Deciphering AKI in Burn Patients: Correlations between Clinical Clusters and Biomarkers.

Acute kidney injury (AKI) is a significant complication in burn patients, impacting outcomes substantially. This study explores the heterogeneity of AKI in burn patients by analyzing creatinine time-series data to identify distinct AKI clusters and evaluating routine biomarkers' predictive values. A retrospective cohort analysis was performed on 2608 adult burn patients admitted to Hangang Sacred Heart Hospital's Burn Intensive Care Unit (BICU) from July 2010 to December 2022. Patients were divided into four clusters based on creatinine trajectories, ranging from high-risk, severe cases to lower-risk, short-term care cases. Cluster A, characterized by high-risk, severe cases, showed the highest mortality and severity, with significant predictors being PT and TB. Cluster B, representing intermediate recovery cases, highlighted PT and albumin as useful predictors. Cluster C, a low-risk, high-resilience group, demonstrated predictive values for cystatin C and eGFR cys. Cluster D, comprising lower-risk, short-term care patients, indicated the importance of PT and lactate. Key biomarkers, including albumin, prothrombin time (PT), cystatin C, eGFR cys, and total bilirubin (TB), were identified as significant predictors of AKI development, varying across clusters. Diagnostic accuracy was assessed using area under the curve (AUC) metrics, reclassification metrics (NRI and IDI), and decision curve analysis. Cystatin C and eGFR cys consistently provided significant predictive value over creatinine, with AUC values significantly higher (p < 0.05) in each cluster. This study highlights the need for a tailored, biomarker-driven approach to AKI management in burn patients, advocating for the integration of diverse biomarkers in clinical practice to facilitate personalized treatment strategies. Future research should validate these biomarkers prospectively to confirm their clinical utility.

Cisd2 deficiency impairs neutrophil function by regulating calcium homeostasis via Calnexin and SERCA.

In the context of aging, the susceptibility to infectious diseases increases, leading to heightened morbidity and mortality. This phenomenon, termed immunosenescence, is characterized by dysregulation in the aging immune system, including abnormal alterations in lymphocyte composition, elevated basal inflammation, and the accumulation of senescent T cells. Such changes contribute to increased autoimmune diseases, enhanced infection severity, and reduced responsiveness to vaccines. Utilizing aging animal models becomes imperative for a comprehensive understanding of immunosenescence, given the complexity of aging as a physiological process in living organisms. Our investigation focuses on Cisd2, a causative gene for Wolfram syndrome, to elucidate on immunosenescence. Cisd2 knockout (KO) mice, serving as a model for premature aging, exhibit a shortened lifespan with early onset of aging-related features, such as decreased bone density, hair loss, depigmentation, and optic nerve degeneration. Intriguingly, we found that the Cisd2 KO mice present a higher number of neutrophils in the blood; however, isolated neutrophils from these mice display functional defects. Through mass spectrometry analysis, we identified an interaction between Cisd2 and Calnexin, a protein known for its role in protein quality control. Beyond this function, Calnexin also regulates calcium homeostasis through interaction with sarcoendoplasmic reticulum calcium transport ATPase (SERCA). Our study proposes that Cisd2 modulates calcium homeostasis via its interaction with Calnexin and SERCA, consequently influencing neutrophil functions. [BMB Reports 2024; 57(5): 256-261].

Complete chloroplast genome sequence of the liverwort, Porella grandiloba Lindb. (Porellaceae).

Porella grandiloba Lindb. is a liverwort species of Porellaceae, primarily distributed in East Asia. Here, we determined the complete chloroplast (cp) genome sequence of P. grandiloba. The complete cp genome was 121,433 bp in length with a typical quadripartite structure consisting of a large single-copy region (83,039 bp), a small single-copy region (19,586 bp), and two copies of inverted repeat regions (9,404 bp, each). Genome annotation predicted 131 genes, including 84 protein-coding, 36 tRNA, and eight rRNA genes. The maximum likelihood tree indicated that P. grandiloba was sister to P. perrottetiana, which species formed a clade with Radula japonica (Radulaceae).

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.

OASL phase condensation induces amyloid-like fibrillation of RIPK3 to promote virus-induced necroptosis.

