Immunostimulatory Activities of CpG-Oligodeoxynucleotides in Teleosts: Toll-Like Receptors 9 and 21

The interactions between CpG oligodeoxynucleotides and Toll-like receptors in Pacific white shrimp Litopenaeus vannamei

CpG oligodeoxynucleotides (ODNs), as a novel type of adjuvant with immunomodulatory effects, are recognized by Toll-like receptors (TLRs) in Litopenaeus vannamei. In the present study, eleven LvTLRs-pCMV recombinants (rLvTLRs) were constructed to investigate the relationships between various CpG ODNs and different LvTLRs in human embryonic kidney 293T (HEK293T) cells, which was further confirmed by bio-layer interferometry (BLI) technique. The results of dual luciferase reporter assay showed that every LvTLR could activate multiple downstream genes, mainly including NF-κB, CREB, ISRE, IL-6-promoter, TNF-α-promoter and Myc, thereby inducing main signaling pathways in shrimps. Most CpG ODNs possessed affinities to more than one LvTLR, while each LvTLR could recognize multiple CpG ODNs, and the widely recognized ligands within CpG ODNs are A-class and B-class. Moreover, BLI analysis showed that CpG 2216, Cpg 2006, CpG 2143 and CpG 21425 exhibited dose-dependent affinity to the expressed TLR protein, which were consistent with the results in HEK293T cells. It suggested that the interactions of CpG ODNs with LvTLRs were indispensable for the immune regulation triggered by CpG ODNs, and these findings would lay foundations for studying the activations of LvTLRs to immune signaling pathways and shedding lights on the immune functions and mechanisms of CpG ODNs.

Hypermethylated genome of a fish vertebrate iridovirus ISKNV plays important roles in viral infection

Iridoviruses are nucleocytoplasmic large dsDNA viruses that infect invertebrates and ectothermic vertebrates. The hypermethylated genome of vertebrate iridoviruses is unique among animal viruses. However, the map and function of iridovirus genomic methylation remain unknown. Herein, the methylated genome of Infectious spleen and kidney necrosis virus (ISKNV, a fish iridovirus), and its role in viral infection, are investigated. The methylation level of ISKNV is 23.44%. The hypermethylated genome is essential for ISKNV amplification, but there is no correlation between hypermethylation and viral gene expression. The hypomethylated ISKNV (obtained via 5-Azacytidine) activates a strong immunoreaction in vitro and reduces its pathogenicity in vivo. The unmethylated viral DNA can induce a stronger immunoreaction in vitro, whereas inactivated hypomethylated ISKNV can induce a stronger immunoreaction in vivo, suggesting ISKNV may evade from immune system by increasing its genome methylation level. Our work provides new insights into the role of genome methylation in viral infection.

Injectable hydrogels for personalized cancer immunotherapies

The field of cancer immunotherapy has shown significant growth, and researchers are now focusing on effective strategies to enhance and prolong local immunomodulation. Injectable hydrogels (IHs) have emerged as versatile platforms for encapsulating and controlling the release of small molecules and cells, drawing significant attention for their potential to enhance antitumor immune responses while inhibiting metastasis and recurrence. IHs delivering natural killer (NK) cells, T cells, and antigen-presenting cells (APCs) offer a viable method for treating cancer. Indeed, it can bypass the extracellular matrix and gradually release small molecules or cells into the tumor microenvironment, thereby boosting immune responses against cancer cells. This review provides an overview of the recent advancements in cancer immunotherapy using IHs for delivering NK cells, T cells, APCs, chemoimmunotherapy, radio-immunotherapy, and photothermal-immunotherapy. First, we introduce IHs as a delivery matrix, then summarize their applications for the local delivery of small molecules and immune cells to elicit robust anticancer immune responses. Additionally, we discuss recent progress in IHs systems used for local combination therapy, including chemoimmunotherapy, radio-immunotherapy, photothermal-immunotherapy, photodynamic-immunotherapy, and gene-immunotherapy. By comprehensively examining the utilization of IHs in cancer immunotherapy, this review aims to highlight the potential of IHs as effective carriers for immunotherapy delivery, facilitating the development of innovative strategies for cancer treatment. In addition, we demonstrate that using hydrogel-based platforms for the targeted delivery of immune cells, such as NK cells, T cells, and dendritic cells (DCs), has remarkable potential in cancer therapy. These innovative approaches have yielded substantial reductions in tumor growth, showcasing the ability of hydrogels to enhance the efficacy of immune-based treatments. STATEMENT OF SIGNIFICANCE: As cancer immunotherapy continues to expand, the mode of therapeutic agent delivery becomes increasingly critical. This review spotlights the forward-looking progress of IHs, emphasizing their potential to revolutionize localized immunotherapy delivery. By efficiently encapsulating and controlling the release of essential immune components such as T cells, NK cells, APCs, and various therapeutic agents, IHs offer a pioneering pathway to amplify immune reactions, moderate metastasis, and reduce recurrence. Their adaptability further shines when considering their role in emerging combination therapies, including chemoimmunotherapy, radio-immunotherapy, and photothermal-immunotherapy. Understanding IHs' significance in cancer therapy is essential, suggesting a shift in cancer treatment dynamics and heralding a novel period of focused, enduring, and powerful therapeutic strategies.

