LUVs Recovered with Chitosan: A New Preparation for Vaccine Delivery

Chitosan, α-(1–4)-amino-2-deoxy-β-D-glucan, is a deacetylated form of chitin, an abundant natural polysaccharide present in crustacean shells. Its unique characteristics such as positive charge, biodegradability, biocompatibility, nontoxicity, and rigid linear molecular structure make this macromolecule ideal as drug carrier. The association between chitosan and liposomes was carefully described, where REVs (reverse phase evaporation vesicles) were sandwiched by chitosan. The usage of these particles in vaccine formulation is here proposed for the first time in the literature. The Chitosan-REVs now stabilized by polyvinilic alcohol were the vehicle for Diphtheria toxoid (Dtxd). Round chitosan-sandwiched REVs (REVs-Chi) particles of 373 ± 17 nm containing 65% Dtxd were obtained. After 200 min of incubation in a simulated gastric fluid, 70% of the Dtxd was liberated from REVs-Chi in comparison to 100% of Dtxd liberated from pure REVs. In PBS, the Dtxd liberation from REVS-Chi was about 60%. Mice were immunized with Dtxd encapsulated within REVs-Chi and with other REVs/Dtxd formulations adsorbed onto Freund adjuvant or alumen [AIF and Al(OH)₃]. The response patterns and the immune maturity were measured by IgG₁ and IgG_2a titrations. REVs-Chi containing Dtxd elicited both antibodies production giving the animals higher immune response and selectivity. It was interesting that the memory of those mice immunized with REVs-Chi containing Dtxd enhanced, after booster, antibody production by 47% in contrast with 17 and 7% in mice immunized with the antigen vehiculated in REVs-AIF or REVs-Al(OH)₃, respectively.     

Enhanced liposomal vaccine formulation and performance: simple physicochemical and immunological approaches

The Dtxd (Diphtheria toxoid) was the first antigen encapsulated within liposomes, their adjuvant properties were discovered (their capacity to enhance the vaccine immunogenicity). The point here is not to propose a new method to prepare this lipossomal vaccine. The central idea is to give new dresses for old vaccines by using classical and well-established liposome preparation method changing only the encapsulation pH and the immunization protocol.The most appropriate method of Dtxd encapsulation within liposome was based on lipid film hydration in 100 mM citrate buffer, pH 4.0. This was accompanied by changes on protein hydrophobicity, observed by CD and fluorescence spectroscopies. Whenever the Dtxd exposed its hydrophobic residues at pH 4.0, it interacted better with the lipossomal (observed by electrophoretic mobility) film than when its hydrophobic residues were buried (pH 9.0). The Dtxd partition coefficient in Triton-X114 and the acrylamide fluorescence quenching were also pH dependent. Both were bigger at pH 4.0 than at pH 9.0. The relationship protein structure and lipid interaction was pH dependent and now it can be easily maximized to enhance encapsulation of antigens in vaccine development.Mice were primed with formulations containing 5 mug of Dtxd within liposomes prepared in pH 4.0 or 7.0 or 9.0. The boosters were done 38 or 138 days after the first immunization. The IgM produced by immediate response of all lipossomal formulations were higher than the control (free protein). The response patterns and the immune maturity were measured by IgG1 and IgG2a titrations. The IgG1 titers produced by both formulations at pH 4.0 and 7.0 were at least 22 higher than those produced by mice injected lipossomal formulation at pH 9.0. When the boosters were done, 138 days after priming the mice produced a IgG2a titer of 29 and the group that received the booster 30 days after priming produced a titer of 25. The strongest antibody production was the neutralizing antibody (245 higher than the control) produced by those mice injected with lipossomal formulation at pH 4.0 with the booster done 138 days after priming. The simple change on lipossomal pH formulation and timing of the booster enhanced both antibody production and selectivity.     

Defective oral tolerance promotes nephritogenesis in experimental IgA nephropathy induced by oral immunization.

