Mucosal vaccines: novel strategies and applications for the control of pathogens and tumors at mucosal sites

Progress toward a vaccine for extraintestinal pathogenic E. coli (ExPEC) II: efficacy of a toxin-autotransporter dual antigen approach

Extraintestinal pathogenic Escherichia coli (ExPEC) is a leading cause of worldwide morbidity and mortality, the top cause of antimicrobial-resistant (AMR) infections, and the most frequent cause of life-threatening sepsis and urinary tract infections (UTI) in adults. The development of an effective and universal vaccine is complicated by this pathogen's pan-genome, its ability to mix and match virulence factors and AMR genes via horizontal gene transfer, an inability to decipher commensal from pathogens, and its intimate association and co-evolution with mammals. Using a pan virulome analysis of >20,000 sequenced E. coli strains, we identified the secreted cytolysin α-hemolysin (HlyA) as a high priority target for vaccine exploration studies. We demonstrate that a catalytically inactive pure form of HlyA, expressed in an autologous host using its own secretion system, is highly immunogenic in a murine host, protects against several forms of ExPEC infection (including lethal bacteremia), and significantly lowers bacterial burdens in multiple organ systems. Interestingly, the combination of a previously reported autotransporter (SinH) with HlyA was notably effective, inducing near complete protection against lethal challenge, including commonly used infection strains ST73 (CFT073) and ST95 (UTI89), as well as a mixture of 10 of the most highly virulent sequence types and strains from our clinical collection. Both HlyA and HlyA-SinH combinations also afforded some protection against UTI89 colonization in a murine UTI model. These findings suggest recombinant, inactive hemolysin and/or its combination with SinH warrant investigation in the development of an E. coli vaccine against invasive disease.

Oral mucosa immunity: ultimate strategy to stop spreading of pandemic viruses

Global pandemics are most likely initiated via zoonotic transmission to humans in which respiratory viruses infect airways with relevance to mucosal systems. Out of the known pandemics, five were initiated by respiratory viruses including current ongoing coronavirus disease 2019 (COVID-19). Striking progress in vaccine development and therapeutics has helped ameliorate the mortality and morbidity by infectious agents. Yet, organism replication and virus spread through mucosal tissues cannot be directly controlled by parenteral vaccines. A novel mitigation strategy is needed to elicit robust mucosal protection and broadly neutralizing activities to hamper virus entry mechanisms and inhibit transmission. This review focuses on the oral mucosa, which is a critical site of viral transmission and promising target to elicit sterile immunity. In addition to reviewing historic pandemics initiated by the zoonotic respiratory RNA viruses and the oral mucosal tissues, we discuss unique features of the oral immune responses. We address barriers and new prospects related to developing novel therapeutics to elicit protective immunity at the mucosal level to ultimately control transmission.

The Upper Nasal Space: Option for Systemic Drug Delivery, Mucosal Vaccines and "Nose-to-Brain"

Sino-nasal disease is appropriately treated with topical treatment, where the nasal mucosa acts as a barrier to systemic absorption. Non-invasive nasal delivery of drugs has produced some small molecule products with good bioavailability. With the recent COVID pandemic and the need for nasal mucosal immunity becoming more appreciated, more interest has become focused on the nasal cavity for vaccine delivery. In parallel, it has been recognized that drug delivery to different parts of the nose can have different results and for "nose-to-brain" delivery, deposition on the olfactory epithelium of the upper nasal space is desirable. Here the non-motile cilia and reduced mucociliary clearance lead to longer residence time that permits enhanced absorption, either into the systemic circulation or directly into the CNS. Many of the developments in nasal delivery have been to add bioadhesives and absorption/permeation enhancers, creating more complicated formulations and development pathways, but other projects have shown that the delivery device itself may allow more differential targeting of the upper nasal space without these additions and that could allow faster and more efficient programs to bring a wider range of drugs-and vaccines-to market.

Dissolving Microneedles Loaded with Nanoparticle Formulation of Respiratory Syncytial Virus Fusion Protein Virus-like Particles (F-VLPs) Elicits Cellular and Humoral Immune Responses

Respiratory syncytial virus (RSV) is one of the leading causes of bronchiolitis and pneumonia in children ages five years and below. Recent outbreaks of the virus have proven that RSV remains a severe burden on healthcare services. Thus, a vaccine for RSV is a need of the hour. Research on novel vaccine delivery systems for infectious diseases such as RSV can pave the road to more vaccine candidates. Among many novel vaccine delivery systems, a combined system with polymeric nanoparticles loaded in dissolving microneedles holds a lot of potential. In this study, the virus-like particles of the RSV fusion protein (F-VLP) were encapsulated in poly (D, L-lactide-co-glycolide) (PLGA) nanoparticles (NPs). These NPs were then loaded into dissolving microneedles (MNs) composed of hyaluronic acid and trehalose. To test the in vivo immunogenicity of the nanoparticle-loaded microneedles, Swiss Webster mice were immunized with the F-VLP NPs, both with and without adjuvant monophosphoryl lipid A (MPL) NPs loaded in the MN. The mice immunized with the F-VLP NP + MPL NP MN showed high immunoglobulin (IgG and IgG2a) levels both in the serum and lung homogenates. A subsequent analysis of lung homogenates post-RSV challenge revealed high IgA, indicating the generation of a mucosal immune response upon intradermal immunization. A flowcytometry analysis showed high CD8+ and CD4+ expression in the lymph nodes and spleens of the F-VLP NP + MPL NP MN-immunized mice. Thus, our vaccine elicited a robust humoral and cellular immune response in vivo. Therefore, PLGA nanoparticles loaded in dissolving microneedles could be a suitable novel delivery system for RSV vaccines.

Laser-assisted intradermal delivery of a microparticle vaccine for respiratory syncytial virus induces a robust immune response

Respiratory syncytial virus (RSV) is an infectious disease that poses a significant public health risk in young children. Vaccine studies conducted in the 1960s using an intramuscular injection of formalin-inactivated respiratory syncytial virus (Fi-RSV) resulted in an enhanced respiratory disease and led to the failure of the vaccine. Thus, the virus-like particles (VLP) of the RSV fusion (F) protein was used as the vaccine antigen in this study. The F-VLP was encapsulated in a microparticle (MP) matrix composed of cross-linked bovine serum albumin (BSA) to enhance the antigen presentation and uptake. Moreover, a painless vaccination method would be desirable for an infectious disease that mainly affects young children. Thus, an ablative laser device, Precise Laser Epidermal System (P.L.E.A.S.E), was utilized to create micropores on the skin for vaccine delivery. We observed enhanced antigen presentation of the vaccine microparticles (F-VLP MP) with and without the adjuvant monophosphoryl lipid A (MPL-A) MP in dendritic cells. Consequently, Swiss Webster mice were immunized with the adjuvanted vaccine microparticles using the P.L.E.A.S.E laser to study the in vivo immunogenicity. The immunized mice had high serum immunoglobulin (IgG, IgG2a) levels, indicating a Th1 response. Subsequent analysis of lung homogenates post- RSV challenge revealed high IgA, indicating generation of a mucosal immune response upon intradermal immunization. Flowcytometry analysis showed high CD8+, and CD4+ expression in the lymph node and spleen of the adjuvanted vaccine microparticle immunized mice. Increased expression of interferon gamma (IFN-γ) in the spleen cells further proved Th1 polarized immune response. Finally, an immune plaque assay indicated significantly low lung viral titer in the mice immunized with intradermal adjuvanted vaccine microparticles. Thus, ablative laser-assisted immunization with the F-VLP based adjuvanted vaccine microparticles could be a promising vaccine candidate for RSV.

