The role of Th1 and Th2 cells for mucosal IgA responses

Differential cytokine profiling and microbial species involved in cecal microbiota modulations in SPF chicks immunized with a dual vaccine against Salmonella Typhimurium infection

Salmonella Typhimurium (ST) infection in laying hens is a significant threat to public health and food safety. Host resistance against enteric pathogen invasion primarily relies on immunity and gut barrier integrity. This study applied the ST infection model and a dual live vaccine containing Salmonella Enteritidis (SE) strain Sm24/Rif12/Ssq and ST strain Nal2/Rif9/Rtt to investigate the cellular cytokine expression profiles and the differential community structure in the cecal microbiota of specific-pathogen-free (SPF) chicks and field-raised layers. The results showed that ST challenge significantly upregulated expressions of IL-1β in SPF chicks. Vaccination, on the other hand, led to an elevation in IFNγ expression and restrained IL-1β levels. In the group where vaccination preceded the ST challenge (S.STvc), heightened expressions of IL-1β, IL-6, IL-10, and IL-12β were observed, indicating active involvement of both humoral and cell-mediated immunity in the defense against ST. Regarding the cecal microbiota, the vaccine did not affect alpha diversity nor induce a significant shift in the microbial community. Conversely, ST infection significantly affected the alpha and beta diversity in the cecal microbiota, reducing beneficial commensal genera, such as Blautia and Subdoligranulum. MetagenomeSeq analysis reveals a significant increase in the relative abundance of Faecalibacterium prausnitzii in the groups (S.STvc and STvc) exhibiting protection against ST infection. LEfSe further demonstrated Faecalibacterium prausnitzii as the prominent biomarker within the cecal microbiota of SPF chicks and field layers demonstrating protection. Another biomarker identified in the S.STvc group, Eubacterium coprostanoligenes, displayed an antagonistic relationship with Faecalibacterium prausnitzii, suggesting the limited biological significance of the former in reducing cloacal shedding and tissue invasion. In conclusion, the application of AviPro Salmonella DUO vaccine stimulates host immunity and modulates cecal microbiota to defend against ST infection. Among the microbial modulations observed in SPF chicks and field layers with protection, Faecalibacterium prausnitzii emerges as a significant species in the ceca. Further research is warranted to elucidate its role in protecting layers against ST infection.

IL-4-secreting CD40L+ MAIT cells support antibody production in the peripheral blood of Heonch-Schönlein purpura patients

OBJECTIVE

Here, we explored the phenotype and function of MAIT cells in the peripheral blood of patients with HSP.

METHODS

Blood samples from HSP patients and HDs were assessed by flow cytometry and single-cell RNA sequencing to analyze the proportion, phenotype, and function of MAIT cells. Th-cytokines in the serum of HSP patients were analyzed by CBA. IgA in cocultured supernatant was detected by CBA to analyze antibody production by B cells.

RESULTS

The percentage of MAIT cells in HSP patients was significantly reduced compared with that in HDs. Genes related to T cell activation and effector were up-regulated in HSP MAIT cells, indicating a more activated phenotype. In addition, HSP MAIT cells displayed a Th2-like profile with the capacity to produce more IL-4 and IL-5, and IL-4 was correlated with IgA levels in the serum of HSP patients. Furthermore, CD40L was up-regulated in HSP MAIT cells, and CD40L+ MAIT cells showed an increased ability to produce IL-4 and to enhance IgA production by B cells.

CONCLUSION

Our data demonstrate that MAIT cells in HSP patients exhibit an activated phenotype. The enhanced IL-4 production and CD40L expression of MAIT cells in HSP patients could take part in the pathogenesis of HSP.

Oral immunization with attenuated Salmonella encoding an elastase elicits protective immunity against Trichinella spiralis infection

Elastase belongs to the serine protease family. Previous studies showed that Trichinella spiralis elastase (TsE) was highly expressed in intestinal infective larvae (IIL). Recombinant TsE (rTsE) promoted the larval intrusion of enteral epithelium cells (IECs), whereas anti-rTsE antibodies and siRNA impeded larval intrusion. Subcutaneous vaccination of mice with rTsE showed a partial protective immunity, suggesting that TsE might be a promising vaccine target against Trichinella infection. In this study, complete TsE cDNA sequence was cloned into pcDNA3.1, and the rTsE DNA was transformed into attenuated S. typhimurium strain ΔcyaSL1344. Oral vaccination of mice with TsE DNA elicited a systemic Th1/Th2/Treg mixed immune response and gut local mucosal sIgA response. Immunized mice exhibited a significant immune protection against T. spiralis larval challenge, as demonstrated by a 52.48% reduction of enteral adult worms and a 69.43% reduction of muscle larvae. The protection might be related to the TsE-induced production of intestinal mucus, specific anti-TsE sIgA and IgG, and secretion of IFN-γ, IL-2, IL-4 and IL-10, which protected gut mucosa from larval intrusion, suppressed worm development and impeded female reproduction. The results demonstrated that attenuated Salmonella-delivered TsE DNA vaccine provided a prospective strategy for the control of Trichinella infection in food animals.

Genetic background affects the mucosal SIgA levels, parasite burden, lung inflammation and susceptibility of male mice to Ascaris suum infection

Ascariasis is a neglected tropical disease, widespread in the world and causing important socioeconomic impacts. The presence of various stages of worm development in the pulmonary and intestinal mucosa induces a humoral and cellular immune response. However, although there is much evidence of the protective role of mucosal immunity against various pathogens, including helminthes, there is still a gap in the knowledge about the immune response and the mechanisms of action that are involved in protection against diseases, especially in the initial phase of ascariasis. Then, the aim of this study was to evaluate the kinetic aspects of the immune parasitological parameters in intestinal and pulmonary mucosa in male mice with early ascariasis. Therefore, two mice strains showed a different susceptibility to ascariasis (BALB/c and C57BL6/j), when experimentally infected with 2,500 infective eggs of Ascaris suum from time-point 0 and the immune parasitological parameters evaluated each two days after infection, during the period of 12 days. The results were suggestive of a synergetic action of intestinal and pulmonary SIgA contributing for the protection against early ascariasis by reducing the amount of migrating larval as well as the influx of leukocytes in the lung and the consequent impair of the pulmonary capacity.

Oral vaccination with attenuated Salmonella encoding the Trichinella spiralis 43-kDa protein elicits protective immunity in BALB/c mice

A vaccine against Trichinella spiralis infection is urgently needed to interrupt its transmission from domestic animals to humans. However, no vaccine against T. spiralis is currently available. Our previous study demonstrated that the use of the 43-kDa glycoprotein present in excretory-secretory (ES) proteins of muscle larvae (ML) as an intramuscular DNA vaccine led to a 52.1% protection rate against T. spiralis infection. Attenuated Salmonella strains have the advantage of eliciting mucosal immunity, which is important for controlling T. spiralis infections at the intestinal stage and can be provided as vaccines via oral or intranasal routes. Therefore, in this study, complete 43-kDa glycoprotein (Ts43) sequences of T. spiralis were cloned into the vector pYA3681, and the recombinant plasmid pYA3681-Ts43 was transformed into the attenuated Salmonella typhimurium strain χ11802. The results showed that oral vaccination of mice with attenuated Salmonella carrying the recombinant plasmid pYA3681-Ts43 induced an evident elevation of the local intestinal mucosal sIgA and serum IgG antibody responses. The flow cytometry results showed that the percentages of CD4⁺ T cells and secreted IFN-γ, IL-4, and IL-17A in CD4⁺ T cells were significantly increased in the spleen and mesenteric lymph node (MLN) lymphocytes of the vaccinated groups. In addition, increased levels of the IFN-γ, IL-4, and IL-17A cytokines were also observed in the serum of the immunized groups. The above immune response results in the immunized groups demonstrated that protective immunity was elicited in this study. Finally, vaccinated mice demonstrated a significant 45.9% reduction in ML burden after infection with T. spiralis. This study demonstrated that oral vaccination with Ts43 delivered by attenuated Salmonella elicited local and systemic concurrent Th1/Th2/Th17 immune responses and provided partial protection against T. spiralis infection in BALB/c mice. This is a prospective strategy for the prevention and control of trichinellosis.

