Host Defenses in Murine Malaria: Immunological Characteristics of a Protracted State of Immunity to Plasmodium yoelii

Random-bred ICR mice recovered from infection with avirulent Plasmodium yoelii were challenged at various later times with virulent P. yoelii or with another species of Plasmodium, P. berghei, to characterize the immunological nature of the long-term state of immunity generated in response to the avirulent infection. It was found that recovered mice resisted lethal challenge with virulent P. yoelii through at least 416 days after primary infection. However, the quality of this immunity changed as the time after avirulent infection increased. Mice challenged early after recovery were able to prevent the development of patent parasitemia. Later, these immune animals lost this capacity and after challenge infections progressed to patency at the same rate as did nonimmune controls. However, after the establishment of parasitemia, those animals which had encountered the homologous parasite a long time before controlled, and then eliminated, blood infection and survived. The “early” state of immunity was expressed by animals which may have harbored small numbers of viable avirulent parasites and possessed a protective humoral factor which could passively transfer anti-P. yoelii activity to naive recipients. In contrast, animals with “late” immunity showed evidence of neither persisting avirulent parasites nor serum anti-P. yoelii activity. The results support the proposition that immunity to this parasite exists as two distinct but interrelated states of immunological reactivity: an early “active” immunity and a later state which has characteristics suggestive of a state of immunological memory wherewith the animals were capable of anamnestically responding to P. yoelii challenge. Little evidence of heterologous immunity to P. berghei was observed for animals recovered from P. yoelii.     

Immunization of Mice with Live-Attenuated Late Liver Stage-Arresting Plasmodium yoelii Parasites Generates Protective Antibody Responses to Preerythrocytic Stages of Malaria

Understanding protective immunity to malaria is essential for the design of an effective vaccine to prevent the large number of infections and deaths caused by this parasitic disease. To date, whole-parasite immunization with attenuated parasites is the most effective method to confer sterile protection against malaria infection in clinical trials. Mouse model studies have highlighted the essential role that CD8⁺ T cells play in protection against preerythrocytic stages of malaria; however, there is mounting evidence that antibodies are also important in these stages. Here, we show that experimental immunization of mice with Plasmodium yoelii fabb/f⁻ (Pyfabb/f⁻), a genetically attenuated rodent malaria parasite that arrests late in the liver stage, induced functional antibodies that inhibited hepatocyte invasion in vitro and reduced liver-stage burden in vivo. These antibodies were sufficient to induce sterile protection from challenge by P. yoelii sporozoites in the absence of T cells in 50% of mice when sporozoites were administered by mosquito bite but not when they were administered by intravenous injection. Moreover, among mice challenged by mosquito bite, a higher proportion of BALB/c mice than C57BL/6 mice developed sterile protection (62.5% and 37.5%, respectively). Analysis of the antibody isotypes induced by immunization with Pyfabb/f⁻ showed that, overall, BALB/c mice developed an IgG1-biased response, whereas C57BL/6 mice developed an IgG2b/c-biased response. Our data demonstrate for the first time that antibodies induced by experimental immunization of mice with a genetically attenuated rodent parasite play a protective role during the preerythrocytic stages of malaria. Furthermore, they highlight the importance of considering both the route of challenge and the genetic background of the mouse strains used when interpreting vaccine efficacy studies in animal models of malaria infection.     

