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1055
Congenital Toxoplasmosis Transmitted from an Immunologically Competent
Mother Infected Before Conception
Nicolas Vogel, Michael Kirisits, Eric Michael,
Howard Bach, Margaret Hostetter, Kenneth Boyer,
Ross Simpson, Ellen Holfels, Joyce Hopkins,
Douglas Mack, Marilyn B. Mets, Charles N. Swisher,
Dushyant Patel, Nancy Roizen, Laszlo Stein, Mark Stein,
Shawn Withers, Ernest Mui, Charles Egwuagu,
Jack Remington, Ronald Dorfman, and Rima McLeod
From Michael Reese Hospital, The University of Illinois, Rush Medical
School, The University of Chicago, Illinois Institute of Technology,
Northwestern Children's Hospital, and Northwestern University,
Chicago, Illinois; The University of Minnesota and Methodist Hospital,
Minneapolis, Minnesota; Stanford University, Stanford, California; and
National Eye Institute, National Institutes of Health, Bethesda, Maryland
Congenital transmission of Toxoplasma gondii from a mother who was apparently immunologically competent and who had toxoplasmic lymphadenitis 2 months before conception is described.
Since no T. gondii—specific serological data were available for this mother from the time her lymph
node biopsy specimen was obtained, the specimen was studied by polymerase chain reaction (PCR)
to determine whether the T. gondii B1 gene was present. The predictive diagnostic value of histologic
findings previously considered to be classic signs of T. gondii lymphadenitis also was studied. This
was done by correlation of serological tests diagnostic of acute acquired T. gondii infection and
presence of characteristic findings in biopsy specimens from persons without known immunocompromise. Both PCR and review of the characteristic features of her lymph node biopsy specimen
confirmed the diagnosis of preconceptual infection in the mother. We also discuss two other cases
in which apparently immunologically competent mothers with preconceptually acquired infection
transmitted this parasite to their fetuses.
The risk of in utero transmission of Toxoplasma gondii from
an immunocompetent mother to her fetus has been considered
to be negligible when maternal toxoplasmic lymphadenopathy
is present before conception [1, p. 153; 2, 3]. We report a case
of congenital toxoplasmosis following maternal toxoplasmic
lymphadenitis that was diagnosed 2 months before conception.
In the absence of a retained serum sample from the time of
the mother's initial presentation, preconceptual infection was
unequivocally documented by the histologic appearance of the
mother's lymph node and by PCR amplification of the T. gondii
B1 gene in this original lymph node biopsy.
We also studied the correlation of the classic histologic triad
of toxoplasmic lymphadenopathy with serological evidence of
acute acquired toxoplasma infection in individuals without
known immunocompromise. We then reviewed the other two
case reports that describe transmission of T. gondii to the fetus
from an apparently immunologically competent mother who
was infected before conception.
Received 23 April 1996; revised 17 June 1996.
Financial support: This work was supported by grants NIH NIAID AI 27530
and NIH AI 108749, the Research to Prevent Blindness (RPB) Foundation
(Rima McLeod is the Jules and Doris Stein RPB Professor at the University
of Chicago), and the Pillsbury Postdoctoral Scholar Award to Nicolas Vogel.
Reprints or correspondence: Dr. Rima McLeod, Department of Medicine,
114 Baumgarten, Michael Reese Hospital, 2929 South Ellis, Chicago, Illinois
60616.
Clinical Infectious Diseases 1996; 23:1055-60
© 1996 by The University of Chicago. All rights reserved.
1058-4838/96/2305 — 0017$02.00
Case Reports
The mother underwent a lymph node biopsy 6 weeks before
conception. The primary care pathologist noted changes indicative of toxoplasmic lymphadenopathy. Retrospectively, 1 1/2
years later, this biopsy specimen was reviewed by one of us
(R. D.), who confirmed that it demonstrated the classic findings
of toxoplasmic lymphadenopathy. It had the classic triad of
histologic features noted in initial observations of the disease
[4]: reactive follicular hyperplasia, clusters of epithelioid histiocytes encroaching on germinal centers, and focal distention of
trabecular sinuses by monocytoid cells (figure 1).
