningitis cases that met the inclusion criteria were included in this study. In 38 of the 140 cerebral spinal fluid (CSF) samples (27.1%), conventional and real-time PCR were used to identify viruses commonly associated with CNS infections.

RESULTS

Among them, 23 patients (16.5%) tested positive for flaviviruses such as dengue, Zika, and yellow fever virus, eight patients (5.7%) were positive for enterovirus (ENTV), and six patients (4.3%) were positive for human herpesvirus 1/2. We also identified one case of dengue virus and ENTV co-infection.

CONCLUSIONS

A correlation between clinical symptoms and laboratory findings for the viruses was identified. Our study also reinforces the importance of including viruses in the laboratory diagnosis of CNS infections especially flaviviruses, which assists public health authorities in implementing early interventions.

Neurologic Manifestations of the World Health Organization's List of Pandemic and Epidemic Diseases

The World Health Organization (WHO) monitors the spread of diseases globally and maintains a list of diseases with epidemic or pandemic potential. Currently listed diseases include Chikungunya, cholera, Crimean-Congo hemorrhagic fever, Ebola virus disease, Hendra virus infection, influenza, Lassa fever, Marburg virus disease, Neisseria meningitis, MERS-CoV, monkeypox, Nipah virus infection, novel coronavirus (COVID-19), plague, Rift Valley fever, SARS, smallpox, tularemia, yellow fever, and Zika virus disease. The associated pathogens are increasingly important on the global stage. The majority of these diseases have neurological manifestations. Those with less frequent neurological manifestations may also have important consequences. This is highlighted now in particular through the ongoing COVID-19 pandemic and reinforces that pathogens with the potential to spread rapidly and widely, in spite of concerted global efforts, may affect the nervous system. We searched the scientific literature, dating from 1934 to August 2020, to compile data on the cause, epidemiology, clinical presentation, neuroimaging features, and treatment of each of the diseases of epidemic or pandemic potential as viewed through a neurologist's lens. We included articles with an abstract or full text in English in this topical and scoping review. Diseases with epidemic and pandemic potential can be spread directly from human to human, animal to human, via mosquitoes or other insects, or via environmental contamination. Manifestations include central neurologic conditions (meningitis, encephalitis, intraparenchymal hemorrhage, seizures), peripheral and cranial nerve syndromes (sensory neuropathy, sensorineural hearing loss, ophthalmoplegia), post-infectious syndromes (acute inflammatory polyneuropathy), and congenital syndromes (fetal microcephaly), among others. Some diseases have not been well-characterized from a neurological standpoint, but all have at least scattered case reports of neurological features. Some of the diseases have curative treatments available while in other cases, supportive care remains the only management option. Regardless of the pathogen, prompt, and aggressive measures to control the spread of these agents are the most important factors in lowering the overall morbidity and mortality they can cause.

Re-Emergence of Yellow Fever in Brazil during 2016-2019: Challenges, Lessons Learned, and Perspectives

Yellow fever (YF) is a re-emerging viral zoonosis caused by the Yellow Fever virus (YFV), affecting humans and non-human primates (NHP). YF is endemic in South America and Africa, being considered a burden for public health worldwide despite the availability of an effective vaccine. Acute infectious disease can progress to severe hemorrhagic conditions and has high rates of morbidity and mortality in endemic countries. In 2016, Brazil started experiencing one of the most significant YF epidemics in its history, with lots of deaths being reported in regions that were previously considered free of the disease. Here, we reviewed the historical aspects of YF in Brazil, the epidemiology of the disease, the challenges that remain in Brazil’s public health context, the main lessons learned from the recent outbreaks, and our perspective for facing future YF epidemics.

