约氏疟原虫BY265株减毒子孢子诱导小鼠保护性免疫的研究

目的探讨约氏疟原虫BY265株减毒子孢子免疫能否诱导小鼠产生完全保护性免疫及其效应分子。方法确定减毒子孢子合适辐照剂量并免疫小鼠后,间接免疫荧光和ELISPOT分别检测抗环子孢子蛋白(CSP)抗体滴度和CSP特异的CD8+T细胞分泌IFN-γ及其抵御子孢子的攻击感染情况。结果免疫小鼠的外周血能检测到子孢子CSP特异的抗体(1∶400)和产生IFN-γ的CSP特异CD8+T细胞;与对照小鼠相比,1000个子孢子尾静脉注射攻击减毒子孢子免疫小鼠后,直到14d也检测不到红内期疟原虫。结论经辐照减毒子孢子免疫后的小鼠对野生株子孢子产生了完全保护性免疫,为红外期疫苗的研究提供基础与理论依据。     

中国株HIV-1 gp120核酸疫苗的实验免疫研究

目的　探讨表达中国株HIV 1gp12 0基因的核酸疫苗在小鼠体内的免疫反应。方法　将表达HIV 1gp12 0的核酸疫苗质粒pVAXP经肌肉注射免疫Balb c小鼠 ,检测免疫小鼠脾CD4 +、CD8+T细胞亚群的数量 ,脾特异性CTL杀伤活性和血清抗体滴度。结果　重组质粒pVAXP免疫组小鼠脾CD4 +、CD8+T细胞亚群的数值均比对照组高 (P <0 .0 5 ) ;免疫组脾特异性CTL杀伤活性与对照组相比差异极显著 (P <0 .0 1) ;血清抗体滴度显著高于对照组 (P <0 .0 5 )。结论　表达HIV 1gp12 0基因的核酸疫苗质粒pVAXP能诱导小鼠产生特异性细胞和体液免疫。     

BCG/恶性疟MSP-2、CSP多价疫苗免疫小鼠应答类型研究

目的：探讨恶性疟原虫FCC－1／HN株裂殖子表面蛋白－2（MSP－2）和环子孢子蛋白（CSP）与BCG多价疫苗在小鼠体内诱导的免疫应答的特性及抗感染的保护性免疫机制。方法：将重组pBCG／MSP－2和pBCG／CSP多价疫苗经皮下注射BALB／c小鼠，小鼠经多价疫苗免疫8周后，用流式细胞仪分析脾脏T淋巴细胞的分化，并体外培养脾脏细胞，用夹心ELISA法测定IFN－γ和IL－2的产生；用血清学方法测定免疫鼠IgG抗体的动态变化，在体外测定抗体介导的抑制实验。结果：与对照组相比，疫苗组CD4^ 和CD8^ T淋巴细胞有显著性的增高，体外培养的脾脏细胞IFN－γ有高浓度的分泌。同时，免疫鼠血清对疟原虫抗原都表现了较高水平的IgG类抗体反应，抗体对原虫的增殖明显抑制。结论：恶性疟原虫FCC－1／HNpBCG/MSP-2和pBCG/CSP多价疫苗诱导了以TH1为主的免疫应答类型。     

HIV-2 DNA疫苗免疫小鼠的免疫反应观察

目的：用构建的HIV－2外膜蛋白gp105和核心蛋白gag基因的DNA疫苗免疫小鼠，评价其免疫效果。方法：将HIV－2型gp 105和gag基因克隆到表达载体pIRES1neo中，构建重组DNA疫苗质粒。间接免疫荧光试验证明，构建的DNA疫苗在真核细胞中表达了gp105或／和gag.构建的疫苗免疫小鼠后，用流式细胞仪测定CD4^ 、CD8^ T淋巴细胞亚类数，并用HIV－2抗体ELISA检测试剂盒检测免疫鼠血清中抗HIV－2抗体水平。结果：构建了3种HIV－2 DNA疫苗pIRES1gag、pIRSE1gp105和pIRES1gag-gp105，转染BHK细胞后均能表达抗原蛋白，免疫小鼠后可有效地刺激淋巴细胞增殖并诱导产生抗HIV－2特异性抗体，其中pIRES1gag-gp105免疫鼠中，淋巴细胞增殖最显著，而pIRES1gp105免疫鼠中HIV－2特异性抗体水平最高。结论：构建的DNA疫苗均能诱导机体产生免疫反应，其中pIRES1gp105诱导的体液免疫应答最显著，而pIRES1gag-gp105 诱导的细胞免疫响应最显著。     

