RESUMO
SARS-CoV-2 neutralizing antibodies play a critical role in prevention and treatment of COVID-19 but are challenged by viral evolution and antibody evasion, exemplified by the highly resistant Omicron BA.1 sublineage.1-12 Importantly, the recently identified Omicron sublineages BA.2.12.1 and BA.4/5 with differing spike mutations are rapidly emerging in various countries. By determining polyclonal serum activity of 50 convalescent or vaccinated individuals against BA.1, BA.1.1, BA.2, BA.2.12.1, and BA.4/5, we reveal a further reduction of BA.4/5 susceptibility to vaccinee sera. Most notably, delineation of the sensitivity to an extended panel of 163 antibodies demonstrates pronounced antigenic differences of individual sublineages with distinct escape patterns and increased antibody resistance of BA.4/5 compared to the most prevalent BA.2 sublineage. These results suggest that the antigenic distance from BA.1 and the increased resistance compared to BA.2 may favor immune escape-mediated expansion of BA.4/5 after the first Omicron wave. Finally, while most monoclonal antibodies in clinical stages are inactive against all Omicron sublineages, we identify promising novel antibodies with high pan-Omicron neutralizing potency. Our study provides a detailed understanding of the antibody escape from the most recently emerging Omicron sublineages that can inform on effective strategies to prevent and treat COVID-19.
RESUMO
Pre-existing immunity against SARS-CoV-2 may have critical implications for our understanding of COVID-19 susceptibility and severity. Various studies recently provided evidence of pre-existing T cell immunity against SARS-CoV-2 in unexposed individuals. In contrast, the presence and clinical relevance of a pre-existing B cell immunity remains to be fully elucidated. Here, we provide a detailed analysis of the B cell response to SARS-CoV-2 in unexposed individuals. To this end, we extensively investigated the memory B cell response to SARS-CoV-2 in 150 adults sampled pre-pandemically. Comprehensive screening of donor plasma and purified IgG samples for binding and neutralization in various functional assays revealed no substantial activity against SARS-CoV-2 but broad reactivity to endemic betacoronaviruses. Moreover, we analyzed antibody sequences of 8,174 putatively SARS-CoV-2-reactive B cells on a single cell level and generated and tested 158 monoclonal antibodies. None of the isolated antibodies displayed relevant binding or neutralizing activity against SARS-CoV-2. Taken together, our results show no evidence of relevant pre-existing antibody and B cell immunity against SARS-CoV-2 in unexposed adults.
RESUMO
The identification and isolation of highly infectious SARS-CoV-2-infected individuals is an important public health strategy. Rapid antigen detection tests (RADT) are promising candidates for large-scale screenings due to timely results and feasibility for on-site testing. Nonetheless, the diagnostic performance of RADT in detecting infectious individuals is yet to be fully determined. Two combined oro- and nasopharyngeal swabs were collected from individuals at a routine SARS-CoV-2 diagnostic center. Side-by-side evaluations of RT-qPCR and RADT as well as live virus cultures of positive samples were performed to determine the sensitivity of the Standard Q COVID-19 Ag Test (SD Biosensor/Roche) in detecting SARS-CoV-2-infected individuals with cultivable virus. A total of 2,028 samples were tested and 118 virus cultures inoculated. SARS-CoV-2 infection was detected in 210 samples by RT-qPCR, representing a positive rate of 10.36%. The Standard Q COVID-19 Ag Test yielded a positive result in 92 (4.54%) samples resulting in an overall sensitivity and specificity of 42.86% and 99.89%. For adjusted Ct values <20, <25, and <30 the RADT reached sensitivities of 100%, 98.15%, and 88.64%, respectively. All 29 culture positive samples were detected by RADT. While overall sensitivity was low, Standard Q COVID-19 RADT reliably detected patients with high RNA loads. Additionally, negative RADT results fully corresponded with the lack of viral cultivability in Vero E6 cells. These results indicate that RADT can be a valuable tool for the detection of individuals that are likely to transmit SARS-CoV-2. RADT testing could therefore guide public health testing strategies to combat the COVID-19 pandemic. One Sentence SummaryStandard Q COVID-19 Ag test reliably detects individuals with high RNA loads and negative results correspond with lack of viral cultivability of SARS-CoV-2 in Vero E6 cells.
RESUMO
The SARS-CoV-2 pandemic has unprecedented implications for public health, social life, and world economy. Since approved drugs and vaccines are not available, new options for COVID-19 treatment and prevention are highly demanded. To identify SARS-CoV-2 neutralizing antibodies, we analysed the antibody response of 12 COVID-19 patients from 8 to 69 days post diagnosis. By screening 4,313 SARS-CoV-2-reactive B cells, we isolated 255 antibodies from different time points as early as 8 days post diagnosis. Among these, 28 potently neutralized authentic SARS-CoV-2 (IC100 as low as 0.04 g/ml), showing a broad spectrum of V genes and low levels of somatic mutations. Interestingly, potential precursors were identified in naive B cell repertoires from 48 healthy individuals that were sampled before the COVID-19 pandemic. Our results demonstrate that SARS-CoV-2 neutralizing antibodies are readily generated from a diverse pool of precursors, fostering the hope of rapid induction of a protective immune response upon vaccination.
RESUMO
The management of gastric gastrointestinal stromal tumors (GIST) is complex. Local tumor resection with disease-free resection margins without lymphadenectomy is the treatment of choice for primary non-metastatic tumors. This can be achieved with several techniques including wedge resection, transgastric resection, partial gastrectomy, total gastrectomy, and multivisceral resection. Open and minimally invasive surgical approaches can be considered. We describe the technical steps of the aforementioned procedures in relation to tumor size, tumor location (especially at or near the gastro-esophageal junction or pylorus), pattern of exophytic or intraluminal growth, adherence to surrounding structures, and other tumor-associated factors. Challenging situations in gastric surgery for GISTs are also discussed and categorized according to a classification of intraoperative complexity (1 [easy] to 4 [very difficult]). On the basis of this classification, we divided all patients with an indication for gastric GIST surgery into appropriate groups.
