Hematopoiesis during acute Toxoplasma gondii infection in mice

We studied hematopoiesis in bone marrow and blood of CBA mice following infection with Toxoplasma gondii. Our data showed that acute infection with the virulent RH strain was associated with leucopenia, thrombocytopenia and bone marrow hypoplasia while, in spite of the infection-induced damage of the granulocyte cell lineage, in bone marrow stimulated production of granulocytes was revealed. In peripheral blood, T. gondii infection caused a significant decrease in the total number of white blood cells, reticulocytes and platelets. However, the relative proportion of granulocytes and lymphocytes was changed in favor of granulocytes, as compared to pre-infection levels. The functional activity of granulocytes was also increased. The bone marrow alterations were characterized by a decrease in the total number of nucleated cells due to the reduced numbers in all cell compartments of erythroid and megakaryocytic lineage, as well as in the number of mature granulocytes and lymphocytes. In contrast, femoral granulocytic proliferative compartments, colony forming unite granulocyte-macrophage (CFU-GM) and morphologically recognizable proliferative granulocytes (PG), exhibited stimulated granulopoiesis, while the number of mature monocytes was close to the control value. In summary, we have shown that acute T. gondii infection results in profound alterations of the hematopoietic system that markedly contribute to the clinical onset of the disease and the, ultimately lethal, outcome.     

Infection with Toxoplasma gondii Alters Lymphotoxin Expression Associated with Changes in Splenic Architecture

B cell responses are required for resistance to Toxoplasma gondii; however, the events that lead to production of class-switched antibodies during T. gondii infection have not been defined. Indeed, mice challenged with the parasite exhibited an expansion of T follicular helper cells and germinal center B cells in the spleen. Unexpectedly, this was not associated with germinal center formation and was instead accompanied by profound changes in splenic organization. This phenomenon was transient and was correlated with a decrease in expression of effector proteins that contribute to splenic organization, including lymphotoxins α and β. The importance of lymphotoxin was confirmed, as the use of a lymphotoxin β receptor agonist results in partial restoration of splenic structure. Splenectomized mice were used to test the splenic contribution to the antibody response during T. gondii infection. Analysis of splenectomized mice revealed delayed kinetics in the production of parasite-specific antibody, but the mice did eventually develop normal levels of parasite-specific antibody. Together, these studies provide a better understanding of how infection with T. gondii impacts the customized structures required for the optimal humoral responses to the parasite and the role of lymphotoxin in these events.     

社区居民弓形虫健康教育效果评价

目的评价对社区居民开展弓形虫病健康教育和重点人群监测干预的效果。方法以社区卫生服务机构为服务载体，对社区居民开展有计划的多种形式的健康教育；对社区居民中育龄妇女、孕妇及宠物饲养者建立健康档案，定期监测；参照“KABP”调查标准，设计调查问卷调查，用SPSS10．0软件分析数据。结果健康教育前社区居民对弓形虫病防治知识、态度信念、行为平均得分为46．5、61．8、81．3；健康教育实施半年后平均得分分别为69．6、77．8、96．6，差异有统计学意义（P〈0．001）。健康教育实施前社区居民特殊人群中育龄妇女、孕妇、宠物饲养者对弓形虫病防治知识知晓率、态度与信念、行为形成率有明显差异（P〈0．01）。结论在社区居民中开展弓形虫病防治的健康教育是有效的。     

弓形虫感染与优生优育

弓形虫是一种分布较广且危害较大的常见寄生虫,特别是当孕妇感染弓形虫后,约有40％的孕妇会通过胎盘将弓形虫垂直传播给胎儿,造成胎儿产生各种先天性弓形虫病,给胎儿的健康带来极大的威胁。因此,控制好弓形虫感染与优生优育有着重要的关系。     