Control of A/D type CpG-ODN aggregates to a suitable size for induction of strong immunostimulant activity

Among several types of CpG-ODNs, A/D-type CpG-ODNs have potent adjuvant activity to induce Th-1 immune responses, but exhibit a propensity to aggregate. For the clinical application of A/D-type CpG-ODNs, it is necessary to control such aggregation and obtain a comprehensive understanding of the relationship between their structure and the immune responses. This study revealed that a representative A/D-type CpG ODN, D35, adopted a single-stranded structure in water, while it assembled into aggregates in response to Na+ ions. From polyacrylamide gel electrophoresis and circular dichroism analyses, D35 adopted a homodimeric form (duplex) via palindromic sequences in low-Na+-concentration conditions (10-50 mM NaCl). After replacement of the solution with PBS, quadruplexes began to form in a manner coordinated by Na+, resulting in large aggregates. The duplexes and small aggregates prepared in 50 mM NaCl showed not only high cellular uptake but also high affinity to Toll-like receptor 9 (TLR9) proteins, leading to the production of a large amount of interferon-α for peripheral blood mononuclear cells. The much larger aggregates prepared in 100 mM NaCl were incorporated into cells at a high level, but showed a low ability to induce cytokine production. This suggests that the large aggregates have difficulty inducing TLR9 dimerization, resulting in loss of the stimulation of the cells. We thus succeeded in inducing adequate innate immunity in vitro by controlling and adjusting the formation of D35 aggregates. Therefore, the findings in this study for D35 ODNs could be a vital research foundation for in vivo applications.

Immunogenicity of rabies virus G mRNA formulated with lipid nanoparticles and nucleic acid immunostimulators in mice

Rabies is a preventable zoonotic disease caused by rabies virus (RABV) with high mortality. Messenger RNA (mRNA) vaccines have opened up new avenues for vaccine development and pandemic preparedness with potent scalability, which may overcome the only licensed rabies inactived vaccine' shortcoming of time and cost wasting. Here, we designed an RABV mRNA vaccines expressed RABV G protein and capsulated with lipid nanoparticle (LNP) and different nucleic acid immunostimulator (CPG 1018, CPG 2395 and Poly I:C) and then assessed the immunogenicity and protective capacity in mice. While RABV mRNA capsulated with LNP and CPG 1018 could induce more potent humoral response with highest and durable RABV-G specific IgG titers and virus neutralizing titers, but also induced stronger RABV G-specific cell-mediated immunity (CMI) responses, including the highest proportions of interferon-γ (IFN-γ) and tumor necrosis factor alpha (TNFα)- producing CD4+/CD8 + T cells according to a flow cytometry assay in mice. In addition, in the pre- and post-exposure challenge assays, LNP + CPG 1018 capsulated RABV G mRNA induced 100 % protection against 25 LD50 of RABV infection with highest inhibition efficacy of viral replication with the decreased virus genome detected by qRT-PCR. These results showed that RABV G mRNA capsulated with LNP immune-stimulating nucleic acids CPG 1018 showed promise as a safe and economical rabies vaccine candidate.

Programming Cell-Derived Vesicles with Enhanced Immunomodulatory Properties

Tumor-associated macrophages are the predominant immune cells present in the tumor microenvironment and mostly exhibit a pro-tumoral M2-like phenotype. However, macrophage biology is reversible allowing them to acquire an anti-tumoral M1-like phenotype in response to external stimuli. A potential therapeutic strategy for treating cancer may be achieved by modulating macrophages from an M2 to an M1-like phenotype with the tumor microenvironment. Here, programmed nanovesicles are generated as an immunomodulatory therapeutic platform with the capability to re-polarize M2 macrophages toward a proinflammatory phenotype. Programmed nanovesicles are engineered from cellular membranes to have specific immunomodulatory properties including the capability to bidirectionally modulate immune cell polarization. These programmed nanovesicles decorated with specific membrane-bound ligands can be targeted toward specific cell types including immune cells. Macrophage-derived vesicles are engineered to enhance immune cell reprogramming toward a proinflammatory phenotype.

Development of Long Asymmetric siRNA Structure for Target Gene Silencing and Immune Stimulation in Mammalian Cells

Post-transcriptional regulation of transcript abundances by RNA interference (RNAi) is a widely conserved regulatory mechanism to control cellular processes. We previously introduced an alternative siRNA structure called asymmetric siRNA (asiRNA), and showed that asiRNA exhibits comparable gene-silencing efficiency with reduced off-target effects compared with conventional siRNAs. However, to what extent the length of the guide strand affects the gene-silencing efficiency of asiRNAs is still elusive. In this study, we analyzed in detail the gene-silencing ability of asiRNAs along the guide strand length and immunostimulatory capacity of asiRNAs. We generated asiRNAs containing various guide strand lengths ranging from 25 to 29 nt, called long asiRNA (lasiRNA). We found that the gene-silencing activity of lasiRNAs decreased as the length of the guide strand increased. Nonetheless, the 3'-end overhangs that are complementary to the target gene have higher efficiency for gene silencing compared with mismatched overhangs. In addition, we found that the silencing efficiency of lasiRNAs correlates with their Ago2-binding affinity. Finally, replacing the mismatched overhang with a TLR7- or TLR9-associated immune response motif induced a toll-like receptor (TLR)-specific immune response and retained gene-silencing activity. Our findings demonstrate that lasiRNA structures can be tailored to function as bifunctional siRNA, which trigger a specific immune response combined with target gene silencing. Taken together, we anticipate that our findings provide a road map for the subsequent development of immune-stimulating lasiRNA, which bear the potential to be applied for therapeutic benefits.

