The correlation between Toxoplasma gondii infection and prenatal depression in pregnant women.

Previous studies have demonstrated that latent toxoplasmosis is associated with neuropsychiatric disorders. We evaluated the correlation between Toxoplasma gondii infection and prenatal depression. In this case-control study, we enrolled 116 depressed pregnant women and 244 healthy controls. The Edinburgh Postpartum Depression Scale (EPDS) was used to evaluate the depression symptom severity in study participants. All participants were screened for the anti-Toxoplasma IgG by enzyme-linked immunosorbent assay. Seroprevalence of T. gondii did not significantly differ between the depressed pregnant women and healthy controls (OR = 1.4; 95 % CI = 0.9-2.19; P = 0.142). T. gondii IgG titer was significantly higher in depressed women (18.6 ± 10.9 IUs) than those in the control group (13.6 ± 8.1 IUs) (z = -5.36, P < 0.001). The T. gondii-positive depressed women showed a positive correlation of T. gondii IgG titer with the EPDS scores (r = 0.52; P < 0.01). The mean EPDS score was also significantly higher in the T. gondii-positive depressed women (20.7 ± 2.7) compared with the controls (18.36 ± 2.7) (P < 0.001). The results obtained from the current study revealed that T. gondii infection might affect susceptibility to depression and severity of depressive symptoms in pregnant women, particularly in those patients who have high antibody titers. Further study is required to fully elucidate the characteristics and mechanisms of this association.

Prediction of spontaneous preterm delivery in women with threatened preterm labour: a prospective cohort study of multiple proteins in maternal serum.

OBJECTIVE: To analyse whether specific proteins in maternal serum and cervical length, alone or in combination, can predict the likelihood that women with intact membranes with threatened preterm labour will deliver spontaneously within 7 days of sampling. DESIGN: Cohort study. SETTING: Sahlgrenska University Hospital, Gothenburg, Sweden. POPULATION: Women at between 22 and 33 weeks of gestation with threatened preterm labour (n = 142) admitted to the Sahlgrenska University Hospital, Gothenburg, Sweden, in 1995-2005. METHODS: Maternal serum was tested for 27 proteins using multiplex xMAP technology. Individual levels of each protein were compared, and calculations were performed to investigate potential associations between different proteins, cervical length and spontaneous preterm delivery. Receiver operating characteristic curves were used to find the best cut-off values for continuous variables in relation to spontaneous preterm delivery within 7 days of sampling. Prediction models were created based on a stepwise logistic regression using binary variables. MAIN OUTCOME MEASURE: Spontaneous preterm delivery within 7 days. RESULTS: In order to determine the best prediction model, we analysed models of serum proteins alone, cervical length alone, and the combination of serum proteins and cervical length. We found one multivariable combined model through the data analysis that more accurately predicted spontaneous preterm delivery within 7 days. This model was based on serum interleukin-10 (IL-10) levels, serum RANTES levels and cervical length (sensitivity 74%, specificity 87%, positive predictive value 76%, negative predictive value 86%, likelihood ratio 5.8 and area under the curve 0.88). CONCLUSIONS: A combination of maternal serum proteins and cervical length constituted the best prediction model, and would help determine whether women with threatened preterm labour are likely to deliver within 7 days of measurement.

Dysregulated biomarkers induce distinct pathways in preterm birth.

