AIM To investigate potential effects of poly I:C on mucosal injury and epithelial barrier disruption in dextran sulfate sodium (DSS)-induced acute colitis. METHODS Thirty C57BL/6 mice were given either regular drinkin...AIM To investigate potential effects of poly I:C on mucosal injury and epithelial barrier disruption in dextran sulfate sodium (DSS)-induced acute colitis. METHODS Thirty C57BL/6 mice were given either regular drinking water (control group) or 2% (w/v) DSS drinking water (model and poly I:C groups) ad libitum for 7 d. Poly I:C was administrated subcutaneously (20 mu g/mouse) 2 h prior to DSS induction in mice of the poly I:C group. Severity of colitis was evaluated by disease activity index, body weight, colon length, histology and myeloperoxidase (MPO) activity, as well as the production of proinflammatory cytokines, including tumor necrosis factor-a (TNF-alpha), interleukin 17 (IL-17) and interferon-. (IFN-gamma). Intestinal permeability was analyzed by the fluorescein isothiocyanate labeled-dextran (FITC-D) method. Ultrastructural features of the colon tissue were observed under electron microscopy. Expressions of tight junction (TJ) proteins, including zo-1, occludin and claudin-1, were measured by immunohistochemistry/immunofluorescence, Western blot and real-time quantitative polymerase chain reaction (RT-qPCR). RESULTS DSS caused significant damage to the colon tissue in the model group. Administration of poly I:C dramatically protected against DSS-induced colitis, as demonstrated by less body weight loss, lower disease activity index score, longer colon length, colonic MPO activity, and improved macroscopic and histological scores. It also ameliorated DSS-induced ultrastructural changes of the colon epithelium, as observed under scanning electron microscopy, as well as FITC-D permeability. The mRNA and protein expressions of TJ protein, zo-1, occludin and claudin-1 were also found to be significantly enhanced in the poly I:C group, as determined by immunohistochemistry/immunofluorescence, Western blot and RT-qPCR. By contrast, poly I:C pretreatment markedly reversed the DSS-induced up-regulated expressions of the inflammatory cytokines TNF-alpha, IL-17 and IFN-gamma. CONCLUSION Our study suggested that poly I:C may protect against DSS-induced colitis through maintaining integrity of the epithelial barrier and regulating innate immune responses, which may shed light on the therapeutic potential of poly I:C in human colitis.展开更多
AIM: To study the role of luteolin(LUT) in the expression of toll-like receptors 3(TLR3) ligand poly I:C stimulated inflammatory factors in human corneal fibroblasts(HCFs).METHODS: HCFs cells were cultivated with or w...AIM: To study the role of luteolin(LUT) in the expression of toll-like receptors 3(TLR3) ligand poly I:C stimulated inflammatory factors in human corneal fibroblasts(HCFs).METHODS: HCFs cells were cultivated with or without LUT or poly I:C.The expression levels of interleukin(IL)-6, IL-8, monocyte chemotactic protein-1(MCP-1), vascular cell adhesion molecule(VCAM)-1, as well as intercellular adhesion molecule(ICAM)-1 were measured using enzymelinked immunosorbent assay(ELISA), immunoblotting or reverse transcription-quantitative polymerase chain reaction(PCR) analyses.Immunoblotting was used to assess toll-interleukin-1 receptor-domain-containing adapter-inducing interferon-β(TRIF), TLR3, transforming growth factor-bactivated kinase 1(TAK1), tumor necrosis factor receptor-associated factor 6(TRAF6), the transcription factor AP-1, as well as transcription factor nuclear factor(NF-κB)–inhibitory protein IκB-α degradation and phosphorylation.Immunofluorescence assays were used to localize the cellular location of the p65 subunit of NF-κB.RESULTS: Corneal fibroblasts exposed to poly I:C demonstrated decreased VCAM-1, ICAM-1, MCP-1, IL-6, and IL-8 expression levels upon exposure to LUT in a time-dependent and concentration-dependent manner.LUT was observed to suppress poly I:C-triggered expression of TLR3, the translocation of NF-κB p65 into cell nuclei, as well as the phosphorylation of TAK, c-Jun, and IκB-α, while no impact on the expression levels of TRIF and TRAF6 were observed.CONCLUSION: LUT suppress the expression of proinflammatory adhesion molecules, chemokines, and cytokines in poly I:C exposed HCFs.These effects are likely mediated through TAK/NF-κB signal attenuation.Therefore, LUT is a candidate molecule that can prevent the TLR3-mediated inflammation response associated with corneal viral infection.展开更多