Broad protective vaccination against systemic Escherichia coli with autotransporter antigens

Extraintestinal pathogenic Escherichia coli (ExPEC) is the leading cause of adult life-threatening sepsis and urinary tract infections (UTI). The emergence and spread of multidrug-resistant (MDR) ExPEC strains result in a considerable amount of treatment failure and hospitalization costs, and contribute to the spread of drug resistance amongst the human microbiome. Thus, an effective vaccine against ExPEC would reduce morbidity and mortality and possibly decrease carriage in healthy or diseased populations. A comparative genomic analysis demonstrated a gene encoding an invasin-like protein, termed sinH, annotated as an autotransporter protein, shows high prevalence in various invasive ExPEC phylogroups, especially those associated with systemic bacteremia and UTI. Here, we evaluated the protective efficacy and immunogenicity of a recombinant SinH-based vaccine consisting of either domain-3 or domains-1,2, and 3 of the putative extracellular region of surface-localized SinH. Immunization of a murine host with SinH-based antigens elicited significant protection against various strains of the pandemic ExPEC sequence type 131 (ST131) as well as multiple sequence types in two distinct models of infection (colonization and bacteremia). SinH immunization also provided significant protection against ExPEC colonization in the bladder in an acute UTI model. Immunized cohorts produced significantly higher levels of vaccine-specific serum IgG and urinary IgG and IgA, findings consistent with mucosal protection. Collectively, these results demonstrate that autotransporter antigens such as SinH may constitute promising ExPEC phylogroup-specific and sequence-type effective vaccine targets that reduce E. coli colonization and virulence.

Oral vaccination with recombinant Lactobacillus casei expressing Aeromonas hydrophila Aha1 against A. hydrophila infections in common carps

The immunogenicity of Aha1, an OMP of Aeromonas hydrophila mediating the adhesion of bacteria onto the mucosal surface of hosts has been established. In this study, recombinant vectors, pPG1 and pPG2, carrying a 1366 bp DNA fragment that was responsible for encoding the 49 kDa Aha1 from A. hydrophila were constructed, respectively, then electroporated into a probiotic strain Lactobacillus casei CC16 separately to generate two types of recombinants, L. casei-pPG1-Aha1 (Lc-pPG1-Aha1) and L. casei-pPG2-Aha1 (Lc-pPG2-Aha1). Subsequently, these were orally administered into common carps to examine their immunogenicity. The expression and localization of the expressed Aha1 protein relative to the carrier L. casei was validated via Western blotting, flow cytometry, and immune fluorescence separately. The recombinant vaccines produced were shown high efficacies, stimulated higher level of antibodies and AKP, ACP, SOD, LZM, C3, C4 in serum in hosts. Immune-related gene expressions of cytokines including IL-10, IL-1β, TNF-α, IFN-γ in the livers, spleens, HK, and intestines were up-regulated significantly. Besides, a more potent phagocytosis response was observed in immunized fish, and higher survival rates were presented in common carps immunized with Lc-pPG1-Aha1 (60%) and Lc-pPG2-Aha1 (50%) after re-infection with virulent strain A. hydrophila. Moreover, the recombinant L. casei were shown a stronger propensity for survivability in the intestine in immunized fish. Taken together, the recombinant L. casei strains might be promising candidates for oral vaccination against A. hydrophila infections in common carps.

Development of Nasal Vaccines and the Associated Challenges

Viruses, bacteria, fungi, and several other pathogenic microorganisms usually infect the host via the surface cells of respiratory mucosa. Nasal vaccination could provide a strong mucosal and systemic immunity to combat these infections. The intranasal route of vaccination offers the advantage of easy accessibility over the injection administration. Therefore, nasal immunization is considered a promising strategy for disease prevention, particularly in the case of infectious diseases of the respiratory system. The development of a nasal vaccine, particularly the strategies of adjuvant and antigens design and optimization, enabling rapid induction of protective mucosal and systemic responses against the disease. In recent times, the development of efficacious nasal vaccines with an adequate safety profile has progressed rapidly, with effective handling and overcoming of the challenges encountered during the process. In this context, the present report summarizes the most recent findings regarding the strategies used for developing nasal vaccines as an efficient alternative to conventional vaccines.

Towards the future exploration of mucosal mRNA vaccines against emerging viral diseases; lessons from existing next-generation mucosal vaccine strategies

The mRNA vaccine platform has offered the greatest potential in fighting the COVID-19 pandemic owing to rapid development, effectiveness, and scalability to meet the global demand. There are many other mRNA vaccines currently being developed against different emerging viral diseases. As with the current COVID-19 vaccines, these mRNA-based vaccine candidates are being developed for parenteral administration via injections. However, most of the emerging viruses colonize the mucosal surfaces prior to systemic infection making it very crucial to target mucosal immunity. Although parenterally administered vaccines would induce a robust systemic immunity, they often provoke a weak mucosal immunity which may not be effective in preventing mucosal infection. In contrast, mucosal administration potentially offers the dual benefit of inducing potent mucosal and systemic immunity which would be more effective in offering protection against mucosal viral infection. There are however many challenges posed by the mucosal environment which impede successful mucosal vaccination. The development of an effective delivery system remains a major challenge to the successful exploitation of mucosal mRNA vaccination. Nonetheless, a number of delivery vehicles have been experimentally harnessed with different degrees of success in the mucosal delivery of mRNA vaccines. In this review, we provide a comprehensive overview of mRNA vaccines and summarise their application in the fight against emerging viral diseases with particular emphasis on COVID-19 mRNA platforms. Furthermore, we discuss the prospects and challenges of mucosal administration of mRNA-based vaccines, and we explore the existing experimental studies on mucosal mRNA vaccine delivery.