Comparison of the mucosal adjuvanticities of two Toll-like receptor ligands for recombinant adenovirus-delivered African swine fever virus fusion antigens

The mucosal immunity plays an important role against African swine fever virus (ASFV) infection and the efficacy of mucosal vaccination is highly dependent on the adjuvant. However, the mucosal adjuvant for ASFV vaccination is poorly studied. Toll-like receptor (TLR) ligands such as the FlaB flagellin from Vibrio vulnificus and the heat shock protein 70 from Mycobacterium tuberculosis (mHsp70) hold a great promise as novel vaccine adjuvant. However, the mucosal adjuvanticities of such TLR ligands have not been studied in pigs. In this study, three recombinant Adenovirus (rAd) vectors, namely rAd-F1, rAd-FlaB-F1 and rAd-F1-Hsp70, were constructed by fusing the FlaB or mHsp70 to ASFV CD2v-p30-p54 fusion antigen. Western blotting showed that the three fusion proteins expressed in rAd-infected cells reacted positively with ASFV antibodies. After intranasal immunization of pigs with the three rAd vectors, the antigen-specific IgG antibodies were detectable from day 7 after primary immunization, which were significantly boosted by the secondary immunization. Strong Th1/Th2 cytokine responses were detected in the peripheral blood mononuclear cells. Compared to immunization with the control rAd-F1, significantly higher levels of the antigen-specific IgA antibodies were detected in the nasal fluids, tracheal washes and lung lavages.¹ Compared to immunization with rAd-Flab-F1, immunization with rAd-F1-Hsp70 induced significantly stronger mucosal IgA antibody response. Cytokine detection of the pig lung lavages showed that the elevated IgA antibody responses were correlated mainly with IL-4, IL-10 and IFN-α, which were confirmed by the significantly increased antigen-recall cytokine expression in the porcine alveolar macrophages. These data suggest that mHsp70 has potent mucosal adjuvanticity in pigs, and the fusion rAd vector can be used for ASFV mucosal vaccine development.

TLR4 Agonist Combined with Trivalent Protein JointS of Streptococcus suis Provides Immunological Protection in Animals

Streptococcus suis (S. suis) serotype 2 (SS2) is the causative agent of swine streptococcosis and can cause severe diseases in both pigs and humans. Although the traditional inactive vaccine can protect pigs from SS2 infection, novel vaccine candidates are needed to overcome its shortcomings. Three infection-associated proteins in S. suis—muramidase-released protein (MRP), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and DLD, a novel putative dihydrolipoamide dehydrogenase—have been previously identified by immunoproteomic assays. In this study, the effective immune protection of the recombinant trivalent protein GAPDH-MRP-DLD (JointS) against SS2, SS7, and SS9 was determined in zebrafish. To improve the immune efficacy of JointS, monophosphoryl lipid A (MPLA) as a TLR4 agonist adjuvant, which induces a strong innate immune response in the immune cells of mice and pigs, was combined with JointS to immunize the mice. The results showed that immunized mice could induce the production of a high titer of anti-S. suis antibodies; as a result, 100% of mice survived after SS2 infection. Furthermore, JointS provides good protection against virulent SS2 strain infections in piglets. Given the above, there is potential to develop JointS as a novel subunit vaccine for piglets to prevent infection by SS2 and other S. suis serotypes.

Mild Cytokine Elevation, Moderate CD4+ T Cell Response and Abundant Antibody Production in Children with COVID-19

Children with Coronavirus Disease 2019 (COVID-19) were reported to show milder symptoms and better prognosis than their adult counterparts, but the difference of immune response against SARS-CoV-2 between children and adults hasn’t been reported. Therefore we initiated this study to figure out the features of immune response in children with COVID-19. Sera and whole blood cells from 19 children with COVID-19 during different phases after disease onset were collected. The cytokine concentrations, SARS-CoV-2 S-RBD or N-specific antibodies and T cell immune responses were detected respectively. In children with COVID-19, only 3 of 12 cytokines were increased in acute sera, including interferon (IFN)-γ-induced protein 10 (IP10), interleukin (IL)-10 and IL-16. We observed an increase in T helper (Th)-2 cells and a suppression in regulatory T cells (Treg) in patients during acute phase, but no significant response was found in the IFN-γ-producing or tumor necrosis factor (TNF)-α-producing CD8⁺T cells in patients. S-RBD and N IgM showed an early induction, while S-RBD and N IgG were prominently induced later in convalescent phase. Potent S-RBD IgA response was observed but N IgA seemed to be inconspicuous. Children with COVID-19 displayed an immunophenotype that is less inflammatory than adults, including unremarkable cytokine elevation, moderate CD4⁺ T cell response and inactive CD8⁺ T cell response, but their humoral immunity against SARS-CoV-2 were as strong as adults. Our finding presented immunological characteristics of children with COVID-19 and might give some clues as to why children develop less severe disease than adults.

Protective Passive Immunity in Escherichia coli ETEC-Challenged Neonatal Mice Conferred by Orally Immunized Dams with Nanoparticles Containing Homologous Outer Membrane Vesicles

Enterotoxigenic Escherichia coli (ETEC) strains are a major cause of illness and death in mammals, including neonatal, recently weaned pigs and infant human beings. We have previously shown that outer membrane vesicles (OMV) obtained from ETEC serotypes encapsulated into zein nanoparticles, coated with a Gantrez-mannosamine polymer conjugate (OMV-NP), were immunogenic in mice and sows. In the present study, we show that pups from vaccinated mice were protected against ETEC F4 serotype challenge through maternal passive immunization. OMV from F4 cultures were collected and characterized. Two-week-pregnant BALB/c mice were orally immunized with a single dose of vesicles (0.2 mg) either free (OMV) or encapsulated into nanoparticles (OMV-NP). Evaluation of the antibodies in serum (IgG1, Ig2a or IgA) and feces (IgA) of dams immunized with OMV-NP revealed an enhancement of specific immunogenicity. The antibody response conferred by the nanoparticle adjuvant was also correlated with IL-6 and IL-10 splenic levels. Each mother was allowed to feed her progeny for one week. Suckling pups presented specific IgA in feces demonstrating their passive immunization through colostrum intake. Two weeks after the pups were born, they were infected orally with a single dose of F4 E. coli (1.2 × 10⁸ CFU/pup). Results showed that 70% of the pups from dams immunized with OMV-NP were protected. In contrast, 80% of the pups from dams immunized with free OMV died as a result of the experimental challenge. These findings support the use of zein nanoparticles coated with a Gantrez-mannosamine shield as adjuvant delivery system for the oral immunization during pregnancy to confer immunity to the offspring through maternal immunization

Enhancement of antigen-specific humoral immune responses and protein solubility through conjugation of bacterial flagellin, Vibrio vulnificus FlaB, to the N-terminus of porcine epidemic diarrhea virus surface protein antigen S0