Oral tolerance, an important feature of the mucosal immune system, appears to protect against immune-mediated disease by blunting production of systemic IgG and IgM antibody directed toward immunogens chronically present at mucosal surfaces. In this study, we explored the role of oral tolerance and mucosal immunoregulation in an experimental model of IgA nephropathy (IgAN), an important form of nephritis in humans. Cyclophosphamide and estradiol were used to inhibit the expression of oral tolerance, which otherwise develops after chronic oral presentation of Ag. BALB/c mice given drinking water containing 0.1% bovine gamma globulin (BGG) continuously for 14 wk were randomly assigned to groups given either 2 mg of cyclophosphamide i.p., 2 mg of estradiol s.c. or both drugs. Groups of control mice received neither BGG nor drugs. In three separate experiments, a low percentage of saline-treated orally immunized mice had microscopic hematuria (0 to 20%), as did nonimmunized controls (0 to 20%). However, 58 to 83% of mice given estradiol and/or cyclophosphamide at appropriate times developed significant hematuria. If drugs were given at suboptimal times, only 25 to 56% of mice developed hematuria. Drug-treated immunized mice also had more serum IgG and IgM anti-BGG antibodies than control and saline groups. Immunofluorescence showed significantly more glomerular deposits of IgG, IgM, and C3 in drug-treated immunized mice compared to saline-treated immunized and normal untreated control mice. Hematuria and glomerular deposits of IgG, IgM, and C3 paralleled serum IgG and IgM antibody. All immunized mice showed significant mesangial IgA and BGG deposits and there were no differences in such deposits between saline- and drug-treated immunized mice. We suggest that blunting of oral tolerance with promotion of systemic IgG and IgM antibody production leads to nephritis in chronically orally immunized mice and that glomerular immune complexes containing IgG and/or IgM promote complement deposition and hematuria in IgAN. Analogous defects in oral (or more generally mucosal) tolerance could play a role in the genesis of symptomatic human IgAN.     

Protective effect of antiganglioside antibodies against experimental Trypanosoma brucei infection in mice

Liposome-associated ganglioside antigens (ganglioside GM1 or bovine brain gangliosides) were prepared to facilitate the potential protective efficacy for Trypanosoma brucei. Mice were immunized with liposome-associated ganglioside GM1 or bovine brain gangliosides intraperitoneally (i.p.). After immunization, significantly higher antigen-specific IgG and IgM antibodies were detected in sera than in the nonimmunized control group. When sera from immunized mice were analyzed for isotype distribution, antigen-specific IgG1, IgG2a, and IgG3 antibody responses were also noted. After immunization, mice were challenged i.p. with 1 x 10(2) cells of T. brucei. Sixty percentage of liposome-associated ganglioside GM1-immunized mice survived the infection, and all the mice immunized with bovine brain gangliosides-containing liposomes survived. However, all control mice died within 7 days after infection. These data demonstrate that liposomes containing ganglioside antigens have the potential usefulness for the induction of a protective immune response against T. brucei infection and suggest the possibility of developing vaccines that may ultimately be used for the prevention of trypanosomiasis.     

Glucopyranosyl Lipid Adjuvant (GLA), a Synthetic TLR4 agonist, promotes potent systemic and mucosal responses to intranasal immunization with HIVgp140

Successful vaccine development against HIV will likely require the induction of strong, long-lasting humoral and cellular immune responses in both the systemic and mucosal compartments. Based on the known immunological linkage between the upper-respiratory and urogenital tracts, we explored the potential of nasal adjuvants to boost immunization for the induction of vaginal and systemic immune responses to gp140. Mice were immunized intranasally with HIV gp140 together with micellar and emulsion formulations of a synthetic TLR4 agonist, Glucopyranosyl Lipid Adjuvant (GLA) and responses were compared to R848, a TLR7/8 agonist, or chitosan, a non TLR adjuvant. GLA and chitosan but not R848 greatly enhanced serum immunoglobulin levels when compared to antigen alone. Both GLA and chitosan induced high IgG and IgA titers in nasal and vaginal lavage and feces. The high IgA and IgG titers in vaginal lavage were associated with high numbers of gp140-specific antibody secreting cells in the genital tract. Whilst both GLA and chitosan induced T cell responses to immunization, GLA induced a stronger Th17 response and chitosan induced a more Th2 skewed response. Our results show that GLA is a highly potent intranasal adjuvant greatly enhancing humoral and cellular immune responses, both systemically and mucosally.     