Sublingual Boosting with a Novel Mucoadhesive Thermogelling Hydrogel Following Parenteral CAF01 Priming as a Strategy Against Chlamydia trachomatis

Chlamydia trachomatis is the most prevalent sexually transmitted disease of bacterial origin. The high number of asymptomatic cases makes it difficult to stop the transmission, requiring vaccine development. Herein, a strategy is proposed to obtain local genital tract immunity against C. trachomatis through parenteral prime and sublingual boost. Subcutaneous administration of chlamydia CTH522 subunit vaccine loaded in the adjuvant CAF01 is combined with sublingual administration of CTH522 loaded in a novel thermosensitive and mucoadhesive hydrogel. Briefly, a ternary optimized hydrogel (OGEL) with desirable biological and physicochemical properties is obtained using artificial intelligence techniques. This formulation exhibits a high gel strength and a strong mucoadhesive, adhesive and cohesive nature. The thermosensitive properties of the hydrogel facilitate application under the tongue. Meanwhile the fast gelation at body temperature together with rapid antigen release should avoid CTH522 leakage by swallowing and increase the contact with sublingual tissue, thus promoting absorption. In vivo studies demonstrate that parenteral-sublingual prime-boost immunization, using CAF01 and OGEL as CTH522 vaccine carriers, shows a tendency to increase cellular (Th1/Th17) immune responses when compared to mucosal or parenteral vaccination alone. Furthermore, parenteral prime with CAF01/CTH522 followed by sublingual boosting with OGEL/CTH522 elicits a local IgA response in the genital tract.

Mucosal Vaccination With Recombinant Tm-WAP49 Protein Induces Protective Humoral and Cellular Immunity Against Experimental Trichuriasis in AKR Mice

Trichuriasis is one of the most common neglected tropical diseases of the world's poorest people. A recombinant vaccine composed of Tm-WAP49, an immunodominant antigen secreted by adult Trichuris stichocytes into the mucosa of the cecum to which the parasite attaches, is under development. The prototype is being evaluated in a mouse model of Trichuris muris infection, with the ultimate goal of producing a mucosal vaccine through intranasal delivery. Intranasal immunization of mice with Tm-WAP49 formulated with the adjuvant OCH, a truncated analog of alpha-GalCer with adjuvanticity to stimulate natural killer T cells (NKT) and mucosal immunity, induced significantly high levels of IgG and its subclasses (IgG1 and IgG2a) in immunized mice. This also resulted in a significant reduction of worm burden after challenge with T. muris-infective eggs. The addition of QS-21 adjuvant to this vaccine formulation further reduced worm counts. The improved protection from the dual-adjuvanted vaccine correlated with higher serum antibody responses (IgG, IgG1, IgG2a, IgA) as well as with the induction of antigen-specific IgA in the nasal mucosa. It was also associated with the robust cellular responses including functional subsets of CD4 T cells producing IL-4, and cytotoxic CD8 T cells expressing granzyme B. The worm reduction achieved by mucosal immunization was higher than that induced by subcutaneous immunization. Intranasal immunization also induced a significantly higher nasal mucosa-secreted antigen-specific IgA response, as well as higher functional cellular responses including CD4⁺IL4⁺ (Th1) and CD8⁺GnzB⁺ (Th2) T cells, and antigen-specific INFγ-producing T cells in both spleen and MLNs and antibody-producing B cells (CD19⁺B220⁺/B220⁺GL7⁺). Mucosal immunization further induced long-term T lymphocyte memory with increased central (CD62L⁺CD44⁺) and effector (CD62L^-CD44⁺) memory subsets of both CD4 and CD8 T cells at 60 days after the last immunization. In summary, intranasal immunization with recombinant Tm-WAP49 protein induced strong protection versus murine trichuriasis. It represents a promising vaccination approach against intestinal nematodes.

STxB as an Antigen Delivery Tool for Mucosal Vaccination

Immunotherapy against cancer and infectious disease holds the promise of high efficacy with minor side effects. Mucosal vaccines to protect against tumors or infections disease agents that affect the upper airways or the lung are still lacking, however. One mucosal vaccine candidate is the B-subunit of Shiga toxin, STxB. In this review, we compare STxB to other immunotherapy vectors. STxB is a non-toxic protein that binds to a glycosylated lipid, termed globotriaosylceramide (Gb3), which is preferentially expressed by dendritic cells. We review the use of STxB for the cross-presentation of tumor or viral antigens in a MHC class I-restricted manner to induce humoral immunity against these antigens in addition to polyfunctional and persistent CD4⁺ and CD8⁺ T lymphocytes capable of protecting against viral infection or tumor growth. Other literature will be summarized that documents a powerful induction of mucosal IgA and resident memory CD8⁺ T cells against mucosal tumors specifically when STxB-antigen conjugates are administered via the nasal route. It will also be pointed out how STxB-based vaccines have been shown in preclinical cancer models to synergize with other therapeutic modalities (immune checkpoint inhibitors, anti-angiogenic therapy, radiotherapy). Finally, we will discuss how molecular aspects such as low immunogenicity, cross-species conservation of Gb3 expression, and lack of toxicity contribute to the competitive positioning of STxB among the different DC targeting approaches. STxB thereby appears as an original and innovative tool for the development of mucosal vaccines in infectious diseases and cancer.

Recent Advances in the Noninvasive Delivery of mRNA

Over the past two decades, research on mRNA-based therapies has exploded, mainly because of the inherent advantages of mRNA, including a low integration probability, transient expression, and simple and rapid in vitro transcription production approaches. In addition, thanks to improved stability and reduced immunogenicity by advanced strategies, the application of mRNA has expanded from protein replacement therapy to vaccination, gene editing and other fields, showing great promise for clinical application. Recently, with the successive launch of two mRNA-based COVID-19 vaccines, mRNA technology has attracted an enormous amount of attention from scientific researchers as well as pharmaceutical companies. Because of the large molecular weight, hydrophilicity, and highly negative charge densities of mRNA, it is difficult to overcome the intracellular delivery barriers. Therefore, various delivery vehicles have been developed to achieve more effective mRNA delivery. In general, conventional mRNA administration methods are based on injection strategies, including intravenous, intramuscular, intradermal, and subcutaneous injections. Although these routes circumvent the absorption barriers to some extent, they bring about injection-related concerns such as safety issues, pain, low compliance, and difficulty in repeated dosing, increasing the need to explore alternative strategies for noninvasive delivery. The ideal noninvasive delivery systems are featured with easy to use, low risks of infection, and good patient compliance. At the same time, they allow patients to self-administer, reducing reliance on professional healthcare workers and interference with bodily functions and daily life. In particular, the noninvasive mucosal delivery of mRNA vaccines can induce mucosal immune responses, which are important for resisting pathogens infected through mucosal routes.Because of the potential clinical benefits mentioned above, we detailed the existing strategies for the noninvasive delivery of mRNA in this review, including delivery via the nasal, pulmonary, vaginal, and transdermal routes. First, we discussed the unique strengths and biological hindrances of each route on the basis of physiology. Next, we comprehensively summarized the research progress reported so far and analyzed the technologies and delivery vehicles used, hoping to provide some references for further explorations. Among these noninvasive routes, nasal and pulmonary delivery are the earliest and most intensively studied areas, mostly owing to their favorable physiological structures: the nasal or pulmonary mucosa is easily accessible, highly permeable and highly vascularized. In contrast, the development of vaginal mRNA delivery is relatively less reported, and the current research mainly focused on some local applications. In addition, microneedles have also been investigated to overcome skin barriers for mRNA delivery in recent years, making microneedle-based delivery an emerging alternative pathway. In summary, a variety of mRNA formulations and delivery strategies have been developed for noninvasive mRNA delivery, skillfully combining appropriate vehicles or physical technologies to enhance effectiveness. We surmise that continuous advances and technological innovations in the development of mRNA noninvasive delivery will accelerate the translation from experimental research to clinical application.

