Huixia Li

Encephalomyocarditis virus (EMCV) infection causes viral encephalitis; however, the mechanisms underlying blood-brain barrier (BBB) disruption remain poorly understood. Here, we demonstrate that EMCV actively replicates in mouse brain tissue, induces robust neuroinflammation characterized by elevated proinflammatory cytokines and chemokines, and markedly increases BBB permeability as evidenced by Evans blue and sodium fluorescein extravasation. Importantly, tight junction (TJ) proteins ZO-1 and Occludin are selectively degraded at the post-transcriptional level, whereas Claudin-5 expression remains stable. Consistently, in vitro BBB models confirmed EMCV traversal, reduced transendothelial electrical resistance, and TJ disruption. Mechanistically, EMCV induces biphasic PI3K/AKT modulation and specifically downregulates AKT3. Notably, AKT3 knockdown exacerbates both autophagy and apoptosis, thereby accelerating ZO-1 and Occludin degradation while promoting viral replication. Furthermore, pharmacological inhibition of autophagy (chloroquine) or apoptosis (Z-VAD-FMK) effectively rescues TJ proteins and reduces viral load. Interestingly, the Caspase-8 inhibitor Z-IETD-FMK provides the most robust protection, implicating the extrinsic apoptotic pathway as the dominant route. Collectively, EMCV sequentially activates non-redundant AKT3-dependent autophagic and apoptotic pathways to degrade TJ proteins, ultimately enabling viral traversal across the compromised BBB and offering therapeutic targets for viral encephalitis.

Encephalomyocarditis virus (EMCV), a potential zoonotic pathogen with a broad host range, has been reported to enter cells via caveolin-mediated endocytosis (CavME), a process initiated by caveolae detachment from the plasma membrane. However, the molecular mechanism underlying EMCV’s cellular entry remains incompletely characterized. Here, we identified for the first time that the overexpression of Src kinase and Fyn kinase individually enhanced the replication and proliferation of EMCV. The treatment of specific small interfering RNA or inhibitors resulted in the downregulation of EMCV internalization, indicating the involvement of Src, Fyn, and Ezrin in the viral entry process. By treating different cell lines (BHK-21, hCMEC/D3, and PK15 cells) from various species with inhibitors of Src or Ezrin, as well as using siCav-1, and subsequently performing EMCV invasion experiments, we demonstrated the sequential activation of Src, Ezrin, and Cav-1 during EMCV internalization, indicating that this signaling pathway is widely present during EMCV infection of human-, hamster-, and pig-derived cells. Interestingly, the candidate receptor protein ICAM-1 interacts with Src and regulates its phosphorylation. Compared to the wild-type cells, lower levels of the phosphorylation of Src, Ezrin, and Cav-1 induced by EMCV were observed in ICAM-1 knockout BHK-21 cells. These findings indicate that EMCV entry into BHK-21 cells relies on the activation of the ICAM-1-Src-Ezrin-Cav-1 pathway. Our study first elucidates the molecular mechanism of EMCV invading into BHK-21 cells, providing potential targets for limiting EMCV infection and further refining the regulatory mechanism of the Src pathway on CavME. IMPORTANCE: EMCV has a wide host range and is a potential zoonotic pathogen, yet the mechanism of its entry into cells remains unclear. This study has found that the host proteins Src, Fyn, and Ezrin are involved in viral replication and proliferation, and their activity inhibitors hinder EMCV invasion into cells. With the participation of the cell surface adhesion factor ICAM-1, EMCV infects host cells by sequentially activating the phosphorylation of Src, Ezrin, and Cav-1, mediating the entry of EMCV into host cells through CavME. We have demonstrated for the first time the existence of an ICAM-1-Src-Ezrin-Cav-1 signaling pathway during EMCV entry into susceptible cells, which mediates the internalization process of the virus. Our research not only unravels the molecular mechanism of EMCV invasion, filling a gap in related research, but also provides a theoretical basis for the development of specific antiviral therapeutics.

