Immunogenicity of anti-Haemophilus influenzae type b CRM197 conjugate following mucosal vaccination with oligodeoxynucleotide containing immunostimulatory sequences as adjuvant

Systemic Activation of TLR3-Dependent TRIF Signaling Confers Host Defense against Gram-Negative Bacteria in the Intestine

Recognition of Gram-negative bacteria by toll-like receptor (TLR)4 induces MyD88 and TRIF mediated responses. We have shown that TRIF-dependent responses play an important role in intestinal defense against Gram-negative enteropathogens. In the current study, we examined underlying mechanisms of how systemic TRIF activation enhances intestinal immune defense against Gram-negative bacteria. First we confirmed that the protective effect of poly I:C against enteric infection of mice with Yersinia enterocolitica was dependent on TLR3-mediated TRIF signaling by using TLR3-deficient mice. This protection was unique in TRIF-dependent TLR signaling because systemic stimulation of mice with agonists for TLR2 (Pam3CSK4) or TLR5 (flagellin) did not reduce mortality on Y. enterocolitica infection. Systemic administration of poly I:C mobilized CD11c+, F4/80+, and Gr−1^hi cells from lamina propria and activated NK cells in the mesenteric lymph nodes (MLN) within 24 h. This innate immune cell rearrangement was type I IFN dependent and mediated through upregulation of TLR4 followed by CCR7 expression in these innate immune cells found in the intestinal mucosa. Poly I:C induced IFN-γ expression by NK cells in the MLN, which was mediated through type I IFNs and IL-12p40 from antigen presenting cells and consequent activation of STAT1 and STAT4 in NK cells. This formation of innate immunity significantly contributed to the elimination of bacteria in the MLN. Our results demonstrated an innate immune network in the intestine that can be established by systemic stimulation of TRIF, which provides a strong host defense against Gram-negative pathogens. The mechanism underlying TRIF-mediated protective immunity may be useful to develop novel therapies for enteric bacterial infection.

Enhancement of serum and mucosal immune responses to a Haemophilus influenzae Type B vaccine by intranasal delivery

Intranasal (i.n.) vaccination is potentially the most direct method for conveying upper respiratory and mucosal immunity to respiratory pathogens. However, for unclear reasons, vaccines introduced into the nasal sinuses often have lower efficacy than vaccines administered by the more frequently used parenteral routes. We examined i.n. vaccination in a mouse immune-response model with a commonly used Haemophilus influenzae type B vaccine (Hibv) composed of the polyribosylribitol phosphate (PRP) capsule antigen conjugated to tetanus toxoid. Intranasal vaccination with Hibv using a Toll-like receptor 4 (TLR4) agonist as an adjuvant significantly increased the levels of IgA specific for the PRP capsule antigen in blood serum, saliva, and mucosal secretion specimens. In contrast, control mice vaccinated transdermally (t.d.) with Hibv did not produce significant levels of PRP-specific IgA in the blood serum and saliva, and anti-PRP IgG was increased only in serum. The i.n. and t.d. vaccinations resulted in equivalent bactericidal antibody responses in blood serum, suggesting that vaccine-derived IgG is protective against infection. Elevated levels of IgG specific for the tetanus toxoid carrier protein were measured in nasal sinuses and vaginal secretions in mice vaccinated by either the t.d. or i.n. route. Tissue culture studies confirmed that the nasopharynx-associated lymphoid tissue (NALT) was at least one of the sources of PRP-specific IgA and carrier-specific IgG within the nasal sinuses. We conclude that i.n. vaccination aided by a TLR4 agonist results in robust immune responses to both the carrier protein and bacterial polysaccharide components of the Hibv.

TLR9 agonist CpG enhances protective nasal HSP60 peptide vaccine efficacy in experimental autoimmune arthritis

OBJECTIVES

Peptide-based immune tolerance induction is considered an attractive treatment option for autoimmune diseases. The authors have developed a novel method that can enhance the induction of protective peptide-specific T-cell responses, using a rat arthritis model. The authors focused on the Toll-like receptor 9 ligand CpG, which was shown to stimulate regulatory T-cell proliferation when added to plasmacytoid dendritic cells (pDC) using in-vitro cultures.

