Effects of Mother’s Illness and Breastfeeding on Risk of Ebola Virus Disease in a Cohort of Very Young Children

Background

Young children who contract Ebola Virus Disease (EVD) have a high case fatality rate, but their sources of infection and the role of breastfeeding are unclear.

Methods/Principal Findings

Household members of EVD survivors from the Kerry Town Ebola Treatment Centre in Sierra Leone were interviewed four to 10 months after discharge to establish exposure levels for all members of the household, whether or not they became ill, and including those who died. We analysed a cohort of children under three years to examine associations between maternal illness, survival and breastfeeding, and the child’s outcome. Of 77 children aged zero to two years in the households we surveyed, 43% contracted EVD. 64 children and mothers could be linked: 25/40 (63%) of those whose mother had EVD developed EVD, compared to 2/24 (8%) whose mother did not have EVD, relative risk adjusted for age, sex and other exposures (aRR) 7·6, 95%CI 2·0–29·1. Among those with mothers with EVD, the risk of EVD in the child was higher if the mother died (aRR 1·5, 0·99–2·4), but there was no increased risk associated with breast-feeding (aRR 0·75, 0·46–1·2). Excluding those breastfed by infected mothers, half (11/22) of the children with direct contact with EVD cases with wet symptoms (diarrhoea, vomiting or haemorrhage) remained well.

Conclusion/Significance

This is the largest study of mother-child pairs with EVD to date, and the first attempt at assessing excess risk from breastfeeding. For young children the key exposure associated with contracting EVD was mother’s illness with EVD, with a higher risk if the mother died. Breast feeding did not confer any additional risk in this study but high risk from proximity to a sick mother supports WHO recommendations for separation. This study also found that many children did not become ill despite high exposures.     

Preliminary observations on the characteristics of the owned dog population in Roseau, Dominica

This article reports findings from interviews with 93 heads of households (38.6% of all households) who owned 148 dogs in Roseau, the capital of The Commonwealth of Dominica. Mixed dogs, of no definable cross, were most common, followed by Rottweiler crosses. The median age of the dogs was 3 years, and 9.4% of the population was over 7 years. Respondents showed a definite preference for keeping male dogs (60%), and most animals were kept for protection (65%). Almost 30% of the dogs were allowed to roam. With 8.5% of the dogs neutered and 7 puppies per litter being born, the owned population produces more dogs than are required to maintain its size and so can provide recruits to the “stray” dog population. Comparisons with studies elsewhere in the Caribbean region (Fielding & Plumridge, 2005; Ortega-Pacheco et al. (in press) suggest that environmental effects rather than the level of care offered are primarily responsible for controlling the dog population.     

Neuronal and mesodermal differentiation of P19 embryonal carcinoma cells is characterized by expression of specific marker genes and modulated by activin and fibroblast growth factors

We have used the P19 embryonal carcinoma (EC) aggregation system as a model for early mouse development to study induction and modulation of mesodermal and neuronal differentiation. By studying the expression of marker genes for differentiated cells in this model we have shown that there is a good correlation between the differentiation direction induced in P19 EC aggregates and the expression of these genes. Expression of the neuronal gene midkine is exclusively upregulated when P19 EC cells are induced to form neurons while expression of early mesodermal genes such as Brachyury T, evx-1 , goosecoid and nodal is elevated after induction to the mesodermal pathway. In the present study we have further shown that activin A blocks the different directions of differentiation of P19 EC cells induced by retinoic acid (RA) in a dose-dependent way. To understand the mechanism behind this inhibitory action of activin A the expression of several RA-responsive genes, including the three RA receptor genes (RARα, RARβ and RARγ) was determined. Since activin has no clear effect on the expression and activity of the RAR it is very likely that this factor acts downstream of these receptors. In addition to activin, fibroblast growth factors (FGF) were shown to modulate P19 EC cell differentiation. However, in contrast to activin, FGF exclusively blocks the mesodermal differentiation of P19 EC cells by either 10⁻⁹mol/L RA or a factor produced by visceral endoderm-like cells (END-2 factor). The FGF effect is dose-independent. These results suggest an important function for RA and the END-2 factor in the induction and for activin and FGF in the modulation of specific differentiation processes in murine development.     

