Comparative efficacy of the Schistosoma mansoni nucleic acid vaccine,Sm23, following microseeding or gene gun delivery

Sm23 is an integral membrane protein expressed widely in the human parasitic worm Schistosoma mansoni. Sm23 has already been shown to elicit protective immune responses following immunization with peptides or DNA constructs. In this study, we evaluated the immunogenicity and the protective efficacy of the Sm23 DNA vaccine using two different intradermal DNA delivery methods: microseeding and gene gun. Using both techniques, all mice immunized with the Sm23-pcDNA construct generated Sm23-specific immunoglobulin (Ig)G antibody, while mice immunized with the control plasmid, pcDNA, did not. Antibody isotypes analysis revealed that microseeding elicited mainly IgG2a and IgG2b antibodies, with relatively low levels of IgG1 and IgG3. The relative IgG1/IgG2a ratio was 0.03, indicative of a Th1 type immune response. In contrast, gene gun immunization resulted in significantly higher levels of IgG1 and IgG3. The relative IgG1/IgG2a ratio in this case was 11, indicative of a Th2 type immune response. No significant difference in the levels of IgG2b was observed. Coimmunization with plasmid DNA encoding either interleukin (IL)-12 or IL-4 by microseeding did not affect the levels of IgG1, while the levels of IgG2a and IgG2b were reduced. On the other hand, the levels of IgG3 were significantly increased by IL-4, but unchanged by IL-12. Importantly, in all experiments, the Sm23-pcDNA vaccine provided statistically significant levels of protection against challenge infection. Microseeding immunizations resulted in higher levels of protection (31-34% protection) than gene gun immunization (18% protection). This suggests that the Th1 type immune response elicited by microseeding immunization was responsible for the higher protection levels. However, the protective effect of the vaccine was not affected by coadministering plasmids encoding either IL-12 or IL-4 using the microseeding technique.     

Analysis of the immune response elicited by a Multiple Antigen Peptide (MAP) composed of two distinct protective antigens derived from the parasite Schistosoma mansoni

In this report we analyse the immune response elicited by a Multiple Antigen Peptide (MAP), containing three peptide sequences derived from two distinct vaccine candidates against schistosomiasis; the Schistosoma mansoni 28 kDa Gluthatione-S-Transferase (Sm28GST) and the Schistosoma mansoni Triose-Phosphate-Isomerase (sTPI). We examined the immunogenicity of this construct, named MAP 'DA', in three distinct mouse strains. The B-cell response, studied by measuring the production of different IgG isotypes, was mainly directed against the peptide derived from the Sm28GST, but also against the whole Sm28GST protein. In contrast, the T-cell response, as assessed by proliferation assay and cytokine mRNA expression, was directed against the MAP construct, the peptides derived from the sTPI protein and the whole sTPI protein. Significantly, T-cells from all MAP 'DA'-immunized mice, restimulated in vitro was the sTPI antigen, expressed IFN-γ specific messengers. This cytokine has been described to play a major role in the reduction of the Schistosoma mansoni pathology. We thus demonstrate that a single MAP construct, composed of peptides from distinct antigens of Schistosoma mansoni , induced a B- and T-cell response, including production of potentially protective IFN-γ, irrespective of the MHC background.     

Egg-hatching inhibition in mice immunized with recombinant Schistosoma bovis 28 kDa glutathione S-transferase

