Doi:10.1053/j.semperi.2007.01.002

Recent Advances in the Prevention andTreatment of Congenital Cytomegalovirus Infections Stuart P. Adler, MD,* Giovanni Nigro, MD,† and Lenore Pereira, PhD‡ Continued but slow progress has led to recent advances in our understanding that con-genital cytomegalovirus (CMV) infection has occurred. We understand that the mostsevere congenital disease occurs following a primary maternal infection during pregnancy.
We now have the ability to accurately diagnosis a primary maternal infection usingserologic studies of single serum sample. For pregnant women with young children, weknow that child-to-mother CMV transmission can probably be prevented by hygienicintervention, and that for pregnant women who have acquired a primary CMV infection,mother-to-fetal transmission is probably preventable using CMV hyperimmune globulin.
Although additional studies are needed, treatment of congenitally infected fetuses ornewborns should be possible using either CMV hyperimmune globulin or antiviral agentssuch as ganciclovir or its derivates. Finally, recent evidence indicates that CMV replicatesin the placenta, impairs development, and causes inflammation and dysfunction. This plusthe reversibility of many manifestations of congenital infection in the fetus and newbornindicate that congenital CMV disease is in part a syndrome of placental insufficiency.
Semin Perinatol 31:10-18 2007 Elsevier Inc. All rights reserved.
KEYWORDS cytomegalovirus, pregnancy, placental infection, placental enlargement, hyperim-
munoglobulin, antiviral therapy
Progressinpreventingcongenitalcytomegalovirus(CMV) Here, we review recent developments in our understanding infection has been remarkably slow, even though a 1999 of the pathogenesis, treatment, and prevention of congenital Institute of Medicine report, Vaccines for the 21st Century, stated that development of a CMV vaccine was the highestpriority for new Although government and indus-try funding for this effort remains inadequate, two CMV vac- Natural History of
cines are being evaluated, screening programs and interven- Maternal Infections
tions have been studied, and more is known about themechanism of transplacental virus spread and the natural history of congenital infection. Nevertheless, CMV transmis- sion continues imperceptibly, resulting in damage to about Nearly all symptomatic congenital infections occur when a 8000 infants in the United States each Without a vac- woman sustains a primary infection with CMV either during cine, recent efforts have focused on developing interventions or just before Infection appears to be associated that would justify universal screening of pregnant women.
with progressively increasing viral transmission rates by ges-tational age, but infections early in gestation probably resultin more severe congenital If infection occurs after *Department of Pediatrics, Virginia Commonwealth University, Medical conception, approximately 50% of fetuses will become in- College of Virginia Campus, Richmond, VA.
fected, and approximately one-half of those will have symp- †Department of Pediatrics, University of L’Aquila, L’Aquila, Italy. Email: toms at If infection occurs in the 6 months before ‡Department of Cell and Tissue Biology, University of California, San Fran- conception, transmission to the fetus and symptoms at birth cisco, CA. Email: [email protected].
will occur at a lower rate. In a recent study of 12 women who Address reprint requests to Stuart P. Adler, MD, Department of Pediatrics, acquired a CMV infection between 2 and 18 weeks before Virginia Commonwealth University, Medical College of Virginia pregnancy, only 1 of the newborns was asymptomatically Campus, P.O. Box 980163, Richmond, VA 23298. E-mail: [email protected] This rate is higher than expected for naturally im- 0146-0005/07/$-see front matter 2007 Elsevier Inc. All rights reserved.
doi:10.1053/j.semperi.2007.01.002 Recent advances in congenital CMV
mune women, but much less than if following a primary low-avidity anti-CMV IgG is the best way to diagnose a pri- Although congenital infections do affect infants born to Examination of amniotic fluid may be a helpful adjunct in mothers who are seropositive before pregnancy, they rarely prenatal diagnosis. Although viral culture of the amniotic result in symptomatic or severely affected infants. Such in- fluid is 100% specific, it often yields false-negative results.
