Direct effects of IL-4/IL-13 and the nematode Nippostrongylus brasiliensis on intestinal epithelial cells in vitro

Nematode infections induce the upregulation of mucin- and glycosylation-related genes in intestinal epithelial cells in vivo. However, the factor(s) that induce these changes in epithelial cells have not been fully elucidated. In the present study, we analysed the effects of the Th2 cytokines IL-4 and IL-13 and the excretory-secretory (ES) product of the nematode Nippostrongylus brasiliensis on the gene expression of the major mucin core peptide MUC2, the sialyltransferase ST3GalIV (Siat4c) and the sulphotransferase HS3ST1 in intestinal epithelium-derived IEC-6 cells by quantitative reverse transcription (RT)-PCR. The administration of IL-4 and IL-13 resulted in a significant upregulation of ST3GalIV and HS3ST1 gene transcription, but had no effect on MUC2, in IEC-6 cells. RT-PCR studies also demonstrated the constitutive expression of IL-13Ralpha1 and IL-4R in IEC-6 cells. On the other hand, the ES product induced upregulation of ST3GalIV, but not HS3ST1 or MUC2, while coadministration of IL-13 and the ES product induced a slight but significant upregulation of MUC2. Co-incubation of live N. brasiliensis adult worms with IEC-6 cells resulted in the upregulation of ST3GalIV and MUC2. These results suggested that HS3ST1 gene expression is strictly regulated by IL-4/IL-13, while ST3GalIV and MUC2 gene expressions are regulated by redundant mechanisms.

Depleted intestinal goblet cells and severe pathological changes in SCID mice infected with Heligmosomoides polygyrus

To determine the role of T cells and mast cells in intestinal pathology and immune expulsion of intestinal nematodes, worm burdens, goblet cell responses and villus structures were analysed in T- and B-cell-deficient severe combined immunodeficiency (SCID) mice, athymic nu/nu mice and mast cell deficient W/W(v) mice after infection with the nematode Heligmosomoides polygyrus. SCID and nu/nu mice showed significantly higher worm burdens at week 9 post-infection compared with the wild-type controls. SCID and nu/nu mice showed compromised goblet cell hyperplasia and/or Muc 2 expression, indicating that both events are T-cell dependant. On the other hand, the SCID mice showed increased pathology (villus atrophy and crypt hyperplasia) and increased numbers of proliferating cell nuclear antigen positive cells compared to the wild-type controls. W/W(v) mice, conversely, were able to expel the worms normally, had normal goblet cell hyperplasia, and did not demonstrate the changes in mucosal architecture seen in SCID mice, confirming that a normal mast cell response is not necessarily required for these changes. These results suggest that a functional T-cell response, but not a mast cell response, is necessary for anti-parasite responses, goblet cell function, and maintaining normal mucosal architecture.

Activation of caspases in intestinal villus epithelial cells of normal and nematode infected rats

BACKGROUND

Small intestinal epithelial cells (IEC) show apoptosis in physiological turnover of cells and in certain inflammatory diseases.

AIMS

To investigate the role of caspases in the progression of IEC apoptosis in vivo.

METHODS

IEC were separated along the villus-crypt axis from the jejunum of normal and Nippostrongylus brasiliensis infected rats at 4 degrees C. Caspases were examined by a fluorometric assay method, histochemistry, and immunoblotting.

RESULTS

Villus cell rich IEC from normal rats exhibited a high level of caspase-3-like activity whereas activities of caspase-1, -8, and -9 were negligible. Immunoblotting analysis of villus cell rich IEC revealed partial cleavage of procaspase-3 into a 17 kDa molecule as well as cleavage of a caspase-3 substrate, poly(ADP-ribose) polymerase (PARP), whereas in crypt cell rich IEC, caspase-3 cleavage was less significant. Caspase-3 activity was also observed histochemically in villus epithelium on frozen sections of the normal small intestine. IEC prepared at 4 degrees C did not reveal nuclear degradation whereas subsequent incubation in a suspension at 37 degrees C induced intense nuclear degradation within one hour in accordance with increases in active caspase-3. This apoptosis was partially suppressed by the caspase inhibitor Z-VAD-fmk. Nematode infected animals showed villus atrophy together with significant increases in levels of caspase-3 in IEC but not of caspase-1, -8, or -9.

CONCLUSION

Caspase-3 may have an important role in the physiological replacement of IEC as well as in progression of IEC apoptosis induced by nematode infection.