The capacity of a recombinant glutathione S-transferase from Schistosoma bovis (rSb 28GST) to protect BALB/c mice against homologous and heterologous infections with, respectively, S. bovis or Schistosoma mansoni has been studied. Two injections of the rSb 28GST and an intravenous boost resulted in a marked specific IgG response on the day of experimental challenge with S. bovis or S. mansoni cercariae. Immunization of BALB/c mice led to a reduction in egg maturation and egg viability after infection with S. bovis or S. mansoni. Adult worm recoveries after an S. bovis challenge infection and tissue egg densities (intestine and liver) in S. mansoni challenge infection were also reduced in the immunized groups, but these differences were not statistically significant. No association between in vitro inhibition of GST enzymatic activity induced by immunized mouse sera and worm burden reduction was recorded. The analysis of the immune response, on the day of perfusion, showed the production of immunoglobulin (Ig)G1, IgG2a and IgG2b specific antibodies and the production of interleukin (IL)-4 and IL-5 by spleen cells after rSb 28GST stimulation. These data suggest that rSb 28GST immunization induces a moderate effect upon egg maturation and egg hatching, suggesting the involvement of similar mechanisms of action and common, but not exclusive, targets during S. bovis and S. mansoni infections. As a consequence, immunization with rSb 28GST may prove useful in affecting the pathology and transmission of African schistosomes.     

Sex-dependent neutralizing humoral response to Schistosoma mansoni 28GST antigen in infected human populations

The reduction of Schistosoma fecundity observed after experimental vaccination with the Schistosoma mansoni 28-kDa glutathione S-transferase (Sm28GST) antigen has been related to the inhibition of glutathione S-transferase (GST) enzymatic activity by specific antibody. The humoral immune response to the protective antigen Sm28GST and to the epitopes involved in the enzymatic site (amino acid ?aa sequences 10-43 and 190-211) was evaluated in infected individuals before chemotherapy treatment. The capacity of the serum samples to inhibit GST enzymatic activity was assessed. Specific IgG3 response was predominant in the male population with a low intensity of infection and was associated with maximal GST inhibition. In contrast, the neutralizing activity of serum samples from women with a low intensity of infection was correlated with high specific IgA response specifically directed toward the 190-211 epitope. These results strongly support the hypothesis that GST-neutralizing IgG3 and IgA isotypes are sex dependent. The relationship of this specific acquired immune response with the level of intensity of infection is discussed.     

Induction of immunity in mice to Fasciola hepatica with a Fasciola/Schistosoma cross-reactive defined immunity antigen

The paradox of schistosomiasis is that infection confers immunity to its host, yet immunization with subcellular antigens of the parasite does not, in general, induce protective immunity. Infection or immunization with subcellular antigens of Fasciola hepatica confers high levels of immunity to a challenge infection with another trematode, Schistosoma mansoni. We have isolated by antibody affinity chromatography a Fasciola hepatica/Schistoma mansoni cross-reactive antigen, designated FhSmIII(M), and also have shown that this antigen confers immunity in mice to a challenge infection with S. mansoni. This antigen was compared with a crude F. hepatica worm extract (FhWWE) as to its ability to induce an IgG antibody response in mice, and to determine whether it had a protective effect in mice to a challenge infection with F. hepatica metacercariae. Mice immunized with FhSmIII(M) or FhWWE, and subsequently infected with F. hepatica, developed higher IgG antibody levels to FhSmIII(M), as measured by ELISA, than F. hepatica-infected controls. Mice immunized with FhWWE did not develop significant levels of resistance to challenge with F. hepatica metacercariae. Mice immunized with FhSmIII(M) and infected with F. hepatica metacercariae developed 69%-78% less worms than controls. An F. hepatica/S. mansoni cross-reactive, cross-protective defined immunity antigen confers in mice significant levels of protection to a challenge infection with F. hepatica.     

Immunization of mice and baboons with the recombinant Sm28GST affects both worm viability and fecundity after experimental infection with Schistosoma mansoni