fections are called “recurrent” infections and are caused ei- PCR, especially after 21 weeks’ gestation, is both sensitive ther by reinfection with new CMV strain or reactivation of a and specific for fetal A diagnosis of fetal CMV latent infection. The congenital infection rate in infants born infection alone is insufficient to predict whether the newborn to mothers with preconception immunity is between 0.2% will be symptomatic, but fetal abnormalities or placental en- and 2%. There is indirect evidence that reinfection of sero- largement detected by ultrasound are predictive of disease positive mothers with new strains of CMV can The most important risk factor for maternal CMV infection during pregnancy is frequent and prolonged exposure to About 10% of infants with congenital CMV infection have young Once infected, children less than 2 years of signs and symptoms at birth; 90% are asymptomatic. Some of age excrete virus in both saliva and urine for an average of 24 the initially asymptomatic children develop sequelae later in months. Hence, seronegative women who have contact with life, such as progressive sensorineural hearing loss. Some of young children are more likely to become infected than are these children are born of mothers with recurrent infec- women who do not. At least half of the women of middle and higher socioeconomic status in the United States are seroneg- In a recent study, fetal and placental ultrasound findings ative for CMV. These women are often exposed to infected were predictive of symptomatic newborn Fetal young children in the home or in daycare, and 50% of these findings included one or more of the following: ventriculo- women will acquire a CMV infection within 1 year. Thus, megaly, microcephaly, intrauterine growth restriction they are at high risk for delivering an infant with symptom- (IUGR), ascites, organomegaly by ultrasound, pyelectasis, megaloureter, and periventricular or hepatic and intestinal Both cellular and humoral immunity to CMV are impor- echodensities. Placental findings were related to an increase tant factors in viral transmission during pregnancy; women in maximal placental thickness (see below).
with impaired cellular immune responses (eg, those with Symptomatic infants have a constellation of clinical fea- AIDS or those receiving immunosuppressive therapy) are tures that reflect placental dysfunction and probable viral more likely to transmit the virus to the fetus. Neutralizing infection of the central nervous system of the fetus. Many of titers and IgG avidity to CMV antigens are both inversely the signs and symptoms overlap with those of other congen- correlated with Given the reduction of dis- ital viral infections. The symptoms that occur in one-half ormore of CMV-infected symptomatic infants include pete- ease severity in infants born to seropositive mothers, it is chiae and thrombocytopenia, hepatosplenomegaly, liver dis- presumed that in recurrent infections, preexisting immunity ease as manifested by jaundice (elevated direct bilirubin) and reduces or eliminates maternal viremia and is therefore pro- hepatic transaminases, IUGR, microcephaly, and intracranial tective to the fetus. The frequency of CMV transmission to the fetus and disease are associated with viral load, as measured volvement also occur in over one-half of symptomatic new- by polymerase chain reaction (PCR) either in fetal amniotic borns, including seizures, chorioretinitis (and other ocular abnormalities), hypotonia and a poor suck, elevated cerebro- The best method for the serologic diagnosis of asymptom- spinal fluid protein (Ͼ120 mg/dL), and hearing atic maternal primary infection is seroconversion; however, Some of the neurologic manifestations may be due to intra- this is rarely, if ever, achieved because universal serial sero- uterine hypoxia. Others, such as sensorineural hearing loss logic screening of pregnant women is not a standard practice (either bilateral or unilateral), are more likely to be due to in the United States. The detection of IgM antibodies in ma- viral infection and inflammatory effects on the fetus. The ternal sera can be helpful but is not without problems. Al- evidence for this is that hearing at birth may be normal, but though IgM antibodies to CMV occur in all primary infec- hearing loss can be slowly progressive over the first 5 to 10 tions, they may also occur after reactivation or reinfection and remain present for months. Hence, finding IgM to CMVin a single serum sample is not definitive for a primary CMVinfection.
Prevention of Maternal
Antibody avidity is a better method for maternal diagno- Infection during Pregnancy
As an indirect measure of the tightness of antibodybinding to its target antigen, avidity increases in the first Possible approaches to preventing congenital CMV infections weeks and months after a primary infection. Currently, apart include changes in hygienic behavior for seronegative preg- from seroconversion, the combination of anti-CMV IgM and nant women, administration of CMV hyperimmune globulin S.P. Adler, G. Nigro, and L. Pereira
(HIG) to pregnant women with a primary infection, and vac- safe administration of oral ganciclovir to mothers of CMV- cines administered to girls or women well before pregnancy.
