The receptor‐binding domain (RBD) of the SARS‐CoV‐2 spike protein is a candidate vaccine antigen that binds angiotensin‐converting enzyme 2 (ACE2), leading to virus entry. Here, it is shown that rapid conversion of recombinant RBD into particulate form via admixing with liposomes containing cobalt‐porphyrin‐phospholipid (CoPoP) potently enhances the functional antibody response. Antigen binding via His‐tag insertion into the CoPoP bilayer results in a serum‐stable and conformationally intact display of the RBD on the liposome surface. Compared to other vaccine formulations, immunization using CoPoP liposomes admixed with recombinant RBD induces multiple orders of magnitude higher levels of antibody titers in mice that neutralize pseudovirus cell entry, block RBD interaction with ACE2, and inhibit live virus replication. Enhanced immunogenicity can be accounted for by greater RBD uptake into antigen‐presenting cells in particulate form and improved immune cell infiltration in draining lymph nodes. QS‐21 inclusion in the liposomes results in an enhanced antigen‐specific polyfunctional T cell response. In mice, high dose immunization results in minimal local reactogenicity, is well‐tolerated, and does not elevate serum cobalt levels. Taken together, these results confirm that particulate presentation strategies for the RBD immunogen should be considered for inducing strongly neutralizing antibody responses against SARS‐CoV‐2.
Bone metastasis of breast cancer makes patients suffer from pain, fractures, spinal cord compression, and hypercalcemia, and is almost incurable. Although the mechanisms of bone metastasis in breast cancers have been studied intensively, novel specific target will be helpful to the development of new therapeutic strategy of breast cancer. Herein, we focused on the microRNA of tumor cell‐derived exosomes to investigate the communication between the bone microenvironment and tumor cells. The expression of miR‐20a‐5p in the primary murine bone marrow macrophages (BMMs), MCF‐10A, MCF‐7, and MDA‐MB‐231 cell lines, as well as the cell‐derived exosomes were assessed by qRT‐PCR. Transwell assays were used to evaluate the effects of miR‐20a‐5p on tumor cell migration and invasion. The expression of exosomes marker including CD63and TSG101 was detected by Western Blot. Cell cycle distribution of BMMs was analyzed by flow cytometry. 3‐UTR luciferase reporter assays were used to validate the putative binding between miR‐20a‐5p and SRCIN1. MiR‐20a‐5p was highly expressed in breast tumor tissues and the exosomes of MDA‐MB‐231 cells. MiR‐20a‐5p promoted migration and invasion in MDA‐MB‐231 cells, and the proliferation and differentiation of osteoclasts. MDA‐MB‐231 cell‐derived exosomes transferred miR‐20a‐5p to BMMs and facilitated the osteoclastogenesis via targeting SRCIN1. The present work provides evidence that miR‐20a‐5p transferred from breast cancer cell‐derived exosomes promotes the proliferation and differentiation of osteoclasts by targeting SRCIN1, providing scientific foundations for the development of exosome or miR‐20a‐5p targeted therapeutic intervention in breast cancer progression.
Short major histocompatibility complex (MHC) class I (MHC-I)-restricted peptides contain the minimal biochemical information to induce antigen (Ag)-specific CD8+ cytotoxic T cell responses but are generally ineffective in doing so. To address this, we developed a cobalt–porphyrin (CoPoP) liposome vaccine adjuvant system that induces rapid particleization of conventional, short synthetic MHC-I epitopes, leading to strong cellular immune responses at nanogram dosing. Along with CoPoP (to induce particle formation of peptides), synthetic monophosphoryl lipid A (PHAD) and QS-21 immunostimulatory molecules were included in the liposome bilayer to generate the “CPQ” adjuvant system. In mice, immunization with a short MHC-I-restricted peptide, derived from glycoprotein 70 (gp70), admixed with CPQ safely generated functional, Ag-specific CD8+ T cells, resulting in the rejection of multiple tumor cell lines, with durable immunity. When cobalt was omitted, the otherwise identical peptide and adjuvant components did not result in peptide binding and were incapable of inducing immune responses, demonstrating the importance of stable particle formation. Immunization with the liposomal vaccine was well-tolerated and could control local and metastatic disease in a therapeutic setting. Mechanistic studies showed that particle-based peptides were better taken up by antigen-presenting cells, where they were putatively released within endosomes and phagosomes for display on MHC-I surfaces. On the basis of the potency of the approach, the platform was demonstrated as a tool for in vivo epitope screening of peptide microlibraries comprising a hundred peptides.
HPVs are also related to penile, vulvar and anal carcinomas, and more than 40% of oropharyngeal cancers. [3,4] Prophylactic HPV vaccines (i.e., Gardasil and Cervarix) generate neutralizing capsid antibodies against the virus and represent the most successful cancer vaccines, having been adopted into national immunization programs in most industrial nations, preventing significant numbers of cancer deaths. [5] However, there are currently no HPV therapeutic vaccines approved for use in humans against established malignancies, which require strong cellular immune responses rather than humoral ones. The HPV-16 cellular oncoproteins E6 and E7 (E6/E7) transform infected cells, are expressed constitutively at high levels, and represent potential rejection antigens (Ags) for therapeutic HPV vaccines. [6-8] Clinical cervical cancer trials have been carried out using epitopes derived from the E6/E7 oncogenes. [9-11] For preclinical HPV-expressing tumor research, the TC-1 murine cell-line, which expresses E6/E7, has been widely used. [12] Many approaches have been examined for enhancing the cellular immune responses against E6/E7, including the use of live-vector vaccines that spread Ag inside host cells, [9,13,14] proteins, [15,16] nucleic acids, [17] cells, [18] peptide vaccines, [19] and combinatorial approaches. [20] Among these strategies, short peptide vaccines (i.e., ≈8-12 amino acids in length) corresponding to CD8 + T-cell epitopes are likely the simplest to produce. However, they often suffer from poor immunogenicity. To bypass this, peptide sequences can be elongated to generate synthetic long peptides (SLPs) that cover both CD4 + and CD8 + T-cell epitopes. [21-26] In clinical trials, SLPs induced the regression of premalignant lesions in early stage but not late-stage HPV16 + cervical cancer patients. [19,27] Another way to enhance the immunogenicity of short peptide is to include strong adjuvants or peptide delivery systems to induce tumor Ag-specific CD8 + T cells. [28,29] This has been done in clinical trials using short peptides derived from E7 with incomplete Freund's adjuvant, for example. [11] In preclinical studies, numerous experimental approaches have been explored, frequently using the short E7 49-57 epitope (sequence: RAHYNIVTF) along with virus-like particles, [30] very small Human papilloma virus (HPV)-16 is associated with cervical cancers and induces expression of the E6 and E7 oncogenes. Using a murine cell line that expresses these, the genes are sequenced, and six predicted major histocompatibility complex (MHC) class I (MHC-I) epitopes are identified. A liposomal vaccine adjuvant based on cobalt-porphyrin-phospholipid (CoPoP) is admixed with synthetic 9-mer epitopes appended with three histidine residues, resulting in rapid formation of peptide-liposome particles. Immunization with multivalent peptides leads to protection from tumor challenge. Of the peptides screened, only the previously identified E7 49-57 epitope is functional. The peptide-liposome particles that form upon mixing E7 HHH49...
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