孕期弓形虫感染对胎盘的入侵和病理损害的研究

目的探讨孕期弓形虫感染对胎盘的入侵和病理损害情况。方法孕8dBALB/c小鼠经腹腔接种弓形虫速殖子,在孕10、12、14、16和18d剖腹取胎鼠,分离胎盘并精确称重。采用HE染色观察胎盘的病理损害情况,RNA原位杂交检测胎盘组织弓形虫速殖子的动态入侵。结果在孕10、12d,感染组胎盘重量与对照组比较无明显差别。而在孕14、16、18d,感染组的胎盘重量明显低于对照组（P〈0.01）。随着感染时间的延长,胎盘组织切片可见有大量淋巴细胞、单核细胞、嗜酸性粒细胞浸润,绒毛血管减少,显示有炎症表现;滋养层细胞破坏明显,可见凋亡小体形成。感染组小鼠在孕10d未检测到虫体,感染孕12d偶见虫体。孕14、16、18d虫体数目明显增多（P〈0.01）,虫体主要位于滋养层细胞内、细胞间质和血管中,并有假包囊形成。结论孕期弓形虫感染可影响胎盘生长,胎盘出现炎症反应和凋亡等病理损害。虫体可侵入胎盘组织细胞间质和血管中,并侵入滋养层细胞内增殖,跨越胎盘屏障传播给胎儿。     

Multicenter Evaluation of Strategies for Serodiagnosis of Primary Infection with Toxoplasma gondii

 The diagnostic performance of single-serum assays for toxoplasma-specific immunoglobulin (Ig)M, IgA, IgG, and IgE antibodies and of different combinations of such antibody assays in 20 European reference centers was assessed. A panel of 276 sera, of which 73 came from patients who seroconverted within 3 months (acute infection), 49 from patients who had seroconverted 3–12 months earlier (convalescence), and 154 from subjects who had two IgG-positive samples obtained 12 months apart (past infection), was tested with 20 toxoplasma-antibody assays and 195 combinations. In general, every assay with high diagnostic sensitivity showed low diagnostic specificity, i.e. no assay performed alone could reliably distinguish acute from past infection. Furthermore, no single assay (or combination) could separate convalescence from the other stages of toxoplasma infection. However, excellent diagnostic performances were reached by sequential use of highly sensitive IgM assays and methods examining IgG avidity or stage specificity. IgA or IgM assays were less suitable for confirmation of toxoplasma-IgM positivity. This study documents the strength of test combinations in assessing the stage of toxoplasma infection.     

Galectin-3 gene inactivation reduces atherosclerotic lesions and adventitial inflammation in ApoE-deficient mice

This study has examined the role of galectin-3 (GaL3), a multicompartmented N-acetyllactosamine-binding chimeric lectin, on atherogenesis in the ApoE-deficient mouse model of atherosclerosis. Pathological changes consisting of atheromatous plaques, atherosclerotic microaneurysms extending into periaortic vascular channels, and adventitial and periaortic inflammatory infiltrates were assessed in an equal number (n = 36) of apolipoprotein (Apo)E-deficient mice and ApoE-GaL3 double-knockout mice. These mice were divided into three age groups, 21 to 23 weeks, 25 to 31 weeks, and 36 to 44 weeks of age. Results of this morphological analysis have shown an age-related increase in the incidence of aorta atheromatous plaques and periaortic vascular channels in ApoE-deficient mice. By contrast ApoE/GaL3 double-knockout mice did not show an increase in pathological changes with age. The 36- to 44-week group of ApoE(-/-)/GaL3(-/-) mice had a significantly lower number of atherosclerotic lesions (P < 0.004) and fewer atheromatous plaques (P < 0.008) when compared with ApoE(-/-)/GaL3+/+ mice of the same age. ApoE(-/-)/GaL3(-/-) mice had a lower number of perivascular inflammatory infiltrates and mast cells than those found in ApoE(-/-)/GaL3+/+ mice. The reduced number of perivascular mast cells may have resulted in a low level of interleukin-4 that contributed to the reduction in the morphological parameters of atherogenesis correlated with the lack of GaL3 expression. The effect of GaL3 deficiency on atherogenesis decrease could be related to its function as a multifunctional protein implicated in macrophage chemotaxis, angiogenesis, lipid loading, and inflammation.     

