Performance of 20 rapid antigen detection tests to detect SARS-CoV-2 B.1.617.2 (Delta) and B.1.1.529 (Omicron) variants using a clinical specimen panel from January 2022, Berlin, Germany.

BackgroundThere are conflicting reports on the performance of rapid antigen detection tests (RDT) in the detection of the SARS-CoV-2 Omicron (B.1.1.529) variant; however, these tests continue to be used frequently to detect potentially contagious individuals with high viral loads.AimThe aim of this study was to investigate comparative detection of the Delta (B.1.617.2) and Omicron variants by using a selection of 20 RDT and a limited panel of pooled combined oro- and nasopharyngeal clinical Delta and Omicron specimens.MethodsWe tested 20 CE-marked RDT for their performance to detect SARS-CoV-2 Delta and Omicron by using a panel of pooled clinical specimens collected in January 2022 in Berlin, Germany.ResultsWe observed equivalent detection performance for Delta and Omicron for most RDT, and sensitivity was widely in line with our previous pre-Delta/Omicron evaluation. Some variation for individual RDT was observed either for Delta vs Omicron detection, or when compared with the previous evaluation, which may be explained both by different panel sizes resulting in different data robustness and potential limitation of batch-to-batch consistency. Additional experiments with three RDT using non-pooled routine clinical samples confirmed comparable performance to detect Delta vs Omicron. Overall, RDT that were previously positively evaluated retained good performance also for Delta and Omicron variants.ConclusionOur findings suggest that currently available RDT are sufficient for the detection of SARS-CoV-2 Delta and Omicron variants.

Virus-Specific Stem Cell Memory CD8+ T Cells May Indicate a Long-Term Protection against Evolving SARS-CoV-2.

Immune memory to SARS-CoV-2 is key for establishing herd immunity and limiting the spread of the virus. The duration and qualities of T-cell-mediated protection in the settings of constantly evolving pathogens remain an open question. We conducted a cross-sectional study of SARS-CoV-2-specific CD4+ and CD8+ T-cell responses at several time points over 18 months (30-750 days) post mild/moderate infection with the aim to identify suitable methods and biomarkers for evaluation of long-term T-cell memory in peripheral blood. Included were 107 samples from 95 donors infected during the periods 03/2020-07/2021 and 09/2021-03/2022, coinciding with the prevalence of B.1.1.7 (alpha) and B.1.617.2 (delta) variants in Bulgaria. SARS-CoV-2-specific IFNγ+ T cells were measured in ELISpot in parallel with flow cytometry detection of AIM+ total and stem cell-like memory (TSCM) CD4+ and CD8+ T cells after in vitro stimulation with peptide pools corresponding to the original and delta variants. We show that, unlike IFNγ+ T cells, AIM+ virus-specific CD4+ and CD8+ TSCM are more adequate markers of T cell memory, even beyond 18 months post-infection. In the settings of circulating and evolving viruses, CD8+ TSCM is remarkably stable, back-differentiated into effectors, and delivers immediate protection, regardless of the initial priming strain.

Clinical and baseline computed tomography features of patients infected with the B.1.617.2 (Delta) variant of severe acute respiratory syndrome coronavirus 2

