Dendritic Cell Targeting Effectively Boosts T Cell Responses Elicited by an HIV Multiepitope DNA Vaccine

Recombinant antigen delivery to dendritic cells as a way to improve vaccine design

Dendritic cells are central to the development of immunity, as they are specialized in initiating antigen-specific immune responses. In this review, we briefly present the existing knowledge on dendritic cell biology and how their division in different dendritic cell subsets may impact the development of immune responses. In addition, we explore the use of chimeric monoclonal antibodies that bind to dendritic cell surface receptors, with an emphasis on the C-type lectin family of endocytic receptors, to deliver antigens directly to these cells. Promising preclinical studies have shown that it is possible to modulate the development of immune responses to different pathogens when monoclonal antibodies fused to pathogen-derived antigens are used to deliver the antigen to different subsets of dendritic cells. This approach can be used to improve the efficacy of vaccines against different pathogens.

Targeted delivery of autoantigen to dendritic cells prevents development of spontaneous uveitis

Restoration of immunological tolerance to self antigens has been a major drive in understanding the mechanisms of, and developing new treatments for, autoimmune and autoinflammatory disease. Sessile dendritic cells (DC) are considered the main instruments underpinning immunological tolerance particularly the CD205+ (DEC205+) cDC1 subset in contrast to DCIR2+ cDC2 which mediate immunogenicity. Targeting DC using autoantigen peptide-antibody fusion proteins has been a well explored methodology for inducing tolerance. Here we show that subcutaneous (s.c.) inoculation of hen-egg lysozyme (HEL)-DEC205 Ig fusion prevents the development of spontaneous uveoretinitis (experimental autoimmune uveoretinitis, EAU) in a transgenic mouse model generated by crossing interphotoreceptor retinol binding protein (IRBP)-HEL (sTg HEL) with HEL specific TCR (sTg TCR) mice. Prolonged suppression of EAU required injections of HEL-DEC205 Ig once weekly, reflecting the half life of s.c. DC. Interestingly, HEL-DCIR2 Ig also had a suppressive effect on development of EAU but less so than DEC205 Ig while it had minimal effect on preventing the retinal atrophy associated with EAU. In addition, HEL-DEC205 Ig was only effective when administered s.c. rather than systemically and had no effect on EAU induced by adoptive transfer of HEL-activated T cells. These data demonstrate the importance of systemic (lymph node) rather than local (eye) antigen presentation in the development of EAU as well as suggest a potential therapeutic approach to controlling sight-threatening immune-mediated uveitis provided relevant antigen(s) can be identified.

Dendritic Cells - Winning the Fight against HIV

HIV is a virus that targets and hijacks the immune cells of the host. It multiplies by attacking the helper T-lymphocytes. HIV has remained one of the most difficult and dangerous infections in the world due to the inability to find a successful treatment and a lack of access to medical care. When the virus reaches the body, dendritic cells are the first cells it encounters. DCs have been identified as one of the most effective mediators of immune responses, implying a promising strategy against viral infection. The current state of knowledge about the function of dendritic cells and their subsets is critical for using their full potential as a candidate for the development of an HIV vaccine. Despite extensive efforts, a reliable vaccine with the fewest side effects has yet to be found, and further research is needed to find a dependable and efficient vaccine. The extent to which dendritic cell-based therapy is used to treat HIV was investigated in this study. As the virus attacks the host immune system, the dendritic cells can trigger an immune response against HIV-1 infection.