超抗原SEA增强小鼠对HBV DNA 疫苗的免疫反应

观察超抗原SEA(D227A)的真核表达载体(pmSEA),对HBVDNA疫苗诱导Balbc小鼠(H2d)免疫应答的调节作用。肌内注射空载体pcDNA3、HBVDNA疫苗加pmSEA佐剂(pHBVS2S+pmSEA)或不加佐剂(pHBVS2S);ELISA法测定血清抗HBs;ELISPOT检测分泌IFNγ的脾淋巴细胞;4h51Cr释放法检测小鼠脾细胞CTL活性。HBVDNA佐剂组免疫小鼠抗HBsAg抗体滴度明显高于不加佐剂组,其IgG1IgG2a的比例不同于多肽免疫组,二者分别为0.282与10。HBVDNA佐剂组均能增强IgG1和IgG2a的产生,是不加佐剂组的1.36、1.73倍。佐剂组小鼠脾淋巴细胞IFNγ的分泌量是不加佐剂组2～3倍。CTL细胞杀伤活性(E:T=100)佐剂组与不加佐剂组分别为:69.77%±7.5%、42.81%±7.7%,差异显著(P<0.05)。HBVDNA疫苗具有较强的免疫原性,能够诱导机体产生特异性的抗体及CTL反应;pmSEA佐剂能够提高小鼠对DNA疫苗的免疫应答,有望成为DNA疫苗的免疫佐剂。     

Protection of mice from rabies by intranasal immunization with inactivated rabies virus.

The mucosal immunization method is a needle-free alternative way of vaccination. This study evaluated the efficacy of mucosal immunization for rabies. Mice were intranasally administered five times with inactivated and concentrated rabies virus antigen (CRV) supplemented with or without cholera toxin (CT). The anti-rabies virus antibody titer of mice intranasally immunized with CRV plus CT (CRV/CT) was comparable to that of mice intraperitoneally immunized twice with the same amount of CRV. Virus neutralizing (VNA) titers of mice immunized intranasally with CRV/CT were slightly lower than those of intraperitoneally immunized mice. Both anti-rabies virus ELISA antibody and VNA titers of mice immunized with CRV without CT were significantly lower than those of mice immunized with CRV/CT. In mice intranasally immunized with CRV/CT, and intraperitoneally immunized mice, high levels of IgG(2a) antibody were detected, suggesting the activation of Th1-driven cellular immunity by the two ways of immunization. All immunized mice were challenged intracerebrally with a lethal dose of virulent rabies virus CVS strain. The survival rates of mice immunized with CRV/CT and CRV without CT were 67% and 17%, respectively, while the rate of intraperitoneally immunized mice was 100%. Antigen-specific whole IgG and IgG(2a), and VNA titers of survived mice were significantly higher than those of dead mice at the challenge day. These data suggest the possibility of intranasal immunization with inactivated antigen as a rabies vaccination strategy and the importance of a mucosal adjuvant such as CT.     

A New Strategy Based on Smrho Protein Loaded Chitosan Nanoparticles as a Candidate Oral Vaccine against Schistosomiasis

Background

Schistosomiasis is one of the most important neglected tropical diseases and an effective control is unlikely in the absence of improved sanitation and vaccination. A new approach of oral vaccination with alginate coated chitosan nanoparticles appears interesting because their great stability and the ease of target accessibility, besides of chitosan and alginate immunostimulatory properties. Here we propose a candidate vaccine based on the combination of chitosan-based nanoparticles containing the antigen SmRho and coated with sodium alginate.