No T. gondii organisms were seen in the lymph node biopsy
specimen with use of conventional histologic stains. No serological tests for T. gondii—specific antibody were performed
at the time of the biopsy, and no sera were available from that
time for retrospective analysis. No serological follow-up for
T. gondii infection was performed • during pregnancy, and no
antiparasitic therapy was given.
The pregnancy was uneventful until premature rupture of
membranes occurred at 35 weeks' gestation and resulted in
delivery of a 2.5-kg infant girl on 24 April 1991. Her Apgar
scores were 9 at 1 minute and 10 at 5 minutes. Findings of the
physical examination were normal for gestational age.
The infant had a peripheral blood hemoglobin level
of 17.7 g/dL, a hematocrit of 52.7%, and a WBC count of
24,600/mm 3 , with 51% granulocytes, 10% bands, 2% metamyelocytes, 10% monocytes, 19% lymphocytes, and 7% eosinophils. Her platelet count was 299,000/mm 3 . Other laboratory
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Vogel et al.
CID 1996;23 (November)
Figure 1. Histologic appearance of the lymph node biopsy specimen from the mother described herein. Left, monocytoid cells (single arrow)
and histiocytic aggregates (double arrows) outside the follicle are evident (original magnification, X 54). Right, aggregates of histiocytes
(arrow) are evident in the interfollicular area as well as at the edge of and within the follicle (original magnification, X 140).
values were a serum total bilirubin level of 10.3 mg/dL and a
glucose concentration of 22 mg/dL. The serum direct bilirubin
concentration was not determined.
Because the amniotic fluid was turbid, ampicillin and gentamicin were administered for 2 days pending results of bacterial
blood cultures, which were negative. Her total serum bilirubin
concentration was highest (11 mg/dL) on day 3 of life, and
she was treated with phototherapy. Otherwise, her perinatal
course was unremarkable.
Initially, the infant's development was normal. However, at 9
months of age her head growth was noted to be excessive, and
a CT scan of the brain was obtained on 30 January 1992. It
demonstrated obstructive hydrocephalus with marked dilatation
of the lateral and third ventricles (figure 2). The left lateral ventricle was larger than the right, and the temporal horns were asymmetric as well. The third ventricle had a tapered posterior segment,
indicative of acqueductal obstruction. The fourth ventricle was of
normal size. Small calcifications were present in the subependymal regions of both lateral ventricles and within the parenchyma
of the left temporal and parietal regions and right frontal lobe.
No abnormal contrast enhancement was noted.
A ventriculoperitoneal shunt was placed on 12 February
1992 (at 10 months of age) without incident. Follow-up CT
studies of the brain were performed on 14 February and 12
May 1992 (figure 2). They documented a progressive decrease
in the size of the lateral and third ventricles and an increase
in the width of the cortical mantle, indicating a functional
ventricular shunt. Calcifications were unchanged. Again, no
abnormal contrast enhancement was seen. At 12 months of
age, CSF obtained from the shunt had 10 WBCs (58% monocytes and 42% lymphocytes), and culture for bacteria yielded
no growth.
Figure 2. CT scans of the child's brain at
10 months of age (left; before shunt placement) and 12 months of age (right; after shunt
placement) demonstrate the initial hydrocephalus secondary to acqueductal obstruction and the good response to shunt placement, respectively.
CID 1996;23 (November)
Preconceptual Infection Can Transmit T gondii
Evaluation at 14 months of age demonstrated normal growth
as well as normal development and cognitive function, as measured with the Bayley Scale of Infant Development. Hearing,
tested by auditory brain-stem response, was normal at 20 decibels. Indirect ophthalmoscopy revealed a 2-disk-diameter quiescent scar in the periphery of the left retina.
