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Biomedical subjects

J D Schwartzman

Publications and source records attributed to J D Schwartzman.

At least 19 recordsLinked to original sources
PubMed2001

Mice lacking the chemokine receptor CCR1 show increased susceptibility to Toxoplasma gondii infection.

Chemokines are critical for the recruitment of effector immune cells to sites of infection. Mice lacking the chemokine receptor CCR1 have defects in neutrophil trafficking and proliferation. In the present study, we tested the susceptibility of CCR1 knockout mice to infection with the obligate intracellular protozoan parasite Toxoplasma gondii. In comparison with parental wild-type mice, CCR1(-/-) mice exhibited dramatically increased mortality to T. gondii in association with an increased tissue parasite load. No differences were observed in Ag-specific T cell proliferation or in cytokine responses between mutant and wild-type mice. However, the influx of PMNs to the peripheral blood and to the liver were reduced in CCR1(-/-) mice during early infection. Our results suggest that CCR1-dependent migration of neutrophils to the blood and tissues may have a significant impact in controlling parasite replication.

Animals↗
PubMed2001

Murine ileitis after intracellular parasite infection is controlled by TGF-beta-producing intraepithelial lymphocytes.

BACKGROUND & AIMS: Acute inflammatory ileitis occurs in susceptible (C57BL/6) mice after oral infection with Toxoplasma gondii. Overproduction of interferon (IFN)-gamma and synthesis of nitric oxide mediate the inflammation. We evaluated the role of transforming growth factor (TGF)-beta produced by intraepithelial lymphocytes (IELs) in this process. METHODS: We analyzed the histologic and immunologic consequences of adoptive transfer of antigen-primed IELs into susceptible mice treated with anti-TGF-beta before oral challenge with T. gondii cysts. An in vitro coculture of enterocytes and IELs assessed the production of chemokines and cytokines in the presence of anti-TGF-beta. RESULTS: Antigen-primed IELs prevent acute ileitis in susceptible mice that is reversed with anti-TGF-beta. Resistant mice (CBA/J) develop ileitis after treatment with anti-TGF-beta. Antigen-primed IELs can induce systemic immunosuppression as measured by depressed IFN-gamma production. In vitro, primed IELs reduce the production of inflammatory chemokines by infected enterocytes and IFN-gamma by splenocytes. CONCLUSIONS: Regulation of the ileal inflammatory process resulting from T. gondii is dependent on TGF-beta-producing IELs. The IELs are an essential component in gut homeostasis after oral infection with this parasite.

Animals↗
PubMed2000

IP-10 is critical for effector T cell trafficking and host survival in Toxoplasma gondii infection.

The generation of an adaptive immune response against intracellular pathogens requires the recruitment of effector T cells to sites of infection. Here we show that the chemokine IP-10, a specific chemoattractant for activated T cells, controls this process in mice naturally infected with Toxoplasma gondii. Neutralization of IP-10 in infected mice inhibited the massive influx of T cells into tissues and impaired antigen-specific T cell effector functions. This resulted in >1000-fold increase in tissue parasite burden and a marked increase in mortality compared to control antibody-treated mice. These observations suggest that IP-10 may play a broader role in the localization and function of effector T cells at sites of Th1 inflammation.

Animals↗
PubMed2000

Perineal group A streptococcal disease in a pediatric practice.

OBJECTIVE: This study was designed to document the frequency and define the clinical, epidemiologic, and microbiologic characteristics of perineal disease caused by group A beta-hemolytic streptococci (GAS) in a pediatric practice in which increased numbers of cases had been observed. METHODS: Clinical, epidemiologic, and microbiologic data were collected on all culture-confirmed cases of perineal GAS disease during the calendar year 1997. GAS isolates from clinical cases and a comparison group of children with GAS pharyngitis were analyzed by T typing, emm gene analysis, and pulsed-field gel electrophoresis (PFGE). RESULTS: Twenty-three cases of GAS perineal disease were diagnosed during 4530 office visits in 1997. Thirteen cases had perianal disease, 8 had vulvovaginal infection, and 2 were infected at both sites. No cases of penile disease were identified. Infections peaked in late winter and early spring and affected children with an average age of 5 years with a range of perineal, gastrointestinal, and genitourinary symptoms. Analysis of T and emm types showed the majority (82%) of perineal isolates to be T 28 emm 28, showing 2 closely related PFGE patterns. In contrast, the pharyngeal isolates were distributed among 6 different T and emm types. CONCLUSION: Perineal infection caused by GAS may be a relatively common diagnosis in a pediatric or family practice setting. There may be specific GAS types that have a tropism for perineal tissues but the mechanism of infection is yet to be established.