小鼠对HIV-2 gp105核酸疫苗免疫应答的研究

目的: 探讨HIV- 2gp105基因核酸疫苗在小鼠体内的免疫应答, 为开发HIV- 2核酸疫苗提供实验依据。方法:将HIV- 2外膜蛋白 (gp105 )基因插入真核表达质粒载体pVAX1中, 构建pVAX1 gp105重组表达质粒。将其肌注免疫BALB/c小鼠, 用ELISA法检测小鼠血清抗HIV -2抗体, 用流式细胞仪测定CD4 、CD8 T细胞亚群数, 以乳酸脱氢霉释放法检测脾特异性CTL的杀伤活性。结果: 重组质粒pVAX1 -gp105免疫组小鼠的血清抗体滴度、脾T细胞亚群的数量及特异性CTL的杀伤活性, 均明显高于对照组, 分别为P<0. 01, P<0. 05和P<0. 01。结论: HIV -2gp105核酸疫苗能诱导小鼠产生特异性细胞和体液免疫。     

表达HIV-1 gag-gp120嵌合基因的DNA疫苗在小鼠体内的免疫应答

目的 :检测表达HIV 1gag gp12 0嵌合基因的DNA疫苗在小鼠体内的免疫应答效果。方法 :将真核表达质粒pVAXGE肌肉注射BALB C小鼠 ,观察免疫小鼠脾T淋巴细胞亚群的数量、特异性CTL杀伤率及小鼠免疫后不同时间点血清中IgG抗体滴度。结果 :重组质粒pVAXGE免疫组小鼠脾淋巴细胞进行了增殖 ,脾特异性CTL杀伤率显著高于对照组 (P <0 0 1) ;小鼠免疫后于第 8周血清抗体达到最高。结论 :表达HIV 1gag gp12 0嵌合基因的DNA疫苗质粒可诱导BALB C小鼠发生免疫应答     

微小隐孢子虫子孢子表面蛋白质粒DNA接种诱导Balb/c小鼠的免疫应答

目的　探讨微小隐孢子虫子孢子表面蛋白CP2 3重组质粒pCR3.1～ 2 3DNA疫苗诱导机体产生体液和细胞免疫应答的效果。方法　用重组的DNA疫苗于Balb/c小鼠后腿胫骨前肌注射免疫 ,于 0、3、6周共免疫 3次 ,10 0 μg/次。免疫后不同时间检测体液和细胞免疫应答指标。并用 1× 10 6卵囊进行攻虫试验。结果　pCR3.1～ 2 3可诱导机体产生相应的特异性抗体 ,对C .parvum卵囊攻击具有保护作用。结论　微小隐孢子虫子孢子表面蛋白CP2 3重组质粒pCR3.1～ 2 3有可能作为侯选的隐孢子虫DNA疫苗 ,值得进一步深入研究。     

弓形虫多表位DNA疫苗的构建及其免疫保护作用

目的:构建弓形虫多表位DNA疫苗并研究其免疫保护效果.方法:将编码含弓形虫多个T、B细胞表位的6段弓形虫多肽基因,以5个甘氨酸编码基因相间隔相连接,克隆入真核表达质粒pcDNA3.1( )中,构建成多表位弓形虫DNA疫苗.免疫BALB/c小鼠,测定其诱导的特异性抗体水平及T淋巴细胞增殖状况,同时进行弓形虫攻击感染保护实验.结果:成功构建了包含多个弓形虫表位的真核表达质粒pcDNA3.1/T-ME,以其作为DNA疫苗免疫小鼠,可诱导机体产生弓形虫特异性的体液及细胞免疫应答,产生有效的抗弓形虫保护性免疫应答.结论:构建的弓形虫多表位DNA疫苗能诱导机体产生有效的保护性免疫应答,在控制弓形虫感染上具有可行性.     