Serological test results for the mother at this time were as
follows: Sabin-Feldman dye test, 1:2,048; IgM immunosorbent
agglutination assay (ISAGA), 3; IgM ELISA, 1.5; and differential agglutination (AC/HS) test, 400/3,200; those for the infant
were Sabin-Feldman dye test, 1:1024; IgM ELISA, 0.4; IgM
ISAGA, 3; and IgA ELISA, 1.1. All these values were indicative of remote (i.e., >6 months earlier) acquisition of infection.
The dye test [5], IgM ELISA [6, 7], IgM ISAGA [8],
AC/HS test [9, 10], and IgA ELISA [11] were performed in
Dr. Remington's laboratory.
In assays performed in Dr. Remington's laboratory for older
children and adults, an IgM ELISA is considered positive if
the resulting value is >2.0, negative if < 1.4, and equivocal if
1.5-1.9. For infants <6 months of age, it is considered positive
if the value is a0.2 and negative if <0.2. An IgM ISAGA for
an adult is considered negative if the resulting value is <5,
equivocal if 6-9, and positive if 10-12; for an infant the assay
is considered negative if the value is <2, equivocal if 3-7,
and positive if n 8. An IgA ELISA for an adult is considered
positive if the resulting value is > 1.4 and negative if < 1.3;
the assay is positive for infants if the value is >1.0.
The AC/HS test and guidelines for its interpretation are described in detail in Danneman et al. [9]. In brief, this test
compares agglutination titers of serum incubated with acetone
or methanol-fixed tachyzoites (AC antigen) with agglutination
titers of the same serum incubated with formalin-fixed tachyzoites (HS antigen). The AC antigen preparation differentiates
antibodies found early in infection from those that are present
later. As a generalization, an AC/HS test result that is usually
indicative of recently acquired infection in an immunologically
competent adult is an AC titer of _^-100 IU/mL that is greater
than, equal to, or at least one-quarter of the HS titer.
The mother was in good health, was seronegative for HIV
infection, and had no signs of vasculitis or any other illness,
either clinically or serologically.
Detection of the T. gondii B1 Gene in Toxoplasmic
Lymphadenopathy
PCR procedures were used to detect the B1 gene, which is
repeated 35-fold within the genome of each T. gondii organism.
DNA was extracted as previously described [12] from formalinfixed, paraffin-embedded sections of the mother's lymph node.
For controls, DNA was also extracted from paraffin-embedded
sections of formalin-fixed brain from uninfected and T. gondiiinfected mice.
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Primers (5'-GGAACTGCATCCGTTCATGAG-3' and 5'TCTTTAAGCGTTCGTGGTC-3') specific for the B1 gene
were used as previously described by Burg et al. [13] to determine whether T. gondii DNA was present. Each DNA sample
was amplified in a 50-4 mixture containing 1.25 units of Taq
DNA polymerase (Promega, Madison, WI); 2.5 mM MgC1 2 ;
10 mM Tris-HC1 (pH, 9.0); 50 mM KC1; 0.1% triton X-100;
0.2 mM each of deoxyguanosine triphosphate, deoxyadenosine
triphosphate, deoxythymidine triphosphate, and deoxycytidine
triphosphate; and 2.5 pmol of each B1 oligonucleotide primer.
The following conditions were used for PCR amplification: 3
minutes at 95°C prior to 40 cycles, each consisting of 15 seconds at 94°C, 15 seconds at 55°C, and 30 seconds at 72°C;
after 40 cycles, a final extension step was carried out for 7
minutes at 72°C. PCR was performed using a Perkin Elmer
9600 thermocycler (Perkin Elmer, Norwalk, CT).
Product from the PCR amplification reaction was analyzed
with EC1 3' oligolabeling and detection systems (Amersham,
Arlington Heights, IL) after electrophoresis on a 1.8% agarose
gel and transfer to a nylon membrane (Hybond-N+, Amersham) by the Southern [14] protocol. The membrane was
hybridized at 42°C with a fluorescein-labeled oligonucleotide
(5'-GGCGACCAATCTGCGAATACACC-3') that is complementary to a portion of the B1 gene within the amplified segment. The membrane was washed twice in high salt (5 X standard sodium citrate and 0.1% SDS) at 55°C, for 15 minutes
each time. The membrane was then incubated, with exposure
to a horseradish peroxidase—conjugated antibody to fluorescein, on hyperfilm-EC1 (Amersham) at room temperature.