OBJECTIVE: To document racial disparity in biomarker concentrations in maternal/fetal plasma and amniotic fluid between African Americans and European Americans with spontaneous preterm birth (PTB; cases) and normal term birth (controls), and their contribution to distinct pathophysiological pathways of PTB. DESIGN: Nested case-control study. SETTING: The Perinatal Research Center, Nashville, Tennessee, USA. SAMPLE: Maternal and fetal plasma and amniotic fluid samples were collected from 105 cases (59 African American and 46 European American) and 86 controls (40 African American and 46 European American). METHODS: Thirty-six biomarkers were analysed using the protein microarray approach. MAIN OUTCOME MEASURES: Differences in biomarker concentrations between cases and controls of different races in maternal, fetal and intra-amniotic compartments, and the risk of PTB. Dysregulated biomarker-induced PTB pathways associated with PTB in each race were determined using ingenuity pathway analysis (IPA). RESULTS: Racial disparity was observed in biomarker concentrations in each compartment between cases and controls: amniotic fluid, IL8 and MIP1α differed between case and controls in European Americans, whereas ANGPT2, Eotaxin, ICAM-1, IL-1ß, IL1RA, RANTES and TNFα differed between case and controls in African Americans. In both races the FAS ligand, MCP-3 and TNFR-I differed between cases and controls. For fetal plasma, ANGPT2, Eotaxin, FGF basic, ICAM-1, IGF-I, IL10, IL-1ß, IL2, IP10 KGF, MCP-3, MIP1α, PDGF-BB, TGFα, TGFß1, TIMP1, TNFα, TNFR-I, TNFR-II and VEGF differed between cases and controls in European Americans, whereas only MMP7 differed between cases and controls in African Americans. IL-8 differed between cases and controls in both races. For maternal plasma, IL1RA, MMP7 and VEGF differed between cases and controls in European Americans, whereas ANGPT2, FGF basic, IL-1ß, IL5, IL6R, KGF, MCP-3, MIP1α, TIMP1 and TNFα differed between cases and controls in African Americans. ANG, IL8 and TNFR-I differed between cases and controls in both races. CONCLUSIONS: We conclude that: (1) biomarker concentrations in maternal, fetal and intra-amniotic compartments differ between cases and controls; (2) there is racial disparity in the biomarker profile in each of the compartments; (3) substantial numbers of dysregulated fetal plasma biomarkers contribute to PTB in European Americans, whereas maternal plasma biomarkers contribute to PTB in African Americans; and (4) both inflammation and haematological functions are associated with PTB in European Americans, but maternal proinflammatory changes dominate PTB in African Americans. Biomarker analyses document racial disparity and the distinct pathophysiological contributions from different compartments that can determine pregnancy outcome.

Interrelationship of cytokines, hypothalamic-pituitary-adrenal axis hormones, and psychosocial variables in the prediction of preterm birth.

BACKGROUND/AIMS: To examine the relationship of biological mediators (cytokines, stress hormones), psychosocial, obstetric history, and demographic factors in the early prediction of preterm birth (PTB) using a comprehensive logistic regression model incorporating diverse risk factors. METHODS: In this prospective case-control study, maternal serum biomarkers were quantified at 9-23 weeks' gestation in 60 women delivering at <37 weeks compared to 123 women delivering at term. Biomarker data were combined with maternal sociodemographic factors and stress data into regression models encompassing 22 preterm risk factors and 1st-order interactions. RESULTS: Among individual biomarkers, we found that macrophage migration inhibitory factor (MIF), interleukin-10, C-reactive protein (CRP), and tumor necrosis factor-alpha were statistically significant predictors of PTB at all cutoff levels tested (75th, 85th, and 90th percentiles). We fit multifactor models for PTB prediction at each biomarker cutoff. Our best models revealed that MIF, CRP, risk-taking behavior, and low educational attainment were consistent predictors of PTB at all biomarker cutoffs. The 75th percentile cutoff yielded the best predicting model with an area under the ROC curve of 0.808 (95% CI 0.743-0.874). CONCLUSION: Our comprehensive models highlight the prominence of behavioral risk factors for PTB and point to MIF as a possible psychobiological mediator.

Schizophrenia and viral infection during neurodevelopment: a focus on mechanisms.

The task of defining schizophrenia pathogenesis has fascinated and frustrated researchers for nearly a century. In recent years, unprecedented advances from diverse fields of study have given credence to both viral and developmental theories. This review considers possible mechanisms by which viral and developmental processes may interact to engender schizophrenia. Many of the current controversies in schizophrenia pathogenesis are reviewed in light of the viral hypothesis, including: epidemiological findings and the role of a genetic diathesis, phenotype heterogeneity, abnormalities in excitatory and inhibitory neurotransmitter systems, anomalous cerebral latereralization, and static vs progressive disease. The importance of animal models in elucidating the impact of viral infections on developing neurons is illustrated by recent studies in which neonatal rats are infected with lymphocytic choriomeningitis virus in order to examine alterations in hippocampal circuitry. Finally, consideration is given to a new hypothesis that some cases of schizophrenia could be instigated by a viral infection that disrupts developing inhibitory circuits, consequently unleashing glutamatergic neurotransmission leading to selective excitotoxicity, and a degenerative disease course.

