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Infection during pregnancy is common and the developing fetal brain is vulnerable to vertical transmission due to immaturity of the fetal immune system. Infection is a major cause of multiple organ abnormalities, including the neuraxis, due to the neurotropism of the infectious agents. This review sets out to give an overview of fetal infection, review the general principles of the nature and timing of the infectious insult with respect to outcomes, review the neuroimaging of infection by ultrasound and magnetic resonance imaging (MRI), and review the various pathogens involved, including the two most common, cytomegalovirus (CMV) and Toxoplasma, and also other common viral and nonviral infections.

The human pathogen CMV, is a major cause of morbidity and mortality in immunocompromised hosts. The CD8+ class I-restricted CTL response to CMV assists in preventing progression of CMV infection to life-threatening disease; however, the viral Ag recognized by CD8+ CTL are not well characterized. In general, virus-specific CTL recognize endogenously synthesized viral proteins processed and presented associated with class I MHC molecules. Although proteins or inactivated virions have been experimentally delivered to the cytoplasm to result in class I MHC presentation, this mode of Ag delivery to the class I processing pathway after natural viral entry has not been documented in humans. Our data demonstrate that the CMV-specific class I-restricted CTL response in individuals latently infected with CMV is predominantly specific for selected structural virion proteins introduced into the cell after viral penetration and efficient recognition occurs in the absence of de novo viral gene expression. This CTL response may provide a biological advantage for limiting the spread of infection after CMV reactivation because infected cells are lysed before viral assembly.

Truncated versions of the human cytomegalovirus (CMV) strain Towne glycoprotein B (gB) gene were stably expressed in CHO cell lines. The calcium-specific ionophore A23187 inhibited proteolytic cleavage of C-terminal-truncated gB expressed by cell line 67.77. These inhibition studies also showed that the 93-kilodalton cleavage product most likely represents the N-terminal cleavage fragment of gB. The ionophore carboxyl cyanide m-chlorophenyl-hydrazone was used to show that proteolytic cleavage of gB did not occur in the endoplasmic reticulum. Two-dimensional polyacrylamide gel electrophoresis demonstrated that the N- and C-terminal cleavage products of gB remained associated by disulfide linkages after cleavage. Expression studies using constructs in which 80% or all of the N terminus was deleted demonstrated that the N terminus was required for secretion of the gB molecule. The amino acid sequence at the site of cleavage was shown to be critical for cleavage by a cellular protease. Our results indicate that an arginine-to-threonine change at either amino acid 457 or 460, a lysine-to-glutamine change at amino acid 459, or all three substitutions together block gB cleavage. The effect on proteolysis of the arginine-to-threonine amino acid change at residue 457 (position -4 relative to the cleavage site) demonstrated that a basic pair of amino acids at the endoproteolytic processing site is not the only requirement in cis for gB cleavage.

Congenital cytomegalovirus (CMV) infection occurs in approximately 1% of newborns in the United States. A phase II evaluation was done of ganciclovir for the treatment of symptomatic congenital CMV infection. Daily doses of 8 or 12 mg/kg were administered in divided doses at 12-h intervals for 6 weeks. Clinical and laboratory evaluations sought evidence of toxicity, quantitative virologic responses in urine, plasma drug concentrations, and clinical outcome. A total of 14 and 28 babies received 8 and 12 mg/kg/day, respectively. Five additional babies received ganciclovir on a compassionate plea basis. Significant laboratory abnormalities included thrombocytopenia (or = 50,000/mm3) in 37 babies and absolute neutropenia (or = 500 mm3) in 29 babies. Quantitative excretion of CMV in the urine decreased; however, after cessation of therapy, viruria returned to near pretreatment levels. Hearing improvement or stabilization occurred in 5 (16%) of 30 babies at 6 months or later, indicating efficacy.

