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Objectives This study was conducted to assess the efficacy of nirmatrelvir/ritonavir treatment in patients with coronavirus disease 2019 (COVID-19), particularly those aged 60 years and older. Using real-world data, the period during which the BN.1 Omicron variant was dominant was compared to the period dominated by the BA.5 variant. Methods In this retrospective cohort study, data were collected regarding 2,665,281 patients infected with severe acute respiratory syndrome coronavirus 2 between July 24, 2022, and March 31, 2023. Propensity score matching was utilized to match patients who received nirmatrelvir/ritonavir in a 1:4 ratio between BN.1 and BA.5 variant groups. Multivariable logistic regression analysis was employed to assess the effects of nirmatrelvir/ritonavir within these groups. Results Compared to the prior period, the efficacy of nirmatrelvir/ritonavir did not significantly differ during the interval of Omicron BN.1 variant dominance in the Republic of Korea. Among patients treated with nirmatrelvir/ritonavir, a significantly lower risk of mortality was observed in the BN.1 group (odds ratio [OR], 0.698; 95% confidence interval [CI], 0.557–0.875) compared to the BA.5 group. However, this treatment did not significantly reduce the risk of severe or critical illness, including death, for those in the BN.1 group (OR, 0.856; 95% CI, 0.728–1.007). Conclusion Nirmatrelvir/ritonavir has maintained its effectiveness against COVID-19, even with the emergence of the BN.1 Omicron subvariant. Consequently, we strongly recommend the administration of nirmatrelvir/ritonavir to patients exhibiting COVID-19-related symptoms, irrespective of the dominant Omicron variant or their vaccination status, to mitigate disease severity and decrease the risk of mortality.

Abstract Backgrounds The expression of major histocompatibility complex I (MHC-I) in neurons has recently been shown to regulate neurite outgrowth and synaptic plasticity. However, its contribution to neurodegenerative diseases such as Alzheimer's disease (AD) remains largely unknown. Methods In this study, we investigated the relationship between impaired MHC-I-β2M complex and AD in vitro and human AD samples. Interaction between protein was identified by liquid chromatography-tandem mass spectrometry and confirmed by immunoprecipitation. Single-chain trimer of MHC-I-β2M was generated to study the effect of stabilization of MHC-I-β2M complex on NCAM1 signaling. Results MHC-I is destabilized in the brains of AD patients and neuronal cells treated with oligomeric β-amyloid (Aβ). Specifically, Aβ oligomers disassemble the MHC-I-β2-microglobulin (β2M) complex, leading to reduced interactions with neural cell adhesion molecule 1 (NCAM1), a novel interactor of neuronal MHC-I, and decreased signaling. Inhibition of MHC-I-β2M complex destabilization by non-dissociable MHC-I-β2M-peptide complex restored MHC-I-NCAM1 signaling in neuronal cells. Conclusions The current study demonstrated that disruption of MHC-1-NCAM1 signaling by Aβ induced disassembly of MHC-I-β2M complex is involved in the pathophysiology of AD. Moreover, our findings suggest modulation of MHC-I stability may be a potential therapeutic target for restoring synaptic function in AD.

Abstract Although T cell activation is known to involve the internalization of the T cell antigen receptor (TCR), much less is known regarding the release of TCRs following T cell interaction with cognate antigen-presenting cells. In this study, we examine the physiological mechanisms underlying TCR release following T cell activation. We show that T cell activation results in the shedding of TCRs in T cell microvilli, which involves a combined process of trogocytosis and enzymatic vesiculation, leading to the loss of membrane TCRs and microvilli-associated proteins and lipids. Surprisingly, unlike TCR internalization, this event results in the rapid upregulation of surface TCR expression and metabolic reprogramming of cholesterol and fatty acid synthesis to support cell division and survival. These results demonstrate that TCRs are lost through trogocytic ‘molting’ following T cell activation and highlight this mechanism as an important regulator of clonal expansion.