Elevated Levels of the Plasmodium yoelii Homologue of Macrophage Migration Inhibitory Factor Attenuate Blood-Stage Malaria

The excessive production of proinflammatory cytokines plays a significant role in the pathogenesis of severe malaria. Mammalian macrophage migration inhibitory factor (MIF) (mMIF) is an immune mediator that promotes a sustained proinflammatory response by inhibiting the glucocorticoid-mediated downregulation of inflammation. In addition, Plasmodium parasites also encode a homologue of mammalian MIF that is expressed in asexual-stage parasites. We used the Plasmodium yoelii murine model to study the potential role of parasite-encoded MIF in the pathogenesis of malaria. Antibodies raised against purified, non-epitope-tagged P. yoelii MIF (PyMIF) were used to localize expression in trophozoite- and schizont-stage parasites and demonstrate extracellular release. In vitro, recombinant PyMIF was shown to actively induce the chemotaxis of macrophages but did not induce or enhance tumor necrosis factor alpha (TNF-α) production from peritoneal macrophages. To examine the role of parasite-derived PyMIF in vivo, two transgenic parasite lines that constitutively overexpress PyMIF were generated, one in a nonlethal P. yoelii 17X background [Py17X-MIF(+)] and the other in a lethal P. yoelii 17XL background [Py17XL-MIF(+)]. Challenge studies with transgenic parasites in mice showed that the increased expression of PyMIF resulted in a reduction in disease severity. Mice infected with Py17X-MIF(+) developed lower peak parasitemia levels than controls, while malaria-associated anemia was unaltered. Infection with Py17XL-MIF(+) resulted in a prolonged course of infection and a reduction in the overall mortality rate. Combined, the data indicate that parasite-derived MIF does not contribute significantly to immunopathology but, through its chemotactic ability toward macrophages, may attenuate disease and prolong infection of highly virulent parasite isolates.Malaria, caused by protozoan Plasmodium spp., is a significant global health problem, with about 3.3 billion people at risk of infection worldwide (30, 33). The disease can range from a mild, uncomplicated febrile illness to severe, life-threatening syndromes, including cerebral malaria and severe malarial anemia (41). Studies with human subjects show that severe malaria often resembles a sepsis-like syndrome, in that the excessive production of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin-1 (IL-1), IL-6, and gamma interferon (IFN-γ) can contribute to pathology (19, 20, 34). A fine balance in the regulation of the inflammatory response by modulatory anti-inflammatory cytokines such as IL-10 and transforming growth factor β (TGF-β) is required to control parasite replication while limiting immunopathology (25, 46). Data from studies of the rodent malaria parasites Plasmodium yoelii, Plasmodium chabaudi, and Plasmodium berghei also showed that the timing and magnitude of TNF-α, IFN-γ, TGF-β, and IL-10 production markedly influence disease severity and infection outcome (40, 44, 45). One key immunomodulator that likely influences the overall balance between proinflammatory and anti-inflammatory responses during malaria is macrophage migration inhibitory factor (MIF) (21).Mammalian MIF (mMIF), one of the earliest cytokines to be discovered, is homotrimeric in structure and functions as an upregulator of the proinflammatory cascade (14). mMIF is expressed in several immune cell types, including activated T cells, monocytes/macrophages, and eosinophils as well as in cells and tissues of the neuroendocrine system, lung, skin, and gastrointestinal tract (9, 14). mMIF exerts its action mainly by inhibiting glucocorticoid-mediated anti-inflammatory responses (13). A mMIF receptor complex that includes CD74, the major histocompatibility complex (MHC) class II invariant chain, along with CD44, a second surface glycoprotein, has been identified (39, 54). mMIF binds directly to CD74, while CD44 serves as the intracellular signaling component. The binding of mMIF to its receptor complex enables the activation of extracellular signal-regulated kinase (ERK) signaling cascades and the upregulation of the proinflammatory response. Mammalian MIF has been shown to be important in the pathology of several inflammatory conditions, including endotoxic shock, rheumatoid arthritis, atherosclerosis, and cancer (7, 8, 14). Studies of malaria in human subjects and in animal models have also shown a role for host MIF. Previously reported studies of P. chabaudi indicated a pathogenic role for mMIF specifically in the development of severe malarial anemia (42, 43). mMIF knockout (KO) mice infected with P. chabaudi showed increased survival and reduced anemia during infection. Studies of human subjects in areas where malaria is endemic point to a similar pathogenic role for mMIF. Increased mMIF production was associated with heightened inflammatory responses in cases of cerebral malaria and placental malaria (16-18, 35). Recent data suggest that polymorphisms in the mammalian mif promoter associated with elevated levels of mMIF production may increase the risk for developing severe malaria (5, 61). It is important to point out, however, that several studies of uncomplicated and severe P. falciparum malaria assign a protective role for mMIF. In some cases, high circulating levels of mMIF were associated with reduced anemia and with milder episodes of malaria in children (3, 4, 6). An explanation for the apparent discrepancies is not obvious. One factor not specifically considered in those previous studies is that all genomes of Plasmodium parasites examined to date also contain mif homologues (2, 29).Studies of P. berghei-, P. falciparum-, and P. yoelii-encoded MIF revealed a 116-amino-acid protein with ∼30% amino acid sequence identity with mMIF (2, 22, 24, 52). Collectively, the data suggest that plasmodial MIF (pMIF) is structurally similar to mMIF and possesses some but probably not all activities normally attributed to mMIF. As such, the hypothesis that parasite-encoded MIF could enhance proinflammatory responses and contribute to the severity of malaria is reasonable. Infection of mice with P. berghei mif (pbmif) knockout parasites led to earlier and increased reticulocytosis. However, the development of cerebral complications in C57BL/6 mice and hyperparasitemia and severe anemia in BALB/c mice did not differ upon infection with P. berghei wild-type or pbmif knockout parasites (2). While in vitro studies suggested that it is likely that pMIF modulates host immune responses, additional in vivo studies are needed to evaluate its effect on infection outcome (2, 22). Here, we describe the functional properties of recombinant, non-epitope-tagged, P. yoelii MIF (PyMIF) and provide evidence that disease severity is reduced upon infection with nonlethal and lethal P. yoelii transgenic parasites engineered for the increased expression of PyMIF.     