PURPOSE: The purpose of this study was to investigate the clinical and baseline computed tomography (CT) features and their correlation in patients infected with the B.1.617.2 (Delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). MATERIALS AND METHODS: Clinical and chest baseline CT data of patients infected with the Delta variant of SARS-CoV-2 from July to August 2021 were collected. First, the correlation between the clinical data and baseline CT results was analyzed according to CT positivity or negativity. Then, subgroup analysis was performed between different age distributions and clinical characteristics. Next, the CT characteristics and clinical data of all baseline CT-positive patients were collected, and the correlations between CT characteristics and age, vaccination status, and chronic disease were analyzed. Lesions in patients with baseline CT positivity were evaluated by semi-quantitative scoring to analyze the correlations between the semi-quantitative scores and vaccination status and age distribution. RESULTS: A total of 221 nucleic acid-positive patients with the SARS-CoV-2 Delta variant were included, of whom 107 patients were baseline CT positive and 114 were baseline CT negative. Baseline CT positivity was associated with age distribution, and baseline CT positivity was most common in patients aged >60 years (P < 0.001), but not with vaccination status or gender. The results of the subgroup analysis according to age distribution indicated that different age distribution subgroups had different vaccination statuses, and the majority of patients aged <18 years and >60 years were unvaccinated (90.5%, 19/21, and 57.3%, 63/110, respectively). In contrast, most patients aged 18–60 years had received two doses of the vaccine (61.1%, 55/90) (P < 0.001). Different age distribution subgroups had different clinical infection types. Asymptomatic and mild cases were most common in patients aged ≤60 years, and moderate and severe or critical cases were most common in patients aged >60 years. For baseline CT-positive patients, the extent of lung involvement was associated with age, vaccination status, and chronic disease. The number of involved lobes was higher in patients who were unvaccinated or who had received one injection, who were aged >60 years or had chronic disease. There was a statistical difference in CT semi-quantitative scores between the different age subgroups. Compared with patients aged < 60 years, patients aged >60 years had higher semi-quantitative scores (P < 0.001). However, there was no statistical difference between the different vaccination groups. CONCLUSIONS: Age had a large effect on baseline CT positivity, CT characteristics, and semi-quantitative CT scores in patients infected with the Delta variant.

COVID-19 Vaccine Initiation and Dose Completion During the SARS-CoV-2 Delta Variant Surge in the United States, December 2020-October 2021.

OBJECTIVES: In summer 2021, the number of COVID-19-associated hospitalizations in the United States increased with the surge of the SARS-CoV-2 Delta variant. We assessed how COVID-19 vaccine initiation and dose completion changed during the Delta variant surge, based on jurisdictional vaccination coverage before the surge. METHODS: We analyzed COVID-19 vaccination data reported to the Centers for Disease Control and Prevention. We classified jurisdictions (50 states and the District of Columbia) into quartiles ranging from high to low first-dose vaccination coverage among people aged ≥12 years as of June 30, 2021. We calculated first-dose vaccination coverage as of June 30 and October 31, 2021, and stratified coverage by quartile, age (12-17, 18-64, ≥65 years), and sex. We assessed dose completion among those who initiated a 2-dose vaccine series. RESULTS: Of 51 jurisdictions, 15 reached at least 70% vaccination coverage before the Delta variant surge (ie, as of June 30, 2021), while 35 reached that goal as of October 31, 2021. Jurisdictions in the lowest quartile of vaccination coverage (44.9%-54.9%) had the greatest absolute (9.7%-17.9%) and relative (18.1%-39.8%) percentage increase in vaccination coverage during July 1-October 31, 2021. Of those who received the first dose during this period across all jurisdictions, nearly 1 in 5 missed the second dose. CONCLUSIONS: Although COVID-19 vaccination initiation increased during July 1-October 31, 2021, in jurisdictions in the lowest quartile of vaccination coverage, coverage remained below that of jurisdictions in the highest quartile of vaccination coverage before the Delta variant surge. Efforts are needed to improve access to and increase confidence in COVID-19 vaccines, especially in low-coverage areas.

Dynamic characteristics of a COVID-19 outbreak in Nanjing, Jiangsu province, China.

Objectives: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lineage B.1.617.2 (also named the Delta variant) was declared as a variant of concern by the World Health Organization (WHO). This study aimed to describe the outbreak that occurred in Nanjing city triggered by the Delta variant through the epidemiological parameters and to understand the evolving epidemiology of the Delta variant. Methods: We collected the data of all COVID-19 cases during the outbreak from 20 July 2021 to 24 August 2021 and estimated the distribution of serial interval, basic and time-dependent reproduction numbers (R0 and Rt), and household secondary attack rate (SAR). We also analyzed the cycle threshold (Ct) values of infections. Results: A total of 235 cases have been confirmed. The mean value of serial interval was estimated to be 4.79 days with the Weibull distribution. The R0 was 3.73 [95% confidence interval (CI), 2.66-5.15] as estimated by the exponential growth (EG) method. The Rt decreased from 4.36 on 20 July 2021 to below 1 on 1 August 2021 as estimated by the Bayesian approach. We estimated the household SAR as 27.35% (95% CI, 22.04-33.39%), and the median Ct value of open reading frame 1ab (ORF1ab) genes and nucleocapsid protein (N) genes as 25.25 [interquartile range (IQR), 20.53-29.50] and 23.85 (IQR, 18.70-28.70), respectively. Conclusions: The Delta variant is more aggressive and transmissible than the original virus types, so continuous non-pharmaceutical interventions are still needed.