METHODS

The peptide used is a heat shock protein 60 epitope (p1) that elicits tolerogenic peptide-specific immune responses in human arthritis patients and was recently shown to have protective capacity as a bystander antigen in the rat adjuvant arthritis model. Rats were treated with three nasal doses of p1, CpG or a combination of p1 and CpG. Antigen-presenting cells were studied in nose-draining lymph nodes (mandibular lymph nodes; MLN) after nasal treatment, and T-cell responses were analysed in joint-draining lymph nodes after arthritis induction.

RESULTS

Nasal co-administration of p1/CpG significantly augmented the arthritis-protective effect of p1, while CpG treatment alone did not. Co-treatment of p1/CpG increased both the number and activation status of pDC in draining MLN, which was accompanied by amplified p1-specific T-cell proliferation and interleukin (IL)-10 production. During early arthritis, p1-specific IL-10 production was identified at the site of inflammation. P1 and p1/CpG-treated rats showed a greater amount of CD4+FoxP3+ regulatory T cells in the joint-draining lymph nodes, which correlated with lower arthritis scores.

CONCLUSIONS

These clinical and immunological data suggest the use of CpG as a potent adjuvant for mucosal peptide-specific immune therapy in arthritis.

Co-administration of attenuated Mycoplasma hyopneumoniae 168 strain with bacterial DNA enhances the local and systemic immune response after intranasal vaccination in pigs

Mycoplasma hyopneumoniae, the primary pathogen of enzootic pneumonia, occurs worldwide and causes major economic losses to the pig industry. M. hyopneumoniae infects pigs at mucosal surfaces of respiratory tract. The aim of the present study was to investigate if the protection rate against M. hyopneumoniae infection following intranasal immunization with attenuated M. hyopneumoniae 168 strain is improved by administration of bacterial DNA containing CpG motifs. Thirty pigs were immunized intranasally or intramuscularly and the levels of local respiratory tract and systemic immune responses were detected. The results showed that the number of intraepithelial lymphocytes in the tracheal fork, the levels of cytokine IL-6, and M. hyopneumoniae specific SIgA in local nasal cavity increased respectively after intranasal vaccination with the attenuated M. hyopneumoniae 168 strain alone. However, the levels of IL-10 and IFN-γ in local nasal cavity, the number of intraepithelial lymphocytes in trachea, CD4(+) and CD8(+) T lymphocytes in the lung and hilar lymph nodes, the specific IgG antibody level in serum on 35 day post immunization were all increased significantly after intranasal vaccination of the attenuated M. hyopneumoniae 168 strain adjuvanted with bacterial DNA. We concluded that intranasal administration of attenuated M. hyopneumoniae 168 strain adjuvanted with bacterial DNA may be effective in evoking the local cellular and humoral immune response in the respiratory tract and the systemic immune response. Intranasal vaccination will be effective in prevention of the transmission and prevalence of MPS.

CpG DNA: Trigger of Sepsis, Mediator of Protection, or Both?

Unmethylated CpG motifs are prevalent in bacterial but not vertebrate genomic DNAs and activate immune cells that express the TLR9 receptor. This triggers the production of reactive oxygen species and the secretion of proinflammatory cytokines and chemokines. Under some conditions these effects can result in the systemic inflammatory response syndrome. Under other conditions, the immune stimulatory effects of CpG motifs can protect against pathogen challenge and initiate prophylactic and therapeutic innate and adaptive immune responses.

Intranasal immunization with a recombinant truncated FimH adhesin adjuvanted with CpG oligodeoxynucleotides protects mice against uropathogenic Escherichia coli challenge

In this work, we assessed the efficacy of an experimental intranasal vaccine against urinary-tract infections. The vaccine contained a recombinant truncated FimH (rFimHt) adhesin plus CpG oligodeoxynucleotides. The efficacy of the vaccine was compared with that of an intramuscular vaccine that was formulated with the same immunogen plus Freund's adjuvant. Our results show that serum immunoglobulin G titers of vaccinated animals were similarly enhanced in both cases. However, the intranasal vaccine elicited higher vaginal-wash-specific immunoglobulin A titers against rFimHt than the intramuscular route. Both vaccines reduced the in vivo colonization of the bladder by uropathogenic Escherichia coli more than 100-fold in a murine cystitis model. Our results indicate that a recombinant truncated FimH adhesin plus CpG oligodeoxynucleotides is a suitable immunogenic combination that can contribute to the development of a highly efficacious urinary tract infection vaccine.