A member of the glutathione S-transferase family, Sm28GST has previously demonstrated a good ability to protect rodents against experimental infection with Schistosoma mansoni. In order to evaluate its efficacy in a model closer to man, two different protocols of immunization with recombinant Sm28GST were tested on baboons in a large-scale trial. Three injections in the presence of aluminium hydroxide as adjuvant resulted in a significant 38% reduction in the adult worm burden together with a trend for a lower percentage of inflammatory tissue in the liver. Individual levels of protection, ranging from 0 to 80%, underlined the heterogeneity of the immune response to this purified molecule in outbred primates. On the other hand, two injections of Sm28GST in the presence of aluminium hydroxide and Bordetella pertussis reduced female schistosome fecundity by 33%, with a more pronounced effect (66%) on faecal egg output; there was also a trend, in this protocol, for decrease of the mean granuloma surface in the liver. Individual anti-Sm28GST IgG antibodies were apparently unrelated to levels of immunity, but there was partial evidence that cytophilic IgE might play a role in the immune mechanisms affecting worm viability, but not fecundity. In the mouse model, Sm28GST vaccination resulted in a lower hatching ability of tissue eggs recovered from immunized mice whereas passive transfer of specific anti-Sm28GST T-lymphocytes, one day before infection, significantly reduced the number of eggs in the liver of mice. We propose that different protocols of immunization with a recombinant molecule can impede Schistosoma mansoni worm viability and fecundity, but can also affect miracidium physiology, with important consequences for disease transmission and granuloma-derived pathology.     

Construction of a Eukaryotic Plasmid Encoding Bacillus anthracis Protective Antigen,a Candidate for DNA Vaccine

Background: DNA immunization with plasmid DNA encoding bacterial, viral, parasitic and tumor antigens has been reported to trigger protective immunity. Objective: To evaluate the use of a DNA immunization strategy for protection against anthrax, a plasmid was constructed. Methods: The partialsequence of protective antigen of Bacillus anthracis, amino acids 175-764, as a potent immunogenic target was selected. The DNA encoding this segment was utilized in the construction of pcDNA3.1+PA plasmid. After intramuscular injection of rats with pcDNA3.1+PA plasmid, the expression of PA was assessed by RT-PCR and immunohistochemistry at RNA and protein levels, respectively. We also evaluated the presence of anti-PA antibodies in sera of immunized mice with pcDNA3.1+PA construct using immunoblotting. Results: The integrity of pcDNA3.1+PA construct was confirmed with restriction analysis and sequencing. The expression of PA was detected at RNA and protein levels. The presence of anti-PA antibodies in immunized mice with pcDNA3.1+PA construct was also confirmed. Conclusion: Our results indicate that pcDNA3.1+PA eukaryotic expressing vector could express PA antigen, induce antibody response and may be used as a candidate for DNA vaccine against anthrax.     

弓形虫P30基因重组质粒的构建及其免疫效果

目的　通过构建含弓形虫P30不同表达形式 (膜型、分泌型及细胞内型 )的重组质粒 ,并将其用于免疫小鼠 ,测定抗体水平 ,以期初步筛选出一种对弓形虫感染具有良好保护作用的核酸疫苗。　方法　利用PCR技术和亚克隆技术分别构建弓形虫表膜型P30基因重组质粒 (含完整的P30编码序列 ,包括信号肽及疏水尾 )pcDNA3 P30Mb ,分泌型P30基因重组质粒 (含完整的P30编码序列 ,不包括疏水尾 )pcDNA3 P30Se以及细胞内型P30基因重组质粒 (含完整的P30编码序列 ,但不包括信号肽 )pcDNA3 P30In。将以上 3种重组质粒分别与脂质体混合后免疫小鼠 ,ELISA及免疫印迹测定小鼠血清中特异的IgG抗体。　结果　成功构建了弓形虫P30基因 3种表达形式的重组质粒 ,经双酶切鉴定及DNA序列测定 ,3种重组质粒中的插入片段确为P30的编码基因 ,且读码框架正确 ;抗体测定显示 :3个免疫组均能诱导小鼠产生特异的IgG抗体 ,但各组之间IgG出现的时间及强度有一定的差异。　结论　用编码弓形虫P30抗原的重组质粒进行核酸免疫 ,能诱导免疫小鼠产生特异性的IgG抗体 ;膜型及分泌型免疫小鼠的特异IgG抗体出现的时间早于细胞内型免疫鼠 ,但 4wk后 3组间差异无显著性。     

Nasal immunization of mice with Cryptosporidium parvum DNA induces systemic and intestinal immune responses

