Normal structure, function, and histology of mucosa-associated lymphoid tissue

Structural Changes in Large Intestinal Aggregated Lymphoid Follicles in Wistar Rats During Postnatal Ontogeny

Quantitative evaluation of aggregated lymphoid follicles in various compartments of the large intestine was carried out in Wistar rats of different age: newborn (3-4 days), prepubertal (20-30 days), adult (2-3 months), and old (16-18 months). No aggregated lymphoid tissue was detected in the large intestinal mucosa of newborn animals. The cecum of prepubertal, adult, and old animals contained solitary patches with 7-9 follicles. Higher percentage of aggregated lymphoid tissue, associated with colonic mucosa, was explained by enlargement of the lymphoid patch area and of the number of solitary lymphoid follicles during the postnatal ontogenesis. The mean area of a patch in the distal part of the colon in prepubertal, adult, and old animals was 3.2, 2.5, and 2.2 times larger than in the medial part of the intestine, the number of follicles per patch was 2.8, 2.8, and 2.5 times higher, respectively. The differences were significant only for the two younger groups.

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

The mucosal immune system displays several adaptations reflecting the exposure to the external environment. The efficient induction of mucosal immune responses also requires specific approaches, such as the use of appropriate administration routes and specific adjuvants and/or delivery systems. In contrast to vaccines delivered via parenteral routes, experimental, and clinical evidences demonstrated that mucosal vaccines can efficiently induce local immune responses to pathogens or tumors located at mucosal sites as well as systemic response. At least in part, such features can be explained by the compartmentalization of mucosal B and T cell populations that play important roles in the modulation of local immune responses. In the present review, we discuss molecular and cellular features of the mucosal immune system as well as novel immunization approaches that may lead to the development of innovative and efficient vaccines targeting pathogens and tumors at different mucosal sites.

Macrophages and Uveitis in Experimental Animal Models

Resident and infiltrated macrophages play relevant roles in uveitis as effectors of innate immunity and inductors of acquired immunity. They are major effectors of tissue damage in uveitis and are also considered to be potent antigen-presenting cells. In the last few years, experimental animal models of uveitis have enabled us to enhance our understanding of the leading role of macrophages in eye inflammation processes, including macrophage polarization in experimental autoimmune uveoretinitis and the major role of Toll-like receptor 4 in endotoxin-induced uveitis. This improved knowledge should guide advantageous iterative research to establish mechanisms and possible therapeutic targets for human uveitis resolution.

Histologic Features of Postnatal Development of Immune System Organs in the Sprague-Dawley Rat

The immune system of the rat undergoes substantial functional and morphological development during the postnatal period. Some aspects of this development are genetically predetermined, while other aspects depend on environmental influences. Detailed information on postnatal development is important in the interpretation of histopathologic findings in juvenile toxicology and pubertal assay studies, as well as other studies conducted in juvenile rats. Studies were conducted to provide detailed characterization of histologic features of the major functional compartments of immune system organs in male and female Sprague-Dawley rats at weekly intervals from the day of birth through postnatal day (PND) 42. Maturation of the individual immune system organs occurred across a range of ages, with histologic maturation of T-cell-related compartments typically occurring prior to maturation of B-cell-related compartments. The sequence of histologic maturation was bone marrow and thymus on PND 14, mesenteric lymph node on PND 21, Peyer's patches and bronchus-associated lymphoid tissue on PND 28, mandibular lymph node, nasopharynx-associated lymphoid tissue, and diffuse mucosal mononuclear cell population of small intestine on PND 35, and spleen on PND 42. An estimation of functional maturation can be made based on the morphological indications of maturity of each compartment of immune system organs, but histologic indications of maturity do not confirm functional immunocompetence.

Oral antigen exposure in newborn piglets circumvents induction of oral tolerance in response to intraperitoneal vaccination in later life

Background

We previously determined that newborn piglets orally gavaged with Ovalbumin (OVA) responded to systemic OVA re-exposure with tolerance; if adjuvants were included in oral vaccine, piglets responded with antibody-mediated immunity (Vet Immunol Immunopathol 161(3–4):211–21, 2014). Here, we will investigate whether newborn piglets gavaged with a vaccine comprised of OVA plus unmethylated CpG oligodeoxynucleotides (CpG; soluble component; OVA/CpG) combined with OVA plus CpG encapsulated within polyphosphazene microparticles (MP; particulate component) responded with systemic and mucosal immunity. To monitor the response to systemic antigen re-exposure, piglets were i.p.-immunized with OVA plus Incomplete Freund’s Adjuvant (IFA) one month later.

Results

Newborn piglets (n = 5/group) were gavaged with a combined soluble and particulate vaccine consisting of OVA (0.5-0.05 mg) plus 50 μg CpG and 0.5 mg OVA plus 50 μg CpG encapsulated within a polyphosphazene MP (0.5 mg) referred to as OVA/CpG + MP. Control piglets were gavaged with saline alone. Piglets were i.p. immunized with 10 mg OVA (or saline) in IFA at four weeks of age and then euthanized at eight weeks of age. We observed significantly higher titres of serum anti-OVA immunoglobulin (Ig) IgM, IgA, IgG, IgG1, IgG2 and IgG in piglets immunized with 0.05 mg OVA/CpG + MP relative to saline control animals. Thus, a single oral exposure at birth to a combined soluble and particulate OVA vaccine including adjuvants can circumvent induction of oral tolerance which impacts response to i.p. vaccination in later life. Further, piglets gavaged with 0.05 mg OVA/CpG + MP generated significant anti-OVA IgG and IgG1 titres in lung compared to saline control piglets but results were comparable to titres measured in parenteral control piglets. Peripheral blood mononuclear cells (PBMCs) ex vivo-stimulated with OVA showed markedly decreased production of IL-10 cytokine after 72 hours relative to animal-matched cells incubated with media alone. No production of IFN-γ was observed from any groups.

Conclusion

Newborn piglets gavaged with low dose soluble and particulate OVA plus CpG ODN and polyphosphazene adjuvants produced antigen-specific antibodies in serum and lung after systemic re-exposure in later life. These data indicate circumvention of oral tolerance but not induction of oral immunity.

The challenges in developing effective canine infectious respiratory disease vaccines

Objectives

Canine infectious respiratory disease (CIRD) is a disease of multifactorial aetiology, where multiple pathogens act sequentially or synergistically to cause disease. It is common within large dog populations, such as those in re‐homing or training kennels. Vaccines are vital in its management of CIRD, but they often fail to prevent disease. Recently, a number of novel pathogens have been identified in CIRD outbreaks and represent new targets for vaccination.

