Microbial causes of mental retardation. The role of prenatal infections with cytomegalovirus, rubella virus, and toxoplasma

The Global Pregnancy Collaboration (CoLab) symposium on short- and long-term outcomes in offspring whose mothers had preeclampsia: A scoping review of clinical evidence

Preeclampsia is a maternal syndrome characterized by the new onset of hypertension after 20 weeks of gestation associated with multisystemic complications leading to high maternal and fetal/neonatal morbidity and mortality. However, sequelae of preeclampsia may extend years after pregnancy in both mothers and their children. In addition to the long-term adverse cardiovascular effects of preeclampsia in the mother, observational studies have reported elevated risk of cardiovascular, metabolic, cerebral and cognitive complications in children born from women with preeclampsia. Less clear is whether the association between maternal preeclampsia and offspring sequelae are causal, or to what degree the associations might be driven by fetal factors including impaired growth and the health of its placenta. Our discussion of these complexities in the 2018 Global Pregnancy Collaboration annual meeting prompted us to write this review. We aimed to summarize the evidence of an association between maternal preeclampsia and neurobehavioral developmental disorders in offspring in hopes of generating greater research interest in this important topic.

Intrauterine Viral Infections: Impact of Inflammation on Fetal Neurodevelopment

Intrauterine viral infections during pregnancy by pathogens such as Zika virus, Cytomegalovirus, Rubella and Herpes Simplex virus can lead to prenatal as well as postnatal neurodevelopmental disorders. Although maternal viral infections are common during pregnancy, viruses rarely penetrate the trophoblast. When they do cross, viruses can cause adverse congenital health conditions for the fetus. In this context, maternal inflammatory responses to these neurotropic pathogens play a significant role in negatively affecting neurodevelopment. For instance, intrauterine inflammation poses an increased risk of neurodevelopmental disorders such as microcephaly, schizophrenia, autism spectrum disorder, cerebral palsy and epilepsy. Severe inflammatory responses have been linked to stillbirths, preterm births, abortions and microcephaly. In this review, we discuss the mechanistic basis of how immune system shapes the landscape of the brain and how different neurotropic viral pathogens evoke inflammatory responses. Finally, we list the consequences of neuroinflammation on fetal brain development and discuss directions for future research and intervention strategies.

Neuropsychiatric manifestations of latent toxoplasmosis on mothers and their offspring

Toxoplasmosis is one of the most common parasitic diseases worldwide. It is estimated that approximately one-third of the world's population is latently infected. Infection generally occurs via oral the route and maternal transmission. Damage of the central nervous system is one of the most serious consequences of congenital toxoplasmosis. Moreover, recent investigations proposed that acute and sub-acute congenital toxoplasmosis as well as latent toxoplasmosis during pregnancy; play various roles in the etiology of different neuropsychiatric disorders in mothers and their offspring. This paper reviews new findings about the role of latent toxoplasmosis in the etiology of various neuropsychiatric disorders in mothers and their offspring.

Cytokines and the neurodevelopmental basis of mental illness

Epidemiological studies suggest that prenatal exposure to different types of viral or bacterial infections may be associated with similar outcomes; i.e., an increased risk of mental illness disorders in the offspring. Infections arising from various causes have similar debilitating effects in later life, suggesting that the exact pathogen may not be the critical factor in determining the neurological and cognitive outcome in the offspring. Instead, it is thought that response of the innate immune system, specifically the increased production of inflammatory cytokines, may be the critical mediator in altering fetal brain development pre-disposing the offspring to mental illness disorders later in life. Inflammatory cytokines are essential for normal brain development. Factors such as the site of cytokine production, a change in balance between anti- and pro- inflammatory cytokines, placental transfer of cytokines, the effects of cytokines on glial cells, and the effects of glucocorticoids are important when evaluating the impact of maternal infection on fetal brain development. Although it is clear that cytokines are altered in the fetal brain following maternal infection, further evidence is required to determine if cytokines are the critical factor that alters the trajectory of brain development, subsequently leading to postnatal behavioral and neurological abnormalities.