Delivery of antigen to porcine dendritic cells by fusing antigen with porcine dendritic cells targeting peptide

Dendritic cells (DCs) are professional antigen-presenting cells that can recognize, capture, and process antigens. Fusing molecules targeting DCs with antigens can effectively improve the efficiency with which antigens are recognized and captured by DCs. This targeting strategy can be used for vaccine development to effectively improve the efficiency of antigen recognition and capture by DCs. The targeting sequence of porcine cytotoxic T-lymphocyte associated protein 4 (CTLA4), which binds porcine DCs, was identified in this study. Recombinant Lactobacillus reuteri (L. reuteri) expressing CTLA4-6aa (LYPPPY) and CTLA4-87aa fused to the porcine epidemic diarrhea virus (PEDV) protective antigen core neutralizing epitope (COE) were used to evaluate the ability of the two targeting motifs to bind the B7 molecule on DCs. Our results demonstrate that CTLA4-6aa could bind porcine DCs, and recombinant Lactobacillus expressing the CTLA4-6aa captured by porcine DCs was more efficient than those expressing CTLA4-87aa. In addition, the expression of DC markers, toll-like receptors, and cytokines was significantly higher in the 6aa-COE/L. reuteri-stimulated porcine DCs compared to DCs treated with 87aa-COE/L. reuteri (p<0.01) and recombinant Lactobacillus expressing CTLA4-6aa enhanced the ability of porcine DCs to activate T-cell proliferation. Our analysis of the protein structure revealed that CTLA4-87aa contains intramolecular hydrogen bonds, which may have weakened the intermolecular force between the residues on porcine CTLA4 and that on B7. In conclusion, recombinant Lactobacillus expressing CTLA4-6aa were more efficiently captured by porcine DCs and had a stronger ability to promote DC maturation and enhance T-cell proliferation. The LYPPPY motif is the optimal sequence for binding to porcine DCs. Piglets immunized with recombinant Lactobacillus showed that recombinant Lactobacillus expressing CTLA4-6aa induced significant levels of anti-PEDV-specific IgG and IgA antibody responses. Our study may promote research on DC-targeting strategies to enhance the effectiveness of porcine vaccines.

In Silico and in Vivo Analysis of HIV-1 Rev Regulatory Protein for Evaluation of a Multiepitope-based Vaccine Candidate

In silico-designed multiepitope conserved regions of human immunodeficiency virus 1 (HIV-1) proteins would be a beneficial strategy for antigen design which induces effective anti-HIV-1 T-cell responses. The conserved multiple HLA-DR-binding epitopes of Rev protein were identified using IEDB MHC-I prediction tools and SYFPEITHI webserver to screen potential T-cell epitopes. We analyzed toxicity, allergenicity, immunogenicity, hemolytic activity, cross-reactivity, cell-penetrating peptide (CPP) potency, and molecular docking of the candidate epitopes using several immune-informatics tools. Afterward, we designed a novel multiepitope construct based on non-toxic and non-allergenic Rev, Nef, Gp160 and P24-derived cytotoxic T cell (CTL) and T-helper cell (HTL) epitopes. Next, the designed construct (Nef-Rev-Gp160-P24) was subjected to three B-cell epitope prediction webservers, ProtParam and Protein-Sol to obtain the physicochemical features. Then, the recombinant multiepitope DNA and polypeptide constructs were complexed with different CPPs for nanoparticle formation and pass them via the cell membranes. Finally, the immunogenicity of multiepitope constructs in a variety of modalities was evaluated in mice. The results demonstrated that groups immunized with heterologous DNA+ MPG or HR9 CPP prime/rNef-Rev-Gp160-P24 polypeptide + LDP-NLS CPP boost regimens could significantly produce higher levels of IFN-γ and Granzyme B, and lower amounts of IL-10 than other groups. Moreover, higher levels of IgG2a and IgG2b were observed in all heterologous prime-boost regimens than homologous DNA or polypeptide regimens. Altogether, the present findings indicated that the Nef-Rev-Gp160-P24 polypeptide meets the criteria to be potentially useful as a multiepitope-based vaccine candidate against HIV-1 infection.

