Antibody dynamics to SARS-CoV-2 in asymptomatic COVID-19 infections

Background

The missing asymptomatic COVID-19 infections have been overlooked because of the imperfect sensitivity of the nucleic acid testing (NAT). Globally understanding the humoral immunity in asymptomatic carriers will provide scientific knowledge for developing serological tests, improving early identification, and implementing more rational control strategies against the pandemic.

Measure

Utilizing both NAT and commercial kits for serum IgM and IgG antibodies, we extensively screened 11 766 epidemiologically suspected individuals on enrollment and 63 asymptomatic individuals were detected and recruited. Sixty-three healthy individuals and 51 mild patients without any preexisting conditions were set as controls. Serum IgM and IgG profiles were further probed using a SARS-CoV-2 proteome microarray, and neutralizing antibody was detected by a pseudotyped virus neutralization assay system. The dynamics of antibodies were analyzed with exposure time or symptoms onset.

Results

A combination test of NAT and serological testing for IgM antibody discovered 55.5% of the total of 63 asymptomatic infections, which significantly raises the detection sensitivity when compared with the NAT alone (19%). Serum proteome microarray analysis demonstrated that asymptomatics mainly produced IgM and IgG antibodies against S1 and N proteins out of 20 proteins of SARS-CoV-2. Different from strong and persistent N-specific antibodies, S1-specific IgM responses, which evolved in asymptomatic individuals as early as the seventh day after exposure, peaked on days from 17 days to 25 days, and then disappeared in two months, might be used as an early diagnostic biomarker. 11.8% (6/51) mild patients and 38.1% (24/63) asymptomatic individuals did not produce neutralizing antibody. In particular, neutralizing antibody in asymptomatics gradually vanished in two months.

Conclusion

Our findings might have important implications for the definition of asymptomatic COVID-19 infections, diagnosis, serological survey, public health, and immunization strategies.

     

肺炎克雷伯杆菌在T24细胞内存活的动态观察

目的：了解肺炎克雷伯杆菌与膀胱上皮细胞的相互关系，观察肺炎克雷伯杆菌在人膀胱上皮细胞抹T24中生存的动态变化。方法：采用肺炎克雷伯杆菌临床分离抹03138侵袭T24细胞，并用庆大霉素杀死细胞外的细菌，分别于细菌进入细胞后的4、24、48及72h裂解细胞，释放出细胞内的活细菌，用平板菌落计数法计数胞内活菌数。结果：T24细胞内的肺炎克雷伯杆菌03138抹在实验48h内有一定生长，试验72h细胞内活菌数量明显减少。加入细胞因子（TNF-αd和INF-γ）可以促进上皮细胞清除胞内细菌。结论：膀胱上皮细胞清除进入细胞内的肺炎克雷伯杆菌，可能是泌尿道天然免疫的一种防御机制，而细胞因子可以调控上皮细胞的抗菌作用。     

Involvement of protein kinase C in HIV-1 gp120-induced apoptosis in primary endothelium

We previously showed that HIV-1 gp120-induced apoptosis in primary human umbilical vein endothelial cell cultures (HUVEC), through CCR5 and CXCR4. Here, we have found that agonists of protein kinase C (PKC), basic fibroblast growth factor (bFGF), and short exposure to low concentrations of phorbol esters were found to block gp120-induced apoptosis in HUVEC cultures. PKC antagonists, sphingosine, H7, and extended exposure of cultures to high concentrations of phorbol esters were also found to block gp120-induced apoptosis in HUVEC cultures. A significant increase in the total amount of cellular PKC enzymatic activity was observed on exposure of HUVEC to gp120. No increase in total PKC activity was observed on exposure of HUVECs to the natural ligands SDF-1alpha, or regulated-on-activation normal T-expressed and secreted (RANTES) cells, and gp120-induced PKC induction was found to be totally blocked by CXCR4 antibodies and partially blocked by the caspase 3 inhibitor, DEVD-CHO. Alternatively, CXCR4 antibodies and DEVD-CHO totally blocked apoptosis. Finally, gp120-induced effects were found to be insensitive to pertussis toxin. Accumulated evidence suggests PKC involvement at multiple points in the gp120-induced apoptotic pathway; also suggests involvement of the CXCR4 receptor internalization pathway, and potentially suggests different downstream effects of gp120-receptor interactions and natural ligand-receptor interactions.     