Child↗
PubMed1999

CD8+ CTLs are essential for protective immunity against Encephalitozoon cuniculi infection.

Encephalitozoon cuniculi is a protozoan parasite that has been implicated recently as a cause of opportunistic infection in immunocompromised individuals. Protective immunity in the normal host is T cell-dependent. In the present study, the role of individual T cell subtypes in immunity against this parasite has been studied using gene knockout mice. Whereas CD4-/- animals resolved the infection, mice lacking CD8+ T cells or perforin gene succumbed to parasite challenge. The data obtained in these studies suggest that E. cuniculi infection induces a strong and early CD8+ T response that is important for host protection. The CD8+ T cell-mediated protection depends upon the CTL activity of this cell subset, as the host is rendered susceptible to infection in the absence of this function. This is the first report in which a strong dependence upon the cytolytic activity of host CD8+ T cells has been shown to be important in a parasite infection.

Animals↗
PubMed1999

Characterization of myosin-A and myosin-C: two class XIV unconventional myosins from Toxoplasma gondii.

Two class XIV unconventional myosins from Toxoplasma gondii, Myosin-A (TgM-A) and Myosin-C (TgM-C), were characterized in terms of their biochemical properties and their expression in quiescent and motile stages of the parasite life cycle. In cell fractionation studies, both myosins partitioned with the major organelle/cell membrane fraction, and extraction studies indicated that both were tightly associated with membrane domains as detergent was necessary for their solubilization. In addition, both TgM-A and TgM-C demonstrated a hallmark feature of myosins in their ability to bind actin in the absence but not the presence of ATP. In parasites residing within the host cell parasitophorous vacuole, TgM-A was detected by immunofluorescence microscopy as a bright spot near the apical pole of the parasite. This pattern underwent a subtle change as the parasites became motile, with TgM-A then localizing more intimately with the parasite cell membrane domain in apically disposed spots or patches, consistent with the role of this myosin in gliding motility. TgM-C showed a distinct localization to the juxtanuclear region towards the apical pole of the parasite, consistent with an association with the Golgi apparatus.

Actins↗
PubMed1999

Functional and quantitative analysis of splenic T cell immune responses following oral toxoplasma gondii infection in mice.

Functional and quantitative analysis of splenic T cell immune responses following oral Toxoplasma gondii infection in mice. Experimental Parasitology 91, 212-221. Immunity to Toxoplasma gondii is mediated primarily by the host T cell response. Although there is considerable information regarding host immunity following intraperitoneal infection with tachyzoites, little information is available regarding naturally acquired infection following peroral infection with bradyzoites. In this study, a sequential quantitative analysis of the cell-mediated immune response was performed at the single cell level. To assess the kinetics of this response and parasitic loads, inbred mice were orally infected with the 76K strain bradyzoites of T. gondii. Within 24 h of infection, follicular hyperplasia followed by infiltration with histiocytes, macrophages, and apoptotic bodies was observed in the spleens of infected mice. T. gondii were detected from day 1, and counts increased gradually during the experimental period. Splenocyte DNA synthesis to antigen and mitogen was severely suppressed at days 7 and 10. The percentages of NK1.1(+) or delta gamma T cells were increased from day 1, whereas CD4(+) and CD8alpha+ T cells were signficantly increased after day 7 postinfection. CD25 expression and intracellular IFN-gamma production increased in NK1.1(+) cells on day 1 and by all other T cell subsets after day 4. Intracellular IL-4 did not increase until day 7, and IL-10 production was increased in all T cell subsets after day 4. Together, these findings indicate that oral infection with T. gondii stimulates a strong cellular immune response that appears to polarize toward an early Th1 response. However, within 7 days, a strong immune Th2 regulatory response as well as high parasitic loads can be observed, with a reduction in lymphoproliferation to mitogen stimulation, increased production of IL-4 and IL-10, and evidence of T cell apoptosis in the splenic immune compartment.