Terminal 4q deletion syndrome

Terminal deletion of the long arm of chromosome 4, (4q) is a rare event. It is characterized by spectral phenotypic manifestations, depending upon the site and quantity of chromatin lost. The chromosomal loss which span 4 (q31-q35) segment often manifests as craniofacial anomalies, mental retardation with ocular, cardiac, genitourinary defects and pelvic/limb dysmorphism. These abnormalities are usually unilateral. We report a female child (46, XX), aged 11 months, born to nonconsanguineous parents, bearing chromosomal deletion of 4 (q31.2-35.2) segment, which has manifested as craniofacial hypoplasia of left side of face, ipsilateral ptosis, erythroderma and bilateral thumb anomalies.

Why prevent, diagnose and treat congenital toxoplasmosis?

Evidence that prevention, diagnosis and treatment of toxoplasmosis is beneficial developed as follows: anti-parasitic agents abrogate Toxoplasma gondii tachyzoite growth, preventing destruction of infected, cultured, mammalian cells and cure active infections in experimental animals, including primates. They treat active infections in persons who are immune-compromised, limit destruction of retina by replicating parasites and thereby treat ocular toxoplasmosis and treat active infection in the fetus and infant. Outcomes of untreated congenital toxoplasmosis include adverse ocular and neurologic sequelae described in different countries and decades. Better outcomes are associated with treatment of infected infants throughout their first year of life. Shorter intervals between diagnosis and treatment in utero improve outcomes. A French approach for diagnosis and treatment of congenital toxoplasmosis in the fetus and infant can prevent toxoplasmosis and limit adverse sequelae. In addition, new data demonstrate that this French approach results in favorable outcomes with some early gestation infections. A standardized approach to diagnosis and treatment during gestation has not yet been applied generally in the USA. Nonetheless, a small, similar experience confirms that this French approach is feasible, safe, and results in favorable outcomes in the National Collaborative Chicago-based Congenital Toxoplasmosis Study cohort. Prompt diagnosis, prevention and treatment reduce adverse sequelae of congenital toxoplasmosis.

Increased risk for developmental disabilities in children who have major birth defects: a population-based study

OBJECTIVE

We sought to quantify the strength of associations between each of four specific developmental disabilities (DDs) and specific types of major birth defects.

METHODS

We linked data from 2 independent surveillance systems, the Metropolitan Atlanta Congenital Defects Program and the Metropolitan Atlanta Developmental Disabilities Surveillance Program. Children with major birth defects (n = 9142; born 1981-1991 in metro Atlanta) and 3- to 10-year-old children who were born between 1981 and 1991 in metro Atlanta and identified between 1991 and 1994 as having mental retardation, cerebral palsy, hearing impairment, or vision impairment (n = 3685) were studied. Prevalence ratio (PR), which is the prevalence of a DD in children with 1 or more major birth defects divided by the prevalence of the same DD in children without major birth defects, was measured.

RESULTS

Among the 9142 children who were born with a major birth defect, 657 (7.2%) had a serious DD compared with 0.9% in children with no major birth defect, yielding a PR of 8.3 (95% confidence interval: 7.6-9.0). In general, the more severe the DD, the higher was the PR. Birth defects that originated in the nervous system and chromosomal defects resulted in the highest PRs for a subsequent DD. For all other categories of birth defects, PRs were lowest when all major birth defects present were confined to a single category (ie, isolated defects). PRs for any DD increased monotonically with the number of coded birth defects per child or the number of different birth defect categories per child, regardless of the severity of the defect or whether defects of the nervous system, chromosomal defects, or "other syndromes" were counted.

CONCLUSIONS

These data highlight the possible early prenatal origins of some DDs and suggest that both the number of coded birth defects present and the number of anatomic systems involved are strongly related to functional outcomes.

Can cytomegalovirus cause brachydactyly? A case report and review of the literature

A child with the diagnosis of CMV infection associated with brachydactyly is presented. The case is interesting as, to our knowledge, no similar case has been reported up to the present. In our case, apart from CMV, no teratogenic factor which may cause brachydactyly could be detected.

