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JOURNAL OF CLINICAL MICROBIOLOGY, Apr. 2006, p. 1382–1389 0095-1137/06/$08.00ϩ0 doi:10.1128/JCM.44.4.1382–1389.2006Copyright 2006, American Society for Microbiology. All Rights Reserved.
Genotyping of Toxoplasma gondii by Multiplex PCR and Peptide-Based Serological Testing of Samples from Infants in Poland Diagnosed ´n,3,4 Jack S. Remington,4,5 Michael Grigg,6 Elzbieta Golab,7 Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, Missouri 931101; Department of Fetal-Maternal Medicine and Gynecology, Research Institute Polish Mother’s Memorial Hospital, Lodz, Poland2; Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, California 943053; Department of Immunology and Infectious Diseases, Research Institute, Palo Alto Medical Foundation, Palo Alto, California 943014; Division of Infectious Diseases and Geographical Medicine, Stanford University School of Medicine, Stanford, California 943055; Departments of Medicine and Microbiology & Immunology, University of British Columbia, Vancouver, British Columbia V5Z 3J5, Canada6; and Department of Medical Parasitology, National Institute of Hygiene, Warsaw, Poland7 Received 2 October 2005/Returned for modification 15 November 2005/Accepted 23 January 2006 Toxoplasma gondii has a clonal population genetic structure with three (I, II, and III) lineages that predominate
in North America and Europe. Type II strains cause most cases of symptomatic human infections in France and the
United States, although few other regions have been adequately sampled. Here we determined the parasite genotype
in amniotic fluid and cerebrospinal fluid samples from congenital toxoplasmosis cases in Poland. Nineteen con-
firmed congenital cases of toxoplasmosis were analyzed, including both severe and asymptomatic cases. The
genotype of parasite strains causing congenital infection was determined by direct PCR amplification and restric-
tion fragment length polymorphism analysis. Nested multiplex PCR analysis was used to type four independent
polymorphic markers. The sensitivity of multiplex nested PCR was >25 parasites/ml in amniotic fluid and cerebral
spinal fluid samples. Parasite DNA was successfully amplified in 9 of 19 samples (eight severely affected and one
asymptomatic fetus). Only genotype II parasites were identified as the source of T. gondii infection based on
restriction fragment length polymorphism analysis. Strains causing congenital infections were also typed indirectly
based on detection of antibodies to strain-specific peptides. Serotyping indicated that 12 of 15 cases tested were
caused by type II strains and these positives included both symptomatic and asymptomatic infections. Overall, the
combined analysis indicated that 14 of the cases were caused by type II strains. Our results are consistent with the
hypothesis that parasite burden is associated with severity of congenital toxoplasmosis and indicate that serological
testing provides a promising method for genotypic analysis of toxoplasmosis.
Toxoplasmosis is a common parasitic disease caused by the relatively avirulent in mice yet they readily establish chronic protozoan parasite Toxoplasma gondii. Seroprevalence varies infections characterized by tissue cysts that are highly infec- between different geographic regions: in Poland, 2,200 (41.3%) tious by the oral route (25, 27). Type I strains are more virulent out of 4,916 pregnant women were found to have T. gondii- in mice and have a greater capacity to cross tissue barriers in specific anti-immunoglobulin G (IgG) antibodies (20, 20a).
Infection can be acquired by ingestion of viable tissue cysts in Enhanced migration could potentially lead to greater capac- undercooked meat or oocysts excreted by cats (23). T. gondii is ity to cause congenital infection due to transplacental trans- a major cause of morbidity and mortality in congenitally in- mission, although such a relationship has not been directly fected infants and immunodeficient and immunocompromised demonstrated. A single study from Spain indicated that strains possessing the type I allele at the SAG2 locus were found in 6 The population genetic structure of T. gondii is highly clonal, of 13 cases of congenital infection (6). However, even strains despite a sexual phase in the life cycle (14, 25, 26). Three that are nonvirulent in the mouse model are capable of causing predominant clonal types (I, II, and III) are recently derived severe disease in humans, as shown by the prevalence of type from recombination between two highly similar ancestral line- II strains in congenital toxoplasmosis in France (1).
ages (8, 27). Recombinant genotypes are rarely found in na-ture, indicating infrequent sexual recombination between the While the majority of genotyping studies have been based on three lineages (1, 14). Type II strains have been identified as polymorphic DNA markers, one of the primary limitations of the cause of more than 70% of human cases of toxoplasmosis this method is the inability to type strains causing chronic in the United States and France (1, 5, 14). Type II strains are infection. Strains of T. gondii are highly similar antigenically;however, the recent identification of serological epitopes thatare strain specific raises the possibility of genotyping even * Corresponding author. Mailing address: Department of Molecular chronic infections based on serological profile (17). Serological Microbiology, Washington University School of Medicine, 660 S.
typing based on strain-specific peptides is capable of distin- Euclid Ave., Saint Louis, MO 93110. Phone: (314) 362-8873. Fax: (314)362-3203. E-mail: sibley@borcim.wustl.edu.
guishing type II strains from non-type II (typically I or III) strains and offers the promise for determining the frequency of homogenized and inoculated into another pair of mice that were then examined strain types that cause both acute and chronic infections.
for Toxoplasma-specific antibodies as described above.
