Intranasal immunization with protein-linked phosphorylcholine protects mice against a lethal intranasal challenge with streptococcus pneumoniae

Broad specificity of monoclonal IgA (TEPC15-IgA) for enteric bacteria via phosphorylcholine-mediated interaction

Immunoglobulin A (IgA) is notable for its broad specificity toward multiple bacteria. Phosphorylcholine (PC) plays a role in the infection of pathogenic bacteria carrying PC and in the induction of IgA responses in the host immune system. The commercially available mouse monoclonal IgA, TEPC15-IgA, is a distinctive antibody with specificity for PC, warranting further exploration of its response to PC-bearing enteric bacteria. In this study, using 17 different enteric bacteria, including 3 aerobic and 14 anerobic bacteria that could be cultured in vitro, we confirmed that TEPC15-IgA recognizes 4 bacterial species: Lactobacillus taiwanensis, Limosilactobacillus frumenti, Streptococcus infantis, and Escherichia coli, although reactivity varied. Interestingly, TEPC15-IgA did not react with four of six Lactobacillus species used. Moreover, distinct target molecules associated with PC in L. taiwanensis and L. frumenti were evident, differing in molecular weight. These findings suggest that the natural generation of PC-specific IgA could prevent PC-mediated infections and potentially facilitate the formation of a microflora rich in indigenous bacteria with PC, particularly in the gastrointestinal tract.

Cecal Metabolomic Fingerprint of Unscathed Rats: Does It Reflect the Good Response to a Provocative Decompression?

On one side, decompression sickness (DCS) with neurological disorders lead to a reshuffle of the cecal metabolome of rats. On the other side, there is also a specific and different metabolomic signature in the cecum of a strain of DCS-resistant rats, that are not exposed to hyperbaric protocol. We decide to study a conventional strain of rats that resist to an accident-provoking hyperbaric exposure, and we hypothesize that the metabolomic signature put forward may correspond to a physiological response adapted to the stress induced by diving. The aim is to verify and characterize whether the cecal compounds of rats resistant to the provocative dive have a cecal metabolomic signature different from those who do not dive. 35 asymptomatic diver rats are selected to be compared to 21 rats non-exposed to the hyperbaric protocol. Because our aim is essentially to study the differences in the cecal metabolome associated with the hyperbaric exposure, about half of the rats are fed soy and the other half of maize in order to better rule out the effect of the diet itself. Lower levels of IL-1β and glutathione peroxidase (GPX) activity are registered in blood of diving rats. No blood cell mobilization is noted. Conventional and ChemRICH approaches help the metabolomic interpretation of the 185 chemical compounds analyzed in the cecal content. Statistical analysis show a panel of 102 compounds diet related. 19 are in common with the hyperbaric protocol effect. Expression of 25 compounds has changed in the cecal metabolome of rats resistant to the provocative dive suggesting an alteration of biliary acids metabolism, most likely through actions on gut microbiota. There seem to be also weak changes in allocations dedicated to various energy pathways, including hormonal reshuffle. Some of the metabolites may also have a role in regulating inflammation, while some may be consumed for the benefit of oxidative stress management.

Diverse Mechanisms of Protective Anti-Pneumococcal Antibodies

The gram-positive bacterium Streptococcus pneumoniae is a leading cause of pneumonia, otitis media, septicemia, and meningitis in children and adults. Current prevention and treatment efforts are primarily pneumococcal conjugate vaccines that target the bacterial capsule polysaccharide, as well as antibiotics for pathogen clearance. While these methods have been enormously effective at disease prevention and treatment, there has been an emergence of non-vaccine serotypes, termed serotype replacement, and increasing antibiotic resistance among these serotypes. To combat S. pneumoniae, the immune system must deploy an arsenal of antimicrobial functions. However, S. pneumoniae has evolved a repertoire of evasion techniques and is able to modulate the host immune system. Antibodies are a key component of pneumococcal immunity, targeting both the capsule polysaccharide and protein antigens on the surface of the bacterium. These antibodies have been shown to play a variety of roles including increasing opsonophagocytic activity, enzymatic and toxin neutralization, reducing bacterial adherence, and altering bacterial gene expression. In this review, we describe targets of anti-pneumococcal antibodies and describe antibody functions and effectiveness against S. pneumoniae.