Cytomegalovirus (CMV) retinitis is a common, devastating complication of AIDS. Strict host specificity of human CMV (HCMV), has limited the study of the virus. The purpose of this research was to create a model that allowed the in vivo infection of human retinal tissue with HCMV.Small fragments of 13-week human fetal retina were transplanted into the anterior chambers of immune-deficient mice. One week later, 15 of 30 grafts were inoculated with HCMV. Infected and noninfected specimens were compared for histopathologic changes at 14, 30, and 60 days at light and electron microscopic levels. Histochemistry was performed to characterize: level of graft differentiation, range of viral replication cycle, and effects on neuronal, glial, and monocytic elements of the retina.At 30 and 60 days, grafts were well differentiated histologically and histochemically. The infected grafts showed numerous large cells containing intranuclear and intracytoplasmic inclusions. Ultrastructural examination revealed viral particles within cytoplasm and nuclei. Infected cells expressed proteins representative of all phases of the HCMV replication cycle. Most HCMV-infected cells expressed the neuronal marker, protein gene product 9.5. In a second series of experiments, tissue from one graft harvested at 45 days postinfection was used to recover HCMV in fibroblast cultures and also used successfully to passage the virus to two control grafts.This model allows HCMV to actively infect and replicate within highly differentiated human neural tissue. It produces pathology characteristic of CMV-infected neural tissue in a time course suitable for long-term study. The nature of this model will allow the study of: the replication properties of HCMV in nervous tissue, the specific effects of HCMV on the human retina, the interaction of HCMV with other viruses, e.g., HIV, and various anti-viral therapies.

The human pathogen CMV, is a major cause of morbidity and mortality in immunocompromised hosts. The CD8+ class I-restricted CTL response to CMV assists in preventing progression of CMV infection to life-threatening disease; however, the viral Ag recognized by CD8+ CTL are not well characterized. In general, virus-specific CTL recognize endogenously synthesized viral proteins processed and presented associated with class I MHC molecules. Although proteins or inactivated virions have been experimentally delivered to the cytoplasm to result in class I MHC presentation, this mode of Ag delivery to the class I processing pathway after natural viral entry has not been documented in humans. Our data demonstrate that the CMV-specific class I-restricted CTL response in individuals latently infected with CMV is predominantly specific for selected structural virion proteins introduced into the cell after viral penetration and efficient recognition occurs in the absence of de novo viral gene expression. This CTL response may provide a biological advantage for limiting the spread of infection after CMV reactivation because infected cells are lysed before viral assembly.

An epitope common to all classes of murine leukemia viruses (MuLVs) was detected by reactivity of MuLVs with a rat monoclonal antibody (MAb) termed 83A25. The antibody is of the immunoglobulin G2a isotype and was derived after fusion of NS-1 myeloma cells with spleen cells from a Fischer rat immunized with a Friend polytropic MuLV. The antibody reacted with nearly all members of the ecotropic, polytropic, xenotropic, and amphotropic classes of MuLVs. Unreactive viruses were limited to the Friend ecotropic MuLV, Rauscher MuLV, and certain recombinant derivatives of Friend ecotropic MuLV. The presence of an epitope common to nearly all MuLVs facilitated a direct quantitative focal immunofluorescence assay for MuLVs, including the amphotropic MuLVs for which no direct assay has been previously available. Previously described MAbs which react with all classes of MuLVs have been limited to those which react with virion core or transmembrane proteins. In contrast, protein immunoblot and immunoprecipitation analyses established that the epitope reactive with MAb 83A25 resides in the envelope glycoproteins of the viruses. Structural comparisons of reactive and nonreactive Friend polytropic viruses localized the epitope near the carboxyl terminus of the glycoprotein. The epitope served as a target for neutralization of all classes of MuLV with MAb 83A25. The efficiency of neutralization varied with different MuLV isolates but did not correlate with MuLV interference groups.

Late in the course of Friend virus (FV)-induced erythroleukemia, leukemic spleen cells express a cell surface retroviral gp70 envelope protein not detected during the early proliferative phase of the disease. Characterization of this gp70 revealed it was unrelated to the input Friend murine leukemia virus (F-MuLV), but antigenically similar to a unique subset of endogenous xenotropic viruses. This gp70 was expressed by murine erythroleukemia cell lines but has not been identified on cell lines of other lineages. A monoclonal antibody (18-6) specifically reactive with this polypeptide was used to examine hematopoietic organs of normal uninoculated mice. This antibody detected a gp70 expressed by a majority of erythroid cells in fetal liver and by a small but significant percentage of normal adult spleen and bone marrow cells. Increased erythropoietic activity induced by treatment of adult mice with phenylhydrazine ( PHZ ) resulted in a seven- to eightfold increase in the frequency of spleen and bone marrow cells expressing this gp70. Peptide map analysis indicated that the 18-6 reactive gp70 expressed by Friend erythroleukemia cells and by cells from normal fetal liver were structurally identical. These results suggested that this unique gp70 was an erythroid-specific differentiation antigen.