Clinical samples. AF samples were obtained by amniopuncture under sono-
The presentation of congenital toxoplasmosis varies widely graphic guidance in the Department of Ultrasound, RIPMMH, Lodz, Poland.
from subclinical to severe cases, which may cause fetal or Additionally, in one case (number 18) fetal CSF was obtained when hydroceph- neonatal death (23). The frequency and severity of fetal toxo- alus was decompressed in utero by insertion of a ventriculoamniotic shunt (19).
plasmosis depends on the time when infection takes place In two cases (nos. 1 and 10), CSF samples were collected postnatally for geno- during pregnancy. Early in pregnancy, infections are less likely typing. One neonate (no. 1) was confirmed infected by positive B1 PCR fromCSF taken a few days after birth (Table 1). In another case (no. 10), CSF was to cross the placental barrier, yet those congenital infections available from the infant after long-term antiparasitic treatment. For three ne- that do result are more severe. While infection occurs more onates (nos. 16, 17, and 18), AF was not available and instead, neonatal blood readily late in pregnancy, the majority of such cases are mild or was used for typing. Negative controls consisted of AF or CSF samples from asymptomatic at birth (summarized in reference 23). High pregnancies with negative anti-T. gondii serology after delivery. Samples werecollected and stored at Ϫ20°C at the Department of Fetal-Maternal Medicine parasite concentrations in the amniotic fluid (AF) have been and Gynecology, Research Institute Polish Mother’s Memorial Hospital, Lodz, associated with severe outcome (24).
Poland and then sent frozen on dry ice to the Department of Microbiology, In the present study we examined a set of well-characterized Washington University School of Medicine, Saint Louis, MO.
cases of congenital toxoplasmosis from Poland. We deter- Experimental samples. T. gondii tachyzoites were cultivated by 2-day passage
mined the genotypes of T. gondii found in AF and cerebral in human foreskin fibroblast monolayers and purified from host cells as describedpreviously (14). Type strains consisted of RH (type I) (American Type Culture spinal fluid (CSF) from cases of congenital toxoplasmosis using Collection, Manassas, VA; ATCC 50174), PTG (type II) (ATCC 50841), and a newly developed multiplex nested-PCR typing system (16).
CTG (type III) (ATCC 50842). T. gondii cells were harvested, counted, and We also analyzed serological responses to strain-specific pep- resuspended in phosphate-buffered saline (PBS). Two types of standards were tides in order to serotype infections (17).
used for testing sensitivity. First, aliquots containing 1, 0.5, 2.5, 5, or 10 parasiteequivalents were made from a stock lysate of purified parasites prepared byincubation with 100 ␮g/ml proteinase K for 1 h at 37°C and 2 h at 50°C, followedby heat inactivation at 90°C for 15 min. Second, aliquots (10 ␮l) containing 5.0, MATERIALS AND METHODS
10.0, 25.0, 50.0, or 100.0 parasites were added to 1 ml of negative AF and Clinical cases of congenital toxoplasmosis. Nineteen cases of congenital toxo-
centrifuged at 3,000 ϫ g, and the pellet was used for analysis.
plasmosis diagnosed at the Research Institute Polish Mother’s Memorial Hospital Multiplex PCR genotyping. We utilized a recently described multiplex nested
(RIPMMH, Lodz, Poland) between March 1999 and June 2003 were included in the PCR for T. gondii genotyping based on four independent, unlinked markers: study. The following classification of clinical forms of congenital toxoplasmosis was 5Ј-SAG2, 3Ј-SAG2, SAG3, GRA6, and BTUB (16). In the first round of PCR, all used. Symptomatic toxoplasmosis was described when ventricular dilatation was reverse and forward external primers were combined in one reaction tube. The observed in repeated ultrasound scans and/or fetal and neonatal death was reported.
PCR mixture consisted of 5 ␮l of 10ϫ PCR buffer (Sigma, St. Louis, MO) Chorioretinitis was diagnosed during the neonatal period. Fetuses and/or neo- containing 1.5 mM of MgCl2; 4 ␮l of deoxynucleoside triphosphates (2.5 ␮M nates that did not present pathological symptoms were classified as asymptom- each) (Roche Applied Sciences, Indianapolis, IN); 0.15 ␮l of 50 ␮M of each atic. After birth, a team of specialists including neurologists and ophthalmolo- forward and reverse primer (Integrated DNA Technologies, Coralvile, IA); 0.5 gists attended symptomatic and asymptomatic neonates. Congenitally infected ␮l of (5 U/␮l) Taq DNA polymerase (Sigma); and 31.0 ␮l of distilled, DNase- infants were treated with combined therapy with pyrimethamine and sulfadia- and RNase-free water. PCR was conducted using a PTC-200 DNA engine system zine. The studies were conducted with approval of the Ethical Committee of Peltier thermal cycler (MJ Research Inc., Watertown, MA) programmed for 94°C for 30 seconds, 55°C for 60 seconds, and 72°C for 2 min during each of 35 Confirmation of congenital infection. Serological testing (anti-Toxoplasma
cycles. PCR products were digested with restriction enzymes (New England IgG, IgM, IgA, and IgG avidity) was performed in the Department of Microbi- BioLabs, Inc., Beverley, MA) and restriction fragment length polymorphisms ology, RIPMMH, Lodz (20a). Prior to March 2000, screening of maternal sera (RFLPs) were visualized using ethidium bromide staining of 2% agarose gels.