Conventional type 1 dendritic cells induce TH 1, TH 1-like follicular helper T cells and regulatory T cells after antigen boost via DEC205 receptor

Conventional dendritic cells (cDCs) are specialized in antigen presentation. In the mouse spleen, cDCs are classified in cDC1s and cDC2s, and express DEC205 and DCIR2 endocytic receptors, respectively. Monoclonal antibodies (mAbs) αDEC205 (αDEC) and αDCIR2 have been fused to different antigens to deliver them to cDC1s or cDC2s. We immunized mice with αDEC and αDCIR2 fused to an antigen using Poly(I:C) as adjuvant. The initial immune response was analyzed from days 3 to 6 after the immunization. We also studied the influence of a booster dose. Our results showed that antigen targeting to cDC1s promoted a pro-inflammatory T_H 1 cell response. Antigen targeting to cDC2s induced T_FH cells, GCs, and plasma cell differentiation. After boost, antigen targeting to cDC1s improved the T_H 1 cell response and induced T_H 1-like T_FH cells that led to an increase in specific antibody titers and IgG class switch. Additionally, a population of regulatory T cells was also observed. Antigen targeting to cDC2s did not improve the specific antibody response after boost. Our results add new information on the immune response induced after the administration of a booster dose with αDEC and αDCIR2 fusion mAbs. These results may be useful for vaccine design using recombinant mAbs.

Homologous prime-boost with Zika virus envelope protein and poly (I:C) induces robust specific humoral and cellular immune responses

The recent outbreaks of Zika virus (ZIKV) infection and the potential association with Guillain-Barré syndrome in adults and with congenital abnormalities have highlighted the urgency for an effective vaccine. The ZIKV Envelope glycoprotein (E_ZIKV) is the most abundant protein on the virus surface, and has been evaluated together with the pre-membrane protein (prM) of the viral coat as a vaccine candidate in clinical trials. In this study, we performed a head-to-head comparison of the immune response induced by different E_ZIKV-based vaccine candidates in mice. We compared different platforms (DNA, recombinant protein), adjuvants (poly (I:C), CpG ODN 1826) and immunization strategies (homologous, heterologous). The hierarchy of adjuvant potency showed that poly (I:C) was a superior adjuvant than CpG ODN. While poly (I:C) assisted immunization reached a plateau in antibody titers after two doses, the CpG ODN group required an extra immunization dose. Besides, the administration of poly (I:C) induced higher E_ZIKV-specific cellular immune responses than CpG ODN. We also show that immunization with homologous prime-boost E_ZIKV protein + poly (I:C) regimen induced a more robust humoral response than homologous DNA (pVAX-E_ZIKV) or heterologous regimens (DNA/protein or protein/DNA). A detailed analysis of cellular immune responses revealed that homologous (E_ZIKV + poly (I:C)) and heterologous (pVAX-E_ZIKV/E_ZIKV + poly (I:C)) prime-boost regimens induced the highest magnitude of IFN-γ secreting cells and cytokine-producing CD4⁺ T cells. Overall, our data demonstrate that homologous E_ZIKV + poly (I:C) prime-boost immunization is sufficient to induce more robust specific-E_ZIKV humoral and cellular immune responses than the other strategies that contemplate homologous DNA (pVAX-E_ZIKV) or heterologous (pVAX-E_ZIKV/E_ZIKV + poly (I:C), and vice-versa) immunizations.

Recent advances on HIV DNA vaccines development: Stepwise improvements to clinical trials

According to WHO (World Health Organization) reports, more than 770,000 people died from HIV and almost 1.7 million people becoming newly infected in the worldwide in 2018. Therefore, many attempts should be done to produce a forceful vaccine to control the AIDS. DNA-based vaccines have been investigated for HIV vaccination by researches during the recent 20 years. The DNA vaccines are novel approach for induction of both type of immune responses (cellular and humoral) in the host cells and have many advantages including high stability, fast and easy of fabrication and absence of severe side effects when compared with other vaccination methods. Recent studies have been focused on vaccine design, immune responses and on the use of adjuvants as a promising strategy for increased level of responses, delivery approaches by viral and non-viral methods and vector design for different antigens of HIV virus. In this review, we outlined the aforementioned advances on HIV DNA vaccines. Then we described the future trends in clinical trials as a strong strategy even in healthy volunteers and the potential developments in control and prevention of HIV.