CpG ODN 1668 as TLR9 agonist mediates humpback grouper (Cromileptes altivelis) antibacterial immune responses

Cromileptes altivelis (humpback grouper) is the main farmed species in the southern coastal area of China owing to its important economic value. Toll-like receptor 9 (TLR9) belongs to the toll-like receptor (TLR) family and functions as a pattern recognition receptor, recognising unmethylated oligodeoxynucleotides containing the CpG motif (CpG ODNs) in bacterial and viral genomes, thereby activating host immune response. In this study, the C. altivelis TLR9 (CaTLR9) ligand CpG ODN 1668 was screened and found to significantly enhance the antibacterial immunity of humpback grouper in vivo and head kidney lymphocytes (HKLs) in vitro. In addition, CpG ODN 1668 also promoted the cell proliferation and immune gene expression of HKLs and strengthened the phagocytosis activity of head kidney macrophages. However, when the CaTLR9 expression was knocked down in the humpback group, the expression levels of TLR9, myeloid differentiation factor 88 (Myd88), tumour necrosis factor-α (TNF-α), interferon γ (IFN-γ), interleukin-1β (IL-1β), IL-6, and IL-8 were significantly reduced, and the antibacterial immune effects induced by CpG ODN 1668 were mostly abolished. Therefore, CpG ODN 1668 induced antibacterial immune responses in a CaTLR9-dependent pathway. These results enhance the knowledge of the antibacterial immunity of fish TLR signalling pathways and have important implications for exploring natural antibacterial molecules in fish.

CpG ODN 2102 promotes antibacterial immune responses and enhances vaccine-induced protection in golden pompano (Trachinotusovatus)

CpG oligodeoxynucleotides (ODNs) are oligodeoxynucleotides containing CpG motifs and can be recognized by toll-like receptor 9 (TLR9), activating the host's immune responses. In this study, ten different CpG ODNs were designed and synthesized to study the antibacterial immune responses of CpG ODNs in golden pompano (Trachinotus ovatus). Results showed that CpG ODN 2102 significantly improved the immunity of golden pompano against bacteria. Besides, CpG ODN 2102 promoted the proliferation of head kidney lymphocytes and activated the head kidney macrophages. When TLR9-specific small interfering RNA (siRNA) was used to interfere with TLR9 expression, the immune responses were decreased. Moreover, the expression levels of myeloid differentiation primary response 88 (Myd88), p65, tumor necrosis factor receptor-associated factor 6 (TRAF6), and tumor necrosis factor-alpha (TNF-α) in the TLR9-knockdown golden pompano kidney (GPK) cells were significantly reduced. The nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) promoter activity of the TLR9-knockdown GPK cells was also significantly reduced. In vivo, the antibacterial immune effects induced by CpG ODN 2102 in golden pompano were mostly abolished when TLR9 expression was knocked down. These results suggested that TLR9 was involved in the immune responses induced by CpG ODN 2102. CpG ODN 2102 also enhanced the protective effect of the Vibrio harveyi vaccine pCTssJ, where the survival rate of golden pompano was significantly improved by 20%. In addition, CpG ODN 2102 enhanced the messenger RNA (mRNA) expression levels of TLR9, Myxovirus resistance (Mx), interferon γ (IFN-γ), TNF-α, interleukin (IL)-1β, IL-8, major histocompatibility complex class (MHC) Iα, MHC IIα, Immunoglobulin D (IgD), and IgM. Therefore, TLR9 was involved in the antibacterial immune responses induced by CpG ODN 2102 and CpG ODN 2102 possessed adjuvant immune effects. These results enlarged our knowledge of the antibacterial immunity of fish TLRs signaling pathway and had important implications for exploring natural antibacterial molecules in fish and developing new vaccine adjuvants.

Novel adjuvant nano-vaccine induced immune response against Acinetobacter baumannii

Developing adjuvant vaccines to combat rising multidrug-resistant (MDR) Acinetobacter baumannii (A. baumannii) infections is a promising and cost-effective approach. The aim of this analysis was to construct a pDNA-CPG C274-adjuvant nano-vaccine and investigate its immunogenicity and protection in BALB/c mice. The CPG ODN C274 adjuvant was chemically synthesized and cloned into pcDNA3.1( +), and the cloning was verified using PCR and BamHI/EcoRV restriction enzyme digestion. Then, utilizing a complex coacervation approach, pDNA-CPG C274 was encapsulated by chitosan (CS) nanoparticles (NPs). TEM and DLS are used to explore the properties of the pDNA/CSNP complex. TLR-9 pathway activation was investigated in human HEK-293 and RAW 264.7 mouse cells. The vaccine's immunogenicity and immune-protective effectiveness were investigated in BALB/c mice. The pDNA-CPG C274/CSNPs were small (mean size 79.21 ± 0.23 nm), positively charged (+ 38.87 mV), and appeared to be spherical. A continuous slow release pattern was achieved. TLR-9 activation was greatest in the mouse model with CpG ODN (C274) at concentrations of 5 and 10 μg/ml with 56% and 55%, respectively (**P < 0.01). However, in HEK-293 human cells, by increasing the concentration of CpG ODN (C274) from 1 to 50 μg/ml, the activation rate of TLR-9 also increased, so that the highest activation rate (81%) was obtained at the concentration of 50 μg/ml (***P < 0.001). pDNA-CPG C274/CSNPs immunized BALB/c mice produced increased amounts of total-IgG, as well as IFN-γ and IL-1B in serum samples, compared to non-encapsulated pDNA-CPG C274. Furthermore, liver and lung injuries, as well as bacterial loads in the liver, lung, and blood, were reduced, and BALB/c mice immunized with pDNA-CPG C274/CSNPs showed potent protection (50-75%) against acute fatal Intraperitoneal A. baumannii challenge. pDNA-CPG C274/CSNPs evoked total-IgG antibodies, Th1 cellular immunity, and the TLR-9 pathway, as well as protection against an acute fatal A. baumannii challenge. Our findings suggest that this nano-vaccine is a promising approach for avoiding A. baumannii infection when used as a powerful adjuvant.