Presence of the T. gondii B1 gene in the DNA sample extracted from the lymph node of the mother of the congenitally
infected infant was demonstrated. DNA encoding the B1 gene
of T. gondii was also detected in the infected mouse brain but
not in the DNA sample derived from sections of the uninfected
mouse brain (figure 3).
Correlation of the Classic Histologic Triad of
Toxoplasmic Lymphadenopathy and Serological Evidence
of Acute Acquired Toxoplasma Infection
In addition, we further characterized the ability of the classic
triad of histopathologic findings [4], as noted in our patient, to
establish the diagnosis of acute acquired toxoplasmic lymphadenopathy in persons without known immunocompromise.
Absolute correlation was noted between the histopathologic
findings attributed to acute toxoplasmic lymphadenitis and a
serological diagnosis of acute, recently acquired infection in
104 cases of toxoplasmic lymphadenitis involving persons
without known immunocompromise (table 1) (P < .001;
N. Vogel, J. S. Remington, R. Dorfman, and R. McLeod, personal observations regarding lymph node biopsy specimens
obtained between 1981 and 1993 from 72 patients and 31
lymph node biopsy specimens from patients described in [4]).
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CID 1996; 23 (November)
Vogel et al.
Figure 3. Southern blotting to detect the T. gondii B1 gene was
performed with use of genomic DNA extracted from formalin-fixed,
paraffin-embedded tissue or purified T. gondii parasites. Samples were
as follows: lane 1, DNA from T. gondii tachyzoites; lane 2, DNA
from the brain of a mouse chronically infected with the Me49 strain
of T. gondii; lane 3, DNA from the brain of a noninfected mouse;
and lane 4, DNA from a biopsied lymph node of the adult patient
(mother) described in the case report. Lanes 1, 2, and 4 contained
DNA that hybridized with labeled probe for the B1 gene.
This absolute concordance between the lymph node biopsy
histologic patterns and the patients' serological test results in
our laboratories (R. D., J. S. R.) provides strong additional
evidence to support the diagnosis of preconceptual acute toxoplasmosis in the mother we have described, whose lymph node
biopsy findings were so characteristic.
Discussion
Seroprevalence studies demonstrate that infection with
T. gondii occurs worldwide and that the incidence of seroposi-
tivity in all populations increases with advancing age. Although
infection is widespread, significant clinical disease occurs primarily in immunocompromised patients, as the result of reactivation of latent T. gondii, or in congenitally infected infants, in
whom infection develops following the occurrence of primary
maternal toxoplasmosis during gestation.
Transplacental infection of the fetus occurs in —12% of
cases in which the mother acquires infection during the first
trimester, and the incidence of transmission increases thereafter, to >90% when maternal infection occurs during the
last few weeks before delivery. Infection of the fetus early in
gestation usually results in severe involvement, and infection
late in gestation usually results in milder disease. Thus, congenital infection acquired late in gestation often is undiagnosed in
the neonatal period and more often presents with chorioretinitis
later in childhood or in adolescence.
During acute primary maternal toxoplasmosis, fetal infection
occurs as a result of maternal parasitemia and infection of the
placenta. From this nidus, infection of the fetus occurs by
transplacental passage after a variable delay or during delivery.
Although parasitemia may be persistent in immunocompromised patients, it appears usually to be relatively short-lived
in immunocompetent persons.
In a prospective study [1, p. 147], 50 pregnant women who
had recently seroconverted were not found to be parasitemic.
Findings were similar for 30 patients presenting with toxoplas-
mic lymphadenopathy [1, p. 147]. In one series, —10% of
mothers of infants with congenital toxoplasmosis had
lymphadenopathy [1]. These observations suggest that immunity to T. gondii in an immunocompetent person, with or without lymphadenopathy, is capable of rapidly containing parasitemia. Alternatively, the methods for detection of parasitemia
may have been insufficiently sensitive to document parasitemia.