Key findings

Innate immune responses provide a vital first line of defence against the infectious agents involved in the development of CIRD. Once breeched, adaptive mucosal immunity is necessary to prevent infection and limit spread. Current vaccines target only a few of the agents involved in CIRD. Evidence, from the limited amount of published data, indicates that although vaccinating against these agents reduces infection rates, duration of shedding and severity of disease, it does not induce sterilising immunity; and this has important consequences for the management of the disease, and the future of CIRD vaccine development.

Summary

In the process of considering the development of novel CIRD vaccines, this paper focuses on the immunological mechanisms that provide protection for the respiratory tract, the current recommendations for canine vaccination, and the challenges surrounding existing CIRD vaccines, and their future development.

Light and electron microscopic study of the eyelids, conjunctiva-associated lymphoid tissue and lacrimal gland in Bilgorajska Goose (Anser anser)

Normal structure of the accessory organs of the eye is essential for normal eye physiology. Among the most important accessory organs of the eye are the eyelids, the conjunctiva-associated lymphoid tissue (CALT) and the lacrimal gland (LG). The aim of this study was to demonstrate the histological structure of the eyelids and LG by histochemical and ultrastructural analysis. The study was performed on 13 adult female Bilgorajska geese. Eyelid samples were stained with the Alcian blue (AB pH 2.5) and periodic acid-Schiff (PAS) methods. Staining methods used for LG were AB pH 2.5, aldehyde fuchsin (AF), PAS and Hale's dialysed iron (HDI). Within the connective tissue of the eyelids, well-developed, diffuse, CALT follicles were observed, mostly under the conjunctival epithelium. Numerous lymphocytes were present within loose connective tissue. Staining of the eyelids with the PAS method demonstrated the presence of goblet cells of a mucous nature, and AB pH 2.5 staining indicated the presence of sulfated acid mucopolysaccharides. PAS staining of LG revealed the presence of secretory cells containing weakly PAS-positive granules. All epithelial cells of the corpus glandulae and the duct systems reacted positively to AB pH 2.5. HDI staining detected the presence of carboxylated acid mucopolysaccharides. Transmission electron microscopy investigations revealed two types of secretory epithelial cells in LG. Both types of LG cells contained drop-like secretory vesicles of different sizes with low or high electron density in cytoplasm, as well as small and large lipid vacuoles, and numerous small primary lysosomes.

Nanocarriers: a versatile approach for mucosal vaccine delivery

Infectious agents generally use mucosal surfaces as entry port to the body thereby necessitating the need of development of mucosal vaccine as vaccination is important for disease avoidance and suppression. Vaccination through mucosal route is a promising strategy to elicit efficient immune response as parentally administered vaccines induce poor mucosal immunity in general. Safety, economy and stability are highly desired with vaccines and this can be achieved with use of delivery cargos. This review focuses on challenges related with mucosal vaccines and use of nanocarriers as suitable cargos to cater the antigen effectively to the desired site. The review also includes different factors which are to be considered regarding the performance of the nanocarriers and clinical status of these systems.

Effects of synbiotics injected in ovo on regulation of immune-related gene expression in adult chickens

OBJECTIVE

To determine immunomodulatory effects of synbiotics administered in ovo on immune-related gene expression in adult chickens.

ANIMALS

30 Green-legged Partridgelike chickens.

PROCEDURES

On incubation day 12, eggs were injected with 3 synbiotics (Lactococcus lactis subsp lactis IBB SL1 with raffinose family oligosaccharides [RFOs; S1], Lactococcus lactis subsp cremoris IBB SC1 with RFOs [S2], and Lactobacillus acidophilus and Streptococcus faecium with lactose [S3]). Control eggs were injected with RFOs prebiotic or saline (0.9% NaCl) solution. Gene expression of 6 cytokines (interleukin [IL]-4, IL-6, IL-12p40, IL-18, interferon [IFN]-β, and IFN-γ) and 1 chemokine (IL-8) was analyzed in the cecal tonsils and spleen of 6-week-old chickens by means of reverse transcription quantitative PCR assays.

RESULTS

Gene expression for IL-4, IL-6, IFN-β, and IL-18 was significantly upregulated in the spleen of chickens in groups S2 and S3. In contrast, IL-12 expression was downregulated in group S2 and IFN-γ expression was downregulated in group S3. Expression of IL-8 did not change in chickens treated with synbiotics in ovo. Gene expression of all cytokines, except for IL-18, was downregulated in cecal tonsils.

CONCLUSIONS AND CLINICAL RELEVANCE

In ovo administration of synbiotics activated the immune system in adult chickens. The intestinal immune system (cecal tonsils) had downregulation of expression for the cytokines evaluated, which indicated an increase in oral tolerance, whereas in the peripheral part of the immune system (spleen), expression of IL-4 and IL-6 was upregulated. Evaluation of immune-related gene expression patterns may be useful when monitoring the effectiveness of synbiotic selection with respect to immunobiotic properties.

Polymer nanotechnology based approaches in mucosal vaccine delivery: challenges and opportunities

Mucosal sites serve as the main portal for the entry of pathogens and thus immunization through mucosal routes can greatly improve the immunity. Researchers are continuously exploring the vaccination strategies to engender protective mucosal immune responses. Unearthing of mucosal adjuvants, that are safe and effective, is enhancing the magnitude and quality of the protective immune response. Use of nanotechnology based polymeric nanocarrier systems which encapsulate vaccine components for protection of sensitive payload, incorporate mucosal adjuvants to maximize the immune responses and target the mucosal immune system is a key strategy to improve the effectiveness of mucosal vaccines. These advances promise to accelerate the development and testing of new mucosal vaccines against many human diseases. This review focuses on the need for the development of nanocarrier based mucosal vaccines with emphases on the polymeric nanoparticles, their clinical status and future perspectives. This review focuses on the need and new insights for the development of nanoarchitecture governed mucosal vaccination with emphases on the various polymeric nanoparticles, their clinical status and future perspectives.