Porcine epidemic diarrhea (PED) is a highly contagious enteric swine disease. The large economic impact of PED on the swine industry worldwide has made the development of an effective PED vaccine a necessity. S0, a truncated region of the porcine epidemic diarrhea virus (PEDV) spike protein, has been suggested as a candidate antigen for PED subunit vaccines; however, poor solubility problems when the protein is expressed in Escherichia coli, and the inherent problems of subunit vaccines, such as low immunogenicity, remain. Flagellin has been widely used as a fusion partner to enhance the immunogenicity and solubility of many difficult-to-express proteins; however, the conjugation effect of flagellin varies depending on the target antigen or the position of the fusion placement. Here, we conjugated flagellin, Vibrio vulnificus FlaB, to the N- and C-termini of S0 and evaluated the ability of the fusion to enhance the solubility and immunogenicity of S0. Flagellin conjugation in the presence of the trigger factor chaperone tig greatly improved the solubility of the fusion protein (up to 99%) regardless of its conjugation position. Of importance, flagellin conjugated to the N-terminus of S0 significantly enhanced S0-specific humoral immune responses compared to other recombinant antigens in Balb/c mice. The mechanism of this phenomenon was investigated through in vitro and in vivo studies. These findings provide important information for the development of a novel PED vaccine and flagellin-based immunotherapeutics.

Intranasal co-administration of recombinant active fragment of Zonula occludens toxin and truncated recombinant EspB triggers potent systemic, mucosal immune responses and reduces span of E. coli O157:H7 fecal shedding in BALB/c mice

Escherichia coli O157:H7 with its traits such as intestinal colonization and fecal-oral route of transmission demands mucosal vaccine development. E. coli secreted protein B (EspB) is one of the key type III secretory system (TTSS) targets for mucosal candidate vaccine due to its indispensable role in the pathogenesis of E. coli O157:H7. However, mucosally administered recombinant proteins have low immunogenicity which could be overcome by the use of mucosal adjuvants. The quest for safe, potent mucosal adjuvant has recognized ΔG fragment of Zonula occludens toxin of Vibrio cholerae with such properties. ΔG enhances mucosal permeability via the paracellular route by altering epithelial tight junction structure in a reversible, ephemeral and non-toxic manner. Therefore, we tested whether recombinant ΔG intranasally co-administered with truncated EspB (EspB + ΔG) could serve as an effective mucosal adjuvant. Results showed that EspB + ΔG group induced higher systemic IgG and mucosal IgA than EspB alone. Moreover, EspB alone developed Th2 type response with IgG1/IgG2a ratio (1.64) and IL-4, IL-10 cytokines whereas that of EspB + ΔG group generated mixed Th1/Th2 type immune response evident from IgG1/IgG2a ratio (1.17) as well as IL-4, IL-10 and IFN-γ cytokine levels compared to control. Sera of EspB + ΔG group inhibited TTSS mediated haemolysis of murine RBCs more effectively compared to EspB, control group and sera of both EspB + ΔG, EspB group resulted in similar levels of efficacious reduction in E. coli O157:H7 adherence to Caco-2 cells compared to control. Moreover, vaccination with EspB + ΔG resulted in significant reduction in E. coli O157:H7 fecal shedding compared to EspB and control group in experimentally challenged streptomycin-treated mice. These results demonstrate mucosal adjuvanticity of ΔG co-administered with EspB in enhancing overall immunogenicity to reduce E. coli O157:H7 shedding.

Protective immunity against Trichinella spiralis in mice elicited by oral vaccination with attenuated Salmonella-delivered TsSP1.2 DNA

Trichinellosis is a worldwide important food-borne zoonosis caused mainly by ingesting raw or undercooked pork infected with Trichinella spiralis larvae. The development of vaccine is needed for preventing swine from Trichinella infection to ensure pork safety. Previous studies showed that T. spiralis serine protease 1.2 (TsSP1.2) is a vaccine candidate against Trichinella infection. In this study, the complete TsSP1.2 cDNA sequences were cloned into pcDNA3.1, and the rTsSP1.2 DNA was transformed into attenuated Salmonella typhimurium strain ΔcyaSL1344. Oral vaccination of mice with Salmonella-delivered rTsSP1.2 DNA vaccine induced an obvious intestinal mucosal IgA response and a systemic Th1/Th2 immune response; the vaccinated mice showed a 33.45% reduction of intestinal adult worms and 71.84% reduction of muscle larvae after T. spiralis larval challenge. The protection might be due to the rTsSP1.2-induced production of specific anti-TsSP1.2 sIgA, IgG, IgG1/IgG2a, and secretion of IFN-γ, IL-4 and IL-10, which protected intestinal mucosa from the parasite invasion, inhibited worm development and reduced female fecundity. The results indicate that the attenuated Salmonella-delivered rTsSP1.2 DNA vaccine offers a prospective strategy for the prevention and control of animal Trichinella infection.

Mouse immune thrombocytopenia is associated with Th1 bias and expression of activating Fcγ receptors

Immune thrombocytopenia (ITP) is an autoimmune disease mediated by anti-platelet autoantibodies. We recently established a mouse ITP model exhibiting regulatory T-cell (Treg) deficiency, although only one-third of the Treg-deficient mice developed ITP. To clarify mechanisms involved in the emergence of platelet-specific autoimmunity in this model, we examined the T helper (Th)-cell balance and macrophage Fcγ receptor (FcγR) expression profiles in Treg-deficient mice with and without ITP. Splenocytes from both populations of Treg-deficient mice and control BALB/c mice were subjected to flow cytometry-based analyses to evaluate Th cell subset proportions and the expression of activating and inhibitory FcγRs on macrophages. In addition, IgG subclass distribution of anti-platelet autoantibodies in splenocyte culture supernatants was determined by flow cytometry using IgG subclass-specific antibodies. Treg-deficient ITP mice exhibited a significantly higher proportion of Th1 cells than either Treg-deficient non-ITP or control mice. The predominant anti-platelet autoantibody subclasses in the ITP mice were Th1-associated IgG_2a and IgG_2b. Furthermore, the FcγRI/FcγRIIB expression ratio in splenic macrophages was higher in the Treg-deficient ITP than in the Treg-deficient non-ITP and control mice. In summary, Th1 polarization and macrophages' activating FcγR expression profile are associated with the development of ITP in Treg-deficient mice.

E2 multimeric scaffold for vaccine formulation: immune response by intranasal delivery and transcriptome profile of E2-pulsed dendritic cells

BACKGROUND

The E2 multimeric scaffold represents a powerful delivery system able to elicit robust humoral and cellular immune responses upon systemic administrations. Here recombinant E2 scaffold displaying the third variable loop of HIV-1 Envelope gp120 glycoprotein was administered via mucosa, and the mucosal and systemic immune responses were analysed. To gain further insights into the molecular mechanisms that orchestrate the immune response upon E2 vaccination, we analysed the transcriptome profile of dendritic cells (DCs) exposed to the E2 scaffold with the aim to define a specific gene expression signature for E2-primed immune responses.

RESULTS

The in vivo immunogenicity and the potential of E2 scaffold as a mucosal vaccine candidate were investigated in BALB/c mice vaccinated via the intranasal route. Fecal and systemic antigen-specific IgA antibodies, cytokine-producing CD4(+) and CD8(+) cells were induced assessing the immunogenicity of E2 particles via intranasal administration. The cytokine analysis identified a mixed T-helper cell response, while the systemic antibody response showed a prevalence of IgG1 isotype indicative of a polarized Th2-type immune response. RNA-Sequencing analysis revealed that E2 scaffold up-regulates in DCs transcriptional regulators of the Th2-polarizing cell response, defining a type 2 DC transcriptomic signature.