Objectives This study aimed to classify coronavirus disease 2019 (COVID-19)-related deaths according to whether COVID-19 was listed as the cause of death, and to investigate the differences in demographic characteristics and risk factors for COVID-19 death classifications. Methods A total of 5,625 deaths in South Korea among patients with confirmed COVID-19 from January 20, 2020 to December 31, 2021 were selected. Excluding false reports and unnatural deaths, 5,597 deaths were analyzed. Based on death report data, deaths were classified according to whether the cause of death was listed as COVID-19 (CD) or not (NCD). The epidemiological characteristics and causes of deaths were investigated using descriptive, univariate, and multivariate statistical analyses. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to analyze the risk factors. Results The case fatality ratio was 0.89% and increased with age. Additionally, 96.4% of the subjects had an underlying disease, and 53.4% died in winter. The proportion of NCDs was 9.3%, of whom 19.1% died at home and 39.0% were confirmed to have COVID-19 after death. Malignant neoplasms (102/416 vs. 637/4,442; OR, 1.71; 95% CI, 1.36−2.16; p

Obesity and overweight, frequently caused by a lack of exercise, are associated with many metabolic diseases, such as hypertension, diabetes, and dyslipidemia. Aerobic exercise effectively increases the high-density lipoproteins-cholesterol (HDL-C) levels and alleviates the triglyceride (TG) levels. The consumption of Cuban policosanol (Raydel®) is also effective in enhancing the HDL-C quantity and HDL functionality to treat dyslipidemia and hypertension. On the other hand, no study has examined the effects of a combination of high-intensity exercise and policosanol consumption in obese subjects to improve metabolic disorders. In the current study, 17 obese subjects (average BMI 30.1 ± 1.1 kg/m2, eight male and nine female) were recruited to participate in a program combining exercise and policosanol (20 mg) consumption for 12 weeks. After completion, their BMI, waist circumference, total fat mass, systolic blood pressure (SBP), and diastolic blood pressure (DBP) reduced significantly up to around −15%, −13%, −33%, −11%, and −13%, respectively. In the serum lipid profile, at Week 12, a significant reduction was observed in the total cholesterol (TC) and triglyceride (TG) levels, up to −17% and −54% from the baseline, respectively. The serum HDL-C was elevated by approximately +12% from the baseline, as well as the percentage of HDL-C in TC, and HDL-C/TC (%), was enhanced by up to +32% at Week 12. The serum coenzyme Q10 (CoQ10) level was increased 1.2-fold from the baseline in all participants at Week 12. In particular, the male participants exhibited a 1.4-fold increase from the baseline. The larger rise in serum CoQ10 was correlated with the larger increase in the serum HDL-C (r = 0.621, p = 0.018). The hepatic function parameters were improved; the serum γ-glutamyl transferase decreased at Week 12 by up to −55% (p < 0.007), while the aspartate aminotransferase and alanine transaminase levels diminished within the normal range. In the lipoprotein level, the extent of oxidation and glycation were reduced significantly with the reduction in TG content. The antioxidant abilities of HDL, such as paraoxonase (PON) and ferric ion reduction ability (FRA), were enhanced significantly by up to 1.8-fold and 1.6-fold at Week 12. The particle size and number of HDL were elevated up to +10% during the 12 weeks, with a remarkable decline in the TG content, glycation extent, and oxidation. The improvements in HDL quality and functionality were linked to the higher survivability of adult zebrafish and their embryos, under the co-presence of carboxymethyllysine (CML), a pro-inflammatory molecule known to cause acute death. In conclusion, 12 weeks of Cuban policosanol (Raydel®, 20 mg) consumption with high-intensity exercise displayed a significant improvement in blood pressure, body fat mass, blood lipid profile without liver damage, CoQ10 metabolism, and renal impairment.

The spatiotemporal pattern of the spread of pathologically modified tau through brain regions in Alzheimer’s disease (AD) can be explained by prion-like cell-to-cell seeding and propagation of misfolded tau aggregates. Hence, to develop targeted therapeutic antibodies, it is important to identify the seeding- and propagation-competent tau species. The hexapeptide 275VQIINK280 of tau is a critical region for tau aggregation, and K280 is acetylated in various tauopathies, including AD. However, the mechanism that links tau acetylated on lysine 280 (tau-acK280) to subsequent progression to neurodegenerative disease remains unclear. Here, we demonstrate that tau-acK280 is critical for tau propagation processes including secretion, aggregation, and seeding. We developed an antibody, Y01, that specifically targets tau-acK280 and solved the crystal structure of Y01 in complex with an acK280 peptide. The structure confirmed that Y01 directly recognizes acK280 and the surrounding residues. Strikingly, upon interaction with acetylated tau aggregates, Y01 prevented tauopathy progression and increased neuronal viability in neuron cultures and in tau-Tg mice through antibody-mediated neutralization and phagocytosis, respectively. Based on our observations that tau-acK280 is a core species involved in seeding and propagation activities, the Y01 antibody that specifically recognizes acK280 represents a promising therapeutic candidate for AD and other neurodegenerative diseases associated with tauopathy.