PCR gene amplification is a sensitive and rapid method for
diagnosis of toxoplasma infection [12, 13, 15, 16]. Although
amplification of the T. gondii B1 gene is sensitive in demonstrating toxoplasmic retinitis, encephalitis, and myocarditis [15],
it was reported to have low diagnostic sensitivity for diagnosis
of toxoplasmic lymphadenitis [15, 17]: the B1 gene was detected in only 1 of 10 cryopreserved [15] and only 1 of 7
paraffin-embedded [17] lymph node specimens with classic
histologic features of toxoplasmic lymphadenitis.
It was possible, however, to detect the B1 gene product in
preserved samples from the mother's lymph node biopsy in
our case. These findings therefore definitely establish that her
infection was acquired before conception.
There are a number of possible reasons for the variable
diagnostic sensitivity of B1 gene amplification for detection of
the T. gondii genome in cases of toxoplasmic lymphadenitis.
Infection may be focal within the lymph node, or parasites may
be eliminated from the infected node by the time lymphadenitis
is clinically detected. Alternatively, lymphadenitis could be a
response to parasite antigen in other anatomic compartments
and not due to direct infection of the lymph node with T. gondii.
Furthermore, it is also possible that fixation and processing of
tissue could alter the sensitivity of the PCR assay.
The diagnosis of preconceptual toxoplasmosis in the patient
we describe was based on histopathology of a lymph node biopsy
Table 1. Correlation of serological test results (indicative of acute
acquired primary T. gondii infection) and findings of lymph node
biopsies (including features characteristic of lymphadenopathic toxoplasmosis) for persons without known immunocompromising illness.
No. of lymph-node biopsy specimens
with indicated features, as interpreted by
Dr. Dorfman's group*
Serology indicative of:
Acute T. gondii infection
No T. gondii infection
Characteristic
Not characteristic
72
0
0
4
* These lymph node biopsy specimens were submitted to Dr. Dorfman's
investigative group for review between 1981 and 1993 for consideration of a
diagnosis of lymphadenopathic toxoplasmosis. Lymph node biospy specimens
from persons known to be immunocompromised (e.g., by AIDS or malignancy)
were not included in the analysis. Characteristic features of lymphadenopathic
toxoplasmosis include clusters of epithelioid histiocytes that encroach on germinal centers, monocytoid cells that distend trabecular sinuses, and follicular
hyperplasia. Serological test results indicative of acute acquired toxoplasmosis
are summarized in the text.
CID 1996;23 (November)
Preconceptual Infection Can Transmit T gondii
specimen prior to subsequent confirmation by PCR. The classic
histopathologic triad found in cases of toxoplasmic lymphadenitis
has been felt to be highly suggestive of the diagnosis [4]. Our
present results confirm and extend this initial observation, made
by Dorfman and Remington in 1973 on the basis of 31 cases [4].
Our 72 additional cases (table 1) bring the total to 104, and
data from them indicate that the correlation between this classic
histology and serological diagnosis of infection with T gondii
is very strong. These findings provide further evidence of the
sensitivity, specificity, and value of histologic diagnosis of toxoplasmic lymphadenitis in immunologically competent individuals,
especially as our patient's condition was diagnosed preconceptually on the basis of characteristic histologic findings.
This case report documents that congenital transmission of T.
gondii to a live-born infant can occur from a mother without
known immunologic abnormality whose primary infection began
2 months before conception. Our patient is the third such patient
described in the literature. Remington and Desmonts [1, p. 153]
and Desmonts et al. [3] presented a similar case involving a child
with chorioretinitis and hydrocephalus with intracranial calcifications who was born to an immunocompetent mother who had
had toxoplasmic lymphadenopathy 2 months before conception.
Following placement of a ventriculoperitoneal shunt, that child
developed normally [1, p. 153; 3].