infected fetuses. An HIV-positive woman was treated with Two studies were done to determine whether changing intravenous ganciclovir from 30 to 34 weeks’ gestation, fol- protective behaviors prevents child-to-mother transmission lowed by neonatal plasma ganciclovir concentrations of 0.8 of CMV during One studied 166 seronegative ␮g/mL measured at 2 hours after This was within the mothers with a child Ͻ36 months of age who attended 1 of median effective inhibitory dose, which ranges from 0.2 to 124 child care For each child care center, women 1.6 ␮In another report, ganciclovir given orally to a who were either pregnant or attempting to conceive (ie, not pregnant woman with CMV DNA in the amniotic fluid using contraception) were randomly assigned to either a con- reached amniotic concentrations higher than the minimal trol group or an intervention group. Mothers in the interven- inhibitory dose, and the neonate was Two case tion groups were given instructions for frequent hand wash- reports showed no teratogenicity of ganciclovir given in the ing, wearing gloves for specific childcare tasks, and avoiding early stages of The actual efficacy of ganciclo- various types of intimate contact with their child. All women vir remains to be defined in controlled trials.
and their children were monitored for CMV infection every 3 HIG was used to treat a mother with one of her twin fetuses months until delivery or, in women attempting conception, with a CMV infection and Response to HIG was for 12 months; 7.8% seroconverted. Logistic regression anal- suggested by the twin’s growth and decreased placental ysis revealed only 2 independent predictors of maternal in- thickening and cord edema. At birth, the male twin was un- fection: a child shedding virus at any time (50% of children infected, and the female twin was infected but healthy, with became infected after the mother’s enrollment in the study) normal psychomotor development. Subsequently, a multi- and a mother attempting pregnancy at the time of enroll- center prospective cohort study of 157 pregnant women with ment. For 41 women with a child shedding CMV, 10 of 24 confirmed primary CMV infection evaluated the use of who were not pregnant at enrollment became infected, com- Of these women, 148 were asymptomatic and were identified pared with only 1 of 17 women who were pregnant at enroll- by routine serologic screening; 8 had symptoms and labora- ment (P ϭ 0.008). In several studies, only 1 of 31 pregnant tory abnormalities consistent with CMV infection; and 1 was women acquired a CMV infection during pregnancy, com- identified because of abnormal ultrasound fetal images. Forty- pared with 60 of 147 nonpregnant women (P Ͻ five women in the therapy group had a primary infection Therefore, intervention before pregnancy is ineffective, but more than 6 weeks before enrollment, underwent amniocen- pregnant women with a child in daycare should be given the tesis, and had CMV DNA or culture-positive amniotic fluid.
option of serologic testing. Intervention for pregnant women Thirty-one of these women received CMV HIG (200 U per kg should be effective as they are more motivated to adhere to of the mother’s body weight). Nine women received 1 or 2 recommendations than nonpregnant women.
additional intraamniotic infusions because of persistent fetal Prevention of fetal infection by HIG was recently eval- abnormalities on ultrasonography. Fourteen women who de- By serologic screening, 181 asymptomatic pregnant clined HIG were the controls, and half of them had fetuses/ women with a primary CMV infection were identified. For infants with symptomatic CMV infection. In contrast, only 1 women with a primary infection at Ͻ21 weeks’ gestation or of the 31 women who received HIG had a diseased infant at for those who refused amniocentesis, HIG (100 U/kg) was birth (adjusted odds ratio, 0.02; P Ͻ 0.001), although 15 offered monthly until delivery. Of 126 women (mean gesta- were carrying fetuses with ultrasonographic evidence of in- tional age at infection, 14.3. Ϯ 7 weeks) who did not receive fection. In particular, 9 neonates were healthy despite prena- HIG, 56% delivered infected infants, compared with 16% of tal ultrasound signs of involvement with the following sys- 37 women (mean gestational age at infection, 13.2 Ϯ 5.5 tems: cerebral (5 with ventriculomegaly and 2 with weeks) who received prophylactic HIG (P Ͻ 0.001).
periventricular echodensities), hepatic (2 with hepatic Work is in progress to develop vaccines against CMV.
echodensities and 1 with hepatosplenomegaly and ascites), These experimental vaccines include a live attenuated strain intestinal (4 with echodensities), and renal (2 with pyelecta- Towne and a recombinant protein vaccine that uses the major sia, one of whom also had megaloureter involvement). Ad- glycoprotein B of CMV and an adjuvant Work ministration of HIG to the mother and fetal ultrasound ab- in this area has been slow but steadily ongoing, and clinical normalities before treatment were independent predictors of fetal outcome (P Ͻ 0.001). No adverse effects of HIG wereobserved.
