Preoperative increased pronation angle of the first metatarsus associated with correction loss after hallux valgus surgery: A semi-weight-bearing computed tomography study.

BACKGROUND: The effect of preoperative first metatarsal pronation on postoperative prognosis of hallux valgus (HV) surgery is under investigation. Utilizing semi-weight-bearing computed tomography, the preoperative pronation angle was assessed to quantify its impact on postoperative prognosis. METHODS: In a retrospective analysis of 31 feet, those with re-increased hallux valgus angle postoperatively were classified as the non-maintained group, and the remainder as the maintained group. Preoperative pronation angles were compared to establish a threshold. Subsequently, feet were re-classified into high or low-pronation categories. The relative risk of non-maintenance in high-pronation category was calculated. RESULTS: The non-maintained group exhibited a significantly higher preoperative pronation angle (p = 0.021), with a 28.4º threshold. The high-pronation category had a relative risk of 2.34 for non-maintenance. CONCLUSIONS: Increased preoperative first metatarsal pronation angle is associated with correction loss after HV surgery. Utilizing sWBCT to measure the pronation angle provides valuable insights into postoperative prognosis. LEVEL OF EVIDENCE: III.

SFTSV Gn-Head mRNA vaccine confers efficient protection against lethal viral challenge.

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne virus, causing thrombocytopenia and hemorrhagic fever, with a fatality rate ranging from 12% to 30%. SFTSV possesses Gn and Gc glycoproteins, which are responsible for host cell receptor attachment and membrane fusion, respectively, to infect host cells. We have previously reported a protein subunit vaccine candidate (sGn-H-FT) of the SFTSV soluble Gn head region (sGn-H) fused with self-assembling ferritin (FT) nanoparticles, displaying strong protective immunogenicity. In this study, we present messenger RNA (mRNA) vaccine candidates encoding sGn-H or sGn-H-FT, both of which exhibit potent in vivo immunogenicity and protection capacity. Mice immunized with either sGn-H or sGn-H-FT mRNA lipid nanoparticle (LNP) vaccine produced strong total antibodies and neutralizing antibodies (NAbs) against sGn-H. Importantly, NAb titers remained high for an extended period. Finally, mice immunized with sGn-H or sGn-H-FT mRNA LNP vaccine were fully protected from a lethal dose of SFTSV challenge, showing no fatality. These findings underscore the promise of sGn-H and sGn-H-FT as vaccine antigen candidates capable of providing protective immunity against SFTSV infection.

Self-assembling Gn head ferritin nanoparticle vaccine provides full protection from lethal challenge of Dabie bandavirus in aged ferrets.

IMPORTANCE: Dabie bandavirus (DBV) is an emerging tick-borne virus that causes severe fever with thrombocytopenia syndrome (SFTS) in infected patients. Human SFTS symptoms progress from fever, fatigue, and muscle pain to the depletion of white blood cells and platelets with fatality rates up to 30%. The recent spread of its vector tick to over 20 states in the United States increases the potential for outbreaks of the SFTS beyond the East Asia. Thus, the development of vaccine to control this rapidly emerging virus is a high priority. In this study, we applied self-assembling ferritin (FT) nanoparticle to enhance the immunogenicity of DBV Gn head domain (GnH) as a vaccine target. Mice immunized with the GnH-FT nanoparticle vaccine induced potent antibody responses and cellular immunity. Immunized aged ferrets were fully protected from the lethal challenge of DBV. Our study describes the GnH-FT nanoparticle vaccine candidate that provides protective immunity against the emerging DBV infection.

Self-assembling Gn head ferritin nanoparticle vaccine provides full protection from lethal challenge of Dabie Bandavirus in aged ferrets.