Regulatory Effects of Clock and Bmal1 on Circadian Rhythmic TLR Expression

Circadian locomotor output cycles kaput (Clock) and brain and muscle ARNT-like 1 (Bmal1) are two core circadian clock genes. They form a heterodimer that can bind to the E-box element in the promoters of Period circadian protein (Per) and Cryptochrome (Cry) genes, thereby inducing the rhythmic expression of circadian clock control genes. Toll-like receptors (TLRs) are type I transmembrane proteins belonging to the pattern recognition receptor (PRR) family. They can recognize a variety of pathogens and play an important role in innate immunity and adaptive immune responses. Recent studies have found that the circadian clock is closely associated with the immune system. TLRs have a certain correlation with the circadian rhythms; Bmal1 seems to be the central mediator connecting the circadian clock and the immune system. Research on Bmal1 and TLRs has made some progress, but the specific relationship between TLRs and Bmal1 remains unclear. Understanding the relationship between TLRs and Clock/Bmal1 genes is increasingly important for basic research and clinical treatment.

Tyrosinase-Related Protein2 Peptide with Replacement of N-Terminus Residue by Cysteine Binds to H-2Kb and Induces Antigen-Specific Cytotoxic T Lymphocytes after Conjugation with CpG-DNA

Recent studies have shown the potent efficacy of peptide-based vaccines for cancer immunotherapy. Immunological performance is optimized through the co-delivery of adjuvant and antigenic peptide molecules to antigen-presenting cells simultaneously. In our previous study, we showed that a conjugate consisting of 40-mer CpG-DNA and an antigenic ovalbumin peptide through disulfide bonding could efficiently induce ovalbumin-specific cytotoxic T lymphocyte (CTL) responses in vivo. In this study, based on the conjugation design, we prepared a conjugate consisting of 30-mer CpG-DNA (CpG30) and a cancer antigenic peptide of Tyrosinase-related protein 2 (TRP2_180-188) using a cysteine residue attached at the N-terminus of TRP2_180-188. However, the immunization of mice with this conjugate did not induce efficient TRP2_180-188-specific immune responses. It was thought that the resultant peptide (10-mer) cleaved from the conjugate might be too long to fit into the H-2K^b molecule because the optimal length for binding to it is 8-9 amino acids. We newly designed a conjugate consisting of CpG30 and the C-TRP2_181-188 peptide (9-mer), in which the N-terminal serine residue of TRP2_180-188 is replaced by a cysteine. By adjusting the peptide length, we succeeded in inducing strong TRP2_180-188 peptide-specific CTL activity upon immunization with the CpG30-C-TRP2_181-188 conjugate. Furthermore, various CpG30-C-TRP2_181-188 conjugates having other CpG-DNA sequences or cysteine analogues also induced the same level of CTL activity. Therefore, CpG-C-peptide conjugates prepared by replacement of the amino acid residue at the N-terminus with a cysteine residue could be a new and effective platform for peptide vaccines for targeting specific antigens of cancers and infectious diseases.

Advances in the mechanisms and applications of inhibitory oligodeoxynucleotides against immune-mediated inflammatory diseases

Inhibitory oligodeoxynucleotides (ODNs) are short single-stranded DNA, which capable of folding into complex structures, enabling them to bind to a large variety of targets. With appropriate modifications, the inhibitory oligodeoxynucleotides exhibited many features of long half-life time, simple production, low toxicity and immunogenicity. In recent years, inhibitory oligodeoxynucleotides have received considerable attention for their potential therapeutic applications in immune-mediated inflammatory diseases (IMIDs). Inhibitory oligodeoxynucleotides could be divided into three categories according to its mechanisms and targets, including antisense ODNs (AS-ODNs), DNA aptamers and immunosuppressive ODNs (iSup ODNs). As a synthetic tool with immunomodulatory activity, it can target RNAs or proteins in a specific way, resulting in the reduction, increase or recovery of protein expression, and then regulate the state of immune activation. More importantly, inhibitory oligodeoxynucleotides have been used to treat immune-mediated inflammatory diseases, including inflammatory disorders and autoimmune diseases. Several inhibitory oligodeoxynucleotide drugs have been developed and approved on the market already. These drugs vary in their chemical structures, action mechanisms and cellular targets, but all of them could be capable of inhibiting excessive inflammatory responses. This review summarized their chemical modifications, action mechanisms and applications of the three kinds of inhibitory oligodeoxynucleotidesin the precise treatment of immune-mediated inflammatory diseases.

