Drosophila myosin mutants model the disparate severity of type 1 and type 2B distal arthrogryposis and indicate an enhanced actin affinity mechanism

BACKGROUND

Distal arthrogryposis (DA) is a group of autosomal dominant skeletal muscle diseases characterized by congenital contractures of distal limb joints. The most common cause of DA is a mutation of the embryonic myosin heavy chain gene, MYH3. Human phenotypes of DA are divided into the weakest form-DA1, a moderately severe form-DA2B (Sheldon-Hall Syndrome), and a severe DA disorder-DA2A (Freeman-Sheldon Syndrome). As models of DA1 and DA2B do not exist, their disease mechanisms are poorly understood.

METHODS

We produced the first models of myosin-based DA1 (F437I) and DA2B (A234T) using transgenic Drosophila melanogaster and performed an integrative analysis of the effects of the mutations. Assessments included lifespan, locomotion, ultrastructural analysis, muscle mechanics, ATPase activity, in vitro motility, and protein modeling.

RESULTS

We observed significant defects in DA1 and DA2B Drosophila flight and jump ability, as well as myofibril assembly and stability, with homozygotes displaying more severe phenotypes than heterozygotes. Notably, DA2B flies showed dramatically stronger phenotypic defects compared to DA1 flies, mirroring the human condition. Mechanical studies of indirect flight muscle fibers from DA1 heterozygotes revealed reduced power output along with increased stiffness and force production, compared to wild-type controls. Further, isolated DA1 myosin showed significantly reduced myosin ATPase activity and in vitro actin filament motility. These data in conjunction with our sinusoidal analysis of fibers suggest prolonged myosin binding to actin and a slowed step associated with Pi release and/or the power stroke. Our results are supported by molecular modeling studies, which indicate that the F437I and A234T mutations affect specific amino acid residue interactions within the myosin motor domain that may alter interaction with actin and nucleotide.

CONCLUSIONS

The allele-specific ultrastructural and locomotory defects in our Drosophila DA1 and DA2B models are concordant with the differential severity of the human diseases. Further, the mechanical and biochemical defects engendered by the DA1 mutation reveal that power production, fiber stiffness, and nucleotide handling are aberrant in F437I muscle and myosin. The defects observed in our DA1 and DA2B Drosophila models provide insight into DA phenotypes in humans, suggesting that contractures arise from prolonged actomyosin interactions.

Covert COVID-19: Cone Beam Computed Tomography Lung Changes in an Asymptomatic Patient Receiving Radiation Therapy

PURPOSE

COVID-19 profoundly affected the United States, with New York City rapidly becoming the epicenter of the disease. Patients with cancer represent a vulnerable population in this pandemic, with data suggesting a higher risk for severe events and unfavorable outcomes. Timely identification of COVID-19 in patients with cancer has been thwarted by the limited availability of outpatient testing for SARS-CoV-2. Chest computed tomography (CT) plays a major role in the identification of COVID-19 pneumonia, with radiologic hallmarks including bilateral, peripheral ground-glass opacities (GGOs) and consolidation. Patients with cancer undergoing radiation therapy (RT) commonly have daily cone beam computed tomography (CBCT) obtained for image-guided RT, and such imaging frequently includes the chest.

METHODS AND MATERIALS

We retrospectively reviewed the CBCT scans of an initially asymptomatic patient undergoing image-guided RT for breast cancer who developed COVID-19 symptoms during the second week of RT. Lung windows of daily CBCT scans were reviewed with diagnostic radiology to survey for changes consistent with COVID-19. Diagnostic CT scans at the time of recovery were obtained and compared with the CBCTs.

RESULTS

Five consecutive CBCT scans were retrospectively reviewed. Bilateral, peripheral GGOs were noted on the fourth and fifth CBCT scans in the 2 days before symptom onset. CBCT on the day of RT resumption demonstrated substantial worsening of the GGO compared with scans obtained during the asymptomatic phase. Diagnostic CTs demonstrated bilateral, peripheral GGOs and mediastinal lymphadenopathy, findings suggesting COVID-19 pneumonitis. Repeat diagnostic CT 3 days later showed improved pulmonary findings, and the patient resumed RT without incident.

CONCLUSIONS

Familiarity with typical CT changes of COVID-19 pneumonitis may allow for early detection in cancer patients undergoing CBCT for RT treatment. Prompt review of the lung windows is recommended to identify such changes, with the hope that presymptomatic diagnosis leads to expedited patient management, improved outcomes, and a reduction of inadvertent COVID-19 dissemination.