Protection against Toxoplasma gondii in mice immunized with Toxoplasma cell fractions, RNA and synthetic polyribonucleotides

Mice immunized with fractions obtained by centrifugation of disrupted Toxoplasma gondii trophozoites as well as with 200 μg of Toxoplasma ribonucleic acid (RNA) were resistant (as measured by time to death and total mortality) to challenge with Toxoplasma 30 days later. When mice were challenged at 15 days no protection was noted. A dose of 50 μg of Toxoplasma RNA was effective in protecting mice against lethal challenge only when incorporated into Freund's incomplete adjuvant. In studies performed to determine the specificity of the resistance observed, resistance was also noted in mice immunized with 200 μg of RNA extracted from normal mouse peritoneal macrophages, as well as in mice immunized with 100 μg of the synthetic polyribonucleotide polycytidylic acid. Polyadenylicuridylic acid conferred protection only when incorporated into Freund's incomplete adjuvant and polyinosinic—cytidylic acid had no effect. The protection induced by Toxoplasma RNA was eliminated by prior treatment of the preparation with ribonuclease but not by treatment with pronase, suggesting that the moiety responsible for the protective effect was RNA. In experiments designed to explore the mechanism of resistance in the vaccinated mice, macrophages harvested from mice which had been injected with Toxoplasma RNA 15 days earlier were found to be activated in that they resisted challenge with Listeria monocytogenes.     

Infection of mice with Neospora caninum (Protozoa: Apicomplexa) does not protect against challenge with Toxoplasma gondii.

Neospora caninum and Toxoplasma gondii are structurally related protozoal parasites of mammals that may cause abortion and neonatal morbidity and mortality. Groups of mice were subcutaneously inoculated with 10(5) live zoites of the NC-1 or NC-3 isolates of N. caninum and reinoculated with an identical number of live zoites 2 weeks later. Groups of mice which were injected subcutaneously with Hanks balanced salt solution served as controls. Three weeks after the final N. caninum inoculation, one-half of the mice were inoculated subcutaneously with 2.5 x 10(4) zoites of the RH isolate of T. gondii and the other half were inoculated subcutaneously with 2.5 x 10(4) zoites of the GT-1 isolate of T. gondii. Serum samples taken from mice on the day of T. gondii inoculation were negative for specific antibodies to T. gondii, but mice inoculated with N. caninum had reciprocal titers of greater than or equal to 800 to this protozoan. All of the mice died after challenge with T. gondii, and no significant differences (P greater than 0.05) between the survival times of mice inoculated with either isolate of N. caninum and those of control mice were seen. This study indicates that N. caninum and T. gondii are distinct biologic entities and not closely related isolates.     

经口感染弓形虫在小鼠组织内的动态分布

目的观察经口感染弓形虫速殖子在小鼠小肠组织、实质器官内的动态分布。方法BALB／c小鼠96只．随机分为8组，0d组用0．5ml PBS／只灌胃，其余组用RH株弓形虫速殖子1×10^4个灌胃感染，感染后2、4、6、8、10、12、14d处死小鼠，每次处死12只，取十二指肠、空肠、回肠、肝脏、脾、肾、肺、心和脑做组织印片，吉-瑞氏染色，镜检。结果感染后2d在十二指肠、空肠、回肠、肺和心，4d在脾，6d在肾和肝脏发现虫体，脑内未发现虫体。十二指肠、空肠、回肠组织内虫体数量呈上升趋势，第6天达高峰后稍有下降。肝内虫体数量呈上升趋势，第6天最多；脾内虫体数量在6d达峰值后保持较高水平；实验期间肾、肺和心内虫体数量保持较低水平。结论弓形虫经口感染小鼠后2d，小肠组织出现大量速殖子；同时肺和心内有少量速殖子；4d在脾、6d在肾和肝脏发现虫体；速殖子在上述组织内增殖，并形成假包囊，脑内未发现虫体。     