The mucosal immune system of the upper respiratory tract and recent progress in mucosal vaccines

The mucosal immune system prevents microorganism invasion through mucosal surfaces and consists of inductive and effector sites. Nasopharynx-associated lymphoid tissue (NALT) functions as an inductive site, inducing mucosal immune responses in the upper respiratory tract. It follows that intranasal vaccines may prevent upper respiratory infections. To induce and enhance the immune response by administering inactivated antigens intranasally, mucosal adjuvants have been developed, including mutant cholera toxin and cationic cholesteryl pullulan nanogel, which do not accumulate in the central nervous system. Moreover, multivalent pneumococcal polysaccharide conjugate vaccines are used to prevent invasive pneumococcal infections and otitis media, although they only provide moderate protection against acute otitis media because non-vaccine serotypes of Streptococcus pneumoniae and Haemophilus influenzae also cause this infection. To address this problem, pneumococcal surface protein A of S. pneumoniae and P6 of H. influenzae are used as broad-spectrum vaccine antigens. Alternatively, phosphorylcholine (PC) is present in the cell walls of both gram-positive and gram-negative bacteria and induces immune responses through antigenic activity. The significant effects of PC as a mucosal vaccine have been demonstrated through intranasal and sublingual immunization in mice. Furthermore, intranasal administration of PC reverses increases in IgE levels and prevents allergic rhinitis. After immunization with pneumococcal polysaccharide conjugate vaccine, intranasal immunization with PC boosts immune responses to vaccine strains and to PC itself. Thus, PC may be useful as a mucosal vaccine to prevent upper respiratory infections and allergic rhinitis, and it could be used as a booster to the currently used pneumococcal vaccine as it protects against non-vaccine strains.

Cecal metabolome fingerprint in a rat model of decompression sickness with neurological disorders

Massive bubble formation after diving can lead to decompression sickness (DCS), which can result in neurological disorders. We demonstrated that hydrogen production from intestinal fermentation could exacerbate DCS in rats fed with a standard diet. The aim of this study is to identify a fecal metabolomic signature that may result from the effects of a provocative hyperbaric exposure. The fecal metabolome was studied in two groups of rats previously fed with maize or soy in order to account for diet effects. 64 animals, weighing 379.0_20.2 g on the day of the dive, were exposed to the hyperbaric protocol. The rats were separated into two groups: 32 fed with maize (Div MAIZE) and 32 fed with soy (Div SOY). Gut fermentation before the dive was estimated by measuring exhaled hydrogen. Following hyperbaric exposure, we assessed for signs of DCS. Blood was analyzed to assay inflammatory cytokines. Conventional and ChemRICH approaches helped the metabolomic interpretation of the cecal content. The effect of the diet is very marked at the metabolomic level, a little less in the blood tests, without this appearing strictly in the clinic status. Nevertheless, 37 of the 184 metabolites analyzed are linked to clinical status. 35 over-expressed compounds let suggest less intestinal absorption, possibly accompanied by an alteration of the gut microbial community, in DCS. The decrease in another metabolite suggests hepatic impairment. This spectral difference of the ceca metabolomes deserves to be studied in order to check if it corresponds to functional microbial particularities.

Progress in mucosal immunization for protection against pneumococcal pneumonia

Introduction: Lower respiratory tract infections are the fourth cause of death worldwide and pneumococcus is the leading cause of pneumonia. Nonetheless, existing pneumococcal vaccines are less effective against pneumonia than invasive diseases and serotype replacement is a major concern. Protein antigens could induce serotype-independent protection, and mucosal immunization could offer local and systemic immune responses and induce protection against pneumococcal colonization and lung infection. Areas covered: Immunity induced in the experimental human pneumococcal carriage model, approaches to address the physiological barriers to mucosal immunization and improve delivery of the vaccine antigens, different strategies already tested for pneumococcal mucosal vaccination, including live recombinant bacteria, nanoparticles, bacterium-like particles, and nanogels as well as, nasal, pulmonary, sublingual and oral routes of vaccination. Expert opinion: The most promising delivery systems are based on nanoparticles, bacterial-like particles or nanogels, which possess greater immunogenicity than the antigen alone and are considered safer than approaches based on living cells or toxoids. These particles can protect the antigen from degradation, eliminating the refrigeration need during storage and allowing the manufacture of dry powder formulations. They can also increase antigen uptake, control release of antigen and trigger innate immune responses.