SARS-CoV-2 B.1.214.1, B.1.214.2 and B.1.620 are predominant lineages between December 2020 and July 2021 in the Republic of Congo.

Background: : SARS-CoV-2 variants have been emerging and are shown to increase transmissibility, pathogenicity, and decreased vaccine efficacies. The objective of this study was to determine the distribution, prevalence, and dynamics of SARS-CoV-2 variants circulating in Brazzaville, the Republic of Congo (ROC). Methods: : Between December 2020 and July 2021, a total of n=600 oropharyngeal specimens collected in the community were tested for COVID-19. Of the samples tested, 317 (53%) were SARS-CoV-2 positive. All samples that had a threshold of Ct <30 (n=182) were sequenced by next-generation sequencing (NGS), and all complete sequenced genomes were submitted to GISAID; lineages were assigned using pangolin nomenclature and a phylogenetic tree was reconstructed. In addition, the global prevalence of the predominant lineages was analysed using data from GISAID and Outbreak databases. Results: : A total of 15 lineages circulated with B.1.214.2 (26%), B.1.214.1 (19%) and B.1.620 (18%) being predominant. The variants of concern (VOC) alpha (B.1.1.7) (6%) and for the first time in June delta (B.1.617.2) (4%) were observed. In addition, the B.1.214.1 lineage first reported from ROC was observed to be spreading locally and regionally. Phylogenetic analysis suggests that the B.1.620 variant (VUM) under observation may have originated from either Cameroon or the Central African Republic. SARS-CoV-2 lineages were heterogeneous, with the densely populated districts of Poto-Poto and Moungali likely the epicenter of spread. Conclusion: : Longitudinal monitoring and molecular surveillance across time and space are critical to understanding viral phylodynamics, which could have important implications for transmissibility and impact infection prevention and control measures.

Case series in Indonesia: B.1.617.2 (delta) variant of SARS-CoV-2 infection after a second dose of vaccine.

BACKGROUND: The B.1.617.2 (delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first discovered in Maharashtra in late 2020 and has rapidly expanded across India and worldwide. It took only 2 mo for this variant to spread in Indonesia, making the country the new epicenter of the delta variant as of July 2021. Despite efforts made by accelerating massive rollouts of current vaccines to protect against infection, cases of fully-vaccinated people infected with the delta variant have been reported. AIM: To describe the demographic statistics and clinical presentation of the delta variant infection after the second dose of vaccine in Indonesia. METHODS: A retrospective, single-centre case series of the general consecutive population that worked or studied at Faculty of Medicine, Universitas Indonesia with confirmed Delta Variant Infection after a second dose of vaccine from 24 June and 25 June 2021. Cases were collected retrospectively based on a combination of author recall, reverse transcription-polymerase chain reaction (RT-PCR), and whole genome sequencing results from the Clinical Microbiology Laboratory, Faculty of Medicine, Universitas Indonesia. RESULTS: Between 24 June and 25 June 2021, 15 subjects were confirmed with the B.1.617.2 (delta) variant infection after a second dose of the vaccine. Fourteen subjects were vaccinated with CoronaVac (Sinovac) and one subject with ChAdOx1 nCoV-19 (Oxford-AstraZeneca). All of the subjects remained in home isolation, with fever being the most common symptom at the onset of illness (n = 10, 66.67%). The mean duration of symptoms was 7.73 d (± 5.444). The mean time that elapsed from the first positive swab to a negative RT-PCR test for SARS-CoV-2 was 17.93 d (± 6.3464). The median time that elapsed from the second dose of vaccine to the first positive swab was 87 d (interquartile range: 86-128). CONCLUSION: Although this case shows that after two doses of vaccine, subjects are still susceptible to the delta variant infection, currently available vaccines remain the most effective protection. They reduce clinical manifestations of COVID-19, decrease recovery time from the first positive swab to negative swab, and lower the probability of hospitalization and mortality rate compared to unvaccinated individuals.

