Loss of B Cells in Patients with Heterozygous Mutations in IKAROS.

BACKGROUND: Common variable immunodeficiency (CVID) is characterized by late-onset hypogammaglobulinemia in the absence of predisposing factors. The genetic cause is unknown in the majority of cases, and less than 10% of patients have a family history of the disease. Most patients have normal numbers of B cells but lack plasma cells. METHODS: We used whole-exome sequencing and array-based comparative genomic hybridization to evaluate a subset of patients with CVID and low B-cell numbers. Mutant proteins were analyzed for DNA binding with the use of an electrophoretic mobility-shift assay (EMSA) and confocal microscopy. Flow cytometry was used to analyze peripheral-blood lymphocytes and bone marrow aspirates. RESULTS: Six different heterozygous mutations in IKZF1, the gene encoding the transcription factor IKAROS, were identified in 29 persons from six families. In two families, the mutation was a de novo event in the proband. All the mutations, four amino acid substitutions, an intragenic deletion, and a 4.7-Mb multigene deletion involved the DNA-binding domain of IKAROS. The proteins bearing missense mutations failed to bind target DNA sequences on EMSA and confocal microscopy; however, they did not inhibit the binding of wild-type IKAROS. Studies in family members showed progressive loss of B cells and serum immunoglobulins. Bone marrow aspirates in two patients had markedly decreased early B-cell precursors, but plasma cells were present. Acute lymphoblastic leukemia developed in 2 of the 29 patients. CONCLUSIONS: Heterozygous mutations in the transcription factor IKAROS caused an autosomal dominant form of CVID that is associated with a striking decrease in B-cell numbers. (Funded by the National Institutes of Health and others.).

Immune function surveillance: association with rejection, infection and cardiac allograft vasculopathy.

BACKGROUND: Rejection, cardiac allograft vasculopathy (CAV), and infection are significant causes of mortality in heart transplantation recipients. Assessing the immune status of a particular patient remains challenging. Although endomyocardial biopsy (EMB) and angiography are effective for the identification of rejection and CAV, respectively, these are expensive, invasive, and may have numerous complications. The aim of this study was to evaluate the immune function and assess its utility in predicting rejection, CAV, and infection in heart transplantation recipients. METHODS: We prospectively obtained samples at the time of routine EMB and when clinically indicated for measurement of the ImmuKnow assay (IM), 12 cytokines and soluble CD30 (sCD30). EMB specimens were evaluated for acute cellular rejection, and antibody-mediated rejection (AMR). CAV was diagnosed by the development of angiographic coronary artery disease. Infectious episodes occurring during the next 30 days after testing were identified by the presence of positive bacterial or fungal cultures and/or viremia that prompted treatment with antimicrobials. RESULTS: We collected 162 samples from 56 cardiac transplant recipients. There were 31 infection episodes, 7 AMR, and 4 CAV cases. The average IM value was significantly lower during infection, (P = .04). Soluble CD30 concentrations showed significantly positive correlation with infection episodes, (P = .001). Significant positive correlation was observed between interleukin-5(IL-5) and AMR episodes (P = .008). Tumor necrosis factor-α and IL-8 showed significant positive correlation with CAV (P = .001). CONCLUSIONS: Immune function monitoring appears promising in predicting rejection, CAV, and infection in cardiac transplantation recipients. This approach may help in more individualized immunosuppression and it may also minimize unnecessary EMBs and cardiac angiographies.

Clinical relevance of multiple antibody specificity testing in anti-phospholipid syndrome and recurrent pregnancy loss.

We wanted to evaluate whether testing for anti-phosholipid antibodies other than anti-cardiolipin (aCL) and anti-beta-2 glycoprotein I (abeta2GPI) immunoglobulin (Ig)G and IgM identifies patients with recurrent pregnancy loss (RPL) who may be positive for anti-phospholipid syndrome (APS). In a cross-sectional study comprising 62 patients with APS, 66 women with RPL, 50 healthy blood donors and 24 women with a history of successful pregnancies, we tested IgM and IgG antibodies to phosphatidic acid, phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl glycerol, phosphatidyl inositol and phosphatidyl serine with and without beta-2 glycoprotein I (beta2GPI) from a single manufacturer as well as aCL and abeta2GPI antibodies. Diagnostic accuracies of individual and combined anti-phospholipid (aPL) assays were assessed by computing sensitivities, specificities, positive predictive values and negative predictive values together with their 95% confidence intervals. There was a general trend for increased sensitivities in the presence of beta2GPI co-factor with significant effect for certain specificities. The overall combined sensitivity of the non-recommended aPL assays was not significantly higher than that of the aCL and aB2GPI tests. Multiple aPL specificities in RPL group is not significantly different from controls and therefore of no clinical significance.