E-cadherin and cadherin-associated cytoplasmic proteins are expressed in murine mast cells

Cadherins, calcium-dependent cell adhesion molecules, play crucial roles, not only in the maintenance of tissue integrity, but also in the regulation of many aspects of cell behavior. We investigated the expression of "classic" E-, N- and P-cadherins in bone marrow-derived cultured mast cells (BMMC) and peritoneal mast cells (PMC) from mice. Flow cytometric analysis and immunocytochemical staining indicated that E-cadherin was expressed on the cell surface of BMMC and also at lower levels on PMC. N-cadherin was also expressed on the surface of BMMC, but not of PMC, whereas P-cadherin expression was seen in neither cell type. Significant expression of E- and N-cadherin mRNA was observed in BMMC by reverse transcriptase-polymerase chain reaction (RT-PCR), but PMC expressed only E-cadherin mRNA. Western blotting analysis indicated expression of alpha- and beta-catenins and p120-catenin (or p120 cas) in BMMC, whereas PMC showed less intense expression of alpha- and beta-catenins with high levels of p120 expression. Analyses of beta-catenin or E-cadherin immunoprecipitates from BMMC lysate revealed that alpha-catenin, beta-catenin, and E-cadherin were co-precipitated, suggesting that E-cadherin and catenins form a complex in mast cells. Addition of a blocking antibody of homophilic E-cadherin interactions, or a synthetic E-cadherin-binding decapeptide containing the histidine-alanine-valine (HAV) sequence in methylcellulose cultures of gut intraepithelial mononuclear cells or BMMC, significantly suppressed the clonal growth of mast cells. Furthermore, the blocking antibody or synthetic decapeptide significantly suppressed BMMC adhesion to E-cadherin-expressing F9 cell monolayers. These results indicated that E-cadherin and associated cytoplasmic proteins in mast cells might be involved in the regulation of certain stages of mast cell differentiation and cell-cell interactions.

Migration of neutrophils is dependent on mast cells in nonspecific pleurisy in rats

To determine the role of mast cells in the recruitment of neutrophils and eosinophils, acute nonspecific pleurisy was induced by injecting isologous serum into normal +/+ and mast cell-deficient Ws/Ws rats. In +/+ rats, neutrophil infiltration peaked 4 h after serum administration, followed by influx of eosinophils after 24-48 h. The levels of neutrophil influx after 4 h as well as the activity of myeloperoxidase (MPO) in pleural lavage-cell extract were significantly lower in Ws/Ws rats than in +/+ rats. In contrast, numbers of eosinophils as well as activity of eosinophil peroxidase (EPO) did not differ significantly between Ws/Ws and +/+ rats. For local reconstitution of mast cells, +/+ rat peritoneal mast cells (PMC) or mesenteric lymph node cells (MLNC) as a control were transferred into the Ws/ Ws pleural cavity. Serum injection into animals with PMC transfer 7 days previously triggered augmented neutrophil influx by approximately 4.7-fold as compared to that in MLNC-transferred animals. Mast cells recovered from the pleural cavity of PMC-transferred rats showed histamine contents equivalent to 20% of that of freshly isolated PMC and retained the reactivity to compound 48/80. These results indicated that dependency of neutrophil recruitment on resident mast cells is greater than that of eosinophils in isologous serum-induced pleurisy.

Enhancement of apoptosis with loss of cellular adherence in the villus epithelium of the small intestine after infection with the nematode Nippostrongylus brasiliensis in rats

It has been reported that infection with Nippostrongylus brasiliensis induces villus atrophy with various histological alterations. In N. brasiliensis-infected rats, villus length in the jejunum was reduced significantly at day 10 p.i., when serum levels of rat mast cell protease (RMCP) II had increased significantly. To determine whether the villus atrophy is associated with enhancement of apoptosis, apoptotic nuclei were labelled using the nick end-labelling method. Numbers of labelled cells were markedly increased in the villus epithelium at 7-10 days p.i., while the numbers returned to normal 14 days p.i. when worms were rejected from the intestine and villus length became normal. Examination of the expression of the adhesion molecule E-cadherin showed granular immunoreactivity in the cytoplasm of atrophic villus epithelium with loss of normal localization to epithelial cell borders. In mast cell-deficient Ws/Ws rats, villus length was reduced as significantly as in +/+ counterparts at day 10 p.i. with marked increases in the numbers of apoptotic cells. These results suggested that villus atrophy was closely associated with enhanced apoptosis and loss of adhesion in epithelial cells. Mast cell activation appears not to be involved in these alterations.

Lack of active lung anaphylaxis in congenitally mast cell-deficient Ws/Ws rats sensitized with the nematode Nippostrongylus brasiliensis

Ws/Ws rats are deficient in both mucosal- and connective tissue-type mast cells. To study the role of mast cells in active anaphylaxis, changes in vascular permeability in the trachea upon intravenous antigen challenge with Evans blue dye were examined in Ws/Ws, heterogenic Ws/+, and normal +/ + rats sensitized with the nematode Nippostrongylus brasiliensis. Antigen challenge resulted in fatal anaphylactic shock in some +/+ and Ws/+ rats, but not in Ws/Ws rats. Marked dye leakage developed within 30 min in the trachea of +/+ and Ws/+ rats, while Ws/Ws rats showed no substantial increases in the levels of vascular permeability. Ex vivo stimulation of sensitized lung fragments from +/+ animals with specific antigen induced significant releases of histamine and leukotriene (LT) C4, while sensitized Ws/Ws rat-lung fragments did not. In Ws/Ws rats, levels of nematode-specific IgE, IgG1 and IgG2a antibodies as well as levels of lung eosinophilia were not significantly different from those in +/+ rats. These results show that mast cell-deficient Ws/Ws rats fail to develop active anaphylaxis, and this is mediated probably by the lack of mast cell-derived mediators required for initiation of the reaction.