Role of phosphorylcholine in Streptococcus pneumoniae and nontypeable Haemophilus influenzae adherence to epithelial cells

OBJECTIVE

Phosphorylcholine (PC) is a structural component of Streptococcus pneumoniae (Spn) and nontypeable Haemophilus influenzae (NTHi), and is known to be associated with adherence through the platelet activating factor receptor (PAF-R). Furthermore, high PC expression is considered to be involved in Spn and NTHi virulence. In this study, we examined the influence of PC expression on the adherence of Spn and NTHi to epithelial cells in order to clarify the potential effectiveness of a vaccine targeting PC.

METHODS

Twenty-seven strains of Spn and twenty-two strains of NTHi were used, cultured overnight, and PC expression was evaluated by fluorescence activated cell sorting; the strains were divided into two groups: PC low expression (PC-low) and PC high expression (PC-high) groups. Bacterial adherence was then examined using Detroit 562 cells and BALB/c mice. Bacterial invasion was then examined in Detroit 562 cells.

RESULTS

The adherence of Spn and NTHi and invasion of NTHi in the PC-high group was significantly reduced by pretreatment with a monoclonal anti-PC antibody (TEPC-15), PAF-R antagonist (ABT-491), and PC-keyhole limpet hemocyanin (PC-KLH). However, such findings were not observed in the PC-low group.

CONCLUSION

The present study suggests that PC is involved in the mucosal adhesion of Spn and NTHi, and the mucosal invasion of NTHi with PC-high strains, but not PC-low strains. These results suggest that a PC-targeting mucosal vaccine only affects PC-high Spn and NTHi strains and does not disturb commensal bacterial flora in the upper respiratory tract, which comprises nonpathogenic PC-low bacteria.

Intranasal immunization with phosphorylcholine suppresses allergic rhinitis in mice

OBJECTIVES/HYPOTHESIS

Intranasal immunization with phosphorylcholine (PC) is known to reduce immunoglobulin (Ig)E production. However, its effects on the occurrence of allergic rhinitis (AR) are unknown. This study was performed to evaluate the effects of PC-keyhole limpet hemocyanin (PC-KLH) and to examine the effects on the occurrence of AR in a murine model of AR.

STUDY DESIGN

In vivo study using an animal model.

METHODS

Forty-five female BALB/c mice were divided into three groups; those pretreated with intranasal administration of PC-KLH followed by intraperitoneal sensitization and nasal challenge with ovalbumin (OVA) (group A), those untreated with PC-KLH followed by sensitization and nasal challenge with OVA (group B), and those untreated with PC-KLH or OVA as controls (group C). Nasal symptoms, allergic inflammation in the nasal mucosa, OVA specific IgE production, and cytokine profile were compared among those three groups. Dendritic cells (DCs) were isolated from splenic cells and PC-KLH-stimulated interleukin (IL)-12p40 production was measured.

RESULTS

The mice pretreated with PC-KLH showed lower allergic nasal symptoms and inflammation compared to untreated mice. The levels of total IgE and OVA-specific IgE in serum, and IL-4 production by nasal and splenic CD4⁺ T cells were significantly reduced by PC-KLH pretreatment. Furthermore, IL-12p40 production by DCs was induced by PC-KLH in a dose-dependent manner.

CONCLUSIONS

Intranasal administration of PC-KLH suppressed allergic inflammation in nasal mucosa and antigen-specific IgE production by downregulating Th2-type immune response. Intranasal immunization with PC might be useful to prevent AR and upper airway bacterial infection.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:E234-E240, 2018.

Microbial modulation of host immunity with the small molecule phosphorylcholine

All microorganisms dependent on persistence in a host for survival rely on either hiding from or modulating host responses to infection. The small molecule phosphorylcholine, or choline phosphate (ChoP), is used for both of these purposes by a wide array of bacterial and parasitic microbes. While the mechanisms underlying ChoP acquisition and expression are diverse, a unifying theme is the use of ChoP to reduce the immune response to infection, creating an advantage for ChoP-expressing microorganisms. In this minireview, we discuss several benefits of ChoP expression during infection as well as how the immune system fights back against ChoP-expressing pathogens.