The positive clinical results were supported by the immu- Pre- and Postnatal Treatment
nological studies performed in a subgroup of HIG-treated of Congenital CMV Infections
patients before and after the infusions or in untreated patientsat enrollment and after about 2 HIG-treated women showed a significant increase (P Ͻ 0.001) in CMV-specific Despite advances in the diagnosis of maternal–fetal CMV titers and IgG avidity after infusion and at the end of preg- infection, an effective therapy is unavailable. Pregnancy ter- nancy, compared with untreated women. Treated women mination is often offered as an option when affected or in- had a significant decrease (P Ͻ 0.01) in number, percentage, fected fetuses are identified by ultrasonography or amniocen- and cytotoxic activity of natural killer lymphocytes (CD56ϩ tesis, respectively. Recent case reports have focused on the CD16ϩ) and activated cells (HLAϪ DRϩ) at the end of preg- Recent advances in congenital CMV
nancy, compared with untreated mothers. These changes phorylation to ganciclovir triphosphate, which is recognized may be due to HIG inhibition of CMV replication, because as guanosine triphosphate by the viral DNA polymerase, with natural killer and DRϩ cells are increased at the onset of a consequent inhibition of CMV replication. Since the first primary CMV infection. However, the increased number and phosphorylation requires the presence of viral-encoded (UL activity of these immune cells is associated with a high pro- 97 gene) phosphotransferase, ganciclovir is active only in duction of cytokines, such as tumor necrosis factor alpha, infected cells. Potential adverse effects of ganciclovir in neo- which can contribute to the immune-mediated fetal dam- nates include transient neutropenia, which may necessitate Thus, HIG decreases the pathogenic effects of CMV by neutralizing antibodies and immunomodulatory effects Regarding the efficacy of ganciclovir, numerous studies suggested by the increased IgG concentration and avidity, have been published. Apart from a few infants with severe decreased number of natural killer and DRϩ cells, and de- pneumopathy or liver disease, all treated infants were symp- tomatic and had at least one neurologic manifestation: micro- The efficacy of HIG in humans is supported by its in vitro cephaly, seizures, abnormal cerebrospinal fluid, imaging ab- activity against CMV and by studies in guinea pigs going back normalities (calcifications, periventricular echodensities, 25 Pregnant guinea pigs have been challenged with cortical atrophy, ventriculomegaly, cystic leukomalacia, cer- guinea pig (gp)CMV before or after passive administration of ebellar hypoplasia, cerebral dysplasia by abnormal neuronal neutralizing antisera to either whole virus or gB, a glycopro- migration, large cisterna magna, intraventricular adhesions, tein that induces neutralizing Passive admin- hypoplastic corpus callosum, echogenic enhancement in the istration of immune serum to whole virus significantly in- caudothalamic grooves, lenticulostriate vasculopathy, and creased fetal survival from 51% to 77% when administered periventricular pseudocysts), hearing loss, or chorioretini- before gpCMV challenge and to 81% when given after viral In these experiments, immune serum did not A pilot study in 1994 compared 2 regimens of ganciclovir affect the rate of fetal infection, indicating that the immune treatment in 12 infants with severe neurologic manifesta- serum was therapeutic. In other guinea pig experiments with Group 1 (6 infants) received ganciclovir 5 mg/kg immune sera to purified gB, there was reduced fetal infection, twice daily for 2 weeks only, whereas group 2 (6 infants) placental inflammation, fetal death, and Ten of 12 received ganciclovir 7.5 mg/kg twice daily for 2 weeks, fol- fetuses of control (treated with nonimmune globulin) preg- lowed by 10 mg/kg three times a week for 3 months. In group nant dames died, compared with 3 of 23 pregnant dames 1, viral shedding disappeared in 3 infants, whereas in group treated with immune globulin to gB. This effect was indepen- 2, all 6 infants stopped shedding virus. In all infants in the dent of whether immune globulin was administered before or study, viral shedding reappeared after ganciclovir treatment after the challenge Additional high-titer immune was interrupted. Two infants of group 1 and 4 of group 2 had globulin given before or after maternal challenge significantly normal neurologic outcomes at 18 months of age. In 1 infant reduced the rate of fetal infection from 39% (9 of 23 fetuses in group 2, who was born to a mother with recurrent infec- infected) to 0% (0 of 18 fetuses infected). Immune globulin tion, microcephaly resolved. Two infants with initial chori- to gB administered before or after maternal challenge also oretinitis had normal eye examinations at 18 months of age.