Early increase of gut intraepithelial mast cell precursors following Strongyloides venezuelensis infection in mice

The time-course of differentiation/proliferation of mast cells in gut epithelium was investigated in mice infected with the nematode Strongyloides venezuelensis. After infection, expression of proliferating cell nuclear antigen increased in gut intraepithelial mast cells on days 7 to 11, followed by an increase in the number of intraepithelial mast cells from days 11 to 14. Mast cell precursors were defined as cells that formed mast cell colonies in methylcellulose culture. After infection, the numbers of mast cell precursors in the population of gut intraepithelial mononuclear cells (IEMNC) increased significantly on day 3 and returned to the pre-infection level by day 7. Mast cell precursors in Peyer's patches, mesenteric lymph nodes (MLN), and spleen also increased from day 7 p.i. Production of IL-3 and IL-4 in MLN and spleen were increased between 7 and 11 days p.i. These results show that murine intestinal mastocytosis is initiated by an early increase in mast cell precursor number in the gut epithelium followed by proliferation/differentiation of mast cells. Mast cell precursor numbers increased even before the production of IL-3 and IL-4 in MLN and spleen, suggesting that some local factors might be involved in this phenomenon.

Lung granulomatous response induced by infection with the intestinal nematode Nippostrongylus brasiliensis is suppressed in mast cell-deficient Ws/Ws rats

Certain nematode infections induce eosinophil infiltration and granulomatous responses in the lungs. To examine the role of mast cells in the development of lung lesions, normal +/+ and genetically mast cell-deficient Ws/Ws rats were infected with the nematode Nippostrongylus brasiliensis. In +/+ rats, numbers of eosinophils in bronchoalveolar lavage fluid (BALF) increased significantly 3-7 days after infection, and granulomatous responses composed of histiocytes/ macrophages and multinucleate giant cells were triggered in the lungs 3-14 days after infection. Challenge infection, which was carried out on day 28 after primary infection, induced much higher levels of granulomatous response than after primary infection, suggesting that the response is mediated at least in part by an immunological mechanism. In Ws/Ws rats, both the eosinophil percentage in BALF and the size of the granulomas in the lungs were significantly smaller than in +/+ rats after primary as well as after challenge infection. The amount of rat mast cell protease (RMCP) II in +/+ rat BALF was increased 1 day after primary infection and more significantly after challenge infection, suggesting that lung mucosal mast cells were activated more markedly after the challenge infection. In Ws/Ws rats, RMCP II was undetectable throughout the observation period. The time course of nematode migration in the lungs did not differ in +/+ and Ws/Ws rats. These results suggest that mast cell activation might be relevant to eosinophil infiltration and granulomatous response in the lungs, although the responses do not affect lung migration of the nematode.

Dissociation of early and late protective immunity to the nematode Nippostrongylus brasiliensis in Brown Norway and Fischer-344 rats

Worm expulsion of, and IgE and interferon (IFN)-gamma responses to, Nippostrongylus brasiliensis were studied in 2 rat strains, Brown Norway (BN) and Fischer (F)-344. BN rats expelled the majority of worms by day 14 post-infection (p.i.) with approximately 6% of worms surviving for at least 3 weeks. In F-344 rats, worm expulsion was delayed by 2 days relative to that in BN, while the numbers of residual worms were significantly fewer than in BN, suggesting that different immune mechanisms are involved in early and late phases of immunity. Total serum IgE, as well as in vitro IgE production by mesenteric lymph node (MLN) cells, was increased 2 weeks p.i., the levels being markedly higher in BN than in F-344 rats. Serum rat mast cell protease II was also increased more significantly in BN than in F-344 rats. In contrast, production of IgG2a and IFN-gamma by MLN and spleen cells was found to be higher in F-344 than in BN rats. These results indicate that the early worm expulsion is correlated with the host IgE and mast cell responsiveness, whereas the persistence of infection in the late period may be controlled by different immune mechanisms.

COS cell expression cloning of Pfg377, a Plasmodium falciparum gametocyte antigen associated with osmiophilic bodies