Dabie Bandavirus (DBV), previously known as Severe Fever with Thrombocytopenia Syndrome (SFTS) Virus, induces a characteristic thrombocytopenia with a mortality rate ranging from 12% to as high as 30%. The sero-prevalence of DBV in healthy people is not significantly different among age groups, but clinically diagnosed SFTS patients are older than ~50 years, suggesting that age is the critical risk factor for SFTS morbidity and mortality. Accordingly, our immune-competent ferret model demonstrates an age (>4 years old)-dependent DBV infection and pathogenesis that fully recapitulates human clinical manifestation. To protect the aged population from DBV-induced SFTS, vaccine should carry robust immunogenicity with high safety profile. Previous studies have shown that glycoproteins Gn/Gc are the most effective antigens for inducing both neutralizing antibody (NAb)- and T cell-mediated immunity and, thereby, protection. Here, we report the development of a protein subunit vaccine with 24-mer self-assembling ferritin (FT) nanoparticle to present DBV Gn head region (GnH) for enhanced immunogenicity. Anion exchange chromatography and size exclusion chromatography readily purified the GnH-FT nanoparticles to homogeneity with structural integrity. Mice immunized with GnH-FT nanoparticles induced robust NAb response and T-cell immunity against DBV Gn. Furthermore, aged ferrets immunized with GnH-FT nanoparticles were fully protected from DBV challenge without SFTS symptoms such as body weight loss, thrombocytopenia, leukopenia, and fatality. This study demonstrates that DBV GnH-FT nanoparticles provide an efficient vaccine efficacy in mouse and aged ferret models and should be an outstanding vaccine candidate targeted for the aged population against fatal DBV infection.

Lung-specific MCEMP1 functions as an adaptor for KIT to promote SCF-mediated mast cell proliferation.

Lung mast cells are important in host defense, and excessive proliferation or activation of these cells can cause chronic inflammatory disorders like asthma. Two parallel pathways induced by KIT-stem cell factor (SCF) and FcεRI-immunoglobulin E interactions are critical for the proliferation and activation of mast cells, respectively. Here, we report that mast cell-expressed membrane protein1 (MCEMP1), a lung-specific surface protein, functions as an adaptor for KIT, which promotes SCF-mediated mast cell proliferation. MCEMP1 elicits intracellular signaling through its cytoplasmic immunoreceptor tyrosine-based activation motif and forms a complex with KIT to enhance its autophosphorylation and activation. Consequently, MCEMP1 deficiency impairs SCF-induced peritoneal mast cell proliferation in vitro and lung mast cell expansion in vivo. Mcemp1-deficient mice exhibit reduced airway inflammation and lung impairment in chronic asthma mouse models. This study shows lung-specific MCEMP1 as an adaptor for KIT to facilitate SCF-mediated mast cell proliferation.

Association of general and central obesity, and their changes with risk of knee osteoarthritis: a nationwide population-based cohort study.

In this study, we aimed to evaluate the association between general and central obesity, and their changes with risk of knee osteoarthritis (OA) using retrospective cohort data collected from the Korean National Health Insurance Service. We studied 1,139,463 people aged 50 and over who received a health examination in 2009. To evaluate the association between general and/or central obesity and knee OA risk, a Cox proportional hazard models were used. Additionally, we investigate knee OA risk according to the change in obesity status over 2 years for subjects who had undergone health examinations for 2 consecutive years. General obesity without central obesity (HR 1.281, 95% CI 1.270-1.292) and central obesity without general obesity (HR 1.167, 95% CI 1.150-1.184) were associated with increased knee OA risk than the comparison group. Individuals with both general with central obesity had the highest risk (HR 1.418, 95% CI 1.406-1.429). This association was more pronounced in women and younger age group. Remarkably, the remission of general or central obesity over two years was associated with decreased knee OA risk (HR 0.884; 95% CI 0.867-0.902; HR 0.900; 95% CI 0.884-0.916, respectively). The present study found that both general and central obesity were associated with increased risk of knee OA and the risk was highest when the two types of obesity were accompanied. Changes in obesity status have been confirmed to alter the risk of knee OA.

Simple curettage and allogeneic cancellous bone chip impaction grafting in solitary enchondroma of the short tubular bones of the hand.