Evaluation of Cell-Penetrating Peptides as Mucosal Immune Enhancers for Nasal Vaccination

Cell-penetrating peptides (CPPs) have been evaluated as enhancers in drug delivery, their addition in medical formulations favors drug absorption allowing obtaining the pharmacological effect with lower doses. In vaccine formulations their inclusion has been also explored with interesting results. Currently mucosal vaccination constitutes a promising alternative with the main advantage of inducing both systemic and mucosal immune responses, which are crucial for control tumors and infections at mucosal tissues. In the present work the nasal immune-enhancing effect of four CPPs was evaluated in Balb/c mice. Animals were intranasally immunized with CPP and the recombinant hepatitis B surface protein (HBsAg) as model antigen. The antibody response in sera and mucosal tissue was measured by ELISA. The IFN-γ secretion response at spleen was also evaluated by ELISPOT and ELISA. Among the CPPs studied one novel peptide stand out by its ability to potentiate the humoral and cellular immune response against the co-administered antigen. Considering that the use of mucosal routes is a promising strategy in vaccination, which are gaining special relevance nowadays in the development of novel candidates against SARS-CoV-2 and other potential emerging respiratory virus, the searching and development of safe mucosal adjuvants constitute a current need.

Mesoporous silica nanoparticles-based formulations of a chimeric proteinous vaccine candidate against necrotic enteritis disease

To develop a nanoparticle-based vaccine against necrotic enteritis, a chimeric antigen (rNA) consisting of the main antigens of Clostridium perfringens, NetB, and Alpha toxin, was prepared. Then, the rNA molecules were loaded onto the functionalized mesoporous silica nanoparticles (MSNPs) using physical adsorption or covalent conjugation methods. The characterization of synthesized nanoparticles was performed by scanning electron microscopy, dynamic light scattering, zeta potential measurement, Fourier transform infrared spectroscopy, and thermogravimetry techniques. The results revealed that the spherical nanoparticles with an average diameter of 90 ± 12 nm and suitable surface chemistries are prepared. MSNPs-based formulations did not show any significant toxicity on the chicken embryo fibroblast cells. The results of the challenge experiments using subcutaneous or oral administration of the as-prepared formulations in the animal model showed that the as-prepared nanosystems, similar to those formulated with a commercial adjuvant (Montanide), present stronger humoral immune responses as compared to that of the free proteins. It was also indicated that the best protection is obtained in groups vaccinated with MSNPs-based nanovaccine, especially those who orally received covalently conjugated nanovaccine candidates. These results recommend that the MSNPs-based formulated chimeric proteinous vaccine candidates can be considered as an effective immunizing system for the oral vaccination of poultry against gastrointestinal infectious diseases.

Mucosal Vaccination Primes NK Cell-Dependent Development of CD8+ T Cells Against Pulmonary Brucella Infection

Past studies with the live, double-mutant B. abortus (znBAZ) strain resulted in nearly complete protection of mice against pulmonary challenge with wild-type (wt) Brucella via a dominant CD8+ T cell response. To understand the contribution innate immune cells in priming CD8+ T cell responses, mice were nasally dosed with wt B. abortus, smooth vaccine strain 19 (S19), or znBAZ, and examined for innate immune cell activation. Flow cytometric analysis revealed that znBAZ, but not wt B. abortus nor S19 infection, induces up to a 5-fold increase in the frequency of IFN-γ-producing NK cells in mouse lungs. These NK cells express increased CXCR3 and Ki67, indicating their recruitment and proliferation subsequent to znBAZ infection. Their activation status was augmented noted by the increased NKp46 and granzyme B, but decreased NKG2A expression. Further analysis demonstrated that both lung caspase-1+ inflammatory monocytes and monocyte-derived macrophages secrete chemokines and cytokines responsible for NK cell recruitment and activation. Moreover, neutralizing IL-18, an NK cell-activating cytokine, reduced the znBAZ-induced early NK cell response. NK cell depletion also significantly impaired lung dendritic cell (DC) activation and migration to the lower respiratory lymph nodes (LRLNs). Both lung DC activation and migration to LRLNs were significantly impaired in NK cell-depleted or IFN-γ-/- mice, particularly the CD11b+ and monocytic DC subsets. Furthermore, znBAZ vaccination significantly induced CD8+ T cells, and upon in vivo NK cell depletion, CD8+ T cells were reduced 3-fold compared to isotype-treated mice. In summary, these data show that znBAZ induces lung IFN-γ+ NK cells, which plays a critical role in influencing lung DC activation, migration, and promoting protective CD8+ T cell development.

Twenty years of research on HPV vaccines based on genetically modified lactic acid bacteria: an overview on the gut-vagina axis

Most cervical cancer (CxCa) are related to persistent infection with high-risk human papillomavirus (HR-HPV) in the cervical mucosa, suggesting that an induction of mucosal cell-mediated immunity against HR-HPV oncoproteins can be a promising strategy to fight HPV-associated CxCa. From this perspective, many pre-clinical and clinical trials have proved the potential of lactic acid bacteria (LAB) genetically modified to deliver recombinant antigens to induce mucosal, humoral and cellular immunity in the host. Altogether, the outcomes of these studies suggest that there are several key factors to consider that may offer guidance on improvement protein yield and improving immune response. Overall, these findings showed that oral LAB-based mucosal HPV vaccines expressing inducible surface-anchored antigens display a higher potential to induce particularly specific systemic and mucosal cytotoxic cellular immune responses. In this review, we describe all LAB-based HPV vaccine investigations by reviewing databases from international studies between 2000 and 2020. Our aim is to promote the therapeutic HPV vaccines knowledge and to complete the gaps in this field to empower scientists worldwide to make proper decisions regarding the best strategies for the development of therapeutic HPV vaccines.

