Viral teratology

Poxviruses in Children

The family Poxviridae is a large family of viruses with a ubiquitous distribution, subdivided into two subfamilies: Chordopoxvirinae (poxviruses of vertebrates) and Entomopoxvirinae (poxviruses of insects). Only three species from the first subfamily, Orthopoxvirus (OPV), Molluscipoxvirus and Parapoxvirus, can infect the human being. In the paediatric population, viruses belonging to the first two subfamilies have the greatest importance. Following the eradication of smallpox in 1980, vaccination of the general population was discontinued after careful consideration of the risks and benefits. However, nearly all children and most of the world's population had little to no protection against OPV. The aim of this chapter is to review the current evidence on the aetiology, clinical manifestations, diagnosis and management of Poxviridae infections in children.

The effects of maternal murine cytomegalovirus infection on the mouse conceptus at different gestational stages

The effects of murine cytomegalovirus (MCMV) on the prenatal development of the CD-1 mouse were investigated. Two sets of experiments were performed. In the first, mice were inoculated with different doses of MCMV on gestational day 7, and in the second, pregnant animals were inoculated with a subacute injection dose at different gestational stages. The effects of maternal infection on pregnancy in terms of maternal sickness, embryo lethality, date of parturition, litter size, postnatal death, and pups' body weight on d 1 and d 3 postpartum were investigated. High-dose MCMV infection on d 7 of pregnancy resulted in a significant increase in early embryo resorption and also in a reduction of the neonatal body weight of surviving pups. Two gestational stages were identified as being especially susceptible to MCMV infection. Most embryonic death as indicated by resorption rates was found after treatment on d 9, whereas perinatal death was most frequent when treatment was done on d 13 of gestation. Still births and neonatal death within 24 h of birth were found commonly in this latter group, which also showed the most pronounced growth retardation. The phenomenon of delay in time of parturition was noted and found to be most significant in groups of animals that were inoculated on d 3 or d 13. This investigation suggests that the effects of MCMV on the CD-1 mouse vary greatly with the age of the embryo and the course of the infection.

The growth of reovirus 3 in cultured rat embryos and implications for human reproductive failure

Ten-day rat embryos were exposed to different concentrations of reovirus 3, heat-inactivated virus or diluent and then cultured for 48 h. An effect on embryonic growth and development was observed that required live virus. Virus concentrations of 10(6.0) TCID50 were embryolethal while 10(5.0) TCID50 killed about 20% of embryos and caused varying degrees of growth retardation in the remainder. Growth of the agent in the visceral yolk sac and embryonic tissues was confirmed by virus titration and immunofluorescent studies. Infectious virus was detected in the medium after 6-8 h and increased exponentially throughout the 48 h culture period, except for a check around 18 h. The significance of the findings in relation to previous animal studies and the potential importance of reovirus as a cause of human reproductive failure are discussed.

Viral antibodies in maternal and cord sera

Viral antibodies were determined in paired maternal and cord blood sera of 258 consecutive deliveries. Antibodies to Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpes simplex type 1 (HSV-1), adenovirus (ADV), and varicella zoster (VZV) were tested by indirect immunofluorescence and to rubella (RUB) by hemagglutination inhibition. Analysis of the overall pattern of differences between maternal and cord blood showed a highly significant difference for all six viruses. Analysis regarding individual viruses showed significantly higher titers to CMV and RUB in cord blood, a higher titer to VZV in maternal blood, and similar levels of antibodies to EBV, HSV-1, and ADV in maternal and cord blood. Infants with one or more risk indicators (weight less than 3 kg, Apgar score less than or equal to 7, clinical jaundice, meconium-stained amniotic fluid, respiratory distress syndrome) were defined as "at risk." Infants free of such indicators were defined as "normal." Significantly lower antibody levels to all six viruses were found in both maternal and cord blood of the "at risk" as compared to the "normal" group, while the ratios between the maternal and cord blood levels remained similar. Birth defects were found to have no effect on antibody titers. These results indicate an efficient and selective transfer through the placenta of certain viral antibodies and the possible association of lower antibody production with the presence of risk indicators in the infants.