RIPK3-ZBP1-MLKL-mediated necroptosis is a proinflammatory cell death process that is crucial for antiviral host defence. RIPK3 self-oligomerization and autophosphorylation are prerequisites for executing necroptosis, yet the underlying mechanism of virus-induced RIPK3 activation remains elusive. Interferon-inducible 2'-5' oligoadenylate synthetase-like (OASL) protein is devoid of enzymatic function but displays potent antiviral activity. Here we describe a role of OASL as a virus-induced necroptosis promoter that scaffolds the RIPK3-ZBP1 non-canonical necrosome via liquid-like phase condensation. This liquid-like platform of OASL recruits RIPK3 and ZBP1 via protein-protein interactions to provide spatial segregation for RIPK3 nucleation. This process facilitates the amyloid-like fibril formation and activation of RIPK3 and thereby MLKL phosphorylation for necroptosis. Mice deficient in Oasl1 exhibit severely impaired necroptosis and attenuated inflammation after viral infection, resulting in uncontrolled viral dissemination and lethality. Our study demonstrates an interferon-induced innate response whereby OASL scaffolds RIPK3-ZBP1 assembly via its phase-separated liquid droplets to facilitate necroptosis-mediated antiviral immunity.

Herpesvirus-induced spermidine synthesis and eIF5A hypusination for viral episomal maintenance.

Spermidine is essential for cellular growth and acts as a prerequisite of hypusination, a post-translational modification of eukaryotic initiation factor 5A (eIF5A), allowing the translation of polyproline-containing proteins. Here, we show that oncogenic Kaposi's sarcoma-associated herpesvirus (KSHV) increases spermidine synthesis and eIF5A hypusination to enhance expression of polyproline-containing latency-associated nuclear antigen (LANA) for viral episomal maintenance. KSHV upregulates intracellular spermidine levels by dysregulating polyamine metabolic pathways in three-dimensional (3D) culture and 2D de novo infection conditions. Increased intracellular spermidine leads to increased eIF5A hypusination, ultimately enhancing LANA expression. In contrast, inhibition of spermidine synthesis or eIF5A hypusination alleviates LANA expression, decreasing viral episomal maintenance and KSHV-infected cell proliferation in vitro and in vivo, which is reversed by spermidine supplement. This demonstrates that KSHV hijacks spermidine synthesis and eIF5A hypusination pathways to enhance LANA expression for viral episomal maintenance, suggesting polyamine metabolism and eIF5A hypusination as therapeutic targets for KSHV-induced tumorigenesis.

Cohnella herbarum sp. nov., isolated from wild grass fermentation broth.

A novel strictly aerobic, Gram-stain-positive, rod-shaped, motile, endospore-forming, white-coloured bacterium, designated strain MFER-1T, was isolated from a fermented liquor of wild grasses sampled in the Republic of Korea. The respiratory quinone of strain MFER-1T was menaquinone-7 and its major cellular fatty acids were anteiso-C15 : 0 (55.3 %), iso-C16 : 0 (17.5 %) and C16 : 0 (12.1 %). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, four unidentified aminophospholipids and an unidentified phospholipid. The 16S rRNA gene sequence of strain MFER-1T showed similarity of 98.1 % to 'Cohnella cholangitidis' 1 605-214T and below 98.0 % sequence similarity to the other Cohnella species. The phylogenomic tree indicated that strain MFER-1T formed a reliable cluster with several Cohnella species. The estimated genome size of strain MFER-1T was 8.52 Mb. Genomic DNA G+C content was 50.7mol%. The orthologous average nucleotide identity, digital DNA-DNA hybridization and amino acid identity values of strain MFER-1T with the most closely related species 'Cohnella cholangitidis' 1 605-214T were 78.7, 23.0 and 79.6 %, respectively. Based on the phenotypic, chemotaxonomic and phylogenetic results, strain MFER-1T should represent a novel species of the genus Cohnella, for which the name Cohnella herbarum sp. nov. is proposed, with strain MFER-1T (=KACC 21 257T=NBRC 114 628T) as the type strain.

Single-cell analysis of Kaposi's sarcoma-associated herpesvirus infection in three-dimensional air-liquid interface culture model.

The oral cavity is the major site for transmission of Kaposi's sarcoma-associated herpesvirus (KSHV), but how KSHV establishes infection and replication in the oral epithelia remains unclear. Here, we report a KSHV spontaneous lytic replication model using fully differentiated, three-dimensional (3D) oral epithelial organoids at an air-liquid interface (ALI). This model revealed that KSHV infected the oral epithelia when the basal epithelial cells were exposed by damage. Unlike two-dimensional (2D) cell culture, 3D oral epithelial organoid ALI culture allowed high levels of spontaneous KSHV lytic replication, where lytically replicating cells were enriched at the superficial layer of epithelial organoid. Single cell RNA sequencing (scRNAseq) showed that KSHV infection induced drastic changes of host gene expression in infected as well as uninfected cells at the different epithelial layers, resulting in altered keratinocyte differentiation and cell death. Moreover, we identified a unique population of infected cells containing lytic gene expression at the KSHV K2-K5 gene locus and distinct host gene expression compared to latent or lytic infected cells. This study demonstrates an in vitro 3D epithelial organoid ALI culture model that recapitulates KSHV infection in the oral cavity, where KSHV undergoes the epithelial differentiation-dependent spontaneous lytic replication with a unique cell population carrying distinct viral gene expression.