Truncated Activin Type II Receptors Inhibit Activin Bioactivity by the Formation of Heteromeric Complexes with Activin Type I Receptors

Truncated activin type II receptors have been reported to inhibit activin receptor signaling inXenopusembryos, although the mechanism of action for this effect has not been fully understood. In the present study we demonstrate that in P19 embryonal carcinoma cells both the induction of the activin responsive 3TP-lux reporter construct and the inhibition of retinoic acid-induced neuronal differentiation by activin are blocked by expression of a truncated activin receptor. To reveal the mechanism of action of truncated activin receptors, the interaction between different activin receptors has been investigated upon coexpression in COS cells followed by cross-linking of¹²⁵I-activin A and subsequent immunoprecipitation. Complexes between a truncated activin type IIA receptor and activin type IA and type IB receptors can be formed, as demonstrated by coimmunoprecipitation of these type I receptors with the truncated activin type IIA receptor. Other type I receptors known as ALK-1 and ALK-6 also coimmunoprecipitate with the truncated type IIA receptor, whereas ALK-3 and ALK-5 do not. Furthermore, the activin type IIB₂receptor does not coimmunoprecipitate with the truncated type IIA receptor, but decreases activin binding to the truncated type IIA receptor. In double immunoprecipitation experiments with cell lysates from COS cells, in which full-length activin type IIA and type IIB₂receptors were cotransfected, no interaction between these receptors was found. In contrast, homomeric complexes of full-length activin type IIA receptors were detected. These results implicate that truncated activin receptors can interfere with activin signaling by interacting with activin type I receptors. Additionally, truncated activin type IIB₂receptors might also interfere with type IIA receptor signaling by decreasing activin binding to the type IIA receptor and therefore might be more potent in inhibiting activin signal transduction. Furthermore, our data indicate that truncated type IIA receptors can interact with other type I receptors and as such might inhibit signal transduction by type I receptors other than activin type IA and type IB receptors.     

Carbon monoxide contributes to hypotension-induced cerebrovascular vasodilation in piglets

The gaseous compound carbon monoxide (CO) has been identified as an important endogenous biological messenger in brain and is a major component in regulation of cerebrovascular circulation in newborns. CO is produced endogenously by catabolism of heme to CO, free iron, and biliverdin during enzymatic degradation of heme by heme oxygenase (HO). The present study was designed to test the hypothesis that endogenously produced CO contributes to hypotension-induced vasodilation of cerebral arterioles. Experiments used anesthetized piglets with implanted, closed cranial windows. Topical application of the HO substrate heme-l-lysinate caused dilation of pial arterioles that was blocked by a metal porphyrin inhibitor of HO, chromium mesoporphyrin (CrMP). In normotensive piglets (arterial pressure 64 +/- 4 mmHg), CrMP did not cause vasoconstriction of pial arterioles but rather a transient dilation. Hypotension (50% of basal blood pressure) increased cerebral CO production and dilated pial arterioles from 66 +/- 2 to 92 +/- 7 microm. In hypotensive piglets, topical CrMP or intravenous tin protoporphyrin decreased cerebral CO production and produced pial arteriolar constriction to normotensive diameters. In additional experiments, because prostacyclin and nitric oxide (NO) are also key dilators that can contribute to cerebrovascular dilation, we held their levels constant. NO/prostacyclin clamp was accomplished with continuous, simultaneous application of indomethacin, N(omega)-nitro-l-arginine, and minimal dilatory concentrations of iloprost and sodium nitroprusside. With constant NO and prostacyclin, the transient dilator and prolonged constrictor responses to CrMP of normotensive and hypotensive piglets, respectively, were the same as when NO and prostaglandins were not held constant. These data suggest that endogenously produced CO contributes to cerebrovascular dilation in response to reduced perfusion pressure.     

Nitric Oxide Inhibition Enhances Platelet Aggregation in Experimental Anti-Thy-1 Nephritis

In the present paper we studied the role of nitric oxide radicals (NO) on platelet aggregation, fibrinogen deposition, superoxide formation, peroxynitrite formation, hemodynamics, and leukocyte migration in the Thy-1 model of glomerulonephritis. To first study the baseline kinetics of these parameters, groups of anti-Thy-1-treated rats were sacrificed at 1 h, 4 h, 24 h, 3 days, 7 days, and 14 days and compared to controls. Urinary protein excretion was significantly elevated in Thy-1 nephritis at 3 and 7 days. Glomerular macrophages, PMNs, and superoxide anion-positive cells were significantly increased in Thy-1 nephritis. Nitrotyrosine immunoreactivity was absent during the entire study period. Glomerular platelet aggregation was significantly increased in anti-Thy-1 injected rats at 1 h, 4 h, 24 h, and 3 days. Glomerular fibrinogen deposition was significantly elevated at all time points. To elucidate the role of NO in this process, additional groups of anti-Thy-1-injected rats were treated with the NOS inhibitor l-NAME and studied at 24 h. Urinary protein excretion was significantly higher in l-NAME treated Thy-1 rats compared to nontreated Thy-1 rats. Plasma and urine nitrite/nitrate levels were significantly lower in l-NAME-treated Thy-1 rats compared to nontreated Thy-1 rats. Compared to nontreated Thy-1 rats, there were no differences in intraglomerular leukocyte accumulation after treatment with l-NAME. In contrast, we observed a marked increase in platelet aggregation following l-NAME treatment. From these data we conclude that the inflammatory infiltrate in Thy-1 nephritis develops independent of NO radical production, whereas NO radicals prevent the accumulation of platelet aggregates.     