脑白质疏松症患者的诱发电位研究

对２４例经颅脑ＣＴ证实的脑白质疏松症患者进行脑干听觉诱发电位（ＢＡＥＰ）和短潜伏期体感觉诱发电位（ＳＥＰ）检查，结果ＢＥＡＰ总异常率７９％，ＳＥＰ总异常率８３％，两种诱发电位均以时间参数的异常率明显比波幅度参数的异常率高。结论：在脑白质疏松症的临床早期，虽然还未出现典型的临床表现，但脑电生理已出现异常，诱发电位的检测可以作为早期诊断该病的一个敏感的辅助检测方法。     

Induction of cyclooxygenase-2 mRNA and protein expression by dentin bonding agents in human gingival fibroblasts

An ideal dentin bonding agent should be nonirritating to surrounding tissues. Unfortunately, all histological investigations have demonstrated that dentin bonding agents can induce mild to severe inflammatory alterations. However, there is little information on the precise mechanisms about dentin bonding agents-induced inflammatory reaction. Cyclooxygenase-2 (COX-2) is an inducible enzyme believed to be responsible for prostaglandin synthesis at the site of inflammation. The aim of the present study was to investigate the effects of three dentin bonding agents, Clearfil SE Bond, Prime & Bond NT, and Single Bond on the expression of COX-2 mRNA gene and protein in cultured human gingival fibroblasts. The exposure of quiescent human gingival fibroblasts to dentin bonding agents resulted in the induction of COX-2 mRNA expression. The investigations of the time-dependent on COX-2 mRNA expression in dentin bonding agent-treated human gingival fibroblasts revealed different patterns. The influence of COX-2 mRNA depended on the tested materials. In addition, all dentin bonding agents also induced COX-2 protein expression in human gingival fibroblasts. Taken together, the activation of COX-2 expression may be one of the potential mechanisms of dentin bonding agent-induced gingival inflammation.     

Evidence for a major gene underlying bone size variation in the Chinese

Osteoporosis is a major public health problem defined as a loss of bone strength, of which bone size is an important determinant. In the present study, familial correlation and segregation analyses for the spine and hip bone sizes were performed for the first time in a Chinese sample composed of 393 nuclear families with a total of 1,193 individuals. The results indicate a major gene of codominant inheritance for spine bone size; however, there is no evidence of a major gene influencing hip bone size. Significant familial residual effects are found for both traits, suggesting their polygenic inheritance. Heritability estimates (±SE) for spine and hip bone size were 0.62 (0.13) and 0.59 (0.12), respectively. Sex and age differences in genotype‐specific average bone size were observed. Compared with our previous study on bone mineral density (BMD) in the same population, this study suggests that genetic determination of bone size may be different from that of BMD, and thus studying bone size as one surrogate phenotype for osteoporotic fractures may be necessary. Am. J. Hum. Biol. 16:68–77, 2004. © 2003 Wiley‐Liss, Inc.     

Electrogram prolongation and nifedipine-suppressible ventricular arrhythmias in mice following targeted disruption of KCNE1