Background/Aims Coronavirus disease 2019 (COVID-19) is a global pandemic that had affected more than 13,000 people in South Korea by July 2020. To prevent spread of COVID-19, tele-prescription was permitted temporarily. This study investigated the impact of tele-prescription on glycemic control in patients with type 2 diabetes. Methods Glycated hemoglobin (HbA1c) concentrations were retrospectively analyzed in patients with type 2 diabetes who were treated with tele-prescription because of COVID-19 and those who were treated by face-to-face care (non-tele-prescription group) enrolled at the same period of time. Mean HbA1c concentrations and mean change in HbA1c concentration (ΔHbA1c) were compared in these two groups. Results The mean HbA1c levels of patients were significantly higher after than before the tele-prescription period (7.46% ± 1.24% vs. 7.27% ± 1.13%, p < 0.05). Mean ΔHbA1c was significantly higher in the tele-prescription than in the non-tele-prescription group (0.19% ± 0.68% vs. 0.04% ± 0.95%, p < 0.05). HbA1c was significantly greater in patients taking fewer oral hypoglycemic agents, no insulin, fewer comorbidities (e.g., coronary artery disease, cerebrovascular accident, and diabetic neuropathy), and higher baseline HbA1c. Conclusions Tele-prescription may worsen glycemic control in patients with type 2 diabetes during public health crises.

BackgroundCoronavirus disease 2019 (COVID-19) is a global pandemic that had affected more than eight million people worldwide by June 2020. Given the importance of the presence of diabetes mellitus (DM) for host immunity, we retrospectively evaluated the clinical characteristics and outcomes of moderate-to-severe COVID-19 in patients with diabetes.MethodsWe conducted a multi-center observational study of 1,082 adult inpatients (aged ≥18 years) who were admitted to one of five university hospitals in Daegu because of the severity of their COVID-19-related disease. The demographic, laboratory, and radiologic findings, and the mortality, prevalence of severe disease, and duration of quarantine were compared between patients with and without DM. In addition, 1:1 propensity score (PS)-matching was conducted with the DM group.ResultsCompared with the non-DM group (n=847), patients with DM (n=235) were older, exhibited higher mortality, and required more intensive care. Even after PS-matching, patients with DM exhibited more severe disease, and DM remained a prognostic factor for higher mortality (hazard ratio, 2.40; 95% confidence interval, 1.38 to 4.15). Subgroup analysis revealed that the presence of DM was associated with higher mortality, especially in older people (≥70 years old). Prior use of a dipeptidyl peptidase-4 inhibitor or a renin-angiotensin system inhibitor did not affect mortality or the clinical severity of the disease.ConclusionDM is a significant risk factor for COVID-19 severity and mortality. Our findings imply that COVID-19 patients with DM, especially if elderly, require special attention and prompt intensive care.

This study describes the epidemiological characteristics of coronavirus disease 2019 (COVID-19) based on reported cases from long-term care facilities. As of April 20th, 2020, 3 long-term care facilities in a metropolitan area of South Korea had reported cases of COVID-19. These facilities’ employees were presumed to be the sources of infection. There were 2 nursing hospitals that did not report any additional cases. One nursing home had a total of 25 cases, with an attack rate of 51.4% (95% CI 35.6–67.0), and a fatality rate of 38.9% (95% CI 20.3–61.4) among residents. The results from this study suggest that early detection and maintenance of infection control minimizes the risk of rapid transmission.

Since the first case was contracted by coronavirus disease-19 (COVID-19) in Daegu, Korea in February 2020, about 6,800 cases and 130 deaths have been reported on April 9, 2020. Recent studies have reported that patients with diabetes showed higher mortality and they had a worse prognosis than the group without diabetes. In poorly controlled patients with diabetes, acute hyperglycemic crises such as diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS) also might be precipitated by COVID-19. Thus, intensive monitoring and aggressive supportive care should be needed to inadequately controlled patients with diabetes and COVID-19 infection. Here, we report two cases of severe COVID-19 patients with acute hyperglycemic crises in Korea.

