bims-polyam 2023-04-30 papers

bims-polyam

Biomed News

on Polyamines

Issue of 2023–04–30
thirteen papers selected by
Sebastian J. Hofer, University of Graz

Mechanisms of spermidine-induced autophagy and geroprotection.
Two New Cases of Bachmann-Bupp Syndrome Identified through the International Center for Polyamine Disorders.
Spermidine as a promising anticancer agent: Recent advances and newer insights on its molecular mechanisms.
Structural Analysis of Spermidine Synthase from Kluyveromyces lactis.
Influence of a phyA Mutation on Polyamine Metabolism in Arabidopsis Depends on Light Spectral Conditions.
Persistent Coxsackievirus B3 Infection in Pancreatic Ductal Cells In Vitro Downregulates Cellular Polyamine Metabolism.
Exploring polyamine interactions and binding pockets in SARS-CoV-2 ORF3a.
High-Dose Spermidine Supplementation Does Not Increase Spermidine Levels in Blood Plasma and Saliva of Healthy Adults: A Randomized Placebo-Controlled Pharmacokinetic and Metabolomic Study.
A Fine-Tuning of the Plant Hormones, Polyamines and Osmolytes by Ectomycorrhizal Fungi Enhances Drought Tolerance in Pedunculate Oak.
Drug repositioning to discover novel Ornithine Decarboxylase inhibitors against Visceral Leishmaniasis.
Spermidine protects intestinal mucosal barrier function in mice colitis via the AhR/Nrf2 and AhR/STAT3 signaling pathways.
Pd(II) and Pt(II) Trinuclear Chelates with Spermidine: Selective Anticancer Activity towards TNBC-Sensitive and -Resistant to Cisplatin.
SARS-CoV-2 RBD Conjugated to Polyglucin, Spermidine, and dsRNA Elicits a Strong Immune Response in Mice.

Nat Aging. 2022 Dec;2(12): 1112-1129

Mechanisms of spermidine-induced autophagy and geroprotection.

Sebastian J Hofer, Anna Katharina Simon, Martina Bergmann, Tobias Eisenberg, Guido Kroemer, Frank Madeo.

Aging involves the systemic deterioration of all known cell types in most eukaryotes. Several recently discovered compounds that extend the healthspan and lifespan of model organisms decelerate pathways that govern the aging process. Among these geroprotectors, spermidine, a natural polyamine ubiquitously found in organisms from all kingdoms, prolongs the lifespan of fungi, nematodes, insects and rodents. In mice, it also postpones the manifestation of various age-associated disorders such as cardiovascular disease and neurodegeneration. The specific features of spermidine, including its presence in common food items, make it an interesting candidate for translational aging research. Here, we review novel insights into the geroprotective mode of action of spermidine at the molecular level, as we discuss strategies for elucidating its clinical potential.

DOI: https://doi.org/10.1038/s43587-022-00322-9
Med Sci (Basel). 2023 04 04. pii: 29. [Epub ahead of print]11(2):

Two New Cases of Bachmann-Bupp Syndrome Identified through the International Center for Polyamine Disorders.

Julianne Michael, Elizabeth VanSickle, Marlie Vipond, Abby Dalman, Jeremy Prokop, Charles E Schwartz, Surender Rajasekaran, André S Bachmann, Magalie Barth, Clément Prouteau, Yotam Almagor, Lina Berkun, Gheona Alterescu, Caleb P Bupp.

  Recent identification of four additional polyaminopathies, including Bachmann-Bupp syndrome, have benefited from previous research on Snyder-Robinson syndrome in order to advance from research to treatment more quickly. As a result of the discovery of these conditions, the potential for treatment within this pathway, and for other possible unidentified polyaminopathies, the International Center for Polyamine Disorders (ICPD) was created to help promote understanding of these conditions, research opportunities, and appropriate care for families. This case study provides insights from two new patients diagnosed with Bachmann-Bupp syndrome, further expanding our understanding of this ultra-rare condition, as well as a general discussion about other known polyaminopathies. This work also presents considerations for collaborative research efforts across these conditions, along with others that are likely to be identified in time, and outlines the role that the ICPD hopes to fill as more patients with these polyaminopathies continue to be identified and diagnosed.

