A yellow flag on the horizon: The looming threat of yellow fever to North America

First DFT-supported point of care and novel electrochemical biosensing: Determination of yellow fever NS1 antibody in human plasma

In our study, we developed a point of care electrochemical biosensing platform based on the functionalized cysteine-positioned gold electrode to diagnose yellow fever disease from human plasma samples. The developed platform underwent characterization through diverse methods encompassing cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and density-functional theory. The capacitive interaction between yellow fever virus non-structural antigen and antibody gave a cathodic signal at approximately -260 mV, and increased in proportion to the amount of non-structural antibody. The created electrochemical biosensor has an ability to detect 96 ag/mL of the yellow fever non-structural antibody with an extensive analytical range varied from 0.1 fg/mL to 1 μg/mL. The interference effects of various substances that could be found in human plasma, and the performance of the method were examined from the point of recovery and relative standard deviation for human plasma samples; hereby, the results confirmed the unprecedented selectivity and accuracy of the proposed method.

Yellow Fever Emergence: Role of Heterologous Flavivirus Immunity in Preventing Urban Transmission

During major, recent yellow fever (YF) epidemics in Brazil, human cases were attributed only to spillover infections from sylvatic transmission with no evidence of human amplification. Furthermore, the historic absence of YF in Asia, despite abundant peridomestic Aedes aegypti and naive human populations, represents a longstanding enigma. We tested the hypothesis that immunity from dengue (DENV) and Zika (ZIKV) flaviviruses limits YF virus (YFV) viremia and transmission by Ae. aegypti . Prior DENV and ZIKV immunity consistently suppressed YFV viremia in experimentally infected macaques, leading to reductions in Ae. aegypti infection when mosquitoes were fed on infected animals. These results indicate that, in DENV- and ZIKV-endemic regions such as South America and Asia, flavivirus immunity suppresses YFV human amplification potential, reducing the risk of urban outbreaks.

One-Sentence Summary

Immunity from dengue and Zika viruses suppresses yellow fever viremia, preventing infection of mosquitoes and reducing the risk of epidemics.

Flaviviruses and the Traveler: Around the World and to Your Stage. A Review of West Nile, Yellow Fever, Dengue, and Zika Viruses for the Practicing Pathologist

Flaviviruses are a genus of single-stranded RNA viruses that impose an important and growing burden to human health. There are over 3 billion individuals living in areas where flaviviruses are endemic. Flaviviruses and their arthropod vectors (which include mosquitoes and ticks) take advantage of global travel to expand their distribution and cause severe disease in humans, and they can be grouped according to their vector and pathogenicity. The mosquito-borne flaviviruses cause a spectrum of diseases from encephalitis to hepatitis and vascular shock syndrome, congenital abnormalities, and fetal death. Neurotropic infections such as Zika virus and West Nile virus cross the blood-brain barrier and infect neurons and other cells, leading to meningoencephalitis. In the hemorrhagic fever clade, there are yellow fever virus, the prototypical hemorrhagic fever virus that infects hepatocytes, and dengue virus, which infects cells of the reticuloendothelial system and can lead to a dramatic plasma cell leakage and shock syndrome. Zika virus also causes congenital infections and fetal death and is the first and only example of a teratogenic arbovirus in humans. Diagnostic testing for flaviviruses broadly includes the detection of viral RNA in serum (particularly within the first 10 days of symptoms), viral isolation by cell culture (rarely performed due to complexity and biosafety concerns), and histopathologic evaluation with immunohistochemistry and molecular testing on formalin-fixed paraffin-embedded tissue blocks. This review focuses on 4 mosquito-borne flaviviruses-West Nile, yellow fever, dengue, and Zika virus-and discusses the mechanisms of transmission, the role of travel in geographic distribution and epidemic emergence, and the clinical and histopathologic features of each. Finally, prevention strategies such as vector control and vaccination are discussed.

Yellow Fever: Origin, Epidemiology, Preventive Strategies and Future Prospects

Yellow fever (YF) virus still represents a major threat in low resource countries in both South America and Africa despite the presence of an effective vaccine. YF outbreaks are not only due to insufficient vaccine coverage for insufficient vaccine supply, but also to the increase in people without history of vaccination living in endemic areas. Globalization, continuous population growth, urbanization associated with inadequate public health infrastructure, and climate changes constitute important promoting factors for the spread of this virus to tropical and subtropical areas in mosquito-infested regions capable of spreading the disease. In the present review, we focus on the origin of the virus and its transmission, representing two debated topics throughout the nineteenth century, going deeply into the history of YF vaccines until the development of the vaccine still used nowadays. Besides surveillance, we highlight the urgent need of routine immunization and vaccination campaigns associated to diverse and innovative mosquito control technologies in endemic areas for YF virus in order to minimize the risk of new YF outbreaks and the global burden of YF in the future.