Animals↗
PubMed1999

Experimental ocular toxoplasmosis induced in naive and preinfected mice by intracameral inoculation.

We have developed a murine model to investigate the pathogenesis of acquired ocular toxoplasmosis. Tachyzoites of PLK strain of Toxoplasma gondii were intracamerally inoculated under anesthesia into the right eyes of naive or perorally preinfected C57BL/6 and MRL-MpJ mice. Clinical and histopathological observations of responses to intraocular infection were analyzed. Ocular inflammation from Toxoplasma gondii is dose-dependent in both strains of mice. After inoculation of fifty parasites, no evidence of inflammation was observed in the eyes of naive mice. The eyes of naive mice that received 500 or 5,000 parasites developed inflammatory changes by day 6 post challenge. By day 8, the changes progressed to moderate to severe intraocular inflammation. Histologic analysis of the ocular lesions demonstrated mononuclear cell infiltration and necrosis predominantly in the anterior segment of the eyes of the naive mice. Inoculation of 50,000 tachyzoites induced a destructive ocular inflammatory response and was uniformly lethal to the mice by approximately one week after challenge. In contrast, eyes from mice previously orally infected with Toxoplasma gondii and that received a 50 or 500 parasite intracameral challenge revealed no inflammation, but the eyes receiving 5,000 parasites demonstrated necrotic focal retinochoroiditis with vitreitis by day 8 after challenge. The murine model reproduces some features of ocular toxoplasmosis in humans and may be suitable for large-scale controlled studies of the pathogenesis and therapeutics of acquired ocular toxoplasmosis as well as for study of the mechanisms of immune privilege in the eye.

Animals↗
PubMed1999

Immune CD8(+) T cells prevent reactivation of Toxoplasma gondii infection in the immunocompromised host.

Toxoplasma gondii remains a serious cause of morbidity and mortality in individuals that are immunosuppressed, patients with AIDS in particular. The cellular immune response, especially by gamma interferon (IFN-gamma)-producing CD8(+) T cells, is an essential component of protective immunity against the parasite. In the present study the role of CD8(+) T cells during the reactivation of Toxoplasma infection in an immunocompromised murine model was evaluated. Chronically infected mice were challenged with LP-BM5 virus, and the kinetics of CD8(+) T-cell function was studied. At 10 weeks after viral infection, mice showed obvious signs of systemic illness and began to die. At this stage, CD8(+) T cells were unresponsive to antigenic stimulation and unable to kill Toxoplasma-infected targets. IFN-gamma production by the CD8(+) T cells from dual-infected animals reached background levels, and a dramatic fall in the frequency of precursor cytotoxic T lymphocytes was observed. Histopathological analysis of the tissues demonstrated signs of disseminated toxoplasmosis as a result of reactivation of infection. However, treatment of the dual-infected animals with immune CD8(+) T cells at 5 weeks post-LP-BM5 challenge prevented the reactivation of toxoplasmosis, and mice continued to live. Our study for the first time demonstrates a therapeutic role for CD8(+) T cells against an opportunistic infection in an immunocompromised state.

Animals↗
PubMed1999

Fas-FasL interaction involved in pathogenesis of ocular toxoplasmosis in mice.

Ocular toxoplasmosis is a potentially blinding intraocular inflammation. The intent of this study was to investigate the role of Fas-FasL interaction in a murine model of acquired ocular toxoplasmosis induced by intracameral inoculation of Toxoplasma gondii. Intraocular inflammation, Fas and FasL expression on lymphocytes and on ocular tissues, the occurrence of apoptosis, and the frequency of CD8(+) and CD4(+) T cells in the infected eyes were analyzed in C57BL/6 (B6) mice. Susceptibility to parasite-induced intraocular inflammation was observed in Fas-deficient (B6-lpr) and FasL-deficient (B6-gld) mice. Inoculation of 5,000 T. gondii tachyzoites induced significant intraocular inflammation associated with increase of Fas and FasL expression in the inoculated eyes of wild-type B6 mice. Flow cytometry demonstrated a significant increase of Fas and FasL expression on the splenocytes from naive mice incubated in vitro with the parasite and on the splenocytes harvested from the infected mice at day 8 after parasite inoculation. Apoptosis of inflammatory cells and cells in ocular tissues was seen, and a greater frequency of CD8(+) than CD4(+) T cells was observed in the infected eyes. The intensity of intraocular inflammation was greater in B6-lpr and B6-gld mice than in wild-type B6 mice (P < 0.05). The results suggest that Fas-FasL interaction associated with apoptosis is involved in the pathogenesis of acquired ocular toxoplasmosis in mice.

