Detection of toxoplasmic encephalitis in HIV positive patients in urine with hydrogel nanoparticles.

BACKGROUND: Diagnosis of toxoplasmic encephalitis (TE) is challenging under the best clinical circumstances. The poor clinical sensitivity of quantitative polymerase chain reaction (qPCR) for Toxoplasma in blood and CSF and the limited availability of molecular diagnostics and imaging technology leaves clinicians in resource-limited settings with few options other than empiric treatment. METHOLOGY/PRINCIPLE FINDINGS: Here we describe proof of concept for a novel urine diagnostics for TE using Poly-N-Isopropylacrylamide nanoparticles dyed with Reactive Blue-221 to concentrate antigens, substantially increasing the limit of detection. After nanoparticle-concentration, a standard western blotting technique with a monoclonal antibody was used for antigen detection. Limit of detection was 7.8pg/ml and 31.3pg/ml of T. gondii antigens GRA1 and SAG1, respectively. To characterize this diagnostic approach, 164 hospitalized HIV-infected patients with neurological symptoms compatible with TE were tested for 1) T. gondii serology (121/147, positive samples/total samples tested), 2) qPCR in cerebrospinal fluid (11/41), 3) qPCR in blood (10/112), and 4) urinary GRA1 (30/164) and SAG1 (12/164). GRA1 appears to be superior to SAG1 for detection of TE antigens in urine. Fifty-one HIV-infected, T. gondii seropositive but asymptomatic persons all tested negative by nanoparticle western blot and blood qPCR, suggesting the test has good specificity for TE for both GRA1 and SAG1. In a subgroup of 44 patients, urine samples were assayed with mass spectrometry parallel-reaction-monitoring (PRM) for the presence of T. gondii antigens. PRM identified antigens in 8 samples, 6 of which were concordant with the urine diagnostic. CONCLUSION/SIGNIFICANCES: Our results demonstrate nanoparticle technology's potential for a noninvasive diagnostic test for TE. Moving forward, GRA1 is a promising target for antigen based diagnostics for TE.

Toxoplasmic Encephalitis Followed by Primary EBV-Associated Post-Transplant Lymphoproliferative Disorder of the Central Nervous System in a Patient Undergoing Allogeneic Hematopoietic Stem Cell Transplant: A Case Report.

Toxoplasmic encephalitis (TE) and post-transplant lymphoproliferative disorder of the central nervous system (CNS-PTLD) are major complications after allogeneic hematopoietic stem cell transplant (allo-SCT); both are fatal without timely diagnosis and disease-specific treatment. Differential diagnosis of TE and CNS-PTLD can be challenging because brain biopsy, a gold standard for diagnosis, is sometimes not possible, owing to poor patient condition after allo-SCT. Here, we describe a case of isolated CNS-PTLD arising during the therapeutic course of TE. A 51-year-old man was admitted with mental abnormalities and fever on Day 106 after allo-SCT to treat myelodysplastic syndrome. Magnetic resonance imaging (MRI) revealed multiple nodular and ring-enhanced lesions in the brain, and the result of polymerase chain reaction (PCR) for Toxoplasma gondii in cerebrospinal fluid was positive; therefore, he was diagnosed with TE. Anti-Toxoplasma therapy led to clinical improvement, and the result of subsequent PCR was negative. However, he developed left-sided hemiplegia on Day 306. Head MRI revealed a new lesion and a growing lesion, presenting as ring-enhanced nodules. Brain biopsy was performed, and a pathologic diagnosis of Epstein-Barr virus-associated CNS-PTLD was made. There was no evidence of TE. He was treated successfully by reducing immunosuppressants, followed by rituximab administration and a donor lymphocyte infusion, resulting in complete remission. While T.gondii-specific PCR has great value for diagnosis of TE, CNS-PTLD can be diagnosed only by brain biopsy; hence, brain biopsy may be warranted in cases of suspected PTLD.

Cerebrospinal fluid Plasmodium falciparum histidine-rich protein-2 in pediatric cerebral malaria.