Immunology-Guided Biomaterial Design for Mucosal Cancer Vaccines

Cancer of mucosal tissues is a major cause of worldwide mortality for which only palliative treatments are available for patients with late-stage disease. Engineered cancer vaccines offer a promising approach for inducing antitumor immunity. The route of vaccination plays a major role in dictating the migratory pattern of lymphocytes, and thus vaccine efficacy in mucosal tissues. Parenteral immunization, specifically subcutaneous and intramuscular, is the most common vaccination route. However, this induces marginal mucosal protection in the absence of tissue-specific imprinting signals. To circumvent this, the mucosal route can be utilized, however degradative mucosal barriers must be overcome. Hence, vaccine administration route and selection of materials able to surmount transport barriers are important considerations in mucosal cancer vaccine design. Here, an overview of mucosal immunity in the context of cancer and mucosal cancer clinical trials is provided. Key considerations are described regarding the design of biomaterial-based vaccines that will afford antitumor immune protection at mucosal surfaces, despite limited knowledge surrounding mucosal vaccination, particularly aided by biomaterials and mechanistic immune-material interactions. Finally, an outlook is given of how future biomaterial-based mucosal cancer vaccines will be shaped by new discoveries in mucosal vaccinology, tumor immunology, immuno-therapeutic screens, and material-immune system interplay.

A probiotic treatment increases the immune response induced by the nasal delivery of spore-adsorbed TTFC

Background

Spore-forming bacteria of the Bacillus genus are widely used probiotics known to exert their beneficial effects also through the stimulation of the host immune response. The oral delivery of B. toyonensis spores has been shown to improve the immune response to a parenterally administered viral antigen in mice, suggesting that probiotics may increase the efficiency of systemic vaccines. We used the C fragment of the tetanus toxin (TTFC) as a model antigen to evaluate whether a treatment with B. toyonensis spores affected the immune response to a mucosal antigen.

Results

Purified TTFC was given to mice by the nasal route either as a free protein or adsorbed to B. subtilis spores, a mucosal vaccine delivery system proved effective with several antigens, including TTFC. Spore adsorption was extremely efficient and TTFC was shown to be exposed on the spore surface. Spore-adsorbed TTFC was more efficient than the free antigen in inducing an immune response and the probiotic treatment improved the response, increasing the production of TTFC-specific secretory immunoglobin A (sIgA) and causing a faster production of serum IgG. The analysis of the induced cytokines indicated that also the cellular immune response was increased by the probiotic treatment. A 16S RNA-based analysis of the gut microbial composition did not show dramatic differences due to the probiotic treatment. However, the abundance of members of the Ruminiclostridium 6 genus was found to correlate with the increased immune response of animals immunized with the spore-adsorbed antigen and treated with the probiotic.

Conclusion

Our results indicate that B. toyonensis spores significantly contribute to the humoral and cellular responses elicited by a mucosal immunization with spore-adsorbed TTFC, pointing to the probiotic treatment as an alternative to the use of adjuvants for mucosal vaccinations.

Intranasal delivery system of bacterial antigen using thermosensitive hydrogels based on a Pluronic-Gantrez conjugate

Thermosensitive hydrogels have been studied as feasible needle-avoidance alternative to vaccine delivery. In this work, we report the development of a new thermal-sensitive hydrogel for intranasal vaccine delivery. This delivery system was formulated with a combination of the polymer Gantrez® AN119 and the surfactant Pluronic® F127 (PF127), with a high biocompatibility, biodegradability and immunoadjuvant properties. Shigella flexneri outer membrane vesicles were used as the antigen model. A stable and easy-to-produce thermosensitive hydrogel which allowed the incorporation of the OMV-antigenic complex was successfully synthetized. A rapid gel formation was achieved at body temperature, which prolonged the OMV-antigens residence time in the nasal cavity of BALB/c mice when compared to intranasal delivery of free-OMVs. In addition, the bacterial antigens showed a fast release profile from the hydrogel in vitro, with a peak at 30 min of incubation at 37 °C. Hydrogels appeared to be non-cytotoxic in the human epithelial HeLa cell line and nose epithelium as well, as indicated by the absence of histopathological features. Immunohistochemical studies revealed that after intranasal administration the OMVs reached the nasal associated lymphoid tissue. These results support the use of here described thermosensitive hydrogels as a potential platform for intranasal vaccination.

MUCOSAL anti-infections vaccines: Beyond conventional vaccines

An urgent search is currently underway for alternatives to antibiotics to prevent infections, due to the accelerated evolution and increase in antibiotic resistance. This problem is more serious for patients with recurrent infections, since they have to use many cycles of antibiotics per year, so the risk for antibiotic resistance is higher and can be life-threatening. In recent years, the use of prophylactic vaccines via the mucosal route for these patients with recurrent infections has been demonstrated as a potentially beneficial and safe alternative to prevent infections. The new knowledge about mucosal immunity and trained immunity, a form of innate immunity memory that can enhance the response to different infectious threads, has made it easier to extend its use. The application of the new concepts of trained immunity may explain the simultaneous pro-tolerogenic and boosting effect or effects of these drugs on diverse immune cells for different infections. In this review, we describe the immunomodulatory mechanisms of mucosal polybacterial vaccines and their connection with trained immunity and its utility in the prevention of recurrent infections in immunosuppressed patients.

Nasal route for vaccine and drug delivery: Features and current opportunities

Mucosal administration, and specifically nasal route, constitutes an alternative and promising strategy for drug and vaccine delivery. Mucosal routes have several advantages supporting their selective use for different pathologies. Currently, many efforts are being made to develop effective drug formulations and novel devices for nasal delivery. This review described the structure and main characteristics of the nasal cavity. The advantages, achievements and challenges of the nasal route use for medical purposes are discussed, with particular focus on vaccine delivery. Compelling evidences support the potentialities and safety of the nasal delivery of vaccines and drugs. This alternative route could become a solution for many unmet medical issues and also may facilitate and cheapen massive immunization campaigns or long-lasting chronic treatments. Nowadays, in spite of certain remaining skepticism, the field of nasal delivery of drugs and vaccines is growing fast, bolstered by current developments in nanotechnology, imaging and administration devices. A notable increase in the number of approved drugs for nasal administration is envisaged.

Sublingual Immunotherapy Attenuates Nasal Symptoms Upon Allergen Exposure in Murine Allergic Rhinitis Model via an Induction of IL-10 producing T cells in Submandibular Lymph Node

OBJECTIVE

Sublingual immunotherapy has been considered to be a painless and effective therapeutic treatment of patients with allergic rhinitis. Its mechanism of action has been elucidated, but there are still controversies among many reports between clinical efficacy and laboratory data. Therefore, its mechanism of action needs to be investigated further by using promising animal models such as rodents and monkeys.