An Experimental and Theoretical Approach to Understand Fever, DENF & its Cure

Fever is a response of a human body, due to an increase in the temperature, against certain stimuli. It may be associated with several reasons and one of the major causes of fever is a mosquito bite. Fever due to dengue virus (DENV) infection is being paid most attention out of several other fever types because of a large number of deaths reported worldwide. Dengue virus is transmitted by biting of the mosquitoes, Aedes aegypti and Aedes albopictus. DENV1, DENV2, DENV3 and DENV4 are the four serotypes of dengue virus and these serotypes have 65% similarities in their genomic structure. The genome of DENV is composed of single-stranded RNA and it encodes for the polyprotein. Structural and non-structural proteins (nsP) are the two major parts of polyprotein. Researchers have paid high attention to the non-structural protease (nsP) of DENV like nsP1, nsP2A, nsP2B, nsP3, nsP4A, nsP4B and nsP5. The NS2B-NS3 protease of DENV is the prime target of the researchers as it is responsible for the catalytic activity. In the present time, Dengvaxia (vaccine) is being recommended to patients suffering severely from DENV infection in few countries only. Till date, neither a vaccine nor an effective medicine is available to combat all four serotypes. This review describes the fever, its causes, and studies to cure the infection due to DENV using theoretical and experimental approaches.

Fatal Outcome of Ilheus Virus in the Cerebrospinal Fluid of a Patient Diagnosed with Encephalitis

Ilheus virus is an arbovirus with the potential for central nervous system involvement. Accurate diagnosis is a challenge due to similar clinical symptoms and serologic cross-reactivity with other flaviviruses. Here, we describe the first documented case of a fatal outcome following the identification of Ilheus virus in the cerebrospinal fluid (CSF) of a patient with cerebral encephalitis in Brazil.

Recent sylvatic yellow fever virus transmission in Brazil: the news from an old disease

Yellow fever (YF) is an acute viral disease, affecting humans and non-human primates (NHP), caused by the yellow fever virus (YFV). Despite the existence of a safe vaccine, YF continues to cause morbidity and mortality in thousands of people in Africa and South America. Since 2016, massive YF outbreaks have taken place in Brazil, reaching YF-free zones, causing thousands of deaths of humans and NHP. Here we reviewed the main epidemiological aspects, new clinical findings in humans, and issues regarding YFV infection in vectors and NHP in Brazil. The 2016-2019 YF epidemics have been considered the most significant outbreaks of the last 70 years in the country, and the number of human cases was 2.8 times higher than total cases in the previous 36 years. A new YFV lineage was associated with the recent outbreaks, with persistent circulation in Southeast Brazil until 2019. Due to the high number of infected patients, it was possible to evaluate severity and death predictors and new clinical features of YF. Haemagogus janthinomys and Haemagogus leucocelaenus were considered the primary vectors during the outbreaks, and no human case suggested the occurrence of the urban transmission cycle. YFV was detected in a variety of NHP specimens presenting viscerotropic disease, similar to that described experimentally. Further studies regarding NHP sensitivity to YFV, YF pathogenesis, and the duration of the immune response in NHP could contribute to YF surveillance, control, and future strategies for NHP conservation.

Modelling Neurotropic Flavivirus Infection in Human Induced Pluripotent Stem Cell-Derived Systems

Generation of human induced pluripotent stem cells (hiPSCs) and their differentiation into a variety of cells and organoids have allowed setting up versatile, non-invasive, ethically sustainable, and patient-specific models for the investigation of the mechanisms of human diseases, including viral infections and host–pathogen interactions. In this study, we investigated and compared the infectivity and replication kinetics in hiPSCs, hiPSC-derived neural stem cells (NSCs) and undifferentiated neurons, and the effect of viral infection on host innate antiviral responses of representative flaviviruses associated with diverse neurological diseases, i.e., Zika virus (ZIKV), West Nile virus (WNV), and dengue virus (DENV). In addition, we exploited hiPSCs to model ZIKV infection in the embryo and during neurogenesis. The results of this study confirmed the tropism of ZIKV for NSCs, but showed that WNV replicated in these cells with much higher efficiency than ZIKV and DENV, inducing massive cell death. Although with lower efficiency, all flaviviruses could also infect pluripotent stem cells and neurons, inducing similar patterns of antiviral innate immune response gene expression. While showing the usefulness of hiPSC-based infection models, these findings suggest that additional virus-specific mechanisms, beyond neural tropism, are responsible for the peculiarities of disease phenotype in humans.