Keywords:  Bachmann–Bupp Syndrome (BABS); International Center for Polyamine Disorders (ICPD); Snyder–Robinson Syndrome (SRS); polyamine; α-difluoromethylornithine (DFMO)

DOI:  https://doi.org/10.3390/medsci11020029
Front Chem. 2023 ;11 1164477

Spermidine as a promising anticancer agent: Recent advances and newer insights on its molecular mechanisms.

Parteek Prasher, Mousmee Sharma, Sachin Kumar Singh, Monica Gulati, Dinesh Kumar Chellappan, Rashi Rajput, Gaurav Gupta, Alibek Ydyrys, Marzhan Kulbayeva, Ahmad Faizal Abdull Razis, Babagana Modu, Javad Sharifi-Rad, Kamal Dua.

  Spermidine is a naturally occurring polyamine compound found in semen. It is also found in several plant sources and boasts a remarkable biological profile, particularly with regards to its anticancer properties. Spermidine specifically interferes with the tumour cell cycle, resulting in the inhibition of tumor cell proliferation and suppression of tumor growth. Moreover, it also triggers autophagy by regulating key oncologic pathways. The increased intake of polyamines, such as spermidine, can suppress oncogenesis and slow the growth of tumors due to its role in anticancer immunosurveillance and regulation of polyamine metabolism. Spermidine/spermine N-1-acetyltransferase (SSAT) plays a critical role in polyamine homeostasis and serves as a diagnostic marker in human cancers. Chemically modified derivatives of spermidine hold great potential for prognostic, diagnostic, and therapeutic applications against various malignancies. This review discusses in detail the recent findings that support the anticancer mechanisms of spermidine and its molecular physiology.

Keywords:  anticancer immunosurveillance; anticancer properties; cell proliferation; diagnostic marker; polyamines; spermidine

DOI:  https://doi.org/10.3389/fchem.2023.1164477
Molecules. 2023 Apr 13. pii: 3446. [Epub ahead of print]28(8):

Structural Analysis of Spermidine Synthase from Kluyveromyces lactis.

Seongjin Kim, Jeong Ho Chang.

  Spermidine is a polyamine molecule that performs various cellular functions, such as DNA and RNA stabilization, autophagy modulation, and eIF5A formation, and is generated from putrescine by aminopropyltransferase spermidine synthase (SpdS). During synthesis, the aminopropyl moiety is donated from decarboxylated S-adenosylmethionine to form putrescine, with 5'-deoxy-5'-methylthioadenosine being produced as a byproduct. Although the molecular mechanism of SpdS function has been well-established, its structure-based evolutionary relationships remain to be fully understood. Moreover, only a few structural studies have been conducted on SpdS from fungal species. Here, we determined the crystal structure of an apo-form of SpdS from Kluyveromyces lactis (KlSpdS) at 1.9 Å resolution. Structural comparison with its homologs revealed a conformational change in the α6 helix linked to the gate-keeping loop, with approximately 40° outward rotation. This change caused the catalytic residue Asp170 to move outward, possibly due to the absence of a ligand in the active site. These findings improve our understanding of the structural diversity of SpdS and provide a missing link that expands our knowledge of the structural features of SpdS in fungal species.

Keywords:  SpdS; aminopropyltransferase; polyamine; putrescine; spermidine

DOI:  https://doi.org/10.3390/molecules28083446
Plants (Basel). 2023 Apr 18. pii: 1689. [Epub ahead of print]12(8):

Influence of a phyA Mutation on Polyamine Metabolism in Arabidopsis Depends on Light Spectral Conditions.