MATERIALS AND METHODS

Bearing this in mind, in our present study, we successfully constructed an effective murine model for sublingual immunotherapy (SLIT) in allergic rhinitis in which mice were sublingually administered ovalbumin (OVA), followed by intraperitoneal (ip) sensitization and intranasal (i.n.) challenge of OVA.

RESULTS

To summarize our experimental data, nasal symptoms such as sneezing and nasal rubbing of sublingually treated mice were significantly attenuated in accordance with lower specific IgE antibodies in sera. Histological analysis of eosinophil recruitment in nasal mucosae reveals less allergic inflammation in sublingually treated mice. Interleukin-10 (IL-10) production and IL-10-specific mRNA gene expression of cultured submandibular lymph node (SMLN) cells with OVA, obtained from sublingually treated mice, were significantly higher than those of mice without sublingual treatment.

CONCLUSION

These results demonstrate that sublingually introduced antigens can actually attenuate nasal symptoms in a murine allergic rhinitis model upon allergen exposures. Furthermore, our immunological data might indicate an important role of IL-10 producing T cells in SMLN to control nasal allergic reaction.

Antibodies prevalence against Haemophilus influenzae type b in Jeddah population, Saudi Arabia. II. Antibodies subclasses

Our previous reported that Jeddah, Saudi Arabia population have a comparable and protective herd immunity represented by IgG, IgA and IgM against Haemophilus influenzae type b (Hib), by using indirect ELISA test was used to evaluate Haemophilus influenzae type b (Hib) anti-polyribosyl-ribitol phosphate (PRP) total antibodies (IgM, IgG, IgA) in 1,003 sera samples. Current report was evaluated the IgG and IgA subclasses responsible about this protection using same methodology. IgG, IgA, and their subclasses are responsible about this circulating protection. Our study will consider the first report evaluate the levels of IgA subclasses and its relation to ages, as well as the relations between anti-Hib antibody subclass and age. The current results demonstrated that the highest levels concentrated in IgG1 and IgG2, while IgG3 and IgG4 showed the lowest levels. So, their concentrations were arranged in IgG1 > IgG2 > IgG3 > IgG4. The results indicated that the age and gender have no effect on both IgG or IgA subclasses in healthy immunized individuals enrolled. While, IgA1 concentrations were significantly higher than IgA2 in all age categories regardless of gender. It seem that the IgG1, IgG2 and IgA1 subclasses were the main constituent of Jeddah herd immunity against Hib. Finally, to the best of our knowledge, there were no previous reports that focusing on the levels of IgA subclasses and its relation to ages, so our study considers the first worldwide.

Oral immunization with recombinant Lactococcus lactis NZ9000 expressing human papillomavirus type 16 E7 antigen and evaluation of its immune effects in female C57BL/6 mice

The ORFs of both native and codon-optimized E7 genes were successfully fused to SPusp45 signal peptide and expressed by a nisin-controlled gene expression system in the NZ9000 strains of Lactococcus lactis. Recombinant strains were confirmed by Western blot analysis. To measure immune responses against the E7 antigen, specific-pathogen-free C57BL/6 mice were inoculated with L lactis harboring pNZ8123-rE7 by oral gavage. Then, specific antibodies and cytokines were measured by enzyme-linked immunosorbent assay and enzyme-linked immunospot assay, respectively. Oral administration of L lactis strains expressing rE7 elicited the highest levels of E7-specific antibody and greatest numbers of E7-specific CD4⁺ T helper and CD8⁺ T cell precursors. Our outcomes indicated that the HPV-16 E7 specific IL-2- and IFN-γ-secreting T cells in antigen-stimulated splenocytes and intestinal mucosal lymphocytes were significantly higher than the control groups. Our data also demonstrated that mice vaccinated with recombinant L lactis were able to generate potent protective effects against challenge with the E7-expressing tumor cell line (TC-1). Moreover, L lactis containing pNZ8123-HPV16-optiE7 showed strong therapeutic antitumor effects against established tumors in vivo. These findings demonstrate that recombinant L lactis induce both humoral and cellular immune responses in mice and are therefore recommended for therapeutic treatments in humans after oral administration.

Oral Vaccine Delivery for Intestinal Immunity-Biological Basis, Barriers, Delivery System, and M Cell Targeting

Most currently available commercial vaccines are delivered by systemic injection. However, needle-free oral vaccine delivery is currently of great interest for several reasons, including the ability to elicit mucosal immune responses, ease of administration, and the relatively improved safety. This review summarizes the biological basis, various physiological and immunological barriers, current delivery systems with delivery criteria, and suggestions for strategies to enhance the delivery of oral vaccines. In oral vaccine delivery, basic requirements are the protection of antigens from the GI environment, targeting of M cells and activation of the innate immune response. Approaches to address these requirements aim to provide new vaccines and delivery systems that mimic the pathogen's properties, which are capable of eliciting a protective mucosal immune response and a systemic immune response and that make an impact on current oral vaccine development.

Memory Inflation Drives Tissue-Resident Memory CD8+ T Cell Maintenance in the Lung After Intranasal Vaccination With Murine Cytomegalovirus

Tissue-resident memory T (T_RM) cells provide first-line defense against invading pathogens encountered at barrier sites. In the lungs, T_RM cells protect against respiratory infections, but wane more quickly than T_RM cells in other tissues. This lack of a sustained T_RM population in the lung parenchyma explains, at least in part, why infections with some pathogens, such as influenza virus and respiratory syncytial virus (RSV), recur throughout life. Intranasal (IN) vaccination with a murine cytomegalovirus (MCMV) vector expressing the M protein of RSV (MCMV-M) has been shown to elicit robust populations of CD8⁺ T_RM cells that accumulate over time and mediate early viral clearance. To extend this finding, we compared the inflationary CD8⁺ T cell population elicited by MCMV-M vaccination with a conventional CD8⁺ T cell population elicited by an MCMV vector expressing the M2 protein of RSV (MCMV-M2). Vaccination with MCMV-M2 induced a population of M2-specific CD8⁺ T_RM cells that waned rapidly, akin to the M2-specific CD8⁺ T_RM cell population elicited by infection with RSV. In contrast to the natural immunodominance profile, however, coadministration of MCMV-M and MCMV-M2 did not suppress the M-specific CD8⁺ T cell response, suggesting that progressive expansion was driven by continuous antigen presentation, irrespective of the competitive or regulatory effects of M2-specific CD8⁺ T cells. Moreover, effective viral clearance mediated by M-specific CD8⁺ T_RM cells was not affected by the coinduction of M2-specific CD8⁺ T cells. These data show that memory inflation is required for the maintenance of CD8⁺ T_RM cells in the lungs after IN vaccination with MCMV.