We report the deduced protein sequence and preliminary characterization of Pfg377, a novel sexual stage antigen of Plasmodium falciparum. An initial cDNA clone (Pfg377-1) encoding the N-terminal 755 amino acids of Pfg377 was isolated by transfecting a 3D7 gametocyte cDNA library into COS7 cells and selecting using a pool of anti-Pfs230 monoclonal antibodies. The protein encoded by Pfg377-1 included an N-terminal hydrophobic signal sequence, but no apparent transmembrane anchor. Instead, the particular cDNA clone selected was fused in-frame at its 3' end with the coding sequence for the human decay acceleration factor membrane anchor, which had been deliberately placed downstream of the vector polylinker in order to attach potential fusion proteins onto the COS cell surface. Northern blots probed with the Pfg377-1 cDNA demonstrated cross-hybridization to a single approximately 9.5-kb transcript, which was present only in sexual stages, and not in a sexual stages. DNA hybridization was used to obtain a series of overlapping genomic clones which collectively yielded the complete DNA sequence for Pfg377. There are no introns within the gene, which contains a 9360-bp open reading frame and encodes a 377-kDa protein. The Pfg377 protein is highly hydrophilic, and has an essentially non-repetitive structure, with only four very limited regions of tandem repeats. The Pfg377 gene resides on chromosome 12, and immunoelectron microscopy with two different anti-Pfg377 polyclonal antisera raised against two separate recombinant sub-fragments of the protein both indicated that the antigen is located in electron-dense organelles of the gametocytes--the osmiophilic bodies--which are proposed to play a role in parasite emergence from the erythrocyte during gametocyte maturation in the Anopheles mosquito midgut. Although it was selected with anti-Pfs230 antibodies, comparison of the sub-cellular locations and protein sequences of Pfg377 and Pfs2 show them to be completely distinct antigens. We hypothesize that Pfg377-1 was initially isolated because it expresses an epitope which is recognized by (i.e., cross-reacts with) one of the anti-Pfs230 monoclonal antibodies used to select the original transfected COS cells.

Mucosal mast cell proliferation following normal and heterotopic infections of the nematode Nippostrongylus brasiliensis in rats

Infections of intestinal nematodes induce the T cell-dependent proliferation of intestinal mucosal mast cells (MMC). To examine whether nematode-induced MMC proliferation is affected by the site of infestation, adult-stage nematode Nippostrongylus brasiliensis (NB) was transplanted into the normal infection site, the duodenum, or into heterotopic sites, the peritoneal cavity (i.p.) or subcutaneous tissue (s.c.), of rats. Two weeks after duodenal inoculation, MMC numbers in the small intestine had increased 6.5-fold. In contrast, i.p. and s.c. inoculation induced only slight increases of intestinal MMC. After i.p. inoculation, worm granulomas developed in the connective tissues adhering to stomach and duodenum, and large numbers of mast cells appeared around the granulomas. The majority of the latter mast cells showed histochemical features similar to MMC: they were formalin sensitive, berberine sulfate-, alcian blue+/safranine-, and rat mast cell protease (RMCP) II+. After s.c. inoculation, worm granulomas developed at the inoculation site, but the number of mast cells around the granulomas was not significantly increased. These results suggest that intense proliferation of MMC or MMC-like cells is induced only by the infections on mucosa or in mucosa-associated tissues.

Plasmodium coatneyi-infected rhesus monkeys: a primate model for human cerebral malaria

Although several animal models for human cerebral malaria have been proposed in the past, none have shown pathological findings that are similar to those seen in humans. In order to develop an animal model for human cerebral malaria, we studied the pathology of brains of Plasmodium coatneyi (primate malaria parasite)-infected rhesus monkeys. Our study demonstrated parasitized erythrocyte (PRBC) sequestration and cytoadherence of knobs on PRBC to endothelial cells in cerebral microvessels of these monkeys. This is similar to the findings seen in human cerebral malaria. Cerebral microvessels with sequestered PRBC were shown by immunohistochemistry to possess CD36, TSP and ICAM-1. These proteins were not evident in cerebral microvessels of uninfected control monkeys. Our study indicates, for the first time, that rhesus monkeys infected with P. coatneyi can be used as a primate model to study human cerebral malaria.

A nonhuman primate model for human cerebral malaria: effects of artesunate (qinghaosu derivative) on rhesus monkeys experimentally infected with Plasmodium coatneyi

We studied the effects of artesunate on rhesus monkeys infected with Plasmodium coatneyi. Sixteen rhesus monkeys were divided in four groups. Group I consisted of three monkeys that were splenectomized and were treated with three doses (loading dose: 3.3 mg/kg, maintenance doses: 1.7 mg/kg) of artesunate, group II consisted of three monkeys that were treated with three doses of artesunate (same as group I), group III consisted of two monkeys that were treated with one dose (3.3 mg/kg) of artesunate, and group IV consisted of five untreated monkeys. Parasitemias of these groups ranged from 13.3% to 19.5% before treatment. Twenty-four hours after administration, the parasitemia was reduced to 2.2% in group I and to < 0.1% in group II; parasitemia was lowered to 10.6% in group III only 3 hr after drug administration. The rate of sequestration in the cerebral microvessels, which was 29.4% in untreated animals, was < 0.1% in groups I and II (24 hr after treatment), and 2.0% in group III (3 hr after treatment). These data clearly indicate that artesunate not only reduced parasitemia, but also reduced the rate of parasitized red blood cell (PRBC) sequestration in cerebral microvessels. In an immunohistologic study, endothelial-leukocyte adhesion molecule-1 (ELAM-1) was not detected in group I after treatment with artesunate, although the presence of CD36, thrombospondin, intercellular adhesion molecule-1, IgG, and C3 in the cerebral microvessels was not altered. This is the first in vivo study to show that artesunate interferes with continued PRBC sequestration in the cerebral microvessels in cerebral malaria.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoglobulin complex deposits in Plasmodium falciparum-infected placentas from Malawi and Papua New Guinea