Higher than normal plasma interleukin-6 concentrations in cancer patients with depression: preliminary findings.

OBJECTIVE: This study investigated whether cancer patients with and without major depression exhibit immune system abnormalities similar to those reported in medically healthy, depressed subjects without cancer. METHOD: The study subjects consisted of patients diagnosed with pancreatic, esophageal, or breast cancer. Other groups consisted of subjects with major depression (without cancer) and healthy comparison subjects. Subjects' diagnoses were made with the Structured Clinical Interview for DSM-III-R. Severity of depression was measured with the Hamilton Depression Rating Scale. Plasma concentrations of interleukin-6 (IL-6) and postdexamethasone cortisol were measured. RESULTS: Cancer patients with depression had markedly higher plasma concentrations of IL-6 than healthy comparison subjects and cancer patients without depression. Although significant correlations were found between Hamilton depression scale scores and plasma concentrations of postdexamethasone cortisol, no significant correlations were found between plasma IL-6 and postdexamethasone cortisol concentrations. CONCLUSIONS: Higher than normal plasma IL-6 concentrations were associated with a diagnosis of major depression in cancer patients. IL-6 may contribute to sickness behavior that has overlapping symptoms with major depression.

The steroid receptor antagonists RU40555 and RU486 activate glucocorticoid receptor translocation and are not excreted by the steroid hormones transporter in L929 cells.

RU40555 is a recently available glucocorticoid receptor (GR) antagonist that differs from RU486 by a methyl radical. We have used the mouse fibroblast cell line L929 to study the in vitro effects of RU40555 on GR translocation and function and on the membrane steroid hormones transporter. The results showed that: 1) RU40555 competed for the binding of labelled dexamethasone (Dex) with a K(i) of 2.4 nM; 2) both RU40555 and RU486 were equally potent inhibitors of Dex-induced GR-mediated gene transcription; 3) maximum GR translocation induced by micromolar concentrations of Dex and the GR antagonists was approximately 30-55% loss in the cytoplasmic GR and approximately 40-90% increase in the nuclear GR (assessed by GR immunostaining in cytoplasm and nucleus and western blots of immunoprecipitated GR protein in cytosolic and nuclear fractions) and was similar for the two antagonists; 4) at nanomolar concentrations, RU40555 and RU486 induced more GR translocation than Dex (assessed by [(3)H]Dex binding and western blot of immunoreactive GR in the same cytosolic homogenates); 5) blocking the steroids membrane transporter with verapamil (100 microM) in the presence of Dex (10 nM) increased GR translocation to levels similar to those induced by RU40555 (10 nM) and RU486 (10 nM) alone; 6) verapamil did not affect GR translocation in the presence of RU40555 or RU486. These data demonstrate similar quantitative effects on GR translocation by RU486 and the new GR antagonist, RU40555. Moreover, RU40555, like RU486, is an effective GR antagonist. Finally, there is no evidence that the intracellular concentrations of RU40555 or RU486 are regulated by the steroids membrane transporter in L929 cells.

Viral infection of developing GABAergic neurons in a model of hippocampal disinhibition.

Mechanisms by which perinatal viral infections can disrupt hippocampal development and cause selective neuronal death may have implications for temporal lobe epilepsy and schizophrenia. Despite abnormalities of inhibitory interneurons in these diseases, the causal relationships between such neurotransmitter changes and viral infections remain unclear. This relationship was examined in a model in which rats, infected with lymphocytic choriomeningitis virus (LCMV) as neonates, manifest a gradual loss of hippocampal dentate granule cells and neuronal hyperexcitability. The current data demonstrate that GABAergic interneurons are dual immunostained for LCMV antigens prior to the loss of dentate granule cells, supporting the hypothesis that LCMV may disrupt developing inhibitory circuits causing unbalanced excitatory neurotransmission and the eventual death of dentate granule cells due to excitotoxicity.