for Toxoplasma-specific IgG antibodies was performed with a latex agglutination Sample processing. Clinical samples of AF and CSF were centrifuged for 10 min
´rieux) (positive cutoff: 4 IU/ml), or an indirect at 3,000 ϫ g and pellets were extracted with a QIAamp DNA blood minikit agglutination assay (Platelia Toxo-G; Diagnostics Sanofi Pasteur) (positive cut- (QIAGEN Inc., Valencia, CA). Neonatal whole blood (200 ␮l) was processed off: Ͼ6 IU). Testing for Toxoplasma-specific IgM was conducted using an en- directly using the QIAamp DNA blood minikit. In the final step, samples were zyme-linked immunosorbent assay (ELISA) (Platelia Toxo M; Diagnostics eluted with 25 ␮l of buffer. Multiplex PCR was conducted using 12.5 ␮l of the eluted Sanofi Pateur). (cutoffs: 0 to 1 IU/ml, negative; 1 to 2 IU/ml, borderline; Ͼ2 samples as described above. Representative strains were used as positive controls.
IU/ml, positive). In cases where specific IgM was detected, an immunosorbent Negative AF and CSF samples and distilled water served as negative controls.
agglutination assay was used for detecting specific IgM and IgA (bioMe Serological typing. Strain-specific polymorphic peptides derived from the T.
(cutoffs: Ͻ6, negative; 6 to 7, borderline; Ͼ7, positive). In neonates, the Platelia gondii dense granule (GRA) proteins GRA6 and GRA7 were coupled to keyhole Toxo-M and Toxo-A tests were used with the same cutoff values as in the limpet hemocyanin as described previously (17). Within the abbreviated names mothers and the immunosorbent agglutination assay was used for IgM and IgA of the peptides, 6 denotes peptides from GRA6 and 7 those from GRA7; I/III or (cutoffs: Ͻ3, negative; 3 to 6, intermediate; Ͼ6, positive). IgG avidity was tested II indicates the allele of the peptide, i.e., from which archetypal strain it was using an ELISA (Labsystems) (cutoffs: low, Ͻ15%; borderline, 15 to 30%; high, derived; and indicates a truncated version of the diagnostic peptide. Coupled peptides were diluted to 2 ␮g/ml in 0.1 M carbonate buffer, pH 8.5, and 50 ␮l of Beginning in March 2000, Toxoplasma-specific IgG was detected in sera from each peptide solution was loaded into a polystyrene ELISA plate well overnight mothers and their neonates by enzyme-linked immunofluorescent assay (VIDAS at 4°C. Coated wells were blocked with 200 ␮l of a 2% casein solution in PBS for Toxo-IgG; bioMerieux) (positive cutoff: Ͼ8 IU/ml). Toxoplasma-specific IgM was detected using VIDAS Toxo-IgM (bioMerieux) (positive cutoff: Ͼ0.65 IU/ Sera were tested by adding 50 ␮l of diluted human serum (typically 1:100) to ml) and Toxoplasma-specific IgA was detected using the Platelia Toxo-IgA each well and incubating for 2 h at room temperature. ELISA plates were method as described above. IgG avidity was tested using the enzyme-linked washed four times with a PBS/0.1% Tween 20 solution before incubation with a immunofluorescent assay test (VIDAS Toxo-avidity; bioMerieux) (cutoffs: low, horseradish peroxidase-coupled monoclonal antibody against human IgG (BD Ͻ0.2; borderline, 0.2 to 0.3; high, Ͼ0.3).
Pharmingen, San Diego, CA) for 1 h at room temperature. Plates were washed PCR detection of parasite DNA was based on the B1 gene as described in PBS and developed with 150 ␮l of ABTS 2,2Ј-azinobis(3-ethylbenzthiazoline- previously (7). PCR assays and bioassay by inoculation of mice were conducted sulfonic acid) (ABTS) reagents (Kirkegaard and Perry Laboratories, Inc., Gaithers- in the Department of Medical Parasitology National Institute of Hygiene, War- burg, MD). Absorbance was read at 1, 2, and 4 h using a 405-nm filter. Two saw. For bioassay, 1 ml of AF or CSF was injected intraperitoneally into labo- control peptides served as negative controls to establish background reactivity for ratory mice (CFW/Pzh strain). Six weeks after inoculation, blood samples were normalization purposes. They consisted of a randomized sequence of the GRA6 examined with the Toxo-Screen DA test to detect seroconversion and establish peptide and a mix of peptides derived from the human and Leishmania EF1␣ the titer of Toxoplasma-specific IgG antibodies. The brains of these animals were proteins coupled to keyhole limpet hemocyanin.