Term placentas from 35 patients infected with Plasmodium falciparum were obtained in Malawi in southeast Africa and six term placentas from patients infected with P. falciparum were obtained in Wewak, Papua New Guinea, Melanesia. The placental tissues were examined by light microscopy and by an immunohistologic method to compare the pathologic changes of placentas in the two malaria-endemic countries. Using the number of parasitized red blood cells (PRBC) in intervillous spaces, pregnant women from Malawi with placental parasitemia were categorized into three groups. In the high PRBC group (> 20%, group I), there was no deposition of IgE in fetal blood vessels. In contrast, IgE was observed in fetal blood vessels of the intermediate PRBC group (1-10%, group II) and low PRBC group (< 1%, group III). In all six placentas from Papua New Guinean women, deposition of immune complexes, including IgE, was observed in the fetal blood vessels. All placentas with deposition of IgE in fetal blood vessels showed no sequestration of malaria parasites in intervillous spaces. Our data indicate that the amount of deposition of IgE in the placenta from women infected with P. falciparum is inversely correlated with the degree of parasitemia at that site.

Experimental Plasmodium falciparum cerebral malaria in the squirrel monkey Saimiri sciureus

Infection of the squirrel monkey, Saimiri sciureus, with several strains of Plasmodium falciparum leads in a proportion of animals to neurological symptoms with a fatal outcome. This first simian model for human cerebral malaria was studied with three strains of parasites, the uncloned Palo Alto(FUP-1) strain, the Palo AltoPLF3 clone MHB11, and the recently monkey-adapted P. falciparum strain IPC/RAY. Cerebral malaria could develop during primo infection of monkeys, whether the animals had been splenectomized or not. It did not occur in all animals and the appearance of neurological symptoms could not be predicted, as it was not related to the degree of parasitemia or duration of parasite infections.

Placental pathology in Plasmodium berghei-infected rats

The pathologic changes in placentae of pregnant rats infected with Plasmodium berghei at different stages of gestation were studied using light and electron microscopy and immunohistochemistry. The major changes observed were thickening and duplication of the trophoblastic basement membrane, and accumulation of parasitized erythrocytes and occasional mononuclear cells in the maternal blood space. Immunohistochemical examination of nine placentae revealed that six stained positively for IgG, two for IgM, and four for P. berghei antigen. No C3 deposition was detected. The findings in this study indicate that the variable parasitologic-clinical course from benign to fatal of P. berghei infection in pregnant rats makes it a potentially valuable model of human gestational malaria infection.

Epitope-selected monospecific antibodies to recombinant antigens from Toxoplasma gondii reacted with dense granules of tachyzoites

Epitope-selected monospecific antibodies were applied to investigate the localization of antigenic molecules in Toxoplasma gondii by immunoelectron microscopy. Eighty cDNA clones encoding antigenic polypeptides were immunoscreened from lambda gt11 expression library with T. gondii infected mouse sera. Twenty different clones with no crossreactivity were selected from eighty clones. Monospecific antibodies to antigens derived from respective cDNA clones extracted from infected mouse sera by the epitope selection method were used in Western blot analysis and immunoelectron microscopy. Eleven antigens were detected with epitope-selected antibodies in lysates of T. gondii tachyzoites. Five of the antigens with molecular weights of 60, 40, 35, 28, and 27 KD were localized in the dense granules. Monospecific antibodies purified by the epitope selection method were useful for investigating the localization of antigens without preparation of a monoclonal antibody from a hybridoma.

Renal pathology in owl monkeys vaccinated with Plasmodium falciparum asexual blood-stage synthetic peptide antigens

Renal specimens from Aotus monkeys were studied by light microscopy and immunohistochemistry to examine pathologic changes following vaccination with synthetic peptides corresponding to the 35-kD, 55-kD, and 83-kD asexual blood stage antigens of Plasmodium falciparum. The monkeys were vaccinated and later challenged with P. falciparum. In the monkeys vaccinated with Centers for Disease Control peptides (group I), specimens from four of six postvaccinated animals had mild to severe mesangial proliferation and two had diffuse interstitial nephritis. Specimens from three monkeys vaccinated with Colombia peptides (group II) had mild to severe mesangial proliferation and one had interstitial nephritis. In the hybrid polymer-vaccinated monkeys (group III), specimens from three animals had mild to moderate mesangial proliferation and one had severe interstitial nephritis. On the other hand, the control group immunized with bovine serum albumin (group IV) showed that specimens from three animals had mild to severe mesangial proliferation and two had severe interstitial nephritis. In the nonimmunized group (group V), specimens from three animals had moderate to severe mesangial proliferation and two had severe and mild interstitial nephritis. Immunohistochemical analysis using the peroxidase-antiperoxidase method revealed mesangial deposits of P. falciparum antigens in 11 of 14 vaccinated monkeys and in five of 10 unvaccinated controls. These results show that treatment of monkeys with prospective malaria vaccines does not increase the frequency of occurrence or of the severity of renal lesions. These data thus provide a baseline for assessing the safety of synthetic malarial vaccines in the future.