Regulation and Function of T-Cell-Mediated Immunity during Toxoplasma gondii Infection

The intracellular protozoan Toxoplasma gondii is a widespread opportunistic parasite of humans and animals. Normally, T. gondii establishes itself within brain and skeletal muscle tissues, persisting for the life of the host. Initiating and sustaining strong T-cell-mediated immunity is crucial in preventing the emergence of T. gondii as a serious pathogen. The parasite induces high levels of gamma interferon (IFN-γ) during initial infection as a result of early T-cell as well as natural killer (NK) cell activation. Induction of interleukin-12 by macrophages is a major mechanism driving early IFN-γ synthesis. The latter cytokine, in addition to promoting the differentiation of Th1 effectors, is important in macrophage activation and acquisition of microbicidal functions, such as nitric oxide release. During chronic infection, parasite-specific T lymphocytes release high levels of IFN-γ, which is required to prevent cyst reactivation. T-cell-mediated cytolytic activity against infected cells, while easily demonstrable, plays a secondary role to inflammatory cytokine production. While part of the clinical manifestations of toxoplasmosis results from direct tissue destruction by the parasite, inflammatory cytokine-mediated immunopathologic changes may also contribute to disease progression.     

Protective Role for Interleukin-5 during Chronic Toxoplasma gondii Infection

To investigate the role of interleukin-5 (IL-5) during Toxoplasma gondii infection, IL-5 knockout (KO) mice and C57BL/6 control mice were infected intraperitoneally with ME49 cysts and the course of infection was monitored. The mortality rate during chronic infection was significantly greater in IL-5-deficient animals, and consistent with this finding, the KO mice harbored a greater number of brain cysts and tachyzoites than did their wild-type counterparts. Although the IL-5 KO animals did not succumb until late during infection, increased susceptibility, as measured by accelerated weight loss, was detectable during the acute stages of infection. The amounts of total immunoglobulin (Ig), IgM, and IgG2b were comparable in both strains, while the amount of IgG1 was much smaller in IL-5 KO mice. Spleen cell production of IL-12 in response to T. gondii antigen was approximately threefold lower in the KO strain, and this decrease correlated with a selective loss of B lymphocytes during culture. A link between the presence of B cells and augmented IL-12 production was established by the finding that after removal of B cells with monoclonal antibody and complement, wild-type- and KO-derived cells produced equivalent levels of IL-12 in response to T. gondii antigen. These results demonstrate a protective role of IL-5 against T. gondii infection and suggest that IL-5 may play a role in the production of IL-12.     

Infection with Toxoplasma gondii does not elicit predator aversion in male mice nor increase their attractiveness in terms of mate choice

Behavioral manipulation hypothesis posits that some parasites induce behavioral changes in the host to increase transmission efficiency of the parasite. Protozoan parasite Toxoplasma gondii infecting rats has been widely studied in this context. T. gondii increases attractiveness of infected male rats and reduces innate aversion of rats to cat odor, likely increasing transmission of the parasite by sexual and trophic routes respectively. It is currently unexplored if T. gondii induces gain of male attractiveness in experimental models other than rats. Here we show that laboratory infection of two strains of mice does not induce behavioral manipulation. Moreover, T. gondii infection results in reduction of male attractiveness in one of the strains. In agreement with this observation, T. gondii infection also fails to induce reduction in innate aversion to cat odors in mice. Effects of the parasite on mice mate choice are similar to effects of several other parasites in this animal model. Thus, behavioral change induced by the parasite may be specific to the rodent species.     