Mental health and chest CT scores mediate the relationship between COVID-19 vaccination status and seroconversion time: A cross-sectional observational study in B.1.617.2 (Delta) infection patients.

Background: The coronavirus disease (COVID-19) pandemic, which has been ongoing for more than 2 years, has become one of the largest public health issues. Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is one of the most important interventions to mitigate the COVID-19 pandemic. Our objective is to investigate the relationship between vaccination status and time to seroconversion. Methods: We conducted a cross-sectional observational study during the SARS-CoV-2 B.1.617.2 outbreak in Jiangsu, China. Participants who infected with the B.1.617.2 variant were enrolled. Cognitive performance, quality of life, emotional state, chest computed tomography (CT) score and seroconversion time were evaluated for each participant. Statistical analyses were performed using one-way ANOVA, univariate and multivariate regression analyses, Pearson correlation, and mediation analysis. Results: A total of 91 patients were included in the analysis, of whom 37.3, 25.3, and 37.3% were unvaccinated, partially vaccinated, and fully vaccinated, respectively. Quality of life was impaired in 30.7% of patients, especially for mental component summary (MCS) score. Vaccination status, subjective cognitive decline, and depression were risk factors for quality-of-life impairment. The chest CT score mediated the relationship of vaccination status with the MCS score, and the MCS score mediated the relationship of the chest CT score with time to seroconversion. Conclusion: Full immunization course with an inactivated vaccine effectively lowered the chest CT score and improved quality of life in hospitalized patients. Vaccination status could influence time to seroconversion by affecting CT score and MCS score indirectly. Our study emphasizes the importance of continuous efforts in encouraging a full vaccination course.

SARS-CoV-2 Mutations Responsible for Immune Evasion Leading to Breakthrough Infection.

BACKGROUND AND OBJECTIVES: India had faced a devastating second outbreak of COVID-19 infection, in which a majority of the viral sequences were found to be of the B.1.617.2 lineage (Delta-variant). While India and the world focused on vaccination, reports of vaccine-immunity evasion by the virus, termed "breakthrough cases", emerged worldwide. Our study was focused on the primary objective to identify the mutations associated with breakthrough infections SARS-CoV-2. METHODS: In our study, we extracted the SARS-CoV-2 RNA (ribonucleic acid) from reverse transcription-polymerase chain reaction (RT-PCR) positive COVID-19 patients, and 150 random samples were sent for sequencing to the Centre for Cellular & Molecular Biology, Hyderabad. Whole genome sequences of 150 SARS-CoV-2 viral samples were analyzed thoroughly. We mostly found B.1.617 and its sub-lineages in the genomic sequencing results. RESULTS AND INTERPRETATION: On further analysis of patient data, it was seen that nine patients had been vaccinated against the SARS-CoV-2 previously. These nine patients had B.1.617/B.1 or A strains, and all of them had similar genomic variations in spike proteins as well as non-structural proteins (NSPs). The mutations seen in these sequences in the Spike (S), NSPs, and open reading frame (ORF) regions would have produced amino acid changes known to improve viral replication, confer drug resistance, influence host-cell interaction, and lead to antigenic drift. CONCLUSIONS: Increased virulence culminating in vaccine immunity evasion may be inferred from these specific mutations. Our study adds to the growing body of evidence linking rapidly emerging mutations in the S (Spike) and ORF genes of the SARS-CoV-2 genome to immune evasion.

Delineating the Spread and Prevalence of SARS-CoV-2 Omicron Sublineages (BA.1-BA.5) and Deltacron Using Wastewater in the Western Cape, South Africa.