Cytomegalovirus infection of the developing brain alters catecholamine and indoleamine metabolism

Tissue concentrations of noradrenaline (NA), serotonin (5-HT), dopamine (DA) and selected metabolites were measured in the spinal cord, cerebellum, cerebral cortex and caudate-putamen of developing mice following intraventricular inoculation with murine cytomegalovirus (MCMV) on postnatal day 10. MCMV-infected animals exhibited transient signs of neurological impairment, including apparent hypertonicity of hindlimb extensors and abnormal gait, beginning on days 14-16 and continuing for 3-5 days. At the onset of neurological impairment, tissue concentrations of NA were significantly reduced in the spinal cord (20%), cerebellum (32%) and cerebral cortex (40%) of infected animals. Levels of 5-HT were significantly increased in the caudate-putamen (50%), while 5-hydroxyindoleacetic acid (5-HIAA) was increased in both the spinal cord (94%) and caudate-putamen (65%). The ratio of 5-HIAA/5-HT, which is frequently used as an estimate of turnover of 5-HT, was significantly increased in the spinal cord (90%) at the onset of neurological impairment. In the caudate-putamen of MCMV-infected animals, there were significant increases in the tissue levels of DA (37%), homovanillic acid (HVA, 41%) and 3,4-dihydroxyphenylacetic acid (DOPAC, 34%). All neurochemical parameters were normal in the MCMV-infected animals by postnatal day 70, approximately 50 days after the resolution of neurological signs. These results indicate transient alterations in monoamine metabolism in the developing nervous system during the pathogenesis of cytomegalovirus-induced movement and postural disorders.

Cytomegalovirus infection in Gambian mothers and their babies

A 15 month longitudinal study of cytomegalovirus (CMV) infection in 178 Gambian mothers and their babies was undertaken. Twenty five (14%) of the babies were congenitally infected despite the fact that 87% of their mothers were antibody positive to the virus. Two of the 25 congenitally infected infants had evidence of severe neurological damage; skin sepsis was also a prominent feature in congenitally infected infants. The other children soon became infected. At 6 months of age, 53% of the infants were shedding virus either in urine or saliva. By the age of 12 months 86% of the infants had serological evidence of CMV infection. Preliminary evidence suggests that sibling to sibling infection in crowded compounds might be a major route of transmission.

Increased uric acid in the developing brain and spinal cord following cytomegalovirus infection

Tissue concentrations of uric acid were determined in the spinal cord, cerebellum, caudate-putamen, and cerebral cortex of developing mice following intraventricular inoculation with murine cytomegalovirus (MCMV) on postnatal day 10. Transient signs of neurological impairment were observed in MCMV-infected animals beginning on days 13-16 and continuing until days 19-21. At the onset of neurological impairment, uric acid concentrations in tissues from infected animals were 17-60-fold greater than in control animals. On postnatal day 70, 60 days after inoculation and 40 days after resolution of neurological signs, uric acid levels were still two- to threefold greater in infected animals. Histological examination revealed signs of focal ischemia in the cerebral and cerebellar cortices of MCMV-infected mice only at the onset of neurological impairment, with ischemic cell changes in some pyramidal neurons of the cerebral cortex. These results indicate that uric acid may be a sensitive marker of persistent vascular pathology resulting from cytomegalovirus infection of the developing nervous system.

Enzyme linked immunosorbent assay (ELISA) for determination of IgG antibodies to human cytomegalovirus

A solid-phase enzyme linked immunosorbent assay (ELISA) for determination of IgG antibodies to cytomegalovirus (CMV) is described. The assay used purified CMV and extracts of CMV infected cells as antigen. Antigens were desiccated onto the bottom surface of polystyrene microcuvettes. The antibodies bound to the antigens were assayed by anti-IgG-alkaline phosphate conjugate followed by addition of the enzyme substrate. Titration curves have been obtained from the sera of 35 blood donors and of 23 patients. Comparison of results obtained by ELISA with those obtained by complement fixation (CF) shows that there is agreement between the tests. Both purified CMV and extracts of CMV infected cells were found to be suitable antigens. Purified CMV was of value particularly in those sera which show high reactivity against control antigen. The ELISA technique described is approximately 412 to 548 times more sensitive than the CF test when purified CMV or extracts of CMV infected cells, respectively, are used as antigens. No significant heterotypic rise to CMV was observed by ELISA in three sets of sera with seroconversion to herpes simplex virus. The ELISA technique gives objective results, is easily performed, and may be adaptable as a routine test both for serological diagnosis of CMV infection and for screening of the general population.