霍乱毒素佐剂联合弓形虫ESA鼻内免疫小鼠抗弓形虫感染作用

目的 观察霍乱毒素（cholera toxin,CT）佐剂和弓形虫排泄-分泌抗原（ESA）鼻内免疫小鼠诱导的抗弓形虫感染作用。方法 6周龄BALB/c小鼠60只,随机分为3组,每组20只。分别用PBS 20μl、ESA 20μg或CT 1.0μg＋ESA 20μg每只滴鼻免疫2次,间隔2周。末次免疫后14 d,用4×104个弓形虫速殖子每只灌胃攻击所有小鼠,观察小鼠健康及死亡情况。速殖子攻击后30 d,计数肝、脑组织内弓形虫速殖子。结果 CT作为佐剂联合弓形虫ESA滴鼻免疫小鼠的健康状况明显好于PBS组和ESA组,存活率（95%）也显著高于PBS组（55%）。与PBS组相比,CT＋ESA组肝和脑组织内速殖子数分别减少了80.19%（P〈0.001）和78.24%（P〈0.005）。CT作为佐剂联合ESA滴鼻免疫小鼠诱导了高水平的黏膜免疫应答和系统免疫应答。结论 CT作为佐剂联合弓形虫ESA滴鼻免疫小鼠诱导的免疫应答可有效抵抗弓形虫速殖子攻击。     

Expression of SAG-1 of Toxoplasma gondii in transgenic mice

We describe the expression of SAG-1 cDNA in B6C3F1 mice by microinjecting a 3.3 kbp DNA fragment, consisting of the cytomegalovirus enhancer-chicken β-actin hybrid promoter and SAG-1 into the pronucleus of a fertilized egg at the one-cell stage. Offspring derived from this microinjection were analyzed for the integration and functional expression of the SAG-1 transgene. Steady-state expressions of both the mRNA for SAG-1 and SAG-1 protein product were detected in the brain, thymus, spleen and liver. Approximately 50% of F1 and F2 progeny inherited the SAG-1 transgene from SAG-1 transgenic mice in Mendelian fashion. These results indicated that SAG-1 transgenic lines were established. Transgenic mice harboring the SAG-1 gene will contribute a critical tool of defining the molecular mechanisms of SAG-1 in pathogenesis and host immune response. Received: 28 September 1999 / Accepted: 14 October 1999     

CXCR7在动脉粥样硬化模型ApoE-/-小鼠的表达及阿托伐他汀的干预作用

 目的: 研究CXC趋化因子受体7(CXC chemokine receptor 7,CXCR7)在动脉粥样硬化模型载脂蛋白E基因敲除(ApoE^-/-)小鼠中的表达并探究阿托伐他汀的干预作用。方法: 8周龄ApoE^-/-雄性小鼠,随机分为正常对照组、高脂组与高脂+阿托伐他汀组,实验干预12周建立动脉粥样硬化模型;油红O及HE染色观察动脉粥样硬化病变,Western blot及免疫组化法检测动脉CXCR7的表达,Western blot检测动脉eNOS和Akt的表达。结果: (1)动脉油红O及HE染色示高脂组可见有明显粥样核心及纤维帽的显著斑块,高脂+阿托伐他汀组也可见斑块,但斑块负荷较模型组减轻,正常对照组未见明显斑块形成;(2)免疫组化示高脂组动脉细胞着色浅,CXCR7表达量少,高脂+阿托伐他汀组与高脂组比较,细胞着色增加,CXCR7表达量增加,正常对照组颗粒呈深棕黄色,示CXCR7大量表达;(3)Western blot结果示高脂组CXCR7、eNOS和Akt的表达较正常对照组降低,给予阿托伐他汀干预后CXCR7、eNOS和Akt的表达较高脂组增加,较正常对照组相比CXCR7、eNOS和Akt的表达下降,但磷酸化eNOS的水平未见差异。结论: 高脂血症可损伤血管内皮,促进动脉粥样硬化的发展,下调动脉CXCR7、eNOS和Akt的表达;阿托伐他汀可改善动脉粥样硬化,缓解ApoE^-/-小鼠动脉CXCR7、eNOS和Akt蛋白表达的下调。     