Characterization of immune responses following intranasal immunization with the Mycobacterium bovis CFP-10 protein expressed by attenuated Salmonella typhimurium

Culture filtrate protein 10 (CFP-10) from Mycobacterium bovis or Mycobacterium tuberculosis (MTB) is an immunodominant T-cell antigen expressed during the early stages of infection. Because lungs are most commonly associated with primary M. bovis infections, specific immunity at this site is desirable for protection. Therefore, in this study, immune responses generated in mouse lung, spleen and Peyer's patches were examined following intranasal (i.n.) immunization with Salmonella typhimurium- expressing CFP-10. Cells harvested from the lungs and Peyer's patches of immunized mice and then stimulated with CFP-10 produced significant levels of IFN-γ and these mice developed elevated serum IgG and lung IgA anti-CFP-10 responses, suggesting that this approach induced potent anti-CFP-10 mucosal immunity. Our study demonstrates that i.n. administration of CFP-10 expressed by S. typhimurium represents an effective way to induce efficient immune response to M. bovis antigen.

The role of B cells in lupus pathogenesis

Autoantibodies clearly contribute to tissue inflammation in systemic lupus erythematosus. In order to therapeutically target B cells making pathogenic autoantibodies, it is necessary to identify their phenotype. It is also important to understand the defects in B cell repertoire selection that permit pathogenic autoreactive B cells to enter the immunocompetent B cell repertoire. We present the data that both marginal zone and follicular B cells can produce pathogenic autoantibodies. Moreover, we discuss how B cell survival and maturation are regulated centrally prior to antigen activation and in the periphery after antigen activation to form the repertoire that generates the spectrum of circulating antibodies.

Mechanisms in the serotype-independent pneumococcal immunity induced in mice by intranasal vaccination with the cell wall polysaccharide

We previously reported that cell wall polysaccharide (CWPS) given to mice intranasally with adjuvant induces serotype-independent immunity to pneumococci. Some strains make CWPS with one phosphocholine group (CWPS/1), but most express two per tetrasaccharide repeat unit (CWPS/2). Here, CWPS/1 and CWPS/2 were equally protective against colonization by CWPS/2-type pneumococci, but the related Streptococcus mitis polymer lacking phosphocholine was non-protective. Previously the protection was shown to be CD4+T cell-dependent, abrogated by antiserum to interleukin (IL)-17A, and demonstrable in antibody-defective mice. Here, CWPS failed to protect IL-17A receptor knockout mice, further indicating IL-17A-dependence. When commercial CWPS/1 was size-fractionated preparatively, the larger exceeded the smaller molecules in their capacity to prime for IL-17A responses, and only the larger protected against pneumococcal colonization. However, a CWPS-tetanus toxoid conjugate - despite raising high titers of phosphocholine antibody - was non-protective, confirming the irrelevance of humoral immunity in this model. The results strengthen the concept that IL-17A-mediated T cell immunity is inducible by zwitterionic polysaccharides with sufficient chain length to provide coiled secondary structure. Coupling CWPS to protein, which paradoxically prevents protection, may occlude this regular linear conformation. We suggest that mucosal immunization with CWPS primes T(H)17 cells, which - upon contact with the phosphocholine of colonizing pneumococci - elaborate IL-17A, enhancing phagocytosis.

Animal models of Streptococcus pneumoniae disease

SUMMARY

Streptococcus pneumoniae is a colonizer of human nasopharynx, but it is also an important pathogen responsible for high morbidity, high mortality, numerous disabilities, and high health costs throughout the world. Major diseases caused by S. pneumoniae are otitis media, pneumonia, sepsis, and meningitis. Despite the availability of antibiotics and vaccines, pneumococcal infections still have high mortality rates, especially in risk groups. For this reason, there is an exceptionally extensive research effort worldwide to better understand the diseases caused by the pneumococcus, with the aim of developing improved therapeutics and vaccines. Animal experimentation is an essential tool to study the pathogenesis of infectious diseases and test novel drugs and vaccines. This article reviews both historical and innovative laboratory pneumococcal animal models that have vastly added to knowledge of (i) mechanisms of infection, pathogenesis, and immunity; (ii) efficacies of antimicrobials; and (iii) screening of vaccine candidates. A comprehensive description of the techniques applied to induce disease is provided, the advantages and limitations of mouse, rat, and rabbit models used to mimic pneumonia, sepsis, and meningitis are discussed, and a section on otitis media models is also included. The choice of appropriate animal models for in vivo studies is a key element for improved understanding of pneumococcal disease.