Altafur Rahman, Judit Tajti, Imre Majláth, Tibor Janda, Sylva Prerostova, Mohamed Ahres, Magda Pál.

  The aim of the study was to reveal the influence of phyA mutations on polyamine metabolism in Arabidopsis under different spectral compositions. Polyamine metabolism was also provoked with exogenous spermine. The polyamine metabolism-related gene expression of the wild type and phyA plants responded similarly under white and far-red light conditions but not at blue light. Blue light influences rather the synthesis side, while far red had more pronounced effects on the catabolism and back-conversion of the polyamines. The observed changes under elevated far-red light were less dependent on PhyA than the blue light responses. The polyamine contents were similar under all light conditions in the two genotypes without spermine application, suggesting that a stable polyamine pool is important for normal plant growth conditions even under different spectral conditions. However, after spermine treatment, the blue regime had more similar effects on synthesis/catabolism and back-conversion to the white light than the far-red light conditions. The additive effects of differences observed on the synthesis, back-conversion and catabolism side of metabolism may be responsible for the similar putrescine content pattern under all light conditions, even in the presence of an excess of spermine. Our results demonstrated that both light spectrum and phyA mutation influence polyamine metabolism.

Keywords:  blue light; far-red light; phytochrome; spermine

DOI:  https://doi.org/10.3390/plants12081689
mSphere. 2023 Apr 25. e0003623

Persistent Coxsackievirus B3 Infection in Pancreatic Ductal Cells In Vitro Downregulates Cellular Polyamine Metabolism.

Vincent Mastrodomenico, Natalie J LoMascolo, Mason R Firpo, Maria Del Mar Villanueva Guzman, Adam Zaporowski, Bryan C Mounce.

  Picornaviruses infect a wide variety of cell types in vitro, with rapid replication kinetics and pronounced cytopathic effect. Coxsackievirus B3 (CVB3) can also establish a persistent infection in vivo that can lead to pathology, including dilated cardiomyopathy and myocarditis. One model system to study persistent infection is the pancreatic ductal cell line PANC-1, which CVB3 infects and is maintained indefinitely. We have characterized this model for CVB3 infection to study persistent infection for over 6 months. We find that CVB3 rapidly replicates within PANC-1 cells without robust cytopathic effect, and after 1 month in culture, titers stabilize. We find that infection does not significantly affect cellular viability. Persistent virus reverts to lytic infection when transferred to Huh7 or Vero cells. We find that persistent CVB3 adapts to PANC-1 cells via mutation of its capsid proteins and, curiously, the viral polymerase (3Dpol) to generate a high-fidelity polymerase. Persistent infection is associated with reduced cleavage of eIF4G, reduced plaque size, and decreasing particle infectivity. We further find that polyamine metabolism is altered in persistently infected cells, with the rate-limiting enzyme ornithine decarboxylase (ODC1) reduced in translation. We further find that targeting polyamine synthesis reduces persistent infection without affecting the viability of the PANC-1 cells. Finally, we find that viral fidelity is essential to maintaining CVB3 infection, and targeting viral fidelity reduces persistent virus infection. Together, these data highlight a novel role for polyamines and fidelity in persistent CVB3 infection and suggest avenues for therapeutic development to target persistent infection. IMPORTANCE Enteroviruses are significant human pathogens that can cause severe disease, including cardiomyopathies. Viruses like coxsackievirus B3 (CVB3) can cause tissue damage by lytically infecting cells; however, CVB3 can also persistently infect, which has been associated with several pathologies. Studying persistent infection in vitro is challenging, as CVB3 lytically infects most cellular model systems. Here, we show that CVB3 establishes persistent infection in pancreatic ductal cells in vitro, similar to prior studies on other coxsackieviruses. We also show that this infection results in adaptation of the virus to these cells, as well as changes to cellular metabolism of polyamines.