DNA Oligonucleotides as Antivirals and Vaccine Constituents against SARS Coronaviruses: A Prospective Tool for Immune System Tuning

The SARS-CoV-2 pandemic has demonstrated the need to create highly effective antivirals and vaccines against various RNA viruses, including SARS coronaviruses. This paper provides a short review of innovative strategies in the development of antivirals and vaccines against SARS coronaviruses, with a focus on antisense antivirals, oligonucleotide adjuvants in vaccines, and oligonucleotide vaccines. Well-developed viral genomic databases create new opportunities for the development of innovative vaccines and antivirals using a post-genomic platform. The most effective vaccines against SARS coronaviruses are those able to form highly effective memory cells for both humoral and cellular immunity. The most effective antivirals need to efficiently stop viral replication without side effects. Oligonucleotide antivirals and vaccines can resist the rapidly changing genomic sequences of SARS coronaviruses using conserved regions of their genomes to generate a long-term immune response. Oligonucleotides have been used as excellent adjuvants for decades, and increasing data show that oligonucleotides could serve as antisense antivirals and antigens in vaccine formulations, becoming a prospective tool for immune system tuning.

Comparative study of the impact of dietary supplementation with different types of CpG oligodeoxynucleotides (CpG ODNs) on enhancing intestinal microbiota diversity, antioxidant capacity, and immune-related gene expression profiles in Pacific white shrimp (Litopenaeus vannamei)

The CpG oligodeoxynucleotides (CpG ODNs) reportedly possess the capacity to strengthen immunity in mammals. This experiment was conducted to evaluate the impact of dietary supplementation with 17 types of CpG ODNs on intestinal microbiota diversity, antioxidant capacity, and immune-related gene expression profiles of the shrimp Litopenaeus vannamei. Diets including 50 mg kg^-1 CpG ODNs wrapped in egg whites were prepared and divided into 17 different groups, with 2 control groups (normal feed and feed with egg whites). These CpG ODNs supplemented diets and the control diets were fed to L. vannamei (5.15 ± 0.54 g) three times daily at 5%-8% shrimp body weight for three weeks. The results of consecutive detection of intestinal microbiota by 16S rDNA sequencing indicated that 11 of the 17 types of CpG ODNs significantly enhanced intestinal microbiota diversity, increased the populations of several probiotic bacteria, and activated possible mechanisms relevant to diseases. The immune-related genes expression and antioxidant capacity in hepatopancreas further demonstrated that the 11 types of CpG ODNs effectively improved the innate immunity of shrimp. Additionally, histology results showed that the CpG ODNs in the experiment did not damage the tissue structure of hepatopancreas. The results suggest that CpG ODNs could be used as a trace supplement to improve the intestinal health and immunity of shrimp.

Albumin-hitchhiking: Fostering the pharmacokinetics and anticancer therapeutics

Nanotherapeutics demonstrate poor accumulation in the tumor microenvironment due to poor extravasation and penetration into the tumor. Therapeutics such as oligonucleotides, peptides and other biologicals suffer from low systemic half-life and rapid degradation. Albumin-hitchhiking has emerged as an effective strategy to enhance tumor-specific accumulation of various therapeutics. Hitchhiking on serum albumin (SA) have shown to improve biological half-life of various therapeutics including nanocarriers (NCs), biologics, oligonucleotides, vaccines, etc. In addition, passive and active accumulation of SA-riding therapeutics in the tumor, site-specific drug release, and SA-mediated endosomal escape have improved the potential of various anticancer modalities such as chemo-, immune-, vaccine, and gene therapies. In this review, we have discussed the advantages of employing SA-hitchhiking in anticancer therapies. In addition, vaccine strategies employing inherent lymph-nodes accumulating property of albumin have been discussed. We have presented a clinical overview of SA-hitchhiked formulations along with possible bottlenecks for improved clinical outcomes. We have also discussed the role of physiologically based pharmacokinetics (PBPK) modelling for efficient characterization of anti-cancer nanotherapeutics.

LACpG10-HL Functions Effectively in Antibiotic-Free and Healthy Husbandry by Improving the Innate Immunity

Antibiotics are broadly restricted in modern husbandry farming, necessitating the need for efficient and low-cost immunomodulatory preparations in antibiotic-free and healthful farming. As is known to all, CpG oligonucleotides (CpG-ODNs, an effective innate immunostimulatory agent) recognized by TLR9 in mammals (while TLR21 in avians) could collaborate with some united agent to induce stronger immune responses, but the cost is prohibitively expensive for farmers. Here, considering the coordination between TLR2 and TLR9/TLR21, we firstly proposed the idea that the well-fermented Lactococcus lactis could be utilized as a CpG-plasmid carrier (LACpG10) to enhance the host’s innate immunity against pathogenic invasion. In the present study, after obtaining LACpG10-HL from homogenized and lyophilized recombinant strain LACpG10, we treated primary chicken lymphocytes, two cell lines (HD11 and IPEC-J2), and chickens with LACpG10-HL, CpG plasmids (pNZ8148-CpG10), and other stimulants, and respectively confirmed the effects by conducting qRT-PCR, bacterial infection assays, and a zoological experiment. Our data showed that LACpG10-HL could induce excellent innate immunity by regulating autophagy reactions, cytokine expression, and motivating PRRs. Interestingly, despite having no direct antiseptic effect, LACpG10-HL improved the antibacterial capacities of lymphocytes and enterocytes at the first line of defense. Most importantly, water-supplied LACpG10-HL treatment reduced the average adverse event rates, demonstrating that LACpG10-HL maintained its excellent immunostimulatory and protective properties under farming conditions. Our research not only contributes to revealing the satisfactory effects of LACpG10-HL but also sheds new light on a cost-effective solution with optimal immune effects in green, antibiotic-free, and healthful husbandry farming.