Methods and Findings

Our results showed an efficient performance of protein loading of nanoparticles before and after coating with alginate. Characterization of the resulting nanoparticles reported a size around 430 nm and a negative zeta potential. In vitro release studies of protein showed great stability of coated nanoparticles in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). Further in vivo studies was performed with different formulations of chitosan nanoparticles and it showed that oral immunization was not able to induce high levels of antibodies, otherwise intramuscular immunization induced high levels of both subtypes IgG1 and IgG2a SmRho specific antibodies. Mice immunized with nanoparticles associated to CpG showed significant modulation of granuloma reaction. Mice from all groups immunized orally with nanoparticles presented significant levels of protection against infection challenge with S. mansoni worms, suggesting an important role of chitosan in inducing a protective immune response. Finally, mice immunized with nanoparticles associated with the antigen SmRho plus CpG had 38% of the granuloma area reduced and also presented 48% of protection against of S. mansoni infection.

Conclusions

Taken together, this results support this new strategy as an efficient delivery system and a potential vaccine against schistosomiasis.     

Effect of orally administered non-viable Lactobacillus cells on murine humoral immune responses

BALB/c mice were immunized intraperitoneally with the food antigen ovalbumin (OVA) while they were fed with Lactobacillus GG heated killed cell preparation. The oral administration of Lactobacillus GG did not appear to modify the antigen-augmented serum IgE in the tested mice but significantly augmented serum OVA specific IgG in the tested mice fed with a diet containing 0.1% Lactobacillus GG as the non-viable cell preparation (P< 0.05). The fecal OVA specific IgA of the tested mice fed with nonviable Lactobacillus GG cells was also significantly elevated (P< 0.05) compared to those from OVA immunized mice. The spleen cells of mice fed with non-viable Lactobacillus GG cells secreted more IL-6 (P< 0.01). These results suggest that the non-viable Lactobacillus GG can augment the systemic and mucosal immune responses in a host animal favoring secretory IgA but not IgE in an adjuvant-like manner.     

Oral immunization of mice with Japanese encephalitis virus envelope protein synthesized in Escherichia coli induces anti-viral antibodies

In order to evaluate the possibility of developing an oral vaccine against Japanese encephalitis virus (JEV), mice were fed with recombinant JEV envelope (E) protein synthesized in Escherichia coli. The protein was administered orally to mice with or without an immunostimulatory cytosine-phosphate-guanosine (CpG) motif containing synthetic oligodeoxynucleotide (ODN) as an adjuvant. The immunized mice made high-titered anti-E and anti-JEV antibodies. Mice immunized with JEV E protein along with the ODN adjuvant produced higher antibody titers and these were predominantly IgG2a type. These antibodies, however, failed to neutralize JEV activity in vitro, and the immunization did not protect the mice against lethal JEV challenge. Splenocytes from the immunized mice secreted large amounts of interferon (IFN)-gamma and showed proliferation in the presence of JEV E protein. Our results indicate that JEV E protein delivered orally to mice together with ODN generated both humoral and cellular immune responses to JEV, and these were of the Th1 type.     

Vaccination of mice with a 30 kDa Schistosoma antigen with and without human adjuvant induces high protection against S. mansoni infection

A 30 kDa antigen was characterized as a hydrophobic polypeptide containing 16 amino acids and evaluated as a potential candidate vaccine against infection by Schistosoma mansoni. CD1 albino mice immunized at 0, 14, and 21 days with 25 or 50 microg of the 30 kDa antigen per mouse with and without alum developed high levels of IgG antibodies (predominantly IgG2a and IgG2b isotypes). When immunized mice were infected with 200 S. mansoni cercariae, the highest protection levels (61% and 65% reduction in worm burden in two separate experiments) were obtained using the 50-microg antigen without alum adjuvant. The granuloma size decreased to 10%, a non-significant level in mice immunized using alum adjuvant. The results demonstrate the ability of the 30 kDa antigen with and without alum adjuvant to protect mice against S. mansoni infection.     