Blepharospasm, dry eye and extractable nuclear antigen antibodies

PURPOSE

To study whether there is an association between benign essential blepharospasm and Sjögren's syndrome by analyzing the presence of antibodies to extractable nuclear antigens in this population.

METHODS

Seventy-two patients with benign essential blepharospasm (BEB) were included in this study. We excluded patients with hemifacial spasm or blepharospasm secondary to known corneal pathology. We recorded results of Schirmer I testing as well as levels of anti-SSA/Ro and anti-SSB/La antibodies.

RESULTS

Our study included 72 patients (144 eyes), of which 62 (86.1%) were women. The mean age was 74.3±10.73 years. The mean Schirmer I test result was 3.14±4.00mm. Five women (8% of this female population) were found to have positive anti-SSA/Ro and anti-SSB/La antibodies. Their mean age was 65.66±13.24 years, while the mean age of the antibody-negative patients was 75.42±9.27 years. There was no statistically significant difference between the Schirmer I tests of the antibody positive and negative patients.

CONCLUSION

This study demonstrates a possible association between Sjögren's syndrome and benign essential blepharospasm, justifying anti-SSA/Ro and anti-SSB/La testing in these patients.

Efficacy of a Latex Agglutination Test for Rapid Identification of Staphylococcus aureus: Collaborative Study

Fifteen laboratories completed a collaborative study comparing the efficacy of a latex agglutination kit (Aureus Test) with that of AOAC Official Method 987.09 (coagulase test for identification of Staphylococcus aureus). Each laboratory analyzed 240 strains of bacteria, including 160 isolates of S. aureus and 80 isolates of other bacteria. Upon receipt of cultures, collaborators subcultured each isolate on both tryptic soy agar (TSA) and Baird-Parker agar medium (BPA) to determine whether the growth medium has any effect on either method. For cultures grown on TSA, the latex test had sensitivity and specificity rates of 99.2 and 97.1 %, respectively, whereas the coagulase test had respective rates of 98.4 and 92.5%. For cultures able to grow on BPA, the latex test had sensitivity and specificity rates of 99.2 and 96.6%, respectively, while the coagulase test had respective rates of 98.3 and 91.3%. By using the McNemar pairwise comparison test of the 2 methods, the falsepositive and false-negative rates of the latex test were significantly lower (p < 0.01) than those of the coagulase test for strains grown either on TSA or BPA. The latex agglutination test for identification of S. aureus isolated from foods has been adopted by AOAC INTERNATIONAL.

[Correlation between BRAP expression and prognosis of patients with laryngeal squamous cell carcinoma]

Objective:To investigate the expression of BRCA1 associated protein（BRAP） and its correlations with clinicopathological features and prognosis of patients with laryngeal squamous cell carcinoma（LSCC）. Method:The protein expression of BRAP in LSCC tissues and normal laryngeal tissues were assessed by immunohistochemistry and Western blot, and their correlations with clinicopathological features and prognosis were statistically analyzed. Result:The expression of BRAP in LSCC was significantly higher than that in normal laryngeal tissues（P<0.05）. BRAP expression was significantly correlated with the TNM stage and lymph node metastasis（P<0.05）. Kaplan-Meier survival analysis showed that LSCC patients with high BRAP expression had worse overall survival than those with low BRAP expression（P<0.01）. Multivariate Cox proportional-hazards analysis showed that the high expression of BRAP protein was an important poor prognostic indicator of the patients. Conclusion:BRAP is related with the development of LSCC, and it may be used as an important prognostic biomarker for LSCC patients.

Changes on Dynamic Cerebral Autoregulation Are Associated with Delayed Cerebral Ischemia in Patients with Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Early identification of vasospasm prior to symptom onset would allow prevention of delayed cerebral ischemia (DCI) in aneurysmal subarachnoid hemorrhage (aSAH). Dynamic cerebral autoregulation (DCA) is a noninvasive means of assessing cerebral blood flow regulation by determining independence of low-frequency temporal oscillations of systemic blood pressure (BP) and cerebral blood flow velocities (CBFV).

METHODS

Eight SAH patients underwent prospectively a median of 7 DCA assessments consisting of continuous measurements of BCFV and BP. Transfer function analysis was applied to calculate average phase shift (PS) in low (0.07-0.2 Hz) frequency range for each hemisphere as continuous measure of DCA. Lower PS indicated poorer regulatory response. DCI was defined as a 2-point decrease in Glasgow Coma Score and/or infarction on CT.