Detection of human cytomegalovirus-specific IgG antibodies by a sensitive solid-phase radioimmunoassay and by a rapid-screening test

A radioimmunoassay (RIA) for the detection of human IgG antibodies to cytomegalovirus (CMV) which utilizes extracts of CMV-infected cells as antigen is described. Sera of 66 healthy adults were titered by the RIA and by the complement fixation (CF) test. These same subjects were also used in the evaluation of a rapid screening radioimmunoassay (RSRIA) developed to detect IgG antibodies to CMV in small serum samples. The specificity of the RIA was evaluated by testing sera of seven CMV patients and ten patients with heterotypic titer rises to herpes simplex virus or varicella zoster virus (HSV or VZV). The RIA proved to be sensitive and specific. Possible applications of the RSRIA modification are discussed.

Stimulation of human lymphocytes by cytomegalovirions and dense bodies

Lymphocytes from healthy adult individuals were examined for their ability to incorporate thymidine in the presence of cytomegalovirus (CMV) and dense bodies. It was found that lymphocytes from donors with antibodies to CMV were stimulated to incorporate thymidine-14C both by preparation of CMV and CMV dense bodies. Lymphocytes from CMV seronegative donors did not respond. Dilution experiments and the dose-response curve indicate that the stimulation induced by the dense body preparation was not caused by the small amounts of contaminating CMV particles. These results indicate that in healthy human adults there is a correlation between CMV seropositivity and in vitro lymphocyte transformation, induced by either CMV or by dense bodies.

Pathological observations on experimental cytomegalovirus infections in pregnancy

Cytomegalovirus injected intramuscularly or intraperitoneally into mice on the 8th day of pregnancy resulted in a significant retardation in foetal growth and a reduced number of offspring surviving until near-term. Pathological changes consisted of inflammatory cell infiltration in the liver, heart, salivary glands and adrenal cortex of affected animals. Necrotic changes were also present in the adrenal cortex in most severely affected animals following intraperitoneal injection of virus. Intraperitoneal infection led to a frank peritonitis and marked splenic necrosis with a degeneration and inflammation of visceral fatty tissue and lymphadenitis. In contrast, intramuscular injection of virus did not produce a peritonitis but the spleen was greatly enlarged with reaction centres and increased numbers of lymphocytes being identified at histology. As a consequence of cytomegalovirus infection in pregnant mice foetal growth impairment and intrauterine death was seen. This was related to the severity of pathological changes in the mothers. In those animals dying or appearing sick at near-term, most foetuses were dead and resorbing. Since murine cytomegalovirus was not identified by inclusion body formation in foetal or placental tissues in this study and virus has not been isolated from these tissues previously, it was concluded that the mechanism for the impaired foetal growth was of an indirect nature and attributable primarily to a severe generalised maternal illness.

An aetiological study of 1,000 patients with an I.Q. assessment below 51

This paper examines the actiological basis of the severer grades of mental retardation in 1,000 individuals attending an outpatient clinic. It was found it was possible to make a suggested diagnosis in 78% of cases. These fell into broad aetiological groups: genetically determined, 25%: early prenatal abomalies, 18%: perinatal damage, 17% prenatal and postnatal infections, 15%; cultural disintegration, 3%. The changing pattern of incidence and the possibilities of prevention are discussed for each group.