CD4+ T-Cell- and Gamma Interferon-Dependent Protection against Murine Malaria by Immunization with Linear Synthetic Peptides from a Plasmodium yoelii 17-Kilodalton Hepatocyte Erythrocyte Protein

Most work on protective immunity against the pre-erythrocytic stages of malaria has focused on induction of antibodies that prevent sporozoite invasion of hepatocytes, and CD8(+) T-cell responses that eliminate infected hepatocytes. We recently reported that immunization of A/J mice with an 18-amino-acid synthetic linear peptide from Plasmodium yoelii sporozoite surface protein 2 (SSP2) in TiterMax adjuvant induces sterile protection that is dependent on CD4(+) T cells and gamma interferon (IFN-gamma). We now report that immunization of inbred A/J mice and outbred CD1 mice with each of two linear synthetic peptides from the 17-kDa P. yoelii hepatocyte erythrocyte protein (HEP17) in the same adjuvant also induces protection against sporozoite challenge that is dependent on CD4(+) T cells and IFN-gamma. The SSP2 peptide and the two HEP17 peptides are recognized by B cells as well as T cells, and the protection induced by these peptides appears to be directed against the infected hepatocytes. In contrast to the peptide-induced protection, immunization of eight different strains of mice with radiation-attenuated sporozoites induces protection that is absolutely dependent on CD8(+) T cells. Data represented here demonstrate that CD4(+) T-cell-dependent protection can be induced by immunization with linear synthetic peptides. These studies therefore provide the foundation for an approach to pre-erythrocytic-stage malaria vaccine development, based on the induction of protective CD4(+) T-cell responses, which will complement efforts to induce protective antibody and CD8(+) T-cell responses.     