Differentially regulated production of platelet-derived growth factor and of transforming growth factor beta by a human teratocarcinoma cell line

The human teratocarcinoma stem cell line Tera-2 clone 13 is induced by retinoic acid to differentiate in vitro into endodermal or neuroectodermal cell types. In the absence of externally added growth factors, Tera-2 clone 13 cells proliferated at the same rate as in the presence of serum growth factors. Analysis of serum-free medium conditioned by Tera-2 clone 13 cells showed the presence of a polypeptide immunologically and biochemically related to platelet-derived growth factor (PDGF). In addition transforming growth factor beta (TGF-beta), but no TGF-alpha production could be detected. Tera-2 clone 13 cells specifically expressed high levels of the A-chain mRNA, but not the B-chain mRNA of PDGF. During retinoic acid induced differentiation the level of A-chain mRNA became markedly reduced. In contrast the TGF-beta mRNA levels increased significantly upon differentiation. The implications of these findings are discussed in terms of regulation of growth and differentiation in early embryos as well as in (human) teratocarcinomas.     

Retinoic acid resistance of the variant embryonal carcinoma cell line RAC65 is caused by expression of a truncated RARα

P19 embryonal carcinoma (EC) cells differentiate when treated with retinoic acid (RA). The P19 EC-derived mutant cell line RAC65 is resistant to the differentiation-inducing activity of RA. We show that these cells express a truncated retinoic acid receptor alpha(mRAR alpha-RAC65), probably due to the integration of a transposon-like element in the RAR alpha gene. This receptor lacks 71 C-terminal amino acids and terminates in the ligand-binding domain. In CAT assays in RAC65 cells, mRAR alpha-RAC65 fails to trans-activate the RAR beta promoter, which contains a RA-response element. In wild-type P19 EC cells mRAR alpha-RAC65 functions as a dominant-negative repressor of RA-induced RAR beta activation. Gel retardation assays demonstrate that mRAR alpha-RAC65 is still able to bind to the RA-response element of the RAR beta promoter, indicating that competition with functional RARs for the same binding site leads to the observed dominant-negative effect. In addition, in two RAC65 clones in which wild-type hRAR alpha was stably transfected RA-sensitivity was restored and in one RAR beta expression could be induced by RA. Taken together, these data show that the primary cause of RA-resistance of RAC65 cells is the expression of a defective RAR alpha, which prevents the trans-activation of RA-responsive genes and results in a loss of the ability to differentiate.     

Effect of several herbicides on bacterial populations and activity and the persistence of these herbicides in soil

Summary Samples of a sandy loam soil were supplied with normal, 10-fold and 100-fold rates of ioxynil, dalapon, mecoprop, dichlorprop, MCPA + dichlorprop, picloram, and amitrole-T and incubated at 29°C at 65 per cent of the waterholding capacity. Treated soil samples were compared with untreated samples. Samples supplied with (NH₄)₂SO₄ and herbicides were used to investigate the effect of the herbicides on the rate of nitrification and the production of nitrite. In several cases higher numbers of bacteria were found for a longer or shorter period in soil treated with herbicides. There was some evidence that certain groups of bacteria had adapted to ioxynil in a soil sample supplied with the 100-fold rate of this chemical. After 2 or 4 weeks lower numbers ofAzotobacter chroococcum were found at the normal rate of ioxynil, dalapon, mecoprop, and dichlorprop. At the 100-fold rate of application the numbers of Azotobacter were unfavourably affected by all herbicides. The production of mineral nitrogen was hardly affected by the normal and 10-fold rates of application. In the first week the rate of nitrification was slightly depressed in soil samples treated with the normal rates of dichlorprop and amitrole-T and with the 10-fold rates of dalapon, mecoprop, and MCPA + dichlorprop. Strong inhibition of the nitrification for at least 7 weeks was shown by the 10-fold rate of amitrole-T. At the 100-fold rate all herbicides, with the exception of picloram, depressed the rate of nitrification for a longer or shorter period. During the second week a very small increase of nitrite was found in the samples treated with the normal and 10-fold rates of dalapon, mecoprop, dichlorprop, and amitrole-T. A small increase of nitrite was noted for 26 weeks in samples treated with the 100-fold rates of amitrole-T. A highly significant depression of CO₂ evolution was found in the first week in samples treated with the normal rates of ioxynil, dalapon, mecroprop, dichlorprop, and amitrole-T, also in samples treated with the 10-fold rates of dalapon, mecoprop, dichlorprop, MCPA + dichlorprop, picloram, and amitrole-T. A highly significant depression of CO₂ production was found after 8 weeks in all the samples treated with herbicides at the 100-fold rate with the exception of the sample treated with picloram. The decomposition of the herbicides was studied in soil samples treated with the 100-fold rates of herbicides. Only traces of dalapon and mecoprop were found after 9 months, but 7.2% ioxynil, 29.8% dichlorprop, 39% (MCPA + dichlorprop), 52.1% picloram and 52.2% amitrole-T were still present in active form.