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Cationic Nanoemulsion-Encapsulated Retinoic Acid as an Adjuvant to Promote OVA&#45;Specific Systemic and Mucosal Responses

Cationic nanostructures have emerged as an adjuvant and antigen delivery system that enhances dendritic cell maturation, ROS generation, and antigen ...

Third Military Medical University

As TLR2 agonists, several lipopeptides had been proved to be candidate vaccine adjuvants. In our previous study, lipopeptides mimicking N-terminal structures of the bacterial lipoproteins were also able to promote antigen-specific immune response. However, the structure-activity relationship of lipopeptides as TLR2 agonists is still unclear. Here, 23 synthetic lipopeptides with the same lipid moiety but different peptide sequences were synthesized, and their TLR2 activities  and mucosal adjuvant effects to OVA were evaluated. LP1-14, LP1-30, LP1-34 and LP2-2 exhibited significantly lower cytotoxicity and stronger TLR2 activity compared with PamCSK, the latter being one of the most potent TLR2 agonists. LP1-34 and LP2-2 assisted OVA to induce more profound specific IgG in sera or sIgA in BALF than PamCSK. Furthermore, the possibility of LP1-34, LP2-2 and PamCSK as the mucosal adjuvant for the SARS-CoV-2 recombinant RBD (rRBD) was investigated. Intranasally immunized with rRBD plus either the novel lipopeptide or PamCSK significantly increased the levels of specific serum and respiratory mucosal IgG and IgA, while rRBD alone failed to induce specific immune response due to its low immunogenicity. The novel lipopeptides, especially LP2-2, significantly increased levels of rRBD-induced SARS-CoV-2 neutralizing antibody in sera, BALF and nasal wash. Finally, Support vector machine (SVM) results suggested that charged residues in lipopeptides might be beneficial to the agonist activity, while lipophilic residues might adversely affect the agonistic activity. Figuring out the relationship between peptide sequence in the lipopeptide and its TLR2 activity may lay the foundation for the rational design of novel lipopeptide adjuvant for COVID-19 vaccine.

Novel Synthetic Lipopeptides as Potential Mucosal Adjuvants Enhanced SARS-CoV-2 rRBD-Induced Immune Response.

With the help of the establishment of novel reaction methodology, a series of N-Aryl-5-(2,2,2-trifluoroethoxy)-1,5-dihydro-2H-pyrrol-2-one conjugates were designed and synthesized in 2-4 steps, and subsequent anticancer activity of these compounds was evaluated. Preliminary results showed that these compounds have moderate to potent activities against human acute leukemia cells K562, human lung cancer A549, human breast cancer MDA-MB-231, and human cervical cancer HeLa cancer cell lines. Among them, compounds 2d and 2k were the most potent against K562 cell line with IC values of 0.07 and 0.52 µM, respectively, and the toxicity of 2d to the normal of hepatocytes (LO2) cell line was low (the survival rate 81 %). Flow cytometry analysis showed that 2d arrested K562 cells in the G2/M phase potently, even much better than Combretastatin A4 (CA4). In addition, the results demonstrated the involvement of the caspase-dependent or independent pathways of apoptosis, evidenced by the upregulation of FADD, pro-caspase 3, cleaved-caspase 3, HTRA2/Omi, SMAC/Diablo and the ratio of Bax/Bcl-2.The biological effects founding of 2d in this work point to prospective uses against acute leukemia.

Synthesis and antitumor activity of a series of novel N-aryl-5-(2,2,2-trifluoroethoxy)-1,5-dihydro-2H-pyrrol-2-ones derivatives.

Mitophagy, the selective removal of damaged mitochondria through autophagy, is crucial for mitochondrial turnover and quality control. Docosahexaenoic acid (DHA), an essential omega-3 fatty acid, protects mitochondria in various diseases. This study aimed to investigate the neuroprotective role of DHA in ischaemic stroke models  and  and its involvement in mitophagy and mitochondrial dysfunction. A mouse model of ischaemic stroke was established through middle cerebral artery occlusion (MCAO). To simulate ischaemic stroke , PC12 cells were subjected to oxygen-glucose deprivation (OGD). Immunofluorescence analysis, western blotting (WB), electron microscopy (EM), functional behavioural tests, and Seahorse assay were used for analysis. DHA treatment significantly alleviated the brain infarction volume, neuronal apoptosis, and behavioural dysfunction in mice with ischaemic stroke. In addition, DHA enhanced mitophagy by significantly increasing the number of autophagosomes and LC3-positive mitochondria in neurons. The Seahorse assay revealed that DHA increased glutamate and succinate metabolism in neurons after ischaemic stroke. JC-1 and MitoSox staining, and evaluation of ATP levels indicated that DHA-induced mitophagy alleviated reactive oxygen species (ROS) accumulation and mitochondrial injury. Mechanistically, DHA improved mitochondrial dynamics by increasing the expression of dynamin-related protein 1 (Drp1), LC3, and the mitophagy clearance protein Pink1/Parkin. Mdivi-1, a specific mitophagy inhibitor, abrogated the neuroprotective effects of DHA, indicating that DHA protected neurons by enhancing mitophagy. Therefore, DHA can protect against neuronal apoptosis after stroke by clearing the damaged mitochondria through Pink1/Parkin-mediated mitophagy and by alleviating mitochondrial dysfunction.

Docosahexaenoic Acid Alleviates Brain Damage by Promoting Mitophagy in Mice with Ischaemic Stroke.

Helicobacter pylori (H. pylori) colonizes the stomach epithelium of half the world's population and is responsible for various digestive diseases and even stomach cancer. Vaccine-mediated protection against H. pylori infection depends primarily on the specific mucosal and T-cell responses. In this study, the synthetic lipopeptide vaccines, Hp4 (Pam Cys modified UreB T-cell epitope) and Hp10 (Pam Cys modified CagA T/B cell combined epitope), not only induce the bone marrow derived dendritic cells (BMDCs) maturation by activating a variety of pattern-recognition receptors (PRRs) such as Toll-like receptor (TLR), Nod-like receptor (NLR), and retinoic acid-inducing gene (RIG) I-like receptor (RLR), and but also stimulate BMDCs to secret cytokines that have the potential to modulate T-cell activation and differentiation. Although intranasal immunization with Hp4 or Hp10 elicits robust epitope-specific T-cell responses in mice, only Hp10 confers protection against H. pylori infection, possibly due to the fact that Hp10 also induces substantial specific sIgA response at mucosal sites. Interestingly, Hp4 elevates the protective response against H. pylori infection of Hp10 when administrated in combination, characterized by better protective effect and enhanced specific T-cell and mucosal antibody responses. The results suggest that synthetic lipopeptide vaccines based on the epitopes derived from the protective antigens are promising candidates for protection against H. pylori infection.

Yan Deng

National Engineering Research Center of Immunological Products,
Department of Microbiology and Biochemical Pharmacy,
College of Pharmacy,
National Engineering Research Center of Immunological Products, Department of Microbiology and Biochemical Pharmacy, College of Pharmacy

Third Military Medical University

Cationic Nanoemulsion-Encapsulated Retinoic Acid as an Adjuvant to Promote OVA-Specific Systemic and Mucosal Responses