人免疫缺陷病毒Ⅱ型核心蛋白DNA疫苗的实验免疫研究

目的　检测HIV 2核心蛋白DNA疫苗诱导Balb c小鼠免疫应答的能力。方法　将表达HIV 2核心蛋白DNA疫苗质粒pVAXIgag肌注Balb c小鼠 ,分析CD4 、CD8 T淋巴细胞的数量、脾特异性CTL反应、血清中HIV 2的特异性抗体水平。结果　重组质粒pVAXI gag免疫组与空载体pVAXI及PBS对照组相比较差异显著 ,血清抗体滴度及淋巴细胞杀伤效应为P <0 .0 1,脾T细胞亚群的数量为P <0 .0 5。结论　HIV 2核心蛋白DNA疫苗能诱导Balb c小鼠产生特异性细胞免疫应答和体液免疫应答     

HCV结构区DNA疫苗诱发小鼠特异性细胞免疫反应的研究

目的 :通过HCV结构区DNA疫苗直接免疫小鼠 ,诱发其体内特异性细胞介导的免疫反应的研究 ,为HCVDNA疫苗的研制打下基础。方法 :用重组的pBK CMV质粒体外转染小鼠骨髓瘤细胞SP2 0 ,建立了能体外表达HCV结构区蛋白的SP2 0D细胞系 ,分别用SP2 0和SP2 0D细胞攻击用空质粒或pBK CMV质粒免疫过的Balb c小鼠 ,通过肿瘤形成、肿瘤重量、肿瘤组织淋巴细胞的浸润以及不同免疫组小鼠血清中IL 2和IFN γ含量来观察小鼠体内T淋巴细胞的活性。结果 :用SP2 0和SP2 0D攻击空质粒或pBK CMV质粒免疫过的小鼠 15d后 ,SP2 0D攻击的pBK CMV质粒免疫鼠肿瘤重量〔(0 9± 0 12 )g〕明显低于空白质粒免疫组和SP2 0接种组 (P <0 0 0 1) ,且该免疫组小鼠血清中IL 2和IFN γ的浓度明显高于其它免疫组 ;此外 ,用SP2 0D攻击的pBK CMV免疫鼠 ,肿瘤病理切片中可见明显的T淋巴细胞浸润。结论 :重组的HCV结构区DNA疫苗 (pBK CMV)能诱导小鼠体内特异性T淋巴细胞反应 ,HCVDNA疫苗可能为临床疾病的治疗和预防提供一种新的途径     

Immunization with a recombinant C-terminal fragment of Plasmodium yoelii merozoite surface protein 1 protects mice against homologous but not heterologous P. yoelii sporozoite challenge.

It has been reported previously that immunization with recombinant protein containing the two epidermal growth factor (EGF)-like modules from merozoite surface protein 1 (MSP-1) of Plasmodium yoelii (strain YM) protects mice against a lethal blood-stage challenge with the same parasite strain. Since MSP-1 is expressed in both liver- and blood-stage schizonts and on the surface of merozoites, we evaluated the effectiveness of immunization with recombinant proteins containing either the individual or the two combined EGF-like modules in producing a protective response against a sporozoite challenge. The recombinant protein expressing the combined EGF-like modules of the YM strain protected mice against a homologous sporozoite challenge, and sterile protection, as defined by the absence of detectable blood-stage parasites, was observed in the majority of the mice. In contrast, mice immunized with recombinant P. yoelii YM MSP-1 were not protected against a heterologous challenge with sporozoites from strain 265 BY of P. yoelii. The lack of protection may be explained by differences identified in the amino acid sequences of MSP-1 for the two strains. A recombinant protein containing the two EGF-like modules of MSP-1 from P. yoelii 265 BY was produced and used to immunize mice. These mice were protected against a homologous challenge with sporozoites of P. yoelii 265 BY. The results suggest that a recombinant MSP-1 has potential as a vaccine against malaria, but its efficacy may be limited by sequence polymorphism and selection of variants.     