significantly reduced placental inflammation and IUGR, as Three infants (2 in group 1 and 1 in group 2) developed measured by fetal weight. Thus, there are several plausible bilateral hearing loss that was detected before treatment.
mechanisms for the therapeutic efficacy of HIG: immuno- A larger phase II study compared two 6-week regimens of modulatory effects, reduction of viral load, and/or decreased ganciclovir (8 mg/kg/d versus 12 mg/kg/d, in 14 and 28 placental inflammation resulting in increased blood flow infants, respectively) for toxicity, virologic response, and with enhanced fetal nutrition and oxygenation.
clinical and neurologic The 12 mg/kg/d groupshowed a more pronounced antiviral effect in urine that wasassociated with a normal neurologic examination at 18 months of age. Data on audiologic performance, which were HIG has not been directly evaluated for the treatment of available for 30 of the 42 infants, did not differ by treatment neonates with symptomatic congenital CMV disease, but ob- group. Eleven of 13 infants with normal baseline hearing servations of neonates with transfusion-acquired CMV infec- developed deafness. Of 14 infants with initial chorioretinitis tions suggest that it may be Premature neonates (12 in the 12 mg/kg group), 8 had normal eye examinations born of seronegative mothers develop symptomatic CMV in- at 6 months. Of the infants with baseline normal eye exami- fection acquired from transfused blood products, but the nations, 3 developed retinal scarring. Eight of 33 children premature newborns from seropositive mothers remain (24%) evaluated at Ն2 years of age had normal neurologic asymptomatic after receiving the same blood products. After development, which did not differ by ganciclovir dosage.
birth, the infant’s maternal antibody to CMV declines rapidly, During therapy, the most significantly abnormal laboratory and by 8 weeks of age only 10% to 20% remains. Even at this finding was absolute neutropenia, which was more frequent age, although not protected against transfusion-acquired in- at a low dose (63% of children) than at a high dose (19% of fection, newborns are protected against disease.
children). A slight hypercreatinemia (always Ͼ2 mg/dL) was Ganciclovir may be used to treat neonates or infants with observed in 32% of children. Increased levels of liver en- congenital CMV disease. This drug is active only after phos- zymes (aspartate aminotransferase Ͼ250 IU/L; alanine ami- S.P. Adler, G. Nigro, and L. Pereira
notransferase Ͼ150 IU/L) were noted in 36% of both groups.
The embryo’s acquisition of a supply of maternal Of four infants who died, 1 had concomitant HIV, syphilis, blood is a critical hurdle in pregnancy maintenance. The mechanics of this process are accomplished by cytotropho- A subsequent randomized controlled trial of ganciclovir blasts, which are specialized epithelial cells of the placenta.
showed a beneficial effect on hearing deterioration in chil- Placentation, a stepwise process whereby cytotrophoblasts dren with at least 1 neurologic Ganciclovir initiate blood flow to the placenta, entails differentiation was given within the first month at 12 mg/kg/d intravenously along two pathways, depending on location. In floating villi, for 6 weeks. The primary endpoint was improvement of cytotrophoblasts fuse to form a multinucleate syncytial cov- brainstem-evoked potential between baseline and follow-up, ering, attached at one end to the tree-like fetal portion of the or, for patients with normal baseline hearing, normal brain- placenta. The rest of the villus, covered by syncytiotropho- stem-evoked potential at both time points. Functional eval- blasts, floats in a stream of maternal blood, delivering nutri- uation (results obtained with the better ear) was distin- ents and, later in gestation, maternal IgG across syncytiotro- guished from biological evaluation (results with individual ears), and the latter represented the biological effects of gan- To form anchoring villi, cytotrophoblasts undergo a novel ciclovir. Among 42 infants followed, functional evaluation at differentiation program, switching from an epithelial to an 6 months and 1 year showed significantly less hearing dete- endothelial phenotype that resembles vasculogenesis, con- rioration in treated infants (0% and 21%, respectively) than trolled through the coordinated actions of numerous fac- in control infants (41% and 68%, respectively) (P Ͻ 0.01 at Differentiating cytotrophoblasts initiate expression of both ages). A significantly higher number of treated infants invasion-promoting endothelial integrins, vasculogenic fac- had normal or improved hearing compared with control in- tors, and receptors that allow them to mimic the surface of fants. Neutropenia occurred more frequently (63%) in the vascular Cytotrophoblasts also upregulate matrix treated group than in the control group (21%). The large metalloproteinases that degrade the uterine and ex- proportion of unevaluable infants—58 of 100 subjects en- press immune molecules—nonclassical MHC class Ib mole- rolled—raises concerns about follow-up bias.