Dendritic Cells/Macrophages-Targeting Feature of Ebola Glycoprotein and its Potential as Immunological Facilitator for Antiviral Vaccine Approach

In the prevention of epidemic and pandemic viral infection, the use of the antiviral vaccine has been the most successful biotechnological and biomedical approach. In recent times, vaccine development studies have focused on recruiting and targeting immunogens to dendritic cells (DCs) and macrophages to induce innate and adaptive immune responses. Interestingly, Ebola virus (EBOV) glycoprotein (GP) has a strong binding affinity with DCs and macrophages. Shreds of evidence have also shown that the interaction between EBOV GP with DCs and macrophages leads to massive recruitment of DCs and macrophages capable of regulating innate and adaptive immune responses. Therefore, studies for the development of vaccine can utilize the affinity between EBOV GP and DCs/macrophages as a novel immunological approach to induce both innate and acquired immune responses. In this review, we will discuss the unique features of EBOV GP to target the DC, and its potential to elicit strong immune responses while targeting DCs/macrophages. This review hopes to suggest and stimulate thoughts of developing a stronger and effective DC-targeting vaccine for diverse virus infection using EBOV GP.

Development of Functional Antibodies Directed to Human Dialyzable Leukocyte Extract (Transferon®)

Transferon® is an immunomodulator made of a complex mixture of peptides from human dialyzable leucocyte extracts (hDLEs). Development of surrogate antibodies directed to hDLE is an indispensable tool for studies during process control and preclinical trials. These antibodies are fundamental for different analytical approaches, such as identity test and drug quantitation, as well as to characterize its pharmacokinetic and mechanisms of action. A previous murine study showed the inability of the peptides of Transferon® to induce antibody production by themselves; therefore, in this work, two approaches were tested to increase its immunogenicity: chemical conjugation of the peptides of Transferon® to carrier proteins and the use of a rabbit model. Bioconjugates were generated with Keyhole Limpet Hemocyanin (KLH) or Bovine Serum Albumin (BSA) through maleimide-activated carrier proteins. BALB/c mice and New Zealand rabbits were immunized with Transferon® conjugated to KLH or nonconjugated Transferon®. Animals that were immunized with conjugated Transferon® showed significant production of antibodies as evinced by the recognition of Transferon®-BSA conjugate in ELISA assays. Moreover, rabbits showed higher antibody titers when compared with mice. Neither mouse nor rabbits developed antibodies when immunized with nonconjugated Transferon®. Interestingly, rabbit antibodies were able to partially block IL-2 production in Jurkat cells after costimulation with Transferon®. In conclusion, it is feasible to elicit specific and functional antibodies anti-hDLE with different potential uses during the life cycle of the product.

Poly(I:C) Potentiates T Cell Immunity to a Dendritic Cell Targeted HIV-Multiepitope Vaccine

Cellular immune responses are implicated in resistance to HIV and have been considered for the development of an effective vaccine. Despite their safety profile, subunit vaccines need to be delivered combined with an adjuvant. In the last years, in vivo antigen targeting to dendritic cells (DCs) using chimeric monoclonal antibodies (mAb) against the DC endocytic receptor DEC205/CD205 was shown to support long-term T cell immunity. Here, we evaluated the ability of different adjuvants to modulate specific cellular immune response when eight CD4⁺ HIV-derived epitopes (HIVBr8) were targeted to DEC205⁺ DCs in vivo. Immunization with two doses of αDECHIVBr8 mAb along with poly(I:C) induced Th1 cytokine production and higher frequency of HIV-specific polyfunctional and long-lived T cells than MPL or CpG ODN-assisted immunization. Although each adjuvant elicited responses against the 8 epitopes present in the vaccine, the magnitude of the T cell response was higher in the presence of poly(I:C). Moreover, poly(I:C) up regulated the expression of costimulatory molecules in both cDC1 and cDC2 DCs subsets. In summary, the use of poly(I:C) in a vaccine formulation that targets multiple epitopes to the DEC205 receptor improved the potency and the quality of HIV-specific responses when compared to other vaccine-adjuvant formulations. This study highlights the importance of the rational selection of antigen/adjuvant combination to potentiate the desired immune responses.