Depletion of Phagocytic Cells during Nonlethal Plasmodium yoelii Infection Causes Severe Malaria Characterized by Acute Renal Failure in Mice

In the current study, we examined the effects of depletion of phagocytes on the progression of Plasmodium yoelii 17XNL infection in mice. Strikingly, the depletion of phagocytic cells, including macrophages, with clodronate in the acute phase of infection significantly reduced peripheral parasitemia but increased mortality. Moribund mice displayed severe pathological damage, including coagulative necrosis in liver and thrombi in the glomeruli, fibrin deposition, and tubular necrosis in kidney. The severity of infection was coincident with the increased sequestration of parasitized erythrocytes, the systematic upregulation of inflammation and coagulation, and the disruption of endothelial integrity in the liver and kidney. Aspirin was administered to the mice to minimize the risk of excessive activation of the coagulation response and fibrin deposition in the renal tissue. Interestingly, treatment with aspirin reduced the parasite burden and pathological lesions in the renal tissue and improved survival of phagocyte-depleted mice. Our data imply that the depletion of phagocytic cells, including macrophages, in the acute phase of infection increases the severity of malarial infection, typified by multiorgan failure and high mortality.     

Protection of Mice against Plasmodium yoelii Sporozoite Challenge with P. yoelii Merozoite Surface Protein 1 DNA Vaccines

Immunization of mice with DNA vaccines encoding the full-length form and C and N termini of Plasmodium yoelii merozoite surface protein 1 provided partial protection against sporozoite challenge and resulted in boosting of antibody titers after challenge. In C57BL/6 mice, two DNA vaccines provided protection comparable to that of recombinant protein consisting of the C terminus in Freund’s adjuvant.     

黄芪对豚鼠哮喘模型血红素氧合酶—1表达的影响

用免疫组织化学染色方法观察血红素氧合酶-1（HO-1）在哮喘豚鼠肺组织中的表达变化,测定全血一氧化碳血红蛋白（COHb)的百分比含量并观察气道壁嗜酸性粒细胞（EOS）浸润情况,以探讨黄芪对哮喘豚鼠HO-1表达的影响。发现HO-1主要表达在气道上皮细胞,哮喘各组HO-1的表达水平均显著高于正常组（P＜0.01)。黄芪治疗后HO-1的表达水平显著低于哮喘各组（P＜0.01)。可见黄芪能显著抑制哮喘豚鼠气道上皮细胞HO-1的表达,提示黄芪抑制细胞HO-1的表达可能是黄芪治疗哮喘的作用机制之一。     

Killing of Plasmodium yoelii by enzyme-induced products of the oxidative burst

The murine malaria parasite Plasmodium yoelii was killed in vitro when incubated with glucose and glucose oxidase, a system generating hydrogen peroxide, or with xanthine and xanthine oxidase, a system which produces the superoxide anion and subsequently other products of the oxidative burst. Catalase blocked the killing in both cases; superoxide dismutase and scavengers of hydroxyl radicals or singlet oxygen were ineffective in the xanthine oxidase system. Thus, hydrogen peroxide appears to be the main reactive oxygen species killing P. yoelii.     

Association of a Determinant on Mouse Chromosome 18 with Experimental Severe Plasmodium berghei Malaria

Experimental severe malaria (ESM; also known as experimental cerebral malaria) is an acute lethal syndrome caused by infection with Plasmodium berghei ANKA and associated with coma and other neurological manifestations in mice. Various inbred strains of mice exhibit differences in susceptibility to the development of ESM. For example, C57BL/6 mice are highly susceptible and DBA/2 mice are relatively resistant. We report here the results of a genomewide scan for host genomic regions that control resistance to ESM in DBA/2 mice using an F(2) intercross population of susceptible and resistant strains. A region of mid-chromosome 18 was found to be a major determinant of resistance to ESM.     