Two case reports provide pharmacokinetic data on oral ternal tolerance. The cells express chemokine–receptor pairs treatment with valganciclovir, the valine ester of ganciclo- that contribute to placental development and attract a spe- One infant with encephalitis due to perinatal HIV- cialized population of decidual leukocytes—natural killer CMV coinfection was treated for 1 year. Valganciclovir inhib- cells (CD56ϩ CD16Ϫ), macrophages, and dendritic cell ited CMV replication without side In another case, a progenitors—to the pregnant Cytotrophoblasts also continuous adaptation dose of 280 to 850 mg/m2 was needed express substances that influence vasculogenesis, including during 5.5 months of treatment of a symptomatic infant to vascular endothelial growth factor family ligands and recep- achieve plasma levels that made CMV DNA undetectable in tors that regulate cell survival at low oxygen the Since valganciclovir has variable bioavailability,dosage adaptation related to the viral load in the urine could be a better marker of the drug’s efficacy than pharmacoki-netic monitoring.
Ganciclovir has potential toxicity: short-term, high doses of Dramatic changes in oxygen content of the placental environ- ganciclovir can inhibit spermatogenesis and induce possible car- ment occur during gestation. In the first trimester, differen- cinogenic effects in For this reason, foscarnet that tiation occurs in a relatively hypoxic Cytotro- blocks viral DNA polymerase was Foscarnet was phoblast invasion is confined to superficial portions of administered for 4 months to an infant with multi-system uterine blood vessels near the lumen, and blood does not CMV disease. At 1 year and subsequent follow up until 10 flow to the intervillous In the second trimester, cy- years, clinical outcome and psychomotor development were totrophoblasts completely remodel the uterine vasculature and replace the endothelium up to the first third of the myo- In conclusion, for infants with symptomatic congenital metrium. By mid-gestation, cytotrophoblast differentiation CMV infection, a longer duration of antiviral therapy appears becomes sensitive to hypoxia that inhibits The to be associated with better outcomes.
hypoxia-inducible factor is a central mediator of cellular re-sponse to low oxygen and regulates expression of genes forcell survival, including vascular endothelial growth factor, Congenital CMV
which is modulated as cytotrophoblasts acquire an invasive Infection and the Placenta
phenotype. Cytotrophoblasts, which are relatively resistantto hypoxia, survive when they fail to access sufficient mater- nal blood, and cells proliferate and begin to differentiate but fail to complete integrin Invasion is impaired IUGR associated with congenital CMV disease suggests pla- in pregnancy complications such as preeclampsia and is cental deficiencies. Knowledge of the cellular and molecular characterized by shallow cytotrophoblast invasion in the processes involved in development of the human placenta is uterine vasculature and reduced maternal blood perfusion of a prerequisite to understanding how infection impairs func- Recent advances in congenital CMV
IgG from the maternal to the fetal Immune complexes of CMV virions and IgG in secretions and blood that bathe the placenta are endocytosed by syncytiotropho-blasts, and some are transcytosed to cytotrophoblasts. In the Immunofluorescence analysis of paired decidual and placen- presence of IgG with low neutralizing titer, focal infection can tal biopsy specimens from early gestation showed that pat- occur. Although replication is not usually found in CMV terns of CMV replication vary depending on maternal immu- DNA-positive placentas from immune mothers with high In highly infected placentas, cell islands in both neutralizing titer, syncytiotrophoblasts accumulate vesicles decidual and placental compartments expressed viral repli- cation proteins, and neutralizing titers were low. In the de- A recent study of CMV virion receptors provided another cidua, the uterine vasculature and interstitial cytotrophoblasts explanation for why focal infection occurs in some villus contained viral replication proteins, as did cytotrophoblasts and cytotrophoblast progenitor cells but not others. Cell surface fetal capillaries in the adjacent placenta, suggesting transmis- adhesion molecules for virions are developmentally regu- sion. In moderately infected placentas, the number of cells lated as trophoblasts progress from the fetal to the maternal with viral replication proteins was reduced in the decidua compartment. Indeed, location of productive infection sug- and placenta, with occasional focal infection. This pattern gests virion engagement with receptors that are expressed predominated in women with low to intermediate neutraliz- during differentiation (Maidji E, Genbacev O, Chang HT, et ing titers. PCR analysis confirmed the presence of CMV DNA, al, manuscript submitted for publication, December 13, sometimes alone and sometimes in combination with herpes 2006). In floating villi, syncytiotrophoblasts express the epi- simplex viruses, chlamydia, and pathogenic In dermal growth factor receptor that binds CMV but placentas without viral DNA and infection, few cells con- they lack the integrin coreceptors ␣1␤1 and ␣V␤3 used in tained viral replication proteins in the adjacent decidua. This fibroblasts and endothelial Strikingly, focal infec- pattern predominated in women with intermediate to high tion begins in villus cytotrophoblasts that upregulate ␣V in- neutralizing titers. Sometimes syncytiotrophoblasts and vil- tegrin expression (Maidji E, Genbacev O, Chang HT, et al, lus core macrophages contained vesicles with the CMV virion manuscript submitted for publication December 13, 2006).