RESULTS

Three subjects developed symptomatic vasospasm with median time-to-DCI of 9 days. DCI was significantly associated with lower PS over the entire recording period (Wald = 4.28; p = 0.039). Additionally, there was a significant change in PS over different recording periods after adjusting for DCI (Wald = 15.66; p = 0.001); particularly, a significantly lower mean PS day 3-5 after bleed (14.22 vs 27.51; p = 0.05).

CONCLUSIONS

DCA might be useful for early detection of symptomatic vasospasm. A larger cohort study of SAH patients is currently underway.

P3432Coronary artery calcium score is of limited sensitivity in detecting subclinical atherosclerosis in young individuals with family history of coronary artery disease

Introduction

Family history of premature coronary artery disease (CAD) is known to predispose individuals to adverse CAD events, often at a younger age. Current risk stratification strategy is suboptimal, as up to 50% of individuals were considered “low-risk” prior to their first presentation of myocardial infarction. Coronary artery calcium score (CACS) is a marker of atherosclerosis and provides incremental value in risk stratification. However, the utility of CACS may be limited in younger patients as they often have non-calcified atherosclerotic plaques. In this study, we evaluate the sensitivity of CACS in detecting subclinical atherosclerosis in different age groups.

Method

From 310 referrals to a specialized unit in the management of early atherosclerosis, 222 individuals with a family history of premature CAD (defined as CAD events in first-degree family members, male<55 and female<65) and aged between 35 and 55 were enrolled for assessment of their CAD risks. Individuals with possible, probably or definite familial hypercholesterolemia were excluded. In addition to clinical and risk factor evaluation, cardiac CT and CACS were performed in select individuals, at the discretion of the treating physician.

Results

Of the 141 (59% male, mean age 45.9±6.0 year) individuals that completed clinical evaluation, 65 (73% male, mean age 47.4±6.9 years) have subclinical atherosclerosis (defined by the presence of atherosclerotic plaques in any of the coronary artery segments in cardiac CT). Of them, 52 have CACS>0, giving an overall sensitivity of 80%. The breakdown by age group is shown in table 1. The sensitivity of CACS in detecting subclinical atherosclerosis is quite modest in younger individuals (60% in individuals <45 year-old) but improves with patient age (>85% in >45 years).

Table 1. Sensitivity of CACS in different age groups Age group True Positive Fast Negative Sensitivity N (CAC+ CTCA+) (CAC+ CTCA−) (%) <40 6 4 60 10 41–45 7 4 55 11 46–50 19 3 86 22 51–55 20 1 95 21

Conclusion

In younger individuals (<45 years) with family history of premature CAD, CACS is of limited sensitivity in detecting subclinical atherosclerosis, and should not be used to rule out CAD. Further studies are warranted.

P3412Risk factors, biomarkers and framingham risk estimate fail to identify presence of subclinical atherosclerosis in young individual with family history of premature coronary artery disease

Introduction

Patients with family history of premature coronary artery disease (CAD) are at increased risk of CAD events at a younger age. Risk factor based approaches and clinical evaluation are most commonly used to assess these individuals. However, it has been recently shown that up to 50% of individual presenting with their first myocardial infarction (MI) were considered to be “low risk” prior to that event. MI is often a result of plaque rupture preceded by progression of subclinical atherosclerosis. Detection of subclinical atherosclerosis may therefore help target prevention of plaque progression. We assessed the value of clinical risk factor, biomarkers and Framingham Risk Score (FRS) in predicting subclinical atherosclerosis in individuals with a family history of premature CAD.

Methods

From 310 referrals, 222 individuals between the ages of 35 and 55 with a family history of premature CAD (CAD events in first-degree family members (male <55, female <65)) were enrolled for evaluation of risk of CAD. Those with familial hypercholesteremia (possible, probable or definite) were excluded. Patients underwent clinical and risk factor evaluations as well as Cardiac CT or Calcium Score (CS) to assess presence of subclinical / clinical atherosclerosis at the discretion of the treating physician.

Results

In this pilot, 141 individuals (59% male, mean age 45.9±6.0 years) completed evaluation, and 65 (46%) had evidence of subclinical atherosclerosis on CT coronary angiography or CT calcium score with a mean segment involvement score (SIS) of 2.8 and mean CS of 152, putting them above the 80th percentile for their age and sex. Aside from male sex, age, and smoking history, other traditional risk factors and biomarkers including diabetes mellitus, hypertension, total cholesterol, LDL-C, HDL-C and Cholesterol/HDL-C were not significantly different between those with or without subclinical atherosclerosis (Table 1).