Class II-restricted protective immunity induced by malaria sporozoites

The irradiated-sporozoite vaccine elicits sterile immunity against Plasmodium parasites in experimental rodent hosts and human volunteers. Based on rodent malaria models, it has been proposed that CD8+ T cells are the key protective effector mechanism required in sporozoite-induced immunity. To investigate the role of class II-restricted immunity in protective immunity, we immunized beta2-microglobulin knockout (beta2M-/-) mice with irradiated Plasmodium yoelii or P. berghei sporozoites. Sterile immunity was obtained in the CD8+-T-cell-deficient mice immunized with either P. berghei or P. yoelii sporozoites. beta2M-/- mice with the BALB/c (H-2d) genetic background as well as those with the C57BL (H-2b) genetic background were protected. Effector mechanisms included CD4+ T cells, mediated in part through the production of gamma interferon, and neutralizing antibodies that targeted the extracellular sporozoites. We conclude that in the absence of class I-restricted CD8+ T cells, sporozoite-induced protective immunity can be effectively mediated by class II-restricted immune effector mechanisms. These results support efforts to develop subunit vaccines that effectively elicit high levels of antibody and CD4+ T cells to target Plasmodium pre-erythrocytic stages.     

The course of a primary infection of Plasmodium yoelii 17XL in both 129S1 and IFN-γ receptor-deficient mice

In the present study, we found that 129S1 mice are resistant to the infection with Plasmodium yoelii 17XL, which is highly virulent and causes lethal infection in various strains of mice. In contrast, IFN-γ receptor-deficient (IFN-γR(-/-)) mice on the 129S1 background were much more susceptible than 129S1 mice with intraperitoneal infection with 1?×?10(5) parasitized erythrocytes. The mortality in 129S1 and IFN-γR(-/-) mice was 11.6 and 79.4 %, respectively. Following inoculation of the parasites, both 129S1 and IFN-γR(-/-) mice showed a progressive increase in parasitemia. Growth rate of malaria parasites at the early stages of infection in the IFN-γR(-/-) mice was faster than that in 129S1 mice, and this difference in growth rate might cause the earlier death of IFN-γR(-/-) host from day 8 of infection than that of 129S1. In surviving mice of both strains, however, malaria parasites in their bloodstream began to decrease in number right after a peak of parasitemia and were not detectable by a microscopic examination during the observation period. Next, we investigated the cytokine and antibody production in 129S1 and IFN-γR(-/-) mice during infection. An analysis of cytokines showed that serum IFN-γ and IL-4 levels elevated significantly from day 1 and day 4 of infection, respectively, in both 129S1 and IFN-γR(-/-) mice when compared with the levels from the uninfected controls. Following the infection, significantly higher levels of malaria-specific IgG1 and IgG2a antibodies in the infected 129S1 mice were detected from day 15, and these elevations were coincident with the decrease of parasitemia. On the other hand, the levels of malaria-specific antibodies in IFN-γR(-/-) mice had a tendency to elevate on day 21 but did not reach statistical significance. The present data indicate that IFN-γR plays an essential role in mediating the early immune mechanisms induced by the infection of erythrocytic stages of P. yoelii 17XL parasite, leading to host survival.     

Complete protection against Plasmodium yoelii by adoptive transfer of a CD8+ cytotoxic T-cell clone recognizing sporozoite surface protein 2.

BALB/c mice immunized with irradiated Plasmodium yoelii sporozoites produce antibodies and cytotoxic T lymphocytes against the circumsporozoite protein and against a 140-kDa protein, sporozoite surface protein 2 (PySSP2). Approximately 50% of mice immunized with P815 cells transfected with the gene encoding PySSP2 are protected against malaria, and this protection is reversed by in vivo depletion of CD8+ T cells. To determine if CD8+ T cells against PySSP2 are adequate to protect against malaria in the absence of other malaria-specific immune responses, we produced three CD8+ T-cell clones by stimulating spleen cells from mice immunized with irradiated P. yoelii sporozoites with a mitomycin-treated P815 cell clone transfected with the PySSP2 gene. Adoptive transfer of clone TSLB7 protected 100% of mice against P. yoelii. The second clone protected 58% of mice, and the third clone provided no protection. Clone TSLB7 protected even when administered 3 h after sporozoite inoculation at a time when sporozoites had entered hepatocytes, suggesting that it is recognizing and eliminating infected hepatocytes. These studies demonstrate that cytotoxic T lymphocytes against PySSP2 can protect against P. yoelii sporozoite challenge in the absence of other parasite-specific immune responses.     