The role of liposome charge on immune response generated in BALB/c mice immunized with recombinant major surface glycoprotein of Leishmania (rgp63)

Liposomes as a lipid-based system have been shown to be an effective adjuvant formulation. In this study, the role of liposome charge in induction of a Th1 type of immune response and protection against leishmaniasis in BALB/c mice was studied. Liposomes containing rgp63 were prepared by Dehydration-Rehydration Vesicle (DRV) method. Neutral liposomes consisted of dipalmitoylphosphatidylcholine and cholesterol. Positively and negatively charged liposomes were prepared by adding dimethyldioctadecylammonium bromide (DDAB) or dicetyl phosphate (DCP) to the neutral liposome formulation, respectively. Female BALB/c mice were immunized subcutaneously with negatively, positively charged or neutral liposomes encapsulated with rgp63, rgp63 in soluble form or PBS, three times in 3 week intervals. The extent of protection and type of immune response generated were studied in different groups of mice. The group of mice immunized with rgp63 encapsulated in neutral liposomes showed a significantly (P < 0.01) smaller footpad swelling upon challenge with Leishmania major compared with positively or negatively charged liposomes. The mice immunized with neutral liposomes also showed a significantly (P < 0.01) the lowest splenic parasite burden, the highest IgG2a/IgG1 ratio and IFN-γ production and the lowest IL-4 level compared to the other groups. The results indicated that a Th1 type of immune response was induced in mice immunized with neutral liposomes more efficiently than positively charged liposomes and conversely negatively charged liposomes induced a Th2 type of immune response.     

Expression and Immunogenicity of Enterotoxigenic <Emphasis Type="Italic">Escherichia</Emphasis> <Emphasis Type="Italic">coli</Emphasis> Heat-Labile Toxin B Subunit in Transgenic Rice Callus

Enterotoxigenic Escherichia coli is one of the leading causes of diarrhea in developing countries, and the disease may be fatal in the absence of treatment. Enterotoxigenic E. coli heat-labile toxin B subunit (LTB) can be used as an adjuvant, as a carrier of fused antigens, or as an antigen itself. The synthetic LTB (sLTB) gene, optimized for plant codon usage, has been introduced into rice cells by particle bombardment-mediated transformation. The integration and expression of the sLTB gene were observed via genomic DNA PCR and western blot analysis, respectively. The binding activity of LTB protein expressed in transgenic rice callus to G_M1-ganglioside, a receptor for biologically active LTB, was confirmed by G_M1-ELISA. Oral inoculation of mice with lyophilized transgenic rice calli containing LTB generated significant IgG antibody titers against bacterial LTB, and the sera of immunized mice inhibited the binding of bacterial LTB to G_M1-ganglioside. Mice orally immunized with non-transgenic rice calli failed to generate detectable anti-LTB IgG antibody titers. Mice immunized with plant-produced LTB generated higher IgG1 antibody titers than IgG2a, indicating a Th2-type immune response. Mice orally immunized with lyophilized transgenic rice calli containing LTB elicited higher fecal IgA antibody titers than mice immunized with non-transgenic rice calli. These experimental results demonstrate that LTB proteins produced in transgenic rice callus and given to mice by oral administration induce humoral and secreted antibody immune responses. We suggest that transgenic rice callus may be suitable as a plant-based edible vaccine to provide effective protection against enterotoxigenic E. coli heat-labile toxin.     