细胞穿透肽PEP-1介导血红素加氧酶1预处理对大鼠肝脏缺血再灌注损伤的保护作用

目的:探讨细胞穿透肽PEP-1介导的血红素加氧酶-1(HO-1)对大鼠肝脏缺血再灌注损伤(HIRI)的保护作用。方法:(1)用基因工程学方法人工合成融合蛋白PEP-1-HO-1。(2)选择雄性SD大鼠,随机分为三组(n均=8):假手术组(S组)只开腹,不予干预。HIRI模型组(HIRI组),采用夹闭肝动脉和门静脉30min后恢复血流;HIRI+PEP-1-HO-1预处理组(HIRI+HO-1组),夹闭肝动脉和门静脉前经门静脉注射PEP-1-HO-1蛋白1mg,其余处理同HIRI组。(3)实验完成后,取三组大鼠下腔静脉血,采用自动生化分析仪测定血清谷丙转氨酶(ALT)、谷草转氨酶(AST)、γ-谷氨酰转肽酶(γ-GT)、总胆红素(TBIL)等肝功能指标。处死大鼠,取部分肝脏进行组织切片、HE染色,观察各组肝组织病理学变化。结果:成功制备高纯度PEP-1-HO-1融合蛋白。HIRI组大鼠各项肝功能指标均显著高于S组(P0.01),HIRI+HO-1组各项肝功能指标值明显低于HIRI组(P0.01),但仍高于S组(P0.05)。HIRI组肝细胞肿大或呈球形,胞浆疏松水样变或完全透明,伴炎细胞浸润,可见片状坏死。HIRI+HO-1组肝脏损伤程度较HIRI组明显改善,炎性细胞浸润及肝细胞坏死程度明显减轻,但与S组比较,肝脏组织损伤仍明显。结论:用细胞穿透肽PEP-1介导HO-1预处理能有效保护肝细胞,明显减轻肝功能损害。     

Elucidation of the receptors in macrophage and Plasmodium yoelii interactions

Binding of hyperimmune serum opsonized merozoites of Plasmodium Yoelii nigerensis to trypsinized macrophages suggested it to be mediated by FcII receptor. Receptor blocking inhibition with monoclonal antibody 2.4G2 directed against Fc receptor for IgG1/IgG2b provided evidence that Fc delta 2b on macrophage played an important role in the merozoite-macrophage interactions. In addition, a neuraminidase sensitive receptor was noted to mediate the binding of P. yeelii merozoites in the absence of serum. Binding inhibition studies with two monosaccharides, D-mannose and alpha-methyl mannoside, indicated the role of Mannose/Fucose receptor on macrophage in this interaction.     

Trials to infect Anopheles stephensi with Plasmodium yoelii nigeriensis by the membrane feeding technique.

The aim of this study was to find optimal conditions for the membrane feeding technique to obtain maximum infection rates of mosquitoes with Plasmodium yoelii nigeriensis. The results show that the malaria parasite Plasmodium yoelii nigeriensis is most infective to Anopheles stephensi mosquitoes on day 3 of the infection in the mice, 1 day before the peak of parasitaemia. The mortality rate of the mosquitoes fed on mice on day 3 after infection was the highest as compared to mosquitoes fed on other days after infection. Gametocytes from mice 3 days after infection were fed to mosquitoes by three different membrane feeding methods. The results indicate that feeding during the first 10 min after blood collection gave the highest infection rates. Keeping the blood meal at a pH of 7.2 yields higher infection rates than keeping it at pH of 8.5. Stirring of the blood and supplying it with CO2 is not necessary when feeding of the mosquitoes is completed within the first 10 min after collection of the blood.     

Effect of Plasmodium yoelii Exposure on Vaccination with the 19-Kilodalton Carboxyl Terminus of Merozoite Surface Protein 1 and Vice Versa and Implications for the Application of a Human Malaria Vaccine