Dendritic Cell Targeting Using a DNA Vaccine Induces Specific Antibodies and CD4+ T Cells to the Dengue Virus Envelope Protein Domain III

Dengue fever has become a global threat, causing millions of infections every year. An effective vaccine against all four serotypes of dengue virus (DENV) has not been developed yet. Among the different vaccination strategies available today, DNA vaccines are safe and practical, but currently induce relatively weak immune responses in humans. In order to improve immunogenicity, antigens may be targeted to dendritic cells (DCs), the main antigen presenting cells and orchestrators of the adaptive immune response, inducing T and B cell activation. It was previously shown that a DNA vaccine encoding a fusion protein comprised of an antigen and a single-chain Fv antibody (scFv) specific for the DC endocytic receptor DEC205 induced strong immune responses to the targeted antigen. In this work, we evaluate this strategy to improve the immunogenicity of dengue virus (DENV) proteins. Plasmids encoding the scFv αDEC205, or an isotype control (scFv ISO), fused to the DENV2 envelope protein domain III (EDIII) were generated, and EDIII specific immune responses were evaluated in immunized mice. BALB/c mice were intramuscularly (i.m.) immunized three times with plasmid DNAs encoding either scDEC-EDIII or scISO-EDIII followed by electroporation. Analyses of the antibody responses indicated that EDIII fusion with scFv targeting the DEC205 receptor significantly enhanced serum anti-EDIII IgG titers that inhibited DENV2 infection. Similarly, mice immunized with the scDEC-EDIII plasmid developed a robust CD4⁺ T cell response to the targeted antigen, allowing the identification of two linear epitopes recognized by the BALB/c haplotype. Taken together, these results indicate that targeting DENV2 EDIII protein to DCs using a DNA vaccine encoding the scFv αDEC205 improves both antibody and CD4⁺ T cell responses. This strategy opens perspectives for the use of DNA vaccines that encode antigens targeted to DCs as a strategy to increase immunogenicity.

Current trends in tuberculosis vaccine

Despite the global efforts made to control tuberculosis (TB) and the large number of available new anti-TB drugs, TB still affects one-third of the world population. The conventional vaccine bacille Calmette-Guérin (BCG) shows varying efficacy in different populations, and there are safety issues in immunocompromised patients. Hence, there is an urgent requirement for a new and better TB vaccine candidate than BCG. There are several alternate vaccines available for TB such as DNA, subunit, adjuvant, and live-attenuated vaccines. Use of auxotrophic vaccine is an emerging technology. Newer vaccine technologies include vaccine delivery methods such as adenovirus- and cytomegalovirus (CMV)-based vector delivery, chimeric monoclonal antibody, single-chain fragment variable, RNA-lipoplexes, and nanoparticle-based technology. Based on its application, TB vaccines are classified as conventional, prophylactic, booster, therapeutic, and reinfection preventive vaccines. Currently, there are 12 vaccine candidates in clinical trials. In this review, we have briefly discussed about each of these vaccines in different phases of clinical trials. These vaccines should be analyzed further for developing a safe and more efficacious vaccine for TB.

Using Dendritic Cell-Based Immunotherapy to Treat HIV: How Can This Strategy be Improved?

Harnessing dendritic cells (DC) to treat HIV infection is considered a key strategy to improve anti-HIV treatment and promote the discovery of functional or sterilizing cures. Although this strategy represents a promising approach, the results of currently published trials suggest that opportunities to optimize its performance still exist. In addition to the genetic and clinical characteristics of patients, the efficacy of DC-based immunotherapy depends on the quality of the vaccine product, which is composed of precursor-derived DC and an antigen for pulsing. Here, we focus on some factors that can interfere with vaccine production and should thus be considered to improve DC-based immunotherapy for HIV infection.