Mechanistic links between gut microbial community dynamics, microbial functions and metabolic health

Gut microbes comprise a high density, biologically active community that lies at the interface of an animal with its nutritional environment. Consequently their activity profoundly influences many aspects of the physiology and metabolism of the host animal. A range of microbial structural components and metabolites directly interact with host intestinal cells and tissues to influence nutrient uptake and epithelial health. Endocrine, neuronal and lymphoid cells in the gut also integrate signals from these microbial factors to influence systemic responses. Dysregulation of these host-microbe interactions is now recognised as a major risk factor in the development of metabolic dysfunction. This is a two-way process and understanding the factors that tip host-microbiome homeostasis over to dysbiosis requires greater appreciation of the host feedbacks that contribute to regulation of microbial community composition. To date, numerous studies have employed taxonomic profiling approaches to explore the links between microbial composition and host outcomes (especially obesity and its comorbidities), but inconsistent host-microbe associations have been reported. Available data indicates multiple factors have contributed to discrepancies between studies. These include the high level of functional redundancy in host-microbiome interactions combined with individual variation in microbiome composition; differences in study design, diet composition and host system between studies; and inherent limitations to the resolution of rRNA-based community profiling. Accounting for these factors allows for recognition of the common microbial and host factors driving community composition and development of dysbiosis on high fat diets. New therapeutic intervention options are now emerging.

A single, low dose oral antigen exposure in newborn piglets primes mucosal immunity if administered with CpG oligodeoxynucleotides and polyphosphazene adjuvants

By definition, soluble antigens ingested orally trigger mucosal tolerance such that any subsequent re-exposure by a systemic route results in suppression of immunity. We propose that antigens introduced in extreme early life can readily traverse the gut wall and therefore circumvent induction of mucosal tolerance and instead induce immunity. Piglets were drenched with low-doses of ovalbumin (OVA; 5mg or 0.05 mg) alone, OVA plus adjuvants (CpG oligodeoxynucleotides and PCEP polyphosphazene) or saline within 6h of birth. At 28 days of age, they were administered 10mg OVA plus 1:1 Montanide adjuvant (or saline) via the intraperitoneal (i.p.) route or via the oral route. Serum was obtained on day 28 and day 49 to measure OVA-specific antibodies titres. All piglets boosted orally with OVA plus Montanide, regardless of prior OVA exposure, failed to induce immunity. As expected, piglets drenched with saline but boosted via the i.p. route with OVA plus Montanide showed significant induction of anti-OVA IgA, IgG, IgG1 and IgG2 relative to saline control piglets. Newborn animals drenched with 5mg or 0.05 mg OVA failed to induce oral immunity. A second intramuscular injection in adulthood triggered immunity in the piglets that were drenched with 0.05 mg OVA and boosted initially by the i.p. route suggesting that some systemic lymphocytes were primed despite initial lack of induction of humoral immunity. In contrast, piglets orally immunized with 5mg or 0.05 mg OVA plus adjuvants resulted in significant induction of anti-OVA IgA (5mg only), IgM, IgG, IgG1 and IgG2 in serum relative to saline control piglets as well as significant induction of anti-OVA IgA, IgM (5mg only) IgG, IgG1 (5mg only) or IgG2 relative to piglets drenched with OVA alone. These data clearly show that the response was sensitive to the oral vaccine components and was not simply a response to the i.p. immunization at day 28. This work demonstrates that newborn piglets respond to oral antigens with immunity if re-exposure to the antigen occurs via a systemic route and if adjuvants are included with the oral vaccine administered at birth. These results should be further explored to establish whether early life oral vaccination can be exploited to protect this susceptible population against infectious diseases.

Messenger RNA (mRNA) nanoparticle tumour vaccination

Use of mRNA-based vaccines for tumour immunotherapy has gained increasing attention in recent years. A growing number of studies applying nanomedicine concepts to mRNA tumour vaccination show that the mRNA delivered in nanoparticle format can generate a more robust immune response. Advances in the past decade have deepened our understanding of gene delivery barriers, mRNA's biological stability and immunological properties, and support the notion for engineering innovations tailored towards a more efficient mRNA nanoparticle vaccine delivery system. In this review we will first examine the suitability of mRNA for engineering manipulations, followed by discussion of a model framework that highlights the barriers to a robust anti-tumour immunity mediated by mRNA encapsulated in nanoparticles. Finally, by consolidating existing literature on mRNA nanoparticle tumour vaccination within the context of this framework, we aim to identify bottlenecks that can be addressed by future nanoengineering research.

Tonsils of the soft palate do not mediate the response of pigs to oral vaccination with heat-inactivated Mycobacterium bovis

Mycobacterium bovis causes animal tuberculosis (TB) in cattle, humans, and other mammalian species, including pigs. The goal of this study was to experimentally assess the responses of pigs with and without a history of tonsillectomy to oral vaccination with heat-inactivated M. bovis and challenge with a virulent M. bovis field strain, to compare pig and wild boar responses using the same vaccination model as previously used in the Eurasian wild boar (Sus scrofa), to evaluate the use of several enzyme-linked immunosorbent assays (ELISAs) and lateral flow tests for in vivo TB diagnosis in pigs, and to verify if these tests are influenced by oral vaccination with inactivated M. bovis. At necropsy, the lesion and culture scores were 20% to 43% higher in the controls than those in the vaccinated pigs. Massive M. bovis growth from thoracic tissue samples was observed in 4 out of 9 controls but in none of the 10 vaccinated pigs. No effect of the presence or absence of tonsils was observed on these scores, suggesting that tonsils are not involved in the protective response to this vaccine in pigs. The serum antibody levels increased significantly only after challenge. At necropsy, the estimated sensitivities of the ELISAs and dual path platform (DPP) assays ranged from 89% to 94%. In the oral mucosa, no differences in gene expression were observed in the control group between the pigs with and without tonsils. In the vaccinated group, the mRNA levels for chemokine (C-C motif) receptor 7 (CCR7), interferon beta (IFN-β), and methylmalonyl coenzyme A mutase (MUT) were higher in pigs with tonsils. Complement component 3 mRNA levels in peripheral blood mononuclear cells (PBMC) increased with vaccination and decreased after M. bovis challenge. This information is relevant for pig production in regions that are endemic for M. bovis and for TB vaccine research.

Intranasal mRNA nanoparticle vaccination induces prophylactic and therapeutic anti-tumor immunity

Direct in vivo administration of messenger RNA (mRNA) delivered in both naked and nanoparticle formats are actively investigated because the use of dendritic cells transfected ex vivo with mRNA for cancer therapy is expensive and needs significant infrastructure. Notably, intravenous and subcutaneous injections are the only routes of administration tested for mRNA nanoparticle tumor vaccination. In this report, we demonstrate that tumor immunity can be achieved via nasal administration of mRNA. Mice nasally immunized with mRNA delivered in nanoparticle format demonstrate delayed tumor progression in both prophylactic and therapeutic immunization models. The observed tumor immunity correlates with splenic antigen-specific CD8+ T cells and is achieved only when mRNA is delivered in nanoparticle but not in naked format. In conclusion, we demonstrate, as a proof-of-concept, a non-invasive approach to mRNA tumor vaccination, increasing its potential as a broadly applicable and off-the-shelf therapy for cancer treatment.

