Computational Analysis of Mutations in the Receptor-Binding Domain of SARS-CoV-2 Spike and Their Effects on Antibody Binding

Currently, SARS-CoV-2 causing coronavirus disease 2019 (COVID-19) is responsible for one of the most deleterious pandemics of our time. The interaction between the ACE2 receptors at the surface of human cells and the viral Spike (S) protein triggers the infection, making the receptor-binding domain (RBD) of the SARS-CoV-2 S-protein a focal target for the neutralizing antibodies (Abs). Despite the recent progress in the development and deployment of vaccines, the emergence of novel variants of SARS-CoV-2 insensitive to Abs produced in response to the vaccine administration and/or monoclonal ones represent a potential danger. Here, we analyzed the diversity of neutralizing Ab epitopes and assessed the possible effects of single and multiple mutations in the RBD of SARS-CoV-2 S-protein on its binding affinity to various antibodies and the human ACE2 receptor using bioinformatics approaches. The RBD-Ab complexes with experimentally resolved structures were grouped into four clusters with distinct features at sequence and structure level. The performed computational analysis indicates that while single amino acid replacements in RBD may only cause partial impairment of the Abs binding, moreover, limited to specific epitopes, the variants of SARS-CoV-2 with multiple mutations, including some which were already detected in the population, may potentially result in a much broader antigenic escape. Further analysis of the existing RBD variants pointed to the trade-off between ACE2 binding and antigenic escape as a key limiting factor for the emergence of novel SAR-CoV-2 strains, as the naturally occurring mutations in RBD tend to reduce its binding affinity to Abs but not to ACE2. The results provide guidelines for further experimental studies aiming to identify high-risk RBD mutations that allow for an antigenic escape.     

异基因外周血造血干细胞移植41例临床分析

为分析异基因外周血造血干细胞移植（allo-PBSCT)治疗恶性血液病的效果和并发症的防治，用allo-PBSCT治疗恶性血液病41例，急性移植物抗宿主病（GVHD）预防采用环孢素A（CsA）＋短程氨甲蝶呤（MTX）、霉酚酸酯（MMF）联合CsA＋短程MTX两种方案。结果显示，全部患者均顺利造血重建。HLA完全相合移植急性GVHDⅡ度以上者8例（21．05％）。慢性GVHD发生率76％。急性白血病CR1和慢性髓细胞白血病－慢性期（CML－CP）、HLA完全相合移植34例，复发3例（8．82％）；随访2年以上者存活率71．43％（10／14）。表明allo－PBSCT急性GVHD发生率并不高于骨髓移植，但慢性GVHD发生率明显高；感染和间质性肺炎是移植后死亡的主要原因。     

造血干细胞移植术后患者巨细胞病毒感染发生率及临床转归

采用免疫组化法对100例异体造血干细胞移植（Allo-HSCT）和14例自体造血干细胞移植（Auto-HSCT)术后患者、17例非移植患者以及27例正常供者CMVpp6抗原血症检出率进行分析。100例Allo-HSCT术后患者随访观察18（4－36）个月。结果：AlloHSCT者91％，在不同病期出现CMVpp65阳性（CMV－I），其中56％出现CMV疾病；急性移植物抗宿主病（GVHD）发生率为54％，时间为25（11－27天）；慢性GVHD52.9%，CMV相关性死亡率为21％，在各种死因中占主要地位。CMV－I在异体移植后好发，而在AutoHSCT术后患者、非移植患者以及正常人群极为少见，提示，CMV感染与急慢性GVHD呈显著相关性，是影响预后的主要因素。     

基于肺与大肠相表里的针灸治疗变应性鼻炎肠道菌群研究进展

变应性鼻炎患病率较高,已成为全球性健康问题.针灸治疗变应性鼻炎具有副作用小、远期疗效好的特点,在临床已广泛应用.基于"肺与大肠相表里"理论综述了变应性鼻炎与肠道菌群及宿主免疫的关系、针灸调节变应性鼻炎相关肠道菌群及免疫的作用,揭示"肠道菌群-宿主免疫"可能成为针灸治疗变应性鼻炎的新靶点,以期为针灸治疗变应性鼻炎的机制研...     

Aggregatibacter actinomycetemcomitans–Induced Bone Loss and Antibody Response in Three Rat Strains

Background: The aim of this study is to compare the colonization, immunoglobulin (Ig) G response, and alveolar bone loss in Aggregatibacter actinomycetemcomitans (Aa)–inoculated Fawn Hooded Hypertensive (FHH), Dahl Salt‐Sensitive (DSS), and Brown Norway (BN) rats. Methods: Each rat strain was divided into wild‐type Aa‐inoculated and non‐inoculated control groups. Blood taken at 12 weeks after inoculation was assessed for Aa‐specific IgG antibodies by an enzyme‐linked immunosorbent assay. Colonization was assessed 12 weeks postinoculation. Bone loss was estimated by measuring the distance from the cemento‐enamel junction (CEJ) to the alveolar bone crest (ABC) at 20 molar sites. Colonization and antibody levels were compared by using the Student t test. Diseased rats were defined as having two sites per quadrant with CEJ–ABC distances that were significantly greater than the control CEJ–ABC distances. Results: The Aa colonization of FHH rats was significantly higher than in other strains (P <0.05). The Aa‐specific IgG levels in the DSS Aa‐inoculated group were significantly higher than in its control group (P <0.05). Only FHH rats showed Aa disease‐associated bone loss (P = 0.0021). Conclusions: Aa colonized and caused more disease in FHH rats than in the other rat strains. The rat strains each responded differently to the same Aa strain.     