Diffusion-weighted Breast MRI in Prediction of Upstaging in Women with Biopsy-proven Ductal Carcinoma in Situ.

Background Accurate preoperative prediction of upstaging in women with biopsy-proven ductal carcinoma in situ (DCIS) is important for surgical planning, but published models using predictive MRI features remain lacking. Purpose To develop and validate a predictive model based on preoperative breast MRI to predict upstaging in women with biopsy-proven DCIS and to select high-risk women who may benefit from sentinel lymph node biopsy at initial surgery. Materials and methods Consecutive women with biopsy-proven DCIS who underwent preoperative 3.0-T breast MRI including dynamic contrast-enhanced (DCE) MRI and diffusion-weighted imaging (DWI) and who underwent surgery between June 2019 and March 2020 were retrospectively identified (development set) from an academic medical center. The apparent diffusion coefficients of lesions from DWI, lesion size and morphologic features on DCE MRI scans, mammographic findings, age, symptoms, biopsy method, and DCIS grade at biopsy were collected. The presence of invasive cancer and axillary metastases was determined with surgical pathology. A predictive model for upstaging was developed by using multivariable logistic regression and validated in a subsequent prospective internal validation set recruited between July 2020 and April 2021. Results Fifty-seven (41%) of 140 women (mean age, 53 years ± 11 [SD]) in the development set and 43 (41%) of 105 women (mean age, 53 years ± 10) in the validation set were upstaged after surgery. The predictive model combining DWI and clinical-pathologic factors showed the areas under the receiver operating characteristic curve at 0.87 (95% CI: 0.80, 0.92) in the development set and 0.76 (95% CI: 0.67, 0.84) in the validation set. The predicted probability of invasive cancer showed good interobserver agreement (intraclass correlation coefficient, 0.79); the positive predictive value was 85% (28 of 33), and the negative predictive value was 92% (22 of 24). Conclusion A predictive model based on diffusion-weighted breast MRI identified women at high risk of upstaging. © RSNA, 2022 Online supplemental material is available for this article See also the editorial by Baltzer in this issue. An earlier incorrect version appeared online. This article was corrected on July 7, 2022.

Multiple intussusceptions after blunt abdominal trauma in a 9-year-old boy: A case report and literature review.

Traumatic intussusception is exceedingly rare. According to the existing literature, most cases are treated surgically. However, the treatment and prognosis of traumatic intussusception are not well understood, and more research is needed to determine the most beneficial treatment options. Multiple intussusceptions were found on a computed tomography scan of a 9-year-old boy with multiple severe traumatic injuries resulting from a car accident while riding an electric scooter. Conservative management was performed, and spontaneous reduction was successfully achieved without complications. This is the first reported case where multiple traumatic intussusceptions in a pediatric patient were managed without surgical intervention. Thus, traumatic intussusception of varied quantity and quality might be managed conservatively, yielding spontaneous resolution with the prerequisites of stable vital signs and no evidence of intestinal ischemia or perforation.

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.

Effect of Bacillus mesonae H20-5 Treatment on Rhizospheric Bacterial Community of Tomato Plants under Salinity Stress.

Plant growth-promoting bacteria improve plant growth under abiotic stress conditions. However, their effects on microbial succession in the rhizosphere are poorly understood. In this study, the inoculants of Bacillus mesonae strain H20-5 were administered to tomato plants grown in soils with different salinity levels (EC of 2, 4, and 6 dS/m). The bacterial communities in the bulk and rhizosphere soils were examined 14 days after H20-5 treatment using Illumina MiSeq sequencing of the bacterial 16S rRNA gene. Although the abundance of H20-5 rapidly decreased in the bulk and rhizosphere soils, a shift in the bacterial community was observed following H20-5 treatment. The variation in bacterial communities due to H20-5 treatment was higher in the rhizosphere than in the bulk soils. Additionally, the bacterial species richness and diversity were greater in the H20-5 treated rhizosphere than in the control. The composition and structure of the bacterial communities varied with soil salinity levels, and those in the H20-5 treated rhizosphere soil were clustered. The members of Actinobacteria genera, including Kineosporia, Virgisporangium, Actinoplanes, Gaiella, Blastococcus, and Solirubrobacter, were enriched in the H20-5 treated rhizosphere soils. The microbial co-occurrence network of the bacterial community in the H20-5 treated rhizosphere soils had more modules and keystone taxa compared to the control. These findings revealed that the strain H20-5 induced systemic tolerance in tomato plants and influenced the diversity, composition, structure, and network of bacterial communities. The bacterial community in the H20-5 treated rhizosphere soils also appeared to be relatively stable to soil salinity changes.