ABSTRACT: Since its first appearance in 1996, H9N2 avian influenza virus (AIV) of the Y439 lineage persisted in Korean live bird markets (LBMs) until the last documented occurrence in 2018. However, in June 2020, the avian influenza surveillance program detected a novel H9N2 AIV belonging to the Y280 lineage, which has zoonotic potential, in a Korean native chicken (KNC) from a LBM. In this study, we infected KNCs and ducks (the 2 major species held at LBMs), as well as SPF chickens, with Y280-lineage H9N2 AIV LBM261/20 and Y439-equivalent LBM294/18 to compare pathogenicity and transmissibility. In SPF chickens, LBM261/20 replicated mostly in the respiratory tract and spread rapidly among birds. By contrast, LBM294/18 replicated preferentially in the gastrointestinal tract and transmitted more slowly than LBM261/20. LBM261/20 replicated for a longer time in KNCs than in SPF chickens, and only in the respiratory tract; by contrast, LBM294/18 was detected in the oropharynx and cloaca. Ducks did not shed either virus or seroconvert. Taken together, the data suggest that the scheme used to monitor the newly introduced H9N2 AIV of the Y280 lineage needs to be modified to place emphasis on oropharyngeal sampling. Such changes will facilitate better disease control and protect public health.

Renal fibrosis is considered to be the final common outcome of chronic kidney disease. Dipeptidyl peptidase-4 (DPP-4) inhibitors have demonstrated protective effects against diabetic kidney disease. However, the anti-fibrotic effect of evogliptin, a DPP-4 inhibitor, has not been studied. Here, we report the beneficial effects of evogliptin on unilateral ureteral obstruction (UUO)-induced renal fibrosis in mice. Evogliptin attenuated UUO-induced renal atrophy and tubulointerstitial fibrosis. Immunohistochemistry and Western blotting demonstrated that evogliptin treatment inhibits pro-fibrotic gene expressions and extracellular matrix production. In vitro findings showed that the beneficial effects of evogliptin on renal fibrosis are mediated by inhibition of the transforming growth factor-β/Smad3 signaling pathway. The present study demonstrates that evogliptin is protective against UUO-induced renal fibrosis, suggesting that its clinical applications could extend to the treatment of kidney disease of non-diabetic origin.

Central post-stroke pain (CPSP) is an intractable neuropathic pain that can occur following central nervous system injuries. Spino-thalamo-cortical pathway damage contributes to CPSP development. However, brain regions involved in CPSP are unknown and previous studies were limited to supratentorial strokes with cortical lesion involvement. We analyzed the brain metabolism changes associated with CPSP following pontine hemorrhage. Thirty-two patients with isolated pontine hemorrhage were examined; 14 had CPSP, while 18 did not. Brain glucose metabolism was evaluated using 18F-fluorodeoxyglucose-positron emission tomography images. Additionally, regions revealing metabolic correlation with CPSP severity were analyzed. Patients with CPSP showed changes in the brain metabolism in the cerebral cortices and cerebellum. Compared with the control group, the CPSP group showed significant hypometabolism in the contralesional rostral anterior cingulum and ipsilesional primary motor cortex (Puncorrected < 0.001). However, increased brain metabolism was observed in the ipsilesional cerebellum (VI) and contralesional cerebellum (lobule VIIB) (Puncorrected < 0.001). Moreover, increased pain intensity correlated with decreased metabolism in the ipsilesional supplementary motor area and contralesional angular gyrus. This study emphasizes the role of the many different areas of the cortex that are involved in affective and cognitive processing in the development of CPSP.

Atomic level engineering of graphene-based materials is highly demanded for the customized structures and properties. Here, the authors show heteroatom dopant-specific unzipping of carbon nanotubes as a reliable and controllable route to customized 'intact crystalline' graphene-based nanostructures.

Severe weather events occur more frequently due to climate change; therefore, accurate weather forecasts are necessary, in addition to the development of numerical weather prediction (NWP) of the past several decades. A method to improve the accuracy of weather forecasts based on NWP is the collection of more meteorological data by reducing the observation interval. However, in many areas, it is economically and locally difficult to collect observation data by installing automatic weather stations (AWSs). We developed a Mini-AWS, much smaller than AWSs, to complement the shortcomings of AWSs. The installation and maintenance costs of Mini-AWSs are lower than those of AWSs; Mini-AWSs have fewer spatial constraints with respect to the installation than AWSs. However, it is necessary to correct the data collected with Mini-AWSs because they might be affected by the external environment depending on the installation area. In this paper, we propose a novel error correction of atmospheric pressure data observed with a Mini-AWS based on machine learning. Using the proposed method, we obtained corrected atmospheric pressure data, reaching the standard of the World Meteorological Organization (WMO; ±0.1 hPa), and confirmed the potential of corrected atmospheric pressure data as an auxiliary resource for AWSs.