envelope glycoprotein gB without replication. Placental in- Invasive cytotrophoblasts in decidua express integrins ␣1␤1 fection that leads to fetal transmission likely involves viral and ␣V␤3 and upregulate the epidermal growth factor recep- replication in the decidua, in cytotrophoblasts of placentas tor, dramatically increasing susceptibility to infection. On the with the lowest neutralizing titers, and in cytotrophoblasts of whole, the barrier function of the early gestation placenta is some placentas with intermediate titers, including recurrent compromised by transcytosis of virion-containing immune complexes from the proximal infected decidua that reach A recent study of placentas from uncomplicated deliveries villus cytotrophoblasts expressing virion receptors.
reported that more than 50% of biopsy specimens containedCMV DNA without other Analysis of virion pro-teins and antibody levels suggested that there was suppressed infection in placentas with moderate to high neutralizing antibody titers: 5% of the biopsy specimens from these pla- The early gestation placenta is not merely a passive conduit centas contained CMV DNA. Even when neutralizing titers for virion transport to the fetal compartment. Infected cy- were low, focal infection was seldom found in the placenta.
totrophoblasts dysregulate key differentiation molecules that Instead, leukocytes in fetal blood vessels in the villus core are required for interstitial and endovascular invasiveness at contained viral replication proteins. According to current di- the level of transcription and protein These agnostic criteria, CMV proteins and DNA in leukocytes are molecules include integrins for cell– cell and cell–matrix ad- markers for recent The results suggest that there hesion and the class I MHC molecule HLA-G for maternal is transplacental spread, virus replication, and dissemination immune tolerance for the allogeneic fetus. One viral gene in the fetus. Thus, congenital infection could be higher than product that functions as a pathogenesis factor at the uterine– estimated, as most infants appear asymptomatic at birth.
placental interface, cmvIL-10, is an immunosuppressive cy-that impairs cytotrophoblast functions at multiple levels. For example, cmvIL-10 is strongly upregulated in in-fected cells and reduces matrix metalloproteinase-9 protein and Dysregulation of downstream effector mole- cules undermines key functions. Cytotrophoblast differenti- A puzzling pattern of CMV replication in floating villi in utero ation and invasiveness are markedly impaired by dysregu- suggested a circuitous route for virus spread to the placenta lated integrin expression, reduced cell adhesion, and that spares syncytiotrophoblasts but allows focal infection in degradation of the extracellular It is noteworthy that proteins dysregulated in CMV-infected cytotrophoblasts tible cells that involves transcytosis in immune complexes are among those altered in preeclampsia—a pregnancy com- was confirmed using villus explants in Syncytiotro- plication characterized by poor placentation leading to hypo- phoblasts express the neonatal Fc receptor that transports S.P. Adler, G. Nigro, and L. Pereira
Placental Damage and Congenital Infection cally thickened placentas and respond to HIG administra- In congenital CMV infection, IUGR can occur in the absence of fetal infection as a result of placental Histo-logical studies of infected placentas show distinctive changes, including villous fibrosis, calcification, and leukocytic infil- Fibrin deposits that encase villi and damage syncy- Many symptoms of congenital CMV infection that are present tiotrophoblasts block contact with maternal blood. Throm- at birth may not be due to a direct effect of the virus on the bosis in chorionic (fetal) blood vessels and resulting fetus. Rather, they may be due to an indirect effect of intra- avascular villi reduce transport of nutrients and oxygen to the uterine infection on the placenta, which may be impaired in fetal bloodstream. Paradoxically, active viral replication is its capacity to provide oxygen and nutrients to the develop- seldom detected in the placenta at delivery, except in some ing fetus. Several lines of evidence suggest this possibility.
cases of primary infection and severe symptomatic disease.