It is well known that exposure to one antigen can modulate the immune responses that develop following exposure to closely related antigens. It is also known that the composition of the repertoire can be skewed to favor epitopes shared between a current infection and a preceding one, a phenomenon referred to as “original antigenic sin.” It was of interest, therefore, to investigate the antibody response that develops following exposure to the malaria vaccine candidate homologue Plasmodium yoelii MSP1₁₉ in mice that had previously experienced malaria infection and vice versa. In this study, preexposure of mice to Plasmodium yoelii elicited native anti-MSP1₁₉ antibody responses, which could be boosted by vaccination with recombinant MSP1₁₉. Likewise, infection of MSP1₁₉-primed mice with P. yoelii led to an increase of anti-MSP1₁₉ antibodies. However, this increase was at the expense of antibodies to parasite determinants other than MSP1₁₉. This change in the balance of antibody specificities significantly affected the ability of mice to withstand a subsequent infection. These data have particular relevance to the possible outcome of malaria vaccination for those situations where the vaccine response is suboptimal and suggest that suboptimal vaccination may in fact render the ultimate acquisition of natural immunity more difficult.     

血红素加氧酶-1过表达延长肝脏低温保存时间的研究

目的 研究血红素加氧酶-1(heme oxygenase-1,HO-1)过表达延长肝脏低温保存的时间及其机制.方法 利用大鼠肝脏离体再灌注模型,用钴-原卟啉(cobalt protoporphyrin,CoPP)和锌-原卟啉(zincprotoporphyrin,ZnPP)特异地诱导和抑制HO-1,观察肝脏保存0、6、24h,灌注2h后的胆汁生成量,灌流液AST、LDH、TNF-α和IL-6的活性,肝脏MDA的含量,肝组织HO-1蛋白表达的Western印迹,细胞凋亡情况等.结果 CoPP诱导了肝组织HO-1的表达,与未诱导24h保存组相比,CoPP诱导组的肝脏灌流液AST、LDH、TNF-α和IL-6的活性以及肝脏MDA含量显著降低,胆汁生成量明显增加,凋亡细胞数量减少(P<0.05),并与未诱导6h保存组接近.给予ZnPP后,这些保护作用消失.结论 HO-1过表达延长了肝脏低温保存时间,原因可能与抗氧化应激、抑制炎性因子的表达和细胞凋亡有关.     

Characterization of liver lymphomyeloid cells in mice infected with Plasmodium yoelii sporozoites.

We have isolated, characterized and quantified the immunocompetent cells present in the extravascular hepatic compartment at various stages after Plasmodium yoelii malaria infection with sporozoites. Cytological analyses revealed a predominantly lymphoid population. In mice with a primary infection, the predominant cells were CD4+, CD8+ and B lymphocytes. In fully protected mice, CD3+ CD4- CD8- and polymorphonuclear cells, particularly eosinophils, were most common. The significance of changes in subpopulations is discussed in relation to antigen presentation and host-protective mechanisms.     

The high molecular mass rhoptry protein, RhopH1, is encoded by members of the clag multigene family in Plasmodium falciparum and Plasmodium yoelii.

Malarial merozoite rhoptries contain a high molecular mass protein complex called RhopH. RhopH is composed of three polypeptides, RhopH1, RhopH2, and RhopH3, encoded by distinct genes. Using monoclonal antibody-purified protein complex from both Plasmodium falciparum and Plasmodium yoelii, peptides were obtained by digestion of RhopH1 and their sequence determined either by mass spectrometry or Edman degradation. In both species the genes encoding RhopH1 were identified as members of the cytoadherence linked asexual gene (clag) family. In P. falciparum the family members on chromosome 3 were identified as encoding RhopH1. In P. yoelii two related genes were identified and sequenced. One of the genes, pyrhoph1a, was positively identified as encoding RhopH1 by the peptide analysis and the other gene, pyrhoph1a-p, was at least transcribed. Genes in the clag family present in both parasite species have a number of conserved features. The size and location of the P. yoelii protein complex in the rhoptries was confirmed. The first clag gene identified on chromosome 9 was implicated in cytoadherence, the binding of infected erythrocytes to host endothelial cells; this study shows that other members of the family encode merozoite rhoptry proteins, proteins that may be involved in merozoite-erythrocyte interactions. We propose that the family should be renamed as rhoph1/clag.     