Histone H1.2 is a member of the linker histone family, which plays extensive and crucial roles not only in the regulation of chromatin dynamics, cell cycle, and cell apoptosis, but also in viral diseases and innate immunity response. Recently, it was discovered that H1.2 regulates interferon-β and inhibits influenza virus replication, whereas its role in other viral infections is poorly reported. Here, we first found the up-regulation of H1.2 during Encephalomyocarditis virus (EMCV) infection, implying that H1.2 was involved in EMCV infection. Overexpression of H1.2 inhibited EMCV proliferation, whereas knockdown of H1.2 showed a significant promotion of virus infection in HEK293T cells. Moreover, we demonstrated that overexpression of H1.2 remarkably enhanced the production of EMCV-induced type I interferon, which may be the crucial factor for H1.2 proliferation–inhibitory effects. We further found that H1.2 up-regulated the expression of the proteins of the MDA5 signaling pathway and interacted with MDA5 and IRF3 in EMCV infection. Further, we demonstrated that H1.2 facilitated EMCV-induced phosphorylation and nuclear translocation of IRF3. Briefly, our research uncovers the mechanism of H1.2 negatively regulating EMCV replication and provides new insight into antiviral targets for EMCV.

Ghee is a traditional Tibetan dairy product with high-fat content, low yield, plasticity, caseation, and rich nutrition. In this study, we analyzed the diversity of microbial communities in yak milk and ghee samples at high and low altitudes, especially the Lactobacillus genus, and further used metabolomic techniques to compare the differences in metabolites in yak ghee at different altitudes. The results showed that the increase in altitude had a significant and generally inhibitory effect on the microbial community diversity in milk ghee, and yak milk at high altitude was abundant in nutrients, which could antagonize the negative impact of increased altitude. Using non-targeted metabolomics, we infer the composition of flavor compounds in ghee: nine kinds of carboxylic acids, 11 kinds of esters, six kinds of ketones, two kinds of alcohols, and four kinds of alkene compounds, among which the key flavor compounds are dl-2-(acetylamino)-3-phenylephrine acid, 1-(4-methoxyphenyl)-2-propanone, sebacic acid, Lysope 18:1, and uracil 1-beta-d-arabinofuranoside. These flavor substances are found in Lactococcus, Lactobacillus, and Streptococcus. With the participation of Lactobacillus, it is synthesized through biosynthesis of alkaloids derived from ornithine, lysine, and nicotine acid and glyoxylate and decarboxylate metabolism, among which Lactococcus plays a key role. In this study, a variety of lactic acid bacteria related to ghee fermentation were screened out, revealing the composition of volatile flavor compounds in Gannan yak milk ghee in the Qinghai–Tibet Plateau and providing a reference for further key volatile flavor compounds and the formation mechanism of flavor compounds.

Avian hepatitis E virus (HEV) infection is common in chicken flocks in China, as currently no measures exist to prevent the spread of the disease. In this study, we analyzed the effect of caged versus cage-free housing arrangements on avian HEV transmission. First, 127 serum and 110 clinical fecal samples were collected from 4 chicken flocks including the two arrangements in Shaanxi Province, China and tested for HEV antibodies and/or virus. Concurrently, 36 specific-pathogen-free chickens were divided equally into four experimental living arrangement groups, designated cage-free (Inoculated), caged (Inoculated), cage-free (Negative) and caged (Negative) groups. In caged groups, three cages contained 3 chickens each. Three chickens each from cage-free (Inoculated) and caged (Inoculated) groups (one chicken of each cage) were inoculated by cutaneous ulnar vein with the same dose of avian HEV, respectively. The cage-free (Negative) and caged (Negative) groups served as negative control. Serum and fecal samples were collected at 1 to 7 weeks post-inoculation (wpi) and liver lesions were scored at 7 wpi. The results of serology showed that the avian HEV infection rate (54.10%) of the cage-free chickens was significantly higher than the one (12.12%) for caged chickens (P < 0.05). Also, the rate of detection of avian HEV RNA in the clinical fecal samples was significantly higher in the cage-free (22.80%, 13/57) than caged birds (5.66%, 3/53). Moreover, under experimental conditions, the infected number of uninoculated cage-free chickens (6) was significantly higher than the one for the uninoculated caged birds (2), as evidenced by seroconversion, fecal virus shedding, viremia and gross and microscopic liver lesions. These results suggest that reduction of contact with feces as seen in the caged arrangement of housing chickens can reduce avian HEV transmission. This study provides insights for prevention and control of avian HEV infection in chicken flocks.