TABLE 1. Clinical findings and genotype analysis in congenitally infected fetuses and infants with T. gondiia a Abbreviations: GW, gestational week; NP, neonatal period; IUD, intrauterine death; MI, mouse inoculation; NS, neonatal serology; pos., positive result; neg., negative; ND, not done; NT, nontypeable; NA, not available; NB, neonatal blood. Mothers’ serology results are given for the first available test. CSF was used for PCRor mouse inoculation in cases 1 and 18 and AF was used in the remaining cases. Uncertain refers to low values with all peptides, such that a strain type could not bereliably determined. Atypical refers to the reaction with peptides from different strain types, reflecting either mixed infection or possibly unusual genotypes. The testsused and their cutoff values are given in the text.
ELISA data for each infection serum were normalized by dividing the considered significant positive reactivity against the serotyping peptides, as optical density (OD) value obtained at each of the eight serotyping peptides defined previously (17). The four positive control sera utilized (two type II by the mean of the OD readings for the two control peptides. Negative and two type I/III) were from patients from whom parasites were recovered reactivity thus yields a theoretical value of ϳ1.0: values of 1.4 or greater are FIG. 1. Sensitivity of multiplex PCR analysis of T. gondii in AF (A) and CSF (B) samples. Multiplex PCR was performed for the four genetic markers SAG2 (5Ј and 3Ј amplified separately), SAG3, GRA6, and BTUB followed by electrophoresis in agarose gels containing ethidium bromide.
Lanes 1, 6, and 7 are negative controls, and lanes 2 to 5 are samples spiked with 0.5, 2.5, 5.0, and 10.0 T. gondii cells, respectively.
genital toxoplasmosis was confirmed by two of the followingcriteria: positive results by B1 PCR with AF or CSF; positive Sensitivity of multiplex PCR in amniotic fluid. To establish
serology in mice after inoculation of AF or CSF samples into the sensitivity of the multiplex PCR, 1-ml volumes of AF or CSF mice; and presence of specific IgM and/or IgA in the neonate samples from uninfected pregnancies were spiked with lysates of (Table 1). Four neonates were classified as congenitally in- T. gondii equivalent to 0.5 to 10 parasites per sample. Samples fected based solely on demonstration of specific IgG, IgM, were then directly processed for PCR. The sensitivity of detection and/or IgA antibodies in repeated tests following birth (Table ranged from 2.5 to 10 parasites per sample in both AF (Fig. 1A) 1). In the remaining case, only IgG was demonstrated, how- and CSF (Fig. 1B). In the primary round of multiplex PCR (leftside of Fig. 1), no amplification products were seen, consistent ever, it was included in the study based on inoculation of AF with the low input of parasites. In the second round, specific into naı¨ve mice and their subsequent positive serology (case products were detected for each marker (right side, Fig. 1). Dif- number 14). Ventricular dilatation (ventriculomegaly or hy- ferences in the sensitivity of detection of individual markers likely drocephalus) was detected prenatally in 11 cases (Table 1).
reflect efficiencies based on different PCR primers, since all of Five out of 11 symptomatic cases died, two in utero and three these targets are present as a single copy per genome.
in early postnatal periods. Chorioretinitis was diagnosed in We also tested the sensitivity of multiplex PCR under con- four neonates. Eight cases were asymptomatic.
ditions that more closely approximate sample processing. In For 14 of the cases, AF samples were used for detection of this instance, defined numbers of whole parasite cells were parasite DNA by multiplex PCR (Table 1). However, for sev- added to 1 ml of normal AF samples and centrifuged, and the eral cases, only CSF (numbers 1 and 10), or only neonatal pellet was extracted and analyzed. Under these conditions, the blood (numbers 16, 17, and 18) was available. PCR amplifica- sensitivity was approximately 25 parasites per sample (data not tion of T. gondii genetic markers was only successful in 9 out of shown). The decreased sensitivity under these conditions likely 19 samples; the remaining samples were negative in all tests reflects inefficiency in recovery of parasites following centrifu- (Tables 1 and 2). Eight of the nine cases that were positive gation and/or extraction. However, since these conditions were detected with AF samples and the remaining positive was more closely simulate processing of clinical AF samples, they likely reflect the real sensitivity of this method versus the more Gene-specific amplification products were subjected to re- efficient detection seen when small samples are spiked with striction enzyme digestion to identify characteristic RFLPs and the genotypes were determined based on the combination of Genotypes of T. gondii by multiplex PCR-RFLP analysis.
alleles at different markers (16). For eight of the nine samples, Nineteen cases of confirmed congenital toxoplasmosis were the genotype was determined to be type II for all four markers examined here, as summarized in Table 1. In 14 cases, con- (Table 2). A representative example is shown for 3Ј-SAG2 in TABLE 2. Genotypes of T. gondii in clinical samples from congenitally infected fetuses and newborns based on multiplex PCRa a Alleles are defined in reference 16. Genotype II is the result of allele 1 at 5Ј-SAG2 and allele 2 at 3Ј-SAG2.
b Neg, negative.
c Where sample type and volume are not specified for the case, the sample was 1 ml of AF.