Mutations in KCNE1 , the gene encoding the β subunit of the slowly activating delayed rectifier potassium current ( I _Ks) channel protein, may lead to the long QT syndrome (LQTS), a condition associated with enhanced arrhythmogenesis. Mice with homozygous deletion of the coding sequence of KCNE1 have inner ear defects strikingly similar to those seen in the corresponding human condition. The present study demonstrated and assessed the mechanism of ventricular arrhythmias in Langendorff-perfused whole heart preparations from homozygous KCNE1-/- mice compared to wild-type mice of the same age. The effects of programmed electrical stimulation with decremental pacing from the basal right ventricular epicardial surface upon electrogram waveforms recorded from the basal left ventricle were assessed and quantified using techniques of paced electrogram fractionation analysis for the first time in an experimental system. All KCNE1-/-( n = 10) but not wild-type ( n = 14) mouse hearts empirically demonstrated marked pacing-induced ventricular arrhythmogenicity. This correlated with significant increases in electrogram dispersion, consistent with a wider spread in conduction velocities, in parallel with clinical findings from LQTS patients with potassium channel mutations. In contrast, introduction of 100 nM isoprenaline induced arrhythmogenicity in both KCNE1-/- ( n = 7) and wild-type ( n = 6) hearts during pacing. Furthermore, pretreatment with 1 μM nifedipine exerted a strong anti-arrhythmic effect in the KCNE1-/- hearts ( n = 12) that persisted even in the presence of 100 nM isoprenaline ( n = 6). Our findings associate KCNE1-/- with an arrhythmogenic phenotype that shows an increased dispersion of conduction velocities, and whose initiation is prevented by nifedipine, a finding that in turn may have therapeutic applications in conditions such as LQTS.     

Clinical features and complications of viridans streptococci bloodstream infection in pediatric hemato-oncology patients.

BACKGROUND AND PURPOSE: Viridans streptococci (VS) are part of the normal flora of humans, but are fast emerging as pathogens causing bacteremia in neutropenic patients. The clinical features, outcomes, and antibiotic susceptibilities of VS bloodstream infections in children with hemato-oncological diseases are reported in this study. METHODS: A retrospective chart review of pediatric patients (< or =18 years) diagnosed with VS infections between January 1998 and December 2004 was conducted at the National Taiwan University Hospital. RESULTS: Among the 26 episodes noted in 25 pediatric patients, the incidence rate of VS bacteremia was found to be significantly higher in pediatric patients with acute myeloid leukemia compared with other hemato-oncological conditions. Most of the patients had profound neutropenia related to chemotherapy for a median of 5 days on the day of positive blood culture. Eight of the 25 patients had undergone stem cell transplantations. Streptococcus mitis was the most common bloodstream isolate and only 12 (44%) of the 27 isolated strains of VS were penicillin-susceptible. Empirical antibiotic treatments were not effective in half of the episodes, but did not affect overall mortality. Isolated bacteremia (63%) and pneumonia (22%) were the two leading clinical presentations. Complications were recognized more frequently in patients with pneumonia. Hypotension and mechanical ventilation each developed in 8 patients (31%). The overall mortality rate was 23%. CONCLUSIONS: Penicillin non-susceptible VS infection has emerged as a threat in children with hemato-oncological diseases, especially those with acute myeloid leukemia. S. mitis is the most common spp. of VS causing bacteremia in children and is associated with serious complications. The development of pneumonia resulted in clinical complications and higher mortality. Empirical antibiotic treatments with activity against the infecting strains did not reduce the overall mortality rate in this study.     

在戊四氮致痫大鼠早期前脑中OX-42和Fos蛋白的表达变化

研究大鼠在戊四氮导致癫痫发作早期前脑内小胶质细胞的变化及其与神经元的关系,本研究应用免疫组织化学法分别显示前脑内OX-42和Fos蛋白表达的时程变化,并用双重标记显示OX-42和Fos阳性细胞的相互关系。结果发现:在戊四氮导致大鼠癫痫发作早期(从15min到360min),前脑的小胶质细胞OX-42表达阳性,随着存活时间的变化,OX-42的阳性反应经历逐渐升高又降低的过程;Fos蛋白在神经元和小胶质细胞中有表达,也呈现逐渐升高又降低的变化;Fos在小胶质细胞表达高峰的时间早于在神经元的表达;另外OX-42阳性小胶质细胞和Fos阳性神经元在前脑分布基本相同,主要分布在大脑皮层、海马、杏仁核等部位。以上结果表明,前脑的小胶质细胞和神经元一样在戊四氮所致癫痫发作的早期表现明显的反应,但小胶质细胞反应的意义有待进一步研究。