Prior Heterologous Flavivirus Exposure Results in Reduced Pathogenesis in a Mouse Model of Zika Virus Infection

The 2015/2016 Zika virus epidemic in South and Central America left the scientific community urgently trying to understand the factors that contribute to Zika virus pathogenesis. Because multiple other flaviviruses are endemic in areas where Zika virus emerged, it is hypothesized that a key to understanding Zika virus disease severity is to study Zika virus infection in the context of prior flavivirus exposure. Human and animal studies have highlighted the idea that having been previously exposed to a different flavivirus may modulate the immune response to Zika virus. However, it is still unclear how prior flavivirus exposure impacts Zika viral burden and disease. In this murine study, we longitudinally examine multiple factors involved in Zika disease, linking viral burden with increased neurological disease severity, weight loss, and inflammation. We show that prior heterologous flavivirus exposure with dengue virus type 2 or 3 or the vaccine strain of yellow fever provides protection from mortality in a lethal Zika virus challenge. However, reduction in viral burden and Zika disease varies depending on the infecting primary flavivirus; with primary Zika virus infection being most protective from Zika virus challenge, followed by dengue virus 2, with yellow fever and dengue virus 3 protecting against mortality but showing more severe disease. This study demonstrates the variation in protective effects of prior flavivirus exposure on Zika virus pathogenesis and identifies distinct relationships between primary flavivirus infection and the potential for Zika virus disease.

IMPORTANCE The emergence and reemergence of various vector-borne diseases in recent years highlights the need to understand the mechanisms of protection for each pathogen. In this study, we investigated the impact of prior exposure to Zika virus, dengue virus serotypes 2 or 3, or the vaccine strain of yellow fever on pathogenesis and disease outcomes in a mouse model of Zika virus infection. We found that prior exposure to a heterologous flavivirus was protective from mortality, and to varying degrees, prior flavivirus exposure was protective against neurological disease, weight loss, and severe viral burden during a lethal Zika challenge. Using a longitudinal and cross-sectional study design, we were able to link multiple disease parameters, including viral burden, with neurological disease severity, weight loss, and inflammatory response in the context of flavivirus infection. This study demonstrates a measurable but varied impact of prior flavivirus exposure in modulating flavivirus pathophysiology. Given the cyclic nature of most flavivirus outbreaks, this work will contribute to the forecasting of disease severity for future outbreaks.

The electrochemical detection of bioterrorism agents: a review of the detection, diagnostics, and implementation of sensors in biosafety programs for Class A bioweapons

During the past year, disease has shown us the iron grip it can hold over a population of people. Health systems can be overwhelmed, economies can be brought into recession, and many people can be harmed or killed. When weaponized, diseases can be manipulated to create a detriment to health while becoming an economic burden on any society. It is consequently prudent that easy detection of bioweapons is available to governments for protecting their people. Electrochemical sensing displays many distinct advantages, such as its low limit of detection, low cost to run, rapid generation of results, and in many instances portability. We therefore present a wide array of electrochemical sensing platforms currently being fabricated, a brief summary of Class A bioweapons, and the potential future of bioweapon detection and biosafety.

Generation of a reporter yellow fever virus for high throughput antiviral assays

Yellow fever virus (YFV), a member of the Flaviviridae family, is an arthropod-borne virus that can cause severe disease in humans with a lethality rate of up to 60%. Since 2017, increases in YFV activity in areas of South America and Africa have been described. Although a vaccine is available, named strain 17D (Theiler and Smith, 1937), it is contraindicated for use in the elderly, expectant mothers, immunocompromised people, among others. To this day there is no antiviral treatment against YFV to reduce the severity of viral infection. Here, we used a circular polymerase extension reaction (CPER)-based reverse genetics approach to generate a full-length reporter virus (YFVhb) by introducing a small HiBit tag in the NS1 protein. The reporter virus replicates at a similar rate to the parental YFV in HuH-7 cells. Using YFVhb, we designed a high throughput antiviral screening luciferase-based assay to identify inhibitors that target any step of the viral replication cycle. We validated our assay by using a range of inhibitors including drugs, immune sera and neutralizing single chain variable fragments (scFv). In light of the recent upsurge in YFV and a potential spread of the virus, this assay is a further tool in the development of antiviral therapy against YFV.

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Bacteria-free approach to rescue yellow fever virus.

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Novel tagged yellow fever virus that permits quantifiable assays.

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Usage of the novel tagged virus for screening of antivirals and immune sera.

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Novel antiviral compounds against YFV were identified.

Sofosbuvir as a potential alternative to treat the SARS-CoV-2 epidemic

As of today, there is no antiviral for the treatment of the SARS-CoV-2 infection, and the development of a vaccine might take several months or even years. The structural superposition of the hepatitis C virus polymerase bound to sofosbuvir, a nucleoside analog antiviral approved for hepatitis C virus infections, with the SARS-CoV polymerase shows that the residues that bind to the drug are present in the latter. Moreover, a multiple alignment of several SARS-CoV-2, SARS and MERS-related coronaviruses polymerases shows that these residues are conserved in all these viruses, opening the possibility to use sofosbuvir against these highly infectious pathogens.

From Anonymous to Public Enemy: How Does a Mosquito Become a Feared Arbovirus Vector?

The past few decades have seen the emergence of several worldwide arbovirus epidemics (chikungunya, Zika), the expansion or recrudescence of historical arboviruses (dengue, yellow fever), and the modification of the distribution area of major vector mosquitoes such as Aedes aegypti and Ae. albopictus, raising questions about the risk of appearance of new vectors and new epidemics. In this opinion piece, we review the factors that led to the emergence of yellow fever in the Americas, define the conditions for a mosquito to become a vector, analyse the recent example of the new status of Aedes albopictus from neglected mosquito to major vector, and propose some scenarios for the future.