Search

Background: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging zoonotic tick-borne disease in East Asia caused by the SFTS virus (SFTSV). It is to investigate the presence of SFTSV RNA and antibodies in horses from a slaughterhouse and equestrian centers in the Republic of Korea (ROK). A prevalence study of SFTSV-specific RNA and antibodies was designed from 889 horses in the ROK. Materials and Methods: Serum samples were collected from horses at a slaughterhouse and equestrian centers from 2018 to 2020. To detect the presence of SFTSV, RNA was extracted from the serum samples, and a nested reverse transcription-polymerase chain reaction (RT-PCR) was conducted. Sequencing data were analyzed, and a phylogenetic tree was constructed using the maximum-likelihood method with Molecular Evolutionary Genetics Analysis Version 7.0 software. The horse sera were also tested for SFTSV-specific immunoglobulin G antibodies using enzyme-linked immunosorbent assay (ELISA). Results: Twelve of 889 (1.3%) horse sera were positive for SFTSV RNA, and 452 of 887 (51.0%) horse sera were seropositive by ELISA. Among the RT-PCR-positive samples, 12 of the SFTSV S-segment sequences were classified as sub-genotypes B-2 (n = 6) and B-3 (n = 6). ELISA analysis was evaluated by comparison with neutralization test. We investigated SFTSV infection in horses over a 3-year period, but sampling was not performed evenly by season; continuous surveillance of SFTSV in horses is needed. Conclusions: We report the detection of SFTSV RNA and provide serological data on SFTSV prevalence in horses in the ROK. The detection of SFTSV-specific RNA and antibodies in horses, which are in close proximity to humans, suggests that SFTS is an emerging and important health issue, indicating that more attention to its relevance for equestrian workers is needed. [ABSTRACT FROM AUTHOR]

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne disease caused by SFTS virus (SFTSV) infection. Despite a gradual increase of SFTS cases and high mortality in endemic regions, no specific viral therapy nor vaccine is available. Here, we developed a single recombinant plasmid DNA encoding SFTSV genes, Gn and Gc together with NP-NS fusion antigen, as a vaccine candidate. The viral antigens were fused with Fms-like tyrosine kinase-3 ligand (Flt3L) and IL-12 gene was incorporated into the plasmid to enhance cell-mediated immunity. Vaccination with the DNA provides complete protection of IFNAR KO mice upon lethal SFTSV challenge, whereas immunization with a plasmid without IL-12 gene resulted in partial protection. Since we failed to detect antibodies against surface glycoproteins, Gn and Gc, in the immunized mice, antigen-specific cellular immunity, as confirmed by enhanced antigen-specific T cell responses, might play major role in protection. Finally, we evaluated the degree of protective immunity provided by protein immunization of the individual glycoprotein, Gn or Gc. Although both protein antigens induced a significant level of neutralizing activity against SFTSV, Gn vaccination resulted in relatively higher neutralizing activity and better protection than Gc vaccination. However, both antigens failed to provide complete protection. Given that DNA vaccines have failed to induce sufficient immunogenicity in human trials when compared to protein vaccines, optimal combinations of DNA and protein elements, proper selection of target antigens, and incorporation of efficient adjuvant, need to be further investigated for SFTSV vaccine development. Author summary: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infection endemic to East Asia including China, Korea, and Japan. Gradual rise of disease incidence and relatively high mortality have become a serious public health problem in the endemic countries. In this study, we developed a recombinant plasmid DNA encoding four antigens, Gn, Gc, NP, and NS, of SFTS virus (SFTSV) as a vaccine candidate. In order to enhance cell-mediated immunity, the viral antigens were fused with Flt3L and IL-12 gene was incorporated into the plasmid. Immunization with the DNA vaccine provides complete protection against lethal SFTSV infection in IFNAR KO mice. Antigen-specific T cell responses might play a major role in the protection since we observed enhanced T cell responses specific to the viral antigens but failed to detect neutralizing antibody in the immunized mice. When we immunized with either viral glycoprotein, Gn protein induced relatively higher neutralizing activity and better protection against SFTSV infection than Gc antigen, but neither generated complete protection. Therefore, an optimal combination of DNA and protein elements, as well as proper selection of target antigens, might be required to produce an effective SFTSV vaccine. [ABSTRACT FROM AUTHOR]

The widespread aeolian deposits on the Chinese Loess Plateau (CLP) have been investigated intensively as an outstanding archive of information on past variations of the East Asian Monsoon (EAM). However, differentiating the impacts of precipitation and temperature on loess-based proxies is difficult and complex, which hampers our ability to understand the variability and dynamics of the EAM. In this study, we investigated the Mg isotope composition (δ26Mg) of the secondary carbonates in fine-grained loess samples from ten Holocene profiles and a loess-paleosol sequence, as well as in the primary carbonates of nine loess-source samples from the Asian inland deserts. Our aim was to explore the potential of the δ26Mg values of secondary carbonates in tracing precipitation changes. The results demonstrate that δ26Mg values are homogeneous (−2.07‰) in primary carbonates from different loess-sources, but display large variations in secondary carbonates of loess, increasing from −3.33‰ in the northwest CLP to −1.80‰ in the southeast CLP, and from −3.58‰ during the last glacial to −1.65‰ during the last interglacial. The variations were mainly controlled by EAM precipitation via the migration of isotopically light Mg, because Mg isotope fractionation during the formation of secondary carbonates is temperature insensitive, and the primary carbonate in different loess-sources has relatively constant δ26Mg values. This conclusion is further supported by high correlation (r 2 = 0.84) between modern mean annual precipitation (MAP) and δ26Mg in the secondary carbonates of spatial loess samples. Based on this δ26Mg-MAP relationship, temporal variations in MAP were quantitatively estimated, ranging from 670 mm during the last interglacial to 270 mm during the last glacial at the southern CLP. Compared with previous estimates, our MAP exhibits a larger amplitude of glacial-interglacial fluctuations (∼400 mm) with a less uncertainty (53–76 mm), implying that δ26Mg values in secondary carbonates of loess can serve as a novel precipitation proxy to infer EAM variability and dynamics. [ABSTRACT FROM AUTHOR]