BACKGROUND: Cerebral malaria (CM) causes a rapidly developing coma, and remains a major contributor to morbidity and mortality in malaria-endemic regions. This study sought to determine the relationship between cerebrospinal fluid (CSF) Plasmodium falciparum histidine rich protein-2 (PfHRP-2) and clinical, laboratory and radiographic features in a cohort of children with retinopathy-positive CM. METHODS: Patients included in the study were admitted (2009-2013) to the Pediatric Research Ward (Queen Elizabeth Central Hospital, Blantyre, Malawi) meeting World Health Organization criteria for CM with findings of malarial retinopathy. Enzyme-linked immunosorbent assay was used to determine plasma and CSF PfHRP-2 levels. Wilcoxon rank-sum tests and multivariable logistic regression analysis assessed the association of clinical and radiographic characteristics with the primary outcome of death during hospitalization. RESULTS: In this cohort of 94 patients, median age was 44 (interquartile range 29-62) months, 53 (56.4%) patients were male, 6 (7%) were HIV-infected, and 10 (11%) died during hospitalization. Elevated concentrations of plasma lactate (p = 0.005) and CSF PfHRP-2 (p = 0.04) were significantly associated with death. On multivariable analysis, higher PfHRP-2 in the CSF was associated with death (odds ratio 9.00, 95% confidence interval 1.44-56.42) while plasma PfHRP-2 was not (odds ratio 2.05, 95% confidence interval 0.45-9.35). CONCLUSIONS: Elevation of CSF, but not plasma PfHRP-2, is associated with death in this paediatric CM cohort. PfHRP-2 egress into the CSF may represent alteration of blood brain barrier permeability related to the sequestration of parasitized erythrocytes in the cerebral microvasculature.

Quantification of Plasmodium falciparum histidine-rich protein-2 in cerebrospinal spinal fluid from cerebral malaria patients.

A cerebrospinal fluid (CSF) biomarker for cerebral malaria (CM) has not been validated. We examined the detection, semiquantification, and clinical use of the Plasmodium falciparum histidine-rich protein-2 (PfHRP-2) as a parasite antigen biomarker for CM. The PfHRP-2 was detected in archival CSF samples from CM patients from Tanzania both by a newly developed sensitive and specific immuno-polymerase chain reaction (72 of 73) and by rapid diagnostic tests (62 of 73). The geometric mean PfHRP-2 CSF concentration was 8.76 ng/mL with no differences in those who survived (9.2 ng/mL), those who died (11.1 ng/mL), and those with neurologic sequelae (10.8 ng/mL). All aparasitemic endemic and nonendemic control samples had undetectable CSF PfHRP-2. In a separate group of 11 matched plasma and CSF cerebral malaria patient samples, the ratio of plasma to CSF PfHRP-2 was 175. The CSF PfHRP-2 reflects elevated plasma PfHRP-2 rather than elevated CM-specific CSF ratios, falling short of a validated biomarker.

Immunospecific immunoglobulins and IL-10 as markers for Trypanosoma brucei rhodesiense late stage disease in experimentally infected vervet monkeys.

OBJECTIVE: To determine the usefulness of IL-10 and immunoglobulin M (IgM) as biomarkers for staging HAT in vervet monkeys, a useful pathogenesis model for humans. METHODS: Vervet monkeys were infected with Trypanosoma brucei rhodesiense and subsequently given sub-curative and curative treatment 28 and 140 days post-infection (dpi) respectively. Matched serum and CSF samples were obtained at regular intervals and immunospecific IgM, immunoglobulin G (IgG) and IL-10 were quantified by ELISA. RESULTS: There was no detectable immunospecific IgM and IgG in the CSF before 49 dpi. CSF IgM and IgG and serum IgM were significantly elevated with peak levels coinciding with meningoencephalitis 98 dpi. The serum IL-10 was upregulated in both early and late disease stage, coinciding with primary and relapse parasitaemia respectively. CSF white cell counts (CSF WCC) were elevated progressively till curative treatment was given. After curative treatment, there was rapid and significant drop in serum IgM and IL-10 concentration as well as CSF WCC. However, the CSF IgM and IgG remained detectable to the end of the study. CONCLUSIONS: Serum and CSF concentrations of immunospecific IgM and CSF IgG changes followed a pattern that mimics the progression of the disease and may present reliable and useful biomarkers of the disease stage. Due to rapid decline, serum IgM and IL-10 are, additionally, potential biomarkers of the success of chemotherapy.