IL-1α and complement cooperate in triggering local neutrophilic inflammation in response to adenovirus and eliminating virus-containing cells

Inflammation is a highly coordinated host response to infection, injury, or cell stress. In most instances, the inflammatory response is pro-survival and is aimed at restoring physiological tissue homeostasis and eliminating invading pathogens, although exuberant inflammation can lead to tissue damage and death. Intravascular injection of adenovirus (Ad) results in virus accumulation in resident tissue macrophages that trigger activation of CXCL1 and CXCL2 chemokines via the IL-1α-IL-1RI signaling pathway. However, the mechanistic role and functional significance of this pathway in orchestrating cellular inflammatory responses to the virus in vivo remain unclear. Resident metallophilic macrophages expressing macrophage receptor with collagenous structure (MARCO⁺) in the splenic marginal zone (MZ) play the principal role in trapping Ad from the blood. Here we show that intravascular Ad administration leads to the rapid recruitment of Ly-6G⁺7/4⁺ polymorphonuclear leukocytes (PMNs) in the splenic MZ, the anatomical compartment that remains free of PMNs when these cells are purged from the bone marrow via a non-inflammatory stimulus. Furthermore, PMN recruitment in the splenic MZ resulted in elimination of virus-containing cells. IL-1α-IL-1RI signaling is only partially responsible for PMN recruitment in the MZ and requires CXCR2, but not CXCR1 signaling. We further found reduced recruitment of PMNs in the splenic MZ in complement C3-deficient mice, and that pre-treatment of IL-1α-deficient, but not wild-type mice, with complement inhibitor CR2-Crry (inhibits all complement pathways at C3 activation) or CR2-fH (inhibits only the alternative complement activation pathway) prior to Ad infection, abrogates PMN recruitment to the MZ and prevents elimination of MARCO⁺ macrophages from the spleen. Collectively, our study reveals a non-redundant role of the molecular factors of innate immunity – the chemokine-activating IL-1α-IL-1RI-CXCR2 axis and complement – in orchestrating local inflammation and functional cooperation of PMNs and resident macrophages in the splenic MZ, which collectively contribute to limiting disseminated pathogen spread via elimination of virus-containing cells.

Adenovirus (Ad) induces a potent activation of pro-inflammatory cytokines and chemokines upon interaction with tissue macrophages in vivo. However, critical factors affecting cellular inflammatory responses to Ad and their functional significance remain unclear. Here we show that in the model of disseminated infection, intravenous Ad administration leads to a rapid release of pro-inflammatory Ly-6G⁺7/4⁺ leukocytes (PMNs) from the bone marrow into the blood. PMNs enter into peripheral tissues and, in the case of spleen, are accumulated in proximity to the virus-containing MARCO⁺ macrophages within the splenic marginal zone (MZ). Mechanistic dissection of molecular queues that guide PMN migration reveals that CXCL1 and CXCL2 chemokines are only partially responsible for CXCR2-dependent PMN recruitment into the splenic MZ. We further found that complement cooperates with IL-1α-IL-1RI-CXCR2 signaling pathways in recruitment of PMNs to the splenic MZ, which results in elimination of virus-containing MARCO⁺ macrophages from the spleen. Administration of complement-blocking CR2-Crry or CR2-fH proteins into IL-1α-deficient, but not wild-type, mice prevents PMN accumulation in the splenic MZ and elimination of virus-containing macrophages from the spleen. Our study defines the functional significance of molecular and cellular host defense mechanisms that cooperate in eliminating virus-containing cells in the model of acute disseminated Ad infection.

Lymph drainage from the ovine tonsils: an anatomical study of the tonsillar lymph vessels

Although the tonsils of sheep have gained much attention during the last decade, only few data are available on their lymph vessel architecture. Tonsillar lymph vessels are immunologically important as they form the efferent routes for locally activated immune cells to reach the draining lymph nodes. To gain insight into the tonsillar lymph drainage in the sheep, Indian ink and a casting polymer were injected into the interstitium of the five tonsils present in the heads of slaughtered sheep. This enabled us to determine the draining lymph node and to examine the microscopic organization of lymph vessels using light and scanning electron microscopy. No lymph vessels were observed within the tonsillar lymphoid follicles. The corrosion casts demonstrated that the lymphoid follicles are surrounded by numerous sacculated lymph sinuses that drain into a dense interfollicular lymph vessel network. From here, the lymph flows into single small lymph vessels that in turn drain into larger lymph vessels extending towards the medial retropharyngeal lymph node. The presented results can be valuable for immunological studies, for example during oral or intranasal vaccine development.

Peculiar composition of epithelial cells in follicle-associated intestinal crypts of Peyer's patches in the rat small intestine

The epithelial cell composition was investigated in the follicle-associated intestinal crypt (FAIC) of rat Peyer’s patches. The epithelium of the FAIC mainly consisted of columnar epithelial cells, goblet cells and Paneth cells. The characteristics of secretory granules in Paneth cells and goblet cells of both the FAIC and ordinary intestinal crypts (IC) were almost the same in periodic acid-Schiff (PAS) reaction, Alcian blue (AB) staining and the immunohistochemical detection of lysozymes and soluble phospholipase A2. Both goblet cells and Paneth cells were markedly less frequent on the follicular sides than on the anti-follicular sides of the FAIC. Goblet cells were also markedly less frequent in the follicle-associated epithelium (FAE) than in the ordinary intestinal villi (IV). Indigenous bacteria were more frequently adhered to FAE than to follicle-associated intestinal villi or IV. These findings suggest that the host defense against indigenous bacteria is inhibited on the follicular sides of FAIC, which might contribute to the preferential settlement of indigenous bacteria on the FAE; they also suggest that differentiation into secretory cells is inhibited in the epithelium of the follicular sides of FAIC, so that differentiation into M cells might be admitted in the FAE of rat Peyer’s patches. Furthermore, intermediate cells possessing characteristics of both Paneth cells and goblet cells were rarely found in the FAIC, but not in the IC. This finding suggests that the manner of differentiation into Paneth cells in the FAIC differs from that in the IC.