Keywords:  coxsackievirus; enterovirus; pancreatic ductal cells; persistence; polyamines

DOI:  https://doi.org/10.1128/msphere.00036-23
J Mol Graph Model. 2023 Apr 10. pii: S1093-3263(23)00085-2. [Epub ahead of print]122 108487

Exploring polyamine interactions and binding pockets in SARS-CoV-2 ORF3a.

Panisak Boonamnaj, R B Pandey, Pornthep Sompornpisut.

  Ongoing global pandemic caused by coronavirus (COVID-19) requires urgent development of vaccines, treatments, and diagnostic tools. Open reading frame 3a (ORF3a) from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is considered to be a potential drug target for COVID-19 treatment. ORF3a is an accessory protein that plays a significant role in virus-host interactions and in facilitating host immune responses. Using putrescine, spermidine and spermine, an aliphatic polyamine for the activity suppression of ORF3a appears to be a promising approach in finding new targets for drug design. In this study, we explored the possible binding poses of polyamines to the ORF3a protein using a combination of various computational approaches i.e. pocket prediction, blind and site-specific molecular docking, molecular dynamics and ligand flooding simulations. The results showed that the tip of cytoplasmic domain and the upper tunnel of transmembrane domain of ORF3a provide a suitable binding site specific for the polyamines. MD simulations revealed the stability of spermidine binding in the upper tunnel pocket of ORF3a through salt bridge and hydrogen bond interactions between the amine groups of the ligand and negatively charged residues of ORF3a. These findings can be helpful in designing new therapeutic drugs.

Keywords:  Molecular docking; Molecular dynamics; ORF3a; SAR-CoV-2; Spermidine

DOI:  https://doi.org/10.1016/j.jmgm.2023.108487
Nutrients. 2023 Apr 12. pii: 1852. [Epub ahead of print]15(8):

High-Dose Spermidine Supplementation Does Not Increase Spermidine Levels in Blood Plasma and Saliva of Healthy Adults: A Randomized Placebo-Controlled Pharmacokinetic and Metabolomic Study.

Stefan Senekowitsch, Eliza Wietkamp, Michael Grimm, Franziska Schmelter, Philipp Schick, Anna Kordowski, Christian Sina, Hans Otzen, Werner Weitschies, Martin Smollich.

  (1) Background: Spermidine is a biogenic polyamine that plays a crucial role in mammalian metabolism. As spermidine levels decline with age, spermidine supplementation is suggested to prevent or delay age-related diseases. However, valid pharmacokinetic data regarding spermidine remains lacking. Therefore, for the first time, the present study investigated the pharmacokinetics of oral spermidine supplementation. (2) Methods: This study was designed as a randomized, placebo-controlled, triple-blinded, two-armed crossover trial with two 5-day intervention phases separated by a washout phase of 9 days. In 12 healthy volunteers, 15 mg/d of spermidine was administered orally, and blood and saliva samples were taken. Spermidine, spermine, and putrescine were quantified by liquid chromatography-mass spectrometry (LC-MS/MS). The plasma metabolome was investigated using nuclear magnetic resonance (NMR) metabolomics. (3) Results: Compared with a placebo, spermidine supplementation significantly increased spermine levels in the plasma, but it did not affect spermidine or putrescine levels. No effect on salivary polyamine concentrations was observed. (4) Conclusions: This study's results suggest that dietary spermidine is presystemically converted into spermine, which then enters systemic circulation. Presumably, the in vitro and clinical effects of spermidine are at least in part attributable to its metabolite, spermine. It is rather unlikely that spermidine supplements with doses <15 mg/d exert any short-term effects.

Keywords:  COVID-19; SARS-CoV-2; autophagy; putrescine; spermidine; spermine

DOI:  https://doi.org/10.3390/nu15081852
Int J Mol Sci. 2023 Apr 19. pii: 7510. [Epub ahead of print]24(8):

A Fine-Tuning of the Plant Hormones, Polyamines and Osmolytes by Ectomycorrhizal Fungi Enhances Drought Tolerance in Pedunculate Oak.

