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.     

非小细胞型肺癌与弓形虫感染的关系

目的： 探讨非小细胞型肺癌（NSCLC）患者弓形虫(TOX)感染的状况。 方法: 用酶联免疫法(ELISA)检测168例NSCLC患者、同期住院的90例非肿瘤且无自身免疫性疾病患者以及90例健康体检者血中弓形虫循环抗原(TOX-CAg)、TOX-IgG及TOX-IgM抗体阳性率，比较各组间以及NSCLC组内性别、肿瘤分期和病理类型的弓形虫阳性率差异。 结果: 168例NSCLC患者血清中TOX-CAg阳性者34例(20.2%)，TOX-IgM阳性者36例(21.4%)，TOX-IgG阳性者27例(16.1%)；而90例其它疾病患者血清中3者分别为9例(10.0%)、10例(11.1%)和6例(6.7%)，90例健康组血清中3者分别为3例(3.3%)、4例(4.4%)和4例(4.4%)；NSCLC组与其它疾病组的TOX-CAg、IgG及IgM阳性率差异均有显著性(P<0.05)，NSCLC组与健康组的TOX-CAg、IgG及IgM差异更明显(P<0.01)，其它疾病组与健康组的TOX-CAg、IgG及IgM差异不明显(P>0.05)；另外，在肺癌分期方面，对于TOX-CAg和TOX-IgM，Ⅰ、Ⅱ期间无明显差异(P>0.05)，Ⅲ、Ⅳ期间也无明显差异(P>0.05)，但Ⅰ、Ⅱ期与Ⅲ期间差异显著（P<0.05），Ⅰ、Ⅱ期与Ⅳ期间差异显著（P<0.05或P<0.01），对于TOX-IgG抗体，各肿瘤分期间无明显差异(P>0.05)；肺腺、鳞癌与其它病理类型间无明显差异(P>0.05)；男女间无明显差异（P>0.05）。 结论: 非小细胞型肺癌患者的弓形虫感染率明显高于其他人，而且晚期肺癌的弓形虫感染率高于早期肺癌。     

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.     

Tissue barriers of the human placenta to infection with Toxoplasma gondii

Toxoplasma gondii is a ubiquitous, obligate intracellular parasite capable of crossing the placenta to cause spontaneous abortion, preterm labor, or significant disease in the surviving neonate. Exploration of the cellular and histological components of the placental barrier is in its infancy, and both how and where T. gondii breaches it are unknown. The human placenta presents two anatomical interfaces between maternal cells and fetal cells (trophoblasts): (i) the villous region where maternal blood bathes syncytialized trophoblasts for nutrient exchange and (ii) the maternal decidua, where mononuclear, extravillous trophoblasts anchor the villous region to the uterus. Using first-trimester human placental explants, we demonstrate that the latter site is significantly more vulnerable to infection, despite presenting a vastly smaller surface. This is consistent with past findings concerning two vertically transmitted viruses and one bacterium. We further explore whether three genetically distinct T. gondii types (I, II, and III) are capable of preferential placental infection and survival in this model. We find no difference in these strains' ability to infect placental explants; however, slightly slower growth is evident in type II (Prugniaud [Pru]) parasites relative to other cell types, although this did not quite achieve statistical significance.     

Two case reports of pituitary adenoma associated with Toxoplasma gondii infection

The involvement of the pituitary in cases of toxoplasmosis has been described in the literature only rarely. This is the first report to describe pituitary adenoma in association with Toxoplasma gondii infection. The two patients were 43 and 19 year old women. Radiological examination revealed tumours in the sellar region. Microscopically, the tumours consisted of small homogeneous polygonal or round cells. Toxoplasma cysts were found among the tumour cells, a finding confirmed by Toxoplasma gondii specific antibody immunohistochemistry. The association between pituitary adenoma and toxoplasma raises the possibility that T gondii might be involved in the development of certain cases of pituitary adenoma.     

Migratory activation of primary cortical microglia upon infection with Toxoplasma gondii

Disseminated toxoplasmosis in the central nervous system (CNS) is often accompanied by a lethal outcome. Studies with murine models of infection have focused on the role of systemic immunity in control of toxoplasmic encephalitis, while knowledge remains limited on the contributions of resident cells with immune functions in the CNS. In this study, the role of glial cells was addressed in the setting of recrudescent Toxoplasma infection in mice. Activated astrocytes and microglia were observed in the close vicinity of foci with replicating parasites in situ in the brain parenchyma. Toxoplasma gondii tachyzoites were allowed to infect primary microglia and astrocytes in vitro. Microglia were permissive to parasite replication, and infected microglia readily transmigrated across transwell membranes and cell monolayers. Thus, infected microglia, but not astrocytes, exhibited a hypermotility phenotype reminiscent of that recently described for infected dendritic cells. In contrast to gamma interferon-activated microglia, Toxoplasma-infected microglia did not upregulate major histocompatibility complex (MHC) class II molecules and the costimulatory molecule CD86. Yet Toxoplasma-infected microglia and astrocytes exhibited increased sensitivity to T cell-mediated killing, leading to rapid parasite transfer to effector T cells in vitro. We hypothesize that glial cells and T cells, besides their role in triggering antiparasite immunity, may also act as "Trojan horses," paradoxically facilitating dissemination of Toxoplasma within the CNS. To our knowledge, this constitutes the first report of migratory activation of a resident CNS cell by an intracellular parasite.     