Selection of an aptamer against mouse GP2 by SELEX

Microfold (M) cells are intestinal epithelial cells specialized for sampling and transport of luminal antigens to gut-associated lymphoid tissue for initiation of both mucosal and systemic immune responses. Therefore, M-cell targeted vaccination has the potential to be a better immunization strategy. Glycoprotein 2 (GP2), an antigen uptake receptor for FimH(+) bacteria on M cells, can be a good target for this purpose. Aptamers are oligonucleotides that bind to a variety of target molecules with high specificity and affinity. Together with its low toxic feature, aptamers serves as a tool of molecular-targeted delivery. In this study, we used Systematic Evolution of Ligands by EXponential enrichment (SELEX) to isolate aptamers specific to murine GP2 (mGP2). After ten rounds of SELEX, eleven different aptamer sequences were selected. Among them, the most frequently appeared sequence (~60%) were aptamer NO. 1 (Apt1), and the second most (~7%) were aptamer NO. 5 (Apt5). In vitro binding experiment confirmed that only Apt1 and Apt5 specifically bound to mGP2 among eleven aptamers initially selected. Apt1 showed the strongest affinity with mGP2, with the Kd value of 110±2.6 nM evaluated by BIACORE. Binding assays with mutants of Apt1 suggest that, in addition to the loop structure, the nucleotide sequence, AAAUA, in the loop is important for binding to mGP2. Furthermore, this aptamer was able to bind to mGP2 expressed on the cell surface. These results suggest that this mGP2-specific aptamer could serve as a valuable tool for testing M-cell-targeted vaccine delivery in the murine model system.

Oral antigen exposure in extreme early life in lambs influences the magnitude of the immune response which can be generated in later life

BACKGROUND

Previous investigations in newborn lambs determined that adenovirus-mediated expression of antigen to a localized region of the gut induced antigen-specific mucosal and systemic immunity. These experiments were limited in that the localized region of the gut to which antigen was introduced was sterile and the influence of colostrum on the antigen was not assessed but they do suggest that mucosal vaccines may be an effective vaccination strategy to protect neonatal lambs. We propose that persistent oral antigen exposure introduced in extreme early life can induce immunity in lambs, despite the presence of commensal bacteria and colostrum.

RESULTS

To test this hypothesis, conventionally raised newborn lambs (n = 4 per group) were gavaged with ovalbumin (OVA) starting the day after birth for either a single day (2.27 g), every day for 3 days (0.23 g/day), or every day for 3 days then every second day until nine days of age (0.023 g/day). Lambs gavaged with OVA for 3 to 9 days developed significant serum anti-OVA IgG titres (p < 0.05), but not IgA titres, relative to control lambs (n = 4) after 3 and 4 weeks. At 4 weeks of age, lambs were immunized with OVA in Incomplete Freund's Adjuvant via intraperitoneal (i.p.) injection then lambs were euthanized at 7 weeks. Serum anti-OVA IgG titres were further augmented after i.p. immunization indicating immunity persisted and tolerance was not induced. Serum IgA titres remained low regardless of treatment. It is known that i.p. priming of sheep with antigen in Freund's complete adjuvant leads to an enhanced number of IgA and IgG antibody containing cells in the respiratory mucosa (Immunology 53(2):375-384, 1984). Lambs gavaged with a single bolus of 2.27 g OVA prior to i.p. immunization showed very low titres of anti-OVA IgA in the lung lavage. These data suggest that a single, high dose exposure to OVA can promote tolerance which impacts response to systemic vaccination in later life. Lambs gavaged with 0.023 g OVA for 9 days (Group C) generated significant anti-OVA IgA titres in lung (p < 0.001) compared to negative control lambs but no additive effect was observed compared to parenteral control lambs. When splenocytes were re-stimulated with OVA ex vivo, all groups failed to show increased lymphocyte proliferation or interferon (IFN)-γ production relative to the parenteral control group.

CONCLUSIONS

In agreement with our hypothesis, persistent low dose antigen exposure primes humoral antibody production in serum in conventionally raised newborn lambs. In contrast, a single high dose bolus of antigen triggered oral tolerance which negatively impacted the quality and magnitude of the immune response to i.p. immunization in later life. These tangential responses are important as they indicate that the dose and/or repeated oral exposure to antigen, such as that which may be found in the neonate's environment, may promote immunity or alternatively it may negatively impact responses to parenteral vaccination.

Site-specific immunophenotyping of keloid disease demonstrates immune upregulation and the presence of lymphoid aggregates

BACKGROUND

Keloid disease (KD) is a common fibroproliferative disorder of unknown aetiology. T cells and macrophages are increased in KD and are thought to contribute to its pathogenesis. However, while a link between inflammation and fibrotic disorders is well known for other disorders, it remains undetermined in KD.

OBJECTIVES

Systematically to immunophenotype the inflammatory infiltrate of KD in situ in a site-specific manner, and to compare this with normal skin and scar tissue.

METHODS

Sixty-eight keloid cases were screened for the presence of all three (intralesional, perilesional and extralesional) keloid-associated specific tissue sites. Subsequently, a complete set of 25 keloid biopsies (from different patients) was compared with normal skin (n = 11) and normal scar (n = 11) samples and subjected to systematic, site-specific quantitative immunohistomorphometry and histochemistry, using a range of immunological markers of B cells, T cells, macrophages, mast cells (MCs) and Langerhans cells.

RESULTS

T cells, B cells, degranulated and mature MCs (coexpressing OX40 ligand) and alternative macrophages (M2) were all significantly increased in intralesional and perilesional KD sites compared with normal skin and scar tissue (P < 0·05). Additionally, 10 of 68 KD cases (15%) showed the presence of distinctive lymphoid aggregates, which resembled mucosa-associated lymphoid tissue (MALT).

CONCLUSIONS

The increased number and activity of MCs and M2 may implicate inflammation in the fibrotic process in KD. The distinct KD-associated lymphoid aggregate resembles MALT, for which we propose the term 'keloid-associated lymphoid tissue' (KALT). It may perpetuate inflammatory stimuli that promote KD growth. KALT, MCs and M2 are promising novel targets for future KD therapy.

Clear evidence of carcinogenic activity by a whole-leaf extract of Aloe barbadensis miller (aloe vera) in F344/N rats

Aloe barbadensis Miller (Aloe vera) is an herbal remedy promoted to treat a variety of illnesses; however, only limited data are available on the safety of this dietary supplement. Drinking water exposure of F344/N rats and B6C3F1 mice to an Aloe vera whole-leaf extract (1, 2, and 3%) for 13 weeks resulted in goblet cell hyperplasia of the large intestine in both species. Based upon this observation, 2-year drinking water studies were conducted to assess the carcinogenic potential of an Aloe vera whole-leaf extract when administered to F344/N rats (48 per sex per group) at 0.5, 1, and 1.5%, and B6C3F1 mice (48 per sex per group) at 1, 2, and 3%. Compared with controls, survival was decreased in the 1.5% dose group of female rats. Treatment-related neoplasms and nonneoplastic lesions in both species were confined primarily to the large intestine. Incidences of adenomas and/or carcinomas of the ileo-cecal and cecal-colic junction, cecum, and ascending and transverse colon were significantly higher than controls in male and female rats in the 1 and 1.5% dose groups. There were no neoplasms of the large intestine in mice or in the 0 or 0.5% dose groups of rats. Increased incidences of mucosa hyperplasia of the large intestine were observed in F344/N rats, and increased incidences of goblet cell hyperplasia of the large intestine occurred in B6C3F1 mice. These results indicate that Aloe vera whole-leaf extract is an intestinal irritant in F344/N rats and B6C3F1 mice and a carcinogen of the large intestine in F344/N rats.