Animals↗
PubMed1997

A dichotomous role for nitric oxide during acute Toxoplasma gondii infection in mice.

Production of nitric oxide by macrophages is believed to be an important microbicidal mechanism for a variety of intracellular pathogens, including Toxoplasma gondii. Mice with a targeted disruption of the inducible nitric oxide synthase gene (iNOS) were infected orally with T. gondii tissue cysts. Time to death was prolonged compared with parental controls. Histologic analysis of tissue from infected mice showed scattered small foci of inflammation with parasites in various tissues of iNOS-/- mice, whereas tissue from the parental C57BL/6 mice had more extensive tissue inflammation with few visible parasites. In particular, extensive ulceration and necrosis of distal small intestine and fatty degeneration of the liver was seen in the parental mice at day 7 postinfection, as compared with the iNOS-/- mice where these tissues appeared normal. Serum interferon gamma and tumor necrosis factor alpha levels postinfection were equally elevated in both mouse strains. Treatment of the parental mice with a NO synthase inhibitor, aminoguanidine, prevented early death in these mice as well as the hepatic degeneration and small bowel necrosis seen in acutely infected control parentals. These findings indicate that NO production during acute infection with T. gondii can kill intracellular parasites but can be detrimental, even lethal, to the host.

Animals↗
PubMed1997

A novel class of unconventional myosins from Toxoplasma gondii.

Here, we describe the complete deduced amino acid sequence of three unconventional myosins identified in the protozoan parasite Toxoplasma gondii. Phylogenetic analysis reveals that the three myosins represent a novel, highly-divergent class addition to the myosin superfamily. Toxoplasma gondii myosin-A (TgM-A) is a remarkably small approximately 93 kDa myosin that shows a striking departure from typical myosin heavy chain structure in having a head and tail domain but no discernible neck domain. In other myosins, the neck is defined by one or more IQ motifs that serve as potential light chain binding domains. No IQ motifs are apparent in TgM-A. The tail domain of TgM-A encompasses only 57 amino acid residues and is characterized by its highly basic charge (pI = 10.8). The other two Toxoplasma myosins, TgM-B and TgM-C appear to be the product of differential RNA splicing with TgM-B yielding a protein of approximately 114 kDa and TgM-C a protein of approximately 125 kDa. These two myosins are identical throughout their head domain and neck domain which contains a single IQ motif. TgM-B and C share the proximal 245 residues of their tail domain and then diverge in their tail structure distally. The tails, like that of TgM-A, share no homology to any other myosin tails apart from a highly basic charge. The identification of yet another class of unconventional myosins, including a myosin as novel in structure as the 93 kDa TgM-A, continues to underscore the diversity of this family of molecular motors.

Amino Acid Sequence↗
PubMed1997

Neospora caninum: role for immune cytokines in host immunity.

Neospora caninum is a coccidial protozoan parasite that infects a large range of mammals including dogs, cats, mice, and cattle. Morphologically, N. caninum appears indistinguishable from Toxoplasma gondii, although they are genetically distinct. To date there have been no reported cases of this infection in humans, although nonhuman primates may be susceptible to infection. Inbred A/J mice develop no clinical and little histologic evidence of infection in spite of a high-dose inoculum of N. caninum. Splenocytes obtained from infected mice proliferate in vitro in response to both N. caninum and T. gondii-soluble antigen. A transient state of T cell hyporesponsiveness to parasite antigen and mitogen was observed at Day 7 p.i. This downregulatory response could be partially reversed by the addition of the nitric oxide antagonist LNMMA, but not antibody to IL-10. Mice infected with N. caninum produce significant quantities of IL-12 and IFN gamma, most evident shortly after infection. In vivo, antibody to IL-12 is able to neutralize immune resistance to the parasite. Moreover, in vivo depletion of IFN gamma with antibody renders the mice susceptible to infection. These observations suggest that N. caninum induces a T cell immune response in the infected host that is at least partially mediated by IL-12 and IFN gamma.