Development and immunogenicity evaluation of porcine deltacoronavirus inactivated vaccine with different adjuvants in mice

Porcine deltacoronavirus (PDCoV) is a novel coronavirus that causes diarrhea in pigs of various ages, especially in suckling piglets, and there are no effective measures to prevent and control PDCoV currently. In this study, two adjuvants Al(OH)₃ and ODN2395 working through different mechanisms were used to prepare inactivated PDCoV vaccines, and the immune effects of PDCoV inactivated vaccines were assessed in mice. From the results, we found that both PDCoV/Al(OH)₃ vaccine and PDCoV/2395 vaccine could induce IgG and neutralizing antibodies with high levels in mice. At the same time, cytokines of IFN-γ, IL-4 and chemokine ligand of CXCL13 in serum were significantly increased after immunization, and reached the highest levels in PDCoV/2395 vaccine group, which suggested that PDCoV/2395 could promote the production of both Th1 and Th2 polarized cytokines. In addition, histopathological observations showed that vaccination helped mice resist PDCoV infection. These results indicated that both the two inactivated vaccines have good immune effects. Moreover, the PDCoV/2395 vaccine worked better than the PDCoV/Al(OH)₃ vaccine for PDCoV/2395 having the good ability to induce both humoral and cellular immunogenicity. The PDCoV/2395 inactivated vaccine developed in this study might be an effective tool for the prevention of PDCoV infection.

A new cell death program regulated by toll-like receptor 9 through p38 mitogen-activated protein kinase signaling pathway in a neonatal rat model with sepsis associated encephalopathy

Background:

Sepsis, a serious condition with high mortality, usually causes sepsis associated encephalopathy (SAE) that involves neuronal cell death. However, the cell death programs involved and their underlying mechanisms are not clear. This study aimed to explore the regulatory mechanisms of different cell death programs in SAE.

Methods:

A neonatal rat model of SAE was established by cecal ligation and perforation. Survival rate and vital signs (mean arterial pressure and heart rate) were monitored, nerve reflexes were evaluated, and cortical pathological changes were observed by hematoxylin and eosin staining. The expression of pyroptosis, apoptosis, and necroptosis (PANoptosis)-related proteins, mitogen- activated protein kinase (MAPK), and its upstream regulator toll-like receptor 9 (TLR9) were detected. The expression of TLR9 in neurons was observed by immunofluorescence staining. The ultrastructure of neurons was observed by transmission electron microscope.

Results:

First, PANoptosis was found in cortical nerve cells of the SAE rats. Meanwhile, the subunits of MAPKs, p38 MAPK, Jun N- terminal kinase, and extracellular signal-regulated kinase (ERK) were activated. After pharmacologically inhibiting each of the subunits, only p38 MAPK was found to be associated with PANoptosis. Furthermore, blocking the p38 MAPK signaling pathway activated necroptosis but inhibited apoptosis and pyroptosis. When necroptosis was pharmacologically inhibited, apoptosis and pyroptosis were reactivated. Finally, we found that the expression of TLR9, a regulator of MAPKs, was significantly increased in this model. After down-regulation of TLR9, p38 MAPK, and ERK signaling pathways were inhibited, which led to the inhibition of PANoptosis. Further analysis found that down-regulation of TLR9 improved the survival rate and reduced the pathological changes in SAE rats.

Conclusions:

Our study showed that the programs comprising PANoptosis are activated simultaneously in SAE rats. TLR9 activated PANoptosis through the p38 MAPK signaling pathway. TLR9 may work as a potential target for SAE treatment.

YBX has functional roles in CpG-ODN against cold stress and bacterial infection of Misgurnus anguillicaudatus

Misgurnus anguillicaudatus (M. anguillicaudatus) is a widely cultivated fish. However, in M. anguillicaudatus breeding, the frequent cold stress during daily breeding could induce immune suppression and increase the risk of infection, causing serious economic loss. Based on existing findings, CpG Oligonucleotides (CpG-ODNs) may be an ideal protective agent for low temperature fish breeding, performing anti-infective when faced with cold stress with cold shock proteins Y box binding proteins (YBX). Although YBX has pleiotropic functions, its roles in CpG-ODNs-mediated immunity (especially under cold situations) remain largely unexplored. To clarify the relationship among them, we identified the YBX1/YBX2 in M. anguillicaudatus and analyzed using a series of bioinformatics methods. After that, we immunized the fish with 3 types of CpG-ODNs and challenged with Aeromonas hydrophila (A. hydrophila). Here we showed that the best anti-bacterial effect of CpG-B was accompanied by the significant upregulation of YBX1. And the detection of the YBX1 downstream effectors confirmed that CpG-B induced the YBX1-mediated Th1 oriented responses to A. hydrophila by regulation of the NLRP3 (Caspase-A/-B), IL-1β, IL-12 and IFN-γ. Afterwards, we found that under cold stress, CpG-B can activate the NLRP3 and NF-κB pathways through YBX1, a key mediator of anti-A. hydrophila in CpG-B immunization. In this study, we demonstrated CpG-B protection against infection in low temperature, and its interaction with YBX1, expanded the research of CpG-ODN under cold stress, and provided a new CpG-ODN application for low temperature fish farming.