Fig. 2. In one CSF sample (number 1), genotype II was deter- peptides to define the genotype of parasites causing infection, mined only for the 3Ј-SAG2 and GRA6 markers and the sam- as described previously (17). A total of 28 mother and infant ple was negative for the remaining markers (Table 2). Geno- sera from 15 different cases of congenital toxoplasmosis (two typing was not successful with the second CSF sample, were not available as paired samples) were provided to the suggesting a lower parasite concentration in CSF than in AF.
Toxoplasma Serology Laboratory (Palo Alto Medical Re- In all three severe cases that were not successfully genotyped, search Foundation) as a blinded set of samples without any late referral complicated proper sampling and this may have identifying information about strain genotype, clinical disease, or dye test titer prior to analysis. Sera were tested against a set Genotyping at the SAG1 locus and type X. The genotype at
of polymorphic peptides that have previously been shown to SAG1 was also examined using gene-specific PCR to distin- identify strain-specific antibodies present in patient serum guish between parasite type II and newly described type X (17). Reaction to these peptides can thus be used to genotype (18). RFLP analysis does not discriminate between type X and the strain responsible for infection.
type II strains at the markers (SAG2, SAG3, and GRA6) used Positive control sera (Table 3) established that the assay was here. However, type X can be distinguished from type II by the reproducible and working within the detection and cutoff limits presence of a type I RFLP pattern at SAG1 after digestion with as previously established by Kong and colleagues (17). The Sau961 (18). PCR-RFLP analysis of the nine clinical samples results show that 20 of 28 sera (representing 12 of 15 cases) studied here showed an RFLP pattern at SAG1 consistent with produced a reactivity pattern consistent with infection by type type II and distinct from type X (Table 2).
II strains (positive reaction with one or more type II peptides Serological typing of clinical samples. Sera from both the
designated 6II, 6 d-II, 7 II, and 7 d-II) (Table 3). Two sera mother and infant were tested for reaction to allele-specific (maternal sera from cases 2 and 14 in Table 1) gave no clearindication of the type responsible for infection, as reactivityagainst all peptides was weak. However, in both cases, serafrom the infant showed reactivity to at least one type II pep-tide. These results for maternal and infant sera were consis-tently observed in repeated assays.
IgG antibodies detected in neonatal sera are almost cer- tainly derived from transfer of maternal antibodies. Thus, thenegative results for the mothers of these infants is likely due todegradation of the sample during storage. Paired maternal andinfant sera from case number 13 reacted weakly with the 6d-I/III peptide but none of the other I/III diagnostic peptides.
All type I/III infection sera previously characterized haveshown strong reactivity with peptide 6 I/III, so lack of reactivity FIG. 2. RFLP analysis of PCR products amplified from AF and with this peptide precludes assigning these two sera. Paired CSF samples from cases of congenital toxoplasmosis. 3Ј-SAG2 ampli- maternal and infant sera from case 15 and case 17 reacted fication products digested with HhaI were resolved in 3% agarose gelsstained with ethidium bromide. The samples loaded in lanes I, II, and strongly with both type II and type I/III peptides, suggesting a III are representative of T. gondii strain types I, II, and III, respectively.
possible mixed infection. Mixed infections are highly unusual, Samples from pregnancies with congenitally infected fetuses were and thus their reactivity is listed as atypical. Based on the loaded in lanes 1 to 9. Genotyping revealed all nine positive samples serological testing, it was concluded that 12 of the 19 cases of were type II strains of T. gondii. AF samples from uninfected pregnantwomen (neg) served as negative controls.
congenital toxoplasmosis were due to type II strains.
TABLE 3. Serological analysis of paired mother-infant samples with strain-specific peptidesa a Peptides utilized in testing are listed across the top of the table. The negative control value is the mean for two negative peptides (see text). Positive controls were provided by patient sera from previously typed cases of toxoplasmosis (see text). Results are shown for sera from the cases listed in Table 1. Sera were reacted againstthe panel of eight strain-specific peptides to identify allele-specific antibodies present in infection serum. All data were normalized by dividing the A405 reading for eachserotyping peptide against the mean of the two control peptides. Values of Ͼ1.4 were considered significant (17). Uncertain refers to low values with all peptides, suchthat a strain type could not be reliably determined. Atypical refers to reaction with peptides from different strain types, reflecting either mixed infection or possiblyunusual genotypes.