Objective To investigate the immunomodulatory effect of pachymaran on cyclosporine A(CsA)-induced lung injury in mice.Methods(i) Fifty male BALB/c mice were randomly divided into five groups(10 mice in each group): no...Objective To investigate the immunomodulatory effect of pachymaran on cyclosporine A(CsA)-induced lung injury in mice.Methods(i) Fifty male BALB/c mice were randomly divided into five groups(10 mice in each group): normal control(NC) group, 30, 45, and 60 mg/kg CsA groups, and lipopolysaccharide(LPS) group. Except for the NC group, other groups underwent CsA modeling. The NC group was treated with phosphate-buffered saline(PBS), the LPS group with 10 mg/kg LPS eight hours before mice euthanized, and the 30, 45, and 60 mg/kg CsA groups with corresponding doses of CsA for seven consecutive days. After treatment, the body and organ mass of each group were weighed, and the lung, thymus, and spleen indexes were calculated. Hematoxylin-Eosin(HE) staining was performed to observe histopathological changes in the lungs of the mice. The protein expression levels of interleukin(IL)-2 and IL-1β in the blood were detected using enzyme-linked immunosorbent assay(ELISA), and those of surfactant protein D(SP-D), IL-2, and IL-6 in lung tissues were detected by immunohistochemistry(IHC). The mRNA expression levels of SP-D, IL-1β, IL-6, and myeloperoxidase(MPO) in the lung tissues were detected by quantitative reverse transcriptase-polymerase chain reaction(q RT-PCR).(ii) Another 60 BALB/c mice were divided into six groups(10 mice in each group) : NC group,model control(MC) group, 50, 100, and 200 mg/kg pachymaran groups, and polyinosinicpolycytidylic acid [poly(I:C)] group. Except for the NC group, other groups underwent45 mg/kg CsA modeling. The NC and MC groups were treated with distilled water, the pachymaran groups with corresponding doses pachymaran, and the poly(I:C) group with 0.1 mg/kg poly(I:C) for seven days.The mice were euthanized to obtain tissues and serum for detection.Detection methods were identical to those described in(i) above.Results(i) CsA(30 mg/kg) increased the lung index of mice(P < 0.001), and decreased the spleen index(P < 0.01), thymus index(P < 0.05), and the serum level of IL-2(P < 0.05). CsA(45 mg/kg) decreased the spleen, thymus indexes, and the serum level of IL-2(P < 0.01) in mice, and increased the serum level of IL-1β(P < 0.05) and the protein level of lung SP-D(P <0.001). CsA(60 mg/kg) increased the lung index of mice(P < 0.01), the serum level of IL-1β(P < 0.05), the protein level of lung SP-D(P < 0.01), and the mRNA levels of lung MPO and SP-D( P < 0.05), and decreased the thymus index of mice(P < 0.01). HE staining showed that 30, 45, and60 mg/kg CsA, and LPS caused pathological changes in the lung tissue of mice.(ii) After pachymaran intervention in MC mice, the spleen and thymus indexes(P < 0.05) were increased in the 100 and 200 mg/kg pachymaran groups, and the lung index was decreased(P < 0.05).Moreover, 50 mg/kg pachymaran increased the thymus index(P < 0.05) and decreased the lung index(P < 0.01) in MC group. Pachymaran(50, 100, and 200 mg/kg) improved lung tissue injury, reduced the serum level of IL-1β(P < 0.001), and the mRNA levels of MPO and SPD in lung tissues(P < 0.05) of mice. Pachymaran(100 mg/kg) increased the protein level of lung IL-2(P < 0.01), decreased the protein level of lung SP-D(P < 0.01), and the mRNA level of IL-1β(P < 0.001) in the lung tissues of mice. Pachymaran(200 mg/kg) increased the serum level of IL-2(P < 0.01) and lung IL-6 of mice(P < 0.05). Pachymaran(50 and 200 mg/kg) increased the mRNA level of IL-6 in the lung tissues of mice(P < 0.05).Conclusion While the immune function of mice was suppressed by CsA, the lung tissue was also damaged. Pachymaran can improve the immunosuppression induced by CsA and improve the lung tissue injury in immunosuppressed mice.展开更多