Human vascular endothelial cell adhesion receptors for Plasmodium falciparum-infected erythrocytes: roles for endothelial leukocyte adhesion molecule 1 and vascular cell adhesion molecule 1

The clinical complications associated with severe and cerebral malaria occur as a result of the intravascular mechanical obstruction of erythrocytes infected with the asexual stages of the parasite, Plasmodium falciparum. We now report that a primary P. falciparum-infected erythrocyte (parasitized red blood cell [PRBC]) isolate from a patient with severe complicated malaria binds to cytokine-induced human vascular endothelial cells, and that this adhesion is in part mediated by endothelial leukocyte adhesion molecule 1 (ELAM-1) and vascular cell adhesion molecule 1 (VCAM-1). PRBC binding to tumor necrosis factor alpha (TNF-alpha)-activated human vascular endothelial cells is partially inhibited by antibodies to ELAM-1 and ICAM-1 and the inhibitory effects of these antibodies is additive. PRBCs selected in vitro by sequential panning on purified adhesion molecules bind concurrently to recombinant soluble ELAM-1 and VCAM-1, and to two previously identified endothelial cell receptors for PRBCs, ICAM-1, and CD36. Post-mortem brain tissue from patients who died from cerebral malaria expressed multiple cell adhesion molecules including ELAM-1 and VCAM-1 on cerebral microvascular endothelium not expressed in brains of individuals who died from other causes. These results ascribe novel pathological functions for both ELAM-1 and VCAM-1 and may help delineate alternative adhesion pathways PRBCs use to modify malaria pathology.

Pathology of falciparum malaria in Vietnam

Autopsy samples from the brains of 20 patients who died of falciparum malaria were examined by light microscopy and by an immunohistologic method. Particular attention was paid to a comparison of the pathologic features of the white matter and the cortex. In the high-sequestration (greater than 50%) group (n = 8), the mean +/- SD percentage of cerebral microvessels that showed parasitized red blood cell (PRBC) sequestration was 71.2 +/- 8.1% in the cortex and 84.0 +/- 6.7% in the white matter. The difference in the PRBC sequestration rate between cortex and white matter was statistically significant (P less than 0.01). Perivascular and ring hemorrhages were seen more frequently in the white matter than in the cortex. Deposition of IgG and Plasmodium falciparum antigen in the cerebral microvessels was more highly significant in the white matter than in the cortex (P less than 0.01). Our study demonstrated that the localized concentration of PRBC sequestration in the brain correlated with the marked immunohistologic differences in the microvessels of cortex and white matter.

A primate model for human cerebral malaria: Plasmodium coatneyi-infected rhesus monkeys

A major factor in the pathogenesis of human cerebral malaria is blockage of cerebral microvessels by the sequestration of parasitized human red blood cells (PRBC). In vitro studies indicate that sequestration of PRBC in the microvessels is mediated by the attachment of knobs on PRBC to receptors on the endothelial cell surface such as CD36, thrombospondin (TSP), and intercellular adhesion molecule-1 (ICAM-1). However, it is difficult to test this theory in vivo because fresh human brain tissues from cerebral malarial autopsy cases are not easy to obtain. Although several animal models for human cerebral malaria have been proposed, none have shown pathologic findings that are similar to those seen in humans. In order to develop an animal model for human cerebral malaria, we studied brains of rhesus monkeys infected with the primate malaria parasite, Plasmodium coatneyi. Our study demonstrated PRBC sequestration and cytoadherence of knobs on PRBC to endothelial cells in the cerebral microvessels of these monkeys. Cerebral microvessels with sequestered PRBC were shown by immunohistochemical analysis to possess CD36, TSP, and ICAM-1. These proteins were not evident in the cerebral microvessels of uninfected control monkeys. Thus, our study indicates, for the first time, that rhesus monkeys infected with P. coatneyi can be used as a primate model to study human cerebral malaria. By using this animal model, we may be able to evaluate strategies for the development of vaccines to prevent human cerebral malaria.

