1. Determinants of attenuation in the envelope protein of the flavivirus Alfuy.
- Author
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Prow NA, May FJ, Westlake DJ, Hurrelbrink RJ, Biron RM, Leung JY, McMinn PC, Clark DC, Mackenzie JS, Lobigs M, Khromykh AA, and Hall RA
- Subjects
- Animals, Disease Models, Animal, Encephalitis, Viral mortality, Encephalitis, Viral pathology, Encephalitis, Viral virology, Flavivirus Infections mortality, Flavivirus Infections pathology, Flavivirus Infections virology, Glycosylation, Lethal Dose 50, Mice, Recombination, Genetic, Rodent Diseases mortality, Rodent Diseases pathology, Rodent Diseases virology, Survival Analysis, Virulence, Flavivirus genetics, Flavivirus pathogenicity, Viral Envelope Proteins genetics, Viral Envelope Proteins metabolism, Virulence Factors genetics, Virulence Factors metabolism
- Abstract
Murray Valley encephalitis virus (MVEV) is a mosquito-borne flavivirus endemic to Australia and Papua New Guinea. Most strains of MVEV cause potentially fatal cases of encephalitis in humans and horses, and have been shown to be highly neuroinvasive in weanling mice. In contrast, the naturally occurring subtype Alfuy virus (ALFV) has never been associated with human disease, nor is it neuroinvasive in weanling mice, even at high doses. To identify viral factors associated with ALFV attenuation, a chimeric infectious clone was constructed containing the structural genes premembrane (prM) and envelope (E) of ALFV swapped into the MVEV genome. The resulting virus (vMVEV/ALFVstr) was no longer neuroinvasive in mice, suggesting that motifs within prM-E of ALFV confer attenuation. To define these motifs further, mutants were constructed by targeting divergent sequences between the MVEV and ALFV E proteins that are known markers of virulence in other encephalitic flaviviruses. MVEV mutants containing a unique ALFV sequence in the flexible hinge region (residues 273-277) or lacking the conserved glycosylation site at position 154 were significantly less neuroinvasive in mice than wild-type MVEV, as determined by delayed time to death or increased LD(50). Conversely, when the corresponding MVEV sequences were inserted into the vMVEV/ALFVstr chimera, the mutant containing the MVEV hinge sequence was more neuroinvasive than the parental chimera, though not to the same level as wild-type MVEV. These results identify the hinge region and E protein glycosylation as motifs that contribute to the attenuation of ALFV.
- Published
- 2011
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