CONCLUSIONS

The current study provides experimental evidence to the possible application of E2 scaffold as antigen delivery system for mucosal immunization and taking advantages of genome-wide approach dissects the type of response induced by E2 particles.

Oral vaccination of mice with Trichinella spiralis nudix hydrolase DNA vaccine delivered by attenuated Salmonella elicited protective immunity

We have previously reported that Trichinella spiralis Nudix hydrolase (TsNd) bound to intestinal epithelial cells (IECs), and the vaccination of mice with recombinant TsNd protein (rTsNd) produced a partial protective immunity against challenge infection in mice. In this study, the full-length cDNA sequence of TsNd gene was cloned into the eukaryotic expression plasmid pcDNA3.1, and the recombinant TsNd DNA was transformed into attenuated Salmonella typhimurium strain ⊿cyaSL1344. Oral immunization of mice with TsNd/S. typhimurium elicited a significant local mucosal IgA response and a systemic Th1/Th2 immune response. Cytokine profiling also showed a significant increase in the Th1 (IFN-γ, IL-2) and Th2 (IL-4, 10) responses in splenocytes of immunized mice upon stimulation with the rTsNd. The oral immunization of mice with TsNd/S. typhimurium displayed a statistically significant 73.32% reduction in adult worm burden and a 49.5% reduction in muscle larvae after challenge with T. spiralis muscle larvae, compared with PBS control group. Our results demonstrated that TsNd DNA delivered by attenuated live S. typhimurium elicited a local IgA response and a mixed Th1/Th2 immune response, and produced a partial protection against T. spiralis infection in mice.

Protective immunity against Trichinella spiralis infection induced by TsNd vaccine in mice

Background

We have previously reported that Trichinella spiralis Nudix hydrolase (TsNd) bound to intestinal epithelial cells (IECs), and vaccination of mice with recombinant TsNd protein (rTsNd) produced a partial protective immunity. The aim of this study was to investigate the immune protection induced by TsNd DNA vaccine.

Methods

The full-length cDNA sequence of TsNd gene was cloned into pcDNA3.1 and used to immunize BALB/c mice by intramuscular injection. Transcription and expression of TsNd were detected by RT-PCR and IFT. The levels of specific IgA, IgG, IgG1 and IgG2a, and cytokines were assayed by ELISA at weeks 0, 6 and 8 post-immunization. The immune protection of TsNd DNA vaccine against challenge infection was investigated.

Results

Immunization of mice with TsNd DNA elicited a systemic Th1/Th2 immune response and a local mucosal IgA response. The in vitro transcription and expression of TsNd gene was observed at all developmental stages of T. spiralis (ML, IIL, AW and NBL). Anti-rTsNd IgG levels were increased after immunization and levels of IgG1 were obviously higher than that of IgG2a. Intestinal specific IgA levels of immunized mice were significantly higher than those of vector and PBS control mice. Cytokine profiling also showed a significant increase in Th1 (IFN-γ, IL-2) and Th2 (IL-4, 10) responses in splenocytes of immunized mice on stimulation with rTsNd. Vaccination of mice with pcDNA3.1-TsNd displayed a 40.44% reduction in adult worms and a 53.9% reduction in larval burden.

Conclusions

TsNd DNA induced a mixed Th1/Th2 immune response and partial protection against T. spiralis infection in mice.

Innate Mucosal Immune System Response of BALB/c vs C57BL/6 Mice to Injury in the Setting of Enteral and Parenteral Feeding

BACKGROUND

Outbred mice exhibit increased airway and intestinal immunoglobulin A (IgA) following injury when fed normal chow, consistent with humans. Parenteral nutrition (PN) eliminates IgA increases at both sites. Inbred mice are needed for detailed immunological studies; however, specific strains have not been evaluated for this purpose. BALB/c and C57BL/6 are common inbred mouse strains but demonstrate divergent immune responses to analogous stress. This study addressed which inbred mouse strain best replicates the outbred mouse and human immune response to injury.

METHODS

Intravenously cannulated mice received chow or PN for 5 days and then underwent sacrifice at 0 or 8 hours following controlled surgical injury (BALB/c: n = 16-21/group; C57BL/6: n = 12-15/group). Bronchoalveolar lavage (BAL) was analyzed by enzyme-linked immunosorbent assay for IgA, tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6, while small intestinal wash fluid (SIWF) was analyzed for IgA.

RESULTS

No significant increase in BAL IgA occurred following injury in chow- or PN-fed BALB/c mice (chow: P = .1; PN: P = .7) despite significant increases in BAL TNF-α and SIWF IgA (chow: 264 ± 28 vs 548 ± 37, P < .0001; PN: 150 ± 12 vs 301 ± 17, P < .0001). Injury significantly increased mucosal IgA in chow-fed C57BL/6 mice (BAL: 149 ± 33 vs 342 ± 87, P = .01; SIWF: 236 ± 28 vs 335 ± 32, P = .006) and BAL cytokines. After injury, PN-fed C57BL/6 mice exhibited no difference in BAL IgA (P = .9), BAL cytokines, or SIWF IgA (P = .1).

CONCLUSIONS

C57BL/6 mice exhibit similar airway responses to injury as outbred mice and humans, providing an appropriate model for studying mucosal responses to injury. The BALB/c mucosal immune system responds differently to injury and does not replicate the human injury response.

Generation of an attenuated strain oral vaccine candidate using a novel double selection platform in Escherichia coli

Live attenuated bacteria delivered orally are interesting tools for mucosal immunization. The objective of this study was to construct a novel counter-selection platform based on an attenuated wild-type Escherichia coli (E. coli) strain and to utilize it for the delivery of LTR192G-STaA13Q fusion protein as an oral vaccine. First, a counter-selectable marker, namely, PRPL-Kil, was inserted into an attenuated wild-type E. coli strain through the use of the red and G-DOC homologous recombination systems to construct the counter-selection platform, and PRPL-Kil was subsequently replaced by the LT192-STa13 fusion gene to construct the oral vaccine O142 (yaiT::LT192-STa13) (ER-A). Subsequently, BALB/c mice were orogastrically inoculated with ER-A. Our results showed that ER-A could induce the production of specific IgA and IgG against fimbriae (F41) and enterotoxins (LT and STa), with neutralizing activity in BALB/c mice. In addition, assays of cellular immune responses showed that the stimulation index (SI) values of immunized mice were significantly higher than those of control mice (P<0.05), and revealed a marked shift toward Th2-mediated immunity. These findings suggest that ER-A is a suitable candidate for an oral vaccine strain to protect animals from enter toxigenic Escherichia coli (ETEC) infection.

Protective effect of a prime-boost strategy with the Ts87 vaccine against Trichinella spiralis infection in mice

Trichinellosis is a widespread zoonosis primarily caused by Trichinella spiralis. Mucosal immunity is crucial for preventing Trichinella spiralis infection. In our previous study, a DNA vaccine with the Trichinella antigen Ts87 delivered by an attenuated Salmonella typhimurium elicited partial protection against Trichinella spiralis infection in mice. In the current study, to elicit a more robust immune response and develop a potent vaccination strategy against trichinellosis, a heterologous prime-boost vaccination regimen for Ts87 was used in mice and the protective efficacy was evaluated compared to the homologous DNA prime-boost or protein prime-boost immunization alone. The results revealed that the DNA-prime/protein-boost vaccination with Ts87 induced higher levels of both humoral and cellular immune responses. The challenge results showed that mice with the DNA-prime/protein-boost vaccination displayed higher muscle larval reduction than those immunized with DNA prime-boost or protein prime-boost. The results demonstrated that mice vaccinated with Ts87 in a DNA-prime/protein-boost strategy effectively elicited a local IgA response and mixed Th1/Th2 immune response that might be responsible for improved protection against Trichinella spiralis infection.