Comparison of protection induced by immunization with recombinant proteins from different regions of merozoite surface protein 1 of Plasmodium yoelii.

Vaccination with native full-length merozoite surface protein 1 (MSP1) or with recombinant C-terminal peptides protects mice against lethal challenge with virulent malaria parasites. To determine whether other regions of MSP1 can also induce protection, Plasmodium yoelii MSP1 was divided into four separate regions. Each was expressed in Escherichia coli as a fusion protein with glutathione S-transferase (GST). The N-terminal fragment began after the cleavage site for the signal sequence and ended in the region comparable to the cleavage site for the C terminus of the 82-kDa peptide of Plasmodium falciparum. This expressed protein was 30 kDa smaller than the predicted peptide. One peptide from the middle region was produced, and the C terminus consisted of a 42-kDa fragment corresponding to the analogous peptide of P. falciparum and a 19-kDa fragment that extended 37 amino acids in the amino-terminal direction beyond the probable cleavage site. To test protection of mice against lethal P. yoelii challenge, three mouse strains (CAF1, BALB/c, and A/J) were vaccinated with each of the four recombinant proteins of MSP1. Mice vaccinated with the C-terminal 19-kDa protein were highly protected (described previously), as were those vaccinated with the 42-kDa protein that contained the 19-kDa fragment. The N-terminally expressed fragment of P. yoelii was not full length because of proteolytic cleavage in E. coli. The GST-82-kDa partial fragments induced some immunity, but the surviving mice still had high parasitemias. Vaccination with the peptide from the middle region of MSP1 gave minimal to no protection. Therefore, in addition to the C-terminal 19- and 42-kDa proteins, the only other fragment to give protection was the 82-kDa protein. The protection induced by the truncated 82-kDa protein was minimal compared with that of the C-terminal fragments.     

肝损伤时诱导肝星状细胞中小窝蛋白-1表达升高

目的 探究肝损伤介导肝星形细胞小窝蛋白-1的表达的影响.方法 通过肝总管结扎手术诱导大鼠肝损伤模型和体外培养肝星形细胞LX-2,检测肝组织和肝星形细胞小窝蛋白-1的表达水平.结果 ①与假手术组相比,胆总管结扎手术可显著诱导肝脏损伤,手术后7d,手术组大鼠体重显著减轻,肝脏重量和肝指数显著增加,以及血清谷丙转氨酶和谷草转氨酶水平显著增加;②与假手术组相比,肝损伤可显著诱导小窝蛋白-1在mRNA和蛋白水平显著增加;③与胆总管结扎组相比,LPS处理可显著增加肝星形细胞小窝蛋白-1的表达水平.结果 肝损伤可显著诱导肝星形细胞小窝蛋白-1的表达.     

Reduced antibody response to the repetitive sequence of the Plasmodium falciparum circumsporozoite protein in mice infected with Plasmodium yoelii blood forms

The immunogenicity of the carrier-free synthetic peptide, (NANP)₄₀, from the repetitive region of the Plasmodium falciparum circumsporozoite (CS) protein was investigated in genetically responder mice (C57BL/6, H-2^b) acutely infected with blood forms of the non-lethal murine malaria parasite, P. yoelii. As compared to non-infected mice, P. yoelii-infected C57BL/6 mice produced significantly lower titers of anti-(NANP)₄₀ IgG antibodies. This decrease in the anti-(NANP)₄₀ antibody response peaked with the peak of parasitemia, and involved all the IgG subclasses. Interestingly, this P. yoelii-mediated effect was evident both on the development of the antibody response to the (NANP)₄₀ peptide, and on an already established anti-(NANP)₄₀ antibody titer, as seen in mice immunized with the peptide 1 month before the infection. Since (NANP)_n-based constructs are strongly envisaged as potential vaccines against falciparum malaria, these results might be important in the evaluation of the efficacy of these vaccine candidates, when they will be used in individuals living in endemic areas.