Critical micelle concentration and particle size determine adjuvanticity of cyclic lipopeptides

Cyclic lipopeptides such as surfactin and polymyxin have potent mucosal adjuvant properties. Cyclic lipopeptides are tensioactive compounds, but the relationship between adjuvanticity and surface activity is unknown. Here, we show that the critical micelle concentration (cmc) of surfactant and particle size of the surfactant-protein complex are important determinants of cyclic lipopeptide adjuvanticity. We found that the diameter of cyclic lipopeptide-ovalbumin (OVA) complex particles was significantly larger than that in the solutions of OVA alone at cyclic lipopeptide concentrations above the cmc. OVA-specific antibody titres in mice immunized intranasally with OVA and a cyclic lipopeptide at concentrations above its cmc were significantly higher than those in mice immunized with OVA plus the same dose of the cyclic lipopeptide but administered with formulations in which cyclic lipopeptide concentration was below the cmc. Thus, the concentration of the cyclic lipopeptide in the formulation at immunization, but not its overall dose, was critical for its adjuvanticity. Furthermore, two types of aggregates, the cyclic lipopeptide simplex micelles and the cyclic lipopeptide-OVA complex micelles, were found in formulations with SF concentrations above its cmc. Degranulation of mast cells exposed to SF simplex micelles was more pronounced when SF concentration was above the cmc. In conclusion, our study showed that surface activity properties, such as the cmc and the size of surfactant-protein complex, contribute to the adjuvanticity of cyclic lipopeptides. Our study proposes a novel idea that cmc is a key parameter for tensioactive adjuvants.

Therapeutic cancer vaccine: building the future from lessons of the past

Anti-cancer vaccines have raised many hopes from the start of immunotherapy but have not yet been clinically successful. The few positive results of anti-cancer vaccines have been observed in clinical situations of low tumor burden or preneoplastic lesions. Several new concepts and new results reposition this therapeutic approach in the field of immunotherapy. Indeed, cancers that respond to anti-PD-1/PD-L1 (20-30%) are those that are infiltrated by anti-tumor T cells with an inflammatory infiltrate. However, 70% of cancers do not appear to have an anti-tumor immune reaction in the tumor microenvironment. To induce this anti-tumor immunity, therapeutic combinations between vaccines and anti-PD-1/PD-L1 are being evaluated. In addition, the identification of neoepitopes against which the immune system is less tolerated is giving rise to a new enthusiasm by the first clinical results of the vaccine including these neoepitopes in humans. The ability of anti-cancer vaccines to induce a population of anti-tumor T cells called memory resident T cells that play an important role in immunosurveillance is also a new criterion to consider in the design of therapeutic vaccines.

Recombinant Invasive Lactococcus lactis Carrying a DNA Vaccine Coding the Ag85A Antigen Increases INF-γ, IL-6, and TNF-α Cytokines after Intranasal Immunization

Tuberculosis (TB) remains a major threat throughout the world and in 2015 it caused the death of 1.4 million people. The Bacillus Calmette-Guérin is the only existing vaccine against this ancient disease; however, it does not provide complete protection in adults. New vaccines against TB are eminently a global priority. The use of bacteria as vehicles for delivery of vaccine plasmids is a promising vaccination strategy. In this study, we evaluated the use of, an engineered invasive Lactococcus lactis (expressing Fibronectin-Binding Protein A from Staphylococcus aureus) for the delivery of DNA plasmid to host cells, especially to the mucosal site as a new DNA vaccine against tuberculosis. One of the major antigens documented that offers protective responses against Mycobacterium tuberculosis is the Ag85A. L. lactis FnBPA⁺ (pValac:Ag85A) which was obtained and used for intranasal immunization of C57BL/6 mice and the immune response profile was evaluated. In this study we observed that this strain was able to produce significant increases in the amount of pro-inflammatory cytokines (IFN-γ, TNF-α, and IL-6) in the stimulated spleen cell supernatants, showing a systemic T helper 1 (Th1) cell response. Antibody production (IgG and sIgA anti-Ag85A) was also significantly increased in bronchoalveolar lavage, as well as in the serum of mice. In summary, these findings open new perspectives in the area of mucosal DNA vaccine, against specific pathogens using a Lactic Acid Bacteria such as L. lactis.

Induction of resident memory T cells enhances the efficacy of cancer vaccine

Tissue-resident memory T cells (Trm) represent a new subset of long-lived memory T cells that remain in tissue and do not recirculate. Although they are considered as early immune effectors in infectious diseases, their role in cancer immunosurveillance remains unknown. In a preclinical model of head and neck cancer, we show that intranasal vaccination with a mucosal vector, the B subunit of Shiga toxin, induces local Trm and inhibits tumour growth. As Trm do not recirculate, we demonstrate their crucial role in the efficacy of cancer vaccine with parabiosis experiments. Blockade of TFGβ decreases the induction of Trm after mucosal vaccine immunization, resulting in the lower efficacy of cancer vaccine. In order to extrapolate this role of Trm in humans, we show that the number of Trm correlates with a better overall survival in lung cancer in multivariate analysis. The induction of Trm may represent a new surrogate biomarker for the efficacy of cancer vaccine. This study also argues for the development of vaccine strategies designed to elicit them.

Lactobacillus plantarum producing a Chlamydia trachomatis antigen induces a specific IgA response after mucosal booster immunization

Mucosal immunity is important for the protection against a wide variety of pathogens. Traditional vaccines administered via parenteral routes induce strong systemic immunity, but they often fail to generate mucosal IgA. In contrast, bacteria-based vaccines comprise an appealing strategy for antigen delivery to mucosal sites. Vaginal infection with Chlamydia trachomatis can develop into upper genital tract infections that can lead to infertility. Therefore, the development of an effective vaccine against Chlamydia is a high priority. In the present study, we have explored the use of a common lactic acid bacterium, Lactobacillus plantarum, as a vector for delivery of a C. trachomatis antigen to mucosal sites. The antigen, referred as Hirep2 (H2), was anchored to the surface of L. plantarum cells using an N-terminal lipoprotein anchor. After characterization, the constructed strain was used as an immunogenic agent in mice. We explored a heterologous prime-boost strategy, consisting of subcutaneous priming with soluble H2 antigen co-administered with CAF01 adjuvant, followed by an intranasal boost with H2-displaying L. plantarum. The results show that, when used as a booster, the recombinant L. plantarum strain was able to evoke cellular responses. Most importantly, booster immunization with the Lactobacillus-based vaccine induced generation of antigen-specific IgA in the vaginal cavity.