Protein kinase activity was detected in immunoprecipitates of human cytomegalovirus virions and infected cells by using a monoclonal antibody directed against an abundant 68,000-dalton virion structural protein. Purification of this protein by electrophoresis confirmed that the kinase activity was associated with this protein. The kinase activity was dependent on divalent cations (Mg2+, Mn2+) and cyclic nucleotide independent and exhibited optimal activity at pH 7 to 8. The kinase phosphorylated threonine and serine but not tyrosine.

✓ Venous air embolism can usually be detected by the use of a precordial Doppler ultrasound monitor at an air infusion rate as low as 0.015 ml/kg/min, and consistently at a rate of 0.021 ml/kg/min. This is in contrast to previously reported thresholds wherein the first physiological change, a gasp, occurs at 0.36 ml/kg/min, electrocardiographic changes first take place at 0.60 ml/kg/min, drop in blood pressure at 0.69 ml/kg/min, increased central venous pressure at 0.40 ml/kg/min, and end-tidal CO2 decreases at 0.42 ml/kg/min. The first change in heart sounds monitored through an esophageal stethoscope is not detectable until an air infusion rate of 1.70 ml/kg/min, and the classical mill-wheel murmur does not occur until 1.96 ml/kg/min. This demonstrates that Doppler ultrasound can detect venous air embolism before the earliest physiological changes, in contrast to most other methods which do not detect venous air embolism until after cardiopulmonary changes have become well established.

The envelope of human cytomegalovirus has been reported to contain between three and eight glycoproteins. Major constituents of the envelope include two abundant glycoproteins with estimated molecular weights of 55,000 (gp55) and 116,000 (gp116). These two glycoproteins have been shown to exist as a disulfide-linked complex (gp55-116) within the envelope of mature virions. Utilizing a panel of monoclonal antibodies reactive with the gp55-116 complex, we characterized the synthesis and processing of these two virion proteins. Infected cells were shown to contain two glycosylated proteins of 160,000 and 150,000 daltons as well as the mature gp55 and gp116. Pulse-chase analysis indicated that gp150 was a precursor protein of gp160. The mature gp55 and gp116 were generated, in turn, by cleavage of gp160. Antigenic and structural analysis revealed that gp55 and gp116 shared little structural homology and no detectable antigenic cross-reactivity. The results of this study are discussed in relation to the synthesis of envelope proteins of other herpesviruses.

We studied 16 218 pregnant women from two income groups to determine the incidence of primary cytomegalovirus (CMV) infection and its consequences for the offspring. In the high-income group, 64.5% of the women were seronegative for CMV and 1.6% had primary CMV infection. In the low-income group, only 23.4% of the women were seronegative for CMV, but 3.7% experienced a primary infection. The rate of transmission in utero was similar in the two groups (39% and 31%). Congenital infections were more frequent in the low-income group; however, primary CMV accounted for 25% of the congenital infections in this group, in contrast to 63% of the high-income cases. Infections acquired early and late in gestation had similar rates of transmission in utero, but three infants (8%) with symptomatic congenital infection and five infants (13.5%) who have developed significant handicaps were exposed in the first half of pregnancy. Primary CMV infection during pregnancy poses a 30% to 40% risk of intrauterine transmission and adverse outcome is more likely when infection occurs within the first half of gestation.

During the course of progressive Friend virus-induced leukemia in Rfv-3r/s mice, antiviral antibody caused a marked reduction in the frequency of leukemic spleen cells releasing infectious virus. We investigated the mechanism of this antibody-induced alteration of leukemia cell phenotype in a series of passive transfer experiments using monoclonal antiviral antibodies. Our results indicated that two IgG2a anti-gp70 cytotoxic antibodies could reduce the frequency of virus-producing cells within the leukemic spleen as well as maintain the virus-nonproducing phenotype once it was established. IgG2a and IgG2b monoclonal anti-p 15 antibodies, IgM, and IgA anti-gp70 antibodies, and an IgG3 anti-p 15(E) antibody were not effective. The mechanism of this phenotypic alteration appeared to involve an antibody-mediated cytostasis of virus-producing leukemia cells with the subsequent over-growth of virus-nonproducing cells. The maintenance of the virus-nonproducing phenotype was dependent on the presence of anti-gp70 antibodies capable of neutralizing and clearing infectious F-MuLV in vivo. The presence of these neutralizing antibodies appeared to prevent reinfection of virus-nonproducing cells and therefore interfered with reversion to the virus-producing phenotype.