Kinetics of mouse antibody and lymphocyte responses during intranasal vaccination with a lipooligosaccharide-based conjugate vaccine

We investigated the kinetics of humoral immunity and its related cellular immune responses to intranasal (IN) immunization with a detoxified lipooligosaccharide (dLOS)-tetanus toxoid (TT) conjugate against nontypeable Haemophilus influenzae (NTHi) in mice. IN vaccination with dLOS-TT elicited high titers of LOS-specific IgA in nasal washes and IgG in sera during a course of 4 inoculations while high titers of TT-specific IgA and IgG were found in sera. A significant increase of LOS-specific IgA antibody forming cells (AFCs) was observed in nasopharyngeal-associated lymphoid tissue (NALT) and nasal passages. However, TT induced broad responses with higher numbers of IgA and IgG AFCs found in NALT and nasal passages, less but significant IgA AFCs in cervical lymphoid nodes (CLN), spleen, and lungs. Phenotypic analysis revealed a significant rise of total B220+ B-lymphocytes in NALT and CLN, particularly a rise in IgA+/IgM+ cells in the NALT after the immunization. The latter result was complied with a significant rise of IL-4 but not IFN-gamma positive CD4+ T-lymphocytes in NALT. Analysis of IgG antibody subclasses showed that an IgG1 response to both LOS and TT epitopes dominated in serum when compared to IgG2a. These kinetic antibody patterns and cellular responses may provide useful information regarding to effective mucosal vaccines against NTHi infections.

Mucosal immunization against hepatitis A: antibody responses are enhanced by co-administration of synthetic oligodeoxynucleotides and a novel cationic lipid

Hepatitis A caused by hepatitis A virus (HAV) transmitted by the fecal-oral route, results in considerable morbidity and economic loss. Mucosal immunization can be more effective than conventional injection at inducing both local and systemic immunity to HAV. Here we show that co-administration of killed HAV with synthetic oligodeoxynucleotides (ODNs) containing CpG sequences, and a novel polycationic sphingolipid (CCS)/cholesterol liposomal delivery system, markedly enhances the HAV-specific antibody response at the intestinal interface, particularly when delivered intrarectally or intranasally, to Balb/c mice at low HAV doses. A mucosally delivered, antigen-sparing HAV vaccine that is easily administered without specialized equipment or personnel, is an attractive alternative for facilitating mass immunization in hepatitis A outbreaks.

Mucosal adjuvants

Induction of immune responses following oral immunization is frequently dependent upon the co-administration of appropriate adjuvants that can initiate and support the transition from innate to adaptive immunity. The three bacterial products with the greatest potential to function as mucosal adjuvants are the ADP-ribosylating enterotoxins (cholera toxin and the heat-labile enterotoxin of Escherichia coli), synthetic oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG ODN), and monophosphoryl lipid A (MPL). The mechanism of adjuvanticity of the ADP-ribosylating enterotoxins is the subject of considerable debate. Our own view is that adjuvanticity is an outcome and not an event. It is likely that these molecules exert their adjuvant function by interacting with a variety of cell types, including epithelial cells, dendritic cells, macrophages, and possibly B- and T-lymphocytes. The adjuvant activities of CpG and MPL are due to several different effects they have on innate and adaptive immune responses and both MPL and CpG act through MyD88-dependent and -independent pathways. This presentation will summarize the probable mechanisms of action of these diverse mucosal adjuvants and discuss potential synergy between these molecules for use in conjunction with plant-derived vaccines.

A novel dry powder influenza vaccine and intranasal delivery technology: induction of systemic and mucosal immune responses in rats

Intranasal (i.n.) vaccination represents an attractive non-invasive alternative to needle-based injection and provides superior protection at mucosal surfaces. However, new formulations are needed to improve efficacy and reduce the refrigerated storage and distribution requirements associated with standard liquid vaccines. Here, we describe a powder formulation of whole inactivated influenza virus and a novel i.n. delivery platform. The powder-formulated vaccine elicited a significant serum antibody response in rats that was at least as strong as that provided by the liquid vaccine administered i.n. or via intramuscular (i.m.) injection. Significant nasal IgA responses were also observed solely after i.n. delivery. This study demonstrates for the first time the generation of potent nasal mucosal and systemic immune responses using an i.n. delivered influenza vaccine powder and suggests an alternative approach to vaccination against influenza and other infectious diseases.