Enchondroma is the most common bone tumor in the hand. While standard surgical procedure is intra-lesional excision and bone grafting, there is a dispute between allogeneic bone, autogenous bone, and synthetic bone substitute grafting. Diverse adjuvant treatments have been introduced to reduce recurrence, but results are mixed with controversies. Meanwhile, whether existing descriptive classification could predict treatment outcome remains unclear. Thus, we reviewed patients with solitary enchondroma of the hand who underwent simple curettage followed by allogeneic cancellous bone chip impaction grafting. Eighty-eight patients with more than 5 years of follow-up were enrolled. Demographic data, local recurrence, and complications were reviewed. Duration of consolidation and the difference according to Takigawa classification were assessed. Range of motion (ROM), and functional scores were also evaluated. There were 51 women and 37 men, with a mean age of 37.9 years. Mean follow-up was 10.2 years. Recurrence occurred only in one patient. There was no complication. Mean postoperative total active motions of fingers and thumb were 239° and 132.9°. Mean modified Disabilities of the Arm, Shoulder, Hand score, and Musculoskeletal Tumor Society Score were 1.63, and 99.2 at the last follow-up. Consolidation, ROM, and functional scores according to Takigawa classification showed no significant differences. This study suggests that simple curettage with impaction grafting of allogeneic cancellous bone chip is a feasible method for treating solitary enchondromas involving short tubular bone of the hand with good long-term outcomes. Postoperative recurrence and complication rates were very low. Radiographic and clinical results were good regardless of the previous radiological classification.

Association between knee osteoarthritis and the risk of cardiovascular disease and the synergistic adverse effects of lack of exercise.

We aimed to determine whether knee OA is associated with CVD risk and all-cause death and to evaluate whether the association differs by exercise behavior. We used Korea National Health Insurance Service (KNHIS) database and included 201,466 participants (7572 subjects diagnosed with knee OA) who underwent health screening between 2009 and 2015. Those who had been diagnosed with knee OA or CVD before the index year were excluded. Cox proportional hazard models were used after adjusting for sociodemographic and CVD risk factors to evaluate the association between knee OA and CVD risk and all-cause death. Stratification analysis was further performed to determine the effect of exercise behavior on this relationship. During a median follow-up of 7.06 ± 2.24 years, 8743 CVD (2510 MI and 6553 stroke) cases developed. Individuals with knee OA had increased risks of CVD [hazard ratio (HR) 1.26, 95% confidence interval (CI) 1.15-1.38], myocardial infarction (MI) (HR 1.20, 95% CI 1.00-1.44), and stroke (HR 1.29, 95% CI 1.16-1.43) compared with those without knee OA. Those with knee OA who did not exercise had an increased risk of CVD (HR 1.25, 95% CI 1.11-1.40), whereas no significant increased CVD risk was observed in those with knee OA who exercised at least once a week (HR 1.11, 95% CI 0.96-1.28). There was no association between knee osteoarthritis and all-cause death. Knee OA was independently associated with an increased risk of CVD. Lack of exercise might have a synergistic adverse effect on the association between knee OA and CVD.

Monocular Depth Estimation Using a Laplacian Image Pyramid with Local Planar Guidance Layers.

It is important to estimate the exact depth from 2D images, and many studies have been conducted for a long period of time to solve depth estimation problems. Recently, as research on estimating depth from monocular camera images based on deep learning is progressing, research for estimating accurate depths using various techniques is being conducted. However, depth estimation from 2D images has been a problem in predicting the boundary between objects. In this paper, we aim to predict sophisticated depths by emphasizing the precise boundaries between objects. We propose a depth estimation network with encoder-decoder structures using the Laplacian pyramid and local planar guidance method. In the process of upsampling the learned features using the encoder, the purpose of this step is to obtain a clearer depth map by guiding a more sophisticated boundary of an object using the Laplacian pyramid and local planar guidance techniques. We train and test our models with KITTI and NYU Depth V2 datasets. The proposed network constructs a DNN using only convolution and uses the ConvNext networks as a backbone. A trained model shows the performance of the absolute relative error (Abs_rel) 0.054 and root mean square error (RMSE) 2.252 based on the KITTI dataset and absolute relative error (Abs_rel) 0.102 and root mean square error 0.355 based on the NYU Depth V2 dataset. On the state-of-the-art monocular depth estimation, our network performance shows the fifth-best performance based on the KITTI Eigen split and the eighth-best performance based on the NYU Depth V2.

A novel technique of tibial tuberosity fracture fixation with two knotless suture anchors in an adult: A case report and literature review.

Tibial tuberosity fractures are uncommon in adults. Surgery for these types of fractures is performed similarly to that of tibial tuberosity avulsion fractures in adolescents. The most commonly introduced method is to fix the displaced bone fragments using screws or wires and, if necessary, use tension band wiring for augmentation. However, if the bone fragments are too small or severely comminuted, it may be challenging to fix them using the conventional method. In this study, we introduced a fixation method using two knotless suture anchors that could be attempted in such cases. Since this surgical method fixes the bone fragments without direct damage to the bone fragments, it can be used even when the fragments are small or comminuted. This technique achieved a nearly full active range of knee motion without an extension lag at four weeks postoperatively. In addition, there were no complications related to surgery, and a complete bone union was achieved without additional dislocation. Therefore, this surgical method may be a good alternative if a fixation of the fracture is considered problematic by the conventional method.

