Neonatal mouse model reveals pathogenesis of Shanxi Tick Virus 2 isolated from Haemaphysalis longicornis

Abstract

Shanxi Tick Virus 2(SXTV2), a Tamdy group member of Orthonairovirus genus, Nairoviridae family, was initially identified through Next Generation Sequencing, with its pathogenicity and risk profile remaining unclear. This study reports the first successful isolation of SXTV2 from Haemaphysalis longicornis ticks collected from Hunchun City, China-a tri-border region between China, Russia, and North Korea. The isolated SXTV2 strain replicated and produced cytopathic effects in both Vero (primate) and SW-13 (human) cell lines. Electron microscopy revealed that SXTV2 particles are enveloped, surface-spiked, pleomorphic, and approximately 100 nm in diameter. Experimental inoculation in neonatal mice led to significant weight loss, liver injury and 100% mortality. In conclusion, this study marks the first successful isolation of the SXTV2 strain and exploring the animal model for member of Tamdy group orthonairovirus. These findings suggest the need for enhanced surveillance of SXTV2 zoonotic exposure and disease epidemic risks.

Keywords: First isolation; Neonatal mouse lethality; Orthonairovirus; Shanxi Tick Virus 2.

Fig. 1

Characteristics of Shanxi Tick Virus 2 (SXTV2) in cell lines. A Cytopathic effects observed in Vero and SW-13 cells at 8 day post-inoculation with the C4 passage YB_tick_2023_236 strain. B Quantitative analysis of viral RNA levels in Vero and SW-13 cells supernatant from 24 to 96 h post-inoculation with the C4 passage YB_tick_2023_236 strain, indicating viral replication. C Ultrastructural features of SXTV2 particles as observed via transmission electron microscopy. Arrows indicate virus particles. Scale bars: 100 nm

Fig. 2

Similarity of the YB_tick_2023_236 strain of SXTV2 with other orthonairoviruses. Phylogenetic tree constructed using the neighbor-joining method, showing the genetic relationship of YB_tick_2023_236 strain with other members of the Orthonairovirus genus within the Nairoviridae family (A) and other L segment of SXTV2 strains (B). C Comparison of the nucleotide and amino acid sequence identities between the YB_tick_2023_236 strain and other orthonairoviruses. D Sequence alignment of the OTUs from CCHFV (3PRP), SXTV2, SGLV (HLJ1202), and XCV (MDJ311). E Sequence alignment of the GP38s from CCHFV (6VKF), SXTV2, SGLV (HLJ1202), and XCV (MDJ311). The secondary structure displayed above the alignments is based on that of CCHFV. The structures of the specified proteins from CCHFV and SXTV2 are shown on the right. SXTV2, Shanxi Tick Virus 2; ATV, Antu virus; SGLV, Songling virus; WTV, Wenzhou tick virus; TAMV, Tamdy virus; TcTV-1, Tǎchéng tick virus-1; BURV, Burana virus; HTV, Huangpi tick virus; CCHFV, Crimean-Congo hemorrhagic fever virus

Fig. 3

SXTV2 infection in BALB/c mouse model. A Male 3–4 week-old BALB/c mice (n = 8) were inoculated intraperitoneally with 10³–10⁵ FFU of SXTV2. B Neonatal BALB/c mice (n = 5) were inoculated intracranially with 10³–10⁵ FFU of SXTV2. C Blood biochemistry tests and quantification of 6dpi and 9dpi of SXTV2 infection (n = 4). Alanine transaminase (ALT), aspartate transaminase (AST), γ-glutamyltransferase(γ-GT), glucose (Glu), low-density lipoprotein (LDL), total bilirubin (T-Bil) values in serum were displayed with the mean values and standard errors

Fig. 4

Viral RNA in different organ of SXTV2-infected neonatal BALB/c. Lungs, livers, spleens, kidneys, intestines, brains, stomachs and hearts of SXTV2-inoculated neonatal BALB/c collected at 3, 6 and 9 dpi were used for analyzing

Fig. 5

Histopathological Analysis of Tissues from SXTV2-infected neonatal BALB/c by HE Staining. A Brain. B Liver. C Kidney. D Intestine. Upper panels depict low-magnification views (scale bar = 500 µm), while lower panels show corresponding high-magnification views (scale bar = 50 µm)