Intranasal immunization with phosphorylcholine induces antigen specific mucosal and systemic immune responses in mice

Phosphorylcholine (PC) is a structural component of a wide variety of pathogens including Streptococcus pneumoniae and Haemophilus influenzae, and anti-PC immune responses are known to protect mice against invasive bacterial diseases. The present study tested the capability of PC as an intranasal plurispecific vaccine against upper airway infections. BALB/c mice immunized with intranasal PC-keyhole limpet hemocyanin (KLH) plus cholera toxin (CT) as a mucosal adjuvant showed increased PC-specific IgM in serum, IgA in nasal wash and saliva, and numbers of PC-specific nasal and splenic antibody producing cells. Enhanced production of IL-4 and IFN-gamma by CD4+ T cells indicated the participation of Th2- and Th1-type cells. Salivary IgA antibodies produced by intranasal immunization with PC-KLH plus CT reacted to most strains of S. pneumoniae and H. influenzae. Further we demonstrated that the clearance of S. pneumoniae and H. influenzae from the nasal tract was significantly enhanced by nasal immunization with PC-KLH and CT. Thus, intranasal vaccination to induce PC-specific immune responses might help to prevent upper airway infections caused by S. pneumoniae and H. influenzae.

Antibody-independent, interleukin-17A-mediated, cross-serotype immunity to pneumococci in mice immunized intranasally with the cell wall polysaccharide

Serotype-specific immunity to Streptococcus pneumoniae is conferred by antibodies to the capsular polysaccharides, which define the 90 known serotypes. Whether antibody to the species-common cell wall polysaccharide (C-Ps) is protective has been a matter of controversy. Here we show that C-Ps given intranasally with mucosal adjuvant increased the resistance of mice to experimental nasopharyngeal colonization by capsulated S. pneumoniae of serotype 6B. This immunity could be induced in mice congenitally lacking immunoglobulin but was dependent upon CD4+ T cells. Elimination of the charged amino group on the polymer backbone by N acetylation of C-Ps reduced the immunity, as did treatment of the mice with antibody to the cytokine interleukin-17A at the time of challenge, both consistent with the hypothesis of T-cell activation due to the zwitterionic motif of the polymer. C-Ps also protected in a model of fatal aspiration pneumonia by heavily capsulated serotype 3. These findings suggest a novel immunization strategy against S. pneumoniae.

Phosphorylcholine-carbohydrate-protein conjugates efficiently induce hapten-specific antibodies which recognize both Streptococcus pneumoniae and Neisseria meningitidis: a potential multitarget vaccine against respiratory infections

Phosphorylcholine (ChoP) is commonly expressed at the surface of pathogens of the respiratory tract, including Streptococcus pneumoniae and Neisseria meningitidis. We designed a synthetic hapten comprising ChoP and part of its native carrier structure in S. pneumoniae, i.e. N-acetyl-D-galactosamine (GalNAc). Protein conjugates of this hapten induced GalNAc-ChoP-specific antibodies which recognized ChoP on both S. pneumoniae and N. meningitidis. GalNAc-ChoP could therefore lead to the rational design of a novel multipurpose vaccine against respiratory infections.