Apoptosis Occurs in the Anterior Talofibular Ligament of Patients With Chronic Lateral Ankle Instability: An In Vitro Study.

BACKGROUND: Chronic lateral ankle instability is treated operatively, whereas most acute ankle sprains associated with acute anterior talofibular ligament injury are usually treated nonoperatively. This treatment strategy is widely accepted and has been validated using a variety of clinical or radiological methods. We suspected that there may be biological differences between chronic and acutely injured ligaments, particularly with respect to apoptosis. Apoptosis is known to cause ligament degeneration. If it could be demonstrated that apoptosis occurs more in the anterior talofibular ligament tissues of patients with chronic lateral ankle instability compared with patients with acute anterior talofibular ligament injury, biological evidence could be supported. QUESTIONS/PURPOSES: We sought to (1) elucidate the difference in the extent of apoptosis between patients with chronic lateral ankle instability and those with acute anterior talofibular ligament injury. In addition, we asked: (2) What is the expression level of apoptotic enzymes such as caspases 3, 7, 8, and 9 and cytochrome c in each patient group? (3) Is there a correlation between apoptotic activities and the symptom duration period of chronic lateral ankle instability? METHODS: Between March 2019 and February 2021, 50 patients were prospectively enrolled in this study. Anterior talofibular ligament tissues were harvested from patients who were divided into two groups: the chronic lateral ankle instability group and the acute anterior talofibular ligament injury group. Patients with insufficient remaining ligaments were excluded from the chronic lateral ankle instability group, and cases in which the tissue was severely damaged or the quality of collected tissue was insufficient because of severe impingement into the fracture site were excluded from the acute anterior talofibular ligament injury group. Tissues were collected from 21 patients (11 males and 10 females) in the chronic lateral ankle instability group with a mean age of 37 ± 14 years and from 17 patients (6 males and 11 females) in the acute anterior talofibular ligament injury group with a mean age of 49 ± 17 years. To investigate our first purpose, apoptotic cells were counted using a TUNEL assay. To answer our second question, Western blotting for apoptotic enzymes such as caspases 3, 7, 8, and 9 and cytochrome c was performed to investigate apoptotic activity. Immunohistochemistry was also used to detect apoptotic enzymes. To answer our third question, the time elapsed after the first symptom related to chronic lateral ankle instability occurred and the expression level of each enzyme was investigated. RESULTS: More apoptotic cells were observed in the chronic lateral ankle instability group than in the acute anterior talofibular ligament injury group in the TUNEL assay. Western blotting revealed that the apoptotic activities of the chronic lateral ankle instability group were higher than those of the acute anterior talofibular ligament injury group: caspase 3 was 117 in the chronic lateral ankle instability group and 59 in the acute anterior talofibular ligament injury group (mean difference 58 [95% confidence interval (CI) 31 to 86]; p < 0.001), caspase 7 was 138 in the chronic lateral ankle instability group and 45 in the acute anterior talofibular ligament injury group (mean difference 93 [95% CI 58 to 128]; p < 0.001), caspase 8 was 126 in the chronic lateral ankle instability group and 68 in the acute anterior talofibular ligament injury group (mean difference 58 [95% CI 29 to 89]; p < 0.001), caspase 9 was 128 in the chronic lateral ankle instability group and 54 in the acute anterior talofibular ligament injury group (mean difference 74 [95% CI 44 to 104]; p < 0.001), and cytochrome c was 139 in the chronic lateral ankle instability group and 51 in the acute anterior talofibular ligament injury group (mean difference 88 [95% CI 46 to 129]; p < 0.001). Immunohistochemistry revealed higher expression of caspases 3, 7, 8, and 9 and cytochrome c in the chronic lateral ankle instability group compared with those in the acute anterior talofibular ligament injury group. Caspases 3, 7, and 9 showed no correlation with duration of chronic lateral ankle instability symptoms: the Pearson correlation coefficient was 0.22 [95% CI -0.25 to 0.69] for caspase 3 (p = 0.36), 0.29 [95% CI -0.16 to 0.74] for caspase 7 (p = 0.23), and 0.29 [95% CI -0.16 to 0.74] for caspase 9 (p = 0.23). CONCLUSION: In chronic lateral ankle instability, apoptotic activity in the anterior talofibular ligament was higher than in acute anterior talofibular ligament injury. CLINICAL RELEVANCE: Apoptosis occurs more in chronic injured ligaments than in acutely injured ligaments. Although urgent surgical repair is not required for acute anterior talofibular ligament injury, chronic lateral ankle instability may progress if the nonoperative treatment is not successful. Further research should focus not only on timing of apoptotic progression, but also on biological augmentation to reverse or prevent apoptosis within the anterior talofibular ligament.