Lymphocytic responses and the gradual hippocampal neuron loss following infection with lymphocytic choriomeningitis virus (LCMV).

Infection of rats with LCMV is known to cause a bi-phasic neurodegeneration characterized by acute T lymphocyte-mediated cerebellar damage, followed by gradual hippocampal neuron loss that occurs by an undefined mechanism. We found infiltration of CD8 + T-cells (but not CD4 + or NK cells) in the hippocampus which correlated with the acute phase, but not the chronic hippocampal degenerative phase. While immunosuppression of T lymphocytes protected the cerebellum and revealed the infection of corticohippocampal glia, the degeneration in the hippocampus was unabated. These data suggest that T lymphocytes control glial infection and mediate degeneration in the cerebellum but not the hippocampus.

The proinflammatory cytokine, interleukin-1alpha, reduces glucocorticoid receptor translocation and function.

Proinflammatory cytokines have been shown to influence the expression and function of the glucocorticoid receptor (GR). Specifically, several studies have found that cytokines induce a decrease in GR function, as evidenced by reduced sensitivity to glucocorticoid effects on functional end points. To investigate the potential mechanism(s) involved, we examined the impact of the proinflammatory cytokine, interleukin-1alpha (IL-1alpha), on 1) GR translocation from cytoplasm to nucleus using GR immunostaining, 2) cytosolic radioligand GR binding, and 3) GR-mediated gene transcription in L929 cells stably transfected with the mouse mammary tumor virus-cholamphenicol acetyltransferase reporter gene. L929 cells were treated with IL-1alpha (100 and 1000 U/ml) for 24 h in the presence or absence of dexamethasone (Dex; 10 nM to 1 microM). IL-1alpha inhibited Dex-induced GR translocation and alone induced GR up-regulation. Pretreatment with IL-1alpha followed by Dex treatment for 1.5 h led to about 20% inhibition of Dex-induced GR-mediated gene transcription, whereas coincubation of IL-1alpha plus Dex for 24 h inhibited Dex-induced GR-mediated gene activity up to 42%. The latter effect was reversed by the IL-1 receptor antagonist. These results suggest that cytokines produced during an inflammatory response may induce GR resistance in relevant cell types by direct effects on the GR, thereby providing an additional pathway by which the immune system can influence the hypothalamic-pituitary-adrenal axis.

Effects of cytokines on glucocorticoid receptor expression and function. Glucocorticoid resistance and relevance to depression.

Our data indicate that the proinflammatory cytokine, IL-1alpha inhibits GR translocation and hormone-induced GR-mediated gene transcription, and, in conjunction with previous in vivo and in vitro studies, can be interpreted to suggest that cytokines have the capacity to contribute to glucocorticoid resistance and thus the pathophysiology of depression. In addition, data from our mouse viral studies in glucocorticoid deficient animals demonstrate that endogenous glucocorticoids modulate a delicate balance between viral defense and cytokine toxicity. Finally, the antidepressant, DMI, has been found to enhance GR translocation and GR-mediated gene transcription and thus may provide a useful strategy for adjusting neuroendocrine setpoints in vivo. Taken together, these findings suggest that factors which modulate glucocorticoid action (e.g. cytokines and antidepressants) will be relevant contributors to disease expression including behavioral toxicity and sickness behavior.

Endogenous glucocorticoids protect against cytokine-mediated lethality during viral infection.