Improving the care of inflammatory bowel disease (IBD) patients: perspectives and strategies for IBD center management.

The incidence and prevalence rates of inf lammatory bowel disease (IBD) have been increasing in East Asian countries over the past few decades. Accordingly, the general understanding and awareness of IBD among healthcare professionals has increased considerably in this region. This increase is ultimately associated with the evolving focus of IBD clinicians devoted to comprehensive patient care, especially in establishing IBD clinics/centers capable of providing multidisciplinary counseling. Comprehensive IBD care at IBD clinics/centers usually includes surgical and medication decision-making, transition from pediatric to adult clinics, care of extraintestinal manifestations, care of infectious diseases in patients undergoing immunomodulatory or biologic therapies, and nutritional, psychosocial, socioeconomic, and pharmacological care. Team members comprise specialists from various departments related to IBD and can be divided into core and ad hoc members. Usually, the scope of work in IBD clinics/centers involves patient care, patient outreach, and system management. Considering the environmental changes in IBD treatment, it is necessary to perform comprehensive IBD patient care in the form of a program based on competencies, rather than simply following the organization of previous IBD centers. The present review summarizes recent trends in IBD patient care and offers perspectives regarding IBD center management.

METTL8 mRNA Methyltransferase Enhances Cancer Cell Migration via Direct Binding to ARID1A.

The association of RNA modification in cancer has recently been highlighted. Methyltransferase like 8 (METTL8) is an enzyme and its role in mRNA m3C modification has barely been studied. In this study, we found that METTL8 expression was significantly up-regulated in canine mammary tumor and investigated its functional roles in the tumor process, including cancer cell proliferation and migration. METTL8 expression was up-regulated in most human breast cancer cell lines tested and decreased by Yin Yang 1 (YY1) transcription factor knockdown, suggesting that YY1 is a regulating transcription factor. The knockdown of METTL8 attenuated tumor cell growth and strongly blocked tumor cell migration. AT-rich interactive domain-containing protein 1A (ARID1A) was identified as a candidate mRNA by METTL8. ARID1A mRNA binds to METTL8 protein. ARID1A mRNA expression was not changed by METTL8 knockdown, but ARID1A protein level was significantly increased. Collectively, our study indicates that METTL8 up-regulated by YY1 in breast cancer plays an important role in cancer cell migration through the mRNA modification of ARID1A, resulting in the attenuation of its translation.

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.

Protaetiibacter larvae sp. nov. and Agromyces intestinalis sp. nov., isolated from the gut of larvae of Protaetia brevitarsis seulensis, reclassification of Lysinimonas yzui as Pseudolysinimonas yzui comb. nov. and emended description of the genus Pseudolysinimonas.

Two bacterial strains, FWR-8T and CFWR-9T, were isolated from the gut of larvae of Protaetia brevitarsis seulensis that were raised at the National Institute of Agricultural Sciences, Wanju-gun, Republic of Korea. Both strains were strictly aerobic, Gram-stain-positive and non-motile. Strain FWR-8T possessed the highest sequence similarity (98.7 %) to that of Protaetiibacter intestinalis 2DFWR-13T and the phylogenetic tree revealed that strain FWR-8T formed a cluster with Ptb. intestinalis 2DFWR-13T. Pseudolysinimonas kribbensis MSL-13T and Lysinimonas yzui N7XX-4T shared a high 16S rRNA gene sequence similarity (97.8 %) and formed a cluster adjacent to the cluster that included Ptb. intestinalis 2DFWR-13T. The 16S rRNA gene sequence of strain CFWR-9T exhibited the highest similarity (97.7 %) to that of Agromyces binzhouensis OAct353T and the phylogenetic tree indicated that strain CFWR-9T formed one independent cluster with A. binzhouensis OAct353T that was within the radius of the genus Agromyces. The peptidoglycan type, major fatty acids, major menaquinones and total polar lipids of strain FWR-8T were characterized as type B1, iso-C16 : 0, anteiso-C15 : 0 and anteiso-C17 : 0, MK-15, MK-16 and MK-14, and diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and one unidentified lipid, respectively. Those from strain CFWR-9T were type B1, iso-C16 : 0, anteiso-C15 : 0 and anteiso-C17 : 0, MK-11, MK-12 and MK-10, and diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and one unidentified lipid, respectively. Based on the phenotypic and genotypic data, strains FWR-8T and CFWR-9T each represent a novel species within the genera Protaetiibacter and Agromyces, respectively. For these species, the names Protaetiibacter larvae sp. nov. and Agromyces intestinalis sp. nov. have been proposed, with the type strains FWR-8T (=KACC 19322T=NBRC 113051T) and CFWR-9T (=KACC 19306T=NBRC 113046T), respectively. Our results also justify a reclassification of Lysinimonas yzui as Pseudolysinimonas yzui comb. nov. and an emended description of the genus Pseudolysinimonas isprovided.