Inflammatory Monocytes but Not Neutrophils Are Necessary To Control Infection with Toxoplasma gondii in Mice

Previous studies have suggested that both inflammatory monocytes and neutrophils are important for controlling acute toxoplasmosis in the mouse model. To test the role of these cell types, we used monoclonal antibody (MAb) RB6-8C5 to deplete both subsets of cells or MAb 1A8 to selectively remove neutrophils. RB6-8C5 MAb-treated mice succumbed to oral infection with Toxoplasma gondii, similar to Ccr2^−/− mice, which are deficient in monocyte recruitment but have normal neutrophils. In contrast, mice treated with MAb 1A8 controlled parasite replication and survived acute infection. Ccr2^−/− mice suffered from acute ileitis and inflammation in the spleen that was associated with a lack of inflammatory monocytes and elevated numbers of neutrophils. RB6-8C5 MAb-treated C57BL/6 mice also suffered from intestinal pathology and splenic damage, although this was less extensive due to the reduced numbers of neutrophils. Neutrophil-depleted infected wild-type mice displayed no pathological changes, compared to untreated infected controls. Collectively, these observations demonstrate the critical role of inflammatory monocytes during the acute infection with the parasite T. gondii and reveal that neutrophils are not protective but rather contribute to the pathology.The intracellular parasite Toxoplasma gondii is an opportunistic pathogen that infects approximately one-third of the human population worldwide (19). Following oral infection, the parasite crosses the intestinal epithelium, disseminates widely, and traverses biological barriers such as the blood-brain barrier to reach immunologically privileged sites, where it causes the most severe pathology (3). Histopathological studies document initial invasion into a variety of cell types in the intestine, including CD11b⁺ and CD11c⁺ intraepithelial leukocytes, which have been implicated in dissemination of the parasite (11). We previously demonstrated that the numbers of Gr1⁺ inflammatory monocytes dramatically increase in the lamina propria of the small intestine in response to T. gondii infection and that these cells play a crucial role in protection against the parasite (14).Murine monocytes have been classified in two subpopulations based on different surface markers and phenotypic characteristics (17, 18). Inflammatory monocytes (CD115⁺, Gr1⁺, F4/80⁺, CD11b⁺, and CX₃CR1^lo) express chemokine receptor 2 (CCR2), emerge from the bone marrow in response to chemokines such as MCP1 (CCL2), and home to sites of inflammation (17, 18). These precursors have the potential to differentiate into dendritic cells (CD11c⁺) and to populate nonlymphoid tissues such as the lamina propria (33). The other major subset of monocytes (Gr1⁻, F4/80⁺, CD11b⁺, and CX₃CR1^hi) are primarily distributed as resident tissue macrophages, which provide surveillance functions (2). Following oral challenge with T. gondii, inflammatory monocytes upregulate inducible nitric oxide synthase (iNOS), produce interleukin-12 (IL-12), and secreted tumor necrosis factor alpha (TNF-α) in response to T. gondii infection (23, 24). Collectively, these responses likely contribute to the control of parasite replication at the site of primary infection in the small intestine (14). Mice deleted in the gene for chemokine receptor 2 (CCR2), or the major chemokine ligand (CCL2) for this receptor, fail to recruit inflammatory monocytes to the lamina propria in response to T. gondii infection (14). The resulting inability to control parasite replication within the small intestine is associated with neutrophil efflux, tissue destruction, and death of mice due to intestinal necrosis (14). Damage to the small intestine following oral infection with T. gondii is also decreased by the genetic absence of the IL-17 receptor (IL-17R), implicating a role for neutrophils in this pathology (20). Collectively, these findings establish the critical role of inflammatory monocytes in innate mucosal immunity but suggest that neutrophils may contribute to enhanced pathology.Neutrophils contain numerous potent antimicrobial effectors, and they rapidly accumulate at the sites of many bacterial infections (21). Neutrophils produce several cytokines and chemokines, such as IL-1β, IL-12, TNF-α, MIP-1, and MIP-2, and hence, they recruit and activate other immune cells (27). There is also evidence that neutrophils influence the T-cell response by enhancing the functions of dendritic cells (32) or inflammatory monocytes (30). Infection of mice by intraperitoneal (i.p.) inoculation with low numbers of a highly virulent strain of T. gondii or with a high inoculum of low-virulence strains results in recruitment of neutrophils to the peritoneal cavity (4, 22). Mouse and human neutrophils challenged in vitro with T. gondii also produce IL-12, TNF-α, MIP-1α, and MIP-1β (6, 7). It has been suggested that neutrophils are protective during acute toxoplasmosis in the mouse based on depletion with MAb RB6-8C5 (5, 26), which results in enhanced susceptibility. However, much more modest effects are observed in mice lacking the major neutrophil chemokine receptor CXCR2, and these animals survive acute infection but develop slightly higher chronic tissue burdens (13). These apparently discordant results might reflect the different genetic backgrounds used in these prior studies, since antibody depletion studies were done with susceptible C57BL/6 mice, while CXCR2^−/− mice were in the resistant BALB/c background.The anti-granulocyte receptor 1 (Gr1) monoclonal antibody (MAb) RB6-8C5 has been used extensively to deplete neutrophils in mice and to investigate the role of these cells in host defense to bacterial and protozoal infections (8-10, 21, 31). RB6-8C5 binds to Ly6G, which is present on the surface of neutrophils, and to Ly6C, which is expressed on neutrophils, dendritic cells, and subpopulations of lymphocytes and monocytes (15). In vivo administration of RB6-8C5 depletes not only neutrophils (CD11b⁺, F4/80⁻, Ly6C^int [where int is intermediate], and Ly6G^hi) but also inflammatory monocytes (CD11b⁺, F4/80⁺, Ly6C^hi, and Ly6G⁻) (12), thus complicating the interpretation of studies using this antibody for neutralization. The Ly6G-specific MAb 1A8 has recently been reported to be an alternative method to selectively deplete neutrophils (12).In the present study, we sought to determine the respective roles of inflammatory monocytes and neutrophils in the pathogenesis and control of T. gondii in mice. We compared the outcome of oral challenge with T. gondii in mice depleted of neutrophils and monocytes with MAb RB6-8C5 and that of mice where neutrophils were selectively depleted with MAb 1A8.     