(i) Many manifestations of congenital infection—IUGR, Possibly, increased neutralizing titers and targeting of infec- microcephaly, liver disease, hematopoietic abnormalities, tion sites by innate immune cells limits CMV replication as and splenomegaly—resolve over the first weeks to months of gestation Ongoing studies of placentas from life, concurrent with adequate oxygenation and nutrition of infants with congenital infection, with and without HIG the newborn. These manifestations include some neonatal revealed significant differences. Among these are neurologic symptoms associated with intrauterine hypox- morphological changes that suggest compensatory develop- emia. For example, neonatal thrombocytopenia, present at ment of chorionic villi with intact syncytiotrophoblasts and birth in 75% of symptomatic CMV-infected newborns, iscaused by impaired megakaryocytopoiesis and platelet pro- blood vessels (E. Maidji and L. Pereira, unpublished obser- duction secondary to a pregnancy complicated by placental vations). The renewed capacity of the placenta to transport insufficiency and/or fetal Fetal hypoxia leading to oxygen, nutrients, and HIG in treated mothers could pro- cerebral hypoxia and ischemia is a well-established cause of mote fetal growth, suppress infection, and prevent symptom- perinatal brain injury and may be associated with periven- tricular calcifications that occur in half of affected newborns.
During intrauterine hypoxia in premature infants, the cere- bral white matter is the site of injury and leads to periven- tricular This condition consists of focal cysticinfarcts adjacent to the lateral ventricles and a diffuse gliosis Serologic testing for primary maternal CMV infection during that extends throughout the cerebral white matter.
pregnancy is not routine, but ultrasound studies, which are, (ii) Many infants born of mothers with primary or recur- can show abnormalities of the placental–fetal unit. Given this rent infection are asymptomatic and develop normally, de- fact and the knowledge that CMV causes extensive acute and spite viremia in utero and postnatally, and shedding of virus chronic placental inflammation, placental thickening was in urine and saliva for years after birth. Infants acquiring evaluated in women with primary CMV infections during CMV postnatally exhibit similar patterns of viremia and viral Ninety-two women with primary infection and excretion without symptoms. Even when CMV is acquired 73 CMV-seropositive pregnant women without primary in- through transfusion by very low birth weight infants (Ͻ1250 fection were studied. Thirty-two women were treated with g) of seronegative mothers, the infants may become ill but do HIG to either prevent or treat intrauterine CMV infection.
not develop the symptoms acquired in utero after primary Maximal placental thickness was measured by longitudinal (nonoblique) scanning, with the ultrasound beam perpen- (iii) CMV infection is occasionally associated with a “blue- dicular to the chorial dish. Programmed placental ultrasound berry muffin” syndrome, in which purpura is caused by ex- evaluations were performed from 16 to 36 weeks’ gestation.
tramedullary hematopoiesis indicative of intrauterine At each placental measurement, women with primary (iv) Hepatomegaly due to biliary obstruction, secondary to CMV infection and a fetus or newborn with CMV disease had extramedullary hematopoiesis and erythrocytic congestion, significantly (P Ͻ 0.0001) thicker placentas than women is responsible for marked splenic enlargement in most symp- without infected fetuses, and these women in turn had sig- nificantly (P Ͻ 0.0001) thicker placentas than seropositive (v) Administration of HIG to pregnant women with pri- controls. After primary infection, for women with or without mary CMV infection is associated with the resolution of in infected fetuses or newborns, treatment with HIG was asso- utero signs of fetal infection detected by ultrasound and with ciated with significant (P Ͻ 0.001) reductions in placental the delivery of normal infants who develop Re- thickness. Placental vertical thickness values, predictive of versal of fetal symptoms suggests that HIG could improve primary maternal infection, were observed at each measure- placental function possibly by reducing inflammation that ment from 16 to 36 weeks’ gestation, and cut-off values ranged from 22 to 35 mm, with the best sensitivity and spec-ificity at 28 and 32 It was concluded that primary maternal CMV infections Lenore Pereira laboratory studies were supported by NIH and fetal or neonatal disease are associated with sonographi- grants AI46657 and AI53782, Thrasher Research Fund grant Recent advances in congenital CMV
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