Table 1

Conclusion

In young individuals with a family history of premature CAD, risk factors, biomarkers, and FRS failed to identify individuals with premature, subclinical atherosclerosis in this pilot study. Detection of subclinical atherosclerosis and early implementation of treatment with the aim of stabilizing plaques and stopping progression might prove vital in reducing events in these individuals. Further studies are warranted.

The R249Q hypertrophic cardiomyopathy myosin mutation decreases contractility in Drosophila by impeding force production

KEY POINTS

Hypertrophic cardiomyopathy (HCM) is a genetic disease that causes thickening of the heart's ventricular walls and is a leading cause of sudden cardiac death. HCM is caused by missense mutations in muscle proteins including myosin, but how these mutations alter muscle mechanical performance in largely unknown. We investigated the disease mechanism for HCM myosin mutation R249Q by expressing it in the indirect flight muscle of Drosophila melanogaster and measuring alterations to muscle and flight performance. Muscle mechanical analysis revealed R249Q decreased muscle power production due to slower muscle kinetics and decreased force production; force production was reduced because fewer mutant myosin cross-bridges were bound simultaneously to actin. This work does not support the commonly proposed hypothesis that myosin HCM mutations increase muscle contractility, or causes a gain in function; instead, it suggests that for some myosin HCM mutations, hypertrophy is a compensation for decreased contractility.

ABSTRACT

Hypertrophic cardiomyopathy (HCM) is an inherited disease that causes thickening of the heart's ventricular walls. A generally accepted hypothesis for this phenotype is that myosin heavy chain HCM mutations increase muscle contractility. To test this hypothesis, we expressed an HCM myosin mutation, R249Q, in Drosophila indirect flight muscle (IFM) and assessed myofibril structure, skinned fibre mechanical properties, and flight ability. Mechanics experiments were performed on fibres dissected from 2-h-old adult flies, prior to degradation of IFM myofilament structure, which started at 2 days old and increased with age. Homozygous and heterozygous R249Q fibres showed decreased maximum power generation by 67% and 44%, respectively. Decreases in force and work and slower overall muscle kinetics caused homozygous fibres to produce less power. While heterozygous fibres showed no overall slowing of muscle kinetics, active force and work production dropped by 68% and 47%, respectively, which hindered power production. The muscle apparent rate constant 2πb decreased 33% for homozygous but increased for heterozygous fibres. The apparent rate constant 2πc was greater for homozygous fibres. This indicates that R249Q myosin is slowing attachment while speeding up detachment from actin, resulting in less time bound. Decreased IFM power output caused 43% and 33% decreases in Drosophila flight ability and 19% and 6% drops in wing beat frequency for homozygous and heterozygous flies, respectively. Overall, our results do not support the increased contractility hypothesis. Instead, our results suggest the ventricular hypertrophy for human R249Q mutation is a compensatory response to decreases in heart muscle power output.

Do repeat ultrasounds affect orchiectomy rate in patients with testicular torsion treated at a pediatric institution?

INTRODUCTION

Testicular torsion is a urological emergency; as the testicular salvage rate decreases with time, prompt intervention is required to restore the blood flow. Interhospital transfers and ultrasound examinations, while clinically essential to proper treatment and diagnosis, may adversely affect outcomes by delaying surgical intervention. Patients transferred to another institution for treatment of testicular torsion may experience a further time delay by undergoing two ultrasound examinations: one at the initial admitting institution and one at the receiving institution. To the knowledge of the authors, no study has yet explored the time delays and outcomes associated with these repeat ultrasounds.

OBJECTIVE

The objective was to investigate the impact of repeat ultrasound imaging on time to treatment and patient outcomes in patients with testicular torsion.

STUDY DESIGN

A retrospective chart review of 133 patients, aged 0-20 years, treated at the authors' institution for testicular torsion was conducted. Neonate patients and patients who did not receive ultrasound were excluded. Demographic and clinical variables were collected from the electronic medical record. Pearson Chi-squared and t-tests were used for univariate comparisons, and multivariate logistic regression analysis was performed to measure the relationships between variables.