Certain cytokines activate the hypothalamic-pituitary-adrenal axis for glucocorticoid release, and these hormones can protect against cytokine-mediated pathologies. However, endogenous activation of such a pathway has not been established during infections. A prominent glucocorticoid response peaks 36 h following murine CMV (MCMV) infection, coincident with circulating levels of the cytokines IL-12, IFN-gamma, TNF, and IL-6, and dependent on IL-6 for maximal release. These studies examined functions of the hormone induction. Mice rendered glucocorticoid deficient by adrenalectomy were more susceptible than intact mice to MCMV-induced lethality, and the increased sensitivity was reversed by hormone replacement. Lack of endogenous glucocorticoids resulted in increases in IL-12, IFN-gamma, TNF, and IL-6 production, as well as in mRNA expression for a wider range of cytokines, also including IL-1 alpha and IL-1 beta. Viral burdens did not increase, and actually decreased, in the livers of glucocorticoid-deficient mice. TNF, but not IFN-gamma, was required for increased lethality in the absence of endogenous hormone. These results conclusively demonstrate the importance of induced endogenous glucocorticoids in protection against life-threatening effects resulting from infection-elicited cytokine responses. Taken together with the dependence on induced IL-6, they document existence of an immune system-hypothalamic-pituitary-adrenal axis pathway for regulating endogenous responses to viral infections.

Glucocorticoid receptors are differentially expressed in the cells and tissues of the immune system.

Cytosolic glucocorticoid receptor (GR) binding studies on immune tissues demonstrate that the thymus exhibits three to four times higher levels of GR protein than the spleen. High levels of GR are consistent with the exquisite sensitivity of the thymus to glucocorticoid exposure. Nevertheless, whole cell binding studies reveal similar levels of GR in immature thymic T lymphocytes and more mature, splenic T lymphocytes. Moreover, whole cell binding techniques indicate that neutrophils (which represent roughly 30% of splenic leukocytes) exhibit higher GR than both T and B lymphocytes, further contradicting results from cytosolic binding studies. To address these inconsistencies, GR protein was assessed in immune cells and tissues using cytosolic radioligand binding. Western blot analysis, and immunocytochemistry. Consistent with previous cytosolic receptor binding studies on immune tissue homogenates, thymic T cells were found to have higher levels of GR than T cells isolated from the spleen. In addition, neutrophils were found to have fewer GR than lymphocytes and monocytes. These results indicate a meaningful relationship between receptor expression and known sensitivity to glucocorticoids.

Steroid-independent translocation of the glucocorticoid receptor by the antidepressant desipramine.

The glucocorticoid receptor (GR) is a ligand-regulated transcription factor that in its unactivated form resides primarily in the cytoplasm. After being bound by steroid, the GR undergoes a conformational change and translocates to the nucleus, where it influences gene transcription. Because the GR mediates negative feedback exerted by circulating glucocorticoid hormones on the hypothalamic-pituitary-adrenal (HPA) axis, it has been hypothesized that abnormalities in GR expression and/or function may underlie the HPA axis hyperactivity described in patients with major depression. In further support of this hypothesis, animal studies have shown that long term in vivo treatment with antidepressants enhances glucocorticoid feedback inhibition, possibly through a direct effect on the GR. To examine this latter possibility, we evaluated translocation of the GR from the cytoplasm to the nucleus after 24-hr in vitro treatment of L929 cells (mouse fibroblasts) with the tricyclic antidepressant desipramine (0.1-10 microM) in the presence or absence of the synthetic steroid dexamethasone. In addition, GR-mediated gene transcription was measured with the use of L929 cells stably transfected with the mouse mammary tumor virus-chloramphenicol acetyltransferase reporter gene. Desipramine was found to (i) induce GR translocation from the cytoplasm to the nucleus in the absence of steroids (with no effect alone on GR-mediated gene transcription) and (ii) potentiate dexamethasone-induced GR translocation and dexamethasone-induced GR-mediated gene transcription. Treatment with desipramine for 24-96 hr had no effect on the expression of GR protein as measured by cytosolic radioligand receptor binding. We suggest that one important aspect of the effects of antidepressants in vivo may be to facilitate GR-mediated feedback inhibition on the HPA axis, by facilitating GR translocation and function, and thereby reverse glucocorticoid hypersecretion in depression.

1996 Curt P. Richter Award. Effects of viral infection on corticosterone secretion and glucocorticoid receptor binding in immune tissues.