Evaluation of a rapid ELISA technique for detection of circulating antigens of Toxoplasma gondii.

To evaluate a modified rapid ELISA method for detecting CAg during Toxoplasma gondii infection, we analyzed the specificity and sensitivity of the ELISA method by using experimental Toxoplasma infection in rabbits and also tested this method in human samples including 5428 serum, 548 cerebrospinal fluid and two breast milk samples. We prepared PcAb, and used it for rapid one-step sandwich ELISA testing in which an incubation time in the regular ELISA procedure was omitted. This method detected CAg at the concentration of 31.2 ng/mL, and no cross-reaction was found with antigens of protozoa (Cryptosporidium parvum, Plasmodium falciparum), trematode (Schistosoma japonicum, Paragonimus sp.) and nematode (Brugia malayi, Ancylostoma duodenale, Ascaris lumbricoides and Trichinella spiralis). CAg was detected in rabbit serum 3 days after infection, and optical density values reached a peak 9-13 days after infection, then declined gradually. Among human serum samples, the positive rate of CAg was 2.11% in cerebral paralysis patients, whereas it was 0.22% or 0.71% in patients without neurological symptoms or in uncomplicated pregnant women. The difference among these three groups was statistically significant (P < 0.05). The positive rate of cerebrospinal fluid samples from cerebral paralysis patients was 10.58%. There is a statistically significant difference between the positive rates of meat-packing workers and blood donors (P < 0.01). In the retrospective analysis, CAg was detected in accordance with the onset of clinical symptoms, suggesting that CAg could reflect the clinical course in humans. Together with these results, CAg detected in the modified rapid sandwich ELISA could be a sensitive marker for acute and active infection of T. gondii.

Expression variance, biochemical and immunological properties of Toxoplasma gondii dense granule protein GRA7.

During intracellular stay, Toxoplasma gondii secretes dense granule proteins (GRA) which remodel the parasitophorous vacuole and are considered functional in parasite-host interrelation. Comparative analysis of parasites from mouse-virulent strain BK and an in vitro attenuated variant revealed that the level of GRA7 expression correlates with T. gondii virulence: proteome analysis and quantitation by immunoblot demonstrated a massive decrease in GRA7 steady-state synthesis parallel to the loss of virulence. Properties of GRA7 that are pertinent to its membrane targeting and to GRA7-directed immune resistance were studied in detail. GRA7 is exclusively membrane-associated in both parasites and infected host cells as demonstrated by subcellular fractionations. Triton X-114 partitioning of isolated parasites substantiated that GRA7 is an integral membrane protein, the hydrophobic stretch from amino acid 181 to 202 providing a possible membrane anchor. A fraction enriched for membranous material from infected host cells contained additional forms of GRA7 with reduced mobility in gel electrophoresis, indicating that the protein is modified after exocytosis from the parasite. By flow cytometric analysis, GRA7 was detected on the surface of intact host cells. An intracellular origin of surface-associated GRA7 seems likely since GRA7 released from extracellular parasites failed to label the host cell surface. Consistent with a role at a parasite-host interface, GRA7 proved to be a target antigen of the intracerebral immune response as evidenced by the presence of GRA7-specific antibodies in mouse cerebrospinal fluid during chronic infection.

Efficacy of a novel reverse transcriptase-polymerase chain reaction (RT-PCR) for detecting Toxoplasma gondii bradyzoite gene expression in human clinical specimens.