Elevation of IgA anti-epidermal transglutaminase antibodies in dermatitis herpetiformis.

BACKGROUND: Dermatitis herpetiformis (DH) is a papulovesicular eruption caused by ingestion of gluten. It is characterized by the deposition of IgA in the dermal papillae. IgA antibodies directed at tissue transglutaminase (TG2) are elevated in gluten-sensitive diseases including DH and coeliac disease (CD). More recently, antibodies directed at epidermal transglutaminase (TG3) were identified in patients with DH, and this may be the dominant autoantigen in this disease. OBJECTIVES: To measure IgA antibodies to TG3 and TG2 in patients with DH and CD, and control populations. METHODS: Serum IgA antibodies against TG2 and TG3 were measured from adults with DH, adults and children with CD, patients with psoriasis, adult Red Cross blood donors, and paediatric controls. RESULTS: Patients with DH and CD had elevated levels of IgA anti-TG2 antibodies compared with control populations. The levels in the patients with DH and adults with CD were similar. IgA anti-TG2 antibodies were higher in the children with CD compared with adults with DH and CD, and with control populations. Patients with DH and adults with CD had elevated levels of IgA anti-TG3 antibodies compared with children with CD and control populations. There was a trend towards higher levels in the patients with DH compared with adults with CD. CONCLUSIONS: IgA antibodies to TG3 are elevated in patients with DH and adults with CD. The progressive expansion of the epitope-binding profile of IgA antitransglutaminase antibodies in patients with CD may explain the development of DH in patients with undiagnosed CD during their adult life.

Antibody reactivity to heat shock protein 70 and inner ear-specific proteins in patients with idiopathic sensorineural hearing loss.

Deafness is attributable to autoimmunity in a subset of adult patients with sensorineural hearing loss (SNHL) of unknown aetiology. To determine the roles of self-antigens in the pathogenesis of idiopathic SNHL, we analysed antibody responses to the inner ear-specific proteins, cochlin and beta-tectorin as well as the non-specific heat shock protein 70 (HSP70). Recombinant cochlin and beta-tectorin proteins were used in a qualitative Western blot assay for the detection of antigen-specific IgG antibodies in 58 patients with idiopathic SNHL and 28 healthy blood donors. In the same study cohort, we also used a Western blot assay to assess IgG antibody responses to the recombinant human HSP70. Of the 58 patient samples analysed, 19 tested positive to the HSP70, eight to cochlin and one to beta-tectorin, giving a prevalence of 33, 14 and 2%, respectively. Only one patient sample was reactive for HSP70, cochlin and beta-tectorin, seven of the remaining eight cochlin IgG antibody-positive samples were monospecific. Thus, cochlin-specific antibodies were observed predominantly in HSP70 IgG-negative patients demonstrating an additive value for testing this antibody response in patients with idiopathic SNHL.

Immunoglobulin (Ig) M antibody against myelin associated glycoprotein (MAG): A comparison of methods.

The presence of immunoglobulin (Ig)M antibody against myelin associated glycoprotein (MAG) has been associated with autoimmune demyelinating, sensorimotor neuropathies. Approximately 50% of patients with IgM paraproteinemia and associated peripheral neuropathy possess antibodies against MAG. These autoantibodies are thought to interfere with the process of myelination, myelin maintenance, or axon-Schwann cell interaction. The detection of these autoantibodies is useful to the clinician and is suggestive of active demyelination in a peripheral neuropathy. Our objective in this study was to compare the results obtained using three different methods (dual enzyme immunoassay [EIA], immunofluorescent antibody [IFA] and Western blot [WB]) for detecting IgM antibody against MAG in patients suspected of having autoimmune demyelinating neuropathies. Since the dual EIA utilized two different antigens, results from this assay were separated into two groups: MAG and sulfate-3-glucuronyl paragloboside (SGPG). When compared to WB (gold standard), percent agreement, sensitivity, and specificity for EIA and IFA are as follows: MAG EIA (68.3, 100.0, and 60.6); SGPG EIA (95.1, 100.0, and 93.9); and myelin IFA (97.6, 100.0, and 97.0). The authors conclude that the SGPG EIA and myelin IFA compared well with the standard WB method when detecting IgM antibody against MAG (100 kD). Many sera demonstrated reactivity on the MAG EIA that were negative by WB (100 kD glycoprotein). The authors recommend screening for MAG IgM in suspected patient sera by SGPG EIA or myelin IFA and utilizing these same methods to titer sera confirmed positive by WB.