Mucosal immunization against respiratory bacterial pathogens

Bacterial respiratory diseases remain a major cause of morbidity and mortality throughout the world. The young and the elderly are particularly susceptible to the pathogens that cause these diseases. Therapeutic approaches remain dependent upon antibiotics contributing to the persistent increases in antibiotic resistance. The main causes of respiratory disease discussed in this review are Mycobacterium tuberculosis, Corynebacterium diphtheriae, Bordatella pertussis, Streptococcus pneumoniae, non-typeable Haemophilus influenzae, Moraxella catarrhalis and Pseudomonas aeruginosa. All these organisms initiate disease at the mucosal surface of the respiratory tract and thus the efficacy of the host's response to infection needs to be optimal at this site. Vaccines available for diseases caused by many of these pathogens have limitations in accessibility or efficacy, highlighting the need for improvements in approaches and products. The most significant challenges in both therapy and prevention of disease induced by bacteria in the respiratory tract remain the development of non-injectable vaccines and delivery systems/immunization regimens that improve mucosal immunity.

Mucosal immunity: overcoming the barrier for induction of proximal responses

Vaccination represents one of the most efficacious and cost-effective medical interventions. It is the only medical intervention proven to eliminate disease at a global level. Many of the pathogens against which we most require adequate vaccines infect via the highly exposed mucosal surfaces. For this reason the mucosa is often considered the first, and sometimes only, line of defense. Therefore, responses that protect the local mucosa are vital. In this review, we first explore the immunological mechanisms that protect the mucosa. We then review the literature of mucosal vaccines within the principles of antigenic composition, dose, and danger, highlighting the need and niche for the next generation of mucosal vaccines.

Mucosal vaccination against encapsulated respiratory bacteria--new potentials for conjugate vaccines?

Polysaccharide (PS)-encapsulated bacteria such as Haemophilus influenzae type b (Hib), Streptococcus pneumoniae (pneumococcus), Neisseria meningitides (meningococcus) and group B streptococcus (GBS), cause a major proportion of disease in early childhood. Native PS vaccines are immunogenic and provide protection against disease in healthy adults but do not induce immunological memory. PSs are T-cell-independent antigens and do not elicit antibodies in infants and young children, but by conjugating PS to proteins they become T-cell dependent and immunogenic at an early age. Despite excellent efficacy of PS-protein conjugate vaccines against invasive disease, protection against mucosal infections such as pneumococcal otitis media has been less efficacious. Circulating PS-specific antibodies may protect against infections at mucosal sites, but mucosal immunoglobulin A antibodies may also contribute significantly to protection against mucosal infections. Mucosal immunization of experimental animals with conjugate vaccines against Hib, pneumococcus, meningococcus and GBS induces systemic and mucosal immune responses, which provide protection against carriage, otitis media and invasive disease in a variety of challenge models, providing new means for protection against encapsulated bacteria. In addition, mucosal immunization of neonatal mice with a pneumococcal conjugate and the nontoxic adjuvant LT-K63 has been superior to parenteral immunization in eliciting protective antibodies and PS-specific memory, and thus circumventing the limitations of antibody responses to PS that are responsible for enhanced susceptibility of neonates and infants to infections caused by encapsulated bacteria. Through T-cell dependent enhanced immunogenicity of PS-protein conjugate vaccines, mucosal immunization could be an attractive approach for early life immunization against encapsulated bacteria.

Mucosal adjuvants and anti-infection and anti-immunopathology vaccines based on cholera toxin, cholera toxin B subunit and CpG DNA

The mucosal immune system consists of an integrated network of lymphoid cells that work in concert with innate host factors to promote host defence. Mucosal immunization can be used both to protect the mucosal surfaces against colonization and invasion by microbial pathogens and to provide a means for immunological treatment of selected autoimmune, allergic or infectious-immunopathological disorders through the induction of antigen-specific tolerance. The development of mucosal vaccines, whether for prevention of infectious diseases or for oral tolerance immunotherapy, requires efficient antigen delivery and adjuvant systems. Significant progress has recently been made to generate partly or wholly detoxified derivatives of cholera toxin (including the completely nontoxic cholera toxin B subunit) and the closely related Escherichia coli heat-labile enterotoxin, with retained adjuvant activity. Cholera toxin B subunit is a protective component of a widely registered oral vaccine against cholera, and has proven to be a promising vector for either giving rise to anti-infective immunity or for inducing peripheral anti-inflammatory tolerance to chemically or genetically linked foreign antigens administered mucosally. Promising advances have also recently been made in the design of efficient mucosal adjuvants based on bacterial DNA that contains CpG-motifs and various imidazoquinoline compounds binding to different Toll-like receptors on mucosal antigen-presenting cells.