DNA immunization offers a novel approach to inducing humoral and cellular immunity against infectious pathogens. We examined whether such an approach could be used against cryptosporiodiosis, an intestinal disease caused by the protozoan parasite Cryptosporidium parvum. This infection is a major problem for young ruminants and immunosuppressed individuals in whom cryptosporidiosis causes life-threatening symptoms. The life cycle of C. parvum takes place in the enterocytes of the intestinal epithelium. We therefore focused our attention on a route of immunization that might induce a mucosal immunoglobulin (Ig)A response. Eight-week-old BALB/c mice were immunized intranasally with DNA encoding a 15-kDa C. parvum sporozoite antigen (CP15-DNA) cloned onto the plasmid pcDNA3. CP15-DNA-immunized mice developed specific and longlasting production of anti-CP15 Ig A in intestinal secretions and specific IgG in sera 3 months and 1 year after the first DNA inoculation. CP15-DNA-immunized mice also developed an antigen-specific T lymphocyte proliferative response in both spleen and mesenteric lymph nodes. Control mice that received the pcDNA3 plasmid alone did not develop specific humoral and cellular responses. These results indicate that plasmid DNA may provide a powerful means of eliciting intestinal humoral and cellular responses to C. parvum infections in mammals.     

Protection against malaria by immunization with plasmid DNA encoding circumsporozoite protein.

Immunization with irradiated sporozoites protects animals and humans against malaria, and the circumsporozoite protein is a target of this protective immunity. We now report that adjuvant-free intramuscular injection of mice with plasmid DNA encoding the Plasmodium yoelii circumsporozoite protein induced higher levels of antibodies and cytotoxic T lymphocytes against the P. yoelii circumsporozoite protein than did immunization with irradiated sporozoites. Mice immunized with this vaccine had an 86% reduction in liver-stage parasite burden after challenge with 5 x 10(5) sporozoites (> 10(5) median infectious doses). Eighteen (68%) of 28 mice that received two or three doses of vaccine were protected against challenge with 10(2) sporozoites, and the protection was dependent on CD8+ T cells. These studies demonstrate the utility of plasmid DNA immunization against a nonviral infection. By obviating the requirement for peptide synthesis, expression and purification of recombinant proteins, and adjuvants, this method of immunization provides an important alternative for rapid identification of protective B- and T-cell epitopes and for construction of vaccines to prevent malaria and other infectious diseases.     

Immune response in susceptible BALB/c mice immunized with DNA encoding Lipophosphoglycan 3 of Leishmania infantum

Visceral leishmaniasis is a serious parasitic infection that the development of an effective vaccine is necessary to control the disease. Lipophosphoglycan 3 (LPG3) is essential for the synthesis of glycoconjugates as parasite virulence factors. In this study, we evaluated the immunogenicity of Leishmania infantum LPG3 gene as a DNA vaccine against murine visceral leishmaniasis. For this purpose, BALB/c mice were immunized subcutaneously with the DNA encoding LPG3 either alone or in combination with recombinant heat shock protein 70 (rHSP70). Next, its immunogenicity and protective efficacy were evaluated in the immunized mice. The results showed a mixed Th1/Th2 response following immunization, which was associated with the production of both IFN‐γ and IL‐10 by splenocytes compared with control groups but did not lead to reduction in the splenic parasite burden. Serum levels of IgG antibody isotypes indicated no significant difference between the LPG3 DNA and the empty vector. In addition, the co‐administration of rHSP70 with the DNA vaccine offered no additive protective advantage on experimental infectious challenge. Thus, we propose to strengthen the immunogenic potential of L. infantum LPG3 in prime‐boost approach with a powerful adjuvant to elicit a robust parasite‐specific protective Th1 response.     