A reverse transcriptase-polymerase chain reaction (RT-PCR) assay, was performed to evaluate the transcription degree of bradyzoite- or tachyzoite-specific genes of Toxoplasma gondii on cerebrospinal fluid (CSF) specimens from AIDS patients with toxoplasmic encephalitis (TE), and to distinguish an asymptomatic latent infection from a reactivated disease. This method was compared with nested DNA amplification (n)-PCR. The mRNA expression of the representative T. gondii cystic matrix (MAG1) or bradyzoite-specific (SAG4) genes was investigated on CSF obtained from AIDS patients with first episode (no. 11) or relapse (no. 8) of TE. The mRNA expression of tachyzoite-specific (SAG1) gene was also studied. New designed oligonucleotide primers and probes, which identify a 212 bp fragment inside to the open reading MAG1 sequence, were employed in both RT-PCR and n-PCR assays. Oligo-dT primed cDNA synthesis appeared a suitable method for subsequent analysis by n-PCR. RT-PCR has been shown to be more sensitive and specific than n-PCR. MAG1 and SAG4 gene expression was detected in 8 (100%) and 6 (75%) patients with TE relapses, respectively, while SAG1 detected 7 (63%) patients with TE first episode. These findings suggest that RT-PCR method is able to identify the bradyzoite stage of T. gondii especially in patients who are at risk for TE relapse.

Detection of Toxoplasma gondii soluble antigen, SAG-1(p30), antibody and immune complex in the cerebrospinal fluid of HIV positive or negative individuals

Active infection by T. gondii was evaluated by immunoassay for soluble SAG-1 (p30), the major surface antigen from T. gondii, specific antibodies and immune complexes in human cerebrospinal fluid (CSF) samples. A total of 263 samples of CSF were collected from hospitalized patients presenting neurological disorders and analyzed for antibodies to HIV. Patients were divided into two groups: HIV positive (n = 96) or HIV negative (n =167). The results of the assays showed that 45 of all samples were positive for soluble SAG-1. Toxoplasma Ag/Ab immune complexes were detected in 19 of the CSF samples and 62 were positive for T. gondii- specific IgG. A combination of these assays in the presence of clinical findings consistent with active Toxoplasma infection may predict the presence of toxoplasmic encephalitis. Moreover, detection of soluble SAG-1 in the CSF of these individuals appears consistent with active infection.

Detection of Toxoplasma gondii soluble antigen, SAG-1(p30), antibody and immune complex in the cerebrospinal fluid of HIV positive or negative individuals.

Active infection by T. gondii was evaluated by immunoassay for soluble SAG-1 (p30), the major surface antigen from T. gondii, specific antibodies and immune complexes in human cerebrospinal fluid (CSF) samples. A total of 263 samples of CSF were collected from hospitalized patients presenting neurological disorders and analyzed for antibodies to HIV. Patients were divided into two groups: HIV positive (n = 96) or HIV negative (n =167). The results of the assays showed that 45% of all samples were positive for soluble SAG-1. Toxoplasma Ag/Ab immune complexes were detected in 19% of the CSF samples and 62% were positive for T. gondii- specific IgG. A combination of these assays in the presence of clinical findings consistent with active Toxoplasma infection may predict the presence of toxoplasmic encephalitis. Moreover, detection of soluble SAG-1 in the CSF of these individuals appears consistent with active infection.

Evaluation of different techniques in the diagnosis of Toxoplasma encephalitis.

This study evaluated the detection of antibodies, circulating antigens and parasite DNA by polymerase chain reaction (PCR) in the diagnosis of toxoplasma encephalitis. The detection of antibody classes and IgG avidity were not useful diagnostically. The detection of circulating antigens by the ELISA system described was not sufficiently sensitive. The detection of DNA by PCR was the most useful test especially in untreated patients, with a sensitivity of 62% overall, 81% in untreated patients and only 20% in treated patients. The use of non-isotopic probes makes the use of this technique feasible in routine diagnostic parasitology laboratories.

Sensitivity of antigen ELISA test for detecting Trypanosoma evansi antigen in horses in the subtropical area of Argentina.

The sensitivity of an antigen detection enzyme immunoassay (Ag-ELISA) based on a Trypanosoma brucei group-specific monoclonal antibody was evaluated to detect circulating Trypanosoma evansi antigen in horse sera. Three horses and 2 mules were experimentally infected with T. evansi. Circulating antigens were detected on 7 and 21 days postinfection. Antigen levels increased during the course of the illness and remained high even when parasitemia was low or when parasites could not be detected. Antigens were cleared from serum when drug treatment was effective but persisted when it was not. In 6 outbreaks of "mal de caderas" involving 125 horses, T. evansi was found in 78 horses using standard parasite detection methods and antigenemia was detected in 58 of them (74%). The Ag-ELISA sensitivity rate varied between 63% and 100% for the 6 different outbreaks. A combination of Ag-ELISA and parasitologic methods diagnosed a total of 93 infected animals. These results show that the Ag-ELISA test is useful both to diagnose T. evansi and to assess the efficacy of drug treatment in horses.