Evasion of human innate and acquired immunity by a bacterial homolog of CD11b that inhibits opsonophagocytosis.

Microbial pathogens must evade the human immune system to survive, disseminate and cause disease. By proteome analysis of the bacterium Group A Streptococcus (GAS), we identified a secreted protein with homology to the alpha-subunit of Mac-1, a leukocyte beta2 integrin required for innate immunity to invading microbes. The GAS Mac-1-like protein (Mac) was secreted by most pathogenic strains, produced in log-phase and controlled by the covR-covS two-component gene regulatory system, which also regulates transcription of other GAS virulence factors. Patients with GAS infection had titers of antibody specific to Mac that correlated with the course of disease, demonstrating that Mac was produced in vivo. Mac bound to CD16 (FcgammaRIIIB) on the surface of human polymorphonuclear leukocytes and inhibited opsonophagocytosis and production of reactive oxygen species, which resulted in significantly decreased pathogen killing. Thus, by mimicking a host-cell receptor required for an innate immune response, the GAS Mac protein inhibits professional phagocyte function by a novel strategy that enhances pathogen survival, establishment of infection and dissemination.

Granulocyte function disorders: aspects of development, genetics and management.

The field of phagocytic disorders has attained major biologic and clinical significance in the past 40 years. The development of exciting new techniques in molecular biology and the cellular physiology of signal transduction have made it possible to identify the genetic defects involved in many of these disorders. Moreover through immunopharmacologic intervention, bone marrow or peripheral or cord blood stem cell transplantation along with the prospect of gene therapy, we have begun attempts to at least partially correct genetic defects in cell development and activation pathways in the entire spectrum of phagocyte disorders. Carrier detection and prenatal diagnosis employing with chain reaction techniques or direct nucleotide sequencing in fetal blood have made these diseases potentially preventable or treatable in utero or shortly after birth.

The effects of polyvinyl chloride and polyolefin blood bags on red blood cells stored in a new additive solution.

BACKGROUND AND OBJECTIVES: Red blood cells (RBCs) must be stored in polyvinyl chloride (PVC) bags plasticized with di-2-ethylhexyl phthalate or a similar plasticizer to achieve their full storage life with conventional storage solutions. Improved storage solutions might remove this requirement and allow blood storage in other plastics. Experimental Additive Solution-61 (EAS-61), which maintains RBCs for 9 weeks with reduced haemolysis and satisfactory 51Cr 24-h recovery, is an appropriate candidate improved RBC storage solution. MATERIALS AND METHODS: Twenty-four units of packed RBCs were pooled in groups of four units, each pool was realiquoted into four units and stored, six pooled units per arm, in one of the following: 100 ml of EAS-61 in PVC; 200 ml of EAS-61 in PVC; 100 ml of EAS-61 in polyolefin (PO); and 200 ml of EAS-61 in PO. Haemolysis, RBC morphology indices, RBC ATP concentrations, and other measures of RBC metabolism and function were measured weekly. RESULTS: RBC haemolysis exceeded 1% by 7 weeks in PO bags containing 100 ml or 200 ml of EAS-61. In PVC bags, haemolysis was less than 1% at 11 weeks. RBC ATP concentrations were 1 mol/g of haemoglobin (Hb) higher at 2 weeks in the PVC-stored units. CONCLUSIONS: RBCs stored in PVC had markedly less haemolysis and higher RBC ATP concentrations than those stored in PO. Haemolysis would limit RBC storage in PO bags to a duration of 6 weeks, even with EAS-61.

The role of electrolytes and pH in RBC ASs.