A highly immunosuppressive tumor microenvironment(TME)and the presence of the blood‒brain barrier are the two major obstacles to eliciting an effective immune response in patients with high-grade glioma(HGG).Here,we t...A highly immunosuppressive tumor microenvironment(TME)and the presence of the blood‒brain barrier are the two major obstacles to eliciting an effective immune response in patients with high-grade glioma(HGG).Here,we tried to enhance the local innate immune response in relapsed HGG by intracranially injecting poly(I:C)to establish a robust antitumor immune response in this registered clinical trial(NCT03392545).During the follow-up,12/27(44.4%)patients who achieved tumor control concomitant with survival benefit were regarded as responders in our study.We found that the T-cell receptor(TCR)repertoire in the TME was reshaped after poly(I:C)treatment.Based on the RNA-seq analysis of tumor samples,the expression of annexin A1(ANXA1)was significantly upregulated in the tumor cells of nonresponders,which was further validated at the protein level.In vitro and in vivo experiments showed that ANXA1 could induce the production of M2-like macrophages and microglia via its surface receptor formyl peptide receptor 1(FPR1)to establish a Treg cell-driven immunosuppressive TME and suppress the antitumor immune response facilitated by poly(I:C).The ANXA1/FPR1 signaling axis can inhibit the innate immune response of glioma patients by promoting an anti-inflammatory and Treg-driven TME.Moreover,ANXA1 could serve as a reliable predictor of response to poly(I:C),with a notable predictive accuracy rate of 92.3%.In light of these notable findings,this study unveils a new perspective of immunotherapy for gliomas.展开更多
Background The outbreak of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has greatly threatened public health.Recent studies have revealed that the spike receptor-binding domain(RBD)of SARS-CoV-2 is a...Background The outbreak of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has greatly threatened public health.Recent studies have revealed that the spike receptor-binding domain(RBD)of SARS-CoV-2 is a potent target for vaccine development.However,adjuvants are usually required to strengthen the immunogenicity of recombinant antigens.Different types of adjuvants can elicit different immune responses.Methods We developed an RBD recombinant protein vaccine with a polyriboinosinic acid–polyribocytidylic acid[poly(I:C)]adjuvant to evoke a strong immune response.The delivery of poly(I:C)was optimized in two steps.First,poly(I:C)was complexed with a cationic polymer,poly-l-lysine(PLL),to form poly(I:C)–PLL,a polyplex core.Thereafter,it was loaded into five different lipid shells(group II,III-1,2-distearoyl-sn-glycero-3-phosphocholine[DSPC],III-1,2-dioleoyl-sn-glycero-3-phosphoethanolamine[DOPE],IV-DOPE,and IV-DSPC).We performed an enzyme-linked immunosorbent assay and enzyme-linked immunosorbent spot assay to compare the ability of the five lipopolyplex adjuvants to enhance the immunogenicity of the SARS-CoV-2 RBD protein,including humoral and cellular immune responses.Finally,the adjuvant with the highest immunogenicity was selected to verify the protective immunity of the vaccine through animal challenge experiments.Results Recombinant RBD protein has low immunogenicity.The different adjuvants we developed enhanced the immunogenicity of the RBD protein in different ways.Among the lipopolyplexes,those containing DOPE(III-DOPE and IV-DOPE)elicited RBD-specific immunoglobulin G antibody responses,and adjuvants with four components elicited better RBD-specific immunoglobulin G antibody responses than those containing three components(P<0.05).The IC50 and IC90 titers indicated that the IV-DOPE lipopolyplex had the greatest neutralization ability,with IC50 titers of 1/117,490.Furthermore,in the challenge study,IV-DOPE lipopolyplex protected mice from SARS-CoV-2 infection.On the fourth day after infection,the average animal body weights were reduced by 18.56%(24.164±0.665 g vs.19.678±0.455 g)and 0.06%(24.249±0.683 g vs.24.235±0.681 g)in the MOCK and vaccine groups,respectively.In addition,the relative expression of viral RNA in the vaccinated group was significantly lower than that in the MOCK group(P<0.05).Interstitial inflammatory cell infiltration was observed in the MOCK group,whereas no obvious damage was observed in the vaccinated group.Conclusions The IV-DOPE–adjuvanted SARS-CoV-2 recombinant RBD protein vaccine efficiently protected mice from SARS-CoV-2 in the animal challenge study.Therefore,IV-DOPE is considered an exceptional adjuvant for SARS-CoV-2 recombinant RBD protein-based vaccines and has the potential to be further developed into a SARS-CoV-2 recombinant RBD protein-based vaccine.展开更多
