An orbivirus designated Yunnan orbivirus (YUOV) was isolated from Culex tritaeniorhynchus mosquitoes collected in the Yunnan province of China. Electron microscopy showed particles with typical orbivirus morphology. The YUOV genome was sequenced completely and compared with previously characterized orbivirus genomes. Significant identity scores were detected between proteins encoded by the segments (Seg-1 to Seg-10) of YUOV and those encoded by their homologues in insect-borne and tick-borne orbiviruses. Analysis of VP1 (Pol) and VP2 (T2, which correlates with the virus serogroup) indicated that YUOV is a new species of the genus Orbivirus that is unrelated to the other insect-borne orbiviruses. The replication of YUOV in mosquito cell lines was restricted to Aedes albopictus cells and the virus failed to replicate in mammalian cell lines. However, intraperitoneal injection of virus into naïve mice resulted in productive, non-lethal virus replication and viraemia. Infected mice developed serum neutralizing antibodies and were protected against a new infection challenge. Sequence analysis of clones from the segments encoding outer coat proteins (Seg-3 and Seg-6) of YUOV recovered from mouse blood did not show significant changes in the sequences. The availability of the complete genome sequence will facilitate the development of sequence-specific PCR assays for the study of YUOV epidemiology in the field.
Seadornaviruses are emerging arboviral pathogens from the south-east of Asia. The genus Seadornavirus contains two distinct species, Banna virus (BAV) isolated from humans with encephalitis and Kadipiro virus. BAV replicates within insect cells and mice but not in cultured mammalian cells. Here, the discovery of Liao ning virus (LNV), a new seadornavirus from the Aedes dorsalis mosquito, which was completely sequenced and was found to be related to BAV and Kadipiro virus, is reported. Two serotypes of LNV could be distinguished by a serum neutralization assay. According to amino acid identity with other seadornaviruses, and to criteria set by the ICTV for species delineation, LNV was identified as a member of a new species of virus. Its morphology was characterized by electron microscopy and found to be similar to that of BAV. LNV is the first reported seadornavirus that replicates in mammalian cells, leading to massive cytopathic effect in all transformed or embryonic cell lines tested. LNV-and BAV-infected mice producing a viraemia lasting for 5 days was followed by viral clearance. Mice infection generated virus quasi-species for LNV (the first reported observation for quasi-species in the family Reoviridae) but not for BAV. Challenge with BAV in mice immunized against BAV did not lead to productive infection. However, challenge with LNV in mice immunized against LNV was lethal with a new phase of viraemia and massive haemorrhage.
Infection with alphaviruses is common in the Chinese population. Here we report the isolation of a Sindbis-like virus from a pool of Anopheles mosquitoes collected in Xinjiang, China during an arbovirus survey. This virus, designated XJ-160, rapidly produced cytopathic effects on mosquito and hamster cells. In addition, it was lethal to neonatal mice if inoculated intracerebrally. Serologically, XJ-160 reacted with and was neutralized by an anti-Sindbis antibody. Anti-XJ-160 antibodies were found in several cohorts of Chinese subjects. The complete 11626-base nucleotide sequence of XJ-160 was determined. XJ-160 has diverged significantly from the prototype Sindbis virus, with an 18 % difference in nucleotide sequence and an 8n6 % difference in amino acids ; there are 11 deletions and 2 insertions, involving 99 nucleotides in total. XJ-160 is most closely linked to Kyzylagach virus isolated in Azerbaijan. Both belong to the African/European genetic lineage of Sindbis virus, albeit more distantly related to other members.
Previous studies have found that the elemental abundances of a star correlate directly with its age and metallicity. Using this knowledge, we derive ages for nearly 250,000 stars of the GALAH DR3 sample using only their overall metallicity and chemical abundances. Stellar ages are estimated via the machine learning algorithm XGBoost, using main sequence turnoff stars with precise ages as our input training set. We find that the stellar ages for the bulk of the GALAH DR3 sample are accurate to 1-2 Gyr using this method. With these ages, we replicate many recent results on the age-kinematic trends of the nearby disk, including the age-velocity dispersion relationship of the solar neighborhood and the larger global velocity dispersion relations of the disk found using Gaia and GALAH. The fact that chemical abundances alone can be used to determine a reliable age for a star have profound implications for the future study of the Galaxy as well as upcoming spectroscopic surveys. These results show that the chemical abundance variation at a given birth radius is quite small, and imply that strong chemical tagging of stars directly to birth clusters may prove difficult with our current elemental abundance precision. Our results highlight the need of spectroscopic surveys to deliver precision abundances for as many nucleosynthetic production sites as possible in order to estimate reliable ages for stars directly from their chemical abundances. Applying the methods outlined in this paper opens a new door into studies of the kinematic structure and evolution of the disk, as ages may potentially be estimated for a large fraction of stars in existing spectroscopic surveys. This would yield a sample of millions of stars with reliable age determinations, and allow precise constraints to be put on various kinematic processes in the disk, such as the efficiency and timescales of radial migration.
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