Protective and therapeutic effect of DNA-based immunization against hepadnavirus large envelope protein

BACKGROUND & AIMS: Studies in the murine model suggest that injection of DNA encoding hepatitis B virus structural proteins is promising for the induction of a specific immune response. We used the duck hepatitis B virus (DHBV) model to study the protective and therapeutic effects of naked DNA immunization against hepadnaviral large envelope protein. METHODS: A pCI-preS/S plasmid expressing the DHBV large protein was used for intramuscular immunization of ducks. The humoral response was tested by enzyme-linked immunosorbent assay, immunoblotting, neutralization, and in vivo protection tests. For DNA therapy, DHBV-carrier ducks received four injections of this plasmid. Viremia was monitored for 10 months; thereafter, liver biopsies were performed. RESULTS: Immunization with pCI-preS/S plasmid induced a specific, long-lasting, neutralizing, and highly protective anti-preS humoral response in uninfected animals. After pCI-preS/S treatment, a significant and sustained decrease in serum and liver DHBV DNA was observed for carrier ducks compared with the controls. CONCLUSIONS: DNA immunization against DHBV large protein results in a potent and protective anti-preS response in the duck model. The results of long-term follow-up of DNA-treated chronically infected ducks are promising and show the usefulness of this model for the study of genetic immunization in chronic hepatitis B therapy.     

细粒棘球绦虫Eg95基因疫苗和重组抗原诱导小鼠免疫应答的比较研究

目的观察比较细粒棘球绦虫Eg95重组抗原和基因疫苗诱导小鼠的免疫应答状况。方法实验组和对照组小鼠分别注射Eg95重组抗原(rEg95)、费氏佐剂(FCA)、pcDNA3-Eg95基因疫苗、pcDNA3质粒和生理盐水,收集各组血清用酶联免疫吸附(ELISA法)检测抗体IgG和IgG2a亚类水平;采集脾细胞用四甲基偶氮唑盐试验(MTT法)检测免疫小鼠的脾淋巴细胞增殖反应。结果rEg95免疫组小鼠在第二次免疫后开始检测到抗Eg95抗原的IgG,并随着免疫次数的增多,血清抗体效价升高,在第1次免疫后第10周时,免疫抗体滴度可达到1∶25,600。Eg95基因疫苗免疫的小鼠产生抗体滴度随免疫次数的增加而升高,最高可达1∶3,200,但是低于Eg95重组蛋白免疫小鼠产生的抗体滴度水平。pcDNA3-Eg95免疫组产生IgG2a亚类抗体水平明显高于对照组和rEg95组。在第四次免疫后,进行淋巴细胞转化试验,MTT法检测证实rEg95和pcD-NA3-Eg95免疫的小鼠,其脾细胞均可在体外被特异性刺激增生。结论细粒棘球绦虫Eg95重组抗原和基因疫苗均可诱发小鼠产生特异性免疫应答。     

Comparison of Schistosoma mansoni irradiated cercariae and Sm23 DNA vaccines

Immunization with defined antigens is generally less effective at inducing host protection against experimental infection with Schistosoma mansoni than vaccination with attenuated infective cercariae. We predicted that quantitative and/or qualitative differences existed between the immune responses generated to attenuated cercariae and those induced by defined antigens. Thus, we compared immune responses typically associated with protection in the murine model between animals vaccinated with attenuated cercariae and mice immunized with DNA encoding Sm23, a schistosome integral membrane protein that has previously been shown to confer protection. Mice vaccinated three times with attenuated cercariae demonstrated higher levels of protection than Sm23-vaccinated animals but spleen cells from Sm23 DNA vaccinated mice produced significantly higher levels of schistosome antigen-specific IFN-gamma. Both vaccines induced similar levels of Sm23-specific antibody and post-challenge dermal inflammation. However, the pulmonary inflammatory responses following challenge were much less pronounced in DNA immunized animals compared to those receiving irradiated cercariae. Thus, although Sm23 DNA vaccination effectively induced parasite-specific IFN-gamma and antibody responses, it failed to evoke other critical responses needed for optimal vaccine efficacy.     