During an immune challenge it has been suggested that responding cells secrete cytokines which then stimulate the release of glucocorticoids. Glucocorticoids, in turn, are believed to bind to their receptors in target immune tissues and provide feedback inhibition on evolving immune responses. The foundations for this hypothesis have been drawn primarily from studies on animal models of autoimmune and/or inflammatory processes, and the relevance of these glucocorticoid-immune interactions to viral infections has not been extensively examined. Accordingly, we infected mice with lymphocytic choriomeningitis virus (LCMV) and measured plasma corticosterone and cytosolic glucocorticoid receptor (GR) binding at multiple time points throughout the day and throughout infection (days 3, 5, 7 and 10 post infection). Despite a vigorous immune response to this virus, LCMV infection was associated with minimal and transient increases in corticosterone secretion. Interestingly, however, significant decreases in cytosolic GR were found in immune tissues. Receptor decreases were characterized by a significant decrease in GR binding during the diurnal rise in corticosterone in the spleen and thymus of infected but not uninfected animals on days 5-10 post infection. In addition, in the morning on these days, GR binding in the spleen of infected mice was decreased compared to uninfected control mice. Following an acute injection of corticosterone on day 7 post infection, LCMV-infected animals exhibited a significantly greater decrease in splenic GR binding than uninfected control mice, suggesting an increased sensitivity to corticosterone in infected animals. No changes were found in the affinity (Kd) of the GR during infection, nor was there evidence of an infection-associated decrease in plasma corticosteroid binding globulin. The appearance of significant GR changes in the spleen and thymus, in the absence of significant elevations in corticosterone or decreases in its binding protein, suggests that cytokines and/or other factors produced within the immune tissues during infection either directly influenced GR number and/or function or influenced the local availability of corticosterone. Taken together, the results indicate that interactions between the neuroendocrine and immune systems can be modified at the level of the GR in the context of an ongoing immune response such as during a viral infection.

Characterization of early cytokine responses and an interleukin (IL)-6-dependent pathway of endogenous glucocorticoid induction during murine cytomegalovirus infection.

Early infection with murine cytomegalovirus (MCMV) induces circulating levels of interleukin (IL)-12, interferon (IFN)-gamma, and tumor necrosis factor (TNF). Studies presented here further characterize these responses by defining kinetics and extending evaluation to include IL-1, IL-6, and glucocorticoids. IL-12 p40, IFN-gamma, TNF, IL-1alpha, and IL-6 were shown to be increased, but IL-1beta was undetectable, in serum of MCMV-infected mice. The IL-12 p40, IFN-gamma, TNF, and IL-6 responses were dramatic with peak levels reaching >150-10,000 pg/ml at 32-40 h after infection and rapidly declining thereafter. Glucocorticoid induction, peaking at 36 h and reaching 30-fold increases above control values, accompanied the cytokine responses. Mice with cytokine deficiencies or neutralized cytokine function demonstrated that IL-6 was the pivotal mediator of the glucocorticoid response, with IL-1 contributing to IL-6 production. The IL-6 requirement appeared to be specific for virus-type stimuli as the synthetic analogue of viral nucleic acid, polyinosinic-polycytidylic acid, also induced IL-6-dependent glucocorticoid release, but treatments with the bacterial product lipopolysaccharide and a non-immune physical restraint stressor elicited IL-6-independent responses. Collectively, the results identify IL-6 as a primary mediator of glucocorticoid induction, and elucidate specific pathways of interactions between immune and neuroendocrine systems during viral infection.

Persistent dentate granule cell hyperexcitability after neonatal infection with lymphocytic choriomeningitis virus.