Association Between Pain Catastrophizing and Central Sensitization Among Patients With Severe Knee Osteoarthritis Awaiting Primary Total Knee Arthroplasty.

Total knee arthroplasty (TKA) is among the most successful types of surgery for the treatment of knee osteoarthritis (OA). However, nearly 20% of patients report unexpected pain after surgery. Recently, some studies have proposed that pain after TKA is related to pain catastrophizing (PC) and central sensitization (CS). However, there is no study comparing PC and CS for the same patient with knee OA requiring TKA. Thus, the goal of this study was to confirm the association between PC and CS among patients with knee OA awaiting primary TKA. This study was conducted with the clinical data of 153 patients collected between July 2019 and February 2021. Both PC and CS were evaluated with the Pain Catastrophizing Scale (PCS) and the Central Sensitizing Inventory (CSI). Patients with PCS scores higher than 30 were classified as high-level catastrophizing. Patients with CSI scores higher than 40 were classified as central sensitized. The distribution of PC and CS levels was confirmed, and the correlation between PC and CS was analyzed. A significant correlation was found between PCS and CSI scores, with Pearson's correlation coefficient of 0.606. Participants with high-level catastrophizing were 2.07 times more likely to belong to the central sensitized group compared with those who did not show high-level catastrophizing. Participants in the central sensitized group were 3.02 times more likely to belong to the high-level catastrophizing group than those who were not central sensitized. In conclusion, many patients with knee OA awaiting primary TKA had high-level catastrophizing, and a significant association was found between PC and CS. [Orthopedics. 2022;45(4):197-202.].

Age-dependent pathogenic characteristics of SARS-CoV-2 infection in ferrets.

While the seroprevalence of SARS-CoV-2 in healthy people does not differ significantly among age groups, those aged 65 years or older exhibit strikingly higher COVID-19 mortality compared to younger individuals. To further understand differing COVID-19 manifestations in patients of different ages, three age groups of ferrets are infected with SARS-CoV-2. Although SARS-CoV-2 is isolated from all ferrets regardless of age, aged ferrets (≥3 years old) show higher viral loads, longer nasal virus shedding, and more severe lung inflammatory cell infiltration, and clinical symptoms compared to juvenile (≤6 months) and young adult (1-2 years) groups. Furthermore, direct contact ferrets co-housed with the virus-infected aged group shed more virus than direct-contact ferrets co-housed with virus-infected juvenile or young adult ferrets. Transcriptome analysis of aged ferret lungs reveals strong enrichment of gene sets related to type I interferon, activated T cells, and M1 macrophage responses, mimicking the gene expression profile of severe COVID-19 patients. Thus, SARS-CoV-2-infected aged ferrets highly recapitulate COVID-19 patients with severe symptoms and are useful for understanding age-associated infection, transmission, and pathogenesis of SARS-CoV-2.

The systemic inflammatory landscape of COVID-19 in pregnancy: Extensive serum proteomic profiling of mother-infant dyads with in utero SARS-CoV-2.

