Analysis of antibodies from whole-cell immunization by a tANCHOR cell-based ELISA

Monitoring specific antibodies derived from whole-cell immunization through cell-based ELISA methods poses challenges due to humoral responses against various cell proteins. In this report, we outline a technique involving pre-adsorption on cells to remove undesirable antibodies from immune serum. This step provides the subsequent monitoring of antibodies specific to the targeted antigen using a tANCHOR-based ELISA. Notably, this approach accelerates result acquisition, eliminating the necessity to purify the expressed antigen or obtain a customized peptide for coating assay plates.

tANCHOR-cell-based assay for monitoring of SARS-CoV-2 neutralizing antibodies rapidly adaptive to various receptor-binding domains

Conventional neutralizing enzyme-linked immunosorbent assay (ELISA) systems for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mimic the protein-protein interaction between angiotensin-converting enzyme 2 (ACE2) and the receptor-binding domain (RBD). However, an easy and rapidly adaptative ELISA-based system for testing neutralizing antibodies against upcoming SARS-CoV-2 variants is urgently needed. In this study, we closed this gap by developing a tANCHOR-cell-based RBD neutralization assay that avoids time-consuming protein expression and purification followed by coating on ELISA plates. This cell-based assay can be rapidly adopted to monitor neutralizing antibodies (NAbs) against upcoming SARS-CoV-2 variants. We show that the results obtained with the tANCHOR-cell-based assay system strongly correlate with commercially available surrogate assays for testing NAbs. Moreover, this technique can directly measure binding between cell-surface-exposed RBDs and soluble ACE2. With this technique, the degree of antibody escape elicited by emerging SARS-CoV-2 variants in current vaccination regimens can be determined rapidly and reliably.

tANCHOR cell-based ELISA approach as a surrogate for antigen-coated plates to monitor specific IgG directed to the SARS-CoV-2 receptor-binding domain

Enzyme-linked immunosorbent assay (ELISA) systems use plates coated with peptides or expressed and purified proteins to monitor immunoglobulins derived from patient serum. However, there is currently no easy, flexible, and fast adaptive ELISA-based system for testing antibodies directed against new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. In this study, we utilized the tANCHOR protein display system that provides a cell surface decorated with the receptor-binding domain (RBD) to monitor specific antibodies derived from SARS-CoV-2 convalescent and vaccinated individuals directed against it. To test sera from vaccinees or convalescent individuals, only the RBD coding sequence needs to be cloned in the tANCHOR vector system and transfected into HeLa cells. Time-consuming protein expression, isolation, and purification followed by coating assay plates are not necessary. With this technique, the immune evasion of new SARS-CoV-2 variants from current vaccination regimes can be examined quickly and reliably.

Label-Free Imaging of Solid-Phase Peptide Synthesis Products and Their Modifications Tethered in Microspots Using Time-of-Flight Secondary Ion Mass Spectrometry

Time-of-flight secondary ion mass spectrometry is used to analyze solid-phase synthesis products in 60 µm spots of high-density peptide arrays. As a result, a table of specific fragments for the individual detection of amino acids and their side chain protecting groups within peptides is compiled. The specific signal of an amino acid increases linearly as its number increases in the immobilized peptide. Mass-to-charge ratio values are identified that can distinguish between isomers such as leucine and isoleucine. The accessibility of the N-terminus of polyalanine will be studied depending on the number of its residues. The examples provided in the study demonstrate the significant potential of time-of-flight secondary ion mass spectrometry for high-throughput screening of functional groups and their accessibility to chemical reactions occurring simultaneously in hundreds of thousands of microreactors on a single microscope slide.

[Tumor biologic prognostic parameters in T1N0M0 squamous cell carcinoma of the oral cavity]

BACKGROUND

Conventional prognostic factors in squamous cell carcinomas are tumor stage, tumor size, evidence of lymph node metastases, extracapsular spread of lymph node metastases, and Broder's grading. Unfortunately these parameters are only of limited value in predicting the biological behavior and ultimately the prognosis of a particular tumor. The present study was conducted for determining objective prognostic factors based on tumor biologic examinations in patients with squamous cell carcinomas of the oral cavity. These parameters were compared to the conventional prognostic factors.

PATIENTS AND METHODS

Operative specimens of fourty-two patients who underwent surgery for a squamous cell carcinoma of the oral cavity with clinical TNM stage T1N0M0 were examined. All tumors were radically excised with histologic clear margins, which were confirmed by serial sections. The examinations included morphologic multifactorial tumor front grading, quantitative DNA analysis, and immunohistochemical assessment of proliferation markers (i.e. proliferating cell nuclear antigen [PCNA] and MIB1) and of oncogene products (i.e. p53; nm23). Prognostic significance of particular parameters was evaluated by univariate and multivariate Cox regression models.

RESULTS

In clinical follow-up of 70 months on average, 6 patients developed local recurrences and 5 patients lymph node metastases. Three patients died of disease. Tumors which recurred had increased values for 2 c Deviation Index, 5 c Exceeding Rate along with high tumor front grading scores and proliferation scores. Using multivariate Cox regression analysis, parameters which were highly significant for prognosis were 5 c Exceeding Rate, tumor front grading score and PCNA score. None of the clinical parameters achieved statistical significance in the multivariate model. Tumors which recurred had also increased expression rates for p53 and nm23. Nevertheless this was statistically not significant.

CONCLUSIONS

Tumor biologic examinations provide important informations about the clinical aggressiveness and ultimately about the prognosis of a particular tumor. Tumors with aggressive behavior can already be identified during initial diagnosis, which has consequences for the therapeutic management of the patients.

Interaction of the regulatory protein NicR1 with the promoter region of the pAO1-encoded 6-hydroxy-D-nicotine oxidase gene of Arthrobacter oxidans

The D,L-nicotine catabolism of the Gram-positive soil bacterium Arthrobacter oxidans is linked to the presence within the cells of the 160 kb catabolic plasmid pAO1. pAO1-cured cells lost the catabolic enzymes and reintroduction of pAO1 by electroporation into cured cells reestablished the nic+ phenotype. DNA band shift assays with extracts from cured and pAO1+ cells suggested that pAO1 encodes the regulatory protein NicR1. Footprint analysis revealed that two homologous palindromes (IR1 and IR2), present in the 5'-regulatory region of the 6-HDNO gene, were protected from DNase I digestion. Binding of NicR1 to the palindromes is symmetrical, co-operative, and stronger to IR1 containing the 6-HDNO gene promoter than to IR2. Site-directed mutagenesis revealed that steric constraints and sequence requirements for NicR1-binding are located exclusively in the palindromic sequences. Deletions and insertions in the interpalindromic region and in the 6-HDNO promoter -10 sequence had no effect on the binding characteristics of NicR1 to the 6-HDNO regulatory region. Acting as a repressor, NicR1 prevents binding of the E. coli RNA-polymerase to the consensus sigma 70 promoter in vitro. However, the interaction of NicR1 with the 6-HDNO promoter region in extracts of nicotine-induced cells from various growth stages did not differ from that observed with extracts of nicotine-uninduced cells.