BACKGROUND: Experimental additive solutions (EASs) containing saline, adenine, glucose, mannitol and disodium phosphate can support RBCs for 9 or 10 weeks if used in 200- or 300-mL volumes. The effects of variations in the electrolyte composition and volume of EASs were explored. STUDY DESIGN AND METHODS: In three four-arm studies, 24 RBC units were pooled in groups of 4 and realiquoted as test units to ensure that all donors were equally represented in each study arm. In Study 1, units were stored for 11 weeks in EAS containing 0, 10, 20, or 30 mmol per L of sodium bicarbonate. In Study 2, units were stored for 9 weeks in EAS containing 26, 50, 100, or 150 mmol per L of sodium chloride. In Study 3, units were stored in 100 or 200 mL of AS-3 or EAS-61. RBC ATP concentrations and hemolysis were measured weekly. RESULTS: Increasing the sodium bicarbonate content of EASs increased the pH throughout storage and increased RBC ATP concentrations in the later phases of storage, but it had no effect on hemolysis. Increased sodium chloride content of EASs led to lower RBC ATP concentrations and increased hemolysis. In EAS-61, RBC ATP concentrations were increased throughout storage, and hemolysis was lower than that of RBCs stored in AS-3. CONCLUSION: RBC ATP synthesis is highly dependent on the pH of the AS. Hemolysis is affected by the salt content and volume of the AS.

The effect of two additive solutions on the postthaw storage of RBCs.

BACKGROUND: Sterile systems for freezing and for washing thawed blood will allow the storage of RBCs for more than 24 hours after removal of the cryoprotectant glycerol. This study assessed the effect of two ASs in maintaining deglycerolized RBCs. STUDY DESIGN AND METHODS: Twenty-four RBC units were stored for 6 days, pooled in groups of 4, realiquoted, sterilely glycerolized, and frozen. One month later, the units were thawed, sterilely deglycerolized by using an automated system (H215; Haemonetics), and stored for 5 weeks in either 100 or 200 mL of AS-3 or an experimental AS (EAS-61). Sterile samples were taken weekly for chemical and morphometric analysis. RESULTS: The glycerolization and deglycerolization process produced highly comparable RBC units, but it caused a marked reduction of RBC pH, to about 6.4 at the beginning of storage. The addition of acidic AS-3 further reduced the pH, which in turn reduced glucose consumption, lactate formation, and RBC ATP concentrations. Alkaline EAS-61 increased these measures. Hypotonic EAS-61 caused increased cell swelling and hemolysis, despite better RBC morphology. CONCLUSIONS: Automation of sterile glycerolization and deglycerolization with the H215 works well, but the solutions should be reformulated for extended postthaw storage. This would best be accomplished by raising the pH of the wash solutions by the addition of disodium phosphate or sodium bicarbonate or both, by using alkaline ASs, and by matching the osmolality of the wash solution and ASs.

Multiplex analysis of heterophil antibodies in patients with indeterminate HIV immunoassay results.

We hypothesized that heterophil antibodies reactive with animal proteins used in blot preparation caused nonspecific staining (NSS) on HIV Western blot (WB) studies, causing indeterminate results. We analyzed samples showing NSS on HIV WB using a multiplexed immunoassay to simultaneously measure IgG antibodies to animal IgG (bovine, goat, sheep, mouse) and bovine serum albumin. Heterophil antibodies reactive with IgG from several animal species were detected in 23 (49%) of 47 samples showing NSS on HIV WB; 15 positive samples demonstrated antibodies to all 5 antigens. Similar IgG heterophil antibodies were detected in only 2 (8%) of 24 control samples. Of the HIV WB samples with a positive HIV-1 enzyme-linked immunosorbent assay (ELISA) result at the time of WB testing (11/47), heterophil antibodies were found in 8 (73%) of 11. Preabsorption with bovine, goat, and sheep IgG removed heterophil antibodies detected by the multiplexed assay and, in some cases, eliminated reactivity in ELISA and WB testing. Heterophil antibodies are associated with indeterminate HIV immunoassay results and are an important cause of false-positive HIV ELISA results. Multiplexed immunoassays provide a powerful tool for screening patients for heterophil antibodies and resolving possible false-positive results.

IgA antibodies against endomysium and transglutaminase: a comparison of methods.

