Biology subjects

Steinmetz, T.

Publications and source records attributed to Steinmetz, T..

3 recordsLinked to original sources

bioRxiv2021

A pair of non-competing neutralizing human monoclonal antibodies protecting from disease in a SARS-CoV-2 infection model

TRIANNI mice carry an entire set of human immunoglobulin V region gene segments and are a powerful tool to rapidly generate human monoclonal antibodies. After immunizing these mice against the spike protein of SARS-CoV-2, we identified 29 hybridoma antibodies that reacted with the SARS-CoV-2 spike protein. Nine antibodies neutralized SARS-CoV-2 infection at IC50 values in the subnanomolar range. ELISA-binding studies and DNA sequence analyses revealed one cluster of clonally related neutralizing antibodies that target the receptor-binding domain and compete with the cellular receptor hACE2. A second cluster of neutralizing antibodies binds to the N-terminal domain of the spike protein without competing with the binding of hACE2 or cluster 1 antibodies. SARS-CoV-2 mutants selected for resistance to an antibody from one cluster are still neutralized by an antibody from the other cluster. Antibodies from both clusters markedly reduced viral spread in mice transgenic for human ACE2 and protected the animals from SARS-CoV-2 induced weight loss. Thus, we report two clusters of potent non-competing SARS-CoV-2 neutralizing antibodies providing potential candidates for therapy and prophylaxis of COVID-19. The study further supports the use of transgenic animals with human immunoglobulin gene repertoires in pandemic preparedness initiatives.

immunology↗

bioRxiv2021

Mitochondrial function is essential for humoral immunity by controlling flux of the TCA cycle, phosphatidic acid and mTOR activity in B cells

The function of mitochondrial respiration during B cell fate decisions and differentiation remains equivocal. This study reveals that selection for mitochondrial fitness occurs during B cell activation and is essential for subsequent plasma cell differentiation. By expressing a mutated mitochondrial helicase in transitional B cells, we depleted mitochondrial DNA during B cell maturation, resulting in reduced oxidative phosphorylation. Although no changes in follicular B cell development were evident, germinal centers, class switch recombination to IgG, plasma cell generation and humoral immunity were diminished. Defective oxidative phosphorylation led to aberrant flux of the tricarboxylic acid cycle and lowered the amount of saturated phosphatidic acid. Consequently, MTOR activity and BLIMP-1 induction were curtailed whereas HIF1, glycolysis and AMPK activity were amplified. Exogenous phosphatidic acid increased mTOR activity in activated B cells. Hence, mitochondrial function is required and selected for in activated B cells for the successful generation of functional plasma cells.

immunology↗

bioRxiv2019

The Trk fused gene-product (Tfg) is part of a 600-700kDa CARMA1 complex

B cell receptor (BCR) mediated activation of nuclear factor {kappa}B (NF-{kappa}B) is key to humoral immunity. CARMA1 (CARD11) is essential for BCR mediated NF-{kappa}B activation by interacting with Bcl10 and MALT1. Besides these two main players, few interaction partners of the CARMA1 complex are known. Here we identified new interaction partners of CARMA1. We generated two rabbit antisera against mouse CARMA1 to immunopurify endogenous CARMA1 from lysates of mouse B cells. Nik-binding protein (NIBP), Ras-GAP SH3 binding protein 2 (G3BP1) and Trk-fused gene (Tfg) were identified by peptide mass fingerprinting in immunopurified CARMA1 complexes. The interaction of Tfg and CARMA1 was confirmed by co-immunoprecipitation and Blue native polyacrylamide gel electrophoresis using the anti CARMA1 and newly generated anti Tfg antibodies. This analysis revealed that CARMA1 formed complexes of 600-1000 kDa. Additionally, Tfg was found in complexes of 500-600 kDa which increased in size to [~]740 kDa upon overexpresssion.

biochemistry↗