This study was one of the first to detect Omicron sublineages BA.4 and BA.5 in wastewater from South Africa. Spearman rank correlation analysis confirmed a strong positive correlation between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral RNA in wastewater samples and clinical cases (r = 0.7749, P < .0001). SARS-CoV-2 viral load detected in wastewater, resulting from the Delta-driven third wave, was significantly higher than during the Omicron-driven fourth wave. Whole-genome sequencing confirmed presence of Omicron lineage defining mutations in wastewater with the first occurrence reported 23 November 2021 (BA.1 predominant). The variant spread rapidly, with prevalence of Omicron-positive wastewater samples rising to >80% by 10 January 2022 with BA.2 as the predominant sublineage by 10 March 2022, whilst on 18 April 2022 BA.4 and BA.5 were detected in selected wastewater sites. These findings demonstrate the value of wastewater-based epidemiology to monitor the spatiotemporal spread and potential origin of new Omicron sublineages.

Dynamic characteristics of COVID-19 infection in Chinese children

From the start of the coronavirus disease 2019 (COVID-19) pandemic in 2020, COVID-19 infection in the pediatric population has aroused great attention. This article presents dynamic epidemiological characteristics of COVID-19 infection in pediatric patients from January 2020 to March 2022 in China. These data contributed essential insights and shared experience on the management of COVID-19 in children. To date, the unvaccinated population and events with children need more attention. Copyright © 2022 E-Century Publishing Corporation. All rights reserved.

Increased Mortality Among Persons With Symptomatic Coronavirus Disease 2019 (COVID-19) During the Period of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) B.1.617.2 (Delta Variant) Predominance: Alaska, November 2020-October 2021.

We compared the mortality risk in Alaska among persons with symptomatic coronavirus disease 2019 (COVID-19) during the period the Delta variant was predominant to the risk among those with symptomatic COVID-19 before Delta predominance. The Delta period was associated with 2.43-fold higher odds of death. Unvaccinated persons were 4.49 times more likely to die than fully vaccinated persons.

Increased pathogenicity and aerosol transmission for one SARS-CoV-2 B.1.617.2 Delta variant over the wild-type strain in hamsters.

During the two-year pandemic of coronavirus disease 2019 (COVID-19), its causative agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been evolving. SARS-CoV-2 Delta, a variant of concern, has become the dominant circulating strain worldwide within just a few months. Here, we performed a comprehensive analysis of a new B.1.617.2 Delta strain (Delta630) compared with the early WIV04 strain (WIV04) in vitro and in vivo, in terms of replication, infectivity, pathogenicity, and transmission in hamsters. When inoculated intranasally, Delta630 led to more pronounced weight loss and more severe disease in hamsters. Moreover, 40% mortality occurred about one week after infection with 104 PFU of Delta630, whereas no deaths occurred even after infection with 105 PFU of WIV04 or other strains belonging to the Delta variant. Moreover, Delta630 outgrew over WIV04 in the competitive aerosol transmission experiment. Taken together, the Delta630 strain showed increased replication ability, pathogenicity, and transmissibility over WIV04 in hamsters. To our knowledge, this is the first SARS-CoV-2 strain that causes death in a hamster model, which could be an asset for the efficacy evaluation of vaccines and antivirals against infections of SARS-CoV-2 Delta strains. The underlying molecular mechanisms of increased virulence and transmission await further analysis.

Clinical features and high-resolution chest computerized tomography findings of children infected by the B.1.617.2 variant of coronavirus disease 2019.