DISCUSSION
T. gondii has a highly clonal population structure and most human infections are caused by one of three main genotypes.
We used multiplex PCR to genotype strains of T. gondii directly in AF and CSF samples from complicated congenital Type II strains cause the majority (70 to 80%) of human cases infections in Poland. We found exclusively type II strains of T. of toxoplasmosis reported previously from North America and gondii and eight of nine typeable cases represented severe Europe (primarily France) (1, 5, 12–14). Type I is infrequent in cases of toxoplasmosis. Serological typing was consistent with nature, but has been shown to be more common both in con- type II genotypes causing the majority of symptomatic and genital toxoplasmosis (6) and in AIDS patients (14). Type III asymptomatic infections. Our findings indicate that type II strains are largely found in animals and only rarely cause hu- strains can cause both benign and complicated cases and are man infection for reasons that are unknown (14).
consistent with the hypothesis that the severity of infection is In the present study, all of the cases typeable by nested PCR primarily related to the burden of parasites.
were type II, and eight of nine positives were obtained from severe cases. Five cases resulted in death in utero or early in testing, which also identified five additional cases of type II the neonatal period. A total of 14 of 19 cases studied in the infections that were only typeable by serology. The failure to present report were found to be due to type II strains, based on detect type I/III samples among these samples is not due to genotyping and/or serological typing. The samples studied here assay bias, since both PCR-based and serological typing per- come from a referral hospital that receives patients with com- form well with standards that included samples from patients plicated pregnancies from a wide area of Poland. Thus, our with infections of known genotypes in the case of serology studies provide a baseline for further analysis of congenital cases of toxoplasmosis in Poland to determine if this pattern of Severe symptoms of congenital toxoplasmosis occur type II infections is widespread. Ajzenberg et al. also described mostly as a result of infections that occur early in pregnancy.
type II in eight out of eight cases of fetal or newborn death and Results of real-time PCR showed that severe outcome was in a majority (73 of 86 samples) of all congenital cases studied associated with high parasite load and the highest parasite from France (1). In contrast to these findings, a study from concentrations were found when seroconversion occurred Spain based on single-locus PCR-RFLP analysis reported that early in pregnancy (24). In our study, the timing of the non-type II strains were found in 12 of 13 congenital infections mother’s primary infection was uncertain due to the lack of (6). This difference may be primarily related to geography, serological monitoring. However, all of the mothers had since any referral bias for severe cases would appear to be the serological results suggesting primary infection during the same in both studies. Collectively, these results indicate mul- first or second trimester of pregnancy (IgM and/or IgA tiple strain types can be associated with severe toxoplasmosis and/or low IgG avidity). In Poland, serological screening in pregnancy is not routinely performed, although anti-T. gon- Clinical forms of congenital toxoplasmosis vary widely. Only dii testing is recommended. Routine ultrasound screening 5 to 10% of all infected fetuses develop serious disease, and the during pregnancy is well established in Poland.
majority of infections are asymptomatic (23). Chorioretinitis In our study, detection of symptoms in a fetus was typically can result from both congenital and acquired infection (11).
followed by prenatal diagnosis of congenital toxoplasmosis.
Human ocular toxoplasmosis is associated with different The prevalence of T. gondii (41.3% seropositive) in pregnant strains, including strains containing a mixture of type I and women in Poland is high (20, 20a), and screening of cord blood type III genotypes (9). Chorioretinitis was diagnosed in four from neonates, which per se does not detect all congenitally neonates presented in our study, all due to type II infections.
infected cases, indicates a frequency of infection of ϳ1 in 1,000 Recently, Miller et al. described T. gondii genotype X that was to 2,000 live births (21, 22). Most of these cases are likely not associated with brain lesions and mortality in sea otters in the severe, and the high rate of fetal defects among the cases western United States (18). Our samples from cases with se- studied here is mainly due to the referral of complicated preg- vere clinical signs of the disease (hydrocephalus and fetal/ nancies to RIPMMH, suggesting that the majority of asymp- neonatal death) were found to match the type II, not the type tomatic cases are not detected. Elective interruption of preg- nancies in Poland is very rare, so the emphasis is placed on Semiquantitative PCR with the B1 gene has been used pre- possible treatment in utero and postnatally (19).
viously to estimate the parasite burden in AF during congenital Strain type has been suggested to play a role in determining infection (10, 24). The parasite load estimated using real-time the outcome of T. gondii infection (3). In our study, T. gondii PCR was less then 10 parasites/ml in 40 to 46% of AF samples type II was identified in eight AF and one CSF sample from and 11 to 100 parasites/ml in 30 to 40% of samples (4, 24) Polish fetuses and neonates with severe forms of disease. Im- Previous studies using real-time PCR in AF established the portantly, for all samples for which PCR genotype data were relationship between high parasite burden and severity of dis- available, the serotyping assay accurately predicted infection ease (24). PCR detection with B1 is more sensitive than the by a type II strain (Tables 2 and 3). While most asymptomatic methods used here; however, it is not sufficiently polymorphic cases were generally not typeable by PCR, serological analysis to allow simple RFLP typing of alleles. For these reasons, we indicated a majority of these were also type II. The reaction developed nested PCR-RFLP typing of several single-copy between mothers and infants was highly correlated, likely re- genes that are polymorphic (16). While these markers are well flecting the fact that this assay detects IgG that is acquired by suited for typing, they are less sensitive overall than detection the infant by transfer across the placental barrier in utero.