Autophagy activated by Toxoplasma gondii infection in turn facilitates Toxoplasma gondii proliferation

Autophagy was found to play an antimicrobial or antiparasitic role in the activation of host cells to defend against intracellular pathogens, at the same time, pathogens could compete with host cell and take advantage of autophagy to provide access for its proliferation, but there are few articles for studying the outcome of this competition between host cell and pathogens. Therefore, the aim of our study was to investigate the relationship between autophagy activated by Toxoplasma gondii (T. gondii) and proliferation of T. gondii affected by autophagy in vitro. Firstly, human embryonic fibroblasts (HEF) cells were infected with T. gondii for different times. The monodansylcadaverine (MDC) staining, acridine orange (AO) staining, punctuate GFP-LC3 distribution, and transmission electron microscopy (TEM) assays were conducted, and the results were consistent in showing that gondii infection could induce autophagy. Secondly, HEF cells were infected with T. gondii and treated with autophagy inhibitor bafilomycin A1 or inducer lithium chloride for different times. Giemsa staining was conducted, and the results exhibited that T. gondii infection-induced autophagy could in turn promote T. gondii proliferation. Simultaneously, the results of Giemsa staining also revealed that autophagy inhibitor could reduce the number of each cell infected with T. gondii and inhibit T. gondii proliferation. In contrast, autophagy inducer could increase the number of each cell infected with T. gondii and encourage T. gondii proliferation. Therefore, our study suggests that T. gondii infection could activate autophagy, and this autophagy could in turn facilitate T. gondii proliferation in HEF cells for limiting nutrients.