基金the Scientific Research Foundation of HealthDepartment of Hebei Province,No.20160483
文摘AIM To investigate potential effects of poly I:C on mucosal injury and epithelial barrier disruption in dextran sulfate sodium (DSS)-induced acute colitis. METHODS Thirty C57BL/6 mice were given either regular drinking water (control group) or 2% (w/v) DSS drinking water (model and poly I:C groups) ad libitum for 7 d. Poly I:C was administrated subcutaneously (20 mu g/mouse) 2 h prior to DSS induction in mice of the poly I:C group. Severity of colitis was evaluated by disease activity index, body weight, colon length, histology and myeloperoxidase (MPO) activity, as well as the production of proinflammatory cytokines, including tumor necrosis factor-a (TNF-alpha), interleukin 17 (IL-17) and interferon-. (IFN-gamma). Intestinal permeability was analyzed by the fluorescein isothiocyanate labeled-dextran (FITC-D) method. Ultrastructural features of the colon tissue were observed under electron microscopy. Expressions of tight junction (TJ) proteins, including zo-1, occludin and claudin-1, were measured by immunohistochemistry/immunofluorescence, Western blot and real-time quantitative polymerase chain reaction (RT-qPCR). RESULTS DSS caused significant damage to the colon tissue in the model group. Administration of poly I:C dramatically protected against DSS-induced colitis, as demonstrated by less body weight loss, lower disease activity index score, longer colon length, colonic MPO activity, and improved macroscopic and histological scores. It also ameliorated DSS-induced ultrastructural changes of the colon epithelium, as observed under scanning electron microscopy, as well as FITC-D permeability. The mRNA and protein expressions of TJ protein, zo-1, occludin and claudin-1 were also found to be significantly enhanced in the poly I:C group, as determined by immunohistochemistry/immunofluorescence, Western blot and RT-qPCR. By contrast, poly I:C pretreatment markedly reversed the DSS-induced up-regulated expressions of the inflammatory cytokines TNF-alpha, IL-17 and IFN-gamma. CONCLUSION Our study suggested that poly I:C may protect against DSS-induced colitis through maintaining integrity of the epithelial barrier and regulating innate immune responses, which may shed light on the therapeutic potential of poly I:C in human colitis.
基金Supported by the National Natural Science Foundation of China (No.81770889)Administration of Traditional Chinese Medicine of Guangdong Province (No.20201070)。
文摘AIM: To study the role of luteolin(LUT) in the expression of toll-like receptors 3(TLR3) ligand poly I:C stimulated inflammatory factors in human corneal fibroblasts(HCFs).METHODS: HCFs cells were cultivated with or without LUT or poly I:C.The expression levels of interleukin(IL)-6, IL-8, monocyte chemotactic protein-1(MCP-1), vascular cell adhesion molecule(VCAM)-1, as well as intercellular adhesion molecule(ICAM)-1 were measured using enzymelinked immunosorbent assay(ELISA), immunoblotting or reverse transcription-quantitative polymerase chain reaction(PCR) analyses.Immunoblotting was used to assess toll-interleukin-1 receptor-domain-containing adapter-inducing interferon-β(TRIF), TLR3, transforming growth factor-bactivated kinase 1(TAK1), tumor necrosis factor receptor-associated factor 6(TRAF6), the transcription factor AP-1, as well as transcription factor nuclear factor(NF-κB)–inhibitory protein IκB-α degradation and phosphorylation.Immunofluorescence assays were used to localize the cellular location of the p65 subunit of NF-κB.RESULTS: Corneal fibroblasts exposed to poly I:C demonstrated decreased VCAM-1, ICAM-1, MCP-1, IL-6, and IL-8 expression levels upon exposure to LUT in a time-dependent and concentration-dependent manner.LUT was observed to suppress poly I:C-triggered expression of TLR3, the translocation of NF-κB p65 into cell nuclei, as well as the phosphorylation of TAK, c-Jun, and IκB-α, while no impact on the expression levels of TRIF and TRAF6 were observed.CONCLUSION: LUT suppress the expression of proinflammatory adhesion molecules, chemokines, and cytokines in poly I:C exposed HCFs.These effects are likely mediated through TAK/NF-κB signal attenuation.Therefore, LUT is a candidate molecule that can prevent the TLR3-mediated inflammation response associated with corneal viral infection.