Marko Kebert, Saša Kostić, Srđan Stojnić, Eleonora Čapelja, Anđelina Gavranović Markić, Martina Zorić, Lazar Kesić, Victor Flors.

  The drought sensitivity of the pedunculate oak (Quercus robur L.) poses a threat to its survival in light of climate change. Mycorrhizal fungi, which orchestrate biogeochemical cycles and particularly have an impact on the plant's defense mechanisms and metabolism of carbon, nitrogen, and phosphorus, are among the microbes that play a significant role in the mitigation of the effects of climate change on trees. The study's main objectives were to determine whether ectomycorrhizal (ECM) fungi alleviate the effects of drought stress in pedunculate oak and to investigate their priming properties. The effects of two levels of drought (mild and severe, corresponding to 60% and 30% of field capacity, respectively) on the biochemical response of pedunculate oak were examined in the presence and absence of ectomycorrhizal fungi. To examine whether the ectomycorrhizal fungi modulate the drought tolerance of pedunculate oak, levels of plant hormones and polyamines were quantified using UPLC-TQS and HPLC-FD techniques in addition to gas exchange measurements and the main osmolyte amounts (glycine betaine-GB and proline-PRO) which were determined spectrophotometrically. Droughts increased the accumulation of osmolytes, such as proline and glycine betaine, as well as higher polyamines (spermidine and spermine) levels and decreased putrescine levels in both, mycorrhized and non-mycorrhized oak seedlings. In addition to amplifying the response of oak to severe drought in terms of inducible proline and abscisic acid (ABA) levels, inoculation with ECM fungi significantly increased the constitutive levels of glycine betaine, spermine, and spermidine regardless of drought stress. This study found that compared to non-mycorrhized oak seedlings, unstressed ECM-inoculated oak seedlings had higher levels of salicylic (SA) and abscisic acid (ABA) but not jasmonic acid (JA), indicating a priming mechanism of ECM is conveyed via these plant hormones. According to a PCA analysis, the effect of drought was linked to the variability of parameters along the PC1 axe, such as osmolytes PRO, GB, polyamines, and plant hormones such as JA, JA-Ile, SAG, and SGE, whereas mycorrhization was more closely associated with the parameters gathered around the PC2 axe (SA, ODPA, ABA, and E). These findings highlight the beneficial function of the ectomycorrhizal fungi, in particular Scleroderma citrinum, in reducing the effects of drought stress in pedunculate oak.

Keywords:  drought; ectomycorrhizal fungi; osmolytes; pedunculate oak; plant hormones; polyamines

DOI:  https://doi.org/10.3390/ijms24087510
J Mol Recognit. 2023 Apr 24. e3021

Drug repositioning to discover novel Ornithine Decarboxylase inhibitors against Visceral Leishmaniasis.

Sabahat Yasmeen Sheikh, Waseem Ahmad Ansari, Firoj Hassan, Tabrez Faruqui, Mohammad Faheem Khan, Yusuf Akhter, Abdul Rahman Khan, Maqsood A Siddiqui, Abdulaziz A Al-Khedhairy, Malik Nasibullah.

  Visceral leishmaniasis (VL) is caused by Leishmania donovani (Ld), and most cases occur in Brazil, East Africa, and India. The treatment for VL is limited and has many adverse effects. The development of safer and more efficacious drugs is urgently needed. Drug repurposing is one of the best processes to repurpose existing drugs. Ornithine decarboxylase (ODC) is an important target against L. donovani in the polyamine biosynthesis pathway. In this study, we have modeled the 3D structure of ODC and performed high-throughput virtual screening (HTVS) of 8630 ZINC database ligands against Leishmania donovani ornithine decarboxylase (Ld ODC), selecting 45 ligands based on their high binding score. It is further validated through molecular docking simulation and the selection of the top two lead molecules (ceftaroline fosamil and rimegepant) for Molecular Dynamics (MD) simulation, DFT, and MMGBSA analysis. The results showed that the binding affinities of ceftaroline fosamil, and rimegepant are, respectively, -10.719 and 10.159 kcal/mol. The docking complexes of the two lead compounds, ceftaroline fosamil, and rimegepant, with the target ODC, were found stable during molecular dynamics simulations. Furthermore, the analysis of molecular mechanics generalized Born surface area (MMGBSA) revealed that these compounds had a high binding free energy. The DFT analysis showed that the top lead molecules were more reactive than the standard drug (pentamidine). In-silico findings demonstrated that ceftaroline fosamil, and rimegepant might be recognized as potent antagonists against ODC for the treatment of VL. This article is protected by copyright. All rights reserved.