DNA immunization with Plasmodium falciparum serine repeat antigen: regulation of humoral immune response by coinoculation of cytokine expression plasmid

We immunized mice with plasmid expressing the 47-kDa amino-terminal domain of the Plasmodium falciparum serine repeat antigen (SERA) using gene gun and investigated humoral immune response to SERA antigen. Significant SERA-specific IgG was observed in BALB/c mice after immunization three times with SERA expression plasmid. Furthermore, these levels were increased by the coinoculation of cytokine (IFN-gamma, IL-4, GM-CSF, or IL-12) expression plasmid. In respect to the SERA-specific Ig subclasses, coinoculation of IFN-gamma, GM-CSF, or IL-12 expression plasmid increased the levels of SERA-specific IgG2a, and these were much higher than that in mice immunized with SERA expression plasmid alone. In contrast to the SERA-specific IgG2a, coinoculation of any cytokine expression plasmid did not change the levels of SERA-specific IgG1. These results indicate that cytokine expression plasmid enhances and regulates humoral immune response elicited by SERA DNA immunization.     

Partial Protective Effect of Intranasal Immunization with Recombinant Toxoplasma gondii Rhoptry Protein 17 against Toxoplasmosis in Mice

Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite that infects a variety of mammals, including humans. An effective vaccine for this parasite is therefore needed. In this study, RH strain T. gondii rhoptry protein 17 was expressed in bacteria as a fusion with glutathione S-transferase (GST) and the recombinant proteins (rTgROP17) were purified via GST-affinity chromatography. BALB/c mice were nasally immunised with rTgROP17, and induction of immune responses and protection against chronic and lethal T. gondii infections were investigated. The results revealed that mice immunised with rTgROP17 produced high levels of specific anti-rTgROP17 IgGs and a mixed IgG1/IgG2a response of IgG2a predominance. The systemic immune response was associated with increased production of Th1 (IFN-γand IL-2) and Th2 (IL-4) cytokines, and enhanced lymphoproliferation (stimulation index, SI) in the mice immunised with rTgROP17. Strong mucosal immune responses with increased secretion of TgROP17-specific secretory IgA (SIgA) in nasal, vaginal and intestinal washes were also observed in these mice. The vaccinated mice displayed apparent protection against chronic RH strain infection as evidenced by their lower liver and brain parasite burdens (59.17% and 49.08%, respectively) than those of the controls. The vaccinated mice also exhibited significant protection against lethal infection of the virulent RH strain (survival increased by 50%) compared to the controls. Our data demonstrate that rTgROP17 can trigger strong systemic and mucosal immune responses against T. gondii and that ROP17 is a promising candidate vaccine for toxoplasmosis.     

新型呼肠病毒 S基因 DNA 疫苗在小鼠体内的免疫原性

目的：探讨新型呼肠病毒R4株S片段免疫小鼠后引发的免疫应答。方法构建4个不同S基因节段的重组真核表达质粒,并免疫小鼠;ELISA检测血清以研究R4特异性抗体升高水平,并对其抗体亚型进行鉴定;ELISPOT检测小鼠淋巴细胞INF-γ的表达情况。结果与对照组相比,4个重组质粒免疫的小鼠血清都有明显的R4特异性抗体升高,尤其以S1和S3基因免疫后抗体水平较高,且均以IgG2a占绝对优势;S1基因免疫组小鼠的细胞免疫应答最强。结论 S1基因重组质粒免疫小鼠后可同时引发较强的体液免疫和细胞免疫应答,是较为理想的疫苗备选基因片段。     

<Emphasis Type="Italic">Brucella abortus</Emphasis> phosphoglyceromutase and dihydrodipicolinate reductase induce Th1 and Th2-related immune responses

Brucellae are intracellular bacterial pathogens that cause Brucellosis, bringing great economic burdens to developing countries. The pathogenic mechanisms of Brucella are still poorly understood. Earlier immune response plays an important role in the Brucella infection. Phosphoglyceromutase (PGM) and dihydrodipicolinate reductase (DapB) were cloned, expressed, purified, and their immunocompetence was analyzed. Cytokines were detected by murine macrophages (RAW 264.7) and splenocytes that stimulated with the two recombinant proteins. The immune responses were analyzed by ELISA from mice with the two recombinant proteins immunized. TNF-α, IL-6 and IL-8 were produced in stimulated RAW 264.7 cells and splenocytes. Th1-type cytokines, IFN-γ and IL-2, induced in RAW 264.7 cells and splenocytes were higher then Th2-type cytokines, IL-4 and IL-5. Th2-related immune response was induced in splenocytes obtained 35 days after mice immunized with the two proteins. The production of IgG1 was higher than IgG2a in immunized mice. Taken together, our results demonstrated that the two proteins could induce Th1 and Th2-type immune responses in vivo and in vitro.     