RESULTS

Forty-nine percent of patients were primary patients, and 51% were transfer patients. Fifty-two percent of transfer patients received repeat ultrasounds. In comparison to salvaged patients, those who underwent orchiectomy experienced a greater delay between presentation at the institution and surgical intervention (229 min vs 177 min, p = 0.048). The transfer status does not appear to be related to the outcome, i.e. orchiectomy versus salvage. Patients who underwent orchiectomy were more likely than salvaged patients to have received repeat ultrasounds (p = 0.008). Repeat ultrasound patients had three times the likelihood of orchiectomy of single ultrasound patients. In a subset analysis of transfer patients, repeat ultrasound patients were more likely than single ultrasound patients to receive an orchiectomy (p = 0.03).

DISCUSSION

In agreement with previous studies, patients who underwent orchiectomy were found to experience greater treatment delays and trend toward transfer. Specifically, repeat ultrasound and time between presentation and intervention appear to influence patient outcomes. The effect of repeat ultrasound on outcomes appears to be independent of the transfer status. The study was limited by its retrospective nature and small sample size.

CONCLUSION

The analysis suggests that efforts to prevent repeat ultrasounds and minimize the time between presentation and intervention would improve patient outcomes. It is proposed that standardized clinical decision-making procedures, such as the TWIST scoring system, be incorporated into hospital protocols.

Randomized equivalence trial of the King Vision aBlade videolaryngoscope with the Miller direct laryngoscope for routine tracheal intubation in children <2 yr of age

Background.

We conducted a randomized equivalence trial to compare direct laryngoscopy using a Miller blade (DL) with the King Vision videolaryngoscope (KVL) for routine tracheal intubation. We hypothesized that tracheal intubation times with DL would be equivalent to the KVL in children <2 yr of age.

Methods.

Two hundred children were randomly assigned to tracheal intubation using DL or KVL. The primary outcome was the median difference in the total time for successful tracheal intubation. Secondary outcomes assessed were tracheal intubation attempts, time to best glottic view, time for tracheal tube entry, percentage of glottic opening score, airway manoeuvres needed, and complications.

Results.

The median difference between the groups was 5.7 s, with an upper 95% confidence interval of 7.5 s, which was less than our defined equivalence time difference of 10 s. There were no differences in the number of tracheal intubation attempts and the time to best glottic view [DL median 5.3 (4.1-7.6) s vs KVL 5.0 (4.0-6.3) s; P =0.19]. The percentage of glottic opening score was better when using the KVL [median 100 (100-100) vs DL median 100 (90-100); P <0.0001]. Use of DL was associated with greater need for airway manoeuvres during tracheal intubation (33 vs 7%; P <0.001). Complications did not differ between devices.

Conclusions.

In children <2 yr of age, the KVL was associated with equivalent times for routine tracheal intubation when compared with the Miller blade.

Clinical trial registration

NCT02590237.

Prolonged cross-bridge binding triggers muscle dysfunction in a Drosophila model of myosin-based hypertrophic cardiomyopathy

K146N is a dominant mutation in human β-cardiac myosin heavy chain, which causes hypertrophic cardiomyopathy. We examined how Drosophila muscle responds to this mutation and integratively analyzed the biochemical, physiological and mechanical foundations of the disease. ATPase assays, actin motility, and indirect flight muscle mechanics suggest at least two rate constants of the cross-bridge cycle are altered by the mutation: increased myosin attachment to actin and decreased detachment, yielding prolonged binding. This increases isometric force generation, but also resistive force and work absorption during cyclical contractions, resulting in decreased work, power output, flight ability and degeneration of flight muscle sarcomere morphology. Consistent with prolonged cross-bridge binding serving as the mechanistic basis of the disease and with human phenotypes, 146N/+ hearts are hypercontractile with increased tension generation periods, decreased diastolic/systolic diameters and myofibrillar disarray. This suggests that screening mutated Drosophila hearts could rapidly identify hypertrophic cardiomyopathy alleles and treatments.

Myosin is a motor protein that drives the contraction of muscles. Filaments made from myosin molecules slide between filaments of another protein called actin, tugging the edges of the muscle cell inwards. To achieve this, part of each motor protein – called the 'head' – grabs hold of actin and uses energy to pull on the filaments.

Small genetic mutations in the gene for myosin can change the shape of the protein. This can change the way that it interacts with actin, altering the molecular machinery that makes muscles contract. In some cases, gene errors can cause the heart muscle wall to thicken, a condition called hypertrophic cardiomyopathy. Mapping the locations of known mutations revealed 'hot spots' on the myosin protein where these errors are likely to cause disease. These include the part of the molecule that swings the myosin heads, and the heads themselves.