Recently, the endomysial antigen has been identified as the protein cross-linking enzyme known as tissue transglutaminase (tTG). Our objective was to compare a novel enzyme immunoassay (EIA) that detects IgA antibody against tTG to two standard IFA methods utilizing thin tissue sections of rat kidney/rat stomach (KS) and distal primate esophagus (PE) as substrates to detect IgA antibody against endomysium (EMA). Sera from 100 patients suspected of having gluten-sensitive enteropathy (GSE) and 23 sera possessing various antibodies used for EIA cross-reactivity studies were included. Additional tests, performed routinely in our laboratory, were utilized to further assess sera from patients suspected having GSE. These tests include anti-gliadin IgA antibody (AGA) and anti-reticulin IgA antibody (ARA) and are part of the European Society for Pediatric Gastroenterology and Nutrition (ESPGAN) revised criteria for diagnosing GSE. When compared to IFA using KS, the tTG EIA had a sensitivity of 87.5%, was 97.1% specific, and had an overall agreement of 94.0%. When compared to IFA using PE, the tTG EIA had a sensitivity of 92.6%, was 93.2% specific, and had an overall agreement of 93.0%. When the KS IFA was compared to the PE IFA for EMA, the KS IFA had a sensitivity of 96.3%, was 91.8% specific, and had an overall agreement of 93.0%. The majority of sera that were positive for tTG but were negative by IFA (KS, n = 2/PE, n = 5) possessed IgA antibodies against gliadin and/or reticulin. Five of six sera with negative results by PE IFA were positive by the KS IFA and possessed one or more antibodies to tTG and/or gliadin and/or reticulin. We conclude that the tTG EIA compares well to both KS and PE IFAs when detecting IgA antibody against endomysium. We do not recommend the use of PE to detect EMA primarily because of the inconsistencies (i.e., tissue selection, quality, and preparation) and limited availability of commercially prepared PE tissue.

Comparison of four enzyme immunoassays with a western blot assay for the determination of type-specific antibodies to herpes simplex virus.

Most current enzyme immunoassays (EIAs) differentiate inadequately between types 1 and 2 herpes simplex virus (HSV) antibodies since significant cross-reactivity exists. We compared 4 IgG type-specific EIAs using a Western blot assay for resolution of discrepant results. The Diamedix had sensitivities of 100% for types 1 and 2 but specificities of only 71% and 61%, respectively. The cross-reactivity rate was 82% in positive samples tested. For HSV types 1 and 2, the Zeus sensitivities were 92% and 98%, respectively; specificities were 72% and 79%, respectively; the cross-reactivity rate was 54%. For HSV types 1 and 2, the Wampole sensitivities were 98% and 95%, respectively; specificities were 68% and 85%, respectively; the cross-reactivity rate was 47%. For HSV types 1 and 2, the Meridian sensitivities were 98% and 90%, respectively; specificities were 96% and 100%, respectively; no cross-reactivity was found between positive samples tested. While the Diamedix, Zeus, and Wampole assays showed good sensitivity, they lacked type specificity. The Meridian EIA offers the highest specificity along with no observed cross-reactivity. This EIA may be an easier, reliable alternative to Western blot for the determination of HSV type-specific antibodies.

RBC storage for 11 weeks.

BACKGROUND: Increasing the length of RBC storage can increase both RBC availability and quality. This work addresses 11-week RBC storage in experimental ASs (EASs). STUDY DESIGN AND METHODS: Three studies were performed. In the first, 24-hour in vivo recovery of (51)Cr-labeled autologous RBCs was measured in nine volunteers after storage of their RBCs for 11 weeks in EAS 67. In the second study, 4 units of blood were divided and stored in aliquots with an EAS containing 0, 15, 30, or 45 mmol per L of mannitol; then hemolysis, RBC morphology, and microvesicle protein were measured. In the third study, 6 full units were stored for 12 weeks in the EAS containing 30 mmol per L of mannitol, with weekly sampling for morphologic and biochemical measures of RBC quality. RESULTS: RBCs stored for 11 weeks in EAS-67 had a mean 24-hour in vivo recovery of 79 +/- 5 percent, but the hemolysis was 1.35 +/- 0.68 percent. Increasing mannitol content of the EAS reduced hemolysis but increased microvesiculation. EAS-76, with 30 mmol per L of mannitol allowed 11-week storage with 0.48 +/- 0.10 percent hemolysis at 11 weeks and 0.62 +/- 0.14 percent hemolysis at 12 weeks. CONCLUSION: It is possible to store RBCs for 11 weeks in EAS with greater than 75 percent recovery and less than 1 percent hemolysis.

Growth failure, intracranial calcifications, acquired pancytopenia, and unusual humoral immunodeficiency: a genetic syndrome?