While pregnancy increases the risk for severe COVID-19, the clinical and immunological implications of COVID-19 on maternal-fetal health remain unknown. Here, we present the clinical and immunological landscapes of 93 COVID-19 mothers and 45 of their SARS-CoV-2-exposed infants through comprehensive serum proteomics profiling for >1,400 cytokines of their peripheral and cord blood specimens. Prenatal SARS-CoV-2 infection triggers NF-κB-dependent proinflammatory immune activation. Pregnant women with severe COVID-19 show increased inflammation and unique IFN-λ antiviral signaling, with elevated levels of IFNL1 and IFNLR1. Furthermore, SARS-CoV-2 infection re-shapes maternal immunity at delivery, altering the expression of pregnancy complication-associated cytokines, inducing MMP7, MDK, and ESM1 and reducing BGN and CD209. Finally, COVID-19-exposed infants exhibit induction of T cell-associated cytokines (IL33, NFATC3, and CCL21), while some undergo IL-1ß/IL-18/CASP1 axis-driven neonatal respiratory distress despite birth at term. Our findings demonstrate COVID-19-induced immune rewiring in both mothers and neonates, warranting long-term clinical follow-up to mitigate potential health risks.

Transtibial Amputation with Removal of the Tibial Intramedullary Nail: Hardware Removal in a Retrograde Manner.

Transtibial amputation is the preferred strategy for treating a diabetic foot with an infection and necrosis. However, if a tibial intramedullary nail was previously inserted into the ipsilateral lower extremity, the nail must be removed to perform the transtibial amputation. In this special situation, the removal of the tibial intramedullary nail can cause various complications after transtibial amputation. We present a case and surgical technique report of a 46-year-old male with an uncontrolled diabetic foot with tibial intramedullary nail insertion. With the nail and ankle fixed by distal interlocking screws, a below-knee amputation was performed by removing the nail and the amputated limb together. This surgical method is expected to reduce postoperative complications such as infections and patella instability after the amputation of a diabetic foot.

Age-dependent pathogenic characteristics of SARS-CoV-2 infection in ferrets.

While the seroprevalence of SARS-CoV-2 in healthy people does not differ significantly among age groups, those aged 65 years or older exhibit strikingly higher COVID-19 mortality compared to younger individuals. To further understand differing COVID-19 manifestations in patients of different ages, three age groups of ferrets were infected with SARS-CoV-2. Although SARS-CoV-2 was isolated from all ferrets regardless of age, aged ferrets (≥ 3 years old) showed higher viral loads, longer nasal virus shedding, and more severe lung inflammatory cell infiltration and clinical symptoms compared to juvenile (≤ 6 months) and young adult (1-2 years) groups. Transcriptome analysis of aged ferret lungs revealed strong enrichment of gene sets related to type I interferon, activated T cells, and M1 macrophage responses, mimicking the gene expression profile of severe COVID-19 patients. Thus, SARS-CoV-2-infected aged ferrets highly recapitulate COVID-19 patients with severe symptoms and are useful for understanding age-associated infection, transmission, and pathogenesis of SARS-CoV-2.

Molecular Signatures of Inflammatory Profile and B-Cell Function in Patients with Severe Fever with Thrombocytopenia Syndrome.

Dabie bandavirus (severe fever with thrombocytopenia syndrome virus [SFTSV]) induces an immunopathogenic disease with a high fatality rate; however, the mechanisms underlying its clinical manifestations are largely unknown. In this study, we applied targeted proteomics and single-cell transcriptomics to examine the differential immune landscape in SFTS patient blood. Serum immunoprofiling identified low-risk and high-risk clusters of SFTS patients based on inflammatory cytokine levels, which corresponded to disease severity. Single-cell transcriptomic analysis of SFTS patient peripheral blood mononuclear cells (PBMCs) at different infection stages showed pronounced expansion of B cells with alterations in B-cell subsets in fatal cases. Furthermore, plasma cells in which the interferon (IFN) pathway is downregulated were identified as the primary reservoir of SFTSV replication. This study identified not only the molecular signatures of serum inflammatory cytokines and B-cell lineage populations in SFTSV-induced fatalities but also plasma cells as the viral reservoir. Thus, this suggests that altered B-cell function is linked to lethality in SFTSV infections.IMPORTANCE SFTSV is an emerging virus discovered in China in 2009; it has since spread to other countries in East Asia. Although the fatality rates of SFTSV infection range from 5.3% to as high as 27%, the mechanisms underlying clinical manifestations are largely unknown. In this study, we demonstrated that SFTSV infection in fatal cases caused an excessive inflammatory response through high induction of proinflammatory cytokines and chemokines and the aberrant inactivation of adaptive immune responses. Furthermore, single-cell transcriptome sequencing (RNA-seq) analysis of SFTS patient PBMCs revealed that SFTSV targets the B-cell lineage population, especially plasma cells, as the potential viral reservoir in patients for whom the infection is fatal. Thus, SFTSV infection may inhibit high-affinity antibody maturation and secretion of plasma B cells, suppressing neutralizing antibody production and thereby allowing significant virus replication and subsequent fatality.