Specific inflammatory cell infiltration of hepatic schizonts in BALB/c mice immunized with attenuated Plasmodium yoelii sporozoites.

We compared immunization of BALB/c mice with radiation-attenuated versus killed sporozoites of the rodent malaria parasite, Plasmodium yoelii. We employed a suboptimal schedule of only two immunizations, in expectation that some parasites might break through the resultant low level immunity and that it might thus be possible to study the response of the host against these 'breakthrough' schizonts. As a measure of protective immunity, we used histological means to determine the percentages of challenge sporozoites prevented from completing development into hepatic schizonts within the liver. Immunization with attenuated sporozoites led to almost complete protection, whereas immunization with similar dosages of killed sporozoites led to approximately a 75% protection. Fluorescent antibody titers against sporozoites were similar in both sets of immunized animals. However, serum from mice immunized with attenuated sporozoites had a protective effect upon passive transfer into immunologically naive mice subsequently challenged with normal sporozoites; serum from mice immunized with killed sporozoites had no such effect. When mice suboptimally immunized with attenuated sporozoites were challenged, we observed breakthrough schizonts being infiltrated with inflammatory cells, primarily mononuclear cells, and neutrophils; partial depletion of CD4+ or CD8+ cells within these mice prior to challenge prevented the infiltration of breakthrough schizonts. Thus, cellular infiltration of schizonts was apparently secondary to earlier action by lymphocytes. This infiltration was also not observed in mice immunized with killed sporozoites. The more effective protective immunity induced by attenuated sporozoites could be due to their ability to release antigen into the cytoplasm of hepatocytes that they invade or their ability to continue differentiating, thereby presenting new antigens that are not seen after immunization with killed sporozoites.     

Phagocyte-derived reactive oxygen species do not influence the progression of murine blood-stage malaria infections

Phagocyte-derived reactive oxygen species have been implicated in the clearance of malaria infections. We investigated the progression of five different strains of murine malaria in gp91(phox-/-) mice, which lack a functional NADPH oxidase and thus the ability to produce phagocyte-derived reactive oxygen species. We found that the absence of functional NADPH oxidase in the gene knockout mice had no effect on the parasitemia or total parasite burden in mice infected with either resolving (Plasmodium yoelii and Plasmodium chabaudi K562) or fatal (Plasmodium berghei ANKA, Plasmodium berghei K173 and Plasmodium vinckei vinckei) strains of malaria. This lack of effect was apparent in both primary and secondary infections with P. yoelii and P. chabaudi. There was also no difference in the presentation of clinical or pathological signs between the gp91(phox-/-) or wild-type strains of mice infected with malaria. Progression of P. berghei ANKA and P. berghei K173 infections was unchanged in glutathione peroxidase-1 gene knockout mice compared to their wild-type counterparts. The rates of parasitemia progression in gp91(phox-/-) mice and wild-type mice were not significantly different when they were treated with l-N(G)-methylarginine, an inhibitor of nitric oxide synthase. These results suggest that phagocyte-derived reactive oxygen species are not crucial for the clearance of malaria parasites, at least in murine models.     