Infection of neonatal Lewis rats with lymphocytic choriomeningitis virus (LCMV) produces distinct retinal, cerebellar, and hippocampal neuropathology. To understand the neurophysiological consequences of LCMV-induced hippocampal pathology, we studied evoked monosynaptic potentials and electro-encephalographic (EEG) activity in the dentate gyrus and CA1 and CA3 subfields of the hippocampus in vivo. Lewis rats were inoculated intracerebrally with LCMV at postnatal day 4. In rats studied 84-107 d postinfection, virus was cleared from the dentate gyrus and the number of dentate granule cells was decreased by 70%. No viral antigen or cell loss was apparent in CA1 or CA3. The hippocampal EEG of LCMV-infected rats 84-102 d postinfection was dominated by continuous theta. Although evoked potentials elicited in CA1 and CA3 by monosynaptic afferent stimulation revealed no differences between sham- and LCMV-infected rats, there was a site-specific dissociation of synaptic [population excitatory postsynaptic potential (pEPSP)] and cellular (population spike) responses and a suppression of GABA-mediated recurrent inhibition in the dentate gyrus of LCMV-infected rats. These findings indicate that GABA-mediated inhibition was markedly decreased in LCMV-infected rats. In support of this, parvalbumin-immunoreactive cell bodies and neuronal processes were decreased in LCMV-infected rats, suggesting that a subpopulation of GABA interneurons was affected. These findings indicate that abnormalities in synaptic function persist after clearance of infectious virus from the central nervous system and suggest that decreased inhibition subsequent to pathological sequence in a subpopulation of GABA interneurons may be implicated in the hyperexcitability of dentate granule cells.

Cytokine induction during T-cell-mediated clearance of mouse hepatitis virus from neurons in vivo.

To investigate the mechanism by which viruses are cleared from neurons in the central nervous system, we have utilized a mouse model involving infection with a neurotropic variant of mouse hepatitis virus (OBLV60). After intranasal inoculation, OBLV60 grew preferentially in the olfactory bulbs of BALB/c mice. Using in situ hybridization, we found that viral RNA localized primarily in the outer layers of the olfactory bulb, including neurons of the mitral cell layer. Virus was cleared rapidly from the olfactory bulb between 5 and 11 days. Athymic nude mice failed to eliminate the virus, demonstrating a requirement for T lymphocytes. Immunosuppression of normal mice with cyclophosphamide also prevented clearance. Both CD4+ and CD8+ T-cell subsets were important, as depletion of either of these subsets delayed viral clearance. Gliosis and infiltrates of CD4+ and CD8+ cells were detected by immunohistochemical analysis at 6 days. The role of cytokines in clearance was investigated by using an RNase protection assay for interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6, tumor necrosis factor alpha (TNF-alpha), TNF-beta, and gamma interferon (IFN-gamma). In immunocompetent mice there was upregulation of RNA for IL-1 alpha, IL-1 beta, IL-6, TNF-alpha, and IFN-gamma at the time of clearance. Nude mice had comparable increases in these cytokine messages, with the exception of IFN-gamma. Induction of major histocompatibility complex class I (MHC-I) molecules on cells in infected brains was demonstrated by immunohistochemical analyses in normal and nude mice, suggesting that IFN-gamma may not be necessary for induction of MHC-I on neural cells in vivo.

Teratogenic effects of neonatal arenavirus infection on the developing rat cerebellum are abrogated by passive immunotherapy.

The effects of viral infection on the developing nervous system and the potential of passive immunotherapy to protect against infection were examined. When 4-day-old Lewis rats were injected intracerebrally with lymphocytic choriomeningitis virus (LCMV) the majority of stem cells within the external granular layer of the developing cerebellum became infected. The infection progressed to the molecular layer, internal granular layer, and the Purkinje cells. By 15 days postinfection the molecular and internal granular layers of LCMV-infected cerebella were noticeably thinner than those in the controls and the individual folia were smaller. Neurons remained infected for up to 40 days as determined by immunohistochemistry. However, in rats treated with rat monoclonal anti-LCMV antibodies the staining was limited to the cells of ependyma and choroid plexus and was not detectable by 15 days postinfection. Macroscopically the infection resulted in pronounced hypoplasia, with the cerebella of 21-day-old LCMV-infected rats weighing 52 +/- 10 mg compared with 159 +/- 30 mg for control rats. Antibody-treated rats exhibited normal cerebellar size and development. Neutralizing antibodies specific for the viral GP-1 glycoprotein were protective but nucleoprotein-specific antibodies were not. Furthermore, suckling rat pups born of and nursed by LCMV-immune mothers were spared from cerebellar disease following neonatal infection. These results suggest that passive immunotherapy of neonates can provide effective protection against teratogenic effects of neonatal viral infection on the developing CNS.