We report on two children who may represent a novel syndrome consisting of a deficiency of immunoglobulin-bearing B lymphocytes and serum antibody, deficient intrauterine and/or postnatal growth, intracranial calcifications, and acquired pancytopenia. Poor growth, intracranial calcifications, developmental delay, and hematological abnormalities are common manifestations of congenital infection. However, humoral immunodeficiency is not characteristic in these infections, and no infection was found on extensive evaluation. Rare genetic syndromes may mimic intrauterine infections and may also include immunodeficiency. However the children reported here lack important characteristics or share distinctive manifestations not described in these disorders. Infants presenting with apparent congenital infections in whom a specific infectious cause cannot be identified should be followed carefully with immunological evaluations since this disorder may be progressive and considerable morbidity is attributable to hematological and immunological manifestations.

The effects of phosphate, pH, and AS volume on RBCs stored in saline-adenine-glucose-mannitol solutions.

BACKGROUND: RBC ATP concentrations are the most important correlate of RBC viability. Tests were performed to determine whether increased AS volume, pH, and phosphate content increased stored RBC ATP concentrations. STUDY DESIGN AND METHODS: In three studies, packed RBCs were pooled in groups of 3 or 4 units and realiquoted as combined units to reduce intradonor differences. Pooled units were stored in the licensed ASs, AS-1 or AS-5, which contain saline, adenine, glucose, and mannitol (SAGM), or in experimental ASs (EASs) containing SAGM and disodium phosphate. Ten pools were stored in AS-1 at RBC concentrations equivalent to 100, 200, or 300 mL of AS. Six pools were stored in 100, 200, 300, or 400 mL volumes of EAS-61. Ten pools were stored in 100 mL of AS-5, 200 mL of EAS-61, or 300 mL of EAS-64. RBC ATP concentration and other measures of RBC metabolism and function were measured weekly. RESULTS: RBC ATP concentrations decreased sooner with storage in increasing volumes of AS-1. In EAS-61 and EAS-64, RBC ATP concentrations initially increased and stayed elevated longer with increasing AS volume. CONCLUSIONS: The addition of disodium phosphate to SAGM AS increases the RBC ATP concentrations. Reducing storage Hct appears to have a separate beneficial effect in reducing hemolysis.

Effects of group B streptococci on cord and adult mononuclear cell interleukin-12 and interferon-gamma mRNA accumulation and protein secretion.

Group B streptococci (GBS) are a major cause of early-onset infection in neonates. Neonates, who have defects in neutrophil function that likely contribute to susceptibility to GBS infection, are deficient in the production of the phagocyte activator interferon (IFN)-gamma. GBS-stimulated mRNA accumulation and protein secretion of IFN-gamma and interleukin (IL)-12, a major enhancer of IFN-gamma production, by mixed mononuclear cells (MMCs) from umbilical cord and adult peripheral blood was examined. GBS-exposed cord blood MMCs secreted lower concentrations of both IL-12 and IFN-gamma proteins than did MMCs from adults. IL-12 and IFN-gamma mRNA accumulation was examined by use of comparative reverse transcriptase-polymerase chain reaction. Cord blood MMCs accumulated less mRNA for both IL-12 and IFN-gamma than did adult blood MMC. The deficiency in cord blood cell production of IL-12 may have a role in inadequate IFN-gamma production, which contributes to the unique susceptibility of neonates to GBS infections.

Evaluation of a PCR probe capture assay for the detection of Toxoplasma gondii. Incorporation of uracil N-glycosylase for contamination control.

Toxoplasma gondii is a cyst-forming parasite of clinical relevance in humans primarily because of the neurologic abnormalities it can cause. In some clinical circumstances, it is desirable to detect the pathogen directly. We modified a commercially available Toxoplasma polymerase chain reaction (PCR) probe capture assay by incorporating uracil N-glycosylase (UNG) to prevent carryover amplicon contamination. In addition, UNG inactivation and DNA denaturation were accomplished chemically to simplify the DNA hybridization to the capture probe. The incorporation of UNG effectively eliminated carryover contamination; the probe capture assay showed a log increase in detection sensitivity compared with standard agarose gel electrophoresis. To assess sensitivity and possible inhibition of amplification, different sample types were spiked with Toxoplasma organisms. After DNA extraction and PCR amplification, a sensitivity of 2 tachyzoites for the assay was determined in buffered saline, cerebrospinal fluid (CSF), serum, and amniotic fluid; 20 tachyzoites for whole blood; and 200 tachyzoites for brain tissue. An additional 20 human serum and CSF samples submitted for Toxoplasma serologic testing were run by the PCR method. Of these, only an IgM-positive CSF sample was PCR positive. The Toxoplasma PCR probe capture assay showed good sensitivity and was not substantially inhibited by several different clinically relevant samples.