Low dose antigen exposure for a finite period in newborn rats prevents induction of mucosal tolerance

Background

In adult rats, initial exposure to antigens by a mucosal route triggers tolerance such that any subsequent re-exposure, even by a systemic route, results in suppression of immunity. The newborn’s gut is semi-permeable for a finite period to allow maternal antibodies to enter the newborn’s circulation. We propose that antigens introduced in extreme early life can readily traverse the gut wall and therefore circumvent induction of mucosal tolerance.

Methodology/Principle Findings

Rat pups were gavaged with low-doses of ovalbumin (OVA; oral exposure group) or saline (parenteral control group) every second day for several weeks followed by an intraperitoneal (i.p.) injection at 1 month of age. When gavage was initiated the day after birth, newborn oral exposure pups responded with significantly higher anti-OVA IgA, IgM, IgG2a, and IgG1 titres in their serum and anti-OVA IgA, IgG2a and IgG1 titres in their lungs compared to negative control pups. Oral exposure alone failed to induce immunity. Pups exposed to the same treatment regimen starting at 14 days of age showed induction of mucosal tolerance after i.p. immunization. Newborn oral exposure groups subjected to secondary i.p. immunization responded with significantly increased humoral immunity in lung and sera suggesting that once antigen-specific mucosal tolerance if circumvented, it persists. Lymphocytes derived from mesenteric lymph node cells re-simulated with OVA ex vivo, from newborn oral exposure pups exposed to secondary immunization produced significantly higher IFN-γ expression and lymphocyte proliferation relative to control pups indicating prevention of tolerance in the cell-mediated immune system.

Conclusions/Significance

This work demonstrates that newborns may be uniquely qualified to prevent induction of mucosal tolerance to oral antigens. These results should be further explored to establish whether prevention of tolerance by early life oral vaccination can be exploited to prime for mucosal as well as systemic immunity and thus protect this susceptible population against infectious diseases.

Organizer and regulatory role of colonic isolated lymphoid follicles in inflammation

Gut-associated lymphoid tissue (GALT) is supposed to play an integral role in the organization of colonic repair mechanisms. Majority of the GALT is composed of isolated and aggregated lymphoid follicles distributed throughout the intestines. These lymphoid follicles, including Peyer's patches of the small, and isolated lymphoid follicles (ILFs) of both the small and large intestines, are composed of a specialised follicle associated epithelium overlying a subepithelial dome containing numerous dendritic cells, macrophages, T and B cells. Within inflammatory conditions the number, the diameter and the density of ILFs are increasing. Follicles are involved not just in immune surveillance, but their presence is also indispensable for normal colonic mucosal regeneration. Regarding mucosal repair the relation of ILFs to bone marrow derived stem cells, follicular dendritic cells, subepithelial myofibroblasts and crypt formations, and the putative organizer role of ILFs have not been clarified yet.

Evidence of a true pharyngeal tonsil in birds: a novel lymphoid organ in Dromaius novaehollandiae and Struthio camelus (Palaeognathae)

BACKGROUND

Tonsils are secondary lymphoid organs located in the naso- and oropharynx of most mammalian species. Most tonsils are characterised by crypts surrounded by dense lymphoid tissue. However, tonsils without crypts have also been recognised. Gut-associated lymphoid tissue (GALT), although not well-organised and lacking tonsillar crypts, is abundant in the avian oropharynx and has been referred to as the "pharyngeal tonsil". In this context the pharyngeal folds present in the oropharynx of ratites have erroneously been named the pharyngeal tonsils. This study distinguishes between the different types and arrangements of lymphoid tissue in the pharyngeal region of D. novaehollandiae and S. camelus and demonstrates that both species possess a true pharyngeal tonsil which fits the classical definition of tonsils in mammals.

RESULTS

The pharyngeal tonsil (Tonsilla pharyngea) of D. novaehollandiae was located on the dorsal free surface of the pharyngeal folds and covered by a small caudo-lateral extension of the folds whereas in S. camelus the tonsil was similarly located on the dorsal surface of the pharyngeal folds but was positioned retropharyngeally and encapsulated by loose connective tissue. The pharyngeal tonsil in both species was composed of lymph nodules, inter-nodular lymphoid tissue, mucus glands, crypts and intervening connective tissue septa. In S. camelus a shallow tonsillar sinus was present. Aggregated lymph nodules and inter-nodular lymphoid tissue was associated with the mucus glands on the ventral surface of the pharyngeal folds in both species and represented the Lymphonoduli pharyngeales. Similar lymphoid tissue, but more densely packed and situated directly below the epithelium, was present on the dorsal, free surface of the pharyngeal folds and represented a small, non-follicular tonsil.

CONCLUSIONS

The follicular pharyngeal tonsils in D. novaehollandiae and S. camelus are distinct from the pharyngeal folds in these species and perfectly fit the classical mammalian definition of pharyngeal tonsils. The presence of a true pharyngeal tonsil differentiates these two ratite species from other known avian species where similar structures have not been described. The pharyngeal tonsils in these ratites may pose a suitable and easily accessible site for immune response surveillance as indicated by swelling and inflammation of the tonsillar tissue and pharyngeal folds. This would be facilitated by the fact that the heads of these commercially slaughtered ratites are discarded, thus sampling at these sites would not result in financial losses.

Strategies for intranasal delivery of vaccines

The vast majority of human pathogens colonize and invade at the mucosal surfaces. Preventing infection at these sites via mucosally active vaccines is a promising and rational approach for vaccine development. However, it is only recently that the stimulation of local immunity at the mucosal surfaces has become a primary objective in addition to inducing systemic immunity. This review describes vaccine formulations designed for mucosal delivery to the nasal-associated lymphoid tissue, via intranasal administration. The association of antigens with mucosal adjuvants and delivery systems is emphasised.