A Rift Valley fever virus Gn ectodomain-based DNA vaccine induces a partial protection not improved by APC targeting

Rift Valley fever virus, a phlebovirus endemic in Africa, causes serious diseases in ruminants and humans. Due to the high probability of new outbreaks and spread to other continents where competent vectors are present, vaccine development is an urgent priority as no licensed vaccines are available outside areas of endemicity. In this study, we evaluated in sheep the protective immunity induced by DNA vaccines encoding the extracellular portion of the Gn antigen which was either or not targeted to antigen-presenting cells. The DNA encoding untargeted antigen was the most potent at inducing IgG responses, although not neutralizing, and conferred a significant clinical and virological protection upon infectious challenge, superior to DNA vaccines encoding the targeted antigen. A statistical analysis of the challenge parameters supported that the anti-eGn IgG, rather than the T-cell response, was instrumental in protection. Altogether, this work shows that a DNA vaccine encoding the extracellular portion of the Gn antigen confers substantial—although incomplete—protective immunity in sheep, a natural host with high preclinical relevance, and provides some insights into key immune correlates useful for further vaccine improvements against the Rift Valley fever virus.

A vaccine made from the genome of Rift Valley fever virus (RVFV) offers partial protection, but pieces of the puzzle are missing, say scientists. French and Spanish researchers, led by the French National Institute for Agricultural Research’s Isabelle Schwartz-Cornil, tested in sheep three slightly-differing vaccine candidates using RVFV genes. Such DNA vaccines are designed to generate proteins which a host’s immune system can use to arm itself against a genuine viral infection. Two of the candidates, designed to target cells that would present the viral proteins to the host’s immune system, provided some benefit to the vaccinated sheep. However, the third untargeted candidate, was the most efficient at protecting sheep, although not completely, and at boosting antibody levels despite not neutralizing the virus. These results provide hope for DNA vaccines against RVFV, and offer direction for future research effort.

Nanoparticle-Fusion Protein Complexes Protect against Mycobacterium tuberculosis Infection

Tuberculosis (TB) is the leading cause of death from infectious disease, and the current vaccine, Bacillus Calmette-Guerin (BCG), is inadequate. Nanoparticles (NPs) are an emerging vaccine technology, with recent successes in oncology and infectious diseases. NPs have been exploited as antigen delivery systems and also for their adjuvantic properties. However, the mechanisms underlying their immunological activity remain obscure. Here, we developed a novel mucosal TB vaccine (Nano-FP1) based upon yellow carnauba wax NPs (YC-NPs), coated with a fusion protein consisting of three Mycobacterium tuberculosis (Mtb) antigens: Acr, Ag85B, and HBHA. Mucosal immunization of BCG-primed mice with Nano-FP1 significantly enhanced protection in animals challenged with low-dose, aerosolized Mtb. Bacterial control by Nano-FP1 was associated with dramatically enhanced cellular immunity compared to BCG, including superior CD4+ and CD8+ T cell proliferation, tissue-resident memory T cell (Trm) seeding in the lungs, and cytokine polyfunctionality. Alongside these effects, we also observed potent humoral responses, such as the generation of Ag85B-specific serum IgG and respiratory IgA. Finally, we found that YC-NPs were able to activate antigen-presenting cells via an unconventional IRF-3-associated activation signature, without the production of potentially harmful inflammatory mediators, providing a mechanistic framework for vaccine efficacy and future development.

Construction and immunogenicity analysis of Lactobacillus plantarum expressing a porcine epidemic diarrhea virus S gene fused to a DC-targeting peptide

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The S protein of PDEV was displayed on the surface of a recombinant Lactobacillus plantarum NC8 strain.

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NC8-pSIP409-pgsA'-S-DCpep promoted DC activation in the LP.

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IgG and sIgA were significant increased in mice orally administered with the NC8-pSIP409-pgsA'-S-DCpep.