Antiviral Efficacies of FDA-Approved Drugs against SARS-CoV-2 Infection in Ferrets.

Due to the urgent need of a therapeutic treatment for coronavirus (CoV) disease 2019 (COVID-19) patients, a number of FDA-approved/repurposed drugs have been suggested as antiviral candidates at clinics, without sufficient information. Furthermore, there have been extensive debates over antiviral candidates for their effectiveness and safety against severe acute respiratory syndrome CoV 2 (SARS-CoV-2), suggesting that rapid preclinical animal studies are required to identify potential antiviral candidates for human trials. To this end, the antiviral efficacies of lopinavir-ritonavir, hydroxychloroquine sulfate, and emtricitabine-tenofovir for SARS-CoV-2 infection were assessed in the ferret infection model. While the lopinavir-ritonavir-, hydroxychloroquine sulfate-, or emtricitabine-tenofovir-treated group exhibited lower overall clinical scores than the phosphate-buffered saline (PBS)-treated control group, the virus titers in nasal washes, stool specimens, and respiratory tissues were similar between all three antiviral-candidate-treated groups and the PBS-treated control group. Only the emtricitabine-tenofovir-treated group showed lower virus titers in nasal washes at 8 days postinfection (dpi) than the PBS-treated control group. To further explore the effect of immune suppression on viral infection and clinical outcome, ferrets were treated with azathioprine, an immunosuppressive drug. Compared to the PBS-treated control group, azathioprine-immunosuppressed ferrets exhibited a longer period of clinical illness, higher virus titers in nasal turbinate, delayed virus clearance, and significantly lower serum neutralization (SN) antibody titers. Taken together, all antiviral drugs tested marginally reduced the overall clinical scores of infected ferrets but did not significantly affect in vivo virus titers. Despite the potential discrepancy of drug efficacies between animals and humans, these preclinical ferret data should be highly informative to future therapeutic treatment of COVID-19 patients.IMPORTANCE The SARS-CoV-2 pandemic continues to spread worldwide, with rapidly increasing numbers of mortalities, placing increasing strain on health care systems. Despite serious public health concerns, no effective vaccines or therapeutics have been approved by regulatory agencies. In this study, we tested the FDA-approved drugs lopinavir-ritonavir, hydroxychloroquine sulfate, and emtricitabine-tenofovir against SARS-CoV-2 infection in a highly susceptible ferret infection model. While most of the drug treatments marginally reduced clinical symptoms, they did not reduce virus titers, with the exception of emtricitabine-tenofovir treatment, which led to diminished virus titers in nasal washes at 8 dpi. Further, the azathioprine-treated immunosuppressed ferrets showed delayed virus clearance and low SN titers, resulting in a prolonged infection. As several FDA-approved or repurposed drugs are being tested as antiviral candidates at clinics without sufficient information, rapid preclinical animal studies should proceed to identify therapeutic drug candidates with strong antiviral potential and high safety prior to a human efficacy trial.

The Cap-Snatching SFTSV Endonuclease Domain Is an Antiviral Target.

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a tick-borne virus with 12%-30% case mortality rates and is related to the Heartland virus (HRTV) identified in the United States. Together, SFTSV and HRTV are emerging segmented, negative-sense RNA viral (sNSV) pathogens with potential global health impact. Here, we characterize the amino-terminal cap-snatching endonuclease domain of SFTSV polymerase (L) and solve a 2.4-Å X-ray crystal structure. While the overall structure is similar to those of other cap-snatching sNSV endonucleases, differences near the C terminus of the SFTSV endonuclease suggest divergence in regulation. Influenza virus endonuclease inhibitors, including the US Food and Drug Administration (FDA) approved Baloxavir (BXA), inhibit the endonuclease activity in in vitro enzymatic assays and in cell-based studies. BXA displays potent activity with a half maximal inhibitory concentration (IC50) of ∼100 nM in enzyme inhibition and an EC50 value of ∼250 nM against SFTSV and HRTV in plaque assays. Together, our data support sNSV endonucleases as an antiviral target.