Keywords:  Visceral Leishmaniasis; molecular docking; molecular dynamics; ornithine decarboxylase, DFT, and MMGBSA

DOI:  https://doi.org/10.1002/jmr.3021
Int Immunopharmacol. 2023 Apr 25. pii: S1567-5769(23)00487-3. [Epub ahead of print]119 110166

Spermidine protects intestinal mucosal barrier function in mice colitis via the AhR/Nrf2 and AhR/STAT3 signaling pathways.

Bing Yan, Xinjie Mao, Shasha Hu, Shimin Wang, Xiaochen Liu, Jing Sun.

   BACKGROUND: Aryl hydrocarbon receptor (AhR) activation promotes intestinal barrier repair and enhances the gut mucosal barrier function in inflammatory bowel diseases (IBD). Spermidine is beneficial in several murine models of IBD and may affect AhR activity. However, the precise effects of spermidine on the intestinal barrier and AhR remain unclear. This study was designed to investigate whether spermidine affects AhR and gut barrier function in IBD models as well as, its underlying mechanism.
METHODS: We used dextran sulfate sodium (DSS)- and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced mice, as well as, Caco2 cells incubated with TNF-α and IFN-γ to establish multiple IBD models, followed by spermidine intervention. Alcian blue/Periodic acid-Schiff (AB/PAS) staining, Fluorescein isothiocyanate (FITC)-dextran permeability assay, transepithelial electrical resistance (TER), tight junction protein (TJs) expression, and 16S rRNA scope in situ hybridization were performed to assess intestinal barrier function. AhR expression and the associated pathways were measured. AhR-targeted adeno-associated virus (AAV) and siRNA were used to explore the related molecular mechanisms.
RESULTS: Spermidine significantly attenuated the increased intestinal permeability, decreased TER, abnormal distribution of TJs in colitis, and bacterial translocation from the gut tract. Additionally, it significantly increased AhR and Nrf2 expression and inhibited STAT3 phosphorylation. However, the protective effects of spermidine and the related alterations in pathway proteins were largely abolished by the specific inhibition of AhR.
CONCLUSION: Our study demonstrated that spermidine rescues intestinal barrier defects in mice with colitis via the AhR-Nrf2 and AhR-STAT3 pathways, providing a potential therapeutic agent for IBD and other conditions associated with dysregulated gut barrier function.

Keywords:  AhR; IBD; Intestinal mucosal barrier; Nrf2; STAT3; Spermidine

DOI:  https://doi.org/10.1016/j.intimp.2023.110166
Pharmaceutics. 2023 Apr 10. pii: 1205. [Epub ahead of print]15(4):

Pd(II) and Pt(II) Trinuclear Chelates with Spermidine: Selective Anticancer Activity towards TNBC-Sensitive and -Resistant to Cisplatin.

Martin Vojtek, Clara B Martins, Raquel Ramos, Sara Gomes Duarte, Isabel M P L V O Ferreira, Ana L M Batista de Carvalho, M Paula M Marques, Carmen Diniz.