A study on the pathogenesis of human cerebral malaria and cerebral babesiosis

Cerebral complications are important, but poorly understood pathological features of infections caused by some species of Plasmodium and Babesia. Patients dying from P. falciparum were classified as cerebral or non-cerebral cases according to the cerebral malaria coma scale. Light microscopy revealed that cerebral microvessels of cerebral malaria patients were filled with a mixture of parasitized and unparasitized erythrocytes, with 94% of the vessels showing parasitized red blood cell (PRBC) sequestration. Some degree of PRBC sequestration was also found in non-cerebral malaria patients, but the percentage of microvessels with sequestered PRBC was only 13%. Electron microscopy demonstrated knobs on the membrane of PRBC that formed focal junctions with the capillary endothelium. A number of host cell molecules such as CD36, thrombospondin (TSP) and intercellular adhesion molecule I (ICAM-1) may function as endothelial cell surface receptors for P. falciparum-infected erythrocytes. Affinity labeling of CD36 and TSP to the PRBC surface showed these molecules specifically bind to the knobs. Babesia bovis infected erythrocytes produce projections of the erythrocyte membrane that are similar to knobs. When brain tissue from B. bovis-infected cattle was examined, cerebral capillaries were packed with PRBC. Infected erythrocytes formed focal attachments with cerebral endothelial cells at the site of these knob-like projections. These findings indicate that cerebral pathology caused by B. bovis is similar to human cerebral malaria. A search for cytoadherence proteins in the endothelial cells of cattle may lead to a better understanding of the pathogenesis of cerebral babesiosis.

Renal pathology in Saimiri monkeys during a vaccine trial using the recombinant circumsporozoite protein of Plasmodium vivax

Renal specimens of squirrel monkeys (Saimiri sciureus boliviensis) were studied by light microscopy and immunohistochemistry to examine the pathologic changes during vaccine trials with four recombinant circumsporozoite (CS) proteins (rPvCS-1, rPvCS-2, rPvCS-3, NS1(81) V20) of Plasmodium vivax. The monkeys were vaccinated and later challenged with P. vivax sporozoites. Among the 33 posttrial biopsies, 17 had mild to moderate mesangial proliferation and nine had interstitial nephritis. Immunohistochemistry by the peroxidase-antiperoxidase (PAP) method revealed IgG deposits in only three of 24 specimens and failed to demonstrate C3 deposits and P. vivax antigens in their glomeruli. There was no relationship between the severity of nephropathy and intensity of parasitemia. The intensity of parasitemia was the same in the vaccinated and control groups. Vaccinated monkeys from the groups (rPvCS-1, rPvCs-2, rPvCS-3) had no differences in renal pathology from the unvaccinated controls, but one group vaccinated with NS1(81) V20 did not develop renal changes.

Human cerebral malaria in Thailand: a clinico-pathological correlation

Based on the cerebral malaria coma scale, 39 falciparum malaria autopsy cases from the Hospital for Tropical Diseases, Mahidol University, Bangkok, Thailand were divided into two groups of patients that had either cerebral malaria or non-cerebral malaria. We then studied significant pathological differences, such as parasitized erythrocyte (PRBC) sequestration, ring hemorrhages and cerebral edema, between these two groups in order to investigate the correlation between the clinical coma scale and pathological findings. Patients with a coma grade of 2 and higher were designated as having cerebral malaria, and had erythrocyte PRBC sequestration in cerebral microvessels. Ninety four percent (94%) of cerebral microvessels showed PRBC sequestration when quantitatively analyzed. On the other hand, only 13% of cerebral microvessels showed sequestration in non-cerebral malaria patients with a coma grade of 1 and lower, although some degree of PRBC sequestration was found in 50% of these patients. Our study, therefore, clearly demonstrated that the degree of the PRBC sequestration in cerebral microvessels appeared to correlate closely with the clinical coma scale.

Bromodeoxyuridine labeling studies on the proliferation of intestinal mucosal mast cells in normal and athymic rats

The proliferation of mucosal-type mast cells (MMC) in rat small intestine was studied using a bromodeoxyuridine (BrdU)-labeling method. After 24-h cumulative injections of BrdU into adult SD rats, 3.5% of MMC were labeled, while only 0.3% and 0.1% of mast cells were labeled in back skin and ear respectively. From the results, it was concluded that MMC division occurred more than 10 times as frequently as the division of skin mast cells. Similar results were obtained in athymic adult rats (F344/N Jcl-rnu) in which the number of MMC was similar to that in heterologous animals. Thus, thymic factor(s) or T cells may not have an important role in MMC division in normal states. When SD rats were infected with Nippostrongylus brasiliensis, vigorous proliferation of MMC was brought about 13 to 15 days after infection. At that period, 40% of MMC were labeled by a single injection of BrdU, and 85% of MMC were labeled by 9-h cumulative injections of BrdU, with the result that most MMC rapidly proliferated in the intestinal mucosa during this period. Mitotic figures of MMC were sometimes observed. On the contrary, hyperplasia of MMC was not observed in athymic rats infected with nematodes. Therefore, MMC hyperplasia after nematode infection is dependent on thymic factor or T cells, and its mechanism is different from that of MMC division in normal states, in which thymic factor(s) or T cells are not essential.

Disseminated infection of Pneumocystis carinii in a patient with the acquired immunodeficiency syndrome

This report describes the histopathology of a disseminated Pneumocystis carinii infection in a 24-year-old Japanese male haemophiliac diagnosed as having the acquired immunodeficiency syndrome. He developed respiratory symptoms, and Pneumocystis carinii pneumonia was confirmed by transbronchial lung biopsy. On the 70th day of hospitalization the patient died. Autopsy findings revealed Pneumocystis carinii not only in the lungs but also in the stomach, jejunum, ileum, colon, mesoappendix, abdominal lymph nodes, diaphragm, and thyroid gland.