Murine antibody response to intranasally administered enterotoxigenic Escherichia coli colonization factor CS6

Enterotoxigenic Escherichia coli (ETEC) is the most common cause of bacterial diarrhea worldwide and is an important cause of infant morbidity and mortality in developing nations. ETEC colonization factors (CF) are virulence determinants that appear to be protective antigens in humans and are the major target of vaccine efforts. One of the most prevalent CF, CS6, is expressed by about 30% of ETEC worldwide. This study was designed to compare the immunogenicity between encapsulated CS6 (CS6-PLG) and unencapsulated CS6. Recombinant CS6 was purified and encapsulated in biodegradable poly(DL-lactide-co-glycolide) (PLG) microspheres using current Good Manufacturing Practices (cGMP). CS6-PLG and CS6 were administered intranasally (IN) to BALB/c mice in three vaccinations 4 weeks apart. Enzyme linked immunosorbent assay (ELISA) was used to measure the anti-CS6 response in serum and mucosal secretions following each of the three inoculations. Mice vaccinated with two or three doses of CS6-PLG demonstrated a significantly greater rise in serum anti-CS6 IgG and mucosal IgA titer values than those immunized with two or three doses of CS6 alone. Three doses of CS6-PLG led to anti-CS6 serum IgG and mucosal IgA titer values 14-fold and 4.4-fold greater, respectively, than three doses of CS6 (P<0.02). IN administered CS6 to mice is safe and highly immunogenic either alone or when encapsulated in microspheres. PLG microsphere encapsulation of CS6 significantly augments the antibody response to that antigen when administered to a mucosal surface.

Biodegradable microparticles for the mucosal delivery of antibacterial and dietary antigens

Mucosal administration of antigen is known to be appropriate for vaccine purposes as well as tolerance induction. Biodegradable poly(DL-lactide-co-glycolide) (PLGA) microparticles were used to deliver both antibacterial phosphorylcholine (PC) and dietary antigen beta lactoglobulin (BLG) by mucosal route. In a first study, the protective immunity elicited by intragastric vaccination with PC encapsulated in microparticles was evaluated in a mouse model against intestinal infection by Salmonella typhimurium and pulmonary infection by Streptococcus pneumoniae. A significant rise in anti-PC immunoglobulin A (IgA) titers, as measured by an enzyme-linked immunosorbent assay, was observed in the intestinal secretions after oral immunization with PC-loaded microparticles compared with the titers of mice immunized with free PC-thyr or blank microparticles. This antibody response correlated with a highly significant resistance to oral challenge by S. typhimurium. IgA in pulmonary secretion were not able to protect against S. pneumoniae infection. BALB/c mice were, therefore, immunized intranasally (i.n.). Immunization was followed by a rise in anti-PC IgA and IgG titers in serum and in pulmonary secretions by both free and encapsulated PC-Thyr. The survival rates were 91 and 76% in the two groups of mice, respectively. In a second study and in order to prevent allergy against milk by inducing oral tolerance, one of the major allergenic milk protein, BLG was entrapped into microparticles. Oral administration of microparticles containing BLG reduced significantly (by 10000) the amount of protein necessary to decrease both specific anti BLG IgE and DTH response. These studies demonstrate the ability of microparticles to induce both mucosal immunity and oral tolerance.

Microparticles for intranasal immunization

Of the several routes available for mucosal immunization, the nasal route is particularly attractive because of ease of administration and the induction of potent immune responses, particularly in the respiratory and genitourinary tracts. However, adjuvants and delivery systems are required to enhance immune responses following nasal immunization. This review focuses on the use of microparticles as adjuvants and delivery systems for protein and DNA vaccines for nasal immunization. In particular we discuss our own work on poly(lactide co-glycolide) (PLG) microparticles with entrapped protein or adsorbed DNA as a vaccine delivery system. The possible mechanisms involved in the enhancement of immune responses through the use of DNA adsorbed onto PLG microparticles are also discussed.

Nasal vaccines

The nasal route for vaccination offers some important opportunities, especially for the prophylaxis of respiratory diseases. Vaccination via the respiratory tract is reviewed and the deposition and clearance of antigens in the deep lung and nose are described and contrasted. Lymphoid structures in the respiratory tract differ according to species; the rat and mouse have a well developed nose-associated lymphoid tissue, while in man, the structure known as Waldeyer's ring (that includes the tonsils), is important as an induction site. The immune response following intranasal administration can provide protection at the administration site and at various effector sites as part of the common mucosal immune system. A number of formulation considerations are important when designing novel systems for nasal administration as are physiological factors such as mucociliary clearance.