Animals↗
PubMed1997

Toxoplasma gondii: dithiol-induced Ca2+ flux causes egress of parasites from the parasitophorous vacuole.

Ca2+ is an essential activator of motility in the obligate intracellular parasite Toxoplasma gondii. Ca2+ ionophore A23187 and intracellular microinjection of Ca2+ initiate motility of parasites residing in parasitophorous vacuoles (PV). The source of Ca2+ and the mechanism by which it activates motility in vivo remain uncertain. Exposure of the parasites to dithiothreitol (DTT) can activate egress of previously nonmotile intravacuolar parasites within 60 sec. DTT is also known to activate both isoforms of the highly concentrated nucleoside triphosphate hydrolase (NTPase) produced by T. gondii. Using an adherent cell analysis system (ACAS) for Ca2+ imaging, a brief 15-50% increase in intra-PV fluorescence ratio was observed after exposure of infected fibroblasts to 5 mM DTT. Chelation of intracellular Ca2+ with BAPTA-AM and extracellular Ca2+ with EGTA blocked the DTT effect; however, this chelation did not prevent the activation of parasites nor the Ca2+ response to the Ca2+ ionophore ionomycin, suggesting that the Ca2+ that activates motility may reside near or within the parasite itself. This result demonstrates that an increase in Ca2+ within the vacuole precedes the onset of motility and the correlation of the DTT effect on motility and tachyzoite NTPase suggests that NTPase activation may be involved in the Ca2+ flux.

Animals↗
PubMed1997

A decision support system for microbiology quality control.

Manual review of antibiotic sensitivity testing results is an essential component of a microbiology laboratory's quality control process. Such review is tedious and prone to human error, however. An expert system is described that remembers which susceptibility patterns are considered typical or atypical by expert reviewers, then uses these to prescreen future isolates. It uses a similarity function to allow matching against this library when two patterns are close, but not identical. Use of this system allows more efficient and reliable review of the laboratory's antibiotic sensitivity testing results.

Decision Support Systems, Clinical↗
PubMed1996

Inhibition of Toxoplasma gondii replication by dinitroaniline herbicides.

Submicromolar concentrations of several dinitroaniline herbicides have been found to specifically inhibit intracellular replication of the protozoan parasite Toxoplasma gondii. IC50 concentrations for T. gondii survival were approximately 100 nM for ethalfluralin and oryzalin and approximately 300 nM for trifluralin. Primary human fibroblasts employed as host cells for parasite culture were unaffected at > 100-fold higher concentrations. Extracellular parasites were unaffected by these drugs, but within 8 hr after treatment of infected cell cultures, intracellular tachyzoites formed large amorphous bodies containing distorted nuclei. Parasite cytokinesis was completely blocked by drug treatment; nucleic acid synthesis, however, continued at near-normal levels for several days in the continuous presence of drug. All dinitroanilines appear to block nuclear division by inhibition of intranuclear spindle formation, but other cytoskeletal components were differentially affected by the various drugs tested. Subpellicular microtubules were absent in oryzalin-treated parasites, and large fragments of the inner membrane complex were observed throughout the parasite cytoplasm. In contrast, subpellicular microtubules and the inner membrane complex remained intact in ethalfluralin-treated parasites, but the endoplasmic reticulum and nuclear envelope were highly distended. Cytoskeletal elements associated with the conoid were not affected by any of the dinitroanilines tested, and treatment with the Ca2+ ionophore A23187 failed to trigger release of drug-treated parasites from infected cells. Mutant parasites resistant to oryzalin, ethalfluralin, or trifluralin were selected by chemical mutagenesis and examined for cross-resistance. An ethalfluralin-resistant mutant displayed cross-resistance to both oryzalin and trifluralin, while a trifluralin-resistant mutant was sensitive to oryzalin and only partially resistant ethalfluralin; an oryzalin-resistant mutant exhibited higher resistance to ethalfluralin and trifluralin than to oryzalin itself. Similarities between Apicomplexan and plant tubulin are discussed.

Animals↗