基金National Natural Science Foundation of China (8207425)Hunan Provincial Natural Science Foundation(2021JJ30508 and 2020JJ4063)+3 种基金Hunan Provincial Scientific Research Project of Chinese Medicine (2021055)Changsha Outstanding and Innovative Youth Training Program (kq2106060)Key Discipline of Hunan University of Chinese Medicine (Basic Medicine 1)the Excellent Teaching Team of Postgraduates in Hunan Province (Postgraduate Teaching Team of Basic Medicine, 118)。
文摘Objective To investigate the immunomodulatory effect of pachymaran on cyclosporine A(CsA)-induced lung injury in mice.Methods(i) Fifty male BALB/c mice were randomly divided into five groups(10 mice in each group): normal control(NC) group, 30, 45, and 60 mg/kg CsA groups, and lipopolysaccharide(LPS) group. Except for the NC group, other groups underwent CsA modeling. The NC group was treated with phosphate-buffered saline(PBS), the LPS group with 10 mg/kg LPS eight hours before mice euthanized, and the 30, 45, and 60 mg/kg CsA groups with corresponding doses of CsA for seven consecutive days. After treatment, the body and organ mass of each group were weighed, and the lung, thymus, and spleen indexes were calculated. Hematoxylin-Eosin(HE) staining was performed to observe histopathological changes in the lungs of the mice. The protein expression levels of interleukin(IL)-2 and IL-1β in the blood were detected using enzyme-linked immunosorbent assay(ELISA), and those of surfactant protein D(SP-D), IL-2, and IL-6 in lung tissues were detected by immunohistochemistry(IHC). The mRNA expression levels of SP-D, IL-1β, IL-6, and myeloperoxidase(MPO) in the lung tissues were detected by quantitative reverse transcriptase-polymerase chain reaction(q RT-PCR).(ii) Another 60 BALB/c mice were divided into six groups(10 mice in each group) : NC group,model control(MC) group, 50, 100, and 200 mg/kg pachymaran groups, and polyinosinicpolycytidylic acid [poly(I:C)] group. Except for the NC group, other groups underwent45 mg/kg CsA modeling. The NC and MC groups were treated with distilled water, the pachymaran groups with corresponding doses pachymaran, and the poly(I:C) group with 0.1 mg/kg poly(I:C) for seven days.The mice were euthanized to obtain tissues and serum for detection.Detection methods were identical to those described in(i) above.Results(i) CsA(30 mg/kg) increased the lung index of mice(P < 0.001), and decreased the spleen index(P < 0.01), thymus index(P < 0.05), and the serum level of IL-2(P < 0.05). CsA(45 mg/kg) decreased the spleen, thymus indexes, and the serum level of IL-2(P < 0.01) in mice, and increased the serum level of IL-1β(P < 0.05) and the protein level of lung SP-D(P <0.001). CsA(60 mg/kg) increased the lung index of mice(P < 0.01), the serum level of IL-1β(P < 0.05), the protein level of lung SP-D(P < 0.01), and the mRNA levels of lung MPO and SP-D( P < 0.05), and decreased the thymus index of mice(P < 0.01). HE staining showed that 30, 45, and60 mg/kg CsA, and LPS caused pathological changes in the lung tissue of mice.(ii) After pachymaran intervention in MC mice, the spleen and thymus indexes(P < 0.05) were increased in the 100 and 200 mg/kg pachymaran groups, and the lung index was decreased(P < 0.05).Moreover, 50 mg/kg pachymaran increased the thymus index(P < 0.05) and decreased the lung index(P < 0.01) in MC group. Pachymaran(50, 100, and 200 mg/kg) improved lung tissue injury, reduced the serum level of IL-1β(P < 0.001), and the mRNA levels of MPO and SPD in lung tissues(P < 0.05) of mice. Pachymaran(100 mg/kg) increased the protein level of lung IL-2(P < 0.01), decreased the protein level of lung SP-D(P < 0.01), and the mRNA level of IL-1β(P < 0.001) in the lung tissues of mice. Pachymaran(200 mg/kg) increased the serum level of IL-2(P < 0.01) and lung IL-6 of mice(P < 0.05). Pachymaran(50 and 200 mg/kg) increased the mRNA level of IL-6 in the lung tissues of mice(P < 0.05).Conclusion While the immune function of mice was suppressed by CsA, the lung tissue was also damaged. Pachymaran can improve the immunosuppression induced by CsA and improve the lung tissue injury in immunosuppressed mice.