BackgroundBoth systemic inflammatory reaction and regional myocardial ischemia/reperfusion injury may elicit hypercoagulability after off-pump coronary artery bypass grafting (OPCAB). We investigated the influence of ulinastatin, which suppresses the activity of polymorphonuclear leukocyte elastase and production of pro-inflammatory cytokines, on coagulation in patients with elevated high-sensitivity C-reactive protein (hsCRP) undergoing OPCAB.MethodsFifty patients whose preoperative hsCRP > 3.0 mg/L were randomly allocated into the ulinastatin (600,000 U) or control group. Serum concentrations of thrombin-antithrombin complex (TAT) and prothrombin fragment 1+2 (F1+2) were measured preoperatively, immediately after surgery, and at 24 h after surgery, respectively. Secondary endpoints included platelet factor (PF)-4, amount of blood loss, and transfusion requirement.ResultsAll baseline values of TAT, F1+2, and PF-4 were higher than the normal range in both groups. F1+2 was elevated in both groups at immediate, and at 24 h after surgery as compared to baseline value, without any significant intergroup differences. Remaining coagulation parameters, transfusion requirement and blood loss during operation and postoperative 24 h were not different between the two groups.ConclusionsIntraoperative administration of ulinastatin did not convey beneficial influence in terms of coagulation and blood loss in high-risk patients with elevated hsCRP undergoing multivessel OPCAB, who already exhibited hypercoagulability before surgery.

Spontaneous rupture of the urinary bladder is a rare clinical entity, with the incidence reported as 1 in 126,000 hospital admissions. It is often associated with malignancy, inflammatory lesions, irradiation, calculus, diverticulum, binge alcohol drinking, continuous bladder irrigation, and neurogenic bladder. In rare instances, bladder rupture occurs without obvious causes. This rare clinical condition is difficult to diagnose because of vague symptoms. High index of suspicion is needed as the mortality rate is high if untreated. A 37-year-old woman with uncontrolled type 2 diabetes, was admitted to the emergency room complaining of progressive abdominal distension and discomfort. She had a past history of tubo-ovarian and bladder abscess, and had undergone multiple surgical operations. From ascites fluid study, she was diagnosed as spontaneous bladder rupture. A transurethral catheter was inserted and the symptoms and signs resolved. Bladder rupture, mimicking acute kidney injury of diabetic nephropathy was disclosed without surgery.

BackgroundThe aim of this study was to investigate the influences of visceral adiposity on cardiovascular autonomic neuropathy (CAN) in patients with type 2 diabetes mellitus.MethodsTwo hundred eleven patients with type 2 diabetes participated in this study. Anthropometric and metabolic parameters were measured, and the visceral fat area was assessed using computed tomography. CAN was diagnosed using a cardiovascular reflex test. We analyzed the correlation between the visceral fat area and each parameter in this test.ResultsThe mean age, body mass index (BMI), and duration of diabetes of the study population were 60±14 years (mean±standard deviation), 25.1±4.2 kg/m2, and 12.3±8.9 years, respectively. The visceral fat area showed positive correlations with age, BMI, waist circumference, and subcutaneous fat area. There was no statistically significant difference in the cardiovascular reflex test outcome between genders. Univariate linear regression analysis showed that an increased visceral fat area diminished good heart rate response to a Valsalva maneuver (R2=4.9%, P=0.013 in an unadjusted model), but only in women. This statistical association was preserved after adjusting for age and BMI (R2=9.8%, P=0.0072).ConclusionThe results of this study suggest that visceral adiposity contributes to an autonomic imbalance to some degree, as demonstrated by the impaired cardiovascular reflex test among women with type 2 diabetes.