From 2014 to 2015 in China, many broiler breeder and layer hen flocks exhibited a decrease in egg production and some chickens developed hepatitis syndrome including hepatomegaly, hepatic necrosis and hemorrhage. Avian hepatitis E virus (HEV) and avian leucosis virus subgroup J (ALV-J) both cause decreasing in egg production, hepatomegaly and hepatic hemorrhage in broiler breeder and layer hens. In the study, the seroprevalence of avian HEV and ALV-J in these flocks emerging the disease from Shandong and Shaanxi provinces were investigated. A total of 1995 serum samples were collected from 14 flocks with hepatitis syndrome in Shandong and Shaanxi provinces, China. Antibodies against avian HEV and ALV-J in these serum samples were detected using iELISAs. The seroprevalence of anti-avian HEV antibodies (35.09%) was significantly higher than that of anti-ALV-J antibodies (2.16%) (p = 0.00). Moreover, the 43 serum samples positive for anti-ALV-J antibodies were all also positive for anti-avian HEV antibodies. In a comparison of both provinces, Shandong chickens exhibited a significantly higher seroprevalence of anti-avian HEV antibodies (42.16%) than Shaanxi chickens (26%) (p = 0.00). In addition, the detection of avian HEV RNA and ALV-J cDNA in the liver samples from the flocks of two provinces also showed the same results of the seroprevalence. In the present study, the results showed that avian HEV infection is widely prevalent and ALV-J infection is endemic in the flocks with hepatitis syndrome from Shandong and Shaanxi provinces of China. These results suggested that avian HEV infection may be the major cause of increased egg drop and hepatitis syndrome observed during the last 2 years in China. These results should be useful to guide development of prevention and control measures to control the diseases within chicken flocks in China.

Avian hepatitis E virus (HEV) is the main causative agent of big liver and spleen disease, as well as hepatitis-splenomegaly syndrome in chickens. To date, conventional reverse transcriptase polymerase chain reaction (RT-PCR) and nested RT-PCR methods have been used for the diagnosis of avian HEV infection in chickens. However, these assays are time consuming, inconvenient, and cannot detect the virus quantitatively. In this study, a rapid and sensitive SYBR Green real-time RT-PCR assay was developed to detect avian HEV RNA quantitatively in serum, liver, spleen, and fecal samples from chickens. Based on the sequence of the most conserved HEV gene, ORF3, the primers for the assay were designed, and the standard plasmid was constructed. The detection limit of the assay was shown to be 10 copies/μl of standard plasmid/reaction, with a corresponding cycle-threshold value of 29.3. The standard curve exhibited a dynamic linear range across at least 7 log units of DNA copy number. The specificity and reproducibility of this assay was high, showing that the assay detected avian HEV RNA specifically and with little variability. Compared to conventional RT-PCR, the current assay is more sensitive for detecting avian HEV in serum, liver, spleen, and fecal samples from chickens. A rapid, specific, and reproducible SYBR Green real-time RT-PCR assay was developed for the diagnosis of avian HEV infection in chickens. This assay can accurately detect avian HEV RNA in serum, liver, spleen, and fecal samples with more sensitivity than conventional RT-PCR.