Development of Spike Receptor-Binding Domain Nanoparticles as a Vaccine Candidate against SARS-CoV-2 Infection in Ferrets.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a causative agent of the CoV disease 2019 (COVID-19) pandemic, enters host cells via the interaction of its receptor-binding domain (RBD) of the spike protein with host angiotensin-converting enzyme 2 (ACE2). Therefore, the RBD is a promising vaccine target to induce protective immunity against SARS-CoV-2 infection. In this study, we report the development of an RBD protein-based vaccine candidate against SARS-CoV-2 using self-assembling Helicobacter pylori-bullfrog ferritin nanoparticles as an antigen delivery system. RBD-ferritin protein purified from mammalian cells efficiently assembled into 24-mer nanoparticles. Sixteen- to 20-month-old ferrets were vaccinated with RBD-ferritin nanoparticles (RBD nanoparticles) by intramuscular or intranasal inoculation. All vaccinated ferrets with RBD nanoparticles produced potent neutralizing antibodies against SARS-CoV-2. Strikingly, vaccinated ferrets demonstrated efficient protection from SARS-CoV-2 challenge, showing no fever, body weight loss, or clinical symptoms. Furthermore, vaccinated ferrets showed rapid clearance of infectious virus in nasal washes and lungs as well as of viral RNA in respiratory organs. This study demonstrates that spike RBD-nanoparticles are an effective protein vaccine candidate against SARS-CoV-2.

Development of spike receptor-binding domain nanoparticle as a vaccine candidate against SARS-CoV-2 infection in ferrets.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a causative agent of COVID-19 pandemic, enters host cells via the interaction of its Receptor-Binding Domain (RBD) of Spike protein with host Angiotensin-Converting Enzyme 2 (ACE2). Therefore, RBD is a promising vaccine target to induce protective immunity against SARS-CoV-2 infection. In this study, we report the development of RBD protein-based vaccine candidate against SARS-CoV-2 using self-assembling H. pylori -bullfrog ferritin nanoparticles as an antigen delivery. RBD-ferritin protein purified from mammalian cells efficiently assembled into 24-mer nanoparticles. 16-20 months-old ferrets were vaccinated with RBD-ferritin nanoparticles (RBD-nanoparticles) by intramuscular or intranasal inoculation. All vaccinated ferrets with RBD-nanoparticles produced potent neutralizing antibodies against SARS-CoV-2. Strikingly, vaccinated ferrets demonstrated efficient protection from SARS-CoV-2 challenge, showing no fever, body weight loss and clinical symptoms. Furthermore, vaccinated ferrets showed rapid clearance of infectious viruses in nasal washes and lungs as well as viral RNA in respiratory organs. This study demonstrates the Spike RBD-nanoparticle as an effective protein vaccine candidate against SARS-CoV-2.

Critical role of neutralizing antibody for SARS-CoV-2 reinfection and transmission.

Cases of laboratory-confirmed SARS-CoV-2 reinfection have been reported in a number of countries. Further, the level of natural immunity induced by SARS-CoV-2 infection is not fully clear, nor is it clear if a primary infection is protective against reinfection. To investigate the potential association between serum antibody titres and reinfection of SARS-CoV-2, ferrets with different levels of NAb titres after primary SARS-CoV-2 infection were subjected to reinfection with a heterologous SARS-CoV-2 strain. All heterologous SARS-CoV-2 reinfected ferrets showed active virus replication in the upper respiratory and gastro-intestinal tracts. However, the high NAb titre group showed attenuated viral replication and rapid viral clearance. In addition, direct-contact transmission was observed only from reinfected ferrets with low NAb titres (<20), and not from other groups. Further, lung histopathology demonstrated the presence of limited inflammatory regions in the high NAb titre groups compared with control and low NAb groups. This study demonstrates a close correlation between a low NAb titre and SARS-CoV-2 reinfection in a recovered ferret reinfection model.