Distinctive histopathology and modulation of cytokine production during oral and intraperitonealTrypanosoma cruziY strain infection

Acute Chagas disease outbreaks are related to the consumption of food or drink contaminated by triatomine feces, thus making oral infection an important route of transmission. Both vector-borne and oral infections trigger important cardiac manifestations in the host that are related to a dysregulated immune response. The aims of this work were to evaluate possible alterations of lymphocyte CD4+/CD8+sub-populations, Th1 and Th2 cytokines, nitrite concentrations and cardiac histopathology. One group of male Wistar rats was intraperitoneally infected (I.P.) with 1×105metacyclic trypomastigotes of theT. cruziY strain, and another group of Wistar rats was orally infected (O.I.) with 8×105metacyclic trypomastigotes of the same strain. The intraperitoneal infection triggered statistically enhanced parasite and peritoneal macrophage numbers, increased concentrations of NO and IL-12 and elevated cardiac inflammatory foci when compared with the oral infection. However, proliferation of CD4+and CD8+T cells were not statistically different for oral and intraperitoneal routes.

Evaluation of mucosal and systemic immune responses elicited by GPI-0100- adjuvanted influenza vaccine delivered by different immunization strategies

Vaccines for protection against respiratory infections should optimally induce a mucosal immune response in the respiratory tract in addition to a systemic immune response. However, current parenteral immunization modalities generally fail to induce mucosal immunity, while mucosal vaccine delivery often results in poor systemic immunity. In order to find an immunization strategy which satisfies the need for induction of both mucosal and systemic immunity, we compared local and systemic immune responses elicited by two mucosal immunizations, given either by the intranasal (IN) or the intrapulmonary (IPL) route, with responses elicited by a mucosal prime followed by a systemic boost immunization. The study was conducted in BALB/c mice and the vaccine formulation was an influenza subunit vaccine supplemented with GPI-0100, a saponin-derived adjuvant. While optimal mucosal antibody titers were obtained after two intrapulmonary vaccinations, optimal systemic antibody responses were achieved by intranasal prime followed by intramuscular boost. The latter strategy also resulted in the best T cell response, yet, it was ineffective in inducing nose or lung IgA. Successful induction of secretory IgA, IgG and T cell responses was only achieved with prime-boost strategies involving intrapulmonary immunization and was optimal when both immunizations were given via the intrapulmonary route. Our results underline that immunization via the lungs is particularly effective for priming as well as boosting of local and systemic immune responses.

Enhancement of the immunogenicity and protective efficacy of a mucosal influenza subunit vaccine by the saponin adjuvant GPI-0100

Identification of safe and effective adjuvants remains an urgent need for the development of inactivated influenza vaccines for mucosal administration. Here, we used a murine challenge model to evaluate the adjuvant activity of GPI-0100, a saponin-derived adjuvant, on influenza subunit vaccine administered via the intranasal or the intrapulmonary route. Balb/c mice were immunized with 1 µg A/PR/8 (H1N1) subunit antigen alone or in combination with varying doses of GPI-0100. The addition of GPI-0100 was required for induction of mucosal and systemic antibody responses to intranasally administered influenza vaccine and significantly enhanced the immunogenicity of vaccine administered via the intrapulmonary route. Remarkably, GPI-0100-adjuvanted influenza vaccine given at a low dose of 2×1 µg either in the nares or directly into the lungs provided complete protection against homologous influenza virus infection.

Attenuated Salmonella Gallinarum secreting an Escherichia coli heat-labile enterotoxin B subunit protein as an adjuvant for oral vaccination against fowl typhoid

In our previous study, we constructed a vaccine candidate (JOL916) for fowl typhoid (FT). A live adjuvant Salmonella Gallinarum (SG) strain was generated in the present study to facilitate efficacious oral vaccination with this vaccine. The Escherichia coli eltB gene secreting heat-labile enterotoxin B subunit (LTB) was cloned into an Asd(+) plasmid pJHL65. This was transformed into a Δlon ΔcpxR Δasd SG strain and the resulting strain was designated JOL1229. Secretion of LTB from JOL1229 was confirmed with an immunoblot assay. To determine the optimal dose of the strain, 50 six-week-old female chickens were divided into five groups (Groups A-E, n=10 per group) and orally inoculated with various doses of JOL1229 and JOL916. In Group B (consisting of four parts JOL916 and one part JOL1229), significant cell-mediated immune responses, plasma IgG levels and intestinal secretary IgA levels were induced after inoculation with both strains. On challenge with the wild-type strain, significant reductions in mortality were observed in the group. In addition, after inoculation the LTB strain was not recovered in feces samples, and resulted in no, or very mild, gross lesions in the liver and spleen. Both CD4(+) and CD8(+) T-cells were significantly increased in peripheral blood samples from the chickens immunized with the LTB strain. Expression of the interleukin-6 (IL-6) gene in splenocytes was induced in the chickens immunized with the LTB strain. These results suggest that oral immunization with the LTB-adjuvant strain, in particular with the four parts JOL916 and one part JOL1229 mixture, increased the immune response and provided efficient protection against FT in chickens.

Nasal immunization with a fusion protein consisting of the hemagglutinin A antigenic region and the maltose-binding protein elicits CD11c(+) CD8(+) dendritic cells for induced long-term protective immunity

We assessed the efficacy of a fusion protein consisting of the 25-kDa antigenic region of Porphyromonas gingivalis hemagglutinin A and the Escherichia coli maltose-binding protein (25k-hagA-MBP) as a nasal vaccine for the prevention of oral infection with P. gingivalis. Nasal immunization with 25k-hagA-MBP induced high levels of 25k-hagA-specific serum IgG, serum IgA, and salivary IgA antibodies in a Toll-like receptor 4 (TLR4)-dependent manner. These antibody responses were maintained for at least 1 year after immunization. Analysis of cytokine responses showed that nasal administration of 25k-hagA-MBP induced antigen-specific CD4(+) T cells producing interleukin 4 (IL-4) and IL-5, but not gamma interferon (IFN-γ), in the spleen and cervical lymph nodes (CLNs). Furthermore, increased numbers of CD11c(+) CD8α(+), but not CD11c(+) CD11b(+) or CD11c(+) B220(+), dendritic cells with upregulated expression of CD80, CD86, CD40, and major histocompatibility complex class II (MHC II) molecules were noted in the spleen, CLNs, and nasopharynx-associated lymphoreticular tissues (NALT). Interestingly, when 25k-hagA-MBP or cholera toxin (CT) was given intranasally to enable examination of their presence in neuronal tissues, the amounts of 25k-hagA-MBP were significantly lower than those of CT. Importantly, mice given 25k-hagA-MBP nasally showed a significant reduction in alveolar bone loss caused by oral infection with P. gingivalis, even 1 year after the immunization. These results suggest that 25k-hagA-MBP administered nasally would be an effective and safe mucosal vaccine against P. gingivalis infection and may be an important tool for the prevention of chronic periodontitis in humans.