Serum from several cases (13 and 15) reacted to peptides of In our study, the sensitivity of parasite detection by multiplex both type II and I/III, raising the possibility that these patients nested PCR was Ն25 parasites/ml in AF and CSF. Thus, the were multiply infected either with a mix of different strains or negative status of many of our samples may have resulted from by a novel strain(s) that possesses alleles at GRA6 and GRA7 small amounts of parasite DNA in these samples. Consistent that induce antibodies that react to peptides of both alleles.
with this, most of those strains that were typeable by PCR (Ͼ25 Interpretation of these sera would require parasite genotype parasites/ml) were from severe cases. These findings are con- information, but unfortunately, insufficient parasite DNA was sistent with an association between parasite burden and dis- recovered from these patients to allow PCR-RFLP genotyping.
ease association established previously by more quantitative Our findings demonstrate that type II strains can be associated methods (10, 24). The failure to type some cases by nested with either mild and severe disease and support the hypothesis PCR-RFLP analyses also raises the possibility that the present that high parasite concentration is primarily responsible for the samples have an inherent bias. However, our conclusion that severity of congenital disease. They also demonstrate a close type II strains cause the majority of infections in this sample concordance of parasite genotyping by PCR-based genetic mark- group is supported by similar results obtained by serological ers and serological testing using strain-specific epitopes. Ex- panded use of serological typing should enable more comprehen- 14. Howe, D. K., and L. D. Sibley. 1995. Toxoplasma gondii comprises three
sive analysis of the contribution of parasite genotype to clinical clonal lineages: correlation of parasite genotype with human disease. J. In-
fect. Dis. 172:1561–1566.
15. Joynson, D. H., and T. J. Wreghitt. 2001. Toxoplasmosis: a comprehensive
clinical guide. Cambridge University Press, Cambridge, England.
ACKNOWLEDGMENTS
16. Khan, A., C. Su, M. German, G. A. Storch, D. Clifford, and L. D. Sibley.
2005. Genotyping of Toxoplasma gondii strains from immunocompromised D.N. was supported by a Fulbright Senior Fellowship Grant. This work patients reveals high prevalence of type I strains. J. Clin. Microbiol. 43:5881–
was also partially supported by an NIH grant to L.D.S. (AI059176).
We thank Tadeusz H. Dzbenski for PCR testing and mouse inocu- 17. Kong, J. T., M. E. Grigg, L. Uyetake, S. F. Parmley, and J. C. Boothroyd.
lation studies conducted in the Department of Medical Parasitology, 2003. Serotyping of Toxoplasma gondii infections in humans using synthetic National Institute of Hygiene, in Warsaw, Poland, Asis Khan for tech- peptides. J. Infect. Dis. 187:1484–1495.
nical advice, and Julie Suetterlin and Dorota Stodolnik for technical 18. Miller, M. A., M. E. Grigg, C. Kreuder, E. R. James, A. C. Melli, P. R.
Crosbie, D. A. Jessup, J. C. Boothroyd, D. Brownstein, and P. A. Conrad.
2004. An unusual genotype of Toxoplasma gondii is common in California
REFERENCES
sea otters (Enhydra lutris nereis) and is a cause of mortality. Int. J. Parasitol.
1. Ajzenberg, D., N. Cogne´, L. Paris, M. H. Bessieres, P. Thulliez, D. Fillisetti,
34:275–284.
H. Pelloux, P. Marty, and M. L. Darde
´. 2002. Genotype of 86 Toxoplasma
19. Nowakowska, D., M. Respondek-Liberska, E. Golab, B. Stray-Pedersen, K.
gondii isolates associated with human congenital toxoplasmosis and correla- Szaflik, T. H. Dzbenski, and J. Wilczynski. 2005. Too late prenatal diagnosis
tion with clinical findings. J. Infect. Dis. 186:684–689.
of fetal toxoplasmosis: a case report. Fetal Diagn. Ther. 29:190–193.
2. Barragan, A., and L. D. Sibley. 2002. Transepithelial migration of Toxo-
20. Nowakowska, D., M. Slaska, E. Kostrzewska, and J. Wilczynski. 2001. Anti-
plasma gondii is linked to parasite motility and virulence. J. Exp. Med.
Toxoplasma gondii antibody concentration in sera of pregnant women in the 195:1625–1633.
´dz population. Wiad. Parazytol. 47(Suppl. 1):83–89.