A comparison of the effects of cytosine arabinoside and adenine arabinoside on some aspects of brain growth and development in the rat

1. Treatment of pregnant rats with cytosine arabinoside (ara-C, 50 mg/kg, i.p.)at 14 days of gestation severely impaired both prenatal and postnatal whole brain growth in their offspring, although the cerebellum was relatively less affected than whole brain. 2. Rats treated at 5 days of age with ara-C (250 mg/kg, i.p.) showed an impairment in growth of the cerebellum relative to the rest of the brain. 3. Adenine arabinoside (ara-A) treatment, either prenatally or postnatally, had negligible effect on brain growth, even at doses considerably higher than those of ara-C. 4. Adult rats, previously treated with ara-C (50 mg/kg, i.p.) at 14 days of gestation, showed an impairment in discrimination learning when tested in a water T-maze. 5. These results are discussed in relation to the proposed use of ara-C or ara-A as antiviral agents, particularly against intrauterine infection with cytomegalovirus.

Prospective study of cytomegalovirus infection in pregnancy

In a prospective study of cytomegalovirus infection in 1,040 pregnant women in London 319 (42%) of the white Englishwomen but only 28 (10%) of the immigrant Asian women were without antibodies at the onset of pregnancy. Out of 254 susceptible white women and 16 susceptible Asian women 8 (3%) and 3 (16%) respectively experienced primary infection during the course of pregnancy. The overall incidence of fetal infection after primary infection in the mother was almost 50%, and was higher in early pregnancy. One out of the five infected infants was found to be mentally retarded.Reactivation of latent infection was recognized in 0.7-2.9% of pregnant women; this occurred without involving the fetus.

Infective agents and embryopathy in the west of Scotland 1966-1970

Firm or suggestive evidence of congenital infection was obtained in 25 (10.5%) of 239 children under 1-year-old with suspected embryopathy in the west of Scotland during the 4-year period from September 1966. The numbers of infections associated with the various agents studied were: rubella 11, coxsackievirus 4, cytomegalovirus 3, herpes simplex 3, toxoplasma 3, mumps 1. Persisting residual defects were found in 17 of these 25, 9 being associated with congenital rubella.

Prevalence of cytomegalovirus in France

Between October 1968 and February 1970, 30 strains of cytomegalovirus were isolated from the urine of children admitted to hospitals in Lyon. Three groups of children up to the age of 14 years have been investigated.The first group consisted of 304 newborns and infants up to the age of 1 year; cytomegalovirus was grown from five of these (1.6%). Among these five children, two had cerebral disorders. None of them had ever shown any sign of typical CMV infection.The second group comprised 102 children between the ages of 1 and 14 years, from a special service for neurological and mental diseases. Cytomegalovirus was grown from 19 (18.6%).The third group was 27 children also between 1 and 14 years of age, admitted to hospital for miscellaneous diseases excluding cerebral disorders; cytomegalovirus was grown from six (22.2%).It appears that cytomegalovirus has a very low incidence in neonatal disease. The virus spreads at a higher rate in children 1-14 years old. No difference has so far been shown in the excretion rates of two groups of children, one with cerebral disorders and one with other diseases, but the number of children in the last group is too small to allow definite conclusions to be drawn.

Cytomegalovirus infection in the north west of England. A report on a two-year study

The incidence and epidemiology of cytomegalovirus (CMV) in Manchester has been studied for two years. 36 cases of congenital infection were found. Over 90% of those detected in routine surveys or born without central nervous system disease have not shown any serious developmental defects following their virus infection and are progressing normally. Virus excretion was found in 3·2% of children admitted to hospital, but, except in cases with mental retardation (with or without symptoms of central nervous system disease) and with feeding problems, there was no definite relation between virus excretion and the clinical condition bringing them into hospital. Serological surveys of different groups in the population indicated that the majority of infections occurred in adolescence and early adulthood, that 40-45% of women of child-bearing age were not immune to CMV, and that 5% of blood donors were capable of transmitting infection to patients receiving blood transfusions. Virus was isolated from 5·2% of schoolchildren aged 5-6 years, from 0·4% of babies born in hospital, and from the cervix of 3-4% of women attending hospital clinics. In adults CMV infection was found to be associated sometimes with atypical glandular fever, hepatitis, and polyneuritis. Very close contact seems necessary for the spread of CMV.