Fixation-induced cyst-like spaced in the brains of rabbit foetuses

During teratologic trials, routine investigations of 4261 brains from rabbit foetuses, fixed in Bouin's solution and sectioned by Wilson's free-hand razor blade technique, revealed cyst-like spaces in the brains of 164 foetuses (3.8%). The cyst-like spaces, characterised by the absence of an epithelial or endothelial lining, were usually solitary and occurred mainly in the massa intermedia of the thalamus. The spaces were found almost as ofter in control foetuses as in those from treated animals. On the basis of histologic examination and different fixation techniques, involving a further 1430 foetuses, these cyst-like spaces, previously interpreted as strain specific brain malformations, can be regarded as fixation artefacts.

Non-Mendelian development defects: animal models and implications for research into human disease

The major groups of malformations in man are polygenic in origin but this review deals only with defects due to non-Mendelian factors. Animal models that help in identifying the causes and in understanding the numerous and often subtle mechanisms of human malformations are of particular value. Many chemicals, physical agents, and nutritional deficiencies affect experimental species but few are teratogenic for domestic animals and even fewer for man. The known fetopathic viruses of animals and man cross the placenta to cause chronic, nonlethal fetal damage without harm to the mother. Ionizing radiations are teratogenic for all species and hyperthermia for many, but the role of the latter in human development is uncertain. The identification of more animal species with spontaneous or induced defects comparable to those found in man and of additional causative teratogens will increase the resources available for research into the causes and mechanisms of abnormal development in man. No animal species is ideal in teratological research but each has its virtues. This report comments on the present status of research in teratology and the trends that might profitably be followed in the future.

Congenital abnormalities in newborn lambs after infection of pregnant sheep with Akabane virus

Akabane virus (a Bunyavirus) has been associated with epizootics of congenital deformities in cattle, sheep, and goats. Experimental studies using mouse-adapted virus inoculated intravenously into pregnant sheep gave an inapparent infection. Neutralizing antibodies were detected on day 5, and peaks in the titer were seen at days 10 and 48. Ewes infected at day 30 to 36 of pregnancy produced five (31% incidence) deformed lambs. Sera from four of these possessed neutralizing antibodies to Akabane virus before ingesting colostrum. Two lambs had arthrogryposis, hydranencephaly, kyphosis, scoliosis, and brachygnathia; one had micrencephaly; and the other two had porencephaly. The two lambs with arthrogryposis and hydranencephaly also had extensive lesions in other tissues. In the spinal cord there was a marked decrease in the number of ventral horn neurones and a depletion of myelin. Skeletal muscles showed marked atrophy. The medulla of the thymus possessed large Hassall's corpuscles and a reduced number of thymocytes in the cortex. It would appear that the pathogenic effects of Akabane virus are related to the gestational age (30 to 36 days) at which the fetus is infected. Akabane virus can now be included in the growing list of teratogenic viruses and provides an interesting system for studying such congenital diseases.

Rapid separation of immunoglobulin M from immunoglobulin G antibodies for reliable diagnosis of recent rubella infections

Chromatography on controlled pore glass was adapted for the separation of immunoglobulin M (IgM) and immunoglobulin G (IgG) rubella antibodies from 0.3-ml samples of human serum. An extremely sharp separation of IgM from IgG antibodies could be obtained within 40 min. Nonspecific inhibitors were removed before chromatography by precipitation with high-molecular-weight dextran sulfate, and the titer of rubella antibodies in the different classes of immunoglobulins were assayed with a modified hemagglutination inhibition technique. The combination of these methods is recommended for routine tests. It permits an accurate diagnosis of recent rubella infection within a few hours.

Influence of time of infection during pregnancy with coxsackievirus B3 on maternal pathology and foetal growth in mice

Coxsackievirus B3 causes foetal wastage and growth retardation in mice which may be attributed to the action of the virus in destroying the maternal exocrine pancreas. Injection of virus on Day 4 or 8 of gestation caused greater foetal wastage than injection at 12 days. Foetal and placental weights in infected animals were less than in the controls but did not vary according to the time of infection. Little support is offered for the view that the mouse foetus differs in its susceptibility to Coxsackievirus B3 according to the stage in gestation of infection.