Induction of CD8+ T cell-mediated protective immunity against Trypanosoma cruzi

Trypanosoma cruzi was transformed with the Plasmodium yoelii gene encoding the circum-sporozoite (CS) protein, which contains the well-characterized CD8+ T cell epitope, SYVPSAEQI. In vivo and in vitro assays indicated that cells infected with the transformed T. cruzi could process and present this malaria parasite-derived class I MHC-restricted epitope. Immunization of mice with recombinant influenza and vaccinia viruses expressing the SYVPSAEQI epitope induced a large number of specific CD8+ T cells that strongly suppressed parasitemia and conferred complete protection against the acute T. cruzi lethal infection. CD8+ T cells mediated this immunity as indicated by the unrelenting parasitemia and high mortality observed in immunized mice treated with anti-CD8 antibody. This study demonstrated, for the first time, that vaccination of mice with vectors designed to induce CD8+ T cells is effective against T. cruzi infection.     

A hybrid multistage protein vaccine induces protective immunity against murine malaria

We have previously reported the design and expression of chimeric recombinant proteins as an effective platform to deliver malaria vaccines. The erythrocytic and exoerythrocytic protein chimeras described included autologous T helper epitopes genetically linked to defined B cell epitopes. Proof-of-principle studies using vaccine constructs based on the Plasmodium yoelii circumsporozoite protein (CSP) and P. yoelii merozoite surface protein-1 (MSP-1) showed encouraging results when tested individually in this mouse malaria model. To evaluate the potential synergistic or additive effect of combining these chimeric antigens, we constructed a synthetic gene encoding a hybrid protein that combined both polypeptides in a single immunogen. The multistage vaccine was expressed in soluble form in Escherichia coli at high yield. Here we report that the multistage protein induced robust immune responses to individual components, with no evidence of vaccine interference. Passive immunization using purified IgG from rabbits immunized with the hybrid protein conferred more robust protection against the experimental challenge with P. yoelii sporozoites than passive immunization with purified IgG from rabbits immunized with the individual proteins. High antibody titers and high frequencies of CD4(+)- and CD8(+)-specific cytokine-secreting T cells were elicited by vaccination. T cells were multifunctional and able to simultaneously produce interleukin-2 (IL-2), gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α). The mechanism of vaccine-induced protection involved neutralizing antibodies and effector CD4(+) T cells and resulted in the control of hyperparasitemia and protection against malarial anemia. These data support our strategy of using an array of autologous T helper epitopes to maximize the response to multistage malaria vaccines.     

Intrasplenic immunization with infected hepatocytes: a mouse model for studying protective immunity against malaria pre-erythrocytic stage.

Malaria liver forms are the target of antibody or T-cell-mediated immune mechanisms induced by previous or subsequent developmental stages of the parasite. The potential for vaccine development of antigens expressed exclusively in the liver stages has not been fully explored partly because of the lack of an experimental animal model. Here we show that protective immunity against sporozoite-induced infection with Plasmodium yoelii and P. berghei can be obtained by intrasplenic injection of a small number of liver stages of the parasites. The serum of the protected animals did not contain antibodies against sporozoites, liver or blood stage malaria parasites. Protective immunity was abolished by depletion of either CD4+ or CD8+ T cells from the vaccinated mice before challenge.     

Peptide-primed CD4+ cells and malaria sporozoites.

We have mapped a T cell epitope in the circumsporozoite (CS) protein of the murine malaria parasite, Plasmodium yoelii. A 21-mer synthetic peptide corresponding to the amino acid positions 59-79 (referred to as Py1), induced specific proliferation in BALB/c and C57BL/6 mice, and provided help for the production of antibodies to peptides from the repetitive region, (QGPGAP)n, of the same CS protein, when mice were immunized with the Py1 peptide conjugated to the repetitive peptide. Long-term CD3+CD4+CD8-TCR alpha beta+ T cell lines and clones were derived from both strains of mice. These lines and clones, that proliferated in an MHC-restricted fashion, did not recognize peptides from the homologous region of another murine malaria parasite, P. berghei. About 50% of these clones produced detectable amounts of IFN-gamma and IL-2, whereas the remaining produced IL-4, IL-5, and IL-6. In preliminary experiments, some of these clones specifically inhibited P. yoelii sporozoite development in vitro and conferred protection in vivo in passive transfer experiments. These findings show that heterogenous T cell populations are activated in mice upon immunization with a short peptide from the P. yoelii CS protein and that some of these cells could be active in the effector arm of the immune response against malaria sporozoites.