  Triple-negative breast cancer (TNBC) is one of the most aggressive forms of breast cancer and constitutes 10-20% of all breast cancer cases. Even though platinum-based drugs such as cisplatin and carboplatin are effective in TNBC patients, their toxicity and development of cancer drug resistance often hamper their clinical use. Hence, novel drug entities with improved tolerability and selectivity profiles, as well as the ability to surpass resistance, are needed. The current study focuses on Pd(II) and Pt(II) trinuclear chelates with spermidine (Pd3Spd2 and Pt3Spd2) for evaluating their antineoplastic activity having been assessed towards (i) cisplatin-resistant TNBC cells (MDA-MB-231/R), (ii) cisplatin-sensitive TNBC cells (MDA-MB-231) and (iii) non-cancerous human breast cells (MCF-12A, to assess the cancer selectivity/selectivity index). Additionally, the complexes' ability to overcome acquired resistance (resistance index) was determined. This study revealed that Pd3Spd2 activity greatly exceeds that displayed by its Pt analog. In addition, Pd3Spd2 evidenced a similar antiproliferative activity in both sensitive and resistant TNBC cells (IC50 values 4.65-8.99 µM and 9.24-13.34 µM, respectively), with a resistance index lower than 2.3. Moreover, this Pd compound showed a promising selectivity index ratio: >6.28 for MDA-MB-231 cells and >4.59 for MDA-MB-231/R cells. Altogether, the data presently gathered reveal Pd3Spd2 as a new, promising metal-based anticancer agent, which should be further explored for the treatment of TNBC and its cisplatin-resistant forms.

Keywords:  antineoplastic activity; antiproliferative; cancer resistance; cell viability; cisplatin; palladium; platinum; therapy

DOI:  https://doi.org/10.3390/pharmaceutics15041205
Vaccines (Basel). 2023 Apr 06. pii: 808. [Epub ahead of print]11(4):

SARS-CoV-2 RBD Conjugated to Polyglucin, Spermidine, and dsRNA Elicits a Strong Immune Response in Mice.

Ekaterina A Volosnikova, Iuliia A Merkuleva, Tatiana I Esina, Dmitry N Shcherbakov, Mariya B Borgoyakova, Anastasiya A Isaeva, Valentina S Nesmeyanova, Natalia V Volkova, Svetlana V Belenkaya, Anna V Zaykovskaya, Oleg V Pyankov, Ekaterina V Starostina, Alexey M Zadorozhny, Boris N Zaitsev, Larisa I Karpenko, Alexander A Ilyichev, Elena D Danilenko.

  Despite the rapid development and approval of several COVID vaccines based on the full-length spike protein, there is a need for safe, potent, and high-volume vaccines. Considering the predominance of the production of neutralizing antibodies targeting the receptor-binding domain (RBD) of S-protein after natural infection or vaccination, it makes sense to choose RBD as a vaccine immunogen. However, due to its small size, RBD exhibits relatively poor immunogenicity. Searching for novel adjuvants for RBD-based vaccine formulations is considered a good strategy for enhancing its immunogenicity. Herein, we assess the immunogenicity of severe acute respiratory syndrome coronavirus 2 RBD conjugated to a polyglucin:spermidine complex (PGS) and dsRNA (RBD-PGS + dsRNA) in a mouse model. BALB/c mice were immunized intramuscularly twice, with a 2-week interval, with 50 µg of RBD, RBD with Al(OH)3, or conjugated RBD. A comparative analysis of serum RBD-specific IgG and neutralizing antibody titers showed that PGS, PGS + dsRNA, and Al(OH)3 enhanced the specific humoral response in animals. There was no significant difference between the groups immunized with RBD-PGS + dsRNA and RBD with Al(OH)3. Additionally, the study of the T-cell response in animals showed that, unlike adjuvants, the RBD-PGS + dsRNA conjugate stimulates the production of specific CD4+ and CD8+ T cells in animals.

Keywords:  COVID-19; RBD; SARS-CoV-2; adjuvant; receptor-binding domain

DOI:  https://doi.org/10.3390/vaccines11040808