It only takes a change to a single letter in the DNA code to thicken the heart wall, but the impact of each possible change is not yet known. Kronert et al. have now genetically modified fruit flies to give them one of the mutations that causes thickening of the heart wall in humans. The mutation, known as K146N, does not appear in one of the well-known 'hot spots'. The experiments revealed that the mutation causes myosin to remain attached to actin for longer than normal. This increased the amount of force the myosin generated, but slowed down actin movement, causing muscle stiffness. This resulted in less power for every cycle of muscle movement, and caused the muscles to degenerate over time. As a result, the flies were less able to use their wings, and their hearts pumped less well.

Hypertrophic cardiomyopathy can cause death in young adults, particularly competitive athletes. Yet studying the disease in humans is challenging. Recreating myosin mutations in fruit flies provides a way to study hypertrophic cardiomyopathy in the laboratory. In the future, extensions to this technique could allow researchers to examine the impact of other mutations. Models like this one could also allow early testing of new drugs or genetic treatments to repair faulty myosin molecules.

Prediction of Borderzone Infarction by CTA in Patients Undergoing Carotid Embolization for Carotid Blowout

BACKGROUND AND PURPOSE

Permanent common carotid artery and/or ICA occlusion is an effective treatment for carotid blowout syndrome. Besides postoperative thromboembolic infarction, permanent common carotid artery and/or ICA occlusion may cause borderzone infarction when the collateral flow to the deprived brain territory is inadequate. In this study, we aimed to test the predictive value of CTA for post-permanent common carotid artery and/or ICA occlusion borderzone infarction in patients with carotid blowout syndrome.

MATERIALS AND METHODS

In this retrospective study, we included 31 patients undergoing unilateral permanent common carotid artery and/or ICA occlusion for carotid blowout syndrome between May 2009 and December 2016. The vascular diameter of the circle of Willis was evaluated using preprocedural CTA, and the risk of borderzone infarction was graded as very high risk, high risk, intermediate risk, low risk, and very low risk.

RESULTS

The performance of readers' consensus on CTA for predicting borderzone infarction was excellent, with an area under receiver operating characteristic curve of 0.938 (95% confidence interval, 0.85-1.00). We defined very high risk, high risk, and intermediate risk as positive for borderzone infarction, the sensitivity, specificity, positive predictive value, and negative predictive value of CTA for borderzone infarction were 100% (7/7), 62.5% (15/24), 43.8% (7/16), and 100% (15/15), respectively. The interobserver reliability was excellent (κ = 0.807). No significant difference in the receiver operating characteristic curves was found between the 2 readers (P = .114).

CONCLUSIONS

CTA can be used to predict borderzone infarction after permanent common carotid artery and/or ICA occlusion by measuring the collateral vessels of the circle of Willis.

Changes and analysis of anti-HBs titres after primary immunization in 1- to 16-year-old Chinese children: A hospital-based study

Immunization with the hepatitis B vaccine is the most effective measure to prevent Hepatitis B Virus (HBV) infection. The aim of this study was to investigate the change in antibody levels induced by administration of the hepatitis B vaccine in children aged 1-16 year old in a large sample sized investigation. HBV markers were determined in 93 326 1- to 16-year-old hospitalized children who completed primary immunization as infants from south-west China, Chongqing. Analyses were performed on anti-HBs titre changes with increasing age, and the revaccination effect was evaluated in children aged 7-14. The percentage of protective antibody was between 45.29% and 63.33% in all age groups, but was higher in the 1-, 2- and 3-year-old groups (90.31%, 83.95% and 71.82%, respectively), and the rate of high-responder was 5.03%-10.56%, except in the 1-year-old group (23.33%). Additionally, 3.33%-25.79% of subjects had not seroconverted. There was no significant difference in antibody levels between girls and boys (P > .05). The Geometric Mean Titers in children with confirmed revaccination history were significantly higher than those with unknown or no revaccination history (P < .0001). In conclusion, the overall rate of protective anti-HBs was 67.10% with consecutive age groups from 1 to 16, it decreased from 90.31% to 45.29% for 1- to 8-year-old individuals, and interestingly, the rate increased from 45.46% to 63.33% for subjects aged 9-15. Anti-HBs titres were significantly improved after revaccination. Booster doses are recommended for those without seroconversion, especially children who live in school with other students or have family members with positive HBsAg.