Yeast glucan in the cyst wall of Pneumocystis carinii

Ultrastructurally, the cyst wall of Pneumocystis carinii consists of an electron-dense outer layer, an electron-lucent middle layer, and an innermost plasmalemma. This is similar in appearance to the cell wall of some yeasts, e.g. Saccharomyces cerevisiae, which consists of an outer dense layer of mannan, a middle lucent layer of beta-1,3-glucan (yeast glucan) and an innermost plasmalemma. The cyst wall of P. carinii, as well as the cell wall of S. cerevisiae, can be labeled by a variety of methods which stain polysaccharides, such as Gomori's methenamine silver (GMS) and by Aniline blue, a dye which selectively stains beta-1,3-glucan. The treatment of P. carinii cysts with Zymolyase, which the key enzyme is beta-1,3-glucan laminaripentaohydrolase, results in lysis of the outer 2 layers of the cyst wall and the loss of positive staining by both GMS and Aniline blue. The lysis of elements of the cyst wall of P. carinii is achieved under the same conditions and concentration at which Zymolyase lyses the outer 2 layers of the cell wall of viable cells of S. cerevisiae. These observations indicate that a major component of the cyst wall of P. carinii is beta-1,3-glucan.

Long-term in vitro suspension culture of Toxoplasma and HeLa cells

To establish a method of mass and long-term propagation of Toxoplasma in suspension cultures and to find a technique for separating the organisms from host cells, basic investigations were carried out in a microcomputer controlled system. By using an arbitrary unit "the medium index" host HeLa cells were continuously supplied to Toxoplasma organisms for about 30 days, at cycles of 4 days. HeLa cells were well infected with Toxoplasma in the suspension cultures by leaving the medium unstirred for 15 min intervals. The separation of Toxoplasma organisms from cells was improved by treating toxoplasmas and HeLa cells mixtures with 0.4% trypsin. The total number of separated organisms obtained from 29 days cultivation period was 4.9 X 10(9). The mean generation time of Toxoplasma organisms on the 0, 10, 20 and 30 day's cultivation was calculated approximately 7.4, 9.4, 9.3 and 7.8 h, respectively.

Detection of surface carbohydrates on Pneumocystis carinii by fluorescein-conjugated lectins

Lectins react with a wide range of different carbohydrates (Table 1). Even so-called monospecific anti-H(O) lectins from Lotus tetragonolobus, Ulex europaeus, and Anguilla anguilla react not only with the anti-H determinant but also with several fucosylated carbohydrates. Consequently, the type of lectin receptor existing on the surface of Pneumocystis carinii should be determined, because only a carbohydrate analysis can demonstrate the kind of carbohydrates which exist on the cell surface of this parasite. For the purpose of this study we used fluorescent isothiocyanata (FITC)-conjugated lectins. Concanavalin A (Con A) and Maclura pomifera (MPA) agglutinin reacted to P. carinii at low concentrations, and the fluorescence intensity was gradually increased with the concentration of the lectins. With lectins from Bauhinia purpurea (BPA), Dolichos biflorus (DBA), Glycine max (SBA), Griffonia simplicifolia (GS-I, GS-II), and Triticum vulgaris (WGA), fluorescence was emitted at high concentrations, while Arachis hypogaea (PNA) and Ulex europaeus (UEA-I) agglutinins did not show fluorescence. The results suggest that P. carinii has abundant Con A- and MPA-specific carbohydrates on the surface.

Light microscopical study of Blastocystis spp. in monkeys and fowls

An investigation of a Blastocystis species obtained from several species of monkeys and fowls was conducted to clarify the morphology of the organism, using light microscopical techniques including Giemsa, Heidenhain iron hematoxylin, Trichrome stains, iodine mount and phase-contrast microscopy. A comparison was made with Blastocystis hominis from humans. Blastocystis spp. were found in 15 out of 26 monkeys and in all of 12 fowls (10 chickens and 2 ostriches) examined. The behaviour of the parasites in the bowels was also examined, using paraffin-embedded sections. Microscope examination of the lumen contents at death revealed the organism in the caecum of monkeys and fowls. The organisms from faeces, cultures and the lumen contents of the caecum of humans, monkeys and fowls were similar, except for variations in the size and contents of the central vacuoles, which occupied the centre of the organisms.

Pneumocystis infection in macaque monkeys: Macaca fuscata fuscata and Macaca fascicularis

Retrospective examination of lungs from 128 monkey necropsies was attempted for Pneumocystis infection using special strains, including toluidine blue-O and Gomori's methenamine silver nitrate. Four Japanese monkeys (7.7%), Macaca fuscata fuscata, and one crab-eating monkey (7.7%), Macaca fascicularis, were found to have Pneumocystis infection. The organism was found in young and infant animals. At the time of death, one infant and two young monkeys were debilitated and/or emaciated. Pneumocystis infection was considered an important lesion which could have caused reduced respiratory function in two of the Japanese monkeys, but constituted only an incidental finding in the others.