Garcia described histologic evidence of toxoplasma infection
in two successive siblings. The first infant, delivered at 7
months' gestation because of fetal distress, died with multipleorgan involvement due to T. gondii. The second fetus, conceived 5 months after delivery of the first, was spontaneously
aborted at 6 months' gestation and also had histologic evidence
of toxoplasma infection [1, p. 154; 2]. These cases present
exceptions to the earlier observations that congenital toxoplasmosis occurs only when infection is acquired during pregnancy
and that preconceptual infection is protective for subsequent
pregnancies [18].
It is noteworthy that fetal infection in the present report and
in the similar case described by Remington and Desmonts
[1, p. 153] and others [18-20] was not as severe as the typical
congenital toxoplasma infections acquired in the first trimester
[1, p. 153; 19]. Although this experience with two infants
whose mothers acquired infection in the 2 months immediately
before conception is too limited to allow definitive conclusions,
congenital infection acquired from a mother infected a few
months before conception may have a more favorable prognosis
than that occurring after maternal infection in the first trimester.
The explanation for these differences is speculative. Maternal immunity in these cases may have delayed transmission,
which could have resulted in infection to the fetus during a
less susceptible phase of its development. These case reports,
however, also suggest that delayed transmission could result
from persistent or recurrent toxoplasma parasitemia in some
immunocompetent mothers over a prolonged period. Parasitemia during the year after infection [20] and a delay in
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development of Toxoplasma-specific cell-mediated responsiveness in some acutely infected adults [21] have been noted.
As there are remarkable differences in genetic susceptibility
in animal models, we speculate that this might also occur when
T gondii infection occurs in women with greater genetic susceptibility or with selective suppression of cell-mediated immunity. Increased genetic susceptibility may also be present in
humans; for example, the DQ3 gene may be associated with
greater susceptibility in humans [22 and Johnson, Mack, Roberts, et al., unpublished data]. These factors may be permissive
to transplacental transmission of infection. It also is possible
that these two apparently healthy mothers had unrecognized
immunologic dysfunction(s) or that an alteration in the vimlence of Toxoplasma played a role in these cases.
The cases described above demonstrate that it is no longer
correct to assume that infection in the immediate months before
conception confers effective immunity against congenital transmission, and they warrant consideration of a cautionary change
in the approach to acute infection in symptomatic or asymptomatic immunologically competent women of childbearing age.
Newer serological tests (i.e., IgM, IgA, and IgE ELISA;
'SAGA; and AC/HS) establish the diagnosis of recent T. gondii
infection and are sufficiently sensitive and specific to obviate
the need for lymph node biopsy to establish the diagnosis of
acute acquired toxoplasmic adenopathy [23]. If such serological
evidence of infection is acquired in the months before conception (e.g., serum with an acute AC/HS pattern preconceptually),
then it would suggest at least some risk to the fetus, possibly
similar to that described herein.
Although the present case and two others [1, pp. 153 —4] are
the only reported cases of congenital toxoplasmosis transmitted
from a mother infected before conception, and there are no
data to indicate how frequently such transmission has occurred,
it would seem prudent to advise that there be an interval of
7-9 months from the time of T. gondii acquisition before
initiation of a pregnancy. This interval is greater than the longest time following which preconceptual maternal infection has
resulted in transmission to the fetus, when the mother has no
known immunocompromising illness.
If conception occurs in the first few months after primary
maternal toxoplasmosis, it seems reasonable that approach to
the care of the fetus in such cases should be the same as that
described for women infected during gestation [1, 24, 25]. This
includes starting treatment with spiramycin to decrease the risk
of transplacental infection of the fetus and amniocentesis to
exclude fetal infection [1]. If fetal infection is demonstrated,
then spiramycin is replaced by pyrimethamine and sulfadiazine
after the first 18 weeks of gestation; if not, then spiramycin is
given alone for the remainder of gestation. The infant is then
evaluated for congenital toxoplasmosis at birth [1, 26].
Acknowledgments
The authors gratefully acknowledge the assistance of Diane Patton and Vicki Aitchison in the preparation of the manuscript.
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Vogel et al.
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