Serodiagnosis of recently acquired Toxoplasma gondii infection with a recombinant antigen

A portion of a cDNA encoding a 35-kDa antigen from Toxoplasma gondii was cloned into the CKS expression vector and expressed in Escherichia coli. By using the enzyme-linked immunosorbent assay (ELISA), the recombinant protein (rP35 antigen) was examined for reactivity with immunoglobulin G (IgG) antibodies in the sera of pregnant women. Of these women, 41 had a toxoplasma serologic profile suggestive of recently acquired T. gondii infection (Sabin-Feldman dye test [DT] titers from 1:256 to 1:32,000, positive IgM ELISA titers from 2.3 to 9.7, positive IgA ELISA from 1 to >28, and acute patterns in the differential agglutination [AC/HS] test) (group I), and 50 women had a toxoplasma serologic profile suggestive of infection acquired in the distant past (low DT titers from 1:16 to 1:512, negative IgM ELISA titers from 0 to 0.8, and chronic patterns in the AC/HS test) (group II). The classification of acute or chronic profile was based on the individual's clinical history as well as the combination of the results of the toxoplasma serological profile. An additional group (group III) was composed of sera from 50 women who were seronegative for T. gondii antibodies in the DT. The results revealed that whereas 85.3% of women in group I had IgG antibodies that reacted with the rP35 antigen, only 8% of women in group II had IgG antibodies that reacted with the same antigen. In immunoblots, the rP35 antigen was recognized by IgG antibodies in a pool of sera from individuals with a toxoplasma serologic profile compatible with acute infection but not in a pool of sera from individuals with a serologic profile characteristic of a chronic infection. These results reveal that IgG antibodies against the P35 antigen are produced during the acute stage of the infection but are uncommon in the latent or chronic phase of the infection. Thus, the rP35 antigen may be a useful serologic marker to differentiate between recently acquired infection and that acquired in the more distant past.     

Studies of efferent lymph cells from nodes stimulated with oxazolone.

Efferent lymph from nodes regional to areas of skin that had been treated with solutions of oxazolone in acetone was collected from unanaesthetized sheep. The application of 5% solutions of oxazolone to unsensitized sheep caused no signs of acute inflammation or ''shut-down'' of lymphocyte traffic; none the less, normal immune responses ensued so that immunoblasts, some containing immunoglobulin, were discharged into the lymph together with specific humoral antibodies. When previously sensitized sheep were challenged with 2.5% solutions of oxazolone the vigorous secondary responses were heralded by Arthus reactions, induced presumably by pre-existing antibodies, which were mainly of the IgG class. A similar sequence of events occurred in a thymus-deprived sheep which had undergone intra-uterine thymectomy at 60 days of gestation. Repeated applications of oxazolone to normal sheep did not exhaust or inhibit the characteristic changes in the flow and composition of the lymph. When immunoblasts from efferent lymph were radiolabeled with 125I-UdR and returned intravenously to the sheep they showed no significant tendency to localize either specifically or non-specifically in areas of skin that had been treated with contact-sensitizing chemicals.     

Toxoplasma gondii infection in the peritoneal macrophages of rats treated with glucocorticoids