3. Boothroyd, J. C., and M. E. Grigg. 2002. Population biology of Toxoplasma
20a.Nowakowska, D., B. Stray-Pedersen, E. Spiewak, W. Sobala, E. Malafiej, and
gondii and its relevance to human infection: do different strains cause dif- J. Wilczyski. Prevalence and estimated incidence of Toxoplasma infection
ferent disease? Curr. Opin. Microbiol. 5:438–442.
among pregnant women in Poland: a decreasing trend in the younger pop- 4. Costa, J. M., P. Ernault, E. Gautier, and S. Bretagne. 2001. Prenatal diagnosis
ulation. Clin. Microbiol. Infect., in press.
of congenital toxoplasmosis by duplex real-time PCR using fluorescence reso- 21. Paul, M., E. Petersen, Z. S. Pawlowski, and J. Szczapa. 2000. Neonatal
nance energy transfer hybridization probes. Prenat. Diagn. 21:85–88.
screening for congenital toxoplasmosis in the Poznan region of Poland by 5. Darde´, M. L., B. Bouteille, and M. Pestre-Alexandre. 1992. Isoenzyme anal-
analysis of Toxoplasma gondii-specific IgM antibodies eluted from filter pa- ysis of 35 Toxoplasma gondii isolates and the biological and epidemiological per blood spots. Pediatr. Infect. Dis. 19:30–36.
implications. J. Parasitol. 78:786–794.
22. Paul, M., E. Petersen, and J. Szczapa. 2001. Prevalence of congenital Toxo-
6. Fuentes, I., J. M. Rubio, C. Ramı´rez, and J. Alvar. 2001. Genotypic charac-
plasma gondii infection among newborns from the Poznan region of Poland: terization of Toxoplasma gondii strains associated with human toxoplasmosis validation of a new combined enzyme immunoassay for Toxoplasma gondii- in Spain: direct analysis from clinical samples. J. Clin. Microbiol. 39:1566–
specific immunoglobulin A and immunoglobulin M antibodies. J. Clin. Mi- crobiol. 39:1912–1916.
7. Golab, E. 1995. Detection of Toxoplasma gondii DNA in body fluids by
23. Remington, J. S., R. McLeod, P. Thulliez, and G. Desmonts. 2001. Toxo-
polymerase chain reaction. Wiad. Parazytol. 41:13–18.
plasmosis, p. 205–346. In J. S. Remington and J. O. Klein (ed.), Infectious 8. Grigg, M. E., S. Bonnefoy, A. B. Hehl, Y. Suzuki, and J. C. Boothroyd. 2001.
diseases of the fetus and newborn infant, 5th ed. W. B. Saunders Company, Success and virulence in Toxoplasma as the result of sexual recombination between two distinct ancestries. Science 294:161–165.
24. Romand, S., M. Chosson, J. Franck, M. Wallon, F. Kieffer, K. Kaiser, H.
Grigg, M. E., J. Ganatra, J. C. Boothroyd, and T. P. Margolis. 2001. Unusual
abundance of atypical strains associated with human ocular toxoplasmosis.
Dumon, F. Peyron, P. Thulliez, and S. Picot. 2004. Usefulness of quantitative
polymerase chain reaction in amniotic fluid as early prognostic marker of 184:633–639.
10. Hohlfeld, P., F. Daffos, J. Costa, P. Thulliez, F. Forestier, and M. Vidaud.
fetal infection with Toxoplasma gondii. Am. J. Obstet. Gynecol. 190:797–802.
1994. Prenatal diagnosis of congenital toxoplasmosis with a polymerase- 25. Sibley, L. D. 2003. Recent origins among ancient parasites. Vet. Parasitol.
chain-reaction test on amniotic fluid. N. Engl. J. Med. 331:695–699.
115:185–198.
11. Holland, G. N. 1999. Reconsidering the pathogenesis of ocular toxoplasmo-
26. Sibley, L. D., and J. C. Boothroyd. 1992. Virulent strains of Toxoplasma
sis. Am. J. Ophthalmol. 128:502–505.
gondii comprise a single clonal lineage. Nature (London) 359:82–85.
12. Honore´, S., A. Couvelard, Y. J. Garin, C. Bedel, D. He´nin, M. L. Darde´, and
27. Su, C., D. Evans, R. H. Cole, J. C. Kissinger, J. W. Ajioka, and L. D. Sibley.
F. Derouin. 2000. Genotyping of Toxoplasma gondii strains from immuno-
2003. Recent expansion of Toxoplasma through enhanced oral transmission.
compromised patients. Pathol. Biol. (Paris) 48:541–547.
Science 299:414–416.
13. Howe, D. K., S. Honore´, F. Derouin, and L. D. Sibley. 1997. Determination
28. Su, C., D. K. Howe, J. P. Dubey, J. W. Ajioka, and L. D. Sibley. 2002.
of genotypes of Toxoplasma gondii strains isolated from patients with toxo- Identification of quantitative trait loci controlling acute virulence in Toxo- plasmosis. J. Clin. Microbiol. 35:1411–1414.
plasma gondii. Proc. Natl. Acad. Sci. USA 99:10753–10758.

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