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The expression of specificity cytokines IFN-γ, IL-4 and IL-17A of MLNs was enhanced in mouse treated with the NC8-pSIP409-pgsA'-S-DCpep.

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NC8-pSIP409-pgsA'-S-DCpep might mediate B cell response in mouse.

Porcine epidemic diarrhea virus (PEDV) is one of the most important causative pathogens of swine diarrhea, which is widely prevalent throughout the world and is responsible for significant economic losses in the commercial pig industry, both domestic and abroad. The spike (S) protein in the PEDV capsid structure can carry the major B lymphocyte epitope, which induces production of neutralizing antibodies and provides immunoprotective effects. Moreover, the conserved region encoded by the S gene can be considered a target for establishing a new diagnostic method and is a new candidate for vaccine design. In this study, use of anchorin pgsA' allowed the fusion protein of S-DCpep to express on the surface of recombinant Lactobacillus plantarum (NC8-pSIP409-pgsA'-S-DCpep) NC8 strain. Mice were immunized by lavage administration of the recombinant NC8-pSIP409-pgsA'-S-DCpep, which was observed to induce DC activation and high production of sIgA and IgG antibodies in experimental animals, while also eliciting production of significantly more IgA⁺B220⁺ B cells. More importantly, secretion of cytokines IFN-γ, IL-4 and IL-17 in mice that were vaccinated with NC8-pSIP409-pgsA'-S-DCpep was remarkably increased. The results of our study suggest that NC8-pSIP409-pgsA'-S-DCpep potently triggers cellular and humoral immune responses. The obtained experimental results can provide a theoretical basis that lays the foundation for production of a novel oral vaccine against PED.

CpG Oligodeoxinucleotides and Flagellin Modulate the Immune Response to Antigens Targeted to CD8α+ and CD8α- Conventional Dendritic Cell Subsets

Dendritic cells (DCs) are antigen-presenting cells essential for the induction of adaptive immune responses. Their unprecedented ability to present antigens to T cells has made them excellent targets for vaccine development. In the last years, a new technology based on antigen delivery directly to different DC subsets through the use of hybrid monoclonal antibodies (mAbs) to DC surface receptors fused to antigens of interest opened new perspectives for the induction of robust immune responses. Normally, the hybrid mAbs are administered with adjuvants that induce DC maturation. In this work, we targeted an antigen to the CD8α⁺ or the CD8α⁻ DC subsets in the presence of CpG oligodeoxinucleotides (ODN) or bacterial flagellin, using hybrid αDEC205 or αDCIR2 mAbs, respectively. We also accessed the role of toll-like receptors (TLRs) 5 and 9 signaling in the induction of specific humoral and cellular immune responses. Wild-type and TLR5 or TLR9 knockout mice were immunized with two doses of the hybrid αDEC205 or αDCIR2 mAbs, as well as with an isotype control, together with CpG ODN 1826 or flagellin. A chimeric antigen containing the Plasmodium vivax 19 kDa portion of the merozoite surface protein (MSP1₁₉) linked to the Pan-allelic DR epitope was fused to each mAb. Specific CD4⁺ T cell proliferation, cytokine, and antibody production were analyzed. We found that CpG ODN 1826 or flagellin were able to induce CD4⁺ T cell proliferation, CD4⁺ T cells producing pro-inflammatory cytokines, and specific antibodies when the antigen was targeted to the CD8α⁺ DC subset. On the other hand, antigen targeting to CD8α⁻ DC subset promoted specific antibody responses and proliferation, but no detectable pro-inflammatory CD4⁺ T cell responses. Also, specific antibody responses after antigen targeting to CD8α⁺ or CD8α⁻ DCs were reduced in the absence of TLR9 or TLR5 signaling, while CD4⁺ T cell proliferation was mainly affected after antigen targeting to CD8α⁺ DCs and in the absence of TLR9 signaling. These results extend our understanding of the modulation of specific immune responses induced by antigen targeting to DCs in the presence of different adjuvants. Such knowledge may be useful for the optimization of DC-based vaccines.