It is well known that toxoplasmosis can be life threatening to immunocompromised individuals such as AIDS and organ transplantation patients. Glucocorticoids (GCs) are widely used in the clinic for the treatment of autoimmune diseases and organ transplantation resulting in acute toxoplasmosis in these patients. However, the interaction and mechanism between the development of acute toxoplasmosis and GC therapy are still unknown. The aims of this study were to investigate the infection of Toxoplasma gondii in the peritoneal macrophages of rats treated with glucocorticoids. Our results showed that the growth rate of T. gondii RH strain was significantly increased in the peritoneal macrophages of rats treated with glucocorticoids in vivo. For instance, 242 (±16) tachyzoites were found in 100 macrophages from the rats treated with methylprednisolone (MP), while only 16 (±4) tachyzoites were counted in the macrophages from the non-treated control rats 24 h after infection (P?<?0.01). We also demonstrated that a significant inhibition of nitric oxide (NO) production was detected in the macrophages collected from the rats post-treated with GCs with 12.90 μM (±0.99 μM) of nitrite production from the rats treated with MP, while 30.85 μM (±1.62 μM) was found in the non-treated control rats 36 h after incubation (P?<?0.01). Furthermore, glucocorticoids could significantly inhibit the expression of inducible nitric oxide synthase mRNA and its protein in the rat peritoneal macrophages. Our results strongly indicate that the decrease of NO in the rat peritoneal macrophages is closely linked to the cause of acute toxoplasmosis in the host. Additionally, there was a significant increase in the number of cysts produced by the naturally cyst forming, T. gondii Prugniaud strain with an average of 2,795 (±422) cysts of the parasite being detected in the brains of the rats treated with dexamethasone, while only 1,356 (±490) cysts were found in the non-treated control animals (P?<?0.01). As rats and humans are both naturally resistant to T. gondii infection, these novel data could lead to a better understanding of the development of acute toxoplasmosis during glucocorticoid therapy in humans.     

Seroepidemiological and biomolecular survey on Toxoplasma gondii infection on organic pig farms

Parasitology Research - Pigs are an important reservoir of Toxoplasma gondii, and pork meat is considered one of the main sources of human infection. The present survey assesses the prevalence of...     

Development of granulomatous common variable immunodeficiency subsequent to infection with Toxoplasma gondii

Common variable immunodeficiency (CVID) is a heterogeneous immunodeficiency that is accompanied by granulomatous lesions in 5-10% of cases. Why some patients develop granulomatous disease remains unclear. Here we describe a 12-year-old previously healthy girl who presented with pancytopenia and granulomatous lymphoproliferation subsequent to infection with Toxoplasma gondii. Loosely arranged non-fibrosing granulomas were observed in the liver, lymph nodes and lung, but no Toxoplasma tachyzoites could be demonstrated and polymerase chain reaction (PCR) and culture were negative for Toxoplasma and a wide range of other pathogens. While the patient had a normal peripheral B cell status at presentation, the development of CVID could be observed during the following months, leading to a loss of memory B cells. This was accompanied by an increasingly activated CD4(+) T cell compartment and high serum levels of angiotensin-converting enzyme (ACE), tumour necrosis factor (TNF) and sCD25. Steroid therapy reduced pancytopenia, granulomatous lymphoproliferation and cytokine elevations, but did not improve the B cell status. This is the first report of an association of Toxoplasma infection with granulomatous CVID and provides one of the rare examples where the onset of CVID could be documented subsequent to an infectious disease.     

Effect of sex hormones on the response of mice to infection with Toxoplasma gondii

Groups of male and female mice were gonadectomized and some implanted with a pellet of hexoestrol. Half of the animals in each group, including controls, were infected with a low-virulence strain of Toxoplasma gondii. The animals were killed 6 weeks after infection. Gonadectomy increased the relative thymic weight in both sexes, but more so in the male, and the paracortical area of the lymph node was enlarged, as was the thymus-dependent area of the spleen. Hexoestrol administration induced almost complete thymic atrophy and partial involution of the peripheral lymphoid tissues. Greater resistance to toxoplasmic infection was found in the gonadectomized mice than in controls of both sexes, possibly due to a better cell-mediated immunity in the gonadectomized animals. Overwhelming toxoplasmosis with increased mortality was found in the hexoestrol-treated mice after infection, probably resulting from a depression of cell-mediated immunity caused by hexoestrol. It is postulated that the cellular immune response is of greater importance than the formation of antibody in resistance to toxoplasmic infection. The role of the thymolmphatic--sex hormonal interrelation on the age--sex differences seen in the incidence of toxoplasmic lymphadenopathy is also discussed.     

Gamma interferon induces Fas-dependent apoptosis of Peyer's patch T cells in mice following peroral infection with Toxoplasma gondii.

Since we previously observed a remarkable decrease in the numbers of T cells in the Peyer's patches of the small intestines in C57BL/6 mice following peroral infection with Toxoplasma gondii, we performed studies to examine the mechanism(s) whereby this decrease in numbers of the T cells occurs. We found that apoptotic cell death of CD4+ and CD8+ alphabeta T cells occurred in Peyer's patches following infection. Upregulation of Fas expression was observed in these T cells. C57BL/6-background mutant mice which lack functional Fas antigen did not develop apoptosis in their Peyer's patches following infection. Treatment of infected C57BL/6 mice with anti-gamma interferon (IFN-gamma) monoclonal antibodies prevented the upregulation of Fas on their Peyer's patch T cells and inhibited the occurrence of apoptosis of these T cells. These results indicate that IFN-gamma induces Fas-dependent apoptosis in CD4+ and CD8+ alphabeta T cells in Peyer's patches in C57BL/6 mice following peroral infection with T. gondii.