Regulation of IgA responses in cattle, humans and mice

Secretory IgA (SIgA) constitutes the largest component of the humoral immune system of the body with gram quantities of this isotype produced by mammals on a daily basis. Secretory IgA (SIgA) antibodies function by both blocking pathogen/commensal entry at mucosal surfaces and virus neutralization. Several pathways of induction of IgA responses have been described which depend on T cells (T cell dependent or TD) pathways or are independent of T cells (T-independent or TI) and are mediated by dendritic cells (DCs) and/or epithelial cells. Many elements of IgA regulation readily cross species barriers (adjuvants, soluble and cognate factors) and are highly conserved whereas other pathways may be more specific to any given species and must be evaluated. Regulation of IgA production in cattle is not completely understood and thus we have focused in part on highly conserved factors such as transforming growth factor beta, Type I and Type 2 interferons, neuropeptides which interdigitate mucosal tissues (vasoactive intestinal peptide or VIP), and a small peptide (IgA inducing peptide or IGIP) which can serve as targets for modulation and increasing SIgA virus-specific antibodies. We have evaluated the potential utility of modulating these factors in vitro in regulation of qualitative aspects of antibodies of the IgM, IgG and IgA isotypes at mucosal surfaces and in secretions of the upper and lower respiratory tract to a virus of economic and public health importance, foot and mouth disease virus (FMDV). IgA responses in cattle are essential for host defense in response to various infectious agents. In cattle, IgA is not released into the colostrum, as is the case for other mammals but only IgG1 is selectively transported. In previous studies in cattle, IgA has been shown to be regulated by several cytokines including IFN-gamma, Type I interferons such as IFN-alpha and IFN-tau, transforming growth factor beta, IgA inducing peptide and other potential factors such as APRIL and BlyS which have not yet been fully evaluated in cattle. Many of these factors, namely TGF-beta and Type I interferons block cell cycle progression which is an essential component of Ig class switching and thus these factors require additional regulatory factors such as IL-2 to drive cells through cell cycle resulting in class switch recombination. Among these factors, IgA inducing peptide was originally identified from a bovine gut associated lymphoid tissue expression library and is highly conserved in pigs and humans at >90% at the amino acid level. The factor is regulated differently in various species but is consistently produced by dendritic cells.

Oral immunization with Porphyromonas gingivalis outer membrane protein and CpGoligodeoxynucleotides elicits T helper 1 and 2 cytokines for enhanced protective immunity

The aim of this study was to evaluate the efficacy of an oral vaccine containing the 40-kDa outer membrane protein of Porphyromonas gingivalis (40K OMP) and synthetic oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG ODN) to control oral infection by P. gingivalis. [run on]40K-OMP40K-OMP40K-OMPOral immunization with 40K-OMP plus CpG ODN induced significant 40K-OMP-specific serum IgG, IgA and saliva IgA antibody responses. The 40K-OMP-specific CD4(+) T cells induced by oral 40K-OMP plus CpG ODN produced both Th1 (IFN-gamma) and Th2 (IL-4) cytokines. Furthermore, increased frequencies of CD11c(+)B220(+) DCs and CD11c(+)CD11b(+) DCs with up-regulated expression of CD80, CD86, CD40 and MHC II molecules were noted in spleen, Peyer's patches and cervical lymph nodes. Immunized mice were then infected orally with P. gingivalis to determine whether the immune responses induced by oral 40K-OMP plus CpG ODN were capable of suppressing bone resorption caused by P. gingivalis infection. Mice given 40K-OMP plus CpG ODN showed significantly reduced bone loss associated with oral infection by P. gingivalis.Thus, oral administration of 40K-OMP together with CpG ODN induces Th1- and Th2-type cells, which provide help for protective immunity against P. gingivalis infection. This may be an important tool for prevention of chronic periodontitis.

Identification of a novel antigen-presenting cell population modulating antiinfluenza type 2 immunity

Antiinfluenza type 2 (T2) immunity contributes to both immunopathology and immunoprotection, yet the underlying mechanisms modulating T2 immunity remain ill defined. We describe a novel mouse antigen (Ag)-presenting cell (APC), designated late-activator APC (LAPC). After pulmonary influenza A (H1N1) virus infection, LAPCs enter the lungs, capture viral Ag, and subsequently migrate to the draining lymph node (DLN) and spleen, with delayed kinetics relative to dendritic cells (DCs). In the DLN, influenza virus–activated LAPCs present Ag and selectively induce T helper type 2 (Th2) effector cell polarization by cell–cell contact–mediated modulation of GATA-3 expression. In adoptive transfer experiments, influenza virus–activated LAPCs augmented Th2 effector T cell responses in the DLN, increased production of circulating antiinfluenza immunoglobulin, and increased levels of T2 cytokines in bronchoalveolar lavage fluid in recipient influenza virus–infected mice. LAPC-recipient mice exhibited exacerbated pulmonary pathology, with delayed viral clearance and enhanced pulmonary eosinophilia. Collectively, our results identify and highlight the importance of LAPCs as immunomodulators of T2 immunity during influenza A virus infection.

Oral vaccination with Ts87 DNA vaccine delivered by attenuated Salmonella typhimurium elicits a protective immune response against Trichinella spiralis larval challenge

We have previously reported that Ts87 is an immunodominant antigen that induces protective immunity against Trichinella spiralis larval challenge. In this study, the Ts87 gene was cloned into an expression plasmid, pVAX1, and the recombinant Ts87 DNA was transformed into attenuated Salmonella typhimurium strain SL7207. Oral immunization of mice with Ts87 DNA delivered in S. typhimurium elicited a significant local mucosal IgA response and a systemic Th1/Th2 immune response. Cytokine profiling also showed a significant increase in the Th1 (IFN-gamma) and Th2 (IL-5, 6, 10) responses in splenocytes of immunized mice upon stimulation with Ts87 antigen. An immunofluorescence assay performed with antisera revealed that the recombinant Ts87 protein was expressed in mesenteric lymph nodes of immunized mice. The mice immunized with Salmonella-delivered Ts87 DNA displayed a statistically significant 29.8% reduction in adult worm burden and a 34.2% reduction in muscle larvae following challenge with T. spiralis larvae, compared with mice immunized with empty Salmonella or a PBS control. Our results demonstrate that Ts87 DNA delivered by attenuated live S. typhimurium elicits a local IgA response and a balanced Th1/Th2 immune response and produces partial protection against T. spiralis infection in mice.

Innate signaling networks in mucosal IgA class switching

The past 20 years have seen a growing interest over the control of adaptive immune responses by the innate immune system. In particular, considerable attention has been paid to the mechanisms by which antigen-primed dendritic cells orchestrate the differentiation of T cells. Additional studies have elucidated the pathways followed by T cells to initiate immunoglobulin responses in B cells. In this review, we discuss recent advances on the mechanisms by which intestinal bacteria, epithelial cells, dendritic cells, and macrophages cross talk with intestinal T cells and B cells to induce frontline immunoglobulin A class switching and production.

Differential requirements for protection against mucosal challenge with Francisella tularensis in the presence versus absence of cholera toxin B and inactivated F. tularensis

Francisella tularensis is a category A biothreat agent for which there is no approved vaccine and the correlates of protection are not well understood. In particular, the relationship between the humoral and cellular immune response to F. tularensis and the relative importance of each in protection is controversial. Yet, understanding this relationship will be crucial to the development of an effective vaccine against this organism. We demonstrate, for the first time, a differential requirement for humoral vs cellular immunity in vaccine-induced protection against F. tularensis infection, and that the requirement for Ab observed in some protection studies, may be overcome through the induction of enhanced cellular immunity. Specifically, following intranasal/mucosal immunization of mice with inactivated F. tularensis organisms plus the cholera toxin B subunit, we observe increased production of IgG2a/2c vs IgG1 Ab, as well as IFN-gamma, indicating induction of a Th1 response. In addition, the requirement for F. tularensis-specific IgA Ab production, observed in studies following immunization with inactivated F. tularensis alone, is eliminated. Thus, these data indicate that enhanced Th1 responses can supersede the requirement for anti-F. tularensis-specific IgA. This observation also has important ramifications for vaccine development against this organism.

Human IgA-inducing protein from dendritic cells induces IgA production by naive IgD+ B cells

Over the last several years, there has been a great deal of progress in characterizing the role of dendritic cells (DCs) in the activation and modulation of B cells. DC-secreted chemokines can induce B cell trafficking to the lymph nodes. DC-produced survival factors such as B cell-activating factor of the TNF family and a proliferation-inducing ligand have been shown to be essential for B cell maturation, but have also been implicated in class-switch recombination and B cell lymphoma survival. Recently added to this list of DC-derived factors effecting B cells is IgA-inducing protein (IGIP). In this study, we characterize production of IGIP by human DCs, and examine its capacity to induce IgA class switching and differentiation of naive B cells in vitro. Monocyte-derived DCs were cultured in vitro with TLR agonists (TLR3, 4, 5, and 9) and other factors, including CD40 ligand, GM-CSF, and IL-4 as well as the neuropeptide vasoactive intestinal peptide. Under in vitro stimulation with vasoactive intestinal peptide and CD40L, IGIP mRNA expression could be up-regulated as much as 35-fold above nonstimulated samples within 12-48 h. Naive B cells cultured with exogenous recombinant human IGIP produced IgA in greater quantities than nonstimulated controls. Finally, we demonstrate that IGIP stimulation drives the production of mu-alpha switch circles from IgM(+)IgD(+) naive human B cells, indicating its role as an IgA switch factor.

Trans-sialidase recombinant protein mixed with CpG motif-containing oligodeoxynucleotide induces protective mucosal and systemic trypanosoma cruzi immunity involving CD8+ CTL and B cell-mediated cross-priming

The Trypanosoma cruzi trans-sialidase (TS) is a unique enzyme with neuraminidase and sialic acid transfer activities important for parasite infectivity. The T. cruzi genome contains a large family of TS homologous genes, and it has been suggested that TS homologues provide a mechanism of immune escape important for chronic infection. We have investigated whether the consensus TS enzymatic domain could induce immunity protective against acute and chronic, as well as mucosal and systemic, T. cruzi infection. We have shown that: 1) TS-specific immunity can protect against acute T. cruzi infection; 2) effective TS-specific immunity is maintained during chronic T. cruzi infection despite the expression of numerous related TS superfamily genes encoding altered peptide ligands that in theory could promote immune tolerization; and 3) the practical intranasal delivery of recombinant TS protein combined with a ssDNA oligodeoxynucleotide (ODN) adjuvant containing unmethylated CpG motifs can induce both mucosal and systemic protective immunity. We have further demonstrated that the intranasal delivery of soluble TS recombinant Ag combined with CpG ODN induces both TS-specific CD4(+) and CD8(+) T cells associated with vaccine-induced protective immunity. In addition, optimal protection induced by intranasal TS Ag combined with CpG ODN requires B cells, which, after treatment with CpG ODN, have the ability to induce TS-specific CD8(+) T cell cross-priming. Our results support the development of TS vaccines for human use, suggest surrogate markers for use in future human vaccine trials, and mechanistically identify B cells as important APC targets for vaccines designed to induce CD8(+) CTL responses.

Mid-life stress is associated with both up- and down-regulation of markers of humoral and cellular immunity

Perception of stress with consequent activation of a neuroendocrine cascade causes changes in immune function that may be bi-directional, with alterations in basal levels of biological parameters outside the optimal range. In this cross-sectional study of 302 healthy persons (males 56.3%, females 43.7%) aged 41-46 years, higher stress levels, as assessed by questionnaire measures of recurrent and recent perceived stress, were associated with a 4-fold greater risk of having a high compared to mid-range serum neopterin concentration, indicating activation of cellular immune mechanisms [adjusted odds ratio, OR; (95% confidence intervals, CI): Low stress=1.00 (reference group); Medium stress=4.13 (1.51, 11.29); High stress=4.63, (1.35, 15.83), p for trend=0.01]. Higher stress levels were associated with a 3-fold greater risk of having signs of humoral immune activation, as indicated by salivary IgA concentration [high compared to mid-range salivary IgA: Low stress=1.00 (reference group); Medium stress=1.06 (0.48, 2.34); High stress=3.62 (1.26, 10.39), p for trend=0.02], but also a 4-fold greater risk of humoral immune depression [low compared to mid-range IgA: Low stress=1.00 (reference group); Medium stress=1.72 (0.74, 3.99); High stress=4.38 (1.47, 13.00), p for trend=0.02]. In conclusion, in this cross-sectional study, higher stress levels were associated with higher serum neopterin and both elevated and depressed salivary IgA levels. These findings emphasise the importance of considering that stress may have bi-directional effects on immune mechanisms, and are consistent with an activational effect of chronic, perceived stress on cellular immunity, and a bi-directional effect on IgA levels, one aspect of humoral immunity.

Effect of adjuvants and route of immunizations on the immune response to recombinant plague antigens

In this study, we compare four different adjuvants, LT(R192G), CpG ODN, MPL((R))TDM, and alum, for their ability to affect the magnitude, distribution, and duration of antibody responses against F1-V, the lead-candidate antigen for the next generation vaccine against plague, in a murine model. In addition, three different routes of immunization-intranasal (IN), transcutaneous (TC), and subcutaneous (SC) were compared with each adjuvant. Since aerosol exposure to biological warfare agents is of primary concern, both serum and bronchioalveolar lavage (BAL) were analyzed for antigen-specific antibody responses. The most significant findings of the study reported here are that (1) the adjuvant influences the Type 1/Type 2 balance of the antibody response in both the serum and BAL, (2) mucosal immunization is not necessary to obtain F1-V-specific BAL responses, (3) non-traditional adjuvants such as LT(R192G) work when delivered subcutaneously, (4) the route of immunization affects the magnitude of the immune response, and (5) F1-V is highly immunogenic by some routes even in the absence of an exogenously applied adjuvant. These studies provide important insights into the influence of different classes of adjuvants on the immune outcome in biodefense vaccines and for development of new-generation vaccines against other pathogens as well.

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.

T-2 toxin impairment of enteric reovirus clearance in the mouse associated with suppressed immunoglobulin and IFN-gamma responses

Trichothecenes are exquisitely toxic to the gastrointestinal (GI) tract and leukocytes and thus are likely to impair gut immunity. The purpose of this research was to test the hypothesis that the Type A trichothecene T-2 toxin interferes with the gut mucosal immune response to enteric reovirus infection. Mice were exposed i.p. first to 1.75 mg/kg bw T-2 and then 2 h later with 3 × 10⁷ plaque-forming units of reovirus serotype 1, strain Lang (T1/L). As compared to vehicle-treated control, T-2-treated mice had dramatically elevated intestinal plaque-forming viral titers after 5 days and failed to completely clear the virus from intestine by 10 days. Levels of reovirus λ2 core spike (L2 gene) RNA in feces in T-2-treated mice were significantly higher at 1, 3, 5, and 7 days than controls. T-2 potentiated L2 mRNA expression in a dose-dependent manner with as little as 50 μg/kg of the toxin having a potentiative effect. T-2 exposure transiently suppressed induction of reovirus-specific IgA in feces (6 and 8 days) as well as specific IgA and IgG_2a in serum (5 days). This suppression corresponded to decreased secretion of reovirus-specific IgA and IgG_2a in Peyer's patch (PP) and lamina propria fragment cultures prepared 5 days after infection. T-2 suppressed IFN-γ responses in PP to reovirus at 3 and 7 days as compared to infected controls whereas IL-2 mRNA concentrations were unaffected. PP IL-6 mRNA levels were increased 2-fold 2 h after T-2 treatment, but no differences between infected T-2-exposed and infected vehicle-treated mice were detectable over the next 7 days. Overall, the results suggest that T-2 toxin increased both the extent of GI tract reovirus infection and fecal shedding which corresponded to both suppressed immunoglobulin and IFN-γ responses.

Brucella spp. lumazine synthase: a novel adjuvant and antigen delivery system to effectively induce oral immunity

Brucella lumazine synthase (BLS) has been previously used with success as a delivery system for systemic immunization against murine cysticercosis. We herein determined the usefulness of BLS as a new antigen-delivery system and mucosal-adjuvant using KETc1, one of the peptides of the anti-cysticercosis vaccine. A protection of up to 98% was induced when KETc1 was used as a chimera fused to BLS. Used as adjuvant of KETc1, BLS also induced a high level of protection (79%), which did not significantly differ from that induced by the cholera toxin (74%). KETc1 and BLS administered separately also reduced the parasite load. KETc1 administered orally as a chimera, and to a lesser extent with BLS as adjuvant, elicited IgG and IgA specific antibodies, which were detectable both in fecal extracts and in sera, and increased B and CD4 activated cells. BLS-KETc1 also increased the levels of transcription of TNF-alpha, IL-2 and IFNgamma in Peyer's patches, and in spleen, only increased TNF-alpha was observed. Overall, these results showed that BLS can be used as both an antigen-carrier and as an adjuvant in the design of new oral subunit vaccines.

Type 1 immunity provides both optimal mucosal and systemic protection against a mucosally invasive, intracellular pathogen

It has been hypothesized that optimal vaccine immunity against mucosally invasive, intracellular pathogens may require the induction of different types of immune responses in mucosal and systemic lymphoid tissues. Mucosal type 2/3 responses (producing interleukin-4 [IL-4], IL-6 and/or transforming growth factor beta) could be necessary for optimal induction of protective secretory immunoglobulin A responses. On the other hand, systemic type 1 responses (including gamma interferon [IFN-gamma], tumor necrosis factor alpha, and optimal cytotoxic T-cell responses) are likely to be critical for protection against the disseminated intracellular replication that occurs after mucosal invasion. Despite these predictions, we recently found that vaccines inducing highly polarized type 1 immunity in both mucosal and systemic tissues provided optimal mucosal and systemic protection against the protozoan pathogen Trypanosoma cruzi. To further address this important question in a second model system, we now have studied the capacity of knockout mice to develop protective immune memory. T. cruzi infection followed by nifurtimox treatment rescue was used to immunize CD4, CD8, beta2-microglobulin, inducible nitric oxide synthase (iNOS), IL-12, IFN-gamma, and IL-4 knockout mice. Despite the previously demonstrated importance of CD4(+) T cells, CD8(+) T cells, and nitric oxide for T. cruzi immunity, CD4, CD8, and iNOS knockout mice developed mucosal and systemic protective immunity. However, IL-12, IFN-gamma, and beta2-microglobulin-deficient mice failed to develop mucosal or systemic protection. In contrast, IL-4 knockout mice developed maximal levels of both mucosal and systemic immune protection. These results strongly confirm our earlier conclusion from studies with polarizing vaccination protocols that type 1 immunity provides optimal mucosal and systemic protection against a mucosally invasive, intracellular pathogen.

Modulation of Murine Host Response to Enteric Reovirus Infection by the Trichothecene Deoxynivalenol

Based on the known capacity of deoxynivalenol (DON) to target gut lymphoid tissue and IgA production, it was hypothesized that this mycotoxin interferes with the immune response to enteric reovirus infection. When mice were orally gavaged, first with 25 mg/kg bw DON, and then with reovirus serotype 1, strain Lang (T1/L) 2 or 12 h later, viral titers in the GI tract were 10-fold higher than control mice after 5 days. Virus was almost completely cleared in both treatment and control groups from intestinal tissue after 10 days. Real-time PCR indicated that, in infected control mice, reovirus lambda2 core spike (L2 gene) RNA per g feces in infected mice that were pretreated with DON was significantly higher at 1, 3, and 5 days than in infected mice only. In reovirus-infected mice, DON at doses of 10 and 25 mg/kg bw but not 2 and 5 mg/kg bw increased fecal L2 RNA, whereas DON doses as low as 2 mg/kg potentiated L2 RNA levels in Peyer's patches (PP). Reovirus-specific IgA levels in feces of mice treated with DON were significantly elevated, as were specific IgA responses in lamina propria and PP fragment cultures. Similar effects were observed for serum IgA and IgG. DON suppressed IFN-gamma responses in PP to reovirus at 3 and 5 days as compared to infected controls, while IL-2 mRNA concentrations were unaffected. Although reovirus alone did not induce Th2 cytokine mRNAs in PP, DON exposure significantly elevated IL-4, IL-6, and IL-10 mRNA expression at various times during the infection. ELISPOT revealed that mRNA expression data corresponded to suppression of IFN-gamma- and enhancement of IL-4-producing cell responses in PP cultures from DON-treated mice. Taken together, these data suggest that DON transiently increased both severity of the reovirus infection and shedding in feces as well as elevated reovirus IgA responses. These effects corresponded to suppressed Th1 and enhanced Th2 cytokine expression.

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.

The pathogenicity of Entamoeba histolytica is related to the capacity of evading innate immunity

The host and parasite factors that influence susceptibility to Entamoeba histolytica infection and disease are not well understood. Entamoeba histolytica pathogenicity has been considered by focusing principally on parasite rather than host factors. Thus, research has concentrated on explaining the molecular differences between pathogenic E. histolytica and non-pathogenic E. dispar. However, the amoeba molecules considered most important for host tissue destruction (amoebapore, galactose/N-acetyl galactosamine inhibitable lectin, and cysteine proteinases) are present in both pathogenic E. histolytica and non-pathogenic E. dispar. In addition, the genetic differences in pathogenicity among E. histolytica isolates are unlikely to completely explain the different outcomes of infection. Considering that the principal difference between pathogenic and non-pathogenic amoebas lies in their surface coats, we propose that pathogenicity of the amoebas is related to the composition and properties of the surface coat components (or pathogen-associated molecular patterns, PAMPs), and the ability of innate immune response to recognize these components and eliminate the parasite. According to this hypothesis, a key feature that may distinguish pathogenic (E. histolytica) from non-pathogenic (E. dispar) strains is whether or not they can overcome innate immune defences. A corollary of this hypothesis is that in susceptible individuals the PAMPs are either not recognized or they are recognized by a set of Toll-like receptors (TLRs) that leads to an inflammatory response. In both cases, the result is tissue damage. On the contrary, in resistant individuals the innate/inflammatory response, induced through the activation of a different set of TLRs, eliminates the parasite.