Diagnosis of Trypanosoma brucei gambiense sleeping sickness using an antigen detection enzyme-linked immunosorbent assay.

A monoclonal antibody-based enzyme-linked immunosorbent assay (antigen ELISA) developed for detection of trypanosome antigens in the serum and cerebrospinal fluid (CSF) of patients as a means for diagnosis of Trypanosoma brucei gambiense sleeping sickness was evaluated at the Bureau Central de la Trypanosomiase, Kinshasa, Zaire. Sixty-nine (89.6%) of 77 parasitologically confirmed cases examined at the Daloa clinic had antigens in serum; 35 (45.5%) had antigens in CSF and, in 4 of these, the antigens were detected in CSF only. Taking the serum and CSF results together, 73 (94.8%) of the 77 patients were positive in the assay. In the Kinshasa series, 168 (89.4%) of 188 parasitologically confirmed cases were positive by antigen ELISA. The controls, who included 165 blood donors and 40 patients with malaria, 2 with hydatidosis and 12 with leishmaniasis, were negative by antigen ELISA. Analysis of CSF results for 35 patients who had antigens in CSF revealed that 34 (97.1%) had elevated CSF white cell counts, 29 (82.9%) had elevated protein levels, and 23 (65.7%) had trypanosomes in their CSF. Moreover, analysis of results for 34 patients whose CSF had been shown to harbour trypanosomes by the double centrifugation technique showed that 24 (70.6%) had antigens in CSF, 28 (82.6%) had elevated protein levels, and 33 (97.1%) had elevated CSF white cell counts. Antigens were rapidly cleared from peripheral circulation following institution of treatment. Antigen clearance was accompanied by a rapid fall in CSF protein levels and white cell counts. These results demonstrate the potential of antigen ELISA, not only as a tool for diagnosis, but also for clinical staging and treatment follow-up of patients with T. b. gambiense sleeping sickness.

Multicentre evaluation of an antigen-detection ELISA for the diagnosis of Trypanosoma brucei rhodesiense sleeping sickness.

The performance of an enzyme-linked immunosorbent assay (antigen ELISA) for the detection, in serum or cerebrospinal fluid, of an invariant trypanosome antigen to diagnose Trypanosoma brucei rhodesiense sleeping sickness was evaluated in four clinical treatment centres. The test, which was carried out in polystyrene test-tubes, was positive in 88 (88.9%) of 99 parasitologically confirmed cases that were tested at the National Institute for Medical Research, Tabora, United Republic of Tanzania; 99 (94.3%) of 105 cases tested at the National Sleeping Sickness Control Programme, Jinja, Uganda; 86 (87.8%) of 98 cases tested at the Uganda Trypanosomiasis Research Organisation, Tororo, Uganda; and 59 (96.7%) of 61 cases tested at the Tropical Diseases Research Centre, Ndola, Zambia. The overall detection rate was 91.5%. There was no cross-reactivity with the agents of the common bacterial, viral, or parasitic diseases prevalent in the areas where the studies were conducted. The only false-positive result involved a blood donor from a trypanosomiasis endemic focus. The test was simple to perform, was read visually, and is therefore a potential tool for diagnosing human African trypanosomiasis.

Detection of Toxoplasma gondii antigens by a dot-immunobinding technique.

A sensitive assay for the detection of antigens of Toxoplasma gondii by spotting samples directly onto nitrocellulose paper was developed. The sensitivity ranged from 10 to 40 pg of antigen diluted in phosphate-buffered saline and 40 to 130 pg of antigen diluted in normal mouse serum, normal human serum, or human cerebrospinal fluid. T. gondii antigen in serum samples taken from mice infected with T. gondii was detectable by day 2 of infection. Antigen was also detectable in cerebrospinal fluid samples taken from four of six infants congenitally infected with T. gondii and in serum samples from two of these infants.