Molecular Characterization of a Hamster Viscerotropic Strain of Yellow Fever Virus

Globally, yellow fever virus infects nearly 200,000 people, leading to 30,000 deaths annually. Although the virus is endemic to Latin America, only a single genome from this region has been sequenced. Here, we report 12 Brazilian yellow fever virus complete genomes, their genetic traits, phylogenetic characterization, and phylogeographic dynamics. Variable 3′ noncoding region (3′NCR) patterns and specific mutations throughout the open reading frame altered predicted secondary structures. Our findings suggest that whereas the introduction of yellow fever virus in Brazil led to genotype I-predominant dispersal throughout South and Central Americas, genotype II remained confined to Bolivia, Peru, and the western Brazilian Amazon.

Section: Resultsmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Genomic and Phylogenetic Characterization of Brazilian Yellow Fever Virus Strains

Nunes

Palacios

Cardoso

et al. 2012

“…In contrast, direct CNS infection of most YFV strains in mice is lethal (2). This obstacle can be overcome with the use of viscerotropic strains of YFV in hamsters (24,38) or of immunodeficient (e.g., scid) mice with increased sensitivity to YFV by peripheral routes of infection (6). We show in this study that type I and II interferons are crucial in restricting viral replication in the mouse visceral organs, hence adult IFN-␣/␥-R Ϫ/Ϫ mice are uniformly FIG.…”

Section: Discussionmentioning

confidence: 99%

E Protein Domain III Determinants of Yellow Fever Virus 17D Vaccine Strain Enhance Binding to Glycosaminoglycans, Impede Virus Spread, and Attenuate Virulence

Lee

Lobigs

2008

The yellow fever virus (YFV) 17D strain is one of the most effective live vaccines for human use, but the in vivo mechanisms for virulence attenuation of the vaccine and the corresponding molecular determinants remain elusive. The vaccine differs phenotypically from wild-type YFV by the loss of viscerotropism, despite replicative fitness in cell culture, and genetically by 20 amino acid changes predominantly located in the envelope (E) protein. We show that three residues in E protein domain III inhibit spread of 17D in extraneural tissues and attenuate virulence in type I/II interferon-deficient mice. One of these residues (Arg380) is a dominant glycosaminoglycan-binding determinant, which mainly accounts for more rapid in vivo clearance of 17D from the bloodstream in comparison to 17D-derived variants with wild-type-like E protein. While other mutations will account for loss of neurotropism and phenotypic stability, the described impact of E protein domain III changes on virus dissemination and virulence is the first rational explanation for the safety of the 17D vaccine in humans.The live, attenuated yellow fever virus (YFV) strain 17D vaccine has been used safely and effectively in over 500 million individuals over the past 70 years. This excellent safety record also underpins its potential application as a platform for chimeric vaccines against other medically important flaviviruses (dengue, Japanese encephalitis, and West Nile viruses), which are currently in clinical trials (reviewed in reference 13). Despite knowledge of the complete genome sequences of 17D (33) and its virulent parent (10), the Asibi strain isolated in Africa in 1927, the in vivo mechanism(s) and molecular determinants for virulence attenuation of the YFV vaccine are still not completely resolved. YFV strain 17D was the first human vaccine derived from repeated passage in tissue culture (reviewed in reference 39). More than 230 passages in embryonic mouse tissue (18 passages), chicken embryo tissue (50 passages), and chicken embryo tissue from which the head and spinal chord had been removed (152 passages) separate the 17D from the Asibi strain. The adaptation of 17D to growth in mouse and chicken embryonal tissues culture has resulted in loss of viscerotropism, a property which accounts for the major disease manifestations of yellow fever in primates: high viremia, hepatitis, renal dysfunction, hemorrhagic fever, and circulatory shock (reviewed in reference 28); it also resulted in reduced neurotropism and loss of tropism for mosquitoes, the obligatory vector in the natural transmission cycle of YFV. The complex passage history of YFV strain 17D has given rise to as many as 68 nucleotide mutations and 32 amino acid changes in the viral RNA genome (10). However, when the Asibi genome is compared to the consensus sequence of different 17D vaccine strains derived from it, the number of differences potentially contributing to the attenuated virulence phenotype can be reduced to 20 amino acids and 4 nucleotides in the 3Ј untranslated region...

“…Previous studies have shown that sequential series of liverto-liver passages of YFVs in hamsters led to the generation of viral strains that cause a more lethal disease in hamsters (21,33,39). Instead of serial passaging, we performed alternate passaging of DEN between mosquito cells and mice to obtain D2S10, thereby approximating the natural transmission cycle of DEN between mosquitoes and humans.…”

Section: Discussionmentioning

confidence: 99%

Murine Model for Dengue Virus-Induced Lethal Disease with IncreasedVascular Permeability

Shresta

Sharar

Prigozhin

et al. 2006

319

429

Lack of an appropriate animal model for dengue virus (DEN), which causes dengue fever and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), has impeded characterization of the mechanisms underlying the disease pathogenesis. The cardinal feature of DHF/DSS, the severe form of DEN infection, is increased vascular permeability. To develop a murine model that is more relevant to DHF/DSS, a novel DEN strain, D2S10, was generated by alternately passaging a non-mouse-adapted DEN strain between mosquito cells and mice, thereby mimicking the natural transmission cycle of the virus between mosquitoes and humans. After infection with D2S10, mice lacking interferon receptors died early without manifesting signs of paralysis, carried infectious virus in both non-neuronal and neuronal tissues, and exhibited signs of increased vascular permeability. In contrast, mice infected with the parental DEN strain developed paralysis at late times after infection, contained detectable levels of virus only in the central nervous system, and displayed normal vascular permeability. In the mice infected with D2S10, but not the parental DEN strain, significant levels of serum tumor necrosis factor alpha (TNF-␣) were produced, and the neutralization of TNF-␣ activity prevented early death of D2S10-infected mice. Sequence analysis comparing D2S10 to its parental strain implicated a conserved region of amino acid residues in the envelope protein as a possible source for the D2S10 phenotype. These results demonstrate that D2S10 causes a more relevant disease in mice and that TNF-␣ may be one of several key mediators of severe DEN-induced disease in mice. This report represents a significant advance in animal models for severe DEN disease, and it begins to provide mechanistic insights into DEN-induced disease in vivo.Dengue virus (DEN) causes dengue fever (DF) and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), with an estimated 2.5 billion people at risk for infection in subtropical and tropical regions of the world (6). DEN is a positivesense, single-stranded RNA virus that belongs to the family Flaviviridae and the genus Flavivirus, which includes yellow fever (YFV), West Nile, Japanese encephalitis, and St. Louis encephalitis viruses. Primary infection with any one of the four DEN serotypes typically leads to DF, a debilitating but selflimited acute febrile illness. However, some primary infections and a larger percentage of secondary infections with a different serotype result in the severe, life-threatening DHF/DSS, characterized by increased vascular permeability and hemorrhagic manifestations (6). Despite its name, bleeding manifestations are minor and major hemorrhages are unusual; instead, increased vascular permeability is the hallmark of DHF/DSS. In rare cases of DHF/DSS, neurologic abnormalities, including encephalitis, may also occur (32). DEN is transmitted to humans by the mosquitoes Aedes aegypti and Aedes albopictus. Due to uncontrolled urbanization, globalization, and dissemination of DEN-transmitting mosquito...