Vaccination of patas monkeys experimentally infected with Schistosoma haematobium using a recombinant glutathione S-transferase cloned from S. mansoni

The capacity of a recombinant glutathione S-transferase from Schistosoma mansoni (rSm28GST) to vaccinate primates fErythrocebus patas,) against a heterologous infection with Schistosoma haematobium has been tested. Two injections of the purified molecule with Muramyl-Di-Peptide (MDP) as adjuvant resulted in a high level antibody response in the five immunized animals and in a significant reduction in worm fecundity compared to the controls which received adjuvant alone. Mean levels of daily egg excretion in urine and faeces were reduced by respectively 55% and 74% although perfusion revealed that worm burdens were similar in both groups. The protective effect was long lasting since it was maintained up to the end of the experiment, 42 weeks after infection. Hatching rates and the numbers of intra-uterine eggs were also significantly affected by the vaccination. Tissue eggs were also drastically diminished in the urogenital system (–80%) but the reduction was not statistically significant. One animal was not protected by the immunization. There was a good correlation between parasitological data and the intensity of bladder lesions assessed by microscopic examination. Polypoid formations together with an intense exudation of the lamina propria were frequently seen in the controls but rarely in the vaccinated group where formation of scar tissue was predominant. These results underline the vaccine potential of the recombinant Sm28GST as a possible valuable prophylactic tool for the control of egg-induced pathology and transmission of African schistosomes.     

Factors associated with resistance to Schistosoma mansoni infection in an endemic area of Bahia, Brazil

Detailed knowledge of factors associated with resistance to Schistosoma mansoni infection in endemic areas might facilitate more effective schistosomiasis control. We conducted a cross-sectional study of persons resistant to schistosomiasis and found no association between socioeconomic status and resistance to infection. Mononuclear cells of resistant subjects produced higher levels of interleukin-5 (IL-5), IL-13 and interferon-γ upon stimulation with soluble egg antigen (SEA) compared with infected persons. When stimulated with Sm21.6 or Sm22.6, levels of IL-10 were higher in cell culture of resistant persons. Levels of IgE against soluble adult worm antigen (SWAP) and against interleukin-4-inducing principle from S. mansoni eggs (IPSE) and levels of IgG4 against SWAP, SEA, and Sm22.6 were lower in the resistant group compared with the susceptible group. Our data suggest that socioeconomic status could not fully explain resistance to S. mansoni infection observed in the studied area. However, a mixture of Th1 and Th2 immune responses and low levels of specific IgG4 against parasite antigens could be mediating resistance to infection.     

Cell-mediated and humoral immune responses in capuchin monkeys infected with Schistosoma japonicum or Schistosoma mansoni

Cell-mediated immune responses, assessed by lymphocyte clonal expansion in vitro, as well as humoral responses, assessed by an enzyme-linked immunosorbent assay (ELISA), were evaluated in capuchin monkeys during a 7-month infection with Schistosoma mansoni or with a Japanese or Philippine strain of Schistosoma japonicum. Although mounting a vigorous antibody response against parasite antigens, the S. mansoni-infected monkeys failed to show lymphocyte proliferation in response to stimulation with soluble adult worm antigen or soluble egg antigen derived from S. mansoni. Monkeys infected with S. japonicum responded to parasite antigens obtained from S. japonicum both by antibody production and lymphocyte blastogenesis. Monkeys infected with S. japonicum (Japanese strain) never developed detectable levels of circulating immune complexes (CIC). On the other hand high levels of CIC appeared at 7 months of infection in the monkeys infected with S. mansoni. The CIC levels exhibited negative correlations with intensity of infection. In studies of antigen species specificity, sera from S. mansoni-infected monkeys showed much higher IgG antibody titers to antigens derived from S. mansoni than to S. japonicum-derived antigens. On the other hand, monkeys infected with S. japonicum had comparable IgG antibody titers to antigens of both schistosome species.     