Antimicrobial peptide LL-37 and its pro-form,hCAP18, in desquamated epithelial cells of human whole saliva

The antimicrobial peptide LL-37 is active against oral bacteria and has been demonstrated to be present in human saliva, but its distribution in different fractions of saliva is not known. LL-37 is formed from its intracellular pro-form, hCAP18, in an extracellular enzymatic reaction catalyzed by proteinase 3 and kallikrein 5. Here, we prepared cell-containing and cell-free fractions of unstimulated human whole saliva by centrifugation after depolymerization of mucins with dithiothreitol, and measured the levels of hCAP18/LL-37 in these fractions using ELISA. Cellular expression of hCAP18/LL-37 was determined by western blotting and immunocytochemistry. The ELISA analyses demonstrated that both cells and cell-free saliva contained hCAP18/LL-37. Western blot analysis of cell-pellet homogenates showed a strong band corresponding to hCAP18 at the correct molecular weight and a weak band corresponding to LL-37. Phase-contrast and light microscopy revealed that the cells consisted of desquamated epithelial cells. These cells expressed cytoplasmic immunoreactivity for hCAP18/LL-37. The peripheral part of the cytoplasm, corresponding to the plasma membrane, was particularly rich in hCAP18/LL-37 immunoreactivity. No immunoreactivity was observed after omission of the primary antibody. We conclude that desquamated epithelial cells of human whole saliva contain antimicrobial hCAP18/LL-37, suggesting that these cells may take part in the innate immune system by harboring and releasing these peptides.     

The influence of glucocorticoid receptor single nucleotide polymorphisms on outcome after haematopoietic stem cell transplantation

Haematopoietic stem cell transplantation (HSCT) remains the only cure for most haematological malignancies, however, the mortality rate remains high. Complications after HSCT include relapse, graft versus host disease (GvHD), graft rejection and infection. Over the last few years several groups, have demonstrated that non‐HLA gene polymorphisms can be predictive of outcome after HSCT. Since the glucocorticoid cortisol is pivotal in the regulation of the immune system, we decided to examine single nucleotide polymorphisms (SNPs; rs6198, rs33388 and rs33389) within the glucocorticoid receptor (GR) and correlate with HSCT outcome. The training set consisted of patients (n = 458) who underwent HSCT for acute leukaemia between 1983 and 2005. In the recipients, the absence of the ACT haplotype and absence of the T allele of rs33388 were associated with decreased OS and the absence of the ACT haplotype, the absence of the T allele of rs33388 and the presence of the ATA haplotype were associated with increased risk of relapse. In addition, the presence of the ACT haplotype in the recipient showed a trend to be associated with increased risk of chronic graft versus host disease (cGvHD). The patients in this cohort received mainly myeloablative conditioning (n = 327). The SNPs in the glucocorticoid receptor were then investigated in a validation set (n = 251) of HSCT patients transplanted for acute leukaemia from 2006. This cohort contained significantly more patients that had received reduced intensity conditioning (RIC). Some of the results could be validated in these patients. However, contrary to the training set, the absence of the haplotype ACT in the donor in this cohort was associated with increased risk of cGvHD. Differences in the conditioning were shown to influence the results. These results are the first to associate GR SNPs with HSCT outcome and demonstrate the inherent problems of replicating SNP association studies in HSCT, due to different pre‐transplant regimens.     

C3d binding to the circumsporozoite protein carboxy-terminus deviates immunity against malaria

The immunogenicity of recombinant protein or anti-viral DNA vaccines can be significantly improved by the addition of tandem copies of the complement fragment C3d. We sought to determine if the efficacy of a circumsporozoite protein (CSP)-based DNA vaccine delivered to mouse skin by gene gun was improved by using this strategy. Instead, we found that C3d suppressed the protective immunity against Plasmodium berghei malaria infection and deviated immunity, most notably by suppressing the induction of antibodies specific for the CSP C-terminal flanking sequence and by suppressing the induction of CSP-specific IL-4-producing spleen cells. We further showed that C3d bound to the C-terminal flanking sequence of the CSP, which may explain the immune deviation observed in CS/C3d chimeric antigen. We have thus identified C3d-mediated epitope masking and shifting of both the humoral and cellular immune responses as a potential novel escape mechanism, which plasmodia may use to divert the induction of protective immunity.