Polysaccharide-based nanomedicines for cancer immunotherapy: A review

Cancer immunotherapy is an effective antitumor approach through activating immune systems to eradicate tumors by immunotherapeutics. However, direct administration of "naked" immunotherapeutic agents (such as nucleic acids, cytokines, adjuvants or antigens without delivery vehicles) often results in: (1) an unsatisfactory efficacy due to suboptimal pharmacokinetics; (2) strong toxic and side effects due to low targeting (or off-target) efficiency. To overcome these shortcomings, a series of polysaccharide-based nanoparticles have been developed to carry immunotherapeutics to enhance antitumor immune responses with reduced toxicity and side effects. Polysaccharides are a family of natural polymers that hold unique physicochemical and biological properties, as they could interact with immune system to stimulate an enhanced immune response. Their structures offer versatility in synthesizing multifunctional nanocomposites, which could be chemically modified to achieve high stability and bioavailability for delivering therapeutics into tumor tissues. This review aims to highlight recent advances in polysaccharide-based nanomedicines for cancer immunotherapy and propose new perspectives on the use of polysaccharide-based immunotherapeutics.

An Engineered Prussian Blue Nanoparticles-based Nanoimmunotherapy Elicits Robust and Persistent Immunological Memory in a TH-MYCN Neuroblastoma Model

A combination therapy using Prussian blue nanoparticles (PBNP) as photothermal therapy (PTT) agents coated with CpG oligodeoxynucleotides, an immunologic adjuvant, as a nanoimmunotherapy (CpG-PBNP-PTT) for neuroblastoma (NB) is described. NB driven by MYCN amplification confers high risk and correlates with a dismal prognosis, accounting for the majority of NB-related mortality. The efficacy of the CpG-PBNP-PTT nanoimmunotherapy in a clinically relevant, TH-MYCN murine NB model (9464D) overexpressing MYCN is tested. When administered to 9464D NB cells in vitro, CpG-PBNP-PTT triggers thermal dose-dependent immunogenic cell death and tumor cell priming for immune recognition in vitro, measured by the expression of specific costimulatory and antigen-presenting molecules. In vivo, intratumorally administered CpG-PBNP-PTT generates complete tumor regression and significantly higher long-term survival compared to controls. Furthermore, CpG-PBNP-PTT-treated mice reject tumor rechallenge. Ex vivo studies confirm these therapeutic responses result from the generation of robust T cell-mediated immunological memory. Consequently, in a synchronous 9464D tumor model, CpG-PBNP-PTT induces complete tumor regression on the treated flank and significantly slows tumor progression on the untreated flank, improving animal survival. These findings demonstrate that localized administration of the CpG-PBNP-PTT nanoimmunotherapy drives potent systemic T cell responses in solid tumors such as NB and therefore has therapeutic implications for NB.

Overcoming the challenges of tissue delivery for oligonucleotide therapeutics

Synthetic therapeutic oligonucleotides (STO) represent the third bonafide platform for drug discovery in the pharmaceutical industry after small molecule and protein therapeutics. So far, thirteen STOs have been approved by regulatory agencies and over one hundred of them are in different stages of clinical trials. STOs hybridize to their target RNA or DNA in cells via Watson-Crick base pairing to exert their pharmacological effects. This unique class of therapeutic agents has the potential to target genes and gene products that are considered undruggable by other therapeutic platforms. However, STOs must overcome several extracellular and intracellular obstacles to interact with their biological RNA targets inside cells. These obstacles include degradation by extracellular nucleases, scavenging by the reticuloendothelial system, filtration by the kidney, traversing the capillary endothelium to access the tissue interstitium, cell-surface receptor-mediated endocytic uptake, and escape from endolysosomal compartments to access the nuclear and/or cytoplasmic compartments where their targets reside. In this review, we present the recent advances in this field with a specific focus on antisense oligonucleotides (ASOs) and siRNA therapeutics.

Immune Modulator and Low-Temperature PTT-Induced Synergistic Immunotherapy for Cancer Treatment

Immunotherapy has shown great potential in cancer therapeutics but has limitations of the insufficient activation of dendritic cells (DCs) and immune-suppressive microenvironment. To overcome these obstacles, a cascade synergistic immunotherapy nanosystem (denoted as CpG@PDA-FA) was designed to elevate anticancer immune response. The combination nanosystem including a photothermal agent polydopamine (PDA) and immunomodulator CpG oligodeoxynucleotides (CpG ODNs). On the one hand, polydopamine (PDA) acts as a photothermal agent to induce low-temperature PTT. It leads to immunogenic cell death (ICD), a programmed cell death pathway, which can activate DCs and enhance the antitumor immune response of T cells. On the other hand, CpG ODNs further promote maturation and migration of DCs as well as ameliorates the immunosuppression microenvironment of the tumor (TME). This paper focuses on a cancer synergistic treatment of ICD-induced immunotherapy by low-temperature PTT and ameliorates TME by immunomodulator CpG ODNs. We proved that CpG@PDA-FA NPs realized a remarkable synergistic treatment effect compared with respective single PTT or CpG therapy in the maturation of DCs and activation of T cells. In addition, CpG@PDA-FA NPs also reduced myeloid-derived suppressor cells and regulatory T cells to relieve immunosuppression. Hence, CpG@PDA-FA NPs provide a bidirectional immunotherapy strategy for tumor inhibition and highlight the cascade effects of low-temperature PTT and immunotherapy.