PURPOSE: To analyse the clinical symptoms, laboratory examinations and chest CT findings of children infected by the B.1.617.2 variant of COVID-19 and to compare the differences between clinical subtypes. METHODS: Fifty-three children (28 males, 25 females; age ranging from 4 months to 17 years) were included with B.1.617.2 variant infection in Nanjing, China, from July 21 to August 12 2021. Clinical data from patients were collected and analysed in groups of mild and common types. Imaging data were divided into three stages for evaluation: early, intermediate and late stages. RESULTS: In our study, fever (53%), cough (34%) and pharyngeal discomfort (28%) were the main symptoms. There were no differences in clinical symptoms between the mild and common type. The most common laboratory test items outside the normal range were decreased mean corpuscular volume (68%), lymphocyte percentage (64% elevated and 2% decreased) and decreased serum alkaline phosphatase concentration (66%). The differences in haemoglobin and monocyte percentages between the mild and common types were statistically significant (p = .037 and .033, respectively). No influencing factor was statistically significant in the regression analysis of both symptoms and clinical subtypes. The main CT findings were ground-glass opacity and consolidation located in the periphery and bilateral multilobed involvement. The mean CT score was 1.6. CT score correlated with packet cell volume, haemoglobin, mean erythrocyte volume, mean platelet volume and platelet distribution width. CONCLUSION: The pathogenetic condition of children with B.1.617.2 variant infection is mild. Although there were intergroup differences in some blood cell analyses, T-lymphocyte counts, and comprehensive biochemical indicators, no factors had a significant effect on clinical typing and the presence or absence of symptoms. CT findings and CT scores reflect disease stage and pathological changes and correlate moderately with laboratory tests, making them of good value for disease diagnosis and monitoring.Key MessagesPaediatric patients infected with B.1.617.2 variant have a milder clinical and imaging presentation than adults and are similar to the prototype infection.CT findings and scores which reflect disease stages and pathological changes.There is a correlation between chest CT and laboratory tests, which can be useful for the diagnosis and follow-up of the disease.

BNT162b2 Booster Vaccination Induced Immunity against SARS-CoV-2 Variants among Hemodialysis Patients.

Background: The emergence of new SARS-CoV-2 variants, which evade immunity, has raised the urgent need for multiple vaccine booster doses for vulnerable populations. In this study, we aimed to estimate the BNT162b2 booster effectiveness against the spread of coronavirus variants in a hemodialysis population. Methods: We compared humoral and cell-mediated immunity in 100 dialysis patients and 66 age-matched volunteers, before and 2-3 weeks following the first booster vaccine dose. Participants were assessed for anti-spike (RBD) antibody titer, neutralizing antibodies against B.1.617.2 (Delta) and B.1.1.529 (Omicron) variants, spike-specific T-cell responses by FACS and infection outbreak after the first and second booster. Results: Anti-spike antibody titer was significantly increased following the booster, with reduced humoral and cellular response in the dialysis patients. Neutralizing antibody levels increased significantly after the booster dose, with an inferior effect (≤2 fold) against Omicron compared with the Delta variant. Furthermore, CD4+ and CD8+ T-cell activation by Delta spike protein was preserved in 70% of PBMCs from the dialysis patients. A second booster dose tended to reduce breakthrough infections in the dialysis patients. Conclusions: Until the release of an updated vaccine, BNT162b2 booster doses will improve the humoral and cell-mediated immunity against variants. These findings support the importance of repetitive booster doses for hemodialysis patients.

Charge transport properties of SARS-CoV-2 Delta variant (B.1.617.2).

The B.1.617.2 (Delta) variant of concern is causing a new wave of infections in many countries. In order to better understand the changes of the SARS-CoV-2 mutation at the genetic level, we selected six mutations in the S region of the Delta variant compared with the native SARS-CoV-2 and get the conductance information of these six short RNA oligonucleotides groups by construct RNA: DNA hybrids. The electronic characteristics are investigated by the combination of density functional theory and non-equilibrium Green's function formulation with decoherence. We found that conductance is very sensitive to small changes in virus sequence. Among the 6 mutations in the Delta S region, D950N shows the largest change in relative conductance, reaching a surprising 4104.75%. These results provide new insights into the Delta variant from the perspective of its electrical properties. This may be a new method to distinguish virus variation and possess great research prospects.

Analysis of clinical characteristics of 66 pediatric patients with B.1.617.2 (Delta) variant of COVID-19.