Enhanced histopathology of the immune system: a review and update

Enhanced histopathology (EH) of the immune system is a tool that the pathologist can use to assist in the detection of lymphoid organ lesions when evaluating a suspected immunomodulatory test article within a subchronic study or as a component of a more comprehensive, tiered approach to immunotoxicity testing. There are three primary points to consider when performing EH: (1) each lymphoid organ has separate compartments that support specific immune functions; (2) these compartments should be evaluated individually; and (3) semiquantitative descriptive rather than interpretive terminology should be used to characterize any changes. Enhanced histopathology is a screening tool that should be used in conjunction with study data including clinical signs, gross changes, body weight, spleen and thymus weights, other organ or tissue changes, and clinical pathology. Points to consider include appropriate tissue collection, sectioning, and staining; lesion grading; and diligent comparison with concurrent controls. The value of EH of lymphoid organs is to aid in the identification of target cell type, changes in cell production and cell death, changes in cellular trafficking and recirculation, and determination of mechanism of action.

New insights in mucosal vaccine development

Mucosal surfaces are the major entrance for infectious pathogens and therefore mucosal immune responses serve as a first line of defence. Most current immunization procedures are obtained by parenteral injection and only few vaccines are administered by mucosal route, because of its low efficiency. However, targeting of mucosal compartments to induce protective immunity at both mucosal sites and systemic level represents a great challenge. Major efforts are made to develop new mucosal candidate vaccines by selecting appropriate antigens with high immunogenicity, designing new mucosal routes of administration and selecting immune-stimulatory adjuvant molecules. The aim of mucosal vaccines is to induce broad potent protective immunity by specific neutralizing antibodies at mucosal surfaces and by induction of cellular immunity. Moreover, an efficient mucosal vaccine would make immunization procedures easier and be better suited for mass administration. This review focuses on contemporary developments of mucosal vaccination approaches using different routes of administration.

The tonsils revisited: review of the anatomical localization and histological characteristics of the tonsils of domestic and laboratory animals

This paper gives an overview of the anatomical localization and histological characteristics of the tonsils that are present in ten conventional domestic animal species, including the sheep, goat, ox, pig, horse, dog, cat, rabbit, rat, and pigeon. Anatomical macrographs and histological images of the tonsils are shown. Six tonsils can be present in domestic animals, that is, the lingual, palatine, paraepiglottic, pharyngeal, and tubal tonsils and the tonsil of the soft palate. Only in the sheep and goat, all six tonsils are present. Proper tonsils are absent in the rat, and pigeon. In the rabbit, only the palatine tonsils can be noticed, whereas the pig does not present palatine tonsils. The paraepiglottic tonsils lack in the ox, horse, and dog. In addition, the dog and cat are devoid of the tubal tonsil and the tonsil of the soft palate.

Internet and Print Resources to Facilitate Pathology Analysis When Phenotyping Genetically Engineered Rodents

Genetically engineered mice and rats are increasingly used as models for exploring disease progression and mechanisms. The full spectrum of anatomic, biochemical, and functional changes that develop in novel, genetically engineered mouse and rat lines must be cataloged before predictions regarding the significance of the mutation may be extrapolated to diseases in other vertebrate species, including humans. A growing list of reference materials, including books, journal articles, and websites, has been produced in the last 2 decades to assist researchers in phenotyping newly engineered rodent lines. This compilation provides an extensive register of materials related to the pathology component of rodent phenotypic analysis. In this article, the authors annotate the resources they use most often, to allow for quick determination of their relevance to research projects.

Distribution, organization and innervation of gastric MALT in conventional piglet

Mucosa-associated lymphoid tissue (MALT) is the initial inductive site for mucosal immunity. It is present in the different layers of the mucosal wall and consists of organized lymphoid tissue which may occur as isolated or aggregated lymphoid follicles (LFs) and interfollicular areas. It is present in many organs, including the pig stomach. Gastric MALT has been intensely studied in experimentally infected pigs but few data are available in healthy, non-gnotobiotic or germ-free animals. In the present study we described the gastric MALT in conventional piglets in the cardiac mucosa of the gastric diverticulum, in the pyloric mucosa, and in the sites of transition from cardiac to oxyntic and from cardiac to pyloric mucosa by means of histological and immunohistochemical stains. The majority of LFs were located in the cardiac mucosa and in the transition from the cardiac to the oxyntic mucosa. Here the LFs were mainly located in the submucosa and reached the mucosa; we called these submucosal lymphoid follicles (SLFs). In the pyloric mucosa and in the transition sites from the cardiac to the pyloric mucosa, LFs were located in the mucosa; we called these mucosal lymphoid follicles (MLFs). In SLFs, a compartmental organization of T and B lymphocytes was present; by contrast, in the MLFs, the T and B cells were intermingled, suggesting the possibility of different roles for the two types of follicles. In the epithelium overlying the lymphoid tissue, numerous T lymphocytes and some cells immunoreactive to cytokeratin-18 were observed. Following the application of the fluorescent tracer DiI into the SLFs of the diverticulum, enteric neurones located in the submucosal plexus were labelled, confirming the interplay between the immune and the enteric nervous system.

Topical and mucosal liposomes for vaccine delivery

Mucosal (and in minor extent transcutanous) stimulation can induce local or distant mucosa secretory IgA. Liposomes and other vesicles as mucosal and transcutaneous adjuvants are attractive alternatives to parenteral vaccination. Liposomes can be massively produced under good manufacturing practices and stored for long periods, at high antigen/vesicle mass ratios. However, their uptake by antigen-presenting cells (APC) at the inductive sites remains as a major challenge. As neurotoxicity is a major concern in intranasal delivery, complexes between archaeosomes and calcium as well as cationic liposomes complexed with plasmids encoding for antigenic proteins could safely elicit secretory and systemic antigen-specific immune responses. Oral bilosomes generate intense immune responses that remain to be tested against challenge, but the admixing with toxins or derivatives is mandatory to reduce the amount of antigen. Most of the current experimental designs, however, underestimate the mucus blanket 100- to 1000-fold thicker than a 100-nm diameter liposome, which has first to be penetrated to access the underlying M cells. Overall, designing mucoadhesive chemoenzymatic resistant liposomes, or selectively targeted to M cells, has produced less relevant results than tailoring the liposomes to make them mucus penetrating. Opposing, the nearly 10 µm thickness stratum corneum interposed between liposomes and underlying APC can be surpassed by ultradeformable liposomes (UDL), with lipid matrices that penetrate up to the limit with the viable epidermis. UDL made of phospholipids and detergents, proved to be better transfection agents than conventional liposomes and niosomes, without the toxicity of ethosomes, in the absence of classical immunomodulators.