Multifunctional DNA dendrimer nanostructures for biomedical applications

DNA nanomaterials have attracted ever-increasing attention over the past decades due to their incomparable programmability and multifunctionality. In particular, DNA dendrimer nanostructures, as a major research focus, have been applied in the fields of biosensing, therapeutics, and protein engineering, benefiting from their highly branched configuration. With the aid of specific recognition probes and inherent signal amplification, DNA dendrimers can achieve ultrasensitive detection of nucleic acids, proteins, cells, and other substances, such as lipopolysaccharides (LPS), adenosine triphosphate (ATP), and exosomes. By virtue of their void-containing structures and biocompatibility, DNA dendrimers can deliver drugs or functional nucleic acids into target cells in chemotherapy, immunotherapy, and gene therapy. Furthermore, DNA dendrimers are being applied in protein engineering for efficient directed evolution of proteins. This review summarizes the main research progress of DNA dendrimers, concerning their assembly methods and biomedical applications as well as the emerging challenges and perspectives for future research.

The Role of Virus-Like Particles in Medical Biotechnology

Virus-like particles (VLPs) are protein-based, nanoscale, self-assembling, cage architectures, which have relevant applications in biomedicine. They can be used for the development of vaccines, imaging approaches, drug and gene therapy delivery systems, and in vitro diagnostic methods. Today, three relevant viruses are targeted using VLP-based recombinant vaccines. VLP-based drug delivery, nanoreactors for therapy, and imaging systems are approaches under development with promising outcomes. Several VLP-based vaccines are under clinical evaluation. Herein, an updated view on the VLP-based biomedical applications is provided; advanced methods for the production, functionalization, and drug loading of VLPs are described, and perspectives for the field are identified.

Toll-Like Receptor 21 of Chicken and Duck Recognize a Broad Array of Immunostimulatory CpG-oligodeoxynucleotide Sequences

CpG-oligodeoxynucleotides (CpG-ODNs) mimicking the function of microbial CpG-dideoxynucleotides containing DNA (CpG-DNA) are potent immune stimuli. The immunostimulatory activity and the species-specific activities of a CpG-ODN depend on its nucleotide sequence properties, including CpG-hexamer motif types, spacing between motifs, nucleotide sequence, and length. Toll-like receptor (TLR) 9 is the cellular receptor for CpG-ODNs in mammalian species, while TLR21 is the receptor in avian species. Mammalian cells lack TLR21, and avian cells lack TLR9; however, both TLRs are expressed in fish cells. While nucleotide sequence properties required for a CpG-ODN to strongly activate mammalian TLR9 and its species-specific activities to different mammalian TLR9s are better studied, CpG-ODN activation of TLR21 is not yet well investigated. Here we characterized chicken and duck TLR21s and investigated their activation by CpG-ODNs. Chicken and duck TLR21s contain 972 and 976 amino acid residues, respectively, and differ from TLR9s as they do not have an undefined region in their ectodomain. Cell-based TLR21 activation assays were established to investigate TLR21 activation by different CpG-ODNs. Unlike grouper TLR21, which was preferentially activated by CpG-ODN with a GTCGTT hexamer motif, chicken and duck TLR21s do not distinguish among different CpG-hexamer motifs. Additionally, these two poultry TLR21s were activated by CpG-ODNs with lengths ranging from 15 to 31 nucleotides and with different spacing between CpG-hexamer motifs. These suggested that compared to mammalian TLR9 and grouper TLR21, chicken and duck TLR21s have a broad CpG-ODN sequence recognition profile. Thus, they could also recognize a wide array of DNA-associated molecular patterns from microbes. Moreover, CpG-ODNs are being investigated as antimicrobial agents and as vaccine adjuvants for different species. This study revealed that there are more optimized CpG-ODNs that can be used in poultry farming as anti-infection agents compared to CpG-ODN choices available for other species.

Immune sensing of DNA and strategies for fish DNA vaccine development

Studies of DNA vaccines have shown that understanding the mechanism of DNA vaccine-mediated action is the key for vaccine development. Current knowledge has shown the presence of antigen presenting cells (APCs) involving in B and T cells at the muscle injection site and the upregulation of type I interferon (IFN-I) that initiates antiviral response and benefits adaptive immunity in fish DNA vaccines. IFN-I may be triggered by expressed antigen such as the rhabdovirus G protein encoded DNA vaccine or by plasmid DNA itself through cytosolic DNA sensing. The investigating of Toll-like receptor 9, and 21 are the CpG-motif sensors in many fish species, and the cytosolic DNA receptors DDX41 and downstream STING signaling revealed the mechanisms for IFN-I production. This review article describes the recent finding of receptors for cytosolic DNA, the STING-TBK1-IRF signaling, and the possibility of turning these findings into strategies for the future development of DNA vaccines.

Immunomodulation as a Novel Strategy for Prevention and Treatment of Bordetella spp. Infections

Well-adapted pathogens have evolved to survive the many challenges of a robust immune response. Defending against all host antimicrobials simultaneously would be exceedingly difficult, if not impossible, so many co-evolved organisms utilize immunomodulatory tools to subvert, distract, and/or evade the host immune response. Bordetella spp. present many examples of the diversity of immunomodulators and an exceptional experimental system in which to study them. Recent advances in this experimental system suggest strategies for interventions that tweak immunity to disrupt bacterial immunomodulation, engaging more effective host immunity to better prevent and treat infections. Here we review advances in the understanding of respiratory pathogens, with special focus on Bordetella spp., and prospects for the use of immune-stimulatory interventions in the prevention and treatment of infection.