Broadly neutralizing humanized SARS-CoV-2 antibody binds to a conserved epitope on Spike and provides antiviral protection through inhalation-based delivery in non-human primates

The COVID-19 pandemic represents a global challenge that has impacted and is expected to continue to impact the lives and health of people across the world for the foreseeable future. The rollout of vaccines has provided highly anticipated relief, but effective therapeutics are required to further reduce the risk and severity of infections. Monoclonal antibodies have been shown to be effective as therapeutics for SARS-CoV-2, but as new variants of concern (VoC) continue to emerge, their utility and use have waned due to limited or no efficacy against these variants. Furthermore, cumbersome systemic administration limits easy and broad access to such drugs. As well, concentrations of systemically administered antibodies in the mucosal epithelium, a primary site of initial infection, are dependent on neonatal Fc receptor mediated transport and require high drug concentrations. To reduce the viral load more effectively in the lung, we developed an inhalable formulation of a SARS-CoV-2 neutralizing antibody binding to a conserved epitope on the Spike protein, ensuring pan-neutralizing properties. Administration of this antibody via a vibrating mesh nebulization device retained antibody integrity and resulted in effective distribution of the antibody in the upper and lower respiratory tract of non-human primates (NHP). In comparison with intravenous administration, significantly higher antibody concentrations can be obtained in the lung, resulting in highly effective reduction in viral load post SARS-CoV-2 challenge. This approach may reduce the barriers of access and uptake of antibody therapeutics in real-world clinical settings and provide a more effective blueprint for targeting existing and potentially emerging respiratory tract viruses.

Abstract 6036: Functional antibodies against multi span transmembrane proteins - revisiting the Warburg effect in cancer cells

Background: Alterations in tumor cell metabolism are one of the central processes guiding cancer progression. The increased glucose dependence of cancer cells, also known as the Warburg effect, opens the possibility to therapeutically target the glycolytic pathway and challenge the metabolic needs of tumor cells. We generated 24 monoclonal antibodies targeting the main glucose transporter on cancer cells - SLC2A1 (GLUT1). We evaluated the ability of the antibodies to affect cancer cell fitness alone and in combination with OXPHOS inhibitors to find clinically applicable therapeutics targeting tumor metabolism.

virus like particle (VLP)-based immunization strategy (Kivi, et al., BMC Biotechnology, 2016). Antibodies were functionally characterized by 2-deoxyglucose uptake interference assay and sensitivity to antibody single and combination treatments were evaluated in various tumor cell lines. Metabolomics and oxygen consumption rates were examined as mechanistic endpoints for tumor cell lines and primary tumor samples.

Results: The anti-SLC2A1 antibodies specifically bind to SLC2A1 with low nanomolar EC50 values and not to other glucose transporters. Antibody clones with functional properties inhibit glucose uptake leading to reduced metabolic activity and growth inhibition in a subset of cancer cell lines. A drastic cell proliferation inhibition is moreover observed in combination of anti-SLC2A1 antibodies and OXPHOS inhibitors metformin, phenformin or IACS-010759 in 2D cultures of colon, breast and pancreatic cancer cell lines. The inhibition of metabolic activity was further confirmed in an ex vivo primary patient tissue samples highlighting the putative translational applicability of our antibodies.

Conclusions: This is the first study to provide highly specific antibodies bocking the function of SLC2A1 transporter and demonstrate the proof of principle for inhibiting complex muti-pass membrane transporters with antibody therapeutics. While the developed anti-SLC2A1 antibodies could be efficacious in some indications as single agents, appreciable clinical activity could be obtained by the combined use with OXPHOS inhibitors.

Citation Format: Siret Tahk, Kai Virumäe, Paule Hermet, Korneelia Anton, Maiken Abel, Denis Belitškin, Luciano Galdieri, Steven Garner, Jillian Krings, Kaleb Collver, Emily Hoehn, Brendan Lahm, Kaitlyne Powers, Tuuli Käämbre, Alastair J. King, Francisca Neethling, Anu Planken, Mart Ustav, Andres Männik, Mart Ustav. Functional antibodies against multi span transmembrane proteins - revisiting the Warburg effect in cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6036.

Translational stalling at polyproline stretches is modulated by the sequence context upstream of the stall site

The polymerization of amino acids into proteins occurs on ribosomes, with the rate influenced by the amino acids being polymerized. The imino acid proline is a poor donor and acceptor for peptide-bond formation, such that translational stalling occurs when three or more consecutive prolines (PPP) are encountered by the ribosome. In bacteria, stalling at PPP motifs is rescued by the elongation factor P (EF-P). Using SILAC mass spectrometry of Escherichia coli strains, we identified a subset of PPP-containing proteins for which the expression patterns remained unchanged or even appeared up-regulated in the absence of EF-P. Subsequent analysis using in vitro and in vivo reporter assays revealed that stalling at PPP motifs is influenced by the sequence context upstream of the stall site. Specifically, the presence of amino acids such as Cys and Thr preceding the stall site suppressed stalling at PPP motifs, whereas amino acids like Arg and His promoted stalling. In addition to providing fundamental insight into the mechanism of peptide-bond formation, our findings suggest how the sequence context of polyproline-containing proteins can be modulated to maximize the efficiency and yield of protein production.

Lys34 of translation elongation factor EF-P is hydroxylated by YfcM

Lys34 of the conserved translation elongation factor P (EF-P) is post-translationally lysinylated by YjeK and YjeA--a modification that is critical for bacterial virulence. Here we show that the currently accepted Escherichia coli EF-P modification pathway is incomplete and lacks a final hydroxylation step mediated by YfcM, an enzyme distinct from deoxyhypusine hydroxylase that catalyzes the final maturation step of eukaryotic initiation factor 5A, the eukaryotic EF-P homolog.

Ribosome assembly in Escherichia coli strains lacking the RNA helicase DeaD/CsdA or DbpA

Ribosome subunit assembly in bacteria is a fast and efficient process. Among the nonribosomal proteins involved in ribosome biogenesis are RNA helicases. We describe ribosome biogenesis in Escherichia coli strains lacking RNA helicase DeaD (CsdA) or DbpA. Ribosome large subunit assembly intermediate particles (40S) accumulate at 25 degrees C and at 37 degrees C in the absence of DeaD but not without DbpA. 23S rRNA is incompletely processed in the 40S and 50S particles of the DeaD(-) strain. Pulse labeling showed that the 40S particles are converted nearly completely into functional ribosomes. The rate of large ribosomal subunit assembly was reduced about four times in DeaD-deficient cells. Functional activity tests of the ribosomal particles demonstrated that the final step of 50S assembly, the activation step, was affected when DeaD was not present. The results are compatible with the model that predicts multiple DeaD-catalyzed structural transitions of the ribosome large subunit assembly.