Terminology of the tonsils

Many terms used for referring to tonsillar structures are applied in immunological research. However, in many cases, the use of these terms is not in compliance with official veterinary anatomical nomenclature. This is partly attributable to ambiguous descriptions present in conventional anatomical textbooks. This study gives an overview of pertaining controversial terms and promotes the official anatomical terminology applicable to the tonsils, to enhance the unequivocal transfer of knowledge generated during immunological research.

Degenerating processes identified by electron microscopic immunocytochemical methods

The application of electron microscopic immunolabeling techniques to the identification and analysis of degenerating processes in neural tissue has greatly enhanced the ability of researchers to examine apoptosis and other degenerative disease mechanisms. This is particularly true for the early stages of such mechanisms. Traditionally, degenerating processes could only be identified at the ultrastructural level after significant cellular atrophy had occurred, when subcellular detail was obscured and synaptic relationships altered. Using immunocytochemical labeling procedures, degenerating neural and glial processes are first identified through the use of antibodies directed against a variety of degenerative markers, such as proapoptotic effectors (i.e., cytoplasmic cytochrome c), pathological components (i.e., beta amyloid deposits), or inflammatory agents (i.e., Iba1). Both the subcellular distribution of the marker within the process and the relationship of the labeled process to surrounding elements can then be carefully characterized. The information obtained can be further refined through the use of dual immunolabeling, which can provide additional data on the phenotype of the degenerating process and inputs to the process.

Targeted drug delivery to lymphocytes: a route to site-specific immunomodulation?

Lymphocytes are central to the progression of autoimmune disease, transplant rejection, leukemia, lymphoma and lymphocyte-resident viral diseases such as HIV/AIDs. Strategies to target drug treatments to lymphocytes, therefore, represent an opportunity to enhance therapeutic outcomes in disease states where many current treatment regimes are incompletely effective and promote significant toxicities. Here we demonstrate that highly lipophilic drug candidates that preferentially access the intestinal lymphatics after oral administration show significantly enhanced access to lymphocytes leading to improved immunomodulatory activity. When coadministered with such drugs, lipids enhance lymphocyte targeting via a three tiered action: promotion of drug absorption from the gastrointestinal tract, enhancement of lymphatic drug transport and stimulation of lymphocyte recruitment into the lymphatics. This strategy has been exemplified using a highly lipophilic immunosuppressant (JWH015) where coadministration with selected lipids led to significant increases in lymphatic transport, lymphocyte targeting and IL-4 and IL-10 expression in CD4+ and CD8+ lymphocytes after ex vivo mitogen stimulation. In contrast, administration of a 2.5-fold higher dose of JWH015 in a formulation that did not stimulate lymph transport had no effect on antiinflammatory cytokine levels, in spite of equivalent drug exposure in the blood. The current data suggest that complementary drug design and delivery strategies that combine highly lipophilic, lymphotropic drug candidates with lymph-directing formulations provide enhanced selectivity, potency and therapeutic potential for drug candidates with lymphocyte associated targets.

Effects of restraint stress on NALT structure and nasal IgA levels

The effects of stress on the mucosal immune responses in inflammatory disorders of the gut, as well as on salivary and intestinal IgA levels are well known. However, its effects on the structure and function of the NALT have not yet been reported, and are examined in the present study. Balb/c mice were submitted to restraint stress for 3h per day during 4 or 8d. The immunohistochemistry and flow cytometric analysis revealed that repeated restraint stress (4 and 8d) decreased the percentage, compared to the control group, of CD3(+) and CD4(+) T cells, without affecting the percentage of CD8(+) T cells or B220(+) cells (B cells). The numbers of IELs (CD4(+) and CD8(+) T cells) were lower at 4d of stress and higher at 8d. IgA(+) cells in NALT and nasal IgA levels showed a similar pattern, being significantly lower at 4d of stress and significantly higher at 8d. In summary, repeated restraint stress altered the distribution and number of lymphocytes and IgA(+) cells in nasal mucosa, probably due to changes in norepinephrine and corticosterone levels.

Adjuvant effect of Bacillus firmus on the expression of cytokines and toll-like receptors in mouse nasopharynx-associated lymphoid tissue (NALT) after intranasal immunization with inactivated influenza virus type A

Due to the persisting threat of development of new highly pathogenic influenza A subtypes, a mucosal vaccination which would induce a potent and cross-protective reaction is desirable. We succeeded in mucosal immunization of mice with an inactivated influenza A virus by using delipidated Bacillus firmus (DBF) as adjuvant. The mechanism of adjuvant effect was followed in NALT by comparing the response after intranasal immunization by inactivated influenza virus type A (H1N1) alone, adjuvant alone (DBF), or by a mixture of virus+DBF. Expression of selected gene groups was tested via qPCR at 7 different time-points: cytokines (IL-2, IFN-γ, IL-4, IL-6, and IL-10), type I interferons (IFN-α4, IFN-α11, IFN-α12, and IFN-β), toll-like receptors (TLR2, TLR3, TLR7, and TLR9), iNOS and CCR7. Intranasally administered DBF and the mixture of virus+DBF induced an elevated expression of IFN-γ, IL-6 and IL-10 cytokines, type I interferons, iNOS, and pDC markers in NALT. Multimarker qPCR data was analyzed by relative quantification and by principal component analysis. DBF has been shown to be a very efficient adjuvant for the stimulation of innate immunity after IN immunization. DBF accelerated, increased, and prolonged the antiviral response.

Nanotechnology solutions for mucosal immunization

The current prevalence of infectious diseases in many developing regions of the world is a serious burden, impacting both the general health as well as economic growth of these communities. Additionally, treatment with conventional medication becomes increasingly challenging due to emergence of new and drug resistant strains jeopardizing the progress made in recent years towards control and elimination of certain types of infectious diseases. Thus, from a public health perspective, prevention such as through immunization by vaccination, which has proven to be most effective, might be the best alternative to prevent and combat infectious diseases in these regions. To achieve this, development of wide-scale immunization programs become necessary including vaccines that can easily and widely be distributed, stored and administered. Mucosal vaccines offer great potential since they can be administered via oral or intranasal delivery route which does not require trained personnel, avoids the use of needles and improves overall patient compliance and acceptance. However, it necessitates the implementation of specific immunization strategies to improve their efficacy. Application of nanotechnology to design and create particle mediated delivery systems that can efficiently encapsulate vaccine components for protection of the sensitive payload, target the mucosal immune system and incorporate mucosal adjuvants maximizing immune response is key strategy to improve the effectiveness of mucosal vaccines.