Oral Vaccination with Attenuated Salmonella typhimurium-Delivered TsPmy DNA Vaccine Elicits Protective Immunity against Trichinella spiralis in BALB/c Mice

Background

Our previous studies showed that Trichinella spiralis paramyosin (TsPmy) is an immunomodulatory protein that inhibits complement C1q and C8/C9 to evade host complement attack. Vaccination with recombinant TsPmy protein induced protective immunity against T. spiralis larval challenge. Due to the difficulty in producing TsPmy as a soluble recombinant protein, we prepared a DNA vaccine as an alternative approach in order to elicit a robust immunity against Trichinella infection.

Methods and Findings

The full-length TsPmy coding DNA was cloned into the eukaryotic expression plasmid pVAX1, and the recombinant pVAX1/TsPmy was transformed into attenuated Salmonella typhimurium strain SL7207. Oral vaccination of mice with this attenuated Salmonella-delivered TsPmy DNA vaccine elicited a significant mucosal sIgA response in the intestine and a systemic IgG antibody response with IgG2a as the predominant subclass. Cytokine analysis also showed a significant increase in the Th1 (IFN-γ, IL-2) and Th2 (IL-4, 5, 6, 10) responses in lymphocytes from the spleen and MLNs of immunized mice upon stimulation with TsPmy protein. The expression of the homing receptors CCR9/CCR10 on antibody secreting B cells may be related to the translocation of IgA-secreted B cells to local intestinal mucosa. The mice immunized with Salmonella-delivered TsPmy DNA vaccine produced a significant 44.8% reduction in adult worm and a 46.6% reduction in muscle larvae after challenge with T. spiralis larvae.

Conclusion

Our results demonstrated that oral vaccination with TsPmy DNA delivered by live attenuated S. typhimurium elicited a significant local IgA response and a mixed Th1/Th2 immune response that elicited a significant protection against T. spiralis infection in mice.

Trichinellosis is one of the most important food-borne parasitic zoonoses, and a serious public health issue worldwide. Developing a vaccine is an alternative approach to control the disease. TsPmy is a paramyosin expressed by Trichinella spiralis to bind and neutralize human complement and a vaccine antigen. We made a DNA vaccine of TsPmy orally delivered by attenuated Salmonella typhimurium that elicited a robust Th1/Th2 and mucosa IgA responses, and protected mice against T. spiralis infection with significant worm reduction against larval challenge. The attenuated Salmonella-delivered TsPmy DNA vaccine provides a feasible and promising approach for controlling trichinellosis in human and domestic animals.

Intra-cheek immunization as a novel vaccination route for therapeutic vaccines of head and neck squamous cell carcinomas using plasmo virus-like particles

Despite current therapy, head and neck squamous cell carcinomas (HNSCCs) arising from various mucosal sites of the upper aero-digestive tract frequently relapse in a loco-regional manner and have a poor prognosis. Our objective was to validate an innovative mucosal route of vaccination using plasmo virus-like particles (pVLPs) in a pre-clinical orthotopic model of HNSCCs. For this purpose, we used pVLP-E7, that are plasmid DNA encoding retroviral virus-like particles carrying a truncated E7 oncoprotein from HPV-16 as antigen model, to vaccinate mice bearing pre-established TC-1 tumors implanted into the buccal mucosa. pVLP-E7 were combined with clinical grade TLR agonists (Imiquimod and CpG-ODN). In this pre-clinical orthotopic model, whose tumor microenvironment resembles to those of human HNSCCs, different mucosal vaccination routes were tested for their ability to elicit efficient immune and antitumoral responses. Results showed that mucosal intra-cheek (IC) vaccinations using pVLP-E7, comparatively to intradermic vaccinations (ID), gave rise to higher mobilization of mucosal (CD49a(+)) CD8(+) specific effector T cells in both tumor draining lymph nodes (TdLNs) and tumor microenvironment resulting in better antitumor effects and in a long-term protection against tumor rechallenge. In vivo CD8(+) depletion demonstrated that antitumoral effects were fully dependent upon the presence of CD8(+) T cells. Validation of IC mucosal vaccinations with pVLPs combined with adjuvants using a pre-clinical orthotopic model of HNSCC provides valuable pre-clinical data to rapidly envision the use of such therapeutic vaccines in patients with HNSCCs, inasmuch as vaccinal components and adjuvants can be easily obtained as clinical grade reagents.

Intralymphatic mRNA vaccine induces CD8 T-cell responses that inhibit the growth of mucosally located tumours

The lack of appropriate mouse models is likely one of the reasons of a limited translational success rate of therapeutic vaccines against cervical cancer, as rapidly growing ectopic tumours are commonly used for preclinical studies. In this work, we demonstrate that the tumour microenvironment of TC-1 tumours differs significantly depending on the anatomical location of tumour lesions (i.e. subcutaneously, in the lungs and in the genital tract). Our data demonstrate that E7-TriMix mRNA vaccine-induced CD8⁺ T lymphocytes migrate into the tumour nest and control tumour growth, although they do not express mucosa-associated markers such as CD103 or CD49a. We additionally show that despite the presence of the antigen-specific T cells in the tumour lesions, the therapeutic outcomes in the genital tract model remain limited. Here, we report that such a hostile tumour microenvironment can be reversed by cisplatin treatment, leading to a complete regression of clinically relevant tumours when combined with mRNA immunization. We thereby demonstrate the necessity of utilizing clinically relevant models for preclinical evaluation of anticancer therapies and the importance of a simultaneous combination of anticancer immune response induction with targeting of tumour environment.

Local and systemic adaptive immune responses toward viral infection via gills in ginbuna crucian carp

Recent studies on fish immunity highlighted the significance of gills as mucosal immune tissues. To understand potential of gills as vaccination sites for inducing adaptive systemic immunity, we investigated virus-specific cell-mediated and humoral immune responses following a "per-gill infection method", which directly exposes virus only to gills. The viral load in crucian carp hematopoietic necrosis virus (CHNV)-infected gills decreased after peaking at a particular time point. Furthermore, the viral titers in the gills following the secondary infection were lower than that after the primary infection, indicating that local adaptive immunity helped the elimination of virus. Gene expression analysis demonstrated that IFN-γ in gills and perforin in kidney were increased after the gill infection. CD8(+) cells in kidney leukocytes increased after the secondary infection, whereas IgM(+) cells decreased. These results suggest that IFN-γ and CTL contribute in controlling CHNV-replication in gills and kidney. Gill infection could induce specific cell-mediated cytotoxicity of peripheral blood leukocytes (PBL) and secretion of CHNV-specific IgM in serum, indicating that local priming of the gill site can generate adaptive systemic immunity. Thus, the gills could be prospective antigen-sensitization sites for mucosal vaccination.