DNA immunization by intramuscular injection or gene gun induces specific IgG antibodies against a Schistosoma japonicum 22 kDa antigen, Sj22, when fused to the murine Ig K-chain secretory leader sequence

The 22 kDa tegumental surface membrane-associated antigen of Schistosoma japonica, Sj22, is of recognized interest in schistosomiasis vaccine research. However, previous attempts to induce antibody responses against Sj22 by DNA immunization have been unsuccessful. In this report we demonstrate that fusing the Sj22 cDNA to the murine immunoglobulin Ig kappa-chain secretory leader sequence results in the generation of antigen-specific IgG antibodies following DNA immunization. Mice were immunized into the skin with DNA-coated gold microspheres using a gene-gun, or into the quadriceps muscle by intramuscular injection. Both methods of delivery generated antigen-specific IgG antibodies against the 22 kDa schistosome antigen. The use of a secretory leader sequence, such as the murine Ig-kappa chain used in this study, may facilitate the induction of host antibody responses following DNA immunization with other parasite cDNAs.     

细胞因子表达质粒对恶性疟原虫顶端膜抗原1DNA免疫的调节作用

目的　探讨细胞因子表达质粒对小鼠DNA免疫的促进和调节作用。　方法　构建编码恶性疟原虫顶端膜抗原1(AMA1)完整胞外域的DNA免疫质粒VR1020/E,构建编码小鼠细胞因子(GMCSF)、白细胞介素(IL)如IL4和IL12的真核表达质粒pcDNA3/GMCSF、pcDNA3.1( ) /IL4和pIL12以及双顺反子质粒pGM CSF/pTPA E,分组免疫小鼠,ELISA检测血清中特异性IgG及其亚类的水平,取小鼠脾细胞进行体外增殖。　结果　 3种细胞因子质粒均有效增强了小鼠针对VR10 20/E的免疫应答,抗体水平增加7至10倍,其中pcDNA3/GMCSF质粒和pIL12质粒分别显著促进了小鼠的IgG1和IgG2a应答,小鼠脾细胞的体外增殖水平亦有明显提高。　结论　利用编码GM CSF、IL4和IL12的表达质粒作为佐剂可有效增强小鼠针对AMA1DNA的免疫应答,并对免疫应答的类型产生调节作用。     

Preferential induction of a Th1 immune response and inhibition of specific IgE antibody formation by plasmid DNA immunization.

We compared the antigen-specific antibody isotypes and lymphokine secretion by CD4+ T cells in BALB/c mice immunized intradermally with either Escherichia coli beta-galactosidase (beta-gal) or plasmid DNA (pDNA) encoding beta-gal in a cytomegalovirus-based expression vector (pCMV-LacZ). pCMV-LacZ induced mainly IgG2a, whereas beta-gal in saline or alum induced IgG1 and IgE beta-gal-specific antibodies. In addition, splenic CD4+ T helper (Th) cells isolated from pDNA-immunized mice secreted interferon-gamma but not interleukin (IL)-4 and IL-5, whereas Th cells from beta-gal-injected mice secreted IL-4 and IL-5 but not interferon-gamma after in vitro stimulation with antigen. Together these data demonstrate that pDNA immunization induced a T helper type 1 (Th1) response, whereas protein immunization induced a T helper type 2 (Th2) response to the same antigen. Interestingly, priming of mice with pCMV-LacZ prevented IgE antibody formation to a subsequent i.p. beta-gal in alum injection. This effect was antigen-specific, because priming with pCMV-LacZ did not inhibit IgE anti-ovalbumin antibody formation. Most importantly, intradermal immunization with pCMV-LacZ (but not pCMV-OVA) of beta-gal in alum-primed mice caused a 66-75% reduction of the IgE anti-beta-gal titer in 6 weeks. Also, pCMV-LacZ induced specific IgG2a antibody titers and interferon-gamma secretion by Th cells in the beta-gal in alum-primed mice. The data demonstrate that gene immunization induces a Th1 response that dominates over an ongoing protein-induced Th2 response in an antigen-specific manner. This suggests that immunization with pDNA encoding for allergens may provide a novel type of immunotherapy for allergic diseases.