基金supported by a grant from the National Natural Science Foundation of China(81771309,31930039 and 31821003 to Xin Lin and 82202983 to Haihui Jiang)supported by grants from the Capital’s Funds for Health Improvement and Research(2020-2-1075 to Yong Cui)the National Key Research and Development Program of China(2019YFA0508502 to Xin Lin).
文摘A highly immunosuppressive tumor microenvironment(TME)and the presence of the blood‒brain barrier are the two major obstacles to eliciting an effective immune response in patients with high-grade glioma(HGG).Here,we tried to enhance the local innate immune response in relapsed HGG by intracranially injecting poly(I:C)to establish a robust antitumor immune response in this registered clinical trial(NCT03392545).During the follow-up,12/27(44.4%)patients who achieved tumor control concomitant with survival benefit were regarded as responders in our study.We found that the T-cell receptor(TCR)repertoire in the TME was reshaped after poly(I:C)treatment.Based on the RNA-seq analysis of tumor samples,the expression of annexin A1(ANXA1)was significantly upregulated in the tumor cells of nonresponders,which was further validated at the protein level.In vitro and in vivo experiments showed that ANXA1 could induce the production of M2-like macrophages and microglia via its surface receptor formyl peptide receptor 1(FPR1)to establish a Treg cell-driven immunosuppressive TME and suppress the antitumor immune response facilitated by poly(I:C).The ANXA1/FPR1 signaling axis can inhibit the innate immune response of glioma patients by promoting an anti-inflammatory and Treg-driven TME.Moreover,ANXA1 could serve as a reliable predictor of response to poly(I:C),with a notable predictive accuracy rate of 92.3%.In light of these notable findings,this study unveils a new perspective of immunotherapy for gliomas.
文摘Background The outbreak of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has greatly threatened public health.Recent studies have revealed that the spike receptor-binding domain(RBD)of SARS-CoV-2 is a potent target for vaccine development.However,adjuvants are usually required to strengthen the immunogenicity of recombinant antigens.Different types of adjuvants can elicit different immune responses.Methods We developed an RBD recombinant protein vaccine with a polyriboinosinic acid–polyribocytidylic acid[poly(I:C)]adjuvant to evoke a strong immune response.The delivery of poly(I:C)was optimized in two steps.First,poly(I:C)was complexed with a cationic polymer,poly-l-lysine(PLL),to form poly(I:C)–PLL,a polyplex core.Thereafter,it was loaded into five different lipid shells(group II,III-1,2-distearoyl-sn-glycero-3-phosphocholine[DSPC],III-1,2-dioleoyl-sn-glycero-3-phosphoethanolamine[DOPE],IV-DOPE,and IV-DSPC).We performed an enzyme-linked immunosorbent assay and enzyme-linked immunosorbent spot assay to compare the ability of the five lipopolyplex adjuvants to enhance the immunogenicity of the SARS-CoV-2 RBD protein,including humoral and cellular immune responses.Finally,the adjuvant with the highest immunogenicity was selected to verify the protective immunity of the vaccine through animal challenge experiments.Results Recombinant RBD protein has low immunogenicity.The different adjuvants we developed enhanced the immunogenicity of the RBD protein in different ways.Among the lipopolyplexes,those containing DOPE(III-DOPE and IV-DOPE)elicited RBD-specific immunoglobulin G antibody responses,and adjuvants with four components elicited better RBD-specific immunoglobulin G antibody responses than those containing three components(P<0.05).The IC50 and IC90 titers indicated that the IV-DOPE lipopolyplex had the greatest neutralization ability,with IC50 titers of 1/117,490.Furthermore,in the challenge study,IV-DOPE lipopolyplex protected mice from SARS-CoV-2 infection.On the fourth day after infection,the average animal body weights were reduced by 18.56%(24.164±0.665 g vs.19.678±0.455 g)and 0.06%(24.249±0.683 g vs.24.235±0.681 g)in the MOCK and vaccine groups,respectively.In addition,the relative expression of viral RNA in the vaccinated group was significantly lower than that in the MOCK group(P<0.05).Interstitial inflammatory cell infiltration was observed in the MOCK group,whereas no obvious damage was observed in the vaccinated group.Conclusions The IV-DOPE–adjuvanted SARS-CoV-2 recombinant RBD protein vaccine efficiently protected mice from SARS-CoV-2 in the animal challenge study.Therefore,IV-DOPE is considered an exceptional adjuvant for SARS-CoV-2 recombinant RBD protein-based vaccines and has the potential to be further developed into a SARS-CoV-2 recombinant RBD protein-based vaccine.