BACKGROUND: The aim of this study was to analyze the clinical characteristics of 66 pediatric patients with B.1.617.2 (Delta) variant of coronavirus disease 2019 (COVID-19). METHODS: Sixty-six pediatric patients with B.1.617.2 (Delta) variant of COVID-19 admitted to the hospital from July to August 2021 were classified into mild (n = 41) and moderate groups (n = 25). Clinical characteristics, laboratory data and dynamic trends in different time periods were analyzed retrospectively. RESULTS: There were no statistically significant differences in age, gender ratios and clinical symptoms between the mild group and the moderate group. All the patients in the moderate group had clusters of onsets, and the incubation period was shorter than that of the mild group. Within 24 hours of admission, the levels of erythrocyte sedimentation rate, cardiac troponin I, D-dimer in the moderate group were higher than that in the mild group (P < 0.05). The titers of immunoglobulin (Ig) G and IgM antibodies gradually increased after disease onset. Thirty-five (53.03%) children were tested positive for antibodies in 4-12 days. IgG increased gradually, while IgM decreased obviously in about 15 days after disease onset. The cycle threshold values of open reading frame 1ab and nucleocapsid protein gene in the severe acute respiratory syndrome coronavirus 2 genomes increased gradually on the 3rd, 6th, 9th, and 12th days after disease onset, compared with those in day 0. CONCLUSIONS: The symptoms of children with B.1.617.2 (Delta) variant of COVID-19 were mild. The description and analysis of the clinical characteristics and laboratory data can help medical staff to evaluate the condition of children with COVID-19 and to accumulate more clinical experience.

Better binding informatics of delta variants (B.1.617.2) with ACE2 than wild, D614G or N501Y CoV-2 is fully blocked by 84 amino-acid cut of wild spike

Background and objective The B.1.617.2 known as the Delta-variant harbors diverse Spike-mutations with developed transmissibility and immune-evasion more than wild/D614G/N501Y variants. The Delta-variant claimed comparatively a large number of lives globally. In the present study, the binding-affinities of these variants’ spikes to the human lung-ACE2 were investigated. Further, a certain portion of the spike-protein with a desired mutation was tested in-silico to block the ACE2. Methods Structure of spike-variants were retrieved from PDB/GISAID and used for homology-modeling (SWISS-MODEL). A different combination of spike-ACE2 binding 1:1 or competitive blind-docking was performed using the Haddock 2.4 web-server. Eventually, two cut-segments (84 amino-acid of wild-spike, 432–516 Cut1) and its mutant T500S;Cut 2 were screened (Swiss-model Expasy-server) as blocker/inhibitor of all spike-variants (PyMOL-V2.2.2). Results It is shown that the stability and energy of the Delta binding-affinity to ACE2 is far more than others. The number H-bonding (5), their lengths (1.7 Å-2.8 Å) and energy, Van-der-Walls energy, Haddock-score were highly favorable for more stable-binding of Delta-RBD to ACE2. The Ramachandran-plot (Zlab/UMassMed Bioinfo) data supports this. We observed the best Haddock score as −120.8±2.6 for Delta with Van-der-Walls and electrostatic-energy as −62.9 and −208.7, respectively. The highest binding-affinity (ΔG) was −10.7 kcal/mol. Its THR500 and GLN506 strongly bind with the LYS353 of ACE2. The Cut1 and its mutant T500S completely blocked Delta-spike binding to ACE2 with ΔG -8.4 and −10.6 kcal/mol, respectively. But during the comparison between 2 Cuts, Cut1 showed better results. Conclusions Fractioned spike-protein from the conserved Receptor-Binding-Domain (RBD) could universally block the virus at entry-level, thus completely protecting any intercellular metabolism. Bioinformatics is an emerging field for screening of some drug/therapeutic targets from numerous options, minimizing time and expenses.

SARS-CoV-2 Variant Exposures Elicit Antibody Responses With Differential Cross-Neutralization of Established and Emerging Strains Including Delta and Omicron.

The wide spectrum of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants with phenotypes impacting transmission and antibody sensitivity necessitates investigation of immune responses to different spike protein versions. Here, we compare neutralization of variants of concern, including B.1.617.2 (delta) and B.1.1.529 (omicron), in sera from individuals exposed to variant infection, vaccination, or both. We demonstrate that neutralizing antibody responses are strongest against variants sharing certain spike mutations with the immunizing exposure, and exposure to multiple spike variants increases breadth of variant cross-neutralization. These findings contribute to understanding relationships between exposures and antibody responses and may inform booster vaccination strategies.