BackgroundPostoperative acute kidney injury (AKI) is a significant complication after coronary artery bypass surgery. Prior coronary angiography increases the likelihood of AKI due to the use of a radiocontrast dye. This study examined the effect of coronary angiography on the postoperative renal function after off-pump coronary artery bypass surgery (OPCAB).MethodsThe records of 110 patients who required OPCAB were reviewed. These patients also had at least two of the following conditions: chronic kidney disease, hypertension, diabetes mellitus, emergency surgery, congestive heart failure, age >75 years, hematocrit

This meta-analysis investigated current trends in generative AI research in L2 and Korean language education internationally and domestically, aiming to guide future educational directions. Domestically, most studies focused on university students, with fewer studies on middle and high school students, elementary students, and teachers. Similarly, international studies also predominantly focused on university students. In Korean language education, research primarily involved adult learners, highlighting the effective use of AI tools with intermediate to advanced learners. Analysis of participant numbers revealed that most studies in English and Korean education involved 11-50 participants. Methodologically, many studies in English and Korean education employed quantitative methods, whereas international studies used qualitative approaches. Research on language skills predominantly focused on participant perceptions, with subsequent emphasis on speaking and writing. However, there were significant gaps in studies addressing listening and grammar skills. As a result of a comprehensive analysis of language skills, the research emphasized the area of writing, revealing that learners generally exhibited positive perceptions across the studies. To maximize the educational value of ChatGPT, it is crucial to teach students effective questioning techniques. Future research should focus on specific prompt usage methods and enhance self-directed learning using metacognitive strategies. [ABSTRACT FROM AUTHOR]

Background: Repetitive transcranial magnetic stimulation (rTMS) is widely used therapy to enhance motor deficit in stroke patients. To date, rTMS protocols used in stroke patients are relatively unified. However, as the pathophysiology of stroke is diverse and individual functional deficits are distinctive, more precise application of rTMS is warranted. Therefore, the objective of this study was to determine the effects of personalized protocols of rTMS therapy based on the functional reserve of each stroke patient in subacute phase. Methods: This study will recruit 120 patients with stroke in subacute phase suffering from the upper extremity motor impairment, from five different hospitals in Korea. The participants will be allocated into three different study conditions based on the functional reserve of each participant, measured by the results of TMS-induced motor evoked potentials (MEPs), and brain MRI with diffusion tensor imaging (DTI) evaluations. The participants of the intervention-group in the three study conditions will receive different protocols of rTMS intervention, a total of 10 sessions for 2 weeks: high-frequency rTMS on ipsilesional primary motor cortex (M1), high-frequency rTMS on ipsilesional ventral premotor cortex, and high-frequency rTMS on contralesional M1. The participants of the controlgroup in all three study conditions will receive the same rTMS protocol: lowfrequency rTMS on contralesional M1. For outcome measures, the following assessments will be performed at baseline (T0), during-intervention (T1), postintervention (T2), and follow-up (T3) periods: Fugl-Meyer Assessment (FMA), Box-and-block test, Action Research Arm Test, Jebsen-Taylor hand function test, hand grip strength, Functional Ambulatory Category, fractional anisotropy measured by the DTI, and brain network connectivity obtained from MRI. The primary outcome will be the difference of upper limb function, as measured by FMA from T0 to T2. The secondary outcomes will be the differences of other assessments. Discussion: This study will determine the effects of applying different protocols of rTMS therapy based on the functional reserve of each patient. In addition, this methodology may prove to be more efficient than conventional rTMS protocols. Therefore, effective personalized application of rTMS to stroke patients can be achieved based on their severity, predicted mechanism of motor recovery, or functional reserves. [ABSTRACT FROM AUTHOR]

This paper examines whether and to what extent an AI tutor affects TOEIC learning of English learners. For the study, a total of 110 students were recruited and randomly assigned to an AI tutor group (n = 57) and a human tutor group (n = 53). The study also investigates the difference in English proficiency among students in the two groups. Before the experiment, a TOEIC pre-test was administered. Based on the pre-test scores, participants were grouped into three CEFR proficiency levels: A1, A2, and B1. During the experimental period, the AI tutor group self-studied English with an AI tutor. The human tutor group took a traditional English class offered by a human tutor. After the experiment, a post-test was administered. The study found that the human tutor group increased their TOEIC test scores at all proficiency levels at the 5% significance level. On the other hand, the AI tutor group showed significant increases only at A1 and A2 levels. The group difference was statistically significant for the A1-level participants, indicating the superior effects of the AI tutor over the human tutor. On a basis of the findings, pedagogical implications are made. [ABSTRACT FROM AUTHOR]