Intrarectal immunization with rotavirus 2/6 virus-like particles induces an antirotavirus immune response localized in the intestinal mucosa and protects against rotavirus infection in mice

Rotavirus (RV) is the main etiological agent of severe gastroenteritis in infants, and vaccination seems the most effective way to control the disease. Recombinant rotavirus-like particles composed of the viral protein 6 (VP6) and VP2 (2/6-VLPs) have been reported to induce protective immunity in mice when administered by the intranasal (i.n.) route. In this study, we show that administration of 2/6-VLPs by the intrarectal (i.r.) route together with either cholera toxin (CT) or a CpG-containing oligodeoxynucleotide as the adjuvant protects adult mice against RV infection. Moreover, when CT is used, RV shedding in animals immunized by the i.r. route is even reduced in comparison with that in animals immunized by the i.n. route. Humoral and cellular immune responses induced by these immunization protocols were analyzed. We found that although i.r. immunization with 2/6-VLPs induces lower RV-specific immunoglobulin G (IgG) and IgA levels in serum, intestinal anti-RV IgA production is higher in mice immunized by the i.r. route. Cellular immune response has been evaluated by measuring cytokine production by spleen and Peyer's patch cells (PPs) after ex vivo restimulation with RV. Mice immunized by the i.n. and i.r. routes display higher gamma interferon production in spleen and PPs, respectively. In conclusion, we demonstrate that i.r. immunization with 2/6-VLPs protects against RV infection in mice and is more efficient than i.n. immunization in inducing an anti-RV immune response in intestinal mucosa.     

Nasal inoculation of an adenovirus vector encoding 11 tandem repeats of Abeta1-6 upregulates IL-10 expression and reduces amyloid load in a Mo/Hu APPswe PS1dE9 mouse model of Alzheimer's disease

BACKGROUND: One of the pathological hallmarks of Alzheimer's disease (AD) is deposits of amyloid beta-peptide (Abeta) in neuritic plaques and cerebral vessels. Immunization of AD mouse models with Abeta reduces Abeta deposits and improves memory and learning deficits. Because recent clinical trials of immunization with Abeta were halted due to brain inflammation that was presumably induced by a T-cell-mediated autoimmune response, vaccination modalities that elicit predominantly humoral immune responses are currently being developed. METHODS: We have nasally immunized a young AD mouse model with an adenovirus vector encoding 11 tandem repeats of Abeta1-6 fused to the receptor-binding domain (Ia) of Pseudomonas exotoxin A (PEDI), AdPEDI-(Abeta1-6)(11), in order to evaluate the efficacy of the vector in preventing Abeta deposits in the brain. We also have investigated immune responses of mice to AdPEDI-(Abeta1-6)(11). RESULTS: Nasal immunization of an AD mouse model with AdPEDI-(Abeta1-6)(11) elicited a predominant IgG1 response and reduced Abeta load in the brain. The plasma IL-10 level in the AD mouse model was upregulated after immunization and, upon the stimulation with PEDI-(Abeta1-6)(11), marked IL-10 responses were found in splenic CD4(+) T cells from C57BL/6 mice that had been immunized with AdPEDI-(Abeta1-6)(11). CONCLUSIONS: These results suggest that the induction of Th2-biased responses with AdPEDI-(Abeta1-6)(11) in mice is mediated in part